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How to cite this thesis

Surname, Initial(s). (2012) Title of the thesis or dissertation. PhD. (Chemistry)/ M.Sc. (Physics)/ M.A. (Philosophy)/M.Com. (Finance) etc. [Unpublished]: University of Johannesburg. Retrieved from: https://ujdigispace.uj.ac.za (Accessed: Date).

WASTE TYRE MANAGEMENT TRENDS AND BATCH PYROLYSIS

FEASIBILITY STUDIES IN GAUTENG, SOUTH AFRICA

by

Nhlanhla P Nkosi

DISSERTATION

Submitted in fulfilment of the requirements of the degree

MASTER OF TECHNOLOGY

in

CHEMICAL ENGINEERING

in the

FACULTY OF ENGINEERING AND THE BUILT ENVIRONMENT

at the

UNIVERSITY OF JOHANNESBURG

SUPERVISORS: Prof. E Muzenda and Dr J.N. Zvimba

2014

ii

DECLARATION

I hereby declare that this dissertation, which I herewith submit in fulfilment of the

qualification

MASTER DEGREE IN CHEMICAL ENGINEERING

to the Department of Chemical Engineering, Faculty of Engineering and Built Environment

at the University of Johannesburg, is, apart from the recognised assistance from my

supervisors, my own work and has not previously been submitted by me to another institution

to obtain a diploma or degree.

_______________________________on this_________ day of June 2014

(Candidate)

_______________________________on this _________ day of June 2014

(Supervisor)

_______________________________on this _________ day of June 2014

(Co-Supervisor)

iii

ACKNOWLEDGEMENTS

The author would like to express her deepest appreciation to the supervisors Prof E.

Muzenda and Dr J.N. Zvimba for their dedication, encouragement and continuous

motivation. A greater part of this work would not have been possible without their support

and commitment.

I would like to thank the following sponsors for financial backing; National Research

Foundation (NRF), the Council of Scientific and Industrial Research (CSIR), UJ-Supervisor

linked and the UJ-Merit bursaries.

I would like to give thanks to the Chemical Engineering Technology Department for the

opportunity to conduct this work and for providing the required facilities, as well as the

University of Johannesburg‟s Postgraduate Centre for excellent administrative support.

I would also like to thank Mr J. Pilusa for giving insight about the research topic as well as

useful advice and guidance.

A special thanks to my waste to energy group members, J. Diphare and L. Ntaka for their

valued contribution and constant motivation.

My family and friends, my mother and Mrs S. Botha in particular, for financial and moral

support.

iv

RESEARCH OUTPUTS

Nhlanhla Nkosi, Edison Muzenda and John Zvimba “The Development of a Waste Tyre

Pyrolysis Production Plant Model in the Gauteng Region, South Africa” South African

Journal of Chemical Engineering, manuscript ID is SAJChE-2014-0019 (Submitted 11

August 2014).

Nhlanhla Nkosi and Edison Muzenda “A Review and Discussion of Waste Tyre Pyrolysis

and Derived Products” The International Conference of Manufacturing Engineering and

Engineering Management, London, United Kingdom July 2- 4, 2014, World Congress on

Engineering 2014, ISBN: 978-988-19252-7-5.

Nhlanhla Nkosi, Edison Muzenda and John Zvimba, “An Analysis of the Waste Tyre

Management Plans in South Africa” International Conference on Innovations in Engineering

and Technology, Bangkok, Thailand Dec 25-26, 2013, International Institute of Engineers

International Conference Proceedings, pp. 108-114 ISBN 978-93-82242-60-4.

Nhlanhla Nkosi, Edison Muzenda and John Zvimba “Using Tyre Derived Fuel: An Analysis

of the Benefits” International Conference on Emerging Trends in Engineering and

Technology, Phuket, Thailand Dec 7-8, 2013, International Institute of Engineers

International Conference Proceedings, pp 165-171. ISBN: 978-93-82242-52-9.

Nhlanhla Nkosi, Edison Muzenda and John Zvimba “The Current Waste Generation and

Management Trends in South Africa: A Review”, Chemical Technology, pp 6-12, October

2013.

Nhlanhla Nkosi, Edison Muzenda, John Zvimba and Jefrey Pilusa “The Current Waste

Generation and Management Trends in South Africa: A Review” International Conference on

Chemical, Industrial, Environmental, Mining and Metallurgy, Johannesburg, South Africa

April 15-16, 2013, In International Conference Proceedings of the Planetary Scientific

Research Centre, pp. 303 – 308, 2013, ISBN: 978-93-82242-26-0.

Nhlanhla Nkosi, Edison Muzenda, John Zvimba and Jefrey Pilusa “The Waste Tyre Problem

in South Africa: An Analysis of the REDISA Plan” International Conference on Chemical,

Industrial, Environmental, Mining and Metallurgy ,Johannesburg, South Africa April 15-16,

v

2013, International Conference Proceedings of the Planetary Scientific Research Centre, pp.

42 – 46, 2013, ISBN: 978-93-82242-26-0.

Nhlanhla Nkosi and Edison Muzenda “Waste Management Key Participants in Developing

Countries: A Discussion” International Conference on Chemical, Industrial, Environmental,

Mining and Metallurgy, Johannesburg, South Africa April 15-16, 2013, International

Conference Proceedings of the Planetary Scientific Research Centre, pp. 335 – 338, 2013,

ISBN: 978-93-82242-26-0.

Nhlanhla Nkosi and Edison Muzenda “Waste Management Participant: A South African

Perspective” International Conference on Chemical, Industrial, Environmental, Mining and

Metallurgy, Johannesburg, South Africa April 15-16, 2013, International Conference

Proceedings of the Planetary Scientific Research Centre, pp. 335 – 338, 2013, ISBN: 978-93-

82242-26-0.

NP Nkosi, P Mokoena,, E Muzenda, M Belaid "Organics –Biodiesel Systems Phase

Equilibrium Computation: Part 1" International Conference on Chemical, Biological, and

Environmental Sciences, Bangkok, Thailand, December 23 – 24, 2011, In International

Conference Proceedings of the Planetary Scientific Research Centre, pp. 371 – 375, 2011,

ISBN: 978-81-922428-3-5.

vi

ABSTRACT

Solid waste management is a growing environmental concern in developing countries such as

South Africa. Waste tyres fall under the general solid waste category give rise to land filling,

health and environmental challenges. As a result, majority of these waste tyres accumulate in

large quantities at landfill sites or end up being illegally disposed in open fields. Thus,

sustainable remedial technologies such as pyrolysis which are environmentally friendly must

be developed. Pyrolysis offers a number of attractive advantages as a treatment option such

as the production of primary and secondary economic valuable products, namely pyrolysis

gas, oil, char and steel wires.

The objective of this work was the development of a business model which includes costing,

procurement, installation, commissioning and operating a batch pyrolysis plant in Gauteng,

South Africa. In addition this work assesses the environmental, socio-economic aspects for

waste tyre derived products. The study objectives were achieved through literature research,

site visits, telephonic and personal interviews as well as questionnaires.

An order of magnitude costing method was used for the construction of the pyrolysis business

model. The model showed that it is possible to operate and sustain a batch pyrolysis plant

with a constant supply of waste tyres in the Gauteng region. This research has also shown

that a batch plant with a 12 year life span and a projected payback period of approximately 5

years can be operated. However, an initial capital incentive of R 10 173 075.00 is required

which includes the cost of all major equipment, plant assessment costs, building and

structure, engineering and construction and other costs such as contingency fees and office

utilities.

Four major income streams are expected to be core revenues for the business; the waste tyre

gate fee, tyre derived pyrolysis oil, carbon black and steel wire. Project evaluation methods

such as the Return on Investment (ROI), Return of Assets (ROA) and the Rate of Return

(ROR) were in strong agreement with those obtained from literature. In addition, the positive

net present value shows that the project is viable. However, a stable and well regulated

market should exist for the pyrolysis products.

vii

LIST OF TABLES

Table 2.1 Sources and types of general waste ........................................................................................................ 9

Table 2.2 Hazardous waste sub classes ................................................................................................................ 11

Table 2.3 Provincial waste contribution in South Africa, 2011 ............................................................................ 21

Table 2.4 REDISA tyre categories ....................................................................................................................... 24

Table 2.5 SATRP tyre categories ......................................................................................................................... 29

Table 2.6 Various applications for whole, cut, or shredded tyres ........................................................................ 30

Table 2.7 Various applications for crumbed rubber ............................................................................................. 31

Table 2.8 RMIO tyre categories ........................................................................................................................... 34

Table 2.9 2010 Global waste tyre treatment situation .......................................................................................... 39

Table 2.10 Benefit analysis of incineration .......................................................................................................... 46

Table 2.11 Waste to energy technologies ............................................................................................................. 50

Table 2.12 Composition of whole tyres ................................................................................................................ 56

Table 2.13 Comparison of incineration, gasification and pyrolysis ...................................................................... 57

Table 2.14 Pyrolysis gas constituents ................................................................................................................... 58

Table 2.15 Characteristics of vacuum pyrolysis waste tyre derived oil ................................................................ 62

Table 2.16 Elemental composition of oils obtained by vacuum pyrolysis of used tyres (wt. %) ........................ 63

Table 2.17 Waste tyre-derived pyrolytic oil impurities (ppb) .............................................................................. 63

Table 2.18 Surface area and elemental composition of pyrolytic carbon black and activated carbon black (wt%)

.............................................................................................................................................................................. 65

Table 2.19 Summary of waste tyre applications .................................................................................................. 67

Table 2.20 Ultimate analysis of pyrolysis gas ...................................................................................................... 67

Table 3.1 Questionnaire: Pyrolysis plant .............................................................................................................. 76

Table 3. 2 Questionnaire: Public/Community ...................................................................................................... 76

Table 3. 3 Questionnaire: Landfill sites ................................................................................................................ 77

Table 3.4 Questionnaire: Government/Local municipalities ............................................................................... 77

Table 4.1 Role of the informal sector in waste tyre management ......................................................................... 81

Table 4. 2 Main players in the South African waste sector ................................................................................. 85

Table 4.3 Mogale City waste disposal rates.......................................................................................................... 87

Table 4.4 Calorific values of a number of common fuels ..................................................................................... 92

Table 4.5 Pyrolysis oil specifications ................................................................................................................... 96

Table 4.6 Proximate analysis of crude and distilled pyrolysis .............................................................................. 97

Table 4.7 Pyrolysis carbon black specifications ................................................................................................... 98

viii

Table 5. 1 Effect of temperature on yield ........................................................................................................... 100

Table 5.2 Total plant energy requirement ........................................................................................................... 101

Table 5.3 Pyrolysis plant operational assumptions ............................................................................................. 102

Table 5.4 Process Input assumptions .................................................................................................................. 102

Table 5. 5 Mass and energy balance ................................................................................................................... 103

Table 5.6 Waste tyre pyrolysis project capex ..................................................................................................... 107

Table 5.7 Plant evaluation calculations .............................................................................................................. 108

Table 5.8 Business model option 1 ................................................................................................................... 1108

Table 5.8 Business model option 1 ..................................................................................................................... 108

ix

LIST OF FIGURES

Fig. 2.1 General and hazardous waste disposal [20] ............................................................................................ 12

Fig. 2.2 Provincial municipal waste contribution in South Africa, 2011 [7]. ...................................................... 13

Fig. 2.3 General waste composition, 2011 [7]. .................................................................................................... 13

Fig. 2.4 Recycling rates in South Africa, 2007 [27]. ........................................................................................... 15

Fig. 2.5 Recycling rates in South Africa, 2009 [27]. ........................................................................................... 16

Fig. 2.6 The waste cycle [29]. .............................................................................................................................. 18

Fig. 2.7 Waste Hierarchy, NWMS 1999 [31]. ..................................................................................................... 19

Fig. 2.8 Waste Hierarchy, NWMS 2010 [31]. ..................................................................................................... 19

Fig. 2.9 Waste Hierarchy, 2010 [31]. ................................................................................................................... 20

Fig. 2.10 Municipal general waste data in South Africa[7]. ................................................................................ 21

Fig. 2.11 REDISA waste tyre hierarchy [35] ....................................................................................................... 24

Fig. 2.12 The REDISA Waste Tyre Hierarchy [35]. ............................................................................................ 26

Fig. 2.13 REDISA initial cost allocations ............................................................................................................ 28

Fig. 2.14 SATRP waste tyre hierarchy [38] ......................................................................................................... 29

Fig. 2.15 SATRP Initial cost estimates ................................................................................................................ 33

Fig. 2.16 RMIO waste tyre hierarchy [40] ........................................................................................................... 34

Fig. 2.17 Technologies for managing scrap tyres[60] ......................................................................................... 44

Fig. 2.18 The scrap tyre incineration process[60] ................................................................................................ 46

Fig. 2.19 Scrap tyre gasification process[60]....................................................................................................... 48

Fig. 2.20 Primary energy supply in South Africa 1998-2009 [66] ...................................................................... 49

Fig. 2.21 Energy usage by sector 2006-2009 [66] ............................................................................................... 49

Fig. 2.22 Scrap tyre pyrolysis process[60] .......................................................................................................... 52

Fig. 2.23 Effect of feed size on product yield[8] ................................................................................................. 53

Fig. 2.24 Effect of temperature on product yield[8] ............................................................................................ 54

Fig. 2.25 Effect of residence time on product yield[8] ........................................................................................ 55

Fig. 2.26 Compositions of the gases obtained in tyre pyrolysis at different temperatures[68] ............................ 61

Fig. 2.27 Tyre pyrolysis conversion and products applications[72] .................................................................... 61

Fig. 2.28 Formation of polycyclic aromatic hydrocarbons in scrap tyre [2] ........................................................ 63

Fig. 2.29 Percentage distribution of energy types used in the transport sector in South Africa, 2010[85] .......... 70

Fig. 3.1 Project route map................................................................................................................................... 75

Fig 4.1 Waste streams in different communities [95] ........................................................................................... 79

Fig 5.1 Projected plant life, costs and revenues. ................................................................................................. 105

Fig 5.2 Net present value and depreciation rate .................................................................................................. 106

x

TABLE OF CONTENTS

DECLARATION ....................................................................................................................... ii

ACKNOWLEDGEMENTS ..................................................................................................... iii

RESEARCH OUTPUTS ........................................................................................................... iv

ABSTRACT .............................................................................................................................. vi

LIST OF TABLES ................................................................................................................... vii

LIST OF FIGURES .................................................................................................................. ix

TABLE OF CONTENTS ........................................................................................................... x

INTRODUCTION ..................................................................................................................... 1

1.1 Background and Motivation ........................................................................................ 2

1.2 Problem Statement ...................................................................................................... 2

1.3 Study Justification ....................................................................................................... 4

1.4 Aims and Objectives ................................................................................................... 4

1.5 Dissertation Layout ..................................................................................................... 5

LITERATURE REVIEW .......................................................................................................... 6

2.1 Introduction ...................................................................................................................... 7

2.2 Definition of Waste .......................................................................................................... 8

2.2.1 Waste classes ............................................................................................................. 8

2.2.2 Waste generation ..................................................................................................... 12

2.2.3 Waste management .................................................................................................. 14

2.3 The General Waste Hierarchy ........................................................................................ 18

2.3.1 Waste avoidance and reduction ............................................................................... 20

2.3.2 Recovery, re-use and recycling ............................................................................... 22

2.3.3 Treatment and disposal ............................................................................................ 22

2.3.4 Remediation ............................................................................................................. 22

2.4 The Proposed Integrated Waste Tyre Management Plans ............................................. 22

2.4.1 The REDISA plan .................................................................................................... 23

2.4.2 The SATRP plan ...................................................................................................... 29

2.4.3 Integrated Industry Waste Tyre Management Plan of The Retail Motor Industry

Organisation (IIWTMP-RMIO) ....................................................................................... 33

2.4.4 Analysis of the plans................................................................................................ 36

xi

2.5 Waste Tyre Disposal Alternatives .................................................................................. 37

2.5.1 Rubber ..................................................................................................................... 37

2.5.2 Material recovery ..................................................................................................... 40

2.5.3 De-vulcanization technologies ................................................................................ 41

2.5.4 Energy and material recovery .................................................................................. 44

2.5.5 Pyrolysis, Gasification and Liquefaction (PGL) Processes ..................................... 46

2.6 Product Markets ............................................................................................................. 69

2.6.1 Oil ............................................................................................................................ 69

2.6.2 Char .................................................................................................................... 71

2.6.3 Gas ........................................................................................................................... 71

2.6.4 Steel ......................................................................................................................... 72

2.7 Successes and Failures of Waste Tyre Pyrolysis ........................................................... 72

METHODOLOGY .................................................................................................................. 74

3.1 Project objectives: .......................................................................................................... 75

3.2 Research Methods .......................................................................................................... 75

3.2.1 Interviews ................................................................................................................ 75

3.2.2 Site visits.................................................................................................................. 76

3.2.3 Questionnaires ......................................................................................................... 76

3.2.4 Literature Analysis .................................................................................................. 77

3.2.5 Model Construction ................................................................................................. 77

GENERAL DISCUSSIONS .................................................................................................... 78

4.1 Role Played by Informal and Formal Sector in Waste Tyre Management .................... 79

4.1.1 Municipal Governments .......................................................................................... 79

4.1.2 The Informal Private Sector .................................................................................... 80

4.1.3 The Formal Private Sector ....................................................................................... 82

4.1.4 Community Based Organizations (CBOs) .............................................................. 83

4.1.5 Non-Governmental Organizations (NGOs) ............................................................. 83

4.1.6 Key issues and constrains ........................................................................................ 84

4.1.7 Informal and Formal Sector Integration .................................................................. 84

4.2 Socio-Economic Impact of Using Tyre Derived Products ............................................. 86

4.2.1 Land filling ban of waste tyres ................................................................................ 86

4.2.2 The environmental impact ....................................................................................... 88

4.2.3 Social impact ........................................................................................................... 88

xii

4.2.4 Economic impact ..................................................................................................... 89

4.2.5 Tyre Derived Fuel (TDF) applications .................................................................... 91

4.2.6 Waste tyre pyrolysis markets ................................................................................... 93

WASTE TYRE PLANT PYROLYSIS MODEL .................................................................... 99

5.1 Pyrolysis ....................................................................................................................... 100

5.1.1 Pyrolysis end products ........................................................................................... 100

5.1.2 Utilities .................................................................................................................. 101

5.2 Discussions ................................................................................................................... 101

5.3 Environmental Impact Assessment .............................................................................. 109

5.3.1 Air Emissions ........................................................................................................ 109

5.3.2 Liquid Residues ..................................................................................................... 110

5.3.3 Solid Waste Residues ............................................................................................ 111

5.4.1 Production .............................................................................................................. 111

5.4.2 End products .......................................................................................................... 111

5.4.3 Financial Requirements ......................................................................................... 112

CONCLUSION AND RECOMMENDATIONS .................................................................. 114

REFERENCES ...................................................................................................................... 116

APPENDICES ....................................................................................................................... 125

Appendix A ........................................................................................................................ 125

Appendix B ........................................................................................................................ 132

CHAPTER 1

INTRODUCTION

2

1.1 Background and Motivation

The use of automobile vehicles has become a daily essential for many households and

businesses globally[1, 2]. As a result, the disposal of waste vehicle tyres presents a major

environmental concern that requires immediate attention. Globally more than 330 million

tyres are discarded annually and accumulated over the years[2]. In 2003, Germany alone

generated 600,000 tons of waste tyres[3]. South Africa requires a plan to deal with its

growing „tyre mountain‟ problem, which is escalating at a rate of about 200 000 tons per

year, or one million waste tyres generated of which only 10% - 15 % is recycled[4]. Currently

2% of waste tyre processing takes place in three shredding plants in the country and a small

percentage is used as fuel[5]. A few other plants convert some waste tyres into mats,

playground equipment and protection pads[6]. Thus, there is a need to find alternative waste

tyre disposal methods. This has resulted in the release of the “Minimum Requirements for

Waste Disposal to Landfill”, “Waste Minimisation, Recycling and Treatment” by the

Department of Water Affairs in 1998. The South African Government has identified this

issue as a major area of environmental concern, resulting in the approval of an integrated

industry waste tyre management plan entitled the Recycling and Economic Development

Initiative of South Africa (REDISA) in accordance to the National Environmental

Management: Waste Act, 2008 (Act No. 59 of 2008) as stated in the Government Gazette, 17

April 2012, No.35147. This work focuses on socio-economic sustainable utilisation of waste

tyres. The objectives of this work is in line with the core environmental, social and economic

objectives for South Africa and the Gauteng Province in particular, namely: National Green

Economy Strategy (2010), Gauteng Economic Strategy, Gauteng Integrated Energy Strategy

(GIES, 2010), West Rand Green IQ (2011), Green strategy program for Gauteng (ECODEV,

2011) and most recently the REDISA Plan (2012).

1.2 Problem Statement

Scrap tyre present a major disposal problem in many developing and developed countries.

The same properties that make them desirable for use as automobile tyres in particular

durability also make them difficult to dispose of. Tyres are almost immune to biodegradation,

thus resulting in them being stockpiled in landfills or illegally dumped throughout the

country.

There is alarming increase of waste tyres being disposed in landfills in South Africa, which

were recorded to contribute 1% of the overall general waste composition during 2010 and

3

increasing [7]. Disposal site operators are no longer considering land filling as a viable

solution to harbour waste tyres, thus leading to the illegal dumping or burning of tyres. The

disposal of tyres is also becoming more expensive, while this trend is likely to continue as

landfill space becomes limited[8]. In this regard, the effect of such activities contribute

significantly to environmental challenges, both land and air. Noxious gases are produced

because of tyre burning for heat generation in rural areas; this activity is most common in low

income residential areas and informal settlements. Moreover, the use of worn out tyres sold at

cheaper rates cause severe road accidents due to un-roadworthiness and tyre failure. Tyres

take up large amounts of valuable space and also provide breeding sites for mosquitoes and

rodents[9], causing diseases that threaten human health. Fire hazards in large stockpiles could

consequently cause uncontrollable burning and air pollution where large amounts of thick

black smoke containing carcinogens are emitted into the atmosphere[10]. Such fires are

difficult to control because of the high flammability of tyres and the presence of air available

in the piles.

Over the years, alternative waste management options for tyre recycling such as re-treading,

reclaiming, grinding and crumbing have been implemented to produce rubber for other

applications such as carpets, sports surfaces and children‟s playgrounds[7]. However, all

these have significant drawbacks and limitations[9]. The South African Government is in the

process of implementing new laws and legislation to protect the environment and to consider

greener techniques for the treatment and disposal of waste tyres.

In this regard, alternative waste management options such as tyre pyrolysis are currently

receiving renewed attention[1, 3, 9]. Pyrolysis is the thermal degradation of waste matter in

the absence of oxygen. Pyrolysis has a number of attractive advantages as a treatment option.

Tyre pyrolytic oils have been found to have a high calorific value of approximately 41–44 MJ

kg, which would encourage their use as replacements for conventional liquid fuels[2]. In

addition, tyre derived oil can be used directly as fuel or blended to petroleum refinery feed

stocks. The derived gases are also useful as fuel and the char may be used as carbon black or

activated carbon[2]. Moreover, previous studies on the combustion of oil derived from batch

pyrolysis of waste tyres found the oil to have similar properties to diesel[3].

Due to non-compliance with environmental legislation and the unregulated product market,

several pyrolysis plants have been shut down in South Africa[11]. To date none of the

4

operating plants are addressing the national concerns relating to environmental and socio-

economic sustainability. The pyrolysis processes currently used to treat waste tyres do not

generate high quality primary products that are ecologically friendly and the market for these

products is not regulated and monitored. Secondary products such as high-grade carbon black

and activated carbon may also be obtained by integrating a further purification stage into the

pyrolysis process[2]. The current plant design and operations are not addressing issues

around sustainable job creation, energy and poverty reduction while protecting the

environment and public health. There is need for a detailed investigation for the most cost

effective and environmentally sustainable waste tyre pyrolysis plant that will produce high

quality products with minimal environmental impacts. There is also need to develop and

support the sustainable management of waste tyres for use in recycling and for energy

generation.

1.3 Study Justification

Waste tyres become a burden to deal with after they have reached their life span, thus a

majority of developed countries, such as European Union countries, have put a ban on the

land filling of waste tyres. Currently implemented strategies have proven to be limited and

unsuccessful due to the lack of integration between the private sector tyre manufacturers and

the public sector national waste management departments. Developing countries, such as

South Africa, are faced with an increasing mountain of waste tyres which can be utilised as a

source of fuel. The country is currently experiencing energy shortages and supply, thus

initiatives such as the conversion of waste tyres to energy and material recovery are desired.

1.4 Aims and Objectives

This work covers the feasibility of construction and operating a batch waste tyres pyrolysis

pilot plant in Gauteng. It also demonstrates the possibility of producing high quality fuel from

automotive waste tyres via a process of thermal decomposition. A preliminary study on

quantitative analysis and transport logistics of waste tyres was carried out to evaluate its fit

into the pyrolysis model. Other waste tyres processing technologies such as gasification are

explored and compared to pyrolysis. The study mainly focused on:

Environmental and economic impact of using waste tyre derived oil and carbon black

as alternative green fuels.

Market analysis of waste tyre pyrolysis products.

5

Development of business model including costing, procurement, installation,

commissioning and the operation of a pyrolysis plant.

Analysing the role played by informal and formal sector in waste tyre collection and

recycling.

Assessment of the socio-economic and market opportunities associated with energy

recovery from pyrolysis of waste tyres.

1.5 Dissertation Layout

Chapter 1 outlines the motivation of the study, as well as aims and objectives of the study.

Chapter 2 reviews literature and discusses the various waste tyre management strategies.

Chapter 3 outlines the approaches and procedures followed to achieve the study objectives.

Chapter 4 gives general discussions.

Chapter 5 presents pyrolysis plant design, construction and operation.

Chapter 6 Conclusions and recommendations are presented.

6

CHAPTER 2

LITERATURE REVIEW

7

2.1 Introduction

In generic terms, waste can be defined as “an unavoidable by-product of most human

activity”[12]. Economic development and rising living standards have increased the quantity

and complexity of generated waste. Moreover, industrial diversification and the provision of

expanded health-care facilities have added substantial quantities of industrial hazardous and

high risk health care waste into the waste stream with potentially severe environmental and

human health consequences. There are two fundamental waste classes, namely, general waste

(municipal waste) and hazardous waste (health care risk waste and certain industrial waste).

Waste tyres fall under the general waste category which gives rise to land filling, health and

environmental challenges.

Developing countries, including South Africa, are faced with major challenges concerning

waste tyre disposal, these include: (i) tyre stockpiles provide breeding ground for mosquitoes

and vermin, this in turn, causes serious diseases, thus affecting human health, (ii) fire hazards

in large stockpiles that could consequently cause uncontrollable burning and air pollution,

(iii) the current „„conservation of natural resource concept‟‟, namely the reuse (retread) first,

then reuse of rubber prior to disposal, does not accommodate the increased dumping of tyres,

(iv) due to the high cost of legal disposal for tyres, illegal dumping may increase, (v) disposal

of tyres is becoming more expensive and this trend is likely to continue as landfill space

becomes more scarce. Tyres, also classed as polymers, are non-biodegradable solid waste

because of their complex mixture of very different materials, which include several rubbers,

carbon black, steel cord and other organic and inorganic components. Land filling has been

one of the conventional methods used for waste tyre disposal, but it requires large quantities

of airspace as tyres cannot be compacted[6].

Alternatively, recycling of solid waste to a useful product can be a sustainable approach with

future prospects, particularly the pyrolysis process. Waste tyres can be thermally pyrolyzed to

produce oil, gas, and char. Despite the success of the process, there are still challenges or

drawbacks. Environmental protection is a significant factor that must be taken into account

when considering the pyrolysis process. The gases released during the process are not

environmentally friendly if released into the atmosphere. Thus, stringent atmospheric

protection standards must be adhered to in order to minimize the health and environmental

challenges pyrolytic gases pose. Lastly, the final products, either primary or secondary must

be uncontaminated and marketable and must prove to be viable and profitable.

8

2.2 Definition of Waste

According to the Government Gazette, 24 August 1990[13], waste is defined as an

undesirable or superfluous by-product, emission, residue or remainder of any process or

activity, any matter, gaseous, liquid or solid or any combination thereof, which

is discarded by any person,

is accumulated and stored by any person with the purpose of eventually discarding it

with or without prior treatment connected with the discarding thereof,

is stored by any person with the purpose of recycling, re-using or extracting a usable

product from such matter.

2.2.1 Waste classes

Waste classification systems are vastly documented in South Africa; these include waste

regulations and laws such as the minimum requirements for the handling, classification and

disposal of general and hazardous waste[14] as well as the waste classification and

management regulations, which is in accordance with the Waste Act (Act No. 59, 2008)[15].

Some of the laws that have been amended on this act include, Act No. 73 of 1989

(Environmental Conservation Act, 1989) whereby certain sections have been amended or

repealed as well as the repulsion of sections 8 and 9 of the environmental conservation

amendment Act, 1992 (Act No. 79 of 1992).

The waste classification system is based on the concept of risk[14]. It is accepted that there is

no waste that is truly "non-hazardous", since nothing is entirely safe or ideally non-

hazardous. No matter how remote the risk posed to man and the environment by a particular

waste, it nonetheless exists. However, it is possible to assess the severity of the risk, and to

make informed decisions on that basis. The classification system therefore distinguishes

between waste of extreme hazard, which requires the utmost precaution during disposal, and

waste of limited risk, requiring less attention during disposal. Thus waste is divided into two

main classes, namely general and hazardous waste, which are further sub classified into

smaller categories. General waste is sub classified into domestic, industrial and institutional

waste, while hazardous waste is further classified into explosives, flammable liquids and

solids as well as corrosives. The waste classification system is in accordance with the risk

waste poses; hence, general waste poses little risk to the environment while hazardous waste

poses significant risk. For waste to be properly managed, its properties and its risk potential

must be fully understood.

9

2.2.1.1 General Waste

General waste does not pose a significant threat to public health or the environment if

properly managed [14]. Examples would include domestic, commercial, certain industrial

wastes and builder's rubble. General waste may be disposed of at any duly authorized waste

disposal facility permitted in terms of the Environment Conservation Act (73 of 1989).

Domestic waste is classified as general waste even though it may contain hazardous

components. This is because the quantities and qualities of hazardous substances in domestic

waste are sufficiently minor to be a potential risk. In addition, the Minimum Requirements

for Waste Disposal by Landfill require leachate control at certain general waste disposal sites.

Table 2.1

Sources and types of general waste

Source Typical waste generator Types of solid wastes

Residential Single and multifamily dwellings Food wastes, paper, cardboard,

plastics, textiles, leather, yard wastes,

wood, glass, metals, ashes, special

wastes (e.g. bulky items, consumer

electronics, white goods, batteries,

oil, tyres) and household hazardous

wastes

Industrial Light and heavy manufacturing, Housekeeping wastes, packaging, food

fabrication, construction sites, wastes, construction and demolition

power and chemical plants materials, hazardous wastes, ashes and

special wastes

Commercial Stores, hotels, restaurants, markets, Paper, cardboard, plastics, wood, food

office buildings, etc. wastes, glass, metals, special wastes

hazardous wastes and tyres

Institutional Schools, hospitals, prisons, government Same as commercial

centres

Construction and demolition New construction sites, road repair, Wood, steel, concrete, dirt, etc.

renovation sites, demolition of buildings

2.2.1.2 Hazardous Waste

Hazardous waste is defined as waste that has the potential, even in low concentrations, to

have a significant adverse effect on public health and the environment because of its inherent

toxicological, chemical and physical characteristics[14]. Hazardous waste requires stringent

10

control and management, to prevent harm or damage and hence liabilities. It may only be

disposed of on hazardous waste landfills (Section 3, Minimum Requirements for Waste

Disposal by Landfill)[14]. Hazardous waste can further be classified by its hazardous rating

which simply differentiates between a hazardous waste that is moderately hazardous and one

that is extremely hazardous. The 9 sub classes of hazardous waste as listed in Table 2.2 are

classified and treated under the South African Bureau of Standards (SABS) Code 0228,

namely, the identification and classification of dangerous goods and substances. Applying the

precautionary principle, waste must always be regarded as hazardous where there is any

doubt about the potential danger of the waste stream to human beings or the environment.

Waste management in South Africa is regulated by legislation such as the National

Environmental Management Act, 1998 (Act 107 of 1998), Environment Conservation Act

(Act 73 of 1989) Section 20, National Water Act (Act 36 of 1998), Health Act (Act 63 of

1977), Air Quality Act (Act 39 of 2004), Hazardous Substances Act (Act 15 of 1973),

Nuclear Energy Act (Act 131 of 1993) Section 45 & 46 Authority, Medicines and Related

Substances Act, 1965 (Act 101 of 1965) Section 27, and the Occupational Health and Safety

Act (Act 85 of 1993).

The definition and regulation of waste has been redefined and amended over the past years in

South Africa. However, the Environmental Conservation Act (ECA) was the first piece of

legislation formally regulating waste management in South Africa. The ECA came into

operation on the 9th

of June 1989 and underwent many amendments, and it was later repealed

in its entirety, save for a few provisions by National Environmental Management Waste Act

(NEMWA)[16]. The significant changes that were made in the ECA which are now catered

for by the NEMWA, 1998 (Act No. 107 of 1998) where the redefining and addition of

important terms, the provision for temporary waste storage and other waste related aspects

that came into effect after 1997 are included. Many large industries in South Africa dispose

of industrial waste on-site, but since this hazardous waste does not enter the formal waste

stream, there is also often little reported data available[17].

11

Table 2.2

Hazardous waste sub classes

Class No. Class type

Class 1 Explosives

Class 2 Gases

Class 3 Flammable liquids

Class 4 Flammable solids

Class 5 Oxidising substances and organic peroxides

Class 6 Toxic and infectious substances

Class 7 Radioactive substances

Class 8 Corrosives

Class 9 Other miscellaneous substances.

This regulatory system includes:

The issuing of waste disposal site permits.

A manifest system for the transportation of hazardous waste.

The registration of hazardous waste generators and transporters.

The aim is to protect the environment (Environment is used in the holistic sense and includes

cultural, social, soil, biotic, atmospheric, surface and ground water aspect) and the public

from the harmful effects of unsafe waste disposal practices. Before a waste disposal site

permit is issued, minimum procedures, actions and information is required from the permit

applicant. These are termed "Minimum Requirements". The minimum requirements provide

the applicable waste management standards or specifications that must be met in the absence

of any valid motivation to the contrary. They also provide a point of departure against which

environmentally acceptable waste disposal practices can be distinguished from

environmentally unacceptable waste disposal practices.

The objectives of setting minimum requirements are to[14]:

Prevent water pollution and ensure sustained fitness for use of South Africa's water

resources.

Attain and maintain minimum waste management standards in South Africa, so as to

protect human health and the environment from possible harmful effects caused by

the handling, treatment, storage and disposal of waste.

12

Effectively administer and provide a systematic and nationally uniform approach to

the waste disposal process.

Endeavour to make South African waste management practices internationally

acceptable.

2.2.2 Waste generation

Over 42 million cubic metres of general waste is generated every year in South Africa, with

Gauteng Province contributing 42%[18]. In addition, more than 5 million cubic metres of

hazardous waste is produced yearly, mostly in Mpumalanga and KwaZulu-Natal. This is a

result of the concentration of mining activities and fertilizer production in the two provinces.

The average amount of waste generated per person per day in South Africa is 0.9 kg[7]. This

is closer to the average waste produced in developed countries (0.73 kg in the UK and 0.87

kg in Singapore), compared to the average in developing countries such as 0.3 kg in

Nepal[18]. By far the biggest contributor to the solid waste stream is mining waste (72.3%),

followed by pulverized fuel ash (6.7%), agricultural waste (6.1%), urban waste (4.5%) and

sewage sludge (3.6%) [19].

Fig. 2.1 General and hazardous waste disposal [20]

South Africa has been implementing the “end on pipe” approach in the management of solid

waste, including waste tyres. Disposal at landfills has been the most predominantly utilized

method; hence the main focus was on acquiring land space for landfilling. According to the

South African Waste Information Centre (SAWIC) data bank which was established in 2004,

waste disposal has been increasing since then due to the betterment of the living standards for

most South Africans, thus resulting in an increased number of disposal sites. Domestic

0,00E+00

2,00E+06

4,00E+06

6,00E+06

8,00E+06

1,00E+07

1,20E+07

2004 2005 2006 2007 2008 2009 2010 2011 2012

To

nn

es

Total General Hazardous

13

environmental laws of most countries, including South Africa, have been profoundly

influenced by international laws. Most environmental problems transcend political

boundaries and global trends as well as pressures have driven the development of national

laws. In South Africa, environmental assessment was practised on a voluntary basis since the

early 1980s, but become part of legislation because of the incorporation of an environmental

right in the Bill of Rights[21]. As a result countries such as South Africa adopted new waste

reduction management strategies and systems. Fig. 2.1 shows annual waste generation from

2004 to 2012 obtained from the SAWIC databank.

Fig. 2.2 Provincial municipal waste contribution in South Africa, 2011 [7].

Fig. 2.3 General waste composition, 2011 [7].

.

0%

10%

20%

30%

40%

50%

Wa

ste

gen

era

ted

as

%o

f to

tal

wa

ste

Province

Non-

recyclables

municipal waste; 34%

Contruction and

demolition

waste; 21%

Metal waste;

14%

Organic waste;

13%

Paper; 7%

Plastic;

6%

Glass; 4% Tyres; 1%

14

Fig. 2.2 shows the provincial waste contribution in 2011 and the general waste composition is

shown in Fig 2.3. Gauteng, the economic hub of South Africa with a population of 11.3 x 106

in 2011[22] contributes 42% to the waste stream. Fiehn & Ball (2005)[23] suggested a

current growth rate envelope of between 2-3% per annum from a starting tonnage of ±15m

t/a, while DEAT (2012) suggested a generation rate of 1.57%[17].

Waste tyres made up 1% of landfilled general waste in 2011[17], Fig 2.3. The disposal of

waste tyres at landfill sites is environmentally unfavourable compared relatively to their size

as well their health and environmental implications, accompanied by low recycling and

alternative treatment rates in South Africa. As a result they are often illegally dumped or

burnt to recover steel for recycling. In 2009, regulations were promulgated requiring tyre

producers and importers to develop an integrated industry waste plan for waste tyre

management and funding.

2.2.3 Waste management

This section centers on the current waste management practices in urban communities. Plans

such as the integrated waste management plan and the national waste management strategy

exist for the economical and safe management of waste produced by urban communities. If

left uncontrolled, not only will there be an aesthetic problem, but also pose health risks. This

can be aggravated by the presence of hazardous material in the waste stream. Thus waste

must be collected from all sources as efficiently as possible, and disposed of in controlled

disposal facilities[24]. Various options are available for the treatment of either whole general

waste or of materials separated from it for recovery/recycling or pre-treatment prior to

disposal. After waste prevention and re-use, the waste management hierarchy accords the

highest preference to recycling over energy recovery and other disposal options.

2.2.3.1 Mobilisation

A common feature among the waste management options is the need for collection, sorting,

processing and transportation from source to the waste treatment or disposal facilities and

markets for recovered materials. A formal waste collection system was first established

around 1786 though the utilization of animal-drawn carts until the use of mechanical

transportation took over in the1920‟s. This transition brought about significant cost savings

as well as the advantage of easier supervision[25]. Waste collection and transportation has

had to be critically thought out in South Africa to accommodate rapid urbanization,

population growth, improvements in community health demands as well as better service.

15

The best approach for South Africa is to be able to integrate existing and new technological

systems to maximize economic advantage[25]. The same approach is also required for waste

tyre management, a reliable and well managed collection and transportation system. For

simplicity and easy management, a single national plan is the preferred approach.

2.2.3.2 Recycling

Rapid economic growth in South Africa‟s developed commercial and industrial areas,

particularly in the larger cities, reflects an increasing demand on the individual‟s life style

and leisure preferences. These demands have changed consumption needs resulting in

increased discarded goods and packaging material. Recycling diverts components of the

waste stream for reuse. The success of recycling is largely dependent on the market

availability for both the raw and re-manufactured products. Economically, recycled products

should be priced at a rate that covers the cost of their recovery less any subsidies. The price

commanded by recycled materials is highly dependent on their quality. Clean, well-sorted

and contaminant-free secondary material attracts a higher price than mixed, low quality or

sordid material. Low quality recycled products have no market and must be disposed of at a

cost[26]. Figs. 2.4 and 2.5 show the recycling rates for common general waste in 2007 and

2009 respectively. Generally, there is an increase in recyclable material from 2007 to 2009,

with the exception of beverage cans. This can be attributed to environmental awareness and

recycling initiatives by both private and public sectors. On the contrary, the recycling of

beverage cans dropped slightly during that period, and this might have been attributed to the

recession that was experienced in South Africa during the first quarter of 2009. This resulted

in big cooperate companies not being able to properly fund and sustain their environmental

initiatives and projects.

Fig. 2.4 Recycling rates in South Africa, 2007 [27].

70%

54,50%

25%

22% Metal beverages cans

Paper

Glass

Plastic

16

Fig. 2.5 Recycling rates in South Africa, 2009 [27].

Numerous waste tyre processing plants are in operation across South Africa. The plants

which are currently in operation are involved in the shredding, granulation and pulverising of

waste tyres which found use in various applications. South Africa requires technologies

which can process waste tyres with job creation potential with also the ability to reduce the

health and environmental risks. Some of the waste tyre companies and initiatives in South

Africa are: (a) The East Rand-based Vredestein SA Recycling Company found in the 1950s

and was burnt down in 2008. The facility produced rubber-chip products sold to a leading

international manufacturer of artificial grass systems for pitches and sports fields. Waste steel

and nylon flock were also reclaimed and sold to other recyclers[28]. (b) Innovative Recycling

converted waste rubber and plastic to fuel. The products were steel wire, oil and carbon black

and these were sold to scrap metal traders, transport companies and the ink and paint

industry. The plant closed down due to its failure to meet environmental standards. (c) South

African (SA) Tyre Recyclers, formed in late 2005 in Atlantis, Cape Town, to steer South

Africa's newest and most advanced technology in tyre recycling. The company works closely

with local authorities and government in waste tyre recycling and other waste tyre

environmental related matters. Scrap tyres are processed into a range of rubber granules and

fine powders. Rubber products produced are shreds (used in matting, sport surfaces, turf and

playgrounds); granules and chips (used in athletic tracks, playgrounds, horse arenas and

asphalt); crumbs and powders (used in new tyres, brake pads, road sealing, adhesives and

paints); and large shred tyre chips (used in civil engineering and fuel derivatives).

69%

56%

32%

26% Metal beverage cans

Paper

Glass

Plastic

17

2.2.3.3 Land filling

Land filling involves the managed disposal of waste on engineered sites with little or no pre-

treatment. Thus, landfilling is different from dumping which is characterized by the absence

of design, construction, control of the disposal operations and management of dump sites.

Land filling is the most common, cheapest and cost-effective method of disposing

waste[29].Waste dumping still occurs in less-developed communities in South Africa but this

is gradually declining[26]. The volume and content of the waste to be disposed of will dictate

the size and classification of the landfill, and necessary requirements for licensing purposes.

Some of the major problems associated with landfilling include (i) wind dispersing debris (ii)

rodent, insect and bird infestation (sometimes disease-carrying) (iii) pollution of ground and

surface water (iv) spontaneous combustion hazard, and (v) foul odours. Nation-wide, there

are over 2 000 waste handling facilities, of which 530 are permitted, yet only four of the nine

provinces have hazardous waste facilities[30]. There is an undersupply of landfill airspace,

and the currently available airspace is being rapidly depleted. This is propelled by the low

levels of waste minimization and reuse, recovery and recycling[30].Landfill sites are not

allowed to accept waste tyres into their sites in line with the proposed REDISA plan.

2.2.3.4 Incineration

The demand for land and the need to protect the limited groundwater resources in South

Africa dictates that alternative solutions to landfilling need to be explored. Incineration as an

alternative has been considered as a waste management strategy with the potential to

minimize waste volumes. The purpose of thermal treatment of waste (which in the narrow

sense usually means combustion in incinerators) is to reduce waste bulkiness before disposal

as inert inorganic ash residue. Modern incinerators are designed to recover the energy from

waste combustion supplementing electricity and/or heat from other sources[26]. In this

regard, waste tyres can also be utilised in the same manner. Large-scale incineration, such as

waste tyre incineration, is capital-intensive, but has the advantage of; (i) reducing the volume

of waste requiring landfilling (ii) combating the spread of disease (iii) providing a potential

energy source.

2.2.3.5 Pyrolysis and gasification

Along with the combustion technology outlined in section 2.2.3.4, there is increasing interest

in the advanced thermal conversion technologies of pyrolysis and gasification. These

technologies differ from combustion in that the waste is first heated either in the absence of

air or with a very restricted quantity of air. Organic matter is thermally broken down to give a

18

mixture of gaseous and/or liquid products that are then used as secondary fuels. The

secondary fuels are used to provide heat input for the process, thus promoting process self-

sustainability. The pyrolysis processes also produce solid coke residues which may be used as

a coal substitute. Fig. 2.6 shows the schematic waste cycle. Pyrolysis and gasification are

possible waste tyre remedial methods, and can yield the same products but at varying ratios.

Fig. 2.6 The waste cycle [29].

2.3 The General Waste Hierarchy

The conceptual approach to waste management is underpinned in the waste hierarchy, which

was introduced into South African waste management policy through the White Paper on

Integrated Pollution and Waste Management[17]. It was a hallmark of the 1999 National

Waste Management Strategy (NWMS)[14], as represented in Fig. 2.7, with Fig. 2.8

representing the amended 2011 waste hierarchy. The essence of the approach is to group

waste management measures across the entire value chain in a series of steps, which are

applied in order of priority. The foundation of the hierarchy, and the first choice of the

measures in the management of waste, is waste avoidance and reduction. Where waste cannot

be avoided, it should be recovered, reused, recycled and treated. Waste should only be

disposed of as a last resort.

19

Fig. 2.7 Waste Hierarchy, NWMS 1999 [31].

Fig. 2.8 Waste Hierarchy, NWMS 2010 [31].

The Waste Act provides the legal mandate for the successful implementation of the waste

hierarchy, through the provision of additional measures for the remediation of contaminated

land to protect human health and secure the wellbeing of the environment. Implementation of

the waste hierarchy promotes extended producer responsibility with respect to the design,

composition or production of a product and packaging. These requirements include clean

product measures, the composition and volume of packaging to be restricted as well as the

responsibility of the producer to ensure that packaging be designed in such a way that it can

be reduced, re-used, recycled or recovered[15], thus giving effect to the concept of „cradle-to-

cradle‟ waste management. This is an important advance from the previous “cradle to grave”

approach, which mainly took into account producer responsibility for the entire lifecycle of a

product until its final disposal. Cradle to cradle management ensures that once a product

reaches the end of its life span, its component parts are recovered, reused or recycled, thereby

Disposal

Treatment

Recovery, Re-Use and Recycle

Waste avoidance and Reduction

Waste avoidance and Reduction

Re-Use

Recycle

Recovery

Treatment and Dosposal

20

becoming inputs for new products and materials and this cycle repeats itself until the least

possible portion of the original product is eventually disposed as shown in Fig. 2.9.

Fig. 2.9 Waste Hierarchy, 2010 [31].

2.3.1 Waste avoidance and reduction

Waste avoidance and reduction is the foundation of the waste hierarchy and is the most

preferred waste management option. The aim of waste avoidance and reduction is to achieve

waste minimization and thus reducing the amount of waste entering the waste stream. This is

particularly relevant for waste streams where recycling, recovery, treatment or disposal of the

waste is problematic. While waste minimization is difficult to quantify, available figures

indicate that waste generation across all provinces has been on the rise per kilogram per year,

as supported by the 2011 figures and prior, Fig. 2.10 and Table 2.3[16]. Waste minimisation

occurs largely as a result of competitive pressures, economic incentives, and through

producer responsibility initiatives implemented by industries. To date the most notable of the

national government initiatives with respect to waste minimization has been the plastic bag

levy initiative. The agreement came into effect on the 9th

of May 2003, accompanied by a

standardization of the following bag sizes 8-litres, 12-litres and 24-litres, with the 24-litres

dominating retail markets[30]. Knowler[32] reported that plastic bag consumption

significantly dropped from 90% to 70%, when the fee was first introduced at a rate of 46 cent

per bag in 2003. However, due to pressure from plastic bag manufacturing industries the rate

has decreased by 44% in 2005[33]. A survey carried out by one of the major retail

supermarkets reported that, due to the lower price of plastic bags, majority of people tend to

Remediation

Disposal

Treatment and processing

Recovery, Re-Use and Recycle

Waste avoidance and Reduction

21

not reuse the plastic bags for shopping purposes as was intended by the acts. Consumers

might also perceive the carrying of plastic bags for shopping as an inconvenience, leading to

the absorption of the price of plastic bags into consumer‟s grocery list because of their low

price. Nevertheless, the plastic bag levy has slightly decreased the consumption of plastic

bags in South Africa. This is a tax instrument being used to effect change in behavior at both

consumer and industry level. Furthermore, there is also a proposed levy for the management

of end of life tyres entering the waste stream.

Table 2.3

Provincial waste contribution in South Africa, 2011

Province Kg/capital/Annum Waste generated as % of total waste Waste tyre generation (tonnes)

Western Cape 675 20 47428,60

Eastern Cape 113 4 9485,72

Northern Cape 547 3 7114,29

Free State 199 3 7114,29

KwaZulu Natal 158 9 21342,87

North West 68 1 2371,73

Gauteng 761 45 106714,35

Mpumalanga 518 10 23714,30

Limpopo 103 3 7114,29

237143,00

Fig. 2.10 Municipal general waste data in South Africa[7].

22

2.3.2 Recovery, re-use and recycling

Recovery, re-use and recycling are the second step in the waste hierarchy. These are very

different physical processes, but have the same aim of reclaiming material from the waste

stream and reducing the volume of waste generated that moves up the waste hierarchy.

Recycling rates in South Africa are relatively well established, Figs 2.4 and 2.5. These are

primarily driven by industry-led, voluntary initiatives with funds managed independently of

government via non-profit organizations, which oversee the recovery or recycling processes

and facilities.

2.3.3 Treatment and disposal

Section 2 (a) (iv) of the Waste Act clearly indicates that the treatment and disposal of waste is

a “last resort” within the hierarchy of waste management measures. In terms of waste

treatment and processing, the Department of Environmental Affairs (DEA) supports the

development of alternatives to land filling such as incineration, gasification, and

pyrolysis[27] of general waste and waste tyres. While there are cost implications for the

adaptation of the incineration process as a waste processing technology, the option requires

attention considering the rising costs of landfilling. It is anticipated that appropriate

incineration, gasification and pyrolysis facilities as well as other alternative technologies will

increase over time and ultimately replacing landfills as the primary waste disposal

mechanism[27].

2.3.4 Remediation

Remediation is the final step in the waste hierarchy. There is a lack of data on the number and

extent of contaminated sites (which include un- managed waste dumps) in South Africa due

to the various mining activities in the country plus the historical under-regulation of such

areas.

2.4 The Proposed Integrated Waste Tyre Management Plans

South Africa is considered as one of the fastest growing economies and the economic growth

is realised through the bulk industrial production of goods to meet the socio-economic needs

of a growing population. Over 200 000 tonnes of tyres become waste tyres in South Africa

annually. About 11 million used tyres are dumped illegally or burnt to retrieve steel wire.

With this figure estimated to increase by around 9.5 % annually, clearly the country is facing

a serious waste tyre problem[34].

23

The Department of Environmental affairs is tasked with protecting the environment and

public health. The Waste Management Act[15] declares its objectives as being to protect

human health and well-being as well as the environment. This Act, in Section 28(1),

addresses waste management options for waste that occurs in more than one province. The

Act anticipate the need to address national issues with a holistic national plan, hence the plans

had to be drafted taking cognisance of this. The Department promulgated Waste Tyre

regulations that took effect on the 30th

of June 2009, compelling tyre producers to register

with the Minister of Water and Environmental Affairs, but only three plans passed the initial

screening stages, namely: The South African Tyre Recycling Programme (SATRP) which

initially submitted its first draft in June 2009, The Retail Motor Industry Association

(RMIA), 21 December 2011 and The Recycling and Economic Development Initiative of

South Africa (REDISA plan), 19 April 2010. The REDISA plan was later approved and

gazetted for implementation on the 30th

of November 2012.

2.4.1 The REDISA plan

The REDISA plan has been accepted in accordance with the National Environmental

Management Waste Act, 2008 (Act No. 59 of 2008) as stated in the Government Gazette, 17

April 2012, No.35147. REDISA, registered as REDISA NPC (2010/022733/08) is a non-

profit making organization representing various people and organizations in the tyre and

waste tyre industry.

All tyre assortments that are imported or manufactured, including locally retreaded tyres, will

reach the end of their useful life and become waste tyres need to be managed. According to

REDISA, the annual projection of the quantities and types of tyres that are manufactured or

imported will be managed through the Integrated Industry Waste Management Plan. For the

ease of waste tyre management, tyres will be divided into nine categories as listed in Table

2.4.

24

Table 2.4

REDISA tyre categories

Table Category Type of tyre

1 Passenger tyres

2 Light commercial tyres

3 Heavy commercial tyres

4 Agricultural tyres

5 Motorcycle tyres

6 Industrial tyres

7 Aircraft tyres

8 Earth moving tyres

9 Any other pneumatic tyres

2.4.1.1 Waste tyre hierarchy

Similar to the general waste hierarchy[27], waste reduction and avoidance form the

foundation of the REDISA waste tyre hierarchy. It is followed by recycling, re-use and

recovery as the last option, Fig. 2.11.

Waste Tyre Avoidance and Reduction: Priority will as required in terms of regulation 7 (1) of

the Waste Tyre Regulations of 2009 to be directed to re-treading plants[35].

Re-use: Retreading of high performance tyres is a common practice in Europe[35], but rarely

practised in South Africa, due to the lack of funding associated with the establishment of

suitable plants and also because of consumer and dealer preconceived ideas.

Fig. 2.11 REDISA waste tyre hierarchy [35]

Recycling: Many recycling processes require significant capital investment, which in turn

necessitates assured long-term supply of the raw material to enable them to recoup the

investment. As a result, one of the most vital roles of the REDISA Plan is to manage the flow

and supply of tyres to recycling operations to ensure sustainability of those facilities.

The plan will promote and support the establishment of recycling facilities nationwide. These

facilities create employment opportunities for the informal sector and previously

25

disadvantaged individuals in both urban and rural communities. The collection of waste tyres

to the depots and/or tyre processors will be the main source of job creation and the

establishment of small businesses[36].

Applications to produce industrial and consumer products include sport surfaces, indoor

safety flooring, playground surfaces, shipping container liners, conveyor belts, automobile

mats, footwear, carpet underlay, roof tiles, flooring and activated carbon[37].

26

Fig. 2.12 The REDISA Waste Tyre Hierarchy [35].

27

2.4.1.2 The Plan in a nutshell

The basis of the REDISA Plan centres on the following fundamental aspects:

Job creation: Attaching a value per kilogram to waste tyres provides small entrepreneurs and

the previously disadvantaged with opportunities to earn income by delivering tyres to 150

depots throughout South Africa. REDISA aims to specifically identify micro operators,

provide the relevant training and create business opportunities by awarding specific

collection points, thereby ensuring sustainability.

Small Medium-Micro Enterprises (SMMEs) and Broad-Based Black Economic Empowerment

(BBBEE): One of the biggest hurdles faced by SMMEs is access to capital. Establishment of

depots requires funding that the SMMEs do not generally have access to. Under the REDISA

plan which addresses the entire industry, depots will initially be funded by REDISA and

leased to BBBEE entrepreneurs. This has the secondary advantage that should a depot fail

through mismanagement it becomes easier to re-start operation with new management.

Managers of these depots can over time, as they themselves become fully self-sustaining,

take over full ownership of their depots.

Need for informal participation: Tyre manufacturers and importers must shoulder the

primary responsibility for waste management. In practice, it is the tyre dealers who handle

waste tyres through their life cycle, hence the management approach must fit in with the

practicalities of the retail industry through the integration of both entities. The informal sector

deals with a large proportion of the waste tyre, estimated to be at least 75%[35]. Thus,

without informal sector participation no plan will succeed, hence the plan must be inclusive

of this sector.

Fairness: A single plan approach, with a simple and equitable system for apportioning the

waste tyre management fee will simplify administration and auditing. As a result, the plan

will be far less open to behind the scenes manipulation by the influential participants.

Finance and audit control: The management of waste tyres on a national scale is a massive

task involving very large sums of money, thus proper financial management is essential.

There are approximately 2300 tyre dealerships nationally[35], and hence the scale of

potential problems is huge, as would be the remedial cost.

28

Training and communication: The REDISA Plan will provide various training programmes

in order to equip all stakeholders with the relevant skills and competencies. Similarly, there

will be a need to market the concept of waste tyre recycling and encouraging participation. A

single plan with consolidated funding is not only more effective, but the message is simpler

and can easily be communicated.

Resilience and longevity: There are many other sources of environmental waste which can be

dealt with in the same manner, such as electric goods, small appliance batteries, compact

fluorescent lights and many other forms of waste. This can contribute towards a fund to cater

for safe recycling and disposal of these goods[35].

Fig. 2.13 REDISA initial cost allocations

The waste tyre management fee levied by REDISA on the subscribers will be calculated to

recover the cost of the waste tyre management process. The fee will be levied on both

produced and imported tyres. The Plan will raise funds from the levied fee of R2.30 per

kilogram (kg) and the fee will be reviewed annually to meet demands. The cost is calculated

taking into account the initial cost allocations, Fig. 2.13. From a research point of view, for

R2.30/ Kg

Transportation 38%=

88c/Kg Depots 19.5%=

43c/Kg

Admin

20%= 46c/Kg

Recyclers/ce-ment kilns

13.5%=

31c/Kg

Research & Development 2.5%=6c/Kg

Training 1%=3c/Kg

Marketing 2%=5c/Kg

Social upliftment

3.5%=

8c/Kg

29

the early implementation stages of the Plan, the 2.5% allocated should be sufficient. As the

plan develops and grows, unconventional primary and secondary products will be discovered

through research and development initiatives in the long run.

2.4.2 The SATRP plan

In response to the Waste Tyre Regulations, 2009, the South African Tyre Recycling Plan

(SATRP) Company (Company registration no: 2002/027503/08) prepared its Integrated

Industry Waste Tyre Management Plan, the “SATRP Company Industry Plan”. The plan was

aimed at solving the waste tyre problem in South Africa, creation of jobs for previously

disadvantaged individuals (PDIs) and the establishment of Small Micro Enterprises (SMEs).

Table 2.5

SATRP tyre categories

Category Type of tyre

1 Passenger car tyres

2 Commercial vehicle tyres

3 Agricultural equipment tyres

4 Motorcycle tyres

5 Industrial and lift truck tyres

6 Earthmoving equipment tyres

7 Aircraft tyres

8 Other pneumatic tyres

The SATRP plan addresses the waste tyre problem in the same manner as the REDISA plan

as shown in Table 2.5.

2.4.2.1 Waste Tyre Hierarchy

Fig. 2.14 SATRP waste tyre hierarchy [38].

30

Waste Tyre Avoidance and Reduction: Priority will be given to preventing and reducing

waste tyre generation through the launching of awareness campaigns on maintenance and

producers guidelines. Secondly, the SATRP plan will encourage investment in the retreading

industry and actively promote the use of retreaded tyres. Used tyres classified as retreadable

by tyre dealers as required in terms of regulation 7 (1) of the Waste Tyre Regulations of 2009

to be directed to retreading plants[15].

Re-use: The re-use of a product is defined in the Waste Act, 2008[39] as “utilising articles

from the waste stream again for a similar or different purpose without changing the form or

properties of the articles”. The re-use of waste tyres is defined as “the utilisation of waste

tyres, in whole or in part, without changing the composition of the waste tyre”. The

Guidelines list the applications for whole, cut or shredded tyres as well as crumble rubber,

Table 2.6 and 2.7 [38].

Table 2.6

Various applications for whole, cut, or shredded tyres

Application Material

Source Method

Whole tyre Cut tyre Shred Chip

Embankments x

x x PW, TW, MW M, A

Erosion control x x x x PW, TW M, A

Landfill engineering x

x x PW, TW M, A

Slope stabilization x

x x PW, TW M, A

Temporary roads x

x x PW, TW M, A

Thermal insulation x

x x PW, TW, MW M, A

Collision barriers x x x x All M, A

Light weight fill x

x x PW, TW, MW A

Noise barriers x x x x PW, TW, MW M, A

Train and tram train beds x PW,TW M, A, C

Key for Table 2.6

Sources Technology (size reduction)

PW Whole passenger tyres

M

Mechanical (cut, compress)

TW Whole truck tyres

C

Cryogenic size reduction

MW Mixed whole car/truck tyres A

Ambient size reduction

ALL All

Recycling: Table 2.7 shows some or the recycling technologies for crumbed rubber which are

considered in the SATRAP plan.

Recovery: currently, there are very few energy recovery initiatives from waste tyres in South

Africa, such as cement, lime or steel production and power stations. The authorization of the

31

use of waste tyres as a substitute for fossil fuel is done on a plant by plant basis according to

the existing provisions of the Waste Act, 2008 and the Department of Environmental Affairs

(DEA) National Policy on thermal treatment of general and hazardous Waste

Table 2.7

Various applications for crumbed rubber

Application Material Technology

G P B R

Concrete construction additives

P

Asphalt additives

x

P, D

Asphalt rubber x x

A, C

road furniture x x

x A, C, R, D

Keys to Table 2.7

Material Source Technology

G-Granulate PW-Whole passenger tyres C-Cyrogenic size reduction

P-Powder TW-Whole truck tyres A-Ambient size reduction

B-Buffings MW-Mixed whole car/truck tryes D-Devulcanization

R-Reclaim ALL All

R-Reclaim

D-Devulcanizates P-Pyrolysis

Y-Pyrolytic products

Z-Upgrade material

2.4.2.2 The plan in a nutshell

Job creation: The job creation potential of the SATRP Company Industry Plan, over the 5

year period of implementing the plan is forecast to be in: (i) new tyre dealers, (ii) waste tyre

transportation, (iii) waste tyre transfer sites, (iv) Waste tyre processing. The potential

contribution of the SATRP Company Industry Plan to the green economy is therefore

forecast at 5000 informal jobs transformed to formal jobs; 5060 PDIs new jobs created; 1500

SMMEs created; and 335 SMEs created[38].

Training and development: The SATRP Company will develop training programmes for

informal tyre dealers to enable them to provide an upgraded service to their customers.

Included is the provision of (i) fully equipped workshops; (ii) training in the use of the

equipment provided; (iii) training in general business management and finance (iv) support in

stock control and supply (v) business skills for SMEs.

32

Previously disadvantaged individuals (pdi’s): Individuals presently employed in the informal

second-hand tyre trade will be incorporated into the formal market by means of a training

programme and the provision of tools and equipment and the forming of SMMEs. The

SATRP Company will, together with professional organisations, launch a programme to train

the present roadside and township informal tyre dealers to become recognised as part of the

formal tyre industry.

Auditing: The SATRP Company will appoint external auditors for a period of three (3) years

through a tender process.

Research and development: The SATRP Company intends working closely with its

international partner in the area of research and development. Matters currently under

research are; road surface treatment, concrete composite and odours. Products presently being

developed are: fibres for reinforcing road coating materials, thermoplastic compounds,

acoustic screens and textile fibres used as fuel[38]. The SATRP Company plans to approach

the Council for Scientific and Industrial Research (CSIR) as well as the Department of

Science and Technology to specifically consider issues of the South African environment.

The rate to be charged to subscribers to the SATRP Company Plan will be R1.98/Kg,

resulting in a cost estimation of R487 million during the first year of operation[38]. It is

estimated that 30 transfer sites will be required to store and pre-process the waste tyres

collected from tyres dealers and the legacy stockpiles.

Based on Fig. 2.15, it is evident that the SATRP Company will prioritise its plan mainly on

instituting a well routed and reliable waste tyre transportation system as well as properly

established transfer sites. Only 1.3% of the total cost will be allocated for research and

development. This percentage might need to be revised in order to have a growing

technological plan. Research and development is essential for the integration of new and old

waste tyre treatment technologies.

33

Fig. 2.15 SATRP Initial cost estimates

2.4.3 Integrated Industry Waste Tyre Management Plan of The Retail Motor Industry

Organisation (IIWTMP-RMIO)

In accordance with the Waste Tyre Regulations, the purpose of this plan is to facilitate and

manage the disposal of waste tyres in accordance with the Waste Tyre Act of 2009. Research

done by the RMI show that, majority of fitment centres has entrepreneurs collecting their

scrap tyres. In some instances these tyre collectors have been involved in doing so for 3

generations[40]. The RMI further supports the implementation of a collaborative integrated

Waste Tyre Management Plan that includes all stakeholders within the tyre industry. This

level of involvement will ensure sustainability of a new industry, given their expert industry

experience. Tyres shown in Table 2.8 will become waste tyres and will be managed through

the integrated industry waste management plan:

R1.98/kg

Research & Development

= 1.3%

Transport contractors

= 44%

Transfer sites

= 24.5%

Waste tyre processors = 14.6%

Abatement of stockpiles

= 5%

Social &Training

= 4%

Marketing =3%

Administration

=3.5%

34

Table 2.8

RMIO tyre categories

Category Type of tyre

1 Passenger vehicle tyres

2 Commercial vehicle tyres

3 Agricultural equipment tyres

4 Motorcycle tyres

5 Construction and earthmoving equipment tyres

6 Pedal cycle tyres

7 Aircraft tyres

8 Other diverse tyres

2.4.3.1 Waste Tyre Hierarchy

The Parties to the Plan intend implementing the tyre hierarchy in the following manner as

presented in Fig. 2.16.

Fig. 2.16 RMIO waste tyre hierarchy [40]

Reuse: The Retail Motor Industry Organisation (RMIO) recognises reusing of waste tyres as

their main priority in the waste tyre hierarchy; this is fundamentally identified as retreading.

Recycle: Mechanical shredding and crumbing are the preferred methods of recycling as well

as reclaiming. Crumbing activities render tyre waste as suitable raw material for many

processes such as moulded rubber products, road surface and many others. Crumbing is also a

precursor for reclaimed rubber. The latter is exportable and used in small quantities in many

rubber formulations for a variety of moulded and extruded products. The Plan will also

actively promote and support the establishment of recycling facilities throughout the country.

35

Incineration: Incineration will be facilitated through processes such as pyrolysis as well as

energy recovery for power generation advocacy. The pyrolysis products obtained are fuel

oils, char/carbon black and steel from waste tyres. These value added products are saleable

and a source of sustainable income. Energy recovery from waste tyres can be beneficial to

South Africa in order to reduce the carbon footprint that coal currently imposes in South

Africa.

Export: Export is preferred to landfill, illegal dumping and burning disposal. It has the benefit

that waste tyre volumes in excess of recycling and other requirements are disposed of in a

more environmentally friendly manner. Furthermore the process of preparing waste for

export to be used for steam generation can create jobs.

Landfilling: Landfilling is the last resort in the waste tyre hierarchy; it is undesirable and

should be avoided.

2.4.3.2 The plan in a nutshell

The potential number of waste sites is estimated at about fifty countrywide. Sites may vary in

size depending on the geographical location and the consumer concentration as well as waste

generators.

National awareness: The RMI currently actively promotes awareness in relation to the

management of waste tyres in various advertising mediums, including national and regional

media, in their monthly magazines and monthly newsletters, and as well as at national and

regional meetings/road shows. Funding will also be made available for consumer awareness

programs.

Job creation: The plan provides for on-going monitoring of job creation in the various

processes. Preferences will be given to the lower income earners and previously

disadvantaged, whilst not excluding the existing industry.

Training and development: The fund will establish a full training committee to deal with

training and skills development matters throughout the value chain. The approach of the

parties to the plan is to develop their candidates into independent businessmen who will

compete in local markets and international export markets.

36

New opportunities: The parties to the plan believe these actions will spawn many profitable

downstream industries such as moulded rubber products, chemical, oil refinement and

servicing export markets with these derived products.

Independent auditors: To ensure transparency, all movement of waste tyres, from import

and/or manufacturers of new tyres and casings to final recycling or other disposal, will be

suitably documented, audited and reconciled on the National Centralized Computer System

(NCCS). The operations of all recyclers and processors will also, at their cost, be audited in

terms of the Companies Act and other applicable legislation.

Research and development: The Research and Development department, under the auspices

of the Fund, will also be active in providing other processes applicable to our environment.

All participants will be encouraged to do the same and the plan will not knowingly support

any illegal practices harmful to the environment.

2.4.4 Analysis of the plans

The proposed REDISA Plan has come at a time when South Africa needs to reinforce

stringent laws on their waste management strategies in particular the waste tyre problem.

Before the proposition of the plan no clear approach was used to tackle the accumulation of

waste tyres at landfill sites and illegal stockpiles. Beside, addressing the waste tyre problem

which includes the setting up and managing a national network for collecting and temporarily

storing waste tyres, delivery to recyclers, as well as supporting the development of a waste

tyre recycling industry, the plan also helps with job creation, capacity building, and creation

of small businesses as well as research development of new and innovative techniques on

waste tyre utilization. Despite the various challenges and criticism the plan has received from

competitors, it has been gazetted and only awaits implementation. However, the plan lacks

media coverage as majority of tyre dealers from disadvantaged communities, who account for

75% of waste tyre recycling[40], are not knowledgeable about the existence of the plan.

Lastly, the REDISA stockholders should compare the proposed SA levy to those in other

countries. The authors support the REDISA plan as a well thought solution to the waste tyre

problem. The Plan is seen as a viable approach to remedy the waste tyre problem through the

introduction of a proposed levy fee of R2.30.

The SATRP Plan is an all rounded and well detailed plan which took into account most of the

relevant key objections which are required for the IIWTMP. However, the Department of

Environmental Affairs has the following objections about the plan: The SATRP plan has

37

excluded some of the key issues, for examples, the inadequate consideration of the Waste

Hierarchy, which is the cornerstone of waste legislation in the country. In addition, the plan

failed to address the inclusion and development of previously disadvantaged communities,

which are currently involved in the informal tyre sector.

Lastly, although the RMIO has existed longer than both SATRP and REDISA, the plan

however lacked clear direction in its waste tyre strategy. The plan was not inclusive of future

projected costs as well as implementation strategies. This resulted in a poorly drafted plan

which lacked the inclusion of current waste tyre dealers in the plan. However, it is evident

that RMI supported the implementation of new technologies such as pyrolysis into their plan.

2.5 Waste Tyre Disposal Alternatives

While considering the disposal of used tyres, it is essential to be aware of the different

materials and substances used in the production of tyres. Tyres are a multifaceted mixture of

very different materials. Natural or synthetic rubber, mixed with several ingredients, upon

vulcanisation and coupling with the wire gauze, forms the tyre. Due to the vulcanised nature

of rubber, used tyres are not directly reusable in the production cycle. In fact, the

vulcanisation transforms the elastomer into a non- fusible and insoluble substance.

2.5.1 Rubber

Tyres are designed to be tough and hard-wearing, once they reach their end of life they are

difficult to dispose. The main component of tyres, rubber, is a chemically cross-linked

polymer; which is neither fusible nor soluble, consequently cannot be remoulded without

degradation[41]. In rubber manufacturing, vulcanisation thermally disintegrates rubber

creating a hard plastic rubber that retains its form for tyre application. Antioxidants are added

to tyres to counter zone effects and material fatigue. The addition of steel, rayon and nylon

plus the process of vulcanisation contribute to the non-recycling character of tyres. The

processes and facilities required to extract rubber, steel and fibre from tyres are costly, and

the resultant products are generally of low value[42]. Two major approaches to address this

problem are recycling and the reclaiming of raw rubber materials.

2.5.1.1 Reuse of used and waste rubber products

Polymers can be classified as thermoplastics or thermosetting materials. Thermoplastics

soften when heated, may be moulded and then cooled to obtain the desired geometry. This

process may be repeated either by direct reheating or preferably after grinding into granules.

38

Thermosetting (thermosets) materials, like rubbers, upon processing and moulding are cross-

linked and therefore cannot be softened or remoulded by heating again. Chemical additives

are generally incorporated into both thermoplastics and thermosets as stabilizers, flame-

retardants, colorants and plasticizers to optimize product properties and performance. As a

result, thermoplastics are more readily recyclable than thermoset polymers and rubbers.

Recycling of thermoplastics simply involves a reversible physical change by heating the resin

above its processing temperature for reshaping and then cooling to room temperature to

obtain the desired recycled product. Hence, recycling of thermoplastics is less troublesome

and the technology for its re-fabrication is well established and economical. However

recycling for thermosetting materials like rubber is difficult. The three dimensional network

of the thermoset polymer must be broken down either through the cleavage of crosslinks or

the carbon–carbon linkage of the chain backbone. This is a much more resilient process and

the fragmented products obtained by such cleavage are entirely different from the starting

thermoset or even its precursor thermoplastics material. Thus, a recycled thermoplastic

material competes directly with the virgin polymer. Its commercial viability depends upon

the performance or cost benefit of the finished product, in contrast to thermoplastics. The

technology for the recycling of thermoset polymers including rubbers is complex, costly and

less viable commercially[42]. Reclaimed thermoplastics are used along with virgin resins and

fresh additives to obtain desired properties in the formation of final products. Recycled

plastics undergo significant changes in physical properties in its recycle phase, but still it

retains an acceptable fraction of virgin resin properties[43]. This behaviour is also observed

in reclaimed rubber.

2.5.1.2 Reclaiming of rubber raw materials

The 2003 waste tyre situation in South African was as follows, 10% of waste tyres were

landfilled, 4% recycled and the remaining 86% illegally re-grooved or dumped in the veld

and burnt to recover steel or stockpiled [38]. The statistics for developed and developing

counties is also shown in Table 2.9 [38, 44].

39

Table 2.9

2010 Global waste tyre treatment situation

Method of treatment (%) France Germany Italy Cyprus Spain UK

South Africa (2003)

Reuse 9,18 1,63 0 0 0 9,65 -

Export 0 13,68 3,58 0 2,82 11,84 0

Retreading 10,98 7,33 12,84 0 10,09 7,02 -

Civil Engineering Application 9,69 0 5,97 0 4,69 16,45 -

Recycled 32,65 35,02 23,88 0 18,78 32,67 4

Energy 37,5 42,35 53,73 0 42,78 22,37 -

Landfill 0 0 0 100 21,36 1,97 10

Towards the end of the1950s, nearly one fifth of the rubber used in the United States and

Europe was reclaimed. By the middle of the 1980s less than 1% of the world polymer

consumption was in the form of reclaim[45]. In the beginning of the 20th

century half of the

rubber consumed was in the form of reclaim. It is expected that during the 21st century most

of the scrap rubber will be recycled in the form of reclaim due to increasing environmental

awareness.

Engineering and construction application:

The rubber reclaimed from waste tyres has several applications. In civil engineering and the

construction industry, they are used for play-ground surfaces, parking lots, bank stabilization,

under road surface filling and asphalt modifiers. Tyres have essential building properties such

as light weight, low earth pressure, good thermal insulation and good drainage properties.

Another important property is its improved damping property which is good for running

vehicles. However, recent fires have set back the use of ground scrap rubber for many of

these applications[42].

In most of these applications, scrap tyres replaces other construction materials. Rubber

modified asphalt has increased durability, reduced reflective cracking, thinner lift and

increase skid resistance[46]. Asphalt modified rubber is also used for water-proofing

membranes, crack and joint sealers, hot mix binders and roofing materials. The rubber

improves asphalt ductility, thus increasing the temperature at which asphalt softens. The

aggregate adhesive bond becomes stronger and increases asphalt shelf life.

40

Building environment application:

Rubber is used for retaining walls, erosion control, barricading of shoring embankments, road

embankment fill and thermal insulation in housing foundations.

Agricultural application:

Farmers may use waste tyres as erosion control barriers.

Application of shredded, crumbed and granulated tyres

Shredded tyres can be used as fillers in roads, railway and construction developments. Finely

shredded old tyres can also be used as mulch (protective cover) which is long lasting, and is

presumed to be non-leachable[45]. Rubber mulches (in a variety of colours) have been

awarded innovation awards, and are becoming widely used in gardens, parks, playgrounds

and equestrian arenas. Rubber mulches are said to be permanent and aesthetically pleasing

landscape materials. Waste tyre recycling is a promising environmentally-friendly solution to

the waste tyre challenge in South Africa.

2.5.2 Material recovery

Waste tyre can be milled to obtain powder or granules with a specific configuration using

various techniques such as mechanical milling, cryogenic milling and de-vulcanization

processes. However, de-vulcanization processes are rarely used because of their high

operating costs[46].

2.5.2.1 Tyre remoulding

Fatigued rubber is replaced with a new tread. The new tread rubber is fused to the old carcass

by vulcanisation thus, re-treading the old tyre.

2.5.2.2 Mechanical milling

Rubber is broken down by mechanical shredding at high temperatures with the purpose of

recovering steel wire. Milling plants are normally of low cost and produce minimum

emissions. However, the high power consumption and limited market for the products are the

main drawbacks and thus require further research[46].

2.5.2.3 Cryo-mechanical milling process

In the mid-1960s, the technique of grinding scrap rubber, particularly tyres, in cryo-

mechanical process was developed[47]. Cryogenically ground rubber is used in tyres; hoses;

belts and mechanical goods; wire and cables and various other applications. This is

41

particularly useful in tyre inner liners. In this process, the rubber is cooled using liquid

nitrogen at a temperature range of -60oC to -100

0C. The rubber becomes fragile and mills

easily into very fine particles using ball or hammer milling. The high consumption of both

energy and liquid nitrogen make the process very expensive.

2.5.2.4 Microwave method

This is used to cleave carbon–carbon bonds. Waste tyres and rubber material can be

reclaimed without de-polymerization to a material capable of being re-compounded and re-

vulcanized with physical properties equivalent to the original vulcanizate. This route provides

an economical and ecologically sound recycling method for waste tyres. Furthermore, this

process can produce products similar to virgin rubber. It has been found that the tensile

property of de-vulcanized rubber and virgin rubber blend is almost comparable[48]. The cost

of de-vulcanized hose and inner tube material by microwave method is only a fraction of the

cost of the original compound. The transformation from waste to refined stock ready for

remixing takes place in only about five minutes with usually 90–95% rubber recovery[47].

Therefore, the microwave technique is a unique reclaiming process with regards to product

properties and process swiftness.

2.5.3 De-vulcanization technologies

The following section deals with the types of de-vulcanization technologies; they are

identified and grouped into the following categories:

2.5.3.1 Chemical

Organic Solvents

This type of chemical method is based on the use of 2-butanol solvent as a de-vulcanizing

agent for sulphur-cured rubber under high temperature and pressure. Reference[49] reported

that the molecular weight of the rubber is retained and its microstructure is not significantly

altered during the process. However, the process is extremely slow and requires separation of

the de-vulcanized rubber from the solvent. The process is applicable to de-vulcanization of

finely ground tyre rubber, but so far it has been carried out only on a very small laboratory

scale. Another type of chemical technology uses a solvent to treat the surface of crumb rubber

particles of sizes within 20 to 325 mesh. This is similar to the proposal by Hunt and Kovalak.

The process is carried out at a temperature range between 150° to 300°C, at a pressure of at

least 3.4 Mega Pascals, in the presence of solvent selected from the group consisting of

alcohols and ketones[50], [51], [52].

42

Oils and chemicals

Diallyl disulphide is the major constituent in a simple process for reclaiming rubber using a

vegetable product that is a renewable resource material. Other constituents of this material are

different disulphides, monosulphides, polysulphides, and thiol compounds[53]. Sulphur

vulcanized natural rubber (NR) can be completely recycled at 200° to 225°C by using

diphenyl disulphide. A decrease on crosslink density by 90 % was found when ethylene

propylene diene monomer rubber (EPDM) sulphur vulcanizates and diphenyldisulphide were

heated to 275°C in a closed mold for two hours. At the same time, EPDM cured by peroxide

showed a decrease in crosslink density of about 40 % under the same conditions[54].

Inorganic compounds

Discarded waste tyres have been de-vulcanized by desulphurization of suspended rubber

vulcanizate crumb (10 to 30 mesh) in solvents such as toluene, naphtha, benzene,

cyclohexane, etc. in the presence of sodium[55]. The alkali metal cleaves mono-, di-, and

poly- sulphur crosslinks of the swollen and suspended vulcanized crumb rubber at around

300°C in the absence of oxygen. However, this process may not be economical because it

involves swelling of the vulcanized crumb rubber in an organic solvent. In this process, the

metallic sodium in a molten condition should reach the sulphur crosslink sites in the crumb

rubber. In addition, the solvents may cause pollution and become hazardous.

2.5.3.2 Ultrasonic

Rubber de-vulcanization by using ultrasonic energy was first discussed in Okuda and Hatano

(1987). It was a batch process in which a small piece of vulcanized rubber was de-vulcanized

using 50 kHz ultrasonic waves after treatment for 20 minutes. The process apparently could

break down C-S and S-S bonds, but not carbon-carbon (C-C) bonds. The properties of the

devulcanized rubber were found to be very similar to those of the original vulcanizates[56].

One continuous process is based on the use of high-power ultrasound electromagnetic

radiation. This is a suitable way to recycle waste tyres and waste rubbers. The ultrasonic

waves, at certain levels, in the presence of pressure and heat, can quickly break up the three-

dimensional network in cross-linked, vulcanized rubber. The process of ultrasonic de-

vulcanization is very fast, simple, efficient, and it is free of solvents and chemicals.

43

2.5.3.3 Microwave

Microwave technology has also been proposed to de-vulcanize waste rubber[57]. This

process applies the heat very quickly and uniformly on the waste rubber. The method

employs the application of a controlled amount of microwave energy to de-vulcanize a

sulphur-vulcanized elastomer (containing polar groups or components) to a state in which it

could be compounded and revulcanized into useful products such as hoses. The process

requires extraordinary or substantial physical properties. On the basis of the relative bond

energies of C-C, C-S, and S-S bonds, the scission of the S-S and carbon-sulphur crosslinks

appeared to take place. However, the material to be used in the microwave process must be

polar enough to accept energy at a rate sufficient to generate the heat necessary for de-

vulcanization. This method is a batch process and requires expensive equipment.

2.5.3.4 Biological

Biological processing of vulcanized rubber has been used in some cases, although vulcanized

materials are resistant to normal microbial attack[58]. Several researchers have reported using

different types of microorganisms to attack the sulphur bonds in vulcanized elastomers. One

process uses a chemolithiotrope bacterium in a liquid solution to depolymerize the surface of

powdered elastomers. The polymer chains are then available to bond again during the

vulcanization process. The same type of bacterium has been shown to de-vulcanize crumbed

scrap rubber when held in an aerated liquid suspension of micro-organisms[59]. Reportedly,

sulphur can be recovered in this process, as well as de-vulcanized rubber. The rate of de-

vulcanization was found to be a function of particle size, with best results secured for

particles in the range of 100 to 200 microns. However, only a small percentage of the sulphur

links were broken after 40 days of exposure.

2.5.3.5 Other

Mechanical

A mechanical or reclaim process has been used for the continuous reclaiming of whole tyre

scrap. Fine rubber crumb (typically, 30 mesh), is mixed with various reclaiming oils, is

subjected to high temperature with intense mechanical working in a modified extruder for

reclaiming the rubber scrap.

44

Steam With or Without Chemicals (Digester)

The digester process uses a steam vessel equipped with a paddle agitator for continuous

stirring of the crumb rubber while steam is being supplied. The wet process may use caustic

and water mixed with the crumb rubber, while the dry process uses steam only. If necessary,

various reclaiming oils may be added to the mixer in the vessel. The dry digester has the

advantage of less pollution being generated. Scrap rubber containing natural and synthetic

rubbers can be reclaimed by the digester process, with the use of reclaiming oil having

molecular weights between 200 and 1,000[56].

2.5.4 Energy and material recovery

In light of the overall environmental impact along with the drive towards energy and material

conservation, new waste tyre disposal options are being developed and implemented.

Material and energy recovery through process, such as pyrolysis, can significantly address the

waste tyre disposal problem. Fig 2.17 shows possible waste tyre treatment routes.

Fig. 2.17 Technologies for managing scrap tyres[60]

2.5.4.1 Thermal treatment

The thermal treatment processes encompass combustion, incineration, gasification and

pyrolysis of waste tyres, with the following advantages[61]:

The volume of waste can be reduced by more than 90%.

Net energy production with possible material recovery.

45

Destruction of organic substances which are harmful to human health.

The following difficulties are associated with the thermal treatment of waste tyres[61]:

Disposal of ash: Lead and cadmium salts used as stabilisers during tyre production

remain as ash causing disposal problems.

Toxic gases: Burning of tyres produce toxic gases such as SO2, H2S, HCl, HCN and

these require further treatment.

Soot: Incomplete burning of waste tyres produces soot. This has a much higher

heating value than municipal refuse, so requires further combustion and hence

requires higher flame temperatures.

Appropriate incinerators: To address the challenges such as higher temperatures,

minimal oxygen conditions and corrosive action of the gases, appropriate materials of

construction are required.

Incineration

The incineration of waste tyres may be defined as the reduction of combustible wastes to

inert residue by controlled high-temperature combustion. A typical waste tyre incineration

process is shown in Fig. 2.18. The combustion process is spontaneous above 400oC. It is a

highly exothermic process and once the process has stabilized it becomes self-supporting.

The thermal efficiency of this process is approximately 40% [62]. Waste tyres having a

calorific value of 7.5 - 8 MJ/kg are used as fuel in incinerators. The gas produced may be

used as heat for industrial processing or electricity production. Burning of refuse in steam-

generating incinerators and using it as a supplementary fuel is advanced and proven waste to

energy utilisation [61].

Furnace design and efficiency influences the general combustion performance. Incinerators

have to be designed for excellent burning and reduced soot production. Walls and furnace

beds must be able to withstand high temperatures of approximately 1150oC. Combustion

efficiency, the ratio of thermal energy output to global energy input, usually depends on

interdependent factors such as the fuel's physical characteristics, plant design, manufacturing

and operating conditions. The use of waste as a supplementary fuel in power plants offers

many advantages and drawbacks as shown in Table 2.10

46

Table 2.10

Benefit analysis of incineration

Advantages Disadvantages

Maximum heat-recovery Large capital-investment

Low air-pollution emissions Need for flue-gas cleaning

Environmentally-acceptable process Relatively high operating cost

Reduced power-production costs Skilled labour is required to operate the

system

Fig. 2.18 The scrap tyre incineration process[60]

2.5.5 Pyrolysis, Gasification and Liquefaction (PGL) Processes

PGL processes present alternatives for the disposal of scrap tyres. These technologies are

currently used for the conversion of carbonaceous materials to resource fuels and other

products, and these may become more significant as the supplies of natural fuels become

depleted.

2.5.5.1 Gasification

Gasification is a sub-stoichiometric oxidation of organic material and a typical process is

shown in Fig. 2.19. The thermochemical process for gasification is more reactive than

pyrolysis. It involves the use of air, oxygen (O2), hydrogen (H2), or steam/water as a reaction

agent. While gasification processes vary considerably, typical gasifiers operate at

temperatures between 700 and 800°C. The energy efficiency of the gasification process is

reported to be around 76% [63]. The initial step, de-volatilization, is similar to the initial step

in the pyrolysis reaction. Depending on the gasification process, the de-volatilization step can

take place in a separate reactor upstream of the gasification reaction, in the same reactor, or

simultaneously with the gasification reaction. The gasification process can include a number

47

of different chemical reactions, depending on the process conditions and the gasification

agent. Equations 2.1 to 2.8 show gasification reactions for carbonaceous char.

C + CO2 = 2CO ∆H° = +172 kJ ………………………………………… (2.1)

C + H2O (g) = CO + H2 ∆H° = +130 kJ ……………………………………. (2.2)

C + 2H2O (g) = CO2 + 2H2 ∆H° = + 88 kJ ……………………………… (2.3)

C + 2H2 = CH4 ∆H° = - 71 kJ ……………………………………….. (2.4)

CO + H2O (g) = CO2 + H2 ∆H° = - 42 kJ ……………………………….. (2.5)

CO + 3H2 = CH4 + H2O (g) ∆H° = -205 kJ ……………………………….. (2.6)

C + 1/2 O2 = CO ∆H° = -109 kJ ……………………………………….. (2.7)

C + O2 = CO2 ∆H° = -390 kJ ……………………………………….. (2.8)

The oxygen requirement for the partial oxidation process can be supplied by air, oxygen

enriched air, or pure oxygen at a range of pressures. The method of delivery of the oxygen is

an important factor in determining the expense and efficiency of the process. Energy is

required to compress the combustion air or to cause the cryogenic separation of oxygen from

the air. This additional energy use lowers the overall energy efficiency of the process.

However, due to the absence of nitrogen in the final gaseous product, its calorific value can

be improved from relatively low values of 4 to 10MJ/ m3 using low-cost, air-blown partial

oxidation driven gasifiers, to values of 10 to 15 MJ/m3 for oxygen-blown processes and 25 to

30 MJ/m3 for hydrogen-blown processes, which compares well with natural gas, 39MJ/m

3.

Indirect heating of the feedstock in the gasifier through circulation of inert solid particles

such as sand from an externally fired heater may improve thermal energy management of the

process[61].

48

Fig. 2.19 Scrap tyre gasification process[60]

2.5.5.2 Liquefaction

In the early 1980s, pilot studies focused on the liquefaction of wood wastes. For scrap tyres,

this will involve melting the rubber and mixing the melt with another liquid such as waste

engine oil for processing. Practical methods have been tried. Pilot studies used steam and

catalysts producing oil with a heating value of 34.89 MJ/kg and a specific gravity of 1.03.

The costs of commercial production were estimated to be higher than coal liquefaction[64].

Liquefaction is the thermochemical conversion of an organic solid into petroleum like liquid.

Liquefaction typically involves the production of a liquid composed of heavy molecular

compounds with properties similar, but not identical, to those of petroleum based fuels. The

mechanisms involved in waste tyre liquefaction process are: diffusion of solvent into the

rubber; rubber swelling; rubber degradation; rubber dissolution; product separation from

insolubles. The gases and condensates are regarded as important by-products of waste tyre

liquefaction. The gases start to evolve at around 200C, the rate of gas generation reach

maximum as the mixture reaches the reaction temperature, and then decrease to a low but

steady value. Condensate generation follows a similar pattern to gases and is composed of

hydrocarbons ranging from C6 to C20. Tyres could be liquefied singly, or in combination

with other waste materials and/or coal in co-processing schemes, in one or two stage

processes. The idea of including tyres into a coal liquefaction process has been proven to be

more advantageous on a development plant scale. Liquefaction provides an effective

approach for converting the organic content into oils.

2.5.5.3 Energy recovery

Waste tyres can be utilised as a fuel source. Tyres produce the same amount of energy per

unit mass as oil and slightly more than coal [65]. Hence, they can be used as an efficient fuel

for industrial processes such as power plants with minimum negative environmental impact

49

compared to coal. In most cases tyres are shredded but the use of whole tyres is also possible

with large machinery. The presence of steel belts hinders the use of whole tyres. The

shredding of whole tyres and removal of wires can be integrated as part of the process.

Energy from the direct combustion of waste tyres can be utilized in metal works, paper mills,

tyre factories and on a smaller scale, in farms, greenhouses and sewage treatment plants.

Population growth and increasing individual income result in increased energy demand

exerting pressure on both energy supply and price. Rising international oil prices as well as

local transport demands combined with escalating up stream processes (refining and

extraction) signals the end of cheap oil.

Fig. 2.20 Primary energy supply in South Africa 1998-2009 [66]

Fig. 2.21 Energy usage by sector 2006-2009 [66]

0,%

10,%

20,%

30,%

40,%

50,%

60,%

70,%

80,%

Coal Crude oil Gas Nuclear Hydro Renewables

1998 1999 2000 2001 2002 2003 2004 2005 2006 2009

0%

5%

10%

15%

20%

25%

30%

35%

40%

45%

1998 1999 2000 2001 2002 2003 2004 2005 2006 2009

50

In early 2008, South Africa experienced a shortfall in power generating capacity which

resulted in wide spread power shortages. General awareness and understanding of the value

of energy was lacking in the past mainly due to historical low energy costs in South

Africa[67]. The primary energy source in South Africa is coal as shown in Fig. 2.20. The

industrial and the transport sectors use a significant amount of energy compared to other

sectors. Fig. 2.20 also shows South Africa‟s slow transformation to alternative energy

sources, indicating a greater dependence on coal. As coal usage produces a lot of emissions

impacting negatively on the carbon footprint, there is significant need for the country to

invest in cleaner energy sources.

Government has promulgated regulations and published supporting documents, namely;

green papers; white papers; bills; acts and regulations; international agreements and

obligations; guidelines and policies and gazetted notices to aid in the protection of the

environment as well as the country‟s natural resources. For the past ten years extensive

research, development and demonstration has been done with the key focus being on research

with respect to new technologies as well as the adaptation or evaluation of existing

technologies for specific South African conditions such as high unemployment rate. Some of

these initiatory steps entail the conversion of waste into valuable and profitable products.

Waste to energy processes recover energy in the form of heat and fuel from waste sources.

The aim of these initiatives, besides job creation and generating income, is to reduce waste

volumes going to landfills. This approach can be adapted to address the waste tyre problem.

Thermal and no-thermal technologies may be used for material and energy recovery for waste

tyres, Table 2.11.

Table 2.11

Waste to energy technologies

Thermal technologies Non-thermal technologies

Gasification Anaerobic digestion

Plasma arc gasification Fermentation production

Pyrolysis Mechanical biological treatment(MBT)

Thermal depolymerisation a) MBT+ Anaerobic digestion

b) MBT to Refuse derived fuel

51

2.5.5.4 Pyrolysis

Pyrolysis has been applied in the past to carbonaceous materials such as coal or wood. The

ancient Egyptians practiced wood distillation by collecting tars and pyroligneous acid for use

in their embalming industry. Pyrolysis of wood to produce charcoal was a major industry in

the 1800s, supplying fuel for the industrial revolution. Charcoal was used for the smelting of

metals and it is still used today in metallurgy[64]. For thousands of years charcoal has been a

preferred heating fuel until it was replaced by coal. In the late 19th

century and early 20th

century wood distillation was still profitable for producing soluble tar, pitch, creosote oil,

chemicals, and non-condensable gasses often used to heat boilers. The wood distillation

industry declined in the 1930s due to the advent of the petrochemical industry and its lower

priced products. However, pyrolysis of wood to produce charcoal for the charcoal briquette

market and activated carbon for water purification is still practiced in the United States of

America (USA)[64]. Over the last 20–30 years, several laboratory, pilot-plant and even

commercial attempts have been made to establish economical units for pyrolysis of such

materials for example; Kobe Steel in Japan, Tosco in the USA, Tyrolysis in the United

Kingdom, Ebenhausen in Germany and many more[68].

Pyrolysis is an endothermic process that induces the thermal decomposition of feed materials

without the addition of any reactive gases, such as air or oxygen. The thermal efficiency of

this process is approximately 70%, and can increase to 90% with the use of pyrolysis

products as fuel[69]. The use of tyre chips instead of whole tyres may also increase the

efficiency of the process by 20-30%[4]. Some of the problems related to the process are the

high cost of the plant and residue treatment[4]. The thermal energy used to drive the pyrolysis

reaction is applied indirectly by thermal conduction through the walls of the containment

reactor. Pyrolysis generally occurs at temperatures between 400 and 800°C[6]. As the

temperature changes, the product distribution (or the phase of the product) are also altered.

Lower pyrolysis temperatures usually produce more liquid products while higher

temperatures favour the production of gases.

The speed of the process and rate of heat transfer also influences the product distribution.

Slow pyrolysis (carbonization) can be used to maximize the yield of solid char. This process

requires a slow pyrolytic decomposition at low temperatures. Rapid quenching is often used

to maximize the production of liquid products, by condensing the gaseous molecules into

liquid. In some pyrolysis processes, a product that is up to 80% liquid by weight can be

52

produced[68]. Hydrogen or steam can also be used in the pyrolysis process to change the

makeup of the product distribution. Hydrogen can be used to enhance the chemical reduction

and suppress oxidation by means of the elemental oxygen in the feedstock. Steam can also be

used as a pyrolyzing medium, allowing pyrolysis to occur at lower temperatures and higher

pressures. The use of water as a pyrolyzing media also allows the feedstock to be introduced

into the reactor in an aqueous form. An additional advantage of water or steam is that the

resulting char has a relatively high surface area and porosity that is similar in nature to

activated charcoal. Nitrogen gas can be supplied to maintain the inert atmosphere in the

reactor and also to sweep away the pyrolyzed vapour product to the condensers. Furthermore,

purging the system with nitrogen helps to minimise secondary reactions in the hot zone.

Some of the problems related to the process are the high cost of the plant and residue

treatment[4]. Fig. 2.22 shows the pyrolysis process pathway.

Fig. 2.22 Scrap tyre pyrolysis process[60]

Influence of operating parameters on yield

The pyrolysis process yields a gaseous fraction of mainly non-condensable gases, a solid

fraction mainly composed of carbon, metal and other inert material as well as an oily fraction

mainly composed of organic substances condensable at ambient temperature and pressure.

The composition of the pyrolysis products is influenced by the process operating conditions

such as, feed size, operating temperature and pressure, residence time, heating rate as well as

the presence of catalytic medium.

53

Feed size

Smaller feed size particles provide more reaction surface, giving high heating rate and rapid

decomposition of rubber. The oil product vapours comparatively get enough time for

secondary reactions in the reactor and this consequently increases gas yield and reduces

liquid and char yields[68]. On the other hand, the heating rate in larger tyre feed is low due to

its lower thermal conductivity, in addition heat can flow only to a certain depth in the

available pyrolysis time compared to almost complete thermal decomposition of the smaller

pieces. Thus, the rubber core of the larger pieces becomes carbonized and/or cannot be

decomposed completely resulting in increased char yield and decreased liquid and gas yield.

Fig. 2.23 shows the effect of feed size on product yield.

Fig. 2.23 Effect of feed size on product yield[8]

Temperature

The increase in gas yield with a corresponding reduction in liquid yield with increase in

temperature is due to vapour decomposing into permanent gases, and secondary re-

polymerization as well as carbonization reactions of oil hydrocarbons into char [68]. It is

also a result of char loss and thermal cracking. Thus, high gas yields dominate at higher

temperatures, Fig 2.24.

0

10

20

30

40

50

60

Pro

du

ct y

ield

Increasing feed size

Liquids Char Gas

54

Fig. 2.24 Effect of temperature on product yield[8]

Residence time

An increase in vapour residence time decreases liquid and char yields while the gas yield

increases slightly. This is due to the decomposition of some oil vapour into secondary

permanent gases. Primary vapours are first produced from tyre pyrolysis at optimum

temperature, the primary oil vapours then degrade into secondary gases. For instance: oil

vapours→ heavy hydrocarbons + light hydrocarbons (CH4 + C2H4 + C3H6 +……) + (CO +

CO2 + H2)[68] leading to less oils and more gaseous products. In addition, longer contact

time of the volatiles and char leads to another parallel secondary pyrolysis reaction:

C + CO2 → 2CO which reduces the char yield[68], Fig 2.25.

0

10

20

30

40

50

60

Pro

du

ct y

ield

Increasing temperature

Liquids Char Gas

55

Fig. 2.25 Effect of residence time on product yield[8]

Table 2.12 shows a typical tyre composition. There are many different manufacturers with

various tyre formulations. Hence, the yield and composition of waste tyre pyrolysis depend

on the source and grade of tyres[68]. Table 2.13 shows a summary of the process operating

conditions, final product yields as well as the resulting pollutants for incineration, gasification

and pyrolysis.

0

10

20

30

40

50

60

Incr

ea

sin

g p

rod

uct

yie

ld

Increasing residence time

Liquid Char Gas

56

Table 2.12

Composition of whole tyres

Rubber 38%

Fillers (Carbon black, silica, carbon chalk) 30%

Reinforcing material (steel, rayon, nylon) 16%

Plasticizers (oils and resins) 10%

Vulcanisation agents (Sulphur, zinc oxide, various chemicals) 4%

Antioxidants to counter ozone effect and material fatigue 1%

Miscellaneous 1%

Elementary Composition

Carbon 86.40%

Hydrogen 8.00%

Nitrogen 0.50%

Sulphur 1.70%

Oxygen 2.40%

Proximate Analysis

Volatiles 62.10%

Fixed carbon 29.40%

Ash 7.10%

Moisture 1.30%

57

Table 2.13

Comparison of incineration, gasification and pyrolysis

Process Incineration Gasification Pyrolysis

Process

definition

The combustion of any waste

material to maximize waste

conversion to high heating

value fuel gases mainly CO,

H2 and CH4

Gasification is a sub-

stoichiometric oxidation of

organic material to

maximize waste conversion

to high temperature flue

gases, mainly CO2 and H 2.

The thermal degradation

of carbonaceous material

in an oxygen deprived

atmosphere to maximize

thermal decomposition

of solid into gases and

condensed liquid and

residual char.

Operating conditions:

Reaction

environment

Oxidizing (oxidant amount

larger than that required by

stoichiometric combustion)

Reducing (oxidant amount

lower than that required by

stoichiometric combustion)

Total absence of any

oxidant

Reactant gas Air Air, pure oxygen, oxygen

enriched air, steam

None

Temperature Between 850 oC and 1200

oC

[51]

Between 550 – 900 oC[63]

(in air)

Between 500 and 800 oC

[6]

Pressure Atmospheric Atmospheric Slightly above

atmospheric pressure

Process output:

Produced gases CO2, H2O CO, H2, CO2, H2O, CH4 CO, H2, CH4 and other

hydrocarbons

Produced

liquids

Treated and disposed as

industrial waste.

Condensable fraction of tar

and soot which is minimal.

Oil is similar to diesel

and can be used as a fuel.

. High aromatic content,

thus can serve as a feed

stock in the chemical

industry

Produced solids Bottom ash can be treated to

recover ferrous (iron, steel)

and non-ferrous metals (such

as aluminium, copper and

zinc) and inert materials (to

be utilized as a sustainable

building material).

After the combustion

process. Bottom ash is often

produced as vitreous slag

that can be utilized as

backfilling material for road

construction.

The pyrolysis char

residue has a

considerable amount of

carbon content and can

either be utilized as tyre

derived fuel for the

process or be sold as a

carbon-rich material for

the manufacture of

activated carbon or for

other similar industrial

purposes

Pollutants SO2, NOx, HCl, particulate H2S, HCl, COS, NH3, HCN,

tar, alkali, particulate.

H2S, HCl, NH3, HCN,

tar, particulate.

58

Pyrolysis gas

The approximate yield of gas from waste tyre pyrolysis is about 10-30% by weight[64] and it

increases with increasing pyrolysis temperature. The pyrolysis derived gas has a calorific

value of approximately 30-40MJ N/m-3

[62] and can be sufficient to provide the energy

required for a small scale process plant. The carbon oxide components (COx) are mostly

derived from the oxygenated organic compounds in tyres, such as stearic acid and extender

oils. H2S is a product of the sulphur links vulcanized rubber structure composition and its

concentration is low. C4 and >C4 gases are the most predominant products and these result

from the depolymerisation of styrene-butadiene-rubber (SBR), usually the main constituent

of automotive tyres. Table 2.14 [68] shows the gaseous constituents produced during the

pyrolysis of tyres. The components of the gas obtained from tyre pyrolysis at 400, 500, 600

and 700°C is shown by Fig. 2.26. The gaseous product mixture is made of shorter aliphatic

chains than SBR due to rubber cracking and subsequent reactions to form lighter gases.

Table 2.14

Pyrolysis gas constituents

Component Chemical formula

Carbon monoxide CO

Carbon dioxide CO2

Hydrogen sulphide H2S

Methane CH4

Ethane C2H6

Ethene C2H4

Propane C3H8

Propene C2H6

Butane C4H10

Butene C4H8

Butadiene C4H6

Pentane C5H12

Pantene C5H10

Hexane C6H14

Hexene C6H12

The undesired H2O and CO can be removed using several physical-chemical or biological

abatement methods. H2O can be abated using the following methods: (a) The Claus Process is

used in oil and natural gas refining facilities and removes H2S by oxidizing it to elemental

sulphur. The following reactions 2.5.1 to 2.5.3 occur in various reactor vessels and the

removal efficiency is about 95% using two reactors, and 98% using four reactors. (b)

Chemical oxidants are most often used at wastewater treatment plants to control both odour

and the toxic potential of H2S. The most widely used chemical oxidation system is a

combination of sodium hydroxide (NaOH) and sodium hypochlorite (NaOCl), which are

59

chosen for their low cost, availability, and oxidation capability, equation 2.5.4 to 2.5.5. (c)

Caustic scrubbers function similarly to chemical oxidation systems, except that caustic

scrubbers are equilibrium limited, meaning that if caustic is added, H2S is removed, and if the

pH decreases and becomes acidic, H2S is produced. The pH is kept higher than 9 by

continuously adding sodium hydroxide (NaOH), equation 5.2.6 describes the caustic

scrubber reaction[70]. (d) An adsorbing material can attract molecules in an influent gas

stream to its surface, this removes them from the gas stream. Adsorption can continue until

the surface of the material is completely covered, the materials must either be regenerated

(undergo desorption) or replaced. Regeneration processes can be both expensive and time

consuming. Activated carbon is often used for the removal of H2S by adsorption. Activated

carbon can be impregnated with potassium hydroxide (KOH) or sodium hydroxide (NaOH),

which act as catalysts to remove H2S[70]. (e) H2S scavengers are chemical products that react

directly with H2S to create innocuous products. Some examples of H2S scavenging systems

are: caustic and sodium nitrate solution, amines, and solid, iron-based adsorbents The

chemical products are applied in columns or sprayed directly into gas pipelines.(f) Amine

absorption units: Alkanolamines (amines) are both water soluble and have the ability to

absorb acid gases. Amines are able to remove H2S by absorbing them, and then dissolving

them in an aqueous amine stream. The stream is then heated to desorb the acidic

components, which creates a concentrated gas stream of H2S, which can then be used in a

Claus process unit or other unit to be converted to elemental sulphur. This process is best

used for anaerobic gas streams because oxygen can oxidize the amines, limiting the

efficiency and causing more material to be used[70]. Amines that are commonly used are

monoethanolamine (MEA), diethanolamine (DEA) and methyldiethanolamine (MDEA).

Amine solutions are most commonly used in natural-gas purification processes. They are

attractive because of the potential for high removal efficiencies, their ability to be selective

for either H2S or both CO2 and H2S removal, and are regenerable. (g) Liquid-phase oxidation

systems convert H2S into elemental sulphur through redox reactions by electron transfer

from sources such as vanadium or iron reagents. Hydrogen sulphide is first absorbed into an

aqueous, alkali solution. It is then oxidized to elemental sulphur, while the vanadium reagent

is reduced. This process is relatively slow and usually occurs in packed columns or venturis.

However, vanadium is toxic and these units must be designed so that both the “sulphur cake”

and solution are cleaned. (h) Using physical solvents as a method to remove acid gases, such

as H2S, can be economical depending on the end use of the gas. Hydrogen sulphide can be

dissolved in a liquid and later removed from the liquid by reducing the pressure. Water is

60

widely available and low-cost, it also has solubility potential for CO2. Other physical solvents

that have been used are methanol, propylene carbonate, and ethers of polyethylene glycol.

Criteria for selecting a physical solvent are high absorption capacity, low reactivity with

equipment and gas constituents, and low viscosity[71]. (i) Membrane Processes can be used

to purify biogas. Membranes are not usually used for selective removal of H2S, and are

rather used to upgrade biogas to natural gas standards. There are two types of membrane

systems: high pressure with gas phase on both sides of the membrane, and low pressure with

a liquid adsorbent on one side[71]. (j) Biological methods: microorganisms have been used

for the removal of H2S from biogas. Ideal microorganisms would have the ability to

transform H2S to elemental sulphur, could use CO2 as their carbon source (eliminating a need

for nutrient input), could produce elemental sulphur that is easy to separate from the biomass,

would avoid biomass accumulation to prevent clogging problems, and would be able to

withstand a variety of conditions (fluctuation in temperature, moisture, pH, O2/H2S ratio, for

example). Chemotrophic bacterial species, particularly from the Thiobacillus genus, are

commonly used both aerobically and anaerobically. Under limited oxygen conditions,

elemental sulfur is produced and under excess oxygen conditions, SO4 2-

is produced, which

leads to acidification.

⁄ …………………………………………… 2.5.1

…………………………………………… 2.5.2

⁄ ………………………………………….... 2.5.3

…………………………………………… 2.5.4

…………………………………… 2.5.5

…………………………………………… 2.5.6

61

Fig. 2.26 Compositions of the gases obtained in tyre pyrolysis at different temperatures[68]

Pyrolysis oil

There is need for greener fuel alternatives due to fossil fuel depletion, increasing oil prices

and emission challenges. Tyre pyrolytic liquids production pathways with their wide range of

potential applications are shown in Fig. 2.27.

Fig. 2.27 Tyre pyrolysis conversion and products applications[72]

0

0,005

0,01

0,015

0,02

0,025

0,03

COx H2S Total C1 Total C2 Total C3 Total C4 Total C5

g o

f gas

/g o

f ty

re

Constituent

400oC

500oC

600oC

700oC

Tyre wastes

Tyre Pyrolysis Liquids

62

The waste tyre pyrolytic liquid is an oily organic compound, dark brown in colour with a

strong acrid smell. This oil should be handled carefully as it reacts easily with human skin,

leaving permanent yellowish brown marks and an acrid smell for a few days, and this is

difficult to remove using detergents. The tyre derived oil is composed mainly of alkylated

benzenes, naphthalenes, phenanthrenes, n-alkanes from C11 to C24, and alkenes from C8 to

C15, with small quantities of nitrogen, sulphur and oxygenated compounds[72]. The pyrolysis

oil has a high calorific value of about 44 MJ/kg compared to that of waste tyres, 33

MJ/kg[72]. The calorific value of the oil is also higher than that of bituminous coal, 28

MJ/kg[73] and wood charcoal, 30 MJ/kg[74]. Pyrolytic oils can be used as liquid fuels for

industrial furnaces, power plants and boilers. The oil has a relatively low ash content and

residual carbon as shown in Table 2.15[64].

Table 2.15

Characteristics of vacuum pyrolysis waste tyre derived oil

Gross calorific value (MJ/kg) 43.8

Water content (wt.%) 1.6

Sulphur content (wt.%) 1.5

Chlorine content (ppm) 180

Carbon Conradson residue 1.8

Ash content (wt.%) traces

The liquids are very complex mixtures, containing aliphatic and aromatic compounds with

their total concentration of 49.54% and 16.65%, respectively[64]. The aliphatic compounds

mainly consist of alkanes and alkenes with alkenes being the predominant group, 43.23%.

The aromatic compounds are mainly single ring alkyl aromatics. The aromatic nature of the

waste tyre pyrolytic oils is due to aryl chain fragments from SBR aromatic rings splitting and

cyclisation of olefin structures through dehydrogenation reaction, Fig. 2.28.

63

Fig. 2.28 Formation of polycyclic aromatic hydrocarbons in scrap tyre [2]

Nitrogen and nitro-sulphureted compounds originate from the thermal degradation of

accelerators used in tyre compounding and these are usually sulphur and/or nitrogen based

organic compounds. The oils have higher carbon content, leading to the production of high

value carbon materials for various applications, Table 2.16 [72]. They are also contaminated

with little metallic elements, Table 2.17 [72]. The olefinic composition of the waste tyre

pyrolytic oil is similar to that of condensates from petroleum residues cracking and thermal

steam cracking of gasoline[4]. Hence, pyrolytic oil may be blended with these condensates

and subjected to the same thermal treatment.

Table 2.16

Elemental composition of oils obtained by vacuum pyrolysis of used tyres (wt. %)

Carbon Hydrogen Nitrogen Oxygen C/H

Passenger car tyres 86.5 10.8 0.5 2.2 0.67

Table 2.17

Waste tyre-derived pyrolytic oil impurities (ppb)

V Mn P Mg Na Ba As Ti Ni Fe Cu Al Zn Pb Ca Cr Cd CO

34 6 142 134 1280 198 73 5585 104 4030 104 4030 2044 918 458 93 24 26

64

Monoterpene [1-methyl-4-(1 methylethenyl)-cyclohexene], also known as limonene

constitutes about 30%[64] of pyrolytic liquids. dl-Limonene (dipentene) is produced from the

thermal decomposition of poly-isoprene or natural rubber. It has extremely fast growing and

vast industrial applications including formulation of resins and adhesives; dispersing agent

for pigments; fragrance in cleaning products and an environmentally acceptable solvent[69].

It also has applications in the cosmetic industry[75].

Pyrolysis Char

Activated carbon from pyrolytic char can be used for water purification and air purification,

as well as in batteries and fuel cells. Pyrolytic char has a calorific value comparable to high-

grade coal and may therefore be used as fuel either in pulverised or briquetted form. The

application of pyrolytic char as low grade carbon black for the manufacturing of

thermoplastics and a low cost adsorbent for the treatment of industrial effluents has also been

suggested[76]. The potential of the tyre carbon black product as possible adsorbents for

various pollutants has been assessed and found to be very successful, thus stimulating a huge

research interest[77]. Activated carbon can be used to adsorb phenols, basic dyes, metals, p-

chlorophenols, butane and natural gas. The production, characterization and uses of carbon

black as printing inks bases and recycled tyre fillers have been studied[77]. To enhance the

commercial value of waste tyre pyrolytic carbon black and increase its potential application

as activated carbon, further treatment such as chemical activation is required. This allows

both pyrolysis and activation to be integrated into a single, relatively lower temperature

process in the absence of oxygen. Demineralization of carbon black with acid (sulphuric and

hydrochloric acid) followed by activation at high temperature, normally 900oC, in a furnace

is common[76]. Commercial activation of carbon black is usually conducted at temperatures

above 800oC in a mixture of steam and carbon dioxide. There is general agreement that steam

is a more reactive agent than carbon dioxide[77]. Activation increases the surface area while

decreasing the concentration of contaminants or non-carbon material. Table 2.18[78] shows

the characteristics of untreated and activated carbon black samples.

65

Table 2.18

Surface area and elemental composition of pyrolytic carbon black and activated carbon black (wt%)

Surface area (m2/g) C O Si S Z Ca

Carbon black (not treated) 85 83.1 6.0 1.6 2.6 4.2 2.4

Carbon black (HCl treated) 870 93.0 5.1 0.4 0.9 0.6

Carbon black activated (HCl treated) 940 93.9 4.3 0.4 0.8 0.6

Carbon black (H2SO4) 800 87.0 5.9 0.6 1.8 2.9 1.8

Carbon black activated (H2SO4 treated) 910 30.0 4.4 0.6 1.2 2 1.8

Activated carbon (commercial) 990 96.0 2.9 0.3

Steam-activated carbon black present greater capacities for the adsorption of small and

medium size species such as phenol and methylene blue, while carbon dioxide-activated

adsorb larger molecular size compounds such as textile dyes more effectively[79]. Carbon

black characteristics are influenced by the nature of activation and process temperature to a

lesser extent.

Liquid-phase applications:

Activated carbon has been used in the removal of both organic and inorganic species from

industrial effluents[77]. Due to the high surface area 164 to 1260 m2/g and pore volumes up

to 1.62 cm3/g[80], tyre carbon black is considered as a potential adsorbent in water treatment

particularly for the removal of organic pollutants such as phenol and p-chlorophenol.

Potassium hydroxide (KOH) activated waste tyre pyrolytic carbon black can be used to

remove halogenated hydrocarbons and pesticides from drinking water. Tyre-derived carbon

may also be used to remove chromium, lead, copper, dyes and phenol from industrial waste

waters.

Gas-phase applications

Activated carbon from waste tyres provides an effective means for gas-phase applications

such as the separation, storage and catalysis of gaseous species. One example is the storage of

natural gas for automobiles in which natural gas is adsorbed on tyre carbons under high

pressure. It can also be used for the transportation of flammable gases such as acetylene[79-

81]. Pyrolytic carbon black may be used in the treatment of industrial gaseous effluents. For

example, it was found to have a similar sulphur dioxide (SO2) adsorption rate to commercial

lignite-based carbon[79]. It was also found to be superior in the adsorption of mercury[77].

66

Pyrolysis steel wires

The pyrolysis derived steel wire marketing depends on the cleanliness, quantity, and

packaging of the product. The cleanliness of recovered steel is measured by the degree of

rubber contamination. Steel with less than 10% rubber is considered acceptable in the

market[82]. Thermal processing of scrap tyres can be used to recover steel with minimum or

zero rubber contamination. The quality is also influenced by the pyrolytic process. For a

batch process, the separation of steel and carbon black from pyrolytic oil is fairly simple.

This is complex for continuous pyrolysis, gasification and liquefaction processes where tyres

are usually ground into chips. In addition, the recycling of the recovered steel in the

manufacturing of steel products is hindered by the burning of residual sulphur[82].

The waste tyre market is influenced by the business cycle. During off peak, the processors

may give away the steel for free or pay markets for collection. Bailing is difficult for steel

recovered from shredded tyres. The added cost of transportation and storage reduces the

income from this waste stream. However, this may be cheaper than paying a tipping fee for

disposal. Table 2.19 gives the summary of the waste tyre applications with their benefits and

disadvantages.

67

Table 2.19

Summary of waste tyre applications

Application/Product Benefit Disadvantages

Alternative Fuel (Cement kilns or

power stations)

Conserves natural resources;

High calorific value;

Large volume potential;

Recovery of carbon, steel,

rubber

Special monitoring

equipment required to control

emissions;

Generally needs shredded

tyres;

Needs feeding system;

Costly to operate

Steel electric arc furnace and foundry

kilns

Total and complete recovery

of tyre components: carbon,

steel, rubber;

Replace high cost carbon

Measuring equipment

required to control emissions;

Generally needs shredded

tyres;

Costly to operate

Landfill Engineering

Lightweight, low density fill

material;

Good load bearing capacity;

Lower cost compared to

gravel;

Does not need well qualified

labour

Potential leaching of metals

and hydro-carbonates;

The steel cord in the tyre

could puncture the lining;

Compressibility of the tyre

Light weight or drainage fill

Reduced unit weight

compared to other

alternatives;

Flexible, with good load

bearing capacity;

Good drainage

Potential leaching of metals

and hydro-carbonates;

Deformation under vertical

load, when a proper soil

cover thickness is not used;

Difficulty in compaction

(need to use more than 10ton

roller, six passes, 300mm

lift)

Erosion control

Low density which allows

free floating structures to act

as wave barriers;

Bales are lightweight and

easy to handle;

Durability

Tyres should be securely

anchored to prevent mobility

under flood conditions;

Tyres can trap debris, (needs

maintenance);

Can shift over time due to

wave action rendering tyre

structures insecure;

Water action and tyre

buoyancy makes the

positioning of any permanent

protection below the surface

very difficult;

Ultimately such tyres become

waste again

Noise Barriers

Lightweight, and can

therefore be used in

geologically weak areas

where traditional materials

would prove too heavy;

Free draining and durable

Needs monitoring to avoid

accumulation of debris;

Visual impact

68

Rubber modified concrete

Lower modulus of elasticity

which reduces brittle failure;

Increased energy absorption

making them suitable for use

in crash barriers etc.;

Suitable for low weight

bearing structures;

Can be reprocessed by

grinding and mixing again

with cement

Relatively new product,

producers will need to

convince the construction

industry of its suitability

Train and tram rail beds

Longer life span compared

with timber (20 year for

rubber beds and 3 to 4 for

wood or asphalt);

Environmentally safe;

Better flush with road;

Use chips/shreds as vibration

damping layer beneath sub-

ballast

More expensive than

traditional material;

Relatively new product,

producers will need to

convince industry of its

suitability

Outdoor sport surfaces (equestrian,

hockey and soccer) or artificial turf

Skid resistant;

High impact resistance;

Durable;

Highly resilient;

Easy maintenance;

Independent of irrigation

Indoor safety flooring

Skid resistant;

High impact resistance;

Durable ;

Available in various colours;

Easy maintenance

More expensive than

conventional alternatives;

Colours may be limited;

Limited market

Shipping container liners

Possible use with other

packaging problems

More expensive than

conventional alternatives

Conveyer belts

Possible use as conveyer belt

at supermarket tills

More expensive than

conventional alternatives;

Cannot be used where belt is

subject to large stresses,

since it may be prone to

failure

Asphalt and bitumen modification for

Road applications

Increased durability;

Surface resilience;

Reduced maintenance;

Increased resistance to

deformation and cracking;

More resistant to cracking at

lower temperatures;

Aids in the reduction of road

noise;

Substitutes virgin materials,

like styrene-butadiene-

styrene;

Significant environmental

benefits documented with

respect to global warming

potential, acidification and

cumulative energy demand

It is very sensitive to changes

in conditions during mixing

i.e. requires expert

knowledge;

Difficult to apply in wet

weather;

Not applicable when ambient

or surface temperatures are

less than 13º C;

Possible occupational health

problems due to emissions;

It cannot be reprocessed like

traditional asphalt

Footwear

Water resistant;

Long life span;

By varying the thickness of

Could be more expensive to

manufacture than

conventional product

69

the sole the use of the

footwear can be changed

Carpet underlay

Easy to use;

Recyclable;

Conserves natural resources

Limited industrial production

Floor tiles

Resilient;

Skid resistant;

High impact;

Easy maintenance;

Recyclable

Limited industrial production

Activated carbon

(carbon black) Preserves virgin material

Very expensive process as it

needs pyrolysis;

Very energy intensive;

Low grade activated carbon;

Still in the research stage

Livestock mattresses

Long life span;

Easy to disinfect;

Reusable;

In the long term it is cheaper

than alternatives

Could be more expensive to

manufacture than

conventional mattresses;

Market potential unknown

Thermoplastic Elastomers (TPE)

Similar properties to typical

elastomeric materials

Very limited existing sites

Pyrolysis

Reutilizes the sub products of

pyrolysis (oil and gas)

Limited capacity because of

operational problems caused

by tyres;

very limited existing sites;

The sludge originating from

the process contains metals

and other wastes, which for

the moment is deposited in

abandoned mines, poses an

environmental problem

2.6 Product Markets

In order for pyrolysis success and sustainability, a market for the derived products should

exist. The primary products (oil, char and gas) can be further processed to value added

products. Product upgrade is expected to significantly improve the economics of scrap tyre

pyrolysis. This can significantly improve the commercial viability of waste tyre pyrolysis.

2.6.1 Oil

Fuel oil is classified into six classes, fuel oil 1 to 6, according to boiling point, composition

and purpose. The boiling point ranges from 176 to 600oC. Oil derived from the tyre PGL

process is similar to No. 6 fuel oil. This is also regarded as residual oil as it contains various

impurities including 2% water and 0.5% mineral soil[61].

70

2.6.1.1 Characteristics of No.6 Fuel Oil

No. 6 fuel oil is a thick, syrupy, black, tar-like liquid. It smells like tar, and may even become

semi-solid in cooler conditions. It is also known as bunker oil or black liquor and consists of

a complex mixture of hydrocarbons with varying boiling points[83]. It is used as fuel for

steam boilers and power generators. It is generally bought in large quantities and stored in

large tanks, either above or below the ground[82]. Heating is required before application to

increase flow ability, reduce pump demands and promote burning performance. Cool or cold

No. 6 fuel oil is quite stable with a flashpoint of about 65oC[61]. However, the oil also

contains hydrocarbons with flashpoints below 65oC, hence it has enough flammable vapours

capable of starting a fire[61]. Further refining of No.6 fuel oil produces No.2 fuel oil. These

fuel oils are variously referred to as distillate oils, diesel fuel oils and light fuel oils which are

easy flowing at room temperature. No.2 oil does not require preheating to pump or burn as

compared to No.6 fuel oils. Distillate fuel oils are complex mixtures of hydrocarbons that

also contain small amounts of sulphur, nitrogen and oxygen containing molecules. They

contain normal and branched alkanes, cycloalkanes (naphthenes) and partially reduced

aromatics. Fuel oil No. 2 has a carbon range of C11-C20[84].

No. 2 oil can be used for home heating installations as well as for medium capacity

commercial and industrial burners. Liquid fuels, such as petrol, diesel and jet fuel dominate

the transport industry. Fig. 2.29 shows the various South African energy sources for transport

in 2010. Petrol and diesel dominate the application in this sector.

Fig. 2.29 Percentage distribution of energy types used in the transport sector in South Africa, 2010[85]

0

50

100

150

200

250

300

350

400

450

Gasoline Diesel Kerosene Electricity Natural gas

En

erg

y f

or

tra

nsp

ort

(1

015J

ou

les)

Energy Type

71

2.6.2 Char

Carbon black, an important industrial carbon, is any of various finely-divided forms of

amorphous (non-structured) carbon. Carbon exists in two crystalline forms, and numerous

amorphous, less-ordered forms. The crystalline forms are diamond and graphite, and the less-

ordered forms are mainly cokes and chars. Carbon blacks differ in particle size; surface area;

average aggregate mass; particle and aggregate mass distributions; structure and chemical

composition. The application of carbon depends on chemical composition, pigment

properties, state of subdivision, adsorption activity, and other colloidal properties[86].

Potential uses include upgrading to commercial carbon black, specialized carbon blacks,

printing ink, activated carbon, and fuel. The char from PGL processes with a heating value

close to 30.5 MJ/kg is a valuable energy source. Its heating value is higher than that of South

African lignite coals (16.7 MJ/kg) and compares well with petroleum coke (34.9 MJ/kg)[77].

Thus, the char from PGL processes can substitute coal.

2.6.3 Gas

The pyrolysis gas has high concentrations of methane and ethane, resembling a natural gas,

Table 2.21. In most pyrolytic processes, this is used as a source of fuel. The large quantities

of carbon monoxide and carbon dioxide in the gas hinder its blending with natural gas.

Table 2.20

Ultimate analysis of pyrolysis gas

Parameter Quantity

Carbon 85.76%

Hydrogen 14.24%

Nitrogen trace

Sulphur trace

Oxygen trace

Ash trace

Heating value 44.6 MJ/Kg

One major advantage of waste tyre pyrolysis is that the gas produced can be used as fuel to

sustain the process. The process runs with 10 – 15% of the gas generated. This significantly

reduces operating costs. The rest can be supplied to burners, boilers and internal combustion

engines or can be compressed and stored for future use[77].

72

2.6.4 Steel

Clean scrap iron and steel can easily be marketed. In order to increase the market potential of

steel from shredded tyres, it needs to be baled.

2.7 Successes and Failures of Waste Tyre Pyrolysis

In 2010, about 3.3 million tonnes of used tyres were managed in an environmental acceptable

manner in the European Union (EU), a 2% increase from 2009[87]. About 2.7 million tons of

used tyres were treated; the balance was either recycled or recovered[87]. The potential of

waste tyre treatment through processes such as gasification, pyrolysis and liquefaction is

undervalued. However with the increase in global awareness in environmental friendly

treatment methods, EU countries have considered these processes as future waste tyre

treatment methods.

Currently there is a great deal of research on waste tyre pyrolysis. Juniper[60] identified 40

companies worldwide working on tyre pyrolysis. However, there is only one dedicated tyre

pyrolysis plant in the United Kingdom (UK) operating on a semi-commercial basis. It is

owned by Anglo Unites Environmental (AUE) and handles 1500 tonnes of waste tyres per

year. Other semi-commercial plants have been operated in the UK, Germany, South Korea

and Taiwan, but with limited success. Most of them have ceased operation, reportedly due to

financial difficulties[88]. One of the most recent pyrolysis plant to be commissioned is in

Cyprus (May 2010), with a design capacity of 150 tonnes per month of N660 carbon black,

180 tonnes oil and 70 tonnes per month of steel[89].

Despite the 30 years of research and development, the pyrolysis of scrap tyres and related

waste materials has not achieved commercial success in the United States, with economic

viability and product quality being the primary stumbling blocks[87]. Despite all these

challenges, pyrolysis is still considered as a potential waste tyre treatment option for

developing countries such as South Africa.

Several pyrolysis plants have been shut down in South Africa due to limited and unregulated

markets as well as noncompliance with environmental regulations[90]. In South Africa,

presently there is one operating pyrolysis plant in Pretoria and another in Durban at the

commissioning stage. The Pretoria plant produces pyrolysis oil for industrial applications, the

gas is flared and no use for the carbon black has been found[91]. There are 12 other plants in

73

South Africa recycling waste tyres for other applications such as rubber crumb, mats and

sandals[92]. Major tyre companies like Goodyear and Firestone have invested in pyrolysis

but could not find markets for the by-products and also failed to integrate the venture into

their core business[93].

The main barriers for the development of tyre pyrolysis processes on a commercial scale are:

markets for pyrolytic char are presently not sound. Carbon black char is a fine particulate

composed of carbon black, ash, and other inorganic materials, such as zinc oxide, carbonates,

and silicates. Its application as virgin carbon black is very much restricted since it contains a

lot of impurities ±10%[88] and can only be used as low quality grade carbon black. Similarly

the use of char as activated carbon requires upgrading techniques to increase the surface area.

Reference[75] has shown that tyre pyrolysis oil can be used as a chemical feedstock to

recover valuable chemicals such as limonene. However, waste tyre oils are a complex

mixture of organics and the separation of these compounds to pure products can be costly.

74

CHAPTER 3

METHODOLOGY

75

The project is a desktop study which involves critical literature analysis, evaluation of waste

tyre treatment options, in depth studies of the pyrolysis process, socio-economic and

environmental analysis of waste tyre pyrolysis as well as pyrolysis plant model construction.

Fig.3.1 shows the steps which were followed to achieve the research objectives.

Fig. 30 Project route map

3.1 Project objectives:

Environmental and socio-economic impact of using waste tyre derived oil and carbon

black as alternative green fuels.

Pyrolysis products market survey.

Development of business model including costing, procurement, installation,

commissioning and operation of the pyrolysis plant.

Analysing the role played by informal and formal sectors in waste tyre management.

Assessment of the socio-economic and market opportunities for energy recovery from

waste tyres.

3.2 Research Methods

3.2.1 Interviews

Telephonic and personal interviews with waste tyre management personnel were conducted.

These gave insight on the current and future waste tyre management strategies in South

Africa. This covered governmental, communities, non-governmental and private sector

organizations. The interviews assisted in data collection and feasibility studies of operating a

waste tyre pyrolysis plant in South Africa. These interviews focused particularly on the

LITERATURE AND DATA

COLLECTION

CONCLUSIONS AND RECOMMENDATIONS

GENERAL DISCUSSIONS ,

MODEL CONSTRUCTION AND

EVALUATION

LITERATURE AND DATA ANALYSIS

UNDERSTANDING RESEARCH

QUESTIONS AND OBJECTIVES

TRIANGULATION PROCEDURE

- Literature reviews

- Site visits

- Personal and telephonic interviews with questionnaires

76

proposed three waste tyre management initiatives namely; REDISA, SATRP and RMI. These

investigations were also extended to waste management corporations, landfill personnel and

waste tyre treatment companies.

3.2.2 Site visits

Visits to waste tyre facilities gave insight on the scale of the waste tyre problem in South

Africa as well the existing mechanisms to address these challenges. Visits to pyrolysis

companies shed some light on the application of waste tyre products. Furthermore, the

information obtained assisted in building the pyrolysis plant model and operation.

3.2.3 Questionnaires

Questionnaires gave insight on waste management practices in South Africa, stakeholders in

waste management. Tables 3.1 to 3.4 show examples of questionnaires used in this study.

Table 3.1

Questionnaire: Pyrolysis plant

1 What is the capacity of the plant?

2 What are the process operating conditions?

3 Is it possible to integrate the process with other feed stocks?

4 What is the composition of the final products

5 Was feed material ever in short supply

6 Do markets exist for their final products?

7 Do they further process their primary products

8 Does the plant make profit?

9 Is the company aware of the REDISA plan, if yes, is there any cooperation?

10 Does the process comply with the air emission standards listed in the

National Policy for Thermal Treatment of General and Hazardous Waste?

Is the pyrolysis feasible, sustainable and profitable in Gauteng, South Africa?

Table 3. 2

Questionnaire: Public/Community

1 How do waste tyres affect the community‟s health and environment?

2 Do local municipalities have any collection mechanism for waste tyres?

3 Do waste tyres add value and can they be a source of income?

4 If yes to question 3, which is the most valued component part of the tyre?

5 Is the public aware of any waste tyre integrated waste management plan?

6 Are there any waste tyre recycling stations nearby?

7 Do communities know about the REDISA plan?

77

Table 3. 3

Questionnaire: Landfill sites

1 Do their landfill sites accept waste tyres?

2 If yes to question 1, how much is the disposal fee?

3 If yes to question 1, what do they do with the tyres after collection?

4 Are the landfill operators aware of the REDISA Plan?

5 Do waste pickers play any role in the recycling of waste tyres?

6 What are the health and environmental implications for accepting waste tyres?

7 Are there any mechanisms used for the handling of disposed waste tyres?

Table 3.4

Questionnaire: Government/Local municipalities

1 What are some of the waste tyre management practices offered by local governments?

2 Is there sufficient waste tyre management information being distributed to the general

public?

3 If yes to question 2, does the public know about the REISA Plan?

4 What is the main purpose for the existence of the REDISA plan?

5 How do local governments perceive technologies such as waste tyre pyrolysis?

3.2.4 Literature Analysis

A comprehensive literature study was carried out using reliable sources such as scientific and

research journals; refereed and peer reviewed conference proceedings; patents and companies

technical information. This helped in identify missing gaps and locating this work within the

broader field of study. This also helped in understanding concepts and operation of a waste

tyre pyrolysis plant.

3.2.5 Model Construction

Cost of equipment and operation facilities are fundamental in developing a feasible waste

tyre pyrolysis model. Two approaches were used to obtain the required information namely:

Engineering cost indices were used to estimate recent equipment prices. Operating pyrolysis

plants and their suppliers were used for costing equipment. Engineering rates for services

were obtained from the Engineering Council of South Africa (ECSA).

78

CHAPTER 4

GENERAL DISCUSSIONS

79

4.1 Role Played by Informal and Formal Sector in Waste Tyre

Management

Through literature analysis, questionnaires, site visits as well as personal and telephonic

interviews the research found several key participants in waste tyre management. These

include municipal governments, the informal private sector, community based organizations

and non-governmental organizations.

Recycling is a waste minimization option. Waste tyre recycling and resource recovery can

effectively reduce the amount of waste tyres disposed to landfills and open fields; they also

have the added benefit of conserving natural resources. Waste tyre recycling initiatives can

reduce land and air pollution through burning, manufacturing costs, litter and scavenging at

landfill sites. Employment opportunities can also be created through recycling[94]. The waste

stream‟s composition in an area reflects the community lifestyles and status. This can widely

vary from urban to rural areas and from higher to lower income communities, Fig.4.1. The

waste stream composition is influenced by disposable income. Waste tyres are predominantly

generated in high income areas as they afford luxuries such as multiple motor vehicles.

Fig 4.1 Waste streams in different communities [95]

4.1.1 Municipal Governments

Local municipal governments play key roles in the setting-up and operation of waste

management systems. Most urban authorities in both industrialized and developing countries

are empowered and tasked by central government to protect the rights of the citizens, provide

0

10

20

30

40

50

Per

cen

tage

(by m

ass)

of

tota

l w

aste

qu

anti

ty

Low density, higher income area High density, lower income area

80

waste services and to serve the common good[96]. They have to implement laws and

regulations in order to fulfil their constitutional obligations. The characteristics distinctive to

local governments when fulfilling their waste tyre management responsibility include

(i) mandatory obligation

(ii) use of public funds to achieve their waste tyre management objectives

(iii) regulating or contracting the private sector

(iv) political concerns.

The South African Constitution assigns responsibility for refuse removal, refuse dumps and

solid waste disposal, such as waste tyres, to the local government. District and Local

municipalities have different roles and responsibilities but also complement each other as

outlined in the Municipal Structures Act[97].

4.1.2 The Informal Private Sector

The term “informal private sector” refers to unregistered, unregulated or casual activities

carried out by individuals and/or family or community enterprises engaging in value-adding

activities on a small-scale with minimal capital input, using local materials and labour-

intensive techniques. The informal sector does not pay tax, has no trading license and is not

included in the social welfare or government insurance schemes[98]. Informal waste tyre

recycling is carried out by poor and marginalized social groups who resort to scavenging for

survival.

Informal activities in waste tyre collection and recycling are often driven by poverty, they are

individually initiated and spontaneously with the sole purpose of survival although aimed at

profit making. Consequently, the choice of waste to be collected is influenced by its value,

ease of extraction and handling as well as the transportation required. Paper, metal and plastic

wastes usually collected from the more affluent residential or industrial areas tend to attract

more attention than tyres. However, tyres are still burnt for steel recovery. Table 4.1 shows

the various individuals contributing to solid waste management.

81

Table 4.1

Role of the informal sector in waste tyre management

Category Role

Street pickers Recovery

Landfill scavengers Recovery

Collection groups Recovery

Dealers, neighbourhood dealers or buyers Buying (retail)

Small-scale entrepreneurs Buying , trading

Large-scale entrepreneurs Buying and large-scale processing

technology

Although waste pickers are self-employed, it is important to note that the informal economy

is linked to the formal economy as it produces for, trades with, distributes for and provides

services to the formal sector. In many countries such as Brazil, Argentina, Colombia and

Bangladesh, waste pickers are officially recognized. For example, since 2002, waste pickers

have been recognized in the Brazilian Classification of Occupations (CBO)[99]. Thus, waste

tyre management in South Africa needs to be fully integrated. Informal participants

(scavengers) need to be identified, recognized, trained and integrated into the formal waste

tyre management industry.

The recycling network takes the form of a hierarchy shown in Fig. 4.2[100]. The higher a

secondary raw material is traded, the greater the added value it possesses. Informal recyclers

tend to occupy, and are restricted to, the base of the secondary materials trade hierarchy and

this significantly reduces their potential income.

An estimated 88 000 South Africans currently earn a living through waste recovery [101].

Waste picking offers individuals a means to make a living regardless of age, level of

education or skills. Waste pickers contribute to higher levels of recycling within cities and

towns, and help to divert waste from landfills. Since they are linked to the formal sector, their

activities are subordinate to and dependent on the formal sector recycling companies while

waste picking is at the bottom of the recycling hierarchy. The Marie-Louise and Robinson‟s

Deep landfill sites, in the Gauteng region, accommodate waste pickers into their sites. Their

waste management is well organized with representatives. The waste pickers are responsible

for securing formal recycling companies themselves for the collection of their end-products.

82

Fig. 4. 2 Hierarchy of informal sector recycling

Handling waste poses many health risks to workers. These are even greater for informal

workers due to their daily unprotected exposure to contaminants and hazardous materials.

Despite the fact that waste pickers are solely responsible for the risks that their activities pose

to their health, municipalities assist them by providing protective gear to minimize those

risks[102]. Even though the amount of waste they recycle is not formally recorded, it is

believed to range between 5% and 7% of South Africa‟s yearly recycled waste[103].

4.1.3 The Formal Private Sector

This sector includes private corporations, institutions, firms and individuals operating

registered and licensed businesses with organized labour, capital investment and modern

technology[98]. This sector is motivated by making profit. The formal private sector is

involved in wide-range of waste management activities varying from waste collection,

resource recovery, incineration and landfill operation of all waste assortments, including

waste tyres. Its participation can be through entering into waste management contracts with

municipalities and individuals as well purchasing the recovered waste tyres. The formal

private sector is characterized by:

83

1) the potential for profits

2) use of private resources and

3) municipal regulation.

4.1.4 Community Based Organizations (CBOs)

The community and its representatives have a direct interest in waste management, as

residents, service users and tax payers. Communities in low-income areas generally receive

minimum services with regards to public transport, electricity, sanitation, drainage, and waste

removal[104]. Sometimes these communities take the initiative to organize themselves into

Community Based Organizations (CBOs) with the aim to self-help and improve their living

conditions. CBOs may receive external assistance in the form of technical and/or financial aid

from various agencies. Groups of citizens, including those from middle and high-income

areas, may start CBOs to improve waste management in their neighbourhood. Middle and

high-income communities generate more valuable waste compared to the poorer areas. CBOs

mainly participate in primary waste collection and separation at source initiatives.

4.1.5 Non-Governmental Organizations (NGOs)

NGOs are diverse organizations such as churches, universities, labour, environmental and

lobbies as well as donor organizations. They are generally intermediate organizations linking

communities and municipalities which are not directly involved in community waste projects.

NGOs, besides advocating are also involved in awareness-raising, support and decision

making. They can advocate interests on a larger scale than the single community, provide

support and advice to CBOs as well as marginal groups in the society, such as scavengers and

street children. The role of NGOs as partner organizations in waste management ranges from

serving as umbrella organizations under which CBOs operate, to providing a channel for

donor financing. CBOs and NGOs are motivated by a selfless desire to improve waste

management for communities and function outside the formal decision making structures of

municipal governments.

The following are a number of NGOs that are involved in environmental management,

including waste tyres, and conservation: (i) The Institute of Waste Management of Southern

Africa (IWMSA), is a multi-disciplinary non-profit association that is committed to

supporting professional waste management practices. (ii) The Wildlife and Environment

Society of South Africa (WESSA) is a South African environmental organisation with a

mission to implement high impact environmental and conservation projects which promote

84

public participation in caring for the Earth. With a remarkable 87 year history, WESSA

critically focuses on life-supporting eco-systems such as water, energy and biodiversity. (iii)

Earthlife Africa is a non-profit organisation, founded in Johannesburg, South Africa, in 1988.

The organisation‟s main mission is to encourage and support individuals, businesses and

industries to reduce pollution, minimise waste, and thus protect our natural resources.

4.1.6 Key issues and constrains

There are several fundamental constraints that hinder the development of inter-sectorial

partnerships among municipal governments, the formal private sector, the informal sector as

well as non-governmental and community-based organizations, such as financial constraints.

For all stakeholders, financial problems cover (i) for the municipal governments, constraints

on the use of taxpayers' money (ii) for the formal private sector, constraints on capacity,

credibility, liability and resilience (iii) for the informal private and community sectors,

generally marginal access to social institutions and limited access to finance. Sectorial

cooperation is hindered by the lack of belief in the legitimacy of other partners or the fear that

partnerships may disrupt the status quo, especially for marginal actors such as informal sector

entrepreneurs.

4.1.7 Informal and Formal Sector Integration

The income and living conditions of informal waste workers vary significantly, the majority

is confronted with extremely hazardous working and living conditions. They generally lack

sanitary services, health care and social benefits. Child labour is very frequent, and life

expectancy is low. The integration of the informal sector will assist scavengers to gain access

to personal protective gear and health care services. This will also reduce child labour as a

result of the stringent laws and regulations governing the formal sector. The informal sector

can achieve high waste tyre recovery rates of up to 80%[105] as the ability to recycle is vital

for their survival. A variety of recyclables are segregated and processed in accordance with

new demands and technological advancements in the recycling industry. However, a drop in

waste recovery rates was witnessed in Egypt following the introduction of the private sector

involvement in solid waste collection[106] indicating the significance of the informal sector

in running efficient recycling schemes. The diversion of waste from landfills through waste

minimization and recycling is a national policy objective. In response, the National Waste

Management Strategy (NWMS)[31] emphasizes the need for integrated waste management,

which implies coordination of functions within the waste management hierarchy. The

Department of Environmental Affairs has been designated as the lead agent for integrated

85

waste management. In addition, it is anticipated that the promulgated Waste Act (Act 59 of

2008) will address the various short falls previously discussed above. The main participants

in the waste sector including the management of waste tyres are outlined in Table 4.2[107].

Table 4.2

Main players in the South African waste sector

Type Name of Organisations Roles and Functions

National Department of Environmental Affairs Policy development

Government Department of Co-operative Government and Traditional Affairs Setting National Standards and

Targets, Department of Health,;Department of Transport, Department of Trade

and Industry; Department of Water Affairs; Department of Agriculture

Advisory, Regulation and

Inspection.

Forestry and Fisheries; Department of Mineral Resources Department of Energy

Provincial Provincial Departments dealing with Environmental Affairs Standards and Targets,

Authorisations,

Government Advisory, Regulation (e.g.

permitting of all general waste sites)

Local Metropolitan municipalities, District municipalities, Local municipalities Waste service delivery

Government South African Local Government Association (SALGA) Planning, Waste Disposal

Associations and Institute of Waste Management of South Africa (IWMSA) Networking

organisations National Recycling Forum (NRF), Health Care Waste Forum Information sharing

active in the Packaging Council of South Africa (PACSA), Recycling Action Group

(RAG)

Capacity building

waste industry Plastics Federation, Paper Recycling Association of South Africa

(PRASA)

Electronic Waste Association of South Africa (eWASA) PET Plastic Recycling South Africa (PETCO)

Buyisa-e-Bag, The Glass Recycling Company

Collect-a-Can, SAPRO, Recycling Association of SA (RASA)

Responsible Packaging Management South Africa

Recycling Industry Body (RIB), Rose Foundation (oil recycling)

Tyre Recycling Association, Scrap metal Association

NGOs WESSA, WWF,Groundworx, Earthlife Africa, Other Awareness raising

Clean-up campaigns Watchdogs

Waste Varying in size from one man contractors to large companies employing

more than 1000 people.

Re-claimers, Collectors,

Recyclers,

Contractors Operators of waste, management facilities, Treatment and safe

disposal of waste

Industry Any manufacturing or recycling plant, Energy from waste plants Recycling of recovered materials or waste

Professional Various firms Planning, design, construction,

Service Providers monitoring and auditing

Suppliers Various firms Suppliers of equipment and

materials

including: Vehicles, Compactors Geotextiles, Receptacles,

Containers,

Bin liners, Others Academia Universities, Science Councils Research and Development

86

4.2 Socio-Economic Impact of Using Tyre Derived Products

For the past decades, coal has been the primary source of fuel in most world countries

including South Africa. This was so because of its ample availability and lower price.

However, the use of conventional sources of energy such as coal and wood is being

discouraged globally due to the environmental and health risks they pose. This section

discusses the use of waste tyres which are readily available and pilling up in landfill and

dump site all over South Africa as an alternative source of energy.

Waste generation and energy shortages are the two major challenges in South Africa in

addition to other problems such as job creation and service delivery. The government and

private sector are under pressure to find effective and sustainable remedial measures to these

problems. South African policy makers have long been aware that the country was facing

impending power shortages. The 1998 White Paper on Energy Policy warned that power

shortages would become evident by 2007 and that to avoid a situation of demand exceeding

supply, a decision on supply-side investments would need to be made by the end of 1999[94].

Despite having been forewarned, South Africa now finds itself in a situation of power

shortages, load-shedding and power rationing.

4.2.1 Land filling ban of waste tyres

This section discusses the environmental and socio-economic impacts of the prohibition of

waste tyres disposal at landfill sites. A total ban on landfilling or an obligatory requirement

for the recycling of scrap tyres would require a long transition period and substantial effort to

create options for recycling and recovery. As a result, this may still result in a significant

amount of stockpiles, particularly in remote and rural regions. There is a huge transportation

costs that will have to be considered for the nation-wide collection and storage of waste tyres

in designated locations, as provided by the REDISA Plan.

From a South African point of view, majority of prominent landfills around the Johannesburg

district, such as Mariel Louise and Robenson‟s deep amongst others, have accepted the waste

tyre ban. These landfills do not accept any assortment of tyres in their site due to

environmental regulations. However, landfill sites such as the Mogale City landfill and other

surrounding sites situated in the west of Johannesburg accept waste tyres despite the ban, Fig.

4.3. The Mogale City Landfill site charges a fee of R13.00 per passenger tyre and R26.00 per

heavy commercial or agricultural tyre as shown by Table 4.3. In addition the landfill site

allows individuals to collect tyres from the site for recycling applications, Fig.4.4.

87

Fig 4. 3 Waste tyres disposed at the Mogale City landfill site

Table 4.3

Mogale City waste disposal rates

Waste type Quantity Price

Debris disposal fee, contractors and businesses Tonne R 136,98

Disposal of clean compostable refuse by Mogale city residents and

contractors in excess of 500kg Tonne R 83,32

Disposal of general and non-hazardous solid waste by any person outside the

boundaries of Mogale City Tonne R 166,58

Building rubble (less than 300mm in diameter) free R 0,00

Re-usable material free R 0,00

Tyres-rim size up to 40cm in diameter Per tyre R 12,96

Tyres-rim size greater than 40cm in diameter Per tyre R 25,91

Fig 4. 4 Tyres collected by alternative tyre manufacturers

88

4.2.2 The environmental impact

Local government

The major environmental benefit for the banning of waste tyres in landfills is the potential

improved use of landfill space. Based on the latest assessments, the remaining lifespan of

most landfills, when no additional diversions from land filling are implemented over and

above current diversion methods and excluding private landfills, is between 12 to 14 years

counting from 2010 onwards. South Africa‟s remaining landfill span is below the

international benchmark of banked landfill space of 15 years[108]. On the contrary, the ban

will also promote the implementation of stringent land filling laws.

Tyre recycling industry

The ban will force the tyre industry to find alternative methods for the disposal of their

products when they have reached their end use. This will encourage the tyre industry to

participate in tyre recycling schemes as well as energy recovery initiatives.

Community

The legal or illegal disposal of waste tyres poses severe health issues and fire hazard

concerns. However, due to the proposed ban, the environmentally acute effects of tyre land

filling and illegal disposal will be remedied through the introduction of waste tyre

management strategies, for example, as proposed in the REDISA Plan.

State government

Recycling and energy recovery initiatives will assist in improving waste tyre management as

well as environmental regulations and laws for this waste type.

Manufacturing or retail sectors

The ban will promote improved management strategies for landfills

4.2.3 Social impact

Local government

The ban will possibly increase employment particularly in the management and operation of

stockpiles, small micro and medium enterprises (SMMEs), and boost the local civil

engineering industry as well with regards to the construction and infrastructure management

of the stockpiles. In addition, relating to the REDISA Plan, the actual transportation process

of tyres to storage facilities will marginally provide employment to the transporters.

Tyre recycling industry

89

Employment will be created through tyre recycling and energy recovery initiatives. With

sufficient research in waste to energy, waste tyres can be thermally processed to produce

Tyre Derived Fuel (TDF) for commercial or industrial use.

Community

Poor communities relying on steel recovery from waste tyres, Fig 4.5 and 4.6 perceive the

ban to be undesirable and not beneficial to them as this is their source of income.

State government

An increase in employment in the recycling industry will be experienced and will result in

both government and private institutes willing to fund waste tyre initiatives.

Manufacturing or retail sectors

The collection of tyres from remote rural areas will result in increased economic

opportunities.

4.2.4 Economic impact

Local government

The ban on the landfilling of waste tyres will have a financial impact in the economy

through increased costs of enforcement to prevent illegal dumping, but this can be

remedied by introducing incentives to prevent illegal dumping through basic waste

management education practices.

Tyre recycling industry

The waste tyre ban will promote growth and business opportunities resulting in the

development of an integrated tyre manufacturing, recycling and energy recovering

industry. In addition, there will be a guaranteed supply of waste tyres due to the

possible tyre production competitiveness.

State government

Steady economic growth will be experienced due to the increase in waste tyre business

competitiveness, job creation and capacity building.

Manufacturing or retail sectors

The ban on waste tyre land filling will promote the production of alternative fuel for

some sectors, such as agriculture.

90

Fig. 4.5 A pile of steel wires from burnt tyres

Fig. 4.6 A young steel wire seller from Soweto, Gauteng.

91

Waste tyres have the potential to be utilised as energy source as well an alternative petroleum

fuel source. Pyrolysis and gasification are some of the technologies which can be employed

to achieve this objective. The waste tyre recycling industry has proven to be fairly ineffective

in South Africa with only a 4% waste tyre recycling rate in 2011 and lower in the previous

years[7]. Recycling of waste tyres has the potential to address both environmental and energy

challenges as well as contributing to economic growth. In addition, the South African

government recognizes the conversion of waste to energy in its plans and future

strategies[27]. A waste tyre management plan such as the gazetted REDISA Plan, which is

awaiting implementation, is expected to address the problem at national level.

Progress has been made with a range of energy efficiency initiatives such as the South

African National Energy Development Institute (SANEDI); a Schedule 3A state owned entity

that was established as a successor to the South African National Energy Research Institute

(SANERI) and the National Energy Efficiency Agency (NEEA). The key function of

SANEDI is to direct, monitor and conduct applied energy research and development,

demonstration and deployment as well to undertake specific measures to promote the use of

green energy and energy efficiency in South Africa. SANEDI is involved in numerous

institutional research projects and programmes in green energy engineering. These can

promote South Africa‟s development, increase human capacity and eventually lead to

commercialization of the intellectual property. Other projects include the Industrial Energy

Efficiency Improvement Project, South Africa; the Energy Efficiency Target Monitoring

System (EETMS) and the South Africa Germany Energy Project (SAGEN).

4.2.5 Tyre Derived Fuel (TDF) applications

Scrap tyre markets are mature and stable in most developed countries such as the USA. Scrap

tyres are recognized as abundant valuable resources and are used in a number of applications,

including tyre derived fuels or products. Generally, in South Africa the market for tyre-

derived products is much larger than the market for liquid products, such as oil. Tyre derived

fuel has a higher heating value than coal and wood, Table 4.4[109].

92

Table 4.4

Calorific values of a number of common fuels

Fuel Calorific Value (MJ/kg)

gas 84.7

diesel oil 45.5

scrap tyres 32.5

coal 30.2

coke 26.7

wood 12.4

The following are the existing TDF applications that have been successfully implemented

elsewhere, and these can be used as bench marks for the South African scenario in dealing

with the waste tyre problem.

a) Cement Manufacturing

Tyres can be alternatively utilized in cement kilns and power plants. The use of scrap tyres in

cement kilns is increasing and is by far the leading thermal technology used for scrap tyres

management[110]. When the complete ban of tyres to landfill came into effect in 2006 for

most European countries, the use of tyres in cement kilns increased and this was further

strengthened by the increase in fossil fuel prices[111]. Most of the leading cement companies

such as Lafarge, Holcim, Cimpor, Heidelberg, Taiheiyo, Italcementi, Aalborg Portland, and

Castle Cement have plants around the world that are currently co-combusting tyres[111].

Lafarge Cement‟s overall manufacturing capacity is in excess of 6 million tonnes per annum

in the UK with 40% accounting for their domestic market in 2003[112]. Scrap tyres along

with other alternative fuels, such as recycled liquid fuels, form the mainstay of Lafarge

Cement‟s UK strategy to increase its waste tyre utilisation as an alternative source of energy

from less than 3% in 1999 to an excess of 20% in 2006[113].

Local cement companies such as Pretoria Portland Cement (PPC) are also in the investigation

stages of incorporating waste tyres as part of their fuel source. This proposed project is

however still in the initial stages with full scale implementation expected early 2014[114].

Cement manufacturing companies use whole tyres and TDF to supplement their primary fuel

for firing cement kilns. Several characteristics make scrap tyres, either whole or shredded, an

excellent fuel for the cement kiln. The very high temperatures and long fuel residence time in

the kiln allow complete combustion of the tyres, without the production of odours or

emissions during the combustion process. The ash forms part of the final product and hence

93

there is no waste. The steel component replaces the iron required in cement manufacturing.

The use of waste tyres in cement kilns results in higher production rates, lower fuel costs and

improved environmental quality, considered as advantages, while the only disadvantage is the

possible emission of carbon dioxide (CO2)[111].

b) Pulp and Paper Industry

The pulp and paper industry uses tyre-derived fuel as a supplement to wood waste, the

primary fuel used in pulp mill boilers. The technology has been in continuous use in the

United States since the early 1980s. The heating value of the wood waste fuel ranges from

about 8,334.5 to 9,495 kJ/kg on a dry basis. Tyres facilitate uniform boiler combustion, and

help overcome some of the operating problems caused by fuels with low heat content,

variable heat content and high moisture content. The consistent heating value, low moisture

content of TDF and its low cost in comparison to other supplemental fuels make TDF an

attractive fuel in the pulp and paper industry. One of the key advantages for using TDF in the

pulp and paper industry is that it increases combustion efficiency. It also lowers energy costs

and improves product quality[115].

c) Industrial Boilers

In industrial boiler application, combustion of TDF generates energy in the form of steam

and/or electricity, replacing other fuels such as coal. This also reduces pollution. TDF

combusted industrial boilers emit fewer oxides of sulphur and nitrogen compared to coal.

TDF operated systems offer higher heating value, lower emissions, competitive cost, and

ability to create stable operating conditions in the boilers. This makes the use of TDF

attractive in power generation. However, TDF is not compatible with all boilers as clumping

and clogging can also occur. Also, if the metal in waste tyres is not recovered, it causes

disposal challenges.

4.2.6 Waste tyre pyrolysis markets

Over the last two decades there has been a growing interest in using tyre-derived fuels.

Initially this interest was driven by concerns for potential shortages of crude oil, but in recent

years the ecological advantages of alternative fuels have become an even more important

factor. Tyre derived-oil can be easily transported and stored. However, the properties of

waste tyre-oil also result in several significant problems during its use as a fuel in standard

94

equipment such as boilers, engines and gas turbines. Poor volatility, high viscosity, coking,

and corrosiveness are probably the most challenging and have so far limited the range of its

applications[116].

Tyre Derived Oil Applications

Waste tyre pyrolysis produces gaseous products such as synthesis gas. This gas can be used

for fuel, electricity, and chemicals. When later condensed, the gas generates an oil-based

liquid containing up to 30-50 % of the tyre feedstock[117]. Outlined below are some of the

pyrolysis gas applications:

Chemical feed stock: Pyrolysis of waste tyres produces gases such as benzene; toluene and

xylenes which are very important chemicals. They are used as primary feed stocks to produce

plastics, resins, fibres, surfactants, dyestuffs and pharmaceuticals, and long-chained alkyl

benzenes that can be used as surfactants. Xylenes are important industrial chemicals used to

produce plasticizers and dyes; m- and p-xylene derivatives are used on polyesteric resins and

in the fibre industry. Toluene has a wide range of applications but is mostly used for

pesticides, dyestuffs, surfactants and solvents production[61], such as limonene[2, 68, 72].

Industrial and commercial: Waste tyre derived liquids have properties resembling petroleum

fractions. The oil produced by pyrolysis technology is the fuel oil that is widely used for

industrial and commercial purposes such as industrial furnaces, foundries and boilers in

power plants, due to their higher calorific value, low ash, residual carbon and sulphur content.

[116]. The oil can be a substitute for diesel, heavy fuel oil, light fuel oil or natural gas in

industrial, commercial and residential boilers. Furnaces and boilers are devices commonly

used for heat and power generation. They are usually less efficient than engines and turbines

but they can operate with a great variety of fuels ranging from natural gas and petroleum

distillates to sawdust, coal/water slurries and oil seems. For a fuel to be suitable for boiler

application, it should have consistent characteristics, environmentally acceptable and produce

limited emissions.

Use as automobile fuel: High viscosity, delayed ignition time, lower heating value,

corrosion and solid content hinder the utilization of pyrolysis oil as automobile fuel. Work

has been done on the improvement of pyrolysis oil for use in modern combustion devices. In

this regard it has been found that pyrolytic oils require preliminary treatments such as

95

decanting, centrifugation, filtration, desulphurization, and hydrotreating before application as

fuels [6, 10, 68, 118, 119].

Bi-fuelling or blending: Viscosity and sulphur content of crude TDO influence engine

performance and emissions, hence affect the use of tyre derived pyrolysis oil as a blending

fuel. The high viscosity of the fuel leads to problems over time such as carbon deposit. The

high carbon residue content and high viscosity arise from large molecular mass and chemical

structure of the oil. The high carbon residue is responsible for heavy smoke emissions. The

treated pyrolytic oil could be used alone or blended with other fuels such as CIMAK-B10

diesel fuel, which is basically 10% biofuel, in this case 10% pyrolysis oil, and 90% petroleum

fuel[120]. The addition of pyrolytic oil to this kind of diesel fuel reduces the viscosity of the

resulting blend. Consequently, the atomization will be improved, ensuring a complete

burnout of the fuel. Based on its fuel properties, tyre-derived pyrolytic oil can be considered a

valuable component for use with conventional fuels.

The South African Market

The waste tyre pyrolysis process is still a relatively new concept in South Africa. It has not

been fully explored regardless of the fact that several attempts have been made to operate

profitable plants which adhere to environmental laws. Such attempts include the Pretoria

based pyrolysis plant (Innovative Recycling (Pty) Ltd) which used to process 25 tonnes of

waste tyres daily. The company capitalized on the opportunity of using excess waste tyres by

erecting a waste rubber and plastic conversion to fuel plants. The plant ceased operation

because of its failure to adhere to environmental regulations and laws.

Currently, there is an operating pyrolysis plant in Rosslyn, Pretoria. This plant has been in

operation on and off since March 2012. The plant processes 10 tonnes of waste tyre at a batch

operation of 11 hours per day. It produces 40% pyrolysis oil, 30-35% carbon black, 15% steel

cords and 10% uncondensed gases. The oil is sold as crude for industrial applications. The

pyrolysis oil specifications and properties should be measured against local and international

oil standards before application. For comparison purposes, two samples were analysed and

compared with diesel standards. The first sample was obtained from the Rosslyn pyrolysis

plant and the second from Pace Oil (oil refining company). The two samples were analysed in

two South African Bureau of Standards (SABS) approved laboratories and the results are

shown in Table 4.5.

96

Table 4.5

Pyrolysis oil specifications

Test Description Test method Specification [Milvinetix] [Pace oil]

Density @20oC, kg/l ASTM D4052 0.800 Min 0.895 0.8772

Viscosity @40oC, cSt ASTM D445 2.2-5.3 2.868 2.1

Flash point, oC ASTM D93 55 min ˂25 26

Water Content, ppm ASTM 6304 500 max 673 600

Sulphur content, ppm ASTM D4294 500 max 8100 12400

Total Contamination number,mg/kg IP 440 24 max 31 38.6

Distillation oC: 90% Recovery, oC ASTM D 86 362 max 378.8 360

Micro Carbon Residue ASTM D4530 0.2 max 4.5 2

Cetane Index ASTM D4737 51 min 32.01 34.2

The pyrolysis characteristics in Table 4.6 conform to the South African National Standards

(SANS) specification (SANS 342:2006)[121] for density and viscosity. In addition, the Pace

oil sample was within the distillation recovery SANS specification. This is important as high

boiling components favours the formation of solid combustion deposits and hydrocarbon

mixtures producing potentially explosive vapour[122]. The oil shown in Table 4.6 has a low

flash point requiring specific storage to meet insurance and fire prevention requirements.

Additives and blending can increase the flash point and also reduce the water content[123].

The two oils contained excess contaminants although there was little metallic contamination.

The oils are out of specification with regard to the octane index and micro carbon residue

limiting their application. The Milvinetix oil is not further treated for economic reasons[91,

124] thus it is sold in its crude form. When comparing the 2 samples, it is evident that both

samples do not meet the SANS standards for majority of the tests conducted, however, the

Pace Oil sample seems to be within the distillation: recovery limit.

Pyrolysis oil small scale studies:

References[125] focused on the removal of sulphur compounds using acidic and basic

treatments at varying concentration as well as filtration. Crude pyrolysis oil was distilled at

varying temperatures and the results are shown in Table 4.6. Fig. 4.7 shows that the

temperature range 150-200oC is the most satisfactory for the distillation of pyrolysis oil as the

distillation temperature affects the desulphurization process. Table 4.6 shows the properties

of distilled pyrolysis oil at 150-200oC. Acid treatment of the distilled oil produced better

oxidative desulphurization (ODS) compared to base treatment, Fig 4.7, reducing the sulphur

concentration from 9106 to 4807ppm with 10 (v/v%) H2SO4.

97

Table 4.6

Proximate analysis of crude and distilled pyrolysis

Parameter

Crude Pyrolysis oil Distilled Pyrolysis oil

(150-200oC)

Density @ 20oC (Kg/L) 0.9265 0.835

Viscosity @ 40oC (cSt) 10 0.9

Sulphur (ppm) 9106 7054

Flash Point (oC) 94 26

Total Contamination (mg/kg) 143 4.3

Fig 4.7 Comparison of the sulphur content with varying temperature ranges.

A carbon black sample was also collected from the Pretoria Pyrolysis plant and analysed. The

sample has a high calorific value making it possible for fuel application. However, the sample

did not conform to the ASTM standards for ash and volatile matter content, Table 4.7. This

means that the sample cannot be considered for industrial use in its virgin form after

pyrolyzing waste tyres. Hence further purification of the carbon black is required to improve

marketing and standardisation.

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000

0150-200

150-200200-250

200-250250-300

Before ODS

ODS H2S04

ODS NaOH

Sieved ODS

NaOH Sieved ODS

H2SO4

ODS NaOH

Su

lph

ur(

pp

m)

Temperature Range(Degrees Celcius)

98

Table 4.7

Pyrolysis carbon black specifications

Test Description Test method (SA) [Milvinetix] ASTM Test

method [126]

Calorific Value SANS 1928:2009 31.18%

Moisture Content

SANS

15325:2007 1.30%

Ash content ISO 1171:2010 14.50% 0.5 % Max

Volatile Matter Content ISO 582:2010 24.30% 0.3% Max

Fixed Carbon By difference 59.90%

Total Sulphur ASTM 4239:2010 2.61%

99

CHAPTER 5

WASTE TYRE PYROLYSIS PLANT MODEL

100

This study assesses the feasibility of constructing and operating a batch pyrolysis plant in

Gauteng. The study focuses on the production of alternative fuels and other high value

pyrolysis products. With the support of the REDISA plan, waste tyres will be collected within

the vicinity of Gauteng and transported to the waste tyre treatment plant.

5.1 Pyrolysis

Waste tyres will be delivered to a permitted waste tyre treatment facility where the tyres are

to be weighed then introduced to the pyrolysis system after shredding. The batch process

takes place in a reactor chamber with feedstock of 7 tonnes per day and average residence

time of 8 hours. An inert gas, such as nitrogen, is used to purge the excess oxygen from the

system. To a large extent, reactor temperature determines the yield of solid, gas, and liquid

pyrolysis products thus; operation at 550oC and ambient pressure allows the production of

45% oil; 5% pyrolysis gas; 35% carbon black and 15% steel wires. Table 5.1 gives the

summary of the effect of operating temperature on product yield [127]

Table 5. 1

Effect of temperature on yield

Operating Temperature Operating Pressure Production Variation

42% Oil

500°C Ambient 52% Solid

6% Gas

50% Oil

600°C Ambient 40% Solid

10% Gas

47% Oil

700°C Ambient 38% Solid

15% Gas

40% Oil

800°C Ambient 29% Solid

31% Gas

5.1.1 Pyrolysis end products

During the course of the pyrolysis process, pyrolytic gas is produced then cooled and further

condensed to form pyrolytic oil. This oil is classified as No. 6 oil which is a thick, syrupy

heavy crude oil and has an acrid smell. To increase the economics of this product, a

distillation step is integrated into the process. This treatment step improves the quality of the

oil, thus increasing the application. The crude pyrolysis oil is distilled to form light tyre

101

derived distillate fuel and residual fuel oil fractions. The residual oil is blended with diesel

while the distillate fraction is utilized in agricultural vehicles. The uncondensed gases are

recycled back to the system for use as fuel to sustain the process. The emissions from the

reactor burners are chemically treated using a gas absorption process.

The solid fractions consist of a mixture of carbon black and steel wires. A magnetic

separation is used to remove ferrous metals to isolate the two components. The carbon black

is further milled in order to obtain different grades and fractions of the char. The following

fractions can be obtained: N220 (24-33nm) used in rubber and rubber products; N770 (70-96

nm) used in paints and pigments; N990 (250-350 nm) used as activated carbon and the

residue fraction can be used for briquettes. The steel component is sold to steel manufactures

or dealers.

5.1.2 Utilities

The process requires process water for cooling (heat exchangers and cooling tower),

condensation as well as carbon black wet grinding. Approximately 8000 litres of water will

be used monthly in the plant. The energy requirement for the plant is 528.58 KW, Table 5.2.

This power is supplied to components such as the tyre shredder, heaters, pumps, control

systems as well as large mechanical and heating equipment. Sodium Hydroxide (NaOH) is

used as a scrubbing reagent at a cost of R7.55 kg per bag. The nitrogen required for the

pyrolysis reactor is estimated to be R687, 79 per 13kg cylinder.

Table 5.2

Total plant energy requirement

Energy type Amount

Heating 250, 41 kW

Mechanical 327, 58 kW

Cooling 129,59 kW

Available fuel energy 179 kW

Energy efficiency 0,75

Total supply 528,58 kW

5.2 Discussions

The economic model is based on a 12 year pyrolysis plant life span consisting of 4 rotating

shifts with 3 operating daily. The treatment facility operates as a batch process 329 days per

year, the remaining days are utilized for maintenance. The available plant capacity is 2546

ton/year. With shutdown time of 36 days/year the allowable plant capacity becomes 2291

102

ton/year shown in Table 5.3. The initial process input assumptions for the project are given in

Table 5.4. A basis of 7 tonnes/day of treated tyres will initially be used; however expansion

of up to 10 tonnes/day is catered for in the plant design. The basis is lower than that of the

Pretoria based pyrolysis plant, 10 tonnes per day; this is due to an already established market

for their end products. Therefore, with growth and standardization of the proposed pyrolysis

end products plant expansion is viable.

Table 5.3

Pyrolysis plant operational assumptions

units

Weight of rim-less tyre

7,75 Kg

Single tyre gate fee

13 R/tyre

Operating hours

328,5 Days/yr

Plant shut down time

36,5 Days/yr

operating shifts

3 per day

Loading cycles 3 Per shift

Table 5.4

Process Input assumptions

Variable Unit Figure

Tyre disposal fee R/day R 1 950,00

power consumption R/Annum R 218 437,27

Water consumption R/Annum R 61 257,60

Treated tyres ton/day 6,98

Annual working hours hr/yr 8760

Down time hr/yr 876

Plant operating time hr/yr 7884

Actual plant capacity ton/hr 2291,2875

Available plant capacity ton/hr 2545,875

Exchange rate R/$ 10,84

R/£ 14

Estimated project period Yrs 12

Actual annual production ton/yr 2291,288

Process Input costs

Power R/kWh 1,258

water R/L 0,02127

Telephone Line R/Annum R 36 000,00

NaOH (scrubber reagent) R/ton R 7 550,00

Nitrogen R/3 kg R 687,79

103

Four income streams will be the core revenues for the project. A tyre gate fee of R13.00 per

tyre is collected. Distilled pyrolysis oil is sold at R9.50 taking into account the 2014 fuel

prices with fluctuation allowance. The oil is mainly sold to agricultural businesses. An

overall revenue of R 310 354, 89 per annum of variable carbon black grades N220, N770,

N990 and briquettes is collected. Lastly, the residual steel wires are sold to appropriate

dealers at a rate of R 2 500, 00 per tonne. The 5% uncondensed gasses are recycled back into

the process. The mass and energy balance with 90% plant capacity for the first 4 years is

given in Table 5.5.

Table 5. 5

Mass and energy balance

Year 0 Year 1 Year 2 Year 3 Year 4

Plant capital factor

90,00% 90,00% 90,00% 90,00% 90,00%

Balances

1. Process inputs

Tyres (Ton/yr)

2291,29 2291,29 2291,29 2291,29 2291,29

Water (m3/yr)

2628 2628 2628 2628 2628

Electricity (KW/yr)

218437,27 218437,27 218437,27 218437,27 218437,27

NaOH (ton/yr)

8212,5 8212,5 8212,5 8212,5 8212,5

nitrogen (l/yr)

4270,5 4270,5 4270,5 4270,5 4270,5

2. Process outputs Actual

output

Tyre derived fuel (ton/yr) 45% 1031,07938 1031,079 1031,0794 1031,0794 1031,079

Carbon black, Char (ton/yr) 35% 801,950625 801,951 801,95063 801,95063 801,9506

Steel cords (ton/yr) 15% 343,693125 343,693 343,69313 343,69313 343,6931

Uncondensed Gas (m3/yr) 5% 114,564375 114,564 114,56438 114,56438 114,5644

2291,2875 2291,2875 2291,2875 2291,2875 2291,288

The order of magnitude estimate method was used for major equipment costing. Using

project evaluation methods, represented by equations 5.1 to 5.8, it was found out that the

project is worth investing into with a projected payback period of approximately 5 years, Fig

5.1. The project requires a capital incentive of R 10, 173 075.00 during year 0, this cost

includes the cost of all major equipment, plant assessment costs, building and structure,

engineering and construction as well as other costs such as contingency fees and office

utilities, Table 5.6. The required capex is solely funded by a financial institution with a pay

period of 4 years based on an annual interest rate of 10%. A tax rate and vat rate of 29% and

14% respectively are taken into account for the annual revenues. An annual straight line

depreciation rate is applied over the12 year plant lifespan, Table 5.6.

104

………. (5.1)

………. (5.2)

…………………………………………….....

(5.3)

………………………. (5.4)

. (5.5)

……………………………………………….

(5.6)

………………………………. (5.7)

∑

.……… (5.8)

Fig 5.1 shows a general increasing trend for all the plotted variables (project life, operating

costs, labour costs, net profit after tax and annual revenue) from year 0 to year 12. A steady

increase in the net profit after tax is projected predominantly around year 5; this is due to the

business ending their capex loan repayment period after year 4. This results in the project

accumulating higher revenues annually from year 4 onwards. In addition, a significant gap

between the revenue and annual costs (labour and operating costs) is visible and show a trend

of not intersecting anywhere during the project life, thus indicating a profitable project life.

The plant only breakeven after 5 years due to the high capital investment accompanied by an

annual 10% interest on loan repayment. However due to the availability of raw material at no

cost and the sale of high end products the plant is seen to be highly profitable from there on.

Fig 5.1 also shows stabilisation in the accumulated annual revenue and production costs

towards the end of the project, this is expected as a high increase in revenue is realised from

year 6 onwards.

The net present value (NPV) is also used to determine whether the project is worth investing

into in terms of profit yield and breakeven period. Fig 5.2 shows that the project is worth

investing in due to the positive net present value, this is also depicted in Table 5.7. In

addition, the NPV curve also gives an indication of the projected plant life which agrees very

well with the plotted plant life curve in Fig 5.1. The return of assets (ROA) is also in

105

agreement with the NPV. According to [128] 20 to 30 % of the return of investment (ROI)

can be used as a rough guide for evaluating small projects and the higher a project's return the

more attractive it is. The ROR, defined as the performance of the capital invested, as well as

the ROI are in the 30% range which is in strong agreement with literature.

Fig 5.1 Projected plant life, costs and revenues.

-8000000

-3000000

2000000

7000000

12000000

17000000

22000000

27000000

32000000

37000000

0 2 4 6 8 10 12 14

Val

ue

(R)

Year Project life Operating costs

Revenue Labour costs

Net operating profit after taxes (NOPAT)

106

Fig 5.2 Net present value and depreciation rate

-0,7

-0,6

-0,5

-0,4

-0,3

-0,2

-0,1

0

0,1

0,2

0,3

-R 8000 000,00

-R 6000 000,00

-R 4000 000,00

-R 2000 000,00

R 0,00

R 2000 000,00

R 4000 000,00

R 6000 000,00

0 2 4 6 8 10 12 14

Depreciation Net present value (NPV) Depreciation % ROA(return of Assets)

Table 5.6

Waste tyre pyrolysis project capex

Project Costing

ITEM

No Rental

R 180 000,00

1 PLANT EQUIPMENT COST

DESCRIPTION QUANTITY COST COMMENTS

1,1 Pre-Pyrolysis

1.1.1 Magnetic separator 1 R 56 460 1,1 kW motor, 550kg

1.1.2 Tyre shredding 1 R 211 380 60-80 tyres per hour, 15hp 1.1.3 weighing system 1 R 9 861 2mx1.5m SABS approved. With read out screen

R 277 701

1,2 Pyrolysis

1.2.1 Reaction Chamber 1 R 120 046 D1.4m, L6m, 15KW, 380V, 8-10t/day, Q245/Q345 CSPV

1.2.2 Heat exchanger 2 R 355 525 1:27,5 m2, 177 tubes 20mm o.d, 2.44m L; 2:20,5m2,134 tubes 20mm o.d,2.44m L 1.2.3 condenser 1 R 243 952 38,5 m2, 166 tubes @ 20mm o.d and 3.66m L 1.2.4 Storage tank 2 R 131 000 23000l

1.2.5 cooling tower 1 R 1 125 640 Stainless steel/galvanized steel

1.2.6 pumps 4 R 109 980 carbon steel 1.2.7 Interconnecting pipes and valves R 298 202 carbon steel

R 2 384 345

1,3 Post -Treatment 1.3.1 Distillation column 1 R 291 428 Carbon steel/stainless steel, CC, D=2m, H=4m

1.3.2 Micro ball mill 1 R 839 878 Stainless steel, inc ball liners, 0,019m- 48 mesh, closed circuit with classifier. 0,3 kg/s

1.3.3 Gas scrubber 1 R 685 844 Carbon steel/stainless steel, D=1,5m, H=4m

R 1 817 150

Total equipment R 4 479 196

1,4 Engineering& other services

1.4.1 Plant assessment costs R 604 899

Land and site evaluation

Preliminary plant draughting and layout

Safety, risk and environmental assessment

1.4.2 Building and structure R 1 209 799

Process Building

Maintenance shops

Offices 1.4.4 Engineering and construction

Civil and Construction design R 725 879

108

Fencing

Safety

Structural design and Construction R 967 839 Electrical and controls systems design R 698 879

Project Management R 338 744

1.4.5 Communication R 241 960

1.4.6 Other additional costs R 725 879 Contingencies

Critical standby equipment

Contractor fees

Office equipment and stationary R 5 513 879

TOTAL PLANT COST

R 10 173 075

TOTAL CAPITAL REQUIREMENT R 10 173 075,35

Table 5.7

Plant evaluation calculations

Year Net annual profit Total assets Depreciation Depreciation % ROA ROR ROI NPV

0 0 R 10 671 195,97 R 4 479 195,97 0 0 33,50% 30% 0

1 R -6 428 301,18 R 10 229 768,90 R 689 107,07 0,15 -0,63

R -5 739 554,63

2 R -5 207 945,78 R 16 552 941,81 R 631 681,48 0,14 -0,31

R -4 151 742,49

3 R -3 411 720,79 R 23 635 911,07 R 574 255,89 0,13 -0,14

R -2 428 395,47

4 R -1 232 174,29 R 30 769 420,60 R 516 830,30 0,1 -0,04

R -783 069,04

5 R 1 104 176,82 R 37 967 241,03 R 459 404,71 0,09 0,029

R 626 539,58

6 R 3 717 308,01 R 45 681 920,56 R 401 979,13 0,09 0,08

R 1 883 303,92

7 R 6 818 236,36 R 54 803 826,02 R 344 553,54 0,08 0,12

R 3 084 223,87

8 R 8 987 602,25 R 64 844 604,83 R 287 127,95 0,06 0,14

R 3 629 941,81

9 R 11 557 771,17 R 64 614 902,47 R 229 702,36 0,05 0,18

R 4 167 848,15

10 R 12 684 135,20 R 75 803 323,13 R 172 276,77 0,04 0,17

R 4 083 952,06

11 R 14 340 983,54 R 87 730 811,23 R 114 851,18 0,03 0,16

R 4 122 690,08

12 R 16 223 159,98 R 100 202 235,43 R 57 425,59 0,01 0,16

R 4 164 081,09

R 4 479 195,97

Sum R 12 659 818,94

R 2 486 743,58

5.3 Environmental Impact Assessment

This section presents an evaluation of the environmental impacts of waste tyre pyrolysis

including potential mitigation measures. These impacts include air emissions, liquid wastes,

and solid residues. Generally, the environmental impacts are similar in all three PGL

technologies. When compared to operations that utilize combustion of waste tyres, it is

generally accepted that PGL technologies yield equal or lower environmental risks in most

cases. However, the information available is limited, due to the small number of full-scale

PGL facilities [61]. Exhaust gas clean-up of PGL processes is less compared to incineration,

however, proper design and operation of the process and emissions control systems are

necessary to ensure that all health and safety requirements are met. The control of air

emissions is made less costly and complex for PGL processes compared to incineration

because (a) subsequent combustion of low-molecular-weight gases from pyrolysis and

gasification processes is much cleaner air compared to the combustion of raw feed stocks (b)

pyrolysis and gasification processes use zero or minimum air or oxygen. (c) Pyrolytic gases

are typically in a reducing environment, and can be treated or utilized unlike the fully

combusted (oxidative) exhaust.

5.3.1 Air Emissions

Air emissions may be the greatest environmental concern in PGL operations using waste

tyres. The gases from pyrolysis and gasification processes (and subsequent combustion

processes, if applicable) can contain a variety of air pollutants that must be controlled prior to

discharge into the ambient air. These include particulate matter (PM), oxides of nitrogen

(NOx), oxides of sulphur (SOx), dioxins and furans, hydrocarbon (HC) gases, metals, carbon

dioxide (CO2), and carbon monoxide (CO) [61]. There are many strategies available for

controlling emissions from waste tyre thermal processes depending on the process

requirements and scale of each individual facility.

There are a number of different emission control strategies that can be applied in PGL

processes. An example of a mid-process air pollution control system is the Thermoselect®

process, a high-temperature conversion technology. The company currently has four facilities

in commercial operation worldwide, with three others under construction [49]. The

Thermoselect® process is capable of processing different waste streams, including tyres. The

Thermoselect® process uses gasification for primary processing, but can also be applicable to

high temperature pyrolysis. After completion of the gasification/ pyrolysis stage, the

110

synthesis gas exits the reaction chamber and flows into a water jet quench where it is

instantaneously cooled to below 95o C. The rapid cooling prevents the formation of dioxins

and furans by dramatically reducing the residence time of the synthesis gas at high

temperature. Entrained particles (such as elemental carbon and mineral dusts), heavy metals,

chlorine (in the form of hydrochloric acid [HCl]), and fluorine (in the form of HF) are also

separated out in the quench. The quench water is maintained at a pH of 2 to ensure that heavy

metals are dissolved as chlorinated and fluorinated species, so that they are washed out of the

crude synthesis gas.

Following the quench process, the synthesis gas flows into a demister and then into alkaline

scrubbers, where the remaining particulates and HCl/HF droplets are removed. Then the gas

passes through a desulfurization scrubber for the removal of hydrogen sulphide (H2S) by

direct conversion into elemental sulphur. The scrubber is a packed bed that is sprayed with

scrubbing liquor consisting of water and a dissolved Fe-III chelate that oxidizes the H2S to

elemental sulphur and water. Finally, the gas is dried in a counter current packed bed

scrubber using tri-ethylene glycol liquor. The fully cleaned synthesis gas can then be

conveyed to engines, boilers, or turbines for electricity production. Alternatively, the gas can

be converted to higher molecular weight fuels such as diesel fuel. Other control systems such

as the Exxon thermal de-NOx system for NOx emissions, fabric filters for particulate matter

and wet scrubbers for SOx emissions can be utilized.

5.3.2 Liquid Residues

The primary liquid products from tyre PGL processes are pyrolysis oils and any residual

scrubber solutions from the air pollution control equipment. Pyrolysis oils from tyres and

other products are complex mixtures of hydrocarbons. The liquid fraction can contain a range

of species including acids, alcohols, aldehydes, aromatics, ketones, esters, heterocyclic

derivatives, and phenols, along with varying amounts of water [115]. These oils typically

contain a number of substances that can be considered toxic, but can be handled safely using

typical industrial practices. They also represent an intermediate product that is not disposed

of, but can be used either via combustion for energy production or for the production of other

chemicals after upgrading. Residual products from the gas cleaning and water recovery

processes can be handled using well-established procedures. These residual products include

industrial-grade salts and a separate precipitate containing the heavy metals from the

feedstock stream. In some cases, this precipitate may be rich enough in zinc and lead to

warrant recovery in a smelter operation [49].

111

5.3.3 Solid Waste Residues

The solid residue remaining from PGL processes is typically an inorganic ash or char. The

inorganic ash is the residue from the 3 to 5% of inorganic material in the tyre that cannot be

converted to energy or products through PGL [49]. The ash contains non-volatile trace metals

that are more concentrated in the ash than in the feedstock, but with proper management can

be treated and disposed of in a manner that does not pose an environmental threat. In some

cases, metals can be recycled from the ash. The leach-ability of the ash is used to indicate

whether the ash is classified as a hazardous or non-hazardous waste. Char contains carbon

black; sulphur; zinc oxide; clay fillers; calcium and magnesium carbonates and silicates, all

of which produce PM10 emissions. Operations such as screening, grinding and processing

cause PM10 emissions and could be controlled with dust collectors and a baghouse filters. If

markets for the char cannot be developed, the char becomes a major solid waste problem. In

addition, to landfill disposal, plastic bags should be used and must be shipped and disposed of

in steel drums to prevent additional fugitive emissions during transportation and disposal

[116].

5.4 Pyrolysis plant comparison study

This section will focus on the comparison between the modelled pyrolysis plant and the

Pretoria based plant (Milvinetix) in term of operation, end product, financial requirements

and plant viability. The following report was obtained from the 2013 Milvinetix business plan

[129] .

5.4.1 Production

The business plan and financial models have been modelled around 90% efficiency in each

process. Tonnage tyre processing per month is expected to be 10 ton/day x 26 working days,

thus resulting in 260 tonnes treated per month. Oil production per month (40 % yield on total

tonnage input, 104 litres per month), steel production per month (10 % yield per total tonnage

input, 26 tonnes per month) and carbon Black production per month (30 % yield on total

input 156 tonnes per month).

5.4.2 End products

According to the Milvinetix business plan, the business model will allow through correct

processing and proper filtration of tyre derived oil production of industrial diesel, furnace oil,

bunker fuel, gas. The carbon black will be the main component in the manufacturing of

charcoal briquettes as an alternative heat source to wood. Industrial diesel, furnace oil and

112

bunker fuel is mainly used in: Noxious industries: mining, farming and generators, in

addition, the shipping industry market related price would be R 6.00/litre. The gas created by

the pyrolysis process, forms part of the heating process to generate heat for the pyrolysis

process, hence the process becomes self-sustaining and prevents toxic gasses being released

into the atmosphere.

5.4.3 Financial Requirements

Below are two options depending on requirements and financial options open to the potential

purchaser of a tyre recycling plant. The price includes all machinery, machinery installation,

training and management of the two options.

a) Option 1 is a single reactor plant, Table 5.8.

b) Option 2 is a double reactor plant, Table 5.9.

Table 5.8

Business model option 1

Description Amount

Equipment and machinery for Import

Shipping Cost

Equipment & Machinery Local

Site Preparation

Technical and Installation support

Environmental & Licensing

Factory & Loading Inspection plus transport

Health & Safety Plus OHSA accreditation

IT & Electrical works

Excludes working Capital as this is case sensitive (APROXIMATLY) R 750.000.00

Total Including vat R 11 190 000.00

113

Table 5.9

Business model option 2

Description Amount

Equipment and machinery for Import

Shipping Cost

Equipment & Machinery Local

Site Preparation

Technical and Installation support

Environmental & Licensing

Factory & Loading Inspection plus transport

Health & Safety Plus OHSA accreditation

IT & Electrical works

Excludes working Capital as this is case sensitive (APROXIMATLY) R 1.500.000.00

Total including Vat R 24 380 000.00

According to their financial model, loan repayment will end after 4 years, thus resulting in

the business to break-even at that time. This compares very well with the proposed model in

this work; the model suggests a break-even point just after the 4th

year, Fig. 5.1 and 5.2. In

addition, the required investment needed for each project compares very well, R 10 173 075,

35 and R 11 190 000, 00 are required for the Milvinetix and proposed business model

respectively. Thus, this proves that the model used for this work is applicable in the

construction and commissioning of a new pyrolysis plant in the Gauteng region.

114

CHAPTER 6

CONCLUSION AND RECOMMENDATIONS

115

Based on the pyrolysis plant business model and all relevant data collected through literature

analysis, questionnaires, site visits as well as telephonic and personal interviews the

following conclusions are made:

Waste tyre pyrolysis is a potential waste tyre remedial technology and developing

countries like South Africa should invest in such waste treatment facilities.

Waste tyre pyrolysis shows a profitable business model that is suitable for the South

African environment.

The waste tyre plant business model shows a sound payback period of less than 5 years

and plant life of 12 years is projected.

A further treatment step is required to increase the value of the products.

The final value added products may have the following applications, the oil can be

used in agricultural vehicles or blended to a diesel feed stock, the carbon black can be

reduced to different grades for applications in the rubber, paint, pigments and

briquetting industry and the residual steel wires are sold to local steel dealers.

For a successful business model, a stable and sustainable product market should exist.

It is recommended that a continuation of this work should be done with the costing based on

an existing plant. Other cost estimation models such as the study estimate and preliminary

estimate methods should be used to obtain conclusive results.

116

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APPENDICES

Appendix A

Equipment costing equations

(All equipment) (5.1)

(Heat exchangers) (5.2)

(5.3)

(5.4)

(5.5)

Nomenclature:

126

Fig. A.1 Temperature correction factor: two shell passes; four or multiples of four tube passes

Table A.1

Heat exchanger design, material and pressure correction factor

Material Shell/ Tube Surface Area, ft

2

up to 100 100-500 500-1000 1000-5000 5000-10000

CS/CSa 1.00 1.00 1.00 1.00 1.00

SS/SS 2.50 3.10 3.26 3.45 4.50

CS/SS 1.54 7.78 2.25 2.81 3.52

a. Carbon steel shell/ Carbon steel tubes

127

Table A.2

Temperature, pressure and material of construction correction factor

Design Pressure, atm Correction Factor

0.005 1.3

0.014 1.2

0.048 1.1

0.54 to 6.8 1.0

48 1.1

204 1.2

408 1.3

Design Temp,

oC Correction factor

-80 1.3

0 1.0

100 1.05

600 1.1

5000 1.2

1000 1.4

Material of construction Correction factor

Carbon steel (mild) 1.0

Bronze 1.05

Carbon/ molybdenum 1.065

Steel

Aluminium 1.075

Cast steel 1.11

Stainless steel 1.28 to 1.5

Worthite alloy 1.41

Hastelloy C alloy 1.54

Monel alloy 1.65

Titanium 2.0

Table A.3

Equipment cost data 1

Equipment Size Capacity units FOB Cost4, k$ January [1990] Correlation range Capacity exponent

Agitators 3 hp 2.8 1.0-7.0 0.50, e

Propeller 20.0 hp 12.0 3.0- 100.0 0.30, e

Turbine, single impeller 1.0 ft2 0.137, j 0.80, j

Air cooler

Blower

Centrifugal 4000 ft2/min 60.0 800,0- 1.8x10

4 0.59, c

Compressors and drivers

Centrifugal, electric motor 600 hp 190 2x103 - 1.8x10

4 0.32 c

Centrifugal, steam or gas turbine 600 hp 210 2x103 - 2.1x10

4 0.32, c

Electric motors

Open drip proof 60 kW 3.0, g 0.2x103 - 5.0x10

3 1.10, f

Totally enclosed 60 kW 4.0, g 0.25x103 - 6.0x10

3 1.10, f

Explosion proof 100 kW 9.5, g 0.3x103 - 8.0x10

3 1.10, f

Evaporators (installed)

Forced circulation 1000 ft2 2500, i 1.0x10

2 - 7.0x10

3 0.70, e

Horizontal tube 1000 ft2 120, i 1.0x10

2 - 8.0x10

3 0.53, e

Vertical tube 1000 ft2 180, i 1.0x10

2 - 8.0x10

3 0.53, e

Fans

Centrifugal, radial, low range 4000 ft2/min 2.5 1.0x10

3 - 1.0x10

4 0.44

Centrifugal, radial, high range 10 000 ft2/min 40.0 1.0x10

4 - 1.0x10

5 1.17

Heat exchanger (shell/tube)b

129

Floating head, CS/CS 150 psia 1000 ft2 14.0 1.0x10

2 - 5.0x10

3 0.65, e

Process furnace 20 000 kJ/s 750, g 3.0x103 - 1.6x10

5 0.85, g

Pumps

Centrifugal, high range 20 hp 9.0 2.68 - 335 0.42, g

Centrifugal, low range 0.29 hp 2.3 0.10 -2.0 0.29, g

Gear, 100 psia 80 gpm 1.3 16 - 400 0.36, f

Reactorno agitator

Stirred tank, jacketed, CS, 50 psia 600 gal 17.0 30 - 6.0x103 0.57, f

Stirred tank, glass lined, 100 psia 400 gal 33.0 30 - 4.0x103 0.54, c

Rotary vacuum filter (SS) 30 ft2 60.0 4.0 - 600 0.67, c

Tanks

Storage, cone roof, low range 12x106 gal 170 2.0x10

5 - 1.2x10

6 0.32, f

Storage, cone roof, high range 12x106 gal 170 1.2x10

6 - 1.1x10

7 0.32, f

b. The shell-and-lube materials can differ. CS/SS means carbon steel shell and the stainless steel tubes.

c. Remer, D. S, Chai, L.H, Design Factors for Scaling-up Engineering Equipment, Chem. Eng. Progr, 87, 8, 77, 1990.

e. Guthrie, K.M., Data and Techniques for Preliminary Cost Estimating, Chem. Eng., 76, 7, 114, 1969.

f. Woods, DR., Financial Decision Making in the Process Industry, Prentice Hall, Englewood Cliffs, NJ, 1975.

g. Ulrich, G.D., A Guide to Chemical Engineering Process Design and Economics, John Wiley & Sons, New York, NY, 1984.

i. Peters, M.S., Timmerhaus, K.D., Plant Design and Economics for Chemical Engineers, 4th ed., McGrawHill, New York, NY, 1991.

j. Baasel, W.D., Preliminary Chemical Engineering Plant Design, 2nd edt., VanNostrand, New York, NY, 1990.

130

Table A.4

Equipment cost data 2

Equipment Size unit, S Size range Constant, C, £ C, $ Index, n Comment

Agitators

Propeller Driver 5 - 75 1 200 1 900 0.5

Turbine Power, kW 1 800 3 000 0.5

Boiler Oil or gas fired

Packed

up to 10 bar kg/h steam (5 -50)x103 70 120 0.8

10 to 60 bar 60 100 0.8

Centrifuges

Horizontal basket dia, m 0.5 - 1.0 35 000 58 00 1.3 Carbon steel

Vertical basket 600 35 000 58 000 1.0 x 1.7 for SS

Compressors

Centrifugal Driver 20 -500 1 160 1 920 0.8 Electric, max press

Power, kW

Reciprocating 1 160 2 700 0.8 50 bar

Conveyors

Belt Length, m 2 - 40

0.5 m wide 1 200 1 900 0.75

1.0 m wide 1 800 2 900 0.75

Crushers

Cone t/h 20 -200 2 300 3 800 0.85

Pulverisers kg/h 2 000 3 400 0.35

Dryer

Rotary area, m2 5 - 30 21 000 35 000 0.45 Direct

Pan 2 -10 4 700 7 700 0.35 gas fired

Evaporators

Vertical tube area, m2 10 - 100 12 000 20 000 0.53 Carbon steel

131

Falling film 6 500 10 000 0.52

Filters

Plate and frame area, m2 5 - 10 5 400 8 800 0.6 Cast steel

Vacuum drum 1 -10 21 000 34 000 0.6 Carbon steel

Furnaces

Process Heat abs,kW 103 - 10

4 330 540 0.77 Carbon steel

Cylindrical 103 - 10

5 340 560 0.77 x 2.0 SS

Box

Reactors

Jacketed Capacity, m3 3 - 30 9 300 15 000 0.4 Carbon steel

Agitated 18 500 31 000 0.45 Glass lined

Tank

Process Capacity, m3

Vertical 1 -50 1 450 2 400 0.6 atm, press

Horizontal 10 - 100 1 750 2 900 0.6 Carbon steel

Storage

Floating roof 50 - 80 000 2 500 4 350 0.55 x 2 for

Cone roof 50 - 80 000 1 400 2 300 0.55 Stainless steel

Appendix B

Table B.1

SGS pyrolysis oil test report

Diesel Analysis Report

Client Milvinetix

Product Gasoil

Sample source unknown

Sampling method Supplied Lab report

No. 557/1-1-10-12

Date supplied 26 October 2012 Time sampled 10H00

Date tested 30 October 2012 Time tested 16H00

Sample condition 1x Plastic 5 litre bottle

Test description Test method Specification Results

Density @20oC, kg/l ASTM D4052 0.800 0.8950

Viscosity @ 40oC, cSt ASTM D445 2.2-5.3 2.868

Flash point, oC ASTM D93 55 min <25

Water content, ppm ASTM 6304 500 max 673

Sulphur content, ppm ASTM D4294 Report 8100

Total contamination number, mg/kg IP 440 24 max 31

Distillation oC:

ASTM D86 362 max 378.8 - 90% recovery,

oC

Micro carbon residue (10% bottoms) ASTM D4530 0.2 max 4.5

Cetane index ASTM D4737 Report 32.01

133

Diesel Analysis Report

Table B.2

Wear Check diesel analysis report

Test description Results Units SANS 342 (2006) SPECIFICATIONS

Density @20oC 0.8772 kg/l 0.800 Pass Density is within the SANS specifications

Viscosity @ 40oC 2.1 cSt 2.2-5.3

Not require or not tested

Flash point 26 oC 55 min Fail Flashpoint is below the specification

Water content 0.06 % 500 max Fail Water content exceeds the specification

Sulphur content 21400 ppm Report Pass Sulphur Content exceeds the specification

Total contamination number 38.6 mg/kg 24 max Fail Total Contamination exceeds the spec.

90% recovery temperature 360 oC

Fail The 90% Rec. Temp. is within specification

% Residue 2 % 0.2 max

Calculated cetane index 34.2 Report

For all correspondence, please contact WearCheck Africa

Tel: (031) 700-5460 / (011) 392-6322, Fax: (031) 700-5471 / (011) 392-6350 or Email: support@wearcheck.co.za

2011/09/02 WEARCHECK AFRICA IS A REGISTERED ISO 9001 AND ISO 14001 COMPANY

Table B.3

Coal and Minerals Laboratory, CSIR, carbon black sample

Milvinetix

Date received 22 June 2012

Date reported 27 July 2012

Job No. 145/12-1

SABS No

Sample

Carbon black

Description Coal

Air Dry Basis Test Method Results

Calorific value MJ/kg 2215/14/W07 31.18

Moisture content % 2215/14/W06 1.3

Ash content % 2215/14/W10 / ASTM 1506 14.5

Volatile matter content % 2215/14/W09 24.3

Fixed carbon % By diff. 59.9

Total sulphur % ASTM D4239 2.61

Table B .4

Pyrolysis plant model revenue costing, inflation index and utility costs

Revenue costing

Variable Units Base cost Year 0 Year 1 Year 2 Year 3 Year 4

Tyre fee

R 13,00 R 29 786,74 R 29 786,74 R 29 786,74 R 29 786,74 R 29 786,74

Selling price of tyre derived fuel R/L R 9,50 R 10 065 269,86 R 10 467 880,66 R 10 467 880,66 R 11 567 008,13 R 12 769 976,97

Selling price of carbon black @ different

grades

R 430,00 R 310 354,89 R 322 769,09 R 322 769,09 R 322 769,09 R 322 769,09

Rubber + rubber products (24-33nm, N220) R/ton

Paints(70-96 nm, N770) R/ton

Pigments(70-96 nm, N770) R/ton

Activated carbon (250-350 nm, N990) R/ton

Briquettes R/ton

Selling price of steel wires R/ton R2500,00 R 773 309,53 R 804 241,91 R 892 708,52 R 892 708,52 R 892 708,52

R 11 178 721,02 R 12 089 665,53 R 13 001 590,96 R 14 157 561,09 R 15 472 826,42

Inflation

Year 0 Year 1 Year 2 Year 3 Year 4

Product price inflation Index

1,00 1,04 1,11 1,11 1,10

Labour cost inflation Index

1,00 1,04 1,08 1,10 1,00

Material cost inflation Index

1,00 1,05 1,12 1,16 1,22

Fuel cost inflation Index

1,00 1,05 1,12 1,16 1,22

General inflation Index 1,00 1,04 1,09 1,10 1,22

Variable costs

Electricity

R 61 257,60 R 63 707,90 R 69 441,62 R 76 385,78 R 93 190,65

Water

R 218 437,27 R 227 174,76 R 247 620,49 R 272 382,54 R 332 306,70

Reagent

R 120 000,00 R 124 800,00 R 136 032,00 R 149 635,20 R 182 554,94

nitrogen

R 687,79 R 225 937,70 R 234 975,21 R 260 822,48 R 288 208,84 R 318 182,56

R 625 632,57 R 650 657,87 R 713 916,59 R 786 612,36 R 926 234,85

136

Table B .5

Pyrolysis plant model revenue costing, inflation index and utility costs continued...

Revenue costing

Variable Units Base cost Year 5 Year 6 Year 7 Year 8 Year 9

Tyre fee

R 13,00 R 29 786,74 R 29 786,74 R 30 382,47 R 30 382,47 R 30 382,47

Selling price of tyre derived fuel R/L R 9,50 R 14 098 054,58 R 15 578 350,31 R 15 889 917,31 R 17 320 009,87 R 18 186 010,37

Selling price of carbon black @ different

grades R 430,00 R 322 769,09 R 322 769,09 R 355 046,00 R 355 046,00 R 355 046,00

Rubber + rubber products (24-33nm, N220) R/ton

Paints(70-96 nm, N770) R/ton

Pigments(70-96 nm, N770) R/ton

Activated carbon (250-350 nm, N990) R/ton

Briquettes R/ton

Selling price of steel wires R/ton R 2 500,00 R 892 708,52 R 892 708,52 R 981 979,38 R 981 979,38 R 981 979,38

R 16 939 024,09 R 18 590 094,20 R 18 983 057,67 R 20 369 285,31 R 20 531 089,12

Inflation

Year 5 Year 6 Year 7 Year 8 Year 9

Product price inflation Index

1,10 1,11 1,10 1,09 1,05

Labour cost inflation Index

1,06 1,07 1,09 1,09 1,10

Material cost inflation Index

1,28 1,34 1,41 1,48 1,55

Fuel cost inflation Index

1,28 1,34 1,41 1,48 1,55

General inflation Index

1,15 1,11 1,02 1,05 1,04

Variable costs

Electricity

R 107 169,24 R 118 957,86 R 121 337,02 R 127 403,87 R 132 500,02

Water

R 382 152,70 R 424 189,50 R 432 673,29 R 454 306,95 R 472 479,23

Reagent

R 209 938,19 R 233 031,39 R 237 692,01 R 249 576,61 R 259 559,68

nitrogen

R 687,79 R 351 273,55 R 388 157,27 R 426 973,00 R 465 400,57 R 488 670,60

R 1 050 533,68 R 1 164 336,02 R 1 218 675,32 R 1 296 688,01 R 1 353 209,53

137

Table B.6

Pyrolysis plant model revenue costing, inflation index and utility costs continued...

Revenue costing

Variable Units Base cost Year 10 Year 11 Year 12 Year 13

Tyre fee

R 13,00 R 30 382,47 R 30 382,47 R 30 382,47 R 30 382,47

Selling price of tyre derived fuel R/L R 9,50 R 19 277 170,99 R 20 241 029,54 R 20 848 260,42 R 21 473 708,24

Selling price of carbon black @ different grades

R 430,00 R 355 046,00 R 355 046,00 R 355 046,00 R 355 046,00

Rubber + rubber products (24-33nm, N220) R/ton

Paints(70-96 nm, N770) R/ton

Pigments(70-96 nm, N770) R/ton

Activated carbon (250-350 nm, N990) R/ton

Briquettes R/ton

Selling price of steel wires R/ton R 2 500,00 R 981 979,38 R 981 979,38 R 981 979,38 R 981 979,38

R 21 883 253,56 R 22 688 859,25 R 22 882 138,32 R 23 526 349,56

Inflation Year 10 Year 11 Year 12 Year 13

Product price inflation Index

1,06 1,05 1,03 1,03

Labour cost inflation Index

1,06 1,02 1,02 1,00

Material cost inflation Index

1,63 1,71 1,80 1,89

Fuel cost inflation Index

1,63 1,71 1,80 1,89

General inflation Index 1,02 1,03 1,00 1,00

Variable costs

Electricity

R 135 150,03 R 139 204,53 R 139 204,53 R 139 343,73

Water

R 481 928,82 R 496 386,68 R 496 386,68 R 496 883,07

Reagent

R 264 750,87 R 272 693,40 R 272 693,40 R 272 966,09

nitrogen

R 687,79 R 517 990,83 R 543 890,37 R 560 207,09 R 577 013,30

R 1 399 820,55 R 1 452 174,98 R 1 452 174,98 R 1 453 627,16

138

Table B.7

Pyrolysis plant model fixed cost, total costs and profits continued...

Fixed costs Quantity Base cost Year 5 Year 6 Year 7 Year 8 Year 9

Rental

R 230 400,00 R 241 217,22 R 253 278,08 R 265 941,98 R 279 239,08

Plant manager 1 35000 R 550 548,55 R 589 086,95 R 642 104,78 R 700 536,31 R 770 589,94

Plant engineer 1 28000 R 440 438,84 R 471 269,56 R 513 683,82 R 560 429,05 R 616 471,95

Shift foreman 4 19000 R 1 195 476,86 R 1 279 160,24 R 1 394 284,66 R 1 521 164,56 R 1 673 281,02

Skilled technicians

boiler maker 2 16000 R 503 358,68 R 538 593,78 R 587 067,22 R 640 490,34 R 704 539,38

fitter 2 16000 R 503 358,68 R 538 593,78 R 587 067,22 R 640 490,34 R 704 539,38

electrician 2 16000 R 503 358,68 R 538 593,78 R 587 067,22 R 640 490,34 R 704 539,38

mechanical 2 16000 R 503 358,68 R 538 593,78 R 587 067,22 R 640 490,34 R 704 539,38

Plant operators 16 11500 R 2 894 312,39 R 3 096 914,26 R 3 375 636,54 R 3 682 819,46 R 4 051 101,41

Security 4 4000 R 251 679,34 R 269 296,89 R 293 533,61 R 320 245,17 R 352 269,69

Cleaners 2 4000 R 125 839,67 R 134 648,45 R 146 766,81 R 160 122,59 R 176 134,84

Accountant/secretary 2 20500 R 644 928,30 R 690 073,29 R 752 179,88 R 820 628,25 R 902 691,08

R 8 116 658,65 R 8 684 824,76 R 9 466 458,99 R 10 327 906,76 R 11 360 697,43

Maintenance

R 846 610,02 R 939 737,12 R 958 531,86 R 1 006 458,46 R 1 046 716,79

Land rental/ lease

R 314 907,28 R 349 547,08 R 356 538,02 R 374 364,92 R 389 339,52

Insurance

R 90 119,39 R 100 032,53 R 102 033,18 R 107 134,84 R 111 420,23

Tax/Levies

R 180 238,79 R 200 065,06 R 204 066,36 R 214 269,68 R 222 840,46

Medical

R 84 661,00 R 93 973,71 R 95 853,19 R 100 645,85 R 104 671,68

Telephone line

R 52 484,55 R 58 257,85 R 59 423,00 R 62 394,15 R 64 889,92

IT

R 84 661,00 R 93 973,71 R 95 853,19 R 100 645,85 R 104 671,68

Auditing fees

R 84 661,00 R 93 973,71 R 95 853,19 R 100 645,85 R 104 671,68

Miscellaneous materials

R 84 661,00 R 93 973,71 R 95 853,19 R 100 645,85 R 104 671,68

Safety clothing (PPE)

Cleaning material

Payment period and profits

Year 5 Year 6 Year 7 Year 8 Year 9

Costs

R 12 237 903,91 R 13 131 220,01 R 14 019 725,09 R 15 075 049,70 R 16 264 347,22

Revenues

Profit after tax R 15 652 561,34 R 19 695 047,83 R 22 813 386,26 R 26 509 559,70 R 28 910 206,32

Net annual

profit R 3 414 657,44 R 6 563 827,83 R 8 793 661,17 R 11 434 509,99 R 12 645 859,09

139

Table B.8

Pyrolysis plant model fixed cost, total costs and profits continued...

Fixed costs Quantity Base cost Year 10 Year 11 Year 12

Rental

R 293 201,03 R 307 861,08 R 323 254,14

Plant manager 1 35000 R 816 825,34 R 833 161,85 R 849 825,08

Plant engineer 1 28000 R 653 460,27 R 666 529,48 R 679 860,07

Shift foreman 4 19000 R 1 773 677,88 R 1 809 151,44 R 1 845 334,46

Skilled technicians

R 0,00

boiler maker 2 16000 R 746 811,74 R 761 747,97 R 776 982,93

fitter 2 16000 R 746 811,74 R 761 747,97 R 776 982,93

electrician 2 16000 R 746 811,74 R 761 747,97 R 776 982,93

mechanical 2 16000 R 746 811,74 R 761 747,97 R 776 982,93

Plant operators 16 11500 R 4 294 167,49 R 4 380 050,84 R 4 467 651,86

Security 4 4000 R 373 405,87 R 380 873,99 R 388 491,47

Cleaners 2 4000 R 186 702,93 R 190 436,99 R 194 245,73

Accountant/secretary 2 20500 R 956 852,54 R 975 989,59 R 995 509,38

R 12 042 339,28 R 12 283 186,06 R 12 528 849,79

Maintenance

R 1 067 651,13 R 1 099 680,66 R 1 099 680,66

Land rental/ lease

R 397 126,31 R 409 040,10 R 409 040,10

Insurance

R 113 648,64 R 117 058,09 R 117 058,09

Tax/Levies

R 227 297,27 R 234 116,19 R 234 116,19

Medical

R 106 765,11 R 109 968,07 R 109 968,07

Telephone line

R 66 187,72 R 68 173,35 R 68 173,35

IT

R 106 765,11 R 109 968,07 R 109 968,07

Auditing fees

R 106 765,11 R 109 968,07 R 109 968,07

Miscellaneous materials

R 106 765,11 R 109 968,07 R 109 968,07

Safety clothing (PPE)

Cleaning material

Payment period and profits

Year 10 Year 11 Year 12

Costs

R 17 051 639,91 R 17 428 470,33 R 17 689 527,10

140

Revenues

Profit after tax R 31 449 449,29 R 33 804 180,59 R 35 854 519,70

Net annual profit R 14 397 809,38 R 16 375 710,27 R 18 164 992,60