ENVIRONMENTAL EVALUATION OF PLASTIC WASTE …

ENVIRONMENTAL EVALUATION OF PLASTIC WASTE

MANAGEMENT SCENARIOS

L. Rigamonti1, J. Møller2, M. Grosso1, T.H.Christensen2

1 Politecnico di Milano, Italy 2 Technical University of Denmark, Denmark

1st International EIMPack Congress

Recycling of Packaging Waste: Considering

all the Costs and all the Benefits

29, 30 November 2012 - Lisbon

Nome relatore SEWAS Project – L. Rigamonti

Context

Goal:

to provide a technically sound environmental assessment (LCA) of a range of

alternative municipal solid waste management systems in Europe

to identify the environmentally most beneficiary strategies for future waste

management in Europe - the role of incineration with a view to 2020

to quantify the importance of choice of waste treatment technologies with

special focus on treatment of the plastic fraction in the waste

SEWAS – Sustainable European Waste Systems

Life cycle assessment of prospective integrated waste

management schemes

J. Møller, V. Martinez Sanchez, J. Clavreul,

K.L. Barahona Ramirez, T.H. Christensen

L. Rigamonti, S. Magnani, M. Grosso

A project for

CEWEP


Goal and methodology

The plastic fraction of MSW is specifically addressed in this study, since plastic and its

management is one of the most debated issues in current waste management in

Europe.

There is little doubt that clean fractions of individual types of plastic should be

recycled, but how do the benefits of recycling or recovery of mixed and potentially dirty

plastic compare with the efforts introduced to collect these fractions is still an open

question.

Five scenarios of plastic management are modelled

The environmental assessment was carried out based on the Life Cycle

Assessment (LCA) methodology

The functional unit is the management of 1 tonne of plastic waste as present

in the gross waste


Plastic scenarios

• In the baseline scenario (P0) the plastic is not source

separated at all, which means that it is treated together with

the residual waste (RW).

• In scenarios P1 to P4 a range of potential improvements in

plastic management is introduced, and out of the total plastic

present in the gross waste, a certain amount is sent to

recycling.


Plastic scenarios: P0

P0: Plastic is not collected separately, nor it is mechanically

sorted from the residual waste

The plastic is not source separated at all, which means that it is treated

together with the residual waste (RW):

- 90% is sent to a Waste-to-Energy plant (WTE)

- 10% is sent to a Mechanical-Biological Treatment plant (MBT)

producing Refuse Derived Fuel (RDF) which is sent to cement kiln

(according to the waste management scheme hypothesized for Western Central

Europe)

Typical waste composition of Western-Central Europe region was selected, representing Scandinavia, the

Benelux, Germany, Northern Italy. MSW produced in this region has a relatively high content of paper and

a medium content of organic kitchen waste, while total plastic represents 10% in weight.



P0: Plastic is not collected separately

P1: Source separation only of bottles at 80% efficiency,

leading to an overall plastic collection efficiency of 22%.

The bottles are mechanically separated into PET and

HDPE and then recycled to PET flakes and HDPE

granules




P1: Source separation only of bottles at 80% efficiency

P2: Source separation of all plastic (80% efficiency for bottles;

50% efficiency for the other plastic fractions), leading to an

overall plastic collection efficiency of about 58%. The

fraction is separated into PET, HDPE, a polyolefin fraction

and residues (i.e. Plasmix) used as fuel.

The material will include

impurities, dirt and other items

which will end up in the

Plasmix.

An advanced sorting plant

located in Northern Italy was

taken as a reference for this

scenario.




P2: Source separation of all plastic

P3: Plastic collection (80% efficiency for bottles; 30% efficiency

for the other plastic fractions) in the “dry bin” together with

metals. The overall plastic collection efficiency is 43.5%.

Composition of the dry bin (wet weight)

Iron 21%

Aluminium 6%

Plastic 73%





P2: Source separation of all plastic

P3: Plastic collection in the “dry bin” together with metals

P4: No source separation for plastic, but plastic is mechanically

sorted from residual waste prior to incineration. The

mechanical separation removes PET and HDPE bottles at

high efficiency, which are sent to recycling, and other minor

high calorific fluxes sent to energy recovery in cement kilns.


RW is pre-treated in a MRF facility located

just ahead of the WTE plant, where the focus

is on removing high quality plastic by

mechanical process units for its subsequent

recycling.

This scenario is based on a new approach

proposed in the Netherlands, starting from

the assumption that citizens might be

annoyed by a further request of sorting

plastic waste at their household.


Plastic scenarios

Scenario F.U.(0)

(kg)

Source

separation

(kg)

Plastic in

the RW

(kg)

PET to

recycling

(kg)

HDPE to

recycling

(kg)

Polyolefin

mix to

recycling

(kg)

Residues

to cement

kiln (kg)

Residual

fraction to

WTE (kg)

Energy

consumption

(kWh) (3)

P0 1000 0 1000(1) 0 0 0 0 0 0

P1 1000 216 784(1) 151 43 0 22 0 6.5

P2 1000 581 419(1) 151 71 161 198 0 16.7

P3 1000 435 565(1) 135 45 32 223 0 12

P4 1000 0 1000(2) 205 66 0 188 541 151

(0) The functional unit is the management of 1 tonne of plastic waste as present in the gross waste

(1) 90% sent to WTE and 10% to MBT with RDF production sent to cement kiln

(2) Sent to MRF

(3) The energy consumption of the MRFs was assigned exclusively to plastic management (i.e. no

allocation was done when the plastic management affected other waste streams)


Material Process Secondary material/product Avoided primary material/product

PET Recycling* Granules of recycled PET Granules of virgin PET

HDPE Recycling* Granules of recycled HDPE Granules of virgin HDPE

Polyolefin mix Recycling*

Flakes of mix of polyolefins used to

manufacture products traditionally

made of wood that instead could be

used to generate energy

heat production from natural gas

Residues and RDF

from the plastic in

the RW

Co-combustion

in cement kiln Fuel Coal in cement kiln

Plastic in the RW

and residual

fraction in P4

WTE Electricity and heat

Electricity by coal and heat by a mix

(20% district heating (coal and gas),

14% hard coal, 2% lignite, 8% oil,

42% natural gas, 13% wood)

We have expanded the system boundaries by crediting the plastic

waste management system for energy and material recovery

Avoided products

*the technical substitution for PET, HDPE and polyolefin mix is respectively 75.5%, 90%, 60%; the market substitution is

respectively 81%, 81% and 50%.

Benefits from metal recycling resulting from the overall sorting process in P3 and P4 were not

ascribed to plastic recycling (i.e. the system was modelled as if only plastic was treated in the

waste management system)


In general, LCA applied to waste management systems means:

• To evaluate environmental impacts (direct and indirect) associated

with collection, treatment, recovery and disposal of waste

• To evaluate avoided impacts associated with the conventional

production of materials and energy displaced by those produced in

the waste system

• To compare added and avoided impacts to evaluate the overall

environmental performances of the system

+

-

+/-

We have expanded the system boundaries by crediting the

waste management system for energy and material recovery

Added and avoided impacts


• The analysis was carried out with the LCA-waste-model EASEWASTE

(Environmental Assessment of Solid Waste Systems and Technologies)

developed by DTU Environment, Technical University of Denmark.

• The impact assessment was conducted according to the EDIP-method.

• The emissions are aggregated into the following potential impact

categories: global warming, acidification, nutrient enrichment

(eutrophication), photo-chemical ozone formation and a number of toxic

impact categories including eco-toxicity in water and soil and human

toxicity via soil, water and air.

• The potential impacts were normalized using the person equivalent (PE)

by dividing the impacts with the yearly impact by an average person from

all activities in life

Impact assessment

Nome relatore SEWAS Project – M. Grosso

Results: Non-toxic impact categories

-140

-120

-100

-80

-60

-40

-20

0

20

40

Global Warming Acidification Nutrient EnrichmentPhotochemical Ozone

FormationStratospheric Ozone

Depletion

mPE/fu

P0 (plastic sorting = 0% without mechanical sorting) P1 (plastic sorting = 80% bottles)

P2 (plastic sorting = 80% bottles and 50% other plastic) P3 (dry bin)

P4 (plastic sorting =0% with mechanical sorting)

GW AC NE POF

P0 contributed with direct savings for all impact categories but “Global Warming”, where it represents a net load to the

environment, in clear contrast with the other scenarios. On the other hand, P0 performed best of all in “Acidification”. Scenarios P1

to P4 had better results than P0 for “Global Warming” and “Nutrient Enrichment”, but with a different pattern. In “Stratospheric

Ozone Depletion” absolute impacts in milli Person Equivalents are very modest, as well as the variation among scenarios.

As a final consideration, none of the examined scenarios emerged as the best option for all non-toxic impact categories.

OD

mP

E/t


Results: Toxic impact categories

Huge impact savings are observed for all of the scenarios in the categories “Ecotoxicity in Water”, “Human Toxicity via Water” and

“Human Toxicity via Soil”. On the contrary, “Ecotoxicity in Soil” and “Human Toxicity via Air” had negligible impacts or loads in

terms of milli Person Equivalents. Differences among scenarios are generally modest, with the sole exception of “Ecotoxicity in

Water”. Focussing on the latter, which is also the most beneficial category, P1 performed best of all, while P2 to P4 resulted

worse than P0.

As for the non-toxic impact categories, none of the examined scenarios emerged as the best option for all toxic impact categories.

HT ET

mP

E/t


The maximum contributions to the savings on “Global Warming” impact category are related to plastic co-combustion in

cement kiln and plastic recycling. Plastic in the residual waste ending up in RDF co-combusted in cement kiln also plays a

role, despite the modest amount of material following that path. Incineration always represents a load due to the fossil CO2

emissions from plastic combustion. It is then easy to understand why for this impact category the P0 scenarios performs

worst, giving a net load to the environment, while all the other scenarios where a certain amount of plastic is recycled or co-

combusted result in a net saving.

Results: Contributions to global warming


A completely different picture compared to “Global Warming” is obtained for “Acidification”, where incineration of plastic contained

in the residual waste plays a major role in determining the savings. This is due to the balance of SO2 emissions between plastic

combustion and substituted coal combustion, the latter being much higher because of the higher content of sulphur. Plastic

recycling and plastic co-combustion in cement kiln give a modest saving in P1 to P4 scenarios, while in P4 the operation of the

MRF for plastic sorting prior to incineration constitutes a load. This is due to its energy consumption which, as explained, in the

modelling of the plastic scenarios was fully allocated to the plastic content of the residual waste.

Results: Contributions to acidification


For “Nutrient Enrichment”, incineration of plastic in the residual waste is very relevant in determining the overall savings for

scenario P0, while for scenarios P1 to P4 it gives savings of similar order of magnitude with plastic recycling. A similar picture

was obtained for “Photochemical Ozone Formation” and “Stratospheric Ozone Depletion”.

Results: Contributions to nutrient enrichment


Conclusions (1)

When moving from the P0 treatment strategy to the other

scenarios, it can be concluded that:

Substantial improvements (i.e. transforming loads to

savings) can be obtained for “Global Warming”, especially

with the P2-scheme

Minor improvements can be obtained for “Nutrient

Enrichment”

Impact in the category of “Acidification” will increase (in

terms of a lower saving and not of an actual load to the

environment)

In the remaining impact categories the changes are

relatively small


Conclusions (2)

In conclusion, the proposed plastic management strategies

performed well since all the improvement scenarios P1 to P4

show net savings for all the impact categories.

None of the examined scenarios emerged as the best option for

all impact categories: if focus is on “Global Warming”, the best

alternative is scenario P2 (Source separation of all plastic),

whereas for the rest of impact categories the best options are

P1 (Source separation only of bottles at 80% efficiency) and P4

(No source separation for plastic, but plastic is mechanically

sorted from RW prior to incineration).

P0 (Plastic is not collected separately) clearly performs best of

all only in the “Acidification” category.


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ATTENTION!

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ENVIRONMENTAL EVALUATION OF PLASTIC WASTE …