Che 3163 Sustainability Notes

7/18/2019 Che 3163 Sustainability Notes

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WEEK 1

Brutland Report (1987): meeting the needs of the present without compromising the ability of

future generations to meet their own needs.

SD: social, ecological and economic factors

. Living and nonliving resources. Long term and shortterm consequences. The SD policy involves the maintenance of environmental processes and the

sustainable use of resources. Maintenance of genetic diversity.

Triple bottom line: the economic system draws on material and energy resources from the

environment and on intellectual capital from society. The economy can generate a diversity of

goods and services for the benefit of the society, however, it has an impact on the environment.

The environment, economy and society are all interconnected.

Environmental Indicators: resource depletion, global warming potential, ozone layer depletion,

photochemical smog, human and eco toxicitySocial Indicators: stakeholder inclusion, international standards of conduct regarding business

dealings, child labour, income distribution, satisfaction of social needs including work

Economic Indicators: Gross domestic product (GDP), capital expenditure, environmental

liabilities, ethical investments

World Commission on Environment Development, 2002 Targets: reduce poverty, accelerate shift

towards sustainable consumption and production, increase global share of renewable energy

sources, improve economically viable, socially acceptable and environmentally sound energy

services, develop and disseminate energy efficiency and energy conservation, reduce current loss

of biological diversity, develop water saving technology

Nanotechnology: creating smaller and cheaper devices, using less materials, consuming less

energy, single molecule transistors, enzyme powered bio-molecular reactor, minute blood borne

drug carriers, nanoscale robots, solar nano-technologies

Modern Biotechnology: recombinant DNA, agriculture and medicine (speed up plant breeding,

crop varieties with greater drought resistance, more nutritional value, less environmental stress),

pest resistance

Negative impacts of technological advances: usage of CFC, ozone depletion, increased skin cancer,

explosion of nuclear power plants in ukraine, japan, etc. Anthropogenic global warming,

affordability of nanomaterials, GMO can disrupt ecosystems and cause risk to human health.

Precautionary Principle: where there are threats of serious or irreversible environmental

damage, lack of full scientific certainty should be used as a reason for postponing measures to

prevent environmental degradation. Cost benefit analysis and discretionary judgement are

allowed.


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How to handle negative impacts: avoid transferring genes from foods known to be allergenic.

Check the structure of the new proteins against the structure of known allergens. Measure the

stability of the new protein in stomach and intestinal fluids. Determine how much of the new

protein will be present in the food consumed by humans.

Intra-generational equity: represents the current generation. To achieve material equity andsocial justice within and between countries. Helping poor nations and assuring the poor getting

fair share of resources. Environmental degradation lead to unsafe water, poor sanitation, etc. The

poorest parts of the world will suffer from global climate change. Vicious circle: link between

poverty and environment. Indoor pollution from cooking and heating (burning wood), human

health can suffer. Improving efficiency of cook stoves/solar cook stoves

UNDP and EU Poverty and environment initiative: strengthen participation of the poor in local

plans and policies, transferring ownership of natural assets to the poor and well as resource

transfers, assisting the poor to overcome the high initial costs for sanitation.

Intergenerational Equity: allow future generations to meet their own needs. Can be measured by

the constant capital rule (the value of capital stock must not be allowed to decline for indefinite

future). Weak sustainability: assumes forms of capital can be substitutable with each other.

Strong sustainability is when equivalent stock of natural capital is preserved for future

generations.

1) Principle of not closing down options for future generations by making irreversible

changes, including elimination of species or using up resources

2) Principle of maximising future choices by making a considered judgement as to what are

the most central, significant or important things to preserve and protect the biodiversity,

cultural values, energy, etc.

How to approach SD?

reduce excessive levels of production and consumption

more efficient use of resources

reduce global pollution, protect biodiversity and alleviate poverty

doing business with cleaner and more eco-efficient production process

increase product reuse and recycling

increase public participation in decision making to create policies important to SD.

- begin and maintain a transition from petrochemical to biochemical feedstocks

- develop water saving strategies

- transition from fossil fuels to more sustainable energy

- develop near zero waste development strategies


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WEEK 2

Process Synthesis: define problem, specify feedstock, product specification, synthesis alternative,

processes to convert feedstock to product, evaluate alternative processes (technical, economic,

safety, environmental, sustainable), choose best alternative.

Problem Definition Process design study phase, feed phase, detailed design phase

Problem Statement: primitive problem expresses the current situation and provides an

opportunity to satisfy a societal need. Need to address the source of raw materials, cost of

materials, selling price of product, plant scale and location.

Process Creation: assemble a database of information - thermophysical properties, lab

experiments, economic data on equipment and chemical costs. Synthesize flowsheets involving

the reaction and separation.

Criteria for Evaluation: reliability, capital costs, operating cost, safety, environmental,sustainability, technical feasibility, operability

Process Synthesis Steps: develop a process which converts the raw materials to products by

eliminating differences in molecular type, composition, temp, pressure and phase

- eliminate differences in molecular type

- distribute chemicals by matching sources and sinks

- eliminate differences in composition and temp

- integrate tasks by combining operations

Reactor to separation and recycle system to heat exchanger network to utility system.

Fuels: heating and cooling duties, electricity, nitrogen for purging, compressed air, water for

cleaning, fire fighting. Utility waste can be minimised by reducing the consumption of utilities on

process plants. Improving the design of the utility systems themselves like heat exchangers and

cooling tanks, use them in a more efficient way.

Environmental impacts associated with utilities: generation, distribution, consumption, upstream

extraction, purification and supply of resources such as fuel and water. Operating costs are

sometimes dominated by the cost of utilities.

Fuel generation: electricity generation from coal fired power stations and transmission. Crude oil

extraction, transport and refining in the production of fuel oil. Natural gas extraction, purification,

mining, cleaning and transporting the coal.

Fuel types: natural gas, LPG and Condensate, crude oil, coal, biofuels. Mainly used for high

temperature heating of process fluids, steam and electricity generation. Need to consider supply

issues in terms of availability, quality and cost, CO2 and other emissions with fuel combustion,

resource depletion issues for fossil fuels


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Fuel combustion: furnaces, incinerators, gas turbines, diesel engines, flare stacks, transport

vehicle engines to produce electric power, energy, etc.

Emissions include: SOx, NOx, CO2, CO, unburned hydrocarbons, particulates, ash

Heat of Combustion:

- total heating value is the heat evolved in the complete combustion of the fuel underconstant pressure at 25 degrees when all water initially present in the fuel and in the

combustion products is condensed to the liquid state

- net or lower heating value is similar except that the final state of the water after

combustion is taken as water vapour at 25 degrees.

Combustion under excess air: to ensure complete combustion. It is important to prevent the

production of CO - toxic. Amount of excess air depends on the burner and furnace design

(number of boiler passes, surface area, material of construction). Typically 25% for coal

combustion and 10-15% for gas combustion.

Fuel ratio: the ratio of its percentage fixed carbon to that of volatile matter, Low fuel ratio =

decrease in fuel value.

Environmental impacts of flue gases: acidification, global warming, nitrification, photochemical

smog, resource depletion, human health effects. Can be reduced by: minimising utility

consumption, switching to a cleaner fuel, using fuel of higher calorific value, improved burner

design, treating the fuel before combustion to minimise impurities, treating stack gases after

combustion to remove certain pollutants.

Reducing NOx emissions can be done by: lowering the temp of fuel combustion, using fuels which

are lower in nitrogen, using less excess air, catalytically reducing NOx produced to nitrogen andwater.

Dew point: temperature at which the onset of condensation occurs during cooling of the flue gas.

Condensate can be corrosive to the equipment and piping due to low pH, but also due to nitric

and sulphuric acids resulting from NOx and SOx in the flue gas.

WEEK 2 TUTE

1. What is the definition of Sustainable Development (as per the World Commission on

Environment and Developments Brundtland Report)? Explain the concept of intergenerational

equity in this definition.

Sustainable development is defined as meeting the needs of the present without compromising

the ability of future generations to meet their own needs.

This is a description of intergenerational equity in that it considers people in the future, in

particular avoiding closing down of future options for development to people in the future and

maximising future choices available to those in the future.


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2. Explain the difference between strong and weak sustainability and how they apply to

different forms of capital.

Weak sustainability seeks to maintain constant capital between various forms of capital (human,

financial, social, environmental) but it assumes they are substitutable for each other. Strong

sustainability seeks to maintain constant natural capital for future generations (does not assume

substitution is possible)

3. What is the triple bottom line and how does it refer to the measurement and reporting of the

three key aspects of sustainable development? What are some typical indicators used for each of

the three key aspects?

The triple bottom line is the targeting, monitoring and measurement of indicators in all three key

areas of SD: environmental, social, economical. Typical indicators include:

environmental - global warming potential. ozone depletion, resource depletion,

photochemical smog.

economic: gross domestic product, value added, ethical investments, capital expenditure

social: income distribution, international work practices/standards, stakeholder inclusionin development

4. What practical steps can we take to approach sustainable development? Think of an example

industry and explain how such steps may be applied to that sector. (for e.g. a soft drink

manufacturer may reduce material requirements by reducing the mass of glass in its drink

bottles).

Practical steps include: reducing resource needs, reducing energy intensity, reducing toxic

dispersion, enhancing material recyclability, maximising use of renewable resources, extending

product durability, increasing service intensity.

5. What is the Precautionary Principle? How might it be applied to the use of Genetically Modified

Organisms (GMOs) in the food supply?

Precautionary principle says that where there are threats of serious or irreversible

environmental damage, lack of full scientific certainty should not be used as a reason for

postponing measures to prevent environmental degradation. it is a statement of risk

management pertaining to new developments. For GMOs, it may be applied through careful

avoidance of transfer of genes from known allergenic species, careful control of the spread of

GMO crops into non-GMO crop areas, and significant testing of the eco-and human toxicity of the

GMO crop before its release to market.


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WEEK 3

Energy dissipated to surroundings: there might be no sinks for this energy, too expensive to

convert into another form of energy, not practical to heat exchange (due to pressure, toxicity,

corrosive)

Economical and environmental way to waste energy:- air cooling: no waste of materials, electricity usage is similar to reticulated water cooling,

less labour, cheaper heat exchangers, noisy

- water cooling: closed loop water cooling, reticulated cooling with pond/river/sea,

reticulated cooling with cooling tower.

Power = (Q*delta P)/n

Refrigeration: used in distillation for ethylene manufacturing, LNG. Evaporator to compressor to

condenser to expansion valve.

Process heating:- fired heat (flue gas): natural gas can be oxygen enriched to make it hotter, coal/biomass

flue gas, gas turbine exhaust, molten salts, concentrated solar thermal. Above 400 degrees

- Hot oil heated by flue gas. 90-400 degrees

- Steam is used 90-250 degrees

Steam generation:

- fire tube: hot gases flow through tubes surrounded by a pool of boiling water which is

vaporised. Steam pressure is restricted to 20 bar. Normally used for small steam

generation rates and low pressure

- Water tube: water is circulated by natural convection between a water drum and steamdrum connected by tubes. The boiling water rises and saturated water descends). Hot

gases flow through an external chamber.

- Superheater: superheat saturated steam. Usually integral with a boiler.

- Economisers: heat excahngers that are used to heat water to boiling point temperature

corresponding to the steam generation pressure.

Quantities of dissolved solids need to be reduced to a very low level or else they will accumulate

in the system and destroy equipment.

Feed water - feed water treatment - holding tank - boiler feed pump - deaerater (steam pushes air

out) - chemical dosing (protect materials from corrosion) - boiler feedwater pump - three heat

exchangers (economiser, boiler, superheater) - blowdown/purge (to remove solids) - steam use -

condensate goes back to holding tank

Steam uses: heating, driving turbines, diluent, cleaning plant and equipment.


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Condensate recovery: high quality hot water which is valuable in energy content. Recovery is

important to minimise the quantity of fresh demineralised water. Maximise the energy efficiency

by burning less fuel.

Steam traps must be places in discharge lines from heat exchange spaces to recover condensate

efficiency.

Improving process heating: heat generation, heat transfer, waste heat recovery, sensors and

controls.

Heat Containment Opportunities: use of optimum and adequate insulation for heating equipment

walls, control furnace openings, seals around doors.

Methods of generating electricity: most electric generation is driven by heat engines. Combustion

of fossil fuels supplies most of the heat to these engines. Some from nuclear fission.

Rankine Cycle: boiler feed pump - Steam generator - HP turbine - reheater - LP turbine -

condenser - condensate pump - fed back into pumpBrayton Cycle: combustion chamber - turbine - exhaust - compressor

Environmental Impact of Power Stations: emissions, depletion of fuel and water resources,

aqueous emissions or impact from treatment of these emissions, thermal energy released

Advantages of cogeneration: efficiency of the cogeneration cycle is much higher, reduce fuel

input, reduce emissions, reduce loss of thermal energy

Disadvantages: close proximity to where people live, noisy, have to have proper maintenance

Other utilities: compressed air (instruments, agitators, tools), inert gas (purging flammable gas,vacuum (used in filtration, heat sensitive materials)

Gasification (uses excess fuel instead of air) : done with coal, oil, petro coke, sewage sludge,

plastic tyres. produces syngas and can then be used to make ammonia, methanol, methane,

hydrocarbons, power, fuel gas

Environmental impacts: CO2 is concentrated and in pressurised form, can be captured. No SOx

emissions, H2S can be captured. Particulate emissions are within limits. Heavy organics are also

within limits. Mercury can be captured. 25% less water usage.


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WEEK 4

Onion diagram - main reactor - separation - heat recovery and cooling - final effluent treatment

Checklist for reaction systems:

- Chemical reactions occurring - basic chemistry, reversible/irreversible,

exothermic/endothermic, catalysts, temp, pressure, concentration, side reactions,conversion

- Reactor - phases, batch/continuous, heating/cooling, CSTR, reactor configuration.

Examples - furnace, packed bed reactor, electrolytic cell, stirred tank, platinum gauze

reactors. Chemistry of the process - different reaction pathways, new solvents, improved

catalysts, alternative chemical products which are less toxic.

- Environmental Effectiveness - ratio of kg waste to kg of desired product (E-factor). Q is

the environmental impact. EQ.

- Atom utilisation - measure of how effectively chemical atoms participate in a reaction to

achieve the desired product.Divide the molecular weight of the desired product by the

total products molecular weight- Conversion and Selectivity - moles of desired product produced/moles of reactant

consumed

- Co-product and by-product utilisation - could be useful or a waste, could be turned into a

useful product.

- Impurities in feed - can be unreacted and find their way into the products, can react with

the reactants to produce new waste, can poison the catalyst

- Mixing of reactants - homogeneity of process conditions, even distribution is wanted, can

use a CSTR.

- Minimising secondary reactions - we want good selectivity and minimise wastes.Can be

done by product removal, cooling in waste heat boilers- Recycle of unreacted feed from reactor effluent stream - economic benefit and improved

process efficiency, waste reduction

- Reversible reactions - conversion is limited by equilibrium, may need aditional stages

- Catalyst and catalyst life - help reduce temp and pressure, reduce in energy consumption.

However, catalysts can degrade, so feed has to be ridden of impurities

- Agent materials - used to enable reactions to proceed efficiently, but can be toxic or cause

waste. eg. solvents, reaction enablers, reaction stoppers

Separation Processes - based on phases, components from gas streams, components from liquid

streams. Selection of separation processes depends on raw materials, the compounds that need

to be separated.

Absorption - separation of solute from gaseous mixtures of non-condensable by transfer into a

liquid solvent. eg. absorption of co2 by sodium hydroxide/potassium carbonate solution. Wastes

can be from the energy consumed, electricity, steam, cooling water, gas transport, liquid


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pumping, regeneration of solvent, effluent gas contamination by unabsorbed species, build up on

contaminants, solvent entrainment in gas

Adsorption - process in which atoms or molecules move from a bulk phase onto a solid or liquid

surface. Need a high surface-area solid such as activated charcoal

Solid-liquid separation - settling, filtration, centrifugation, drying. Supernate is the remaining

fluid

Filtration - separation of solids from fluids.

Drying - apply energy to the moisture molecules or changing the environment so that the

molecule has sufficient latent energy to leave the product. No physical or chemical changes occur

Evaporation - large volume of liquid is removed.

Liquid-liquid extraction - two phases are chemically quite different that leads to a separation of

components according to physical and chemical properties.

Distillation - process in which liquid or vapour mixture f two or more substances is separated

into its component fractions of desired purity by the application and removal of heat. Based on

the fact that the vapour of a boiling mixture will be richer in the components that have lower

boiling points. Therefore when this vapour is cooled and condensed, the condensate will contain

the more volatile components.

Sources of waste in distillation - accumulation of non-volatiles, non-condensables, fouling,

abnormal operation, leakage, separation inefficiencies, utilities wastes, energy consumption,

electricity


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WEEK 5

Wastes can result from abnormal operation, start-up and shutdown, maintenance, cleaning and

purging, defects, process product changes

Plant operation: process pressure, temperature and operating values.

Time taken for a process to reach steady state: resonance time, process conditions, nature of

process, complexity, control system. Could be hindered by heat loss, variations in feedcomposition, concentration variation

Plant Shutdown: drainage of equipment, pressure venting from reactors, pipeline purging of

liquids that solidify on cooling, purging of gas lines with inert gas, appropriate process control

system.

Abnormal Operation: failure of relief valve, membrane rupture, failure of a utility, variation of

reactor feed composition, valve failure, failure of instrument or process control system, human

error, mechanical failure

Plant maintenance: equipment might need to be removed or inspection is needed. Draining

process of process fluids might create wastes, process abnormalities.

Process cleaning: wastes from cleaning, acid or alkali used. Wastes can be reduced by

understanding the fouling mechanism, develop a cleaning method to reduce wastes or dangerous

chemical use, process abnormalities, may require plant shut down.

Fouling: physical build up of material that would slow down the efficiency of the process.

Transport and storage: leakages can occur.

Periodic removal of sludge can be a large source of waste. Emissions to air of volatile organiccompounds (storage tank filling condition, change in temp/pressure)

Reducing wastes during operation: waste exchange and integrated manufacturing processes,

good planning, knowledge of current technologies, opportunities for waste minimisation.

Storm water risks: solid entrainment, ground water contamination with dissolved soluble salts,

proper analysis and provision is required.

Driving forces for cleaner production: regulatory rules, customer perception, community

perception, economic benefits

Obstacles: resistance to change, lack of technology, excessive capital costs, insufficient return on

investment

Measuring Profitability:

- ROI = annual profit/capital investment

- net cash generated over project life cycle


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- rate of return

- payback time

Profitability issues:

- time value of money: present value of a hund becoming available in future. Future value of

a fund available at present. Depends on interest rate- cash flow: inflows and outflows at different periods over the life of a project

- depreciation: not a cash flow itself. Internal allowance to provide for future investment in

response to the erosion in the value of assets.

- economic benefits vs. increased capital investments: risks associated with the project

whether business or technology related. Discount rate applied to cash flows, time

required to shutdown the plant for modifications, commissioning and startup. Time

required to develop and prove technology. Costs of purchasing technology, engineering

for a movable target.

- Types of projects and related factors: new power station, new plant to product new clean

product, new plant using cleaner technology, modification to an existing plant to providea waste heat boiler to recover waste heat.

- capital requirements: land, fixed capital into plant and buildings, working capital

- capital sources: equity (shareholder subscriptions and retained earnings), debt (loans)

- capital dependence: I = kQbI = capital investment, K = factor, Q = plant capacity, b =

exponent

Plant costs:

- location

- time - inflation affects labour, materials and equipment costs.

- plant costs - purchased equipment costs, installation, foundations and structures, piping,electrical, instrumentation, overheads for design, construction and project management

- capacity utilisation

- production costs

Net Present Value (NPV): relies on the required rate of return.


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WEEK 6

Greenhouse gases: chemical compounds that enhance the greenhouse effect. They allow sunlight

to enter the atmosphere freely. As the sunlight hits the earths surface, it is reflected back into

space as infrared radiation. Greenhouse gases absorb this infrared radiation therefore trapping

heat in the atmosphere. Examples: water, co2, methane, nitrous oxide n2o, HFCs, PFCs, SF6.

Trend of rising temperatures, rising sea levels, increased acidification of oceans, localised

changes in precipitation that causes droughts, floods, storms. Significant social and political

pressures to reduce these GHG emissions. Leads of initiatives like mandatory reporting of GHG

emissions and carbon pricing.

Sources and sinks of greenhouse gases: regulated by the carbon cycle. Anthropogenic (human

caused) sources of carbon like burning fossil fuels, land use changes, industrial processes, fugitive

emissions. Natural sinks are where this carbon is locked up in a stable form such as biomass

through photosynthesis, in ocean sediment, in solution in the oceans, etc

Anthropogenic sources of GHGs:

combustion of fossil fuels: coal, natural gas, oil, etc. Converts the carbon stored in the

ground into co2 emissions to the atmosphere. Also produces smaller amounts of methane

and n2o.

fugitive emissions of co2 and methane from coal mining, oil and gas exploration, natural

gas distribution, transport of captured or manufactured co2. Direct releases or leaks of

co2/ch4 from previous inventories stored in the ground or from human-made piping or

containment systems.

land use changes. Breakdown of dead vegetation to co2/ch4 and also the breakdown of

nitrogen based fertilisers to n2o. industrial processes that produce GHG as a byproduct. Processes such as clinker (cement)

production, aluminium smelting, hydrogen production from natural gas, nitric acid

production.

Leakage of synthetic GHGs into the atmosphere: SF6 was used as insulating gas in the

electricity sector which had a very high global warming potential

Waste sector: breakdown of solid wastes in landfills to produce methane and co2

GHG reduction: agreements and mechanisms:

Australias Clean Energy Act (2011) also known as the carbon tax. An emissions trading

scheme with a 3 year fixed price period. Requires larger emitters to pay a price for their

emissions.

Renewable Energy Target that provides support for renewable energy to displace fossil

fuel electricity generation

Emitters need to measure and report their GHG emissions in order to verify compliance

and support carbon pricing. If there were no measurements, it would be impossible to

control the situation. Sometimes referred to as greenhouse gas accounting.

Kyoto Protocol in 1997 sets targets for countries to reduce their GHG emissions.


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Greenhouse gas inventory: full account of the emissions produced by an organisation for a given

period of time. A number of standards have been put in place to assist in preparing inventories:

Greenhouse Gas Protocol, produced by the World Resources Institute (WRI) and the

World Business Council for Sustainable Development (WBCSD) is a tool that organisations

can use to understand and quantify GHG emissions. International Standard (ISO 14064-1) Specification with guidance at the organisation

level for quantification and reporting of greenhouse gas emissions and removals

In australia, the national greenhouse and energy reporting measurement must be used by

emitters

Key concepts of GHG inventories:

sources are divided into specific categories: combustion emission from petrol for

transport, fugitive emissions from natural gas exploration, emissions from companys

landfill

all greenhouse gas types clearly stated organisational boundary: if the facility is owned/operated by joint ventures, the

organisation may have part-shares of emissions.

operational boundary: which emissions are included and which are not. For example,

emissions directly produced by a boiler on a companys site are included but what about

the emissions from aircraft associated with business travel?

Scope 1: direction emissions from a facility

Scope 2: emissions produced off-site for the supply of electricity, heating or cooling. These

are indirect emissions.

Scope 3: all other indirect emissions such as air/car travel that are necessary for facility

operation but occurring elsewhere

Global warming potential: in order to allow comparison of emissions, GWP is used. Defined as the

cumulative radiative forcing of both direct and indirect effects integrated over a period of time

from the emission of a unit mass of gas relative to some reference gas.

Quantified measure of the globally averaged radiative warming impacts of a particular

greenhouse gas that is relative to the radiative forcing impact of one tonne of CO2.

Advantage: the calculation is simple as it only needs one piece of activity data. Cheap.

Disadvantage: for variable fuels such as coal, with a possible range of carbon contents, the

emissions can vary.

Methods : more accurate way of measuring emissions by sampling and analysis of fuels for their

carbon content. Benefits include the increased accuracy from fuels with variable energy contents

and carbon contents. As fuels must be analysed, this process if more expensive than looking up

EC and EF factors.

Method 4: involves direct measurement of GHG emissions at the point of emission. Looks at

products of combustion rather than the reactants. Involves the use of periodic or continuous


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sampling and analysis for concentration of CO2/ch4 in the flue gases. Benefits include the fact

that they can capture variable amounts of emissions, automated equipment can be used for this

process. Downside is that it can be expensive, often less accurate.

WEEK 6 TUTE

Question 1:A brewery generates a lot of CO

2 in the fermentation process. This is currently discharged to

atmosphere. It uses some CO2 (which it purchases) for the packaging process and for injection

into the beer to give it "fizz". It also buys hop extract for adding taste to the beer.

It is proposed to capture the CO2 generated in the fermentation process, purify and store under

pressure. This CO2 will be used in the process instead of using purchased CO2. It is also proposed

design and install a process using supercritical CO2 to produce its own hop extract from raw

natural hops.

Based on the following parameters, determine (a) the payback period and (b) the net positive

value of the proposed project over 8 years, given that the required rate of return is 5% per

annum.Cost of equipment and installation = $2.5 million

Annual cost of capital borrowed = 16% of fixed capital cost per annum.

Cost of CO2: $200 per tonne

CO2 purchase saved per batch = 2.3 tonnes

CO2 not discharged to atmosphere per batch = 5.7 tonnes

Cost savings on hop extract per batch = $1800

7 x 100t batches per week, 48 week per year.

Question 2:

Compare the net positive values of the following projects and recommend one for action.Required rate of return: 15%


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Question 3:

A recirculated cooling water system requires make-up of fresh water equivalent to 5% of the

circulating water. Based on the following cost and performance data, estimate of the cost of

cooling water per m

3 of recirculated cooling water.

Question 4:

A shell and tube heat exchanger, constructed with carbon steel shell and tubes and with a heattransfer area 20m2, cost $16,000 in Australia in 1991. Estimate the installed cost of a similar type

of heat exchanger with 304 stainless steel shell and tubes and heat transfer area 20m2 in

Australia in 2005. Assume a Lang factor of 4.

A pressure vessel made of carbon steel and having a volume of 0.3m3 cost $120,000 in Australia

in 1991. Estimate the installed cost of a pressure vessel made of 316 stainless steel and having a

volume of 0.5m3 in Australia in 2005. Assume a Lang factor of 3.8.

Data: Refer to the cost information given in the tables and graphs in the Lecture.

Question 5:A formaldehyde from methanol plant using the metal oxide catalyst process and producing 120

tonnes/day of 37% formaldehyde solution cost $70 million in the USA in 2001. Estimate the cost

of a plant using the same process and producing 180 tonnes/day of of 37% formaldehyde

solution in 2008. Explain how you would estimate the cost of such a plant in Malaysia in 2010.


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WEEK 7

Possible environmental effects of the product: taking up landfill space, production might pollute

the air, not biodegradable, using up non-renewable resources, not recyclable, causes acid rain.

LCA: compilation and evaluation of the inputs, outputs and the potential environmental impacts

of a product throughout its life cycle.Quantitative assessment of the environmental impact of a product over its entire life cycle.

Accounts for inputs (raw material consumption, energy, utilities, transport) and outputs

(emissions to air, land and water)

LCA stages: extraction of raw materials, product manufacture, product use, recycling and reuse,

disposal.

Uses of an LCA: to compare and determine which product or process is more environmentally

friendly. To identify the weak environmental links of an overall product or process. To improve

those segments of the life cycle to make it more environmentally friendly and sustainable.

Life cycle concepts: cradle to grave (entire life cycle), cradle to gate (raw material extraction to

product leaving the factory gate), cradle to cradle (includes recycling stage), gate to gate (single

manufacturing at a particular site), well to wheels (a fuel from its original raw material to its final

production of power output at the wheels of a vehicle)

LCA Methodology:

Goal and Scope definition: scope, purpose, system boundaries and functional unit is all

defined.

Inventory Analysis: all material and energy resources consumed are quantified as well as

the wastes emitted Impact assessment/Classification: inventory data is grouped according to categories of

specific environmental effects or impacts. The data is weighted to provide a numerical

score.

Interpretation: improvement in the processing or product use is identified.

WEEK 7 TUTE

1. What are the six types of greenhouse gases covered by the Kyoto protocol? For each type of

gas, list possible sources.

The six Kyoto gases are:

CO2 - produced from many sources such as fossil fuel combustion, industrial emissions,

breakdown of wastes, water treatment, release of CO2 from forestry activities

Methane - produced from fossil fuel combustion, fugitive emission from natural gas

exploration/processing, breakdown of wastes

Nitrous oxide - produced from fossil fuel combustion, fertiliser production, fertiliser use

Perfluorocarbons - leaks of synthetic gas

Hydrofluorocarbons - leaks of synthetic gas

SF6 - leaks from electrical equipment such as transformers and switchgears


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2. Name three key sinks for greenhouse gases (especially CO2). Describe how these sinks work to

sequester elemental carbon and reduce atmospheric concentrations of greenhouse gases.

the oceans which absorb carbon from atmospheric CO2 into marine life and sequester is

into the deep ocean

forests and other long term vegetation growth which absorb carbon from atmosphericCO2 and store it in solid form in living plant biomass

carbon stored into soils and under the earth by buried vegetation, which in turn absorbed

carbon from CO2 when it was growing

3. ZZZ Ltd. is a multinational corporation with operations around the world. In Australia it owns a

facility that manufactures consumer goods. A different company, AAA Ltd., has been contracted to

operate the business on ZZZs behalf. Which organisation is responsible for reporting the

greenhouse gas emissions for the Australian---based facility, and why?

In australia, the company with operational control is responsible for GHG reporting. AAA is the

operating company and therefore must report the GHG emissions. Ownership is not relevant.They may make commercial arrangements with ZZZ to ensure they are compensated for this

responsibility.

4. Name three key national or international standards or approaches for greenhouse gas

measurement and reporting.

NGERS (Australia)

GHG Protocol (International)

ISO 14064-1 (International)

5. State whether the following GHG emissions sources are Scope 1, Scope 2 or Scope 3 emissions:a. Aviation emissions from business travel for a manufacturing business;

b. Boiler emissions from an off---site steam supplier to a manufacturing business;

c. Fugitive emissions from an oil---refinery natural gas---fired heaters;

d. Emissions from a power station, from the perspective of the operator of that power station

a = scope 3

b = scope 2

c = scope 1

d = scope 1

6. An oil refinery uses fuel oil to supply heat to its boilers. As this facility must pay for its GHG

emissions under a local carbon---pricing scheme (cost $23/tonne CO2---e) they wish to compare

the reported emissions of CO2 using Method 1 (default) and Method 2 (sampling and analysis)

approaches to see which will minimise their liability under the carbon price. Note that emissions

of methane and nitrous oxide will only be reported using Method 1 and therefore are not under

consideration here.

Fuel is sampled and analysed every month for the calendar year 2012. Table 1 shows the results

of the fuel analysis as well as the volumes of fuel combusted for each month are also provided.


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Fuel oil density is a constant 880 kg / m3. Calculate their CO2 emissions using Method 1 and

Method 2 and estimate the carbon price difference between the two methods. (i.e. which is

cheaper, and by how much?).

Only CO2 emissions are relevant as CH4 and N2O are both calculated using Method 1 and will

yield identical carbon prices.

Method 1:

Looking up values for fuel oil in NGER table: EF(CO2) = 72.9kh CO2 eq/GJ

EC = 39.7GJ/kL

Fuel oil quantity for 2012 = 54,201 m

3 = 54201 kL

Emissions (CO2) = 54201 x 39.7 x 72.9 / 1000 = 156,865 tonnes CO2e.

Method 2:

As the Car and EC values vary each month, emissions of CO2 need to be separately calculated

each month and then added up. This provides maximum accuracy from the supplied data. The

example below is for January 2012, then results given for all 12 months:

Q = 5644 m 3 = 5644 kL.

Car = 0.9056. EC = 40.2 GJ/m3

Oxidation factor = 0.99 (for liquid fuels) (from lecture slide 36)

EF (mass basis) = 0.9056 x 0.99 x 3.664 = 3.285 t CO2e / t fuel

EF (energy basis) = EF (Mass basis) (40.2/880) = 71.91 kg CO2 / GJTherefore E(CO2) = 5644 x 40.2x71.91 /1000 = 16315 tonnes CO2---e.

(note: you can go directly from EF (Mass basis) to total emissions without converting to EF

(energy basis) first, as the EC factor cancels out. This approach gives:

E(CO2) = EF(Mass basis) x Q (kL) xDensity (t/m3)= 3.285 x 5644 x 0.880 = 16315 tonnes CO2---e.

Emissions of CO2 for all 12 months are:

Total CO2 emissions for 2012 = 155,426 tonnes CO2---e.


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Difference between Method 1 and Method 2 emissions = ---1439 tonnes CO2---e (i.e. Method 2

figure is lower).

Carbon price difference = $23/t CO2---e x ---1439 = ---$33,095. So emissions using Method 2

costs $33,095 less than Method 1.

7. Look up the default EF and EC values for brown coal (lignite) and various black coals (e.g.bituminous coal). Although the emissions factors for brown coal are quite similar to those for

black coal, facilities of a given capacity that use brown coal typically produce much higher GHG

emissions than those using black coal. Why?

EC of brown coal is similar to that of black coal for given amount of heat (GJ). However, brown

coal is typically high in moisture. Therefore, much of the heat from brown coal must be used to

dry the coal, unlike for black coal. Hence, less heat is available for generating steam or for other

process utilities. This means much more brown coal must be burnt which means that emissions

are higher.

8. For the facility in question 6, the management have requested a review of options to reduce thegreenhouse gas emissions from the facility. List at least three options to reduce emissions from

the facility and briefly state why each option will be effective.

switch to a lower carbon fuel such as natural gas

increase the boiler efficiency so less fuel is required per tonne of steam generated

increase the utility efficiency of the facility so that it requires less steam to meet its

current needs (ensure all steam traps are operating correctly, install insulation, etc)


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WEEK 8

Cleaner Production: the continuous application of an integrated preventive environmental

strategy to processes and products to reduce risks to humans and the environment. For

production processes cleaner production includes conserving raw materials and energy,

eliminating toxic raw materials and reducing the quantity and toxicity of all emissions and wastes

before they leave the process. For products the strategy focuses on reducing impacts along theentire life cycle of the product, from raw material extraction to ultimate disposal of the product.

Key aspects of sustainability:

Integration: cleaner production initiatives must be integrated with business objectives,

technical, safety and operational considerations of processes and plants, over complete

spectrum of industry activity from planning, design, construction, through to operation

and management.

Prevention: cleaner production emphasizes the elimination or reduction of waste at the

source.

Product life-cycle: cleaner production is applied to the entire life cycle of a product fromextraction of basic raw materials through material processing stages, product assembly,

packaging and distribution, use and final disposal.

Global Applicability: although there are differences in priorities and approaches, there is

international acceptance of the need for cleaner production.

Waste Management Hierarchy: source reduction, recycling and reuse, waste treatment, secure

disposal.

Waste can occur within the process systems: reactions, separation, heat exchange, materials

transport, feedstock impurities, waste generated in reactors and separation equipment, energy

used in the process, additives, packaging. Can also occur in the utility systems: fuel combustion,heating and cooling, electricity generation. Waste is generated from the process used, the

equipment used in the process, or from the piping and the physical plant as a whole.

Impacts of wastes: global (global warming, ozone layer depletion), regional (acid rain,

nitrification), local (human toxicity, contamination of land)

Driving forces for cleaner production:

Regulatory: international agreements, licence to operate, customer perception

Community Perception

Economic: potential cost savings through the reduced consumption of raw materials and

energy, future cost of remediation or waste treatment, potential liability arising from

damage to environment, actual costs in generating and treating wastes

Resistances to introducing cleaner production: resistance to change, lack of skilled personnel to

identify opportunities and develop solutions, lack of appropriate technology, time and cost of

developing the technology, capital costs, insufficient return, associated technical risks


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Cleaner production strives to:

reduction in quantity of waste

reduction in toxicity of waste

reduction in consumption of raw materials, energy and utilities

address all facets of chemical engineering such as R&D, design and operation

benefit the health and safety of workers extend to products as well as the processes

extend to all industrial and commercial scale activities

Challenges of cleaner production:

develop improved means of assessing or quantitatively measuring the cleanliness of

processes or products

develop cleaner processes in terms of design by using different or purer raw materials or

by substituting non-toxic materials such as catalysts.

integrate technical, safety, environmental, economic objectives in process and product

design. Ensure that there are economic benefits specify appropriate system boundaries for analysis

manage existing plants and systems for cleaner performance and ensure continuous

improvement

use better techniques for design and revamping process plants

Need for sustainable engineering: due to human exposure to toxic substances in food, soil, water,

increased demand for energy for transport, manufacturing, heating and cooling, increased

demand for water for home, agriculture and industry, resource depletion, rising demand for land

usage.

Industrial Ecology: use of natural ecosystems as models for industrial activity.

Processes/Industries are viewed as interacting systems rather than isolated linear flow systems.

Industrial Symbiosis is an interactive network between two or more industrial facilities or

companies in which the wastes or byproducts of one become the raw materials for another.

Industrial symbiosis is a subset of industrial ecology with a particular focus on material and

energy exchange. Eg. recycling, water cascading, water substitution, steam/heat cogeneration.

Industrial ecology: understanding the impacts of industrial systems on the environment. Purpose

of IE is to have better use of materials and energy in industrial systems and to improve

efficiencies of industrial systems to better approach natural ecosystems.

Tools of IE:

Life Cycle Assessment - method of evaluating the environmental consequences of a

product or process from cradle or grave.

Design for Environment

Industrial Symbiosis


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Kalundborg Industrial Park as an example: the power station removes fly ash from the smoke to

reduce the emissions to the atmosphere. thus producing about 30000 tonnes of fly ash per year.

The ash is used in the cement industry as a cement-blending agent. Nickel and vanadium are

reclaimed from this ash.

Enzyme production at the Novozymes enzymes factory is based on fermentation of potato flour

and cornstarch. The fermentation process generates solid biomass and liquid biomass thatcontains nitrogen, phosphorus and lime as byproducts. After inactivation, this biomass can be

used as fertiliser in the fields.

The insulin production at the Novo Nordisk pharma factory produces yeast as a residual product

which is converted into a yeast slurry that is used as feed for pigs. Sugar water and lactic acid

bacteria are added to this yeast to make it more attractive to the pigs.

Results of the symbiosis: significant reductions of energy and utilities consumptions,

environmental improvements, conversion of traditional waste products, gradual development of

a systematic environmental way of thinking, creation of a positive image of Kalundborg as a clean

industrial city, non renewable water use has significantly reduced.

Characteristics of symbiosis system:

Participating industries must fit together but be different. The individual industry agreements are

based on commercially sound principles, environmental improvements, resource conservation

and economic incentives go hand in hand. The development of symbiosis has been on a voluntary

basis but in close cooperation with the authorities. Mutual management understanding and

cooperative commitment is essential. Effective operative communication between participants is

required. Significant side benefits are achieved in other areas such as safety and training.

Industrial Metabolism: by tracing material and energy flows and performing mass balances, wecan identify inefficient products and processes, determine the steps to reduce industrial waste

and pollution. No waste should leave the industrial system or negatively impact natural systems.

A change from linear (open) processes to cyclical (closed) processes so that the waste from one

industry is used as n input for another.

TYPE 1: linear process, Materials and energy leave as products or byproducts/wastes. Dependent

on a large amount of raw materials.

TYPE 2: some wastes are recycled or reused

TYPE 3: dynamic equilibrium of ecological systems, highly integrated, closed system. Only solar

energy would come from outside, while all byproducts would be constantly reused and recycled

within. Represents a sustainable state and IE.

Challenges and risks in IE: industries which are mutually exclusive cant work together. Industrial

systems may only be mildly transformed. Industrial ecology may reduce the ability of firms to

meet customer demand by restricting production or overproducing. IE may introduce risks to

operation of individual plants if key facilities in the IE system are unreliable. The cooperation


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required in IE may be difficult to achieve in a business context as managers are more familiar

with competition than cooperation.

Complications of IE: companies that are using each others residual products as inputs face the

risk of losing a critical supply or market if a plant closes down or changes its product mix.

Proprietary information could become available to competitors. Uneven quality of byproductmaterials could cause damage to equipment or the quality of products. Exchange of byproducts

could lock in continued reliance on toxic materials. Possible innovations in regulation to enable

EIP development may not be allowed by regulatory agencies.

Scale of systems:

Microscale: individual process or section of a process plant

Mesoscale: petrochemical complex or a petroleum refinery operating on a large site.

Macroscale: flow of industrial materials between diverse industry sectors such as power

generation, chemical manufacture, mineral processing, paper manufacture

WEEK 8 TUTE

1. What are the different stages of LCA and what is done at every stage?

Goal and scope definition (scope and purpose is defined, system boundaries, functional unit),

Inventory analysis (all material and energy resources consumed are quantified, all wastes

emitted are also quantified), impact assessment (inventory data are grouped according to

categories of specific environmental effects or impacts, they are then weighted to provide a

numerical score), interpretation (improvement in the processing or product use are identified).

2. What are the different environmental impact categories within inventory analysis of LCA and

identify their burdens in each category?Includes all relevant stages in the life of a product: raw materials/energy needs, manufacturing,

transportation, storage, distribution, use, reuse, maintenance, recycling and waste management.

The burden of the sub system on the environment = burden from activity*mass or energy flow of

that sub system.

3. Identify the equivalent factors for the categories below:

a) Global warming potential

b) Acidification

c) Eutrophication

d) Ozone depletion

e) Photochemical ozone formation

4. What are the advantages of performing LCA?

5. What are the drawbacks of LCA study?


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6. When is the first time LCA was started and what was it for?

7. In 1969, the LCA study was performed by a famous soft drink company. Which is the company

and what was it for?

8. What are the different types of software which can be used in LCA study?

9. Draw a simplified LCA diagram of a coffee-machine.


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WEEK 9

Biofuels are derived from biological feedstock. Can be used for transportation, power generation,

heating.

Principle objectives of using biofuels: reduce GHG emissions from transport, enhance the security

of supply, increase employment, especially in rural areas.

First generation feedstocks: food crops such as corn, rapeseed oil, sugar beet, sugar cane, palm

oil. Produced from conventional food crops. The starches and sugars produce bioethanol while

the oils and fats produce biodiesel.

Advantages: familiar feedstocks, well-established production methods, scalable processes, fuels

compatible with fossil fuels and there is commercial production and use in many countries.

Disadvantages: competition with food crops, high cost feedstocks can lead to high production

costs, modest reductions in fossil fuel use and GHG emissions due to land use change, production

of byproducts.

Second generation feedstocks: energy crops such as miscanthus, poplar, willow and wastes suchas food waste, manure, straw, waste wood. Produced from nonfood sources. The waste biomass is

generally preferred as there is no additional stresses on the environment. Produced in two main

routes:

Thermochemical - carried out at high temperatures and sometimes high pressures.

Analogous to chemical/fossil fuel processing

Biochemical - includes processes used in first generation biofuels such as chemical and

biological conversion but also includes anaerobic digestion to produce biogas.

Advantages: similar processes to petroleum/chemical/bio industries. There is no competition

with food. There is a reduction in the amount of waste that needs to be disposed of or treated.

Disadvantages: unfamiliar feedstock and uncertain fluctuating availability. High capital andenergy costs. Processing is not optimised for new feedstocks. Competition for land and water for

some energy crops. For anaerobic digestion, only a fraction of the waste produced can be used.

For non-liquid fuels, compatibility with existing transport vehicles is a significant problem.

Third generation feedstock is microalgae. The algae is cultivated in purpose built systems such as

fermenters, photo-reactors or ponds or is harvested from oceans. It has a similar processing

route to the second gen biofuels.

Advantages: microalgae has a high oil content. Can be cultivated in a range of systems, including

contaminated water, wide spectrum of processing routes and biofuel products.

Disadvantages: not commercially available yet, high initial costs to establish algae production

systems. High water content required. If cultivated artificially, it could require large areas and the

growth rate is limited by the rate of insolation. If exploited from oceans, it could impact on

marine life and ecosystems.

Sustainability assessment: biofuels reduce GHG emissions as the CO2 is considered carbon

neutral with biomass. Could be an attractive option due to the security of supply and may

stimulate rural development. The only disadvantages are the additional land requirements and


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competition with food production systems. The land usage change could increase GHG emissions

and there is a high capital and operating cost. Could also be some social issues such as health and

safety, land rights, child labour.

Sustainability issues:

1. Environmental - global warming potential, land availability and land use change,biodiversity, water consumption, other environmental impacts

2. Economic - feedstock costs, investment costs, biofuel price, local income generation

3. Social - human health, human and labour rights, land ownerships, impact on food security,

community development, impact on indigenous people

Economic sustainability of biofuels:

costs of feedstock, cultivation, preparation, delivery

capital costs for biofuel manufacturing plants to convert feedstock into biofuels

other costs such as labour, utilities, maintenance, insurance

The capital costs are uncertain due to many factors. The thermochemical plants appear to be themost economically sustainable option. Integration of biofuel facility into existing refinery or

chemical plant can be the most cost effective option. Competition from fossil fuels is very

significant - rising crude oil prices can make biofuels a more economically attractive option.

Social sustainability of biofuels: increase rural development, improve welfare, infrastructure,

reduce poverty, etc. Biomass production has a range of social impacts including human health,

human rights and labour rights, land ownership, community development, impact on indigenous

peoples. The areas of high biomass production are often areas of low wealth/earnings.

Recycling - major need as landfilling represents loss of land that can be used for other purposesand waste of resources. Recycling can lengthen the lifespan of existing landfills, reduces resource

consumption and need for new landfill sites.

Recycling materials in a chemical reaction - the unconverted reactants are returned to the reactor

which would reduce raw material usage and waste emissions to the environment.

Implications of recycling process streams: the recycled material must often be pumped or

compressed to reactor feed pressure. Material losses may be incurred through imperfect

separations and from purge streams.

Economics of recycling streams: Advantages include a reduction in raw materials consumption

and reduction in waste treatment or disposal. Disadvantages include possible additional

separation processes and the compressing/pumping of recycled materials.

Economics of recycling depends on the value of the material recovered, cost of recovering and

reprocessing, cost of disposing the untreated recyclable material.

Closed loop - when a used product is recycled into a similar product such as glass, metal and

plastic.

Open loop - material from one production sequence is recovered, reprocessed and fed into a

different and often unrelated production sequence to make a saleable product.


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Origin of waste:

producer waste - generated through production process, relatively clean, free of

contamination and known composition

post-consumer waste - generated by households, commercial establishments and

institutions. Mainly solid, its composition can vary depending on its source and canchange over time. Often contaminated/mixed.

Waste reduction hierarchy: reduction, reuse, recycle, recovery

Benefits of plastic use: lighter weight than competing materials, reducing fuel consumption

during transportation. Extreme durability, resistance to chemicals, water and impact. Good safety

and hygiene properties for food packaging, excellent thermal and electrical insulation properties,

relatively inexpensive to produce.

Why bother recycling? plastics have a short life span, with early disposal from the consumer

often within weeks of manufacture. Most plastics are disposed of at landfill sites, chemicalstability of plastics has contributed to finding more landfill sites

WEEK 9 TUTE

1. Define industrial ecology using reference to how it handles material and energy flows.

Industrial ecology takes advantage of the cyclic flows of materials and energy through the design,

redesign and management of eco-efficiency industrial systems.

2. Explain how industrial symbiosis can work to reduce the overall material and energy

requirements for a network of industrial systems.

By utilising wastes from one plant/system as feedstocks for another plant/system. Industrialsymbiosis reduces the need for materials or energy from elsewhere.

3. Draw a diagram of the Kalundborg Industrial Park. Show the flows of key energy and material

streams between different industries in the Park. What are the central players in the Park and

how might they represent a risk to the operation of the Park?


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The central players are the power station and the oil refinery because these two facilities supply

or receive the bulk of the material/energy flows from other parts for the park.

They represent a risk because if either the refinery or the power station stop working, then other

parts of the system need to either stop operating or fall back in alternative supplies of energy and

materials. This increases the operating risks of other plants.

4. What are the characteristics of an industrial symbiosis system?

A symbiosis system:

the participating industries must fit together but be different.

the individual industry agreements are based on commercially sound principles

environmental improvements, resource conservation and economic incentives go hand in

hand

the development of the symbiosis has been on a voluntary basis but in close cooperation

with the authorities

short physical distances between participating plants are an advantage

short mental distances are equally as important

mutual management understanding and cooperative commitment is essential

effective operative communication between participants is required

significant side benefits are achieved in other areas such as safety and training

5. Explain Type 1, Type 2 and Type 3 systems in the context of Industrial Ecology. Which type is

Kalundborg Industrial Park?


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Type 1: represent a linear once through flow of materials and energy, relying on unlimited

supply of materials and energy and producing unlimited wastes.

Type 2:introduces some cyclic flows of materials and energy through industrial symbiosis. This

reduces the call on raw materials/energy and reduces wastes.

Type 3: ideal situation which is only seen in natural ecosystems. All material flows are cyclic with

no raw material requirement and no wastes. Only energy is required from outside the system(which would be sunlight in the case of natural ecosystems)

6. Name 3 key challenges to Industrial Ecology.

industries that are mutually exclusive cant work together on IE

industrial systems may only be mildly transformed. further transformation within

individual plants is still possible

industrial ecology may reduce the ability of firms to meet consumer demand by

restricting production or overproducing

IE may introduce risks to operation of individual plants if key facilities in the IE system

are unreliable the cooperation required in IE may be difficult to achieve in the business context as

managers are more familiar with competition rather than cooperation


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WEEK 10

High demand for electricity impacts:

Environmental: greenhouse gas emissions, acidification, heavy metal air emissions,

resource extraction impacts, waste production

Social: political instability around access to resources and financing conflict, energy

poverty for low income countries Economic: rising prices for energy as fuels become scarcer, resource depletion affecting

economic equity for future generations, opportunity costs - spending money on energy

that could be spent on other productive activities

Options to reduce the problems created by the rising electricity demand: use less electricity,

constrain lifestyle and industrial growth in developing countries, generate more electricity from

renewable sources, generate energy from existing energy sources more efficiently by using less

fuel or produce more electricity from the current fuel usage.

Fuel Cell: an electrochemical device that converts chemical energy in a fuel directly into DCelectricity. Waste heat is a byproduct which is usually much less than from a heat engine. Consists

of two electrodes separated by an electrolyte. The electrolyte allows the reduction and oxidation

reactions that occur. The fuel reacts at the anode and produces a source of electrons. The ionised

fuel moves across the electrolyte to the cathode while the electrons travel via an electric circuit to

the cathode. Oxygen combines with the ionised fuel at the cathode.

The voltage of a single fuel cell is limited by the standard electrode potentials of each half

reaction. To achieve a higher voltage, the fuel cells are combined in series to achieve higher

power outputs. Known as a fuel cell stack.

The enthalpy change can only be partly transformed into electrical energy. The maximumpossible electrical energy obtained is given by the change in Gibbs free energy of formation.

Thermodynamic efficiency = deltaG/deltaH = 1-TdeltaS/deltaH

The efficiency of the fuel cell decreased as temperature rises

Benefits of a fuel cell: no moving parts, no mechanical wear and tear, very quiet and no

lubrication required, heat is not required, though it is a byproduct, unlike heat engines, the

efficiency of energy conversion is not limited by the carnot efficiency, fuel cells are more efficient

at lower temperatures

Advantages and applications of fuel cells:

efficiency advantage - higher conversion of chemical to electrical energy

the electrochemical nature of the reaction and necessity for very clean fuel means that the

fuel cell has low emissions. They also produce less life cycle CO2 emissions even if the

hydrogen is derived from fossil fuels. Emissions advantage

stationary applications - small scale domestic energy supply, larger units can be used for

combined heat and power, large systems for industrial cogeneration


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mobile applications - potential to replace batteries in electrical vehicles, increasing

driving range and allowing more rapid fuelling compared to recharging batteries

portable applications - can replaces rechargeable batteries or diesel generators for

remote sites, building sites and similar duties.

Fuel cells for distributed power generation: fuel cells can be used for generating electricity nearor at the location of the end user rather than in large centralised power stations. Might be more

sustainable than conventional power plants. Concentrates on Combined Heat and Power (CHP).

Need to consider the environmental, economic and social dimensions of sustainability.

Environmental Considerations: assume that the fuel cells will use hydrogen from natural gas.

Emissions of CO2 and CH4. Need to compare fuel cells with the conventional energy systems. An

LCA can be used to get GWP from both systems. Functional unit would be 1kWh of electricity

generated.

Economic and social considerations: current fuel cells are expensive. This high cost is due to lowproduction volumes and the lifetime of operation is also unclear. The public are more likely to

accept a home power plant. The costs make it prohibitive which contributes to the reliance of

society on centralised electricity generation.

Municipal Solid Waste Management:

Increasing amount of MSW means that a larger amount of space is required for storage and

disposal. Landfill generates CO2 emissions and methane emissions. Chemicals might leach into

groundwater and the soil. Unnecessary waste of potentially valuable resources that could

otherwise be recycled or recovered to produce energy. In australia, environmental laws have

made it very hard to dispose of things like batteries, waste oil, non-biodegradable plastic bags,tyres, etc.

Solid waste management hierarchy: reduction, re-use, material recovery, energy recovery, final

disposal.

Energy from waste plant sustainability considerations: waste handling, reception and

pretreatment, incinerator, boiler, energy recovery and generation plant, air pollution, ash

treatment, socioeconomic considerations. Need to consider the waste composition and energy

content as well as the incineration technology and energy recovery system.

Types of Incinerators:

mass burn plants - two or three combustion units, accepts waste of little preprocessing,

generates heat and electricity

Modular plants - small capacity burning, produces steam as the only form of energy

output. Lower capital costs, good for small communities

Refuse-derived fuel (RDF) plant - generate electricity, highest capital cost,


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Pyrolysis and gasification - heating without and less oxygen. Materials and energy

recovery

Design of incinerators:

moving grate or mechanical stoker - the moving grate pushes the waste into the

incinerator and deposits the ash to the bottom of the incinerator. Most dominant designfor use in mass-burn plants

fluidized bed - furnace contains a bed of sand on an air distribution system, air keeps the

sand and waste mixing to increase combustion efficiency. Suitable for RDF.

Rotary kiln - waste is rotated in a cylindrical furnace, air supply through perforation for

complete combustion. Not widely used as it is the most turbulent system.

Air pollution and control:

Primary measure - reduced by controlling the combustion conditions in the furnace and

reboiler eg. supply of primary and secondary air to control CO, NOx. Can also be done by

controlling the temperature and residence times in the combustion chamber, boiler andflue treatment units to prevent nox and dioxins.

Secondary measure - cleaning up the air pollution from incineration. Scrubbers for the

removal of acid gases, cyclones or electrostatic precipitators for fly ash removal, activated

carbon for removal of heavy metals, selective catalytic reduction with ammonia for NOx.

Ash treatment - fly ash is in the flue gas, prone to leaching and therefore need secure landfills.

The bottom ash can be used for road construction.

Legislation - integrated pollution prevention control directive, environmental impact assessment

directive, landfill directive, ambient air framework directive

Socioeconomic impact - internal costs are the direct cost of running the incineration. Externalcosts include the environmental damage. Generally, incineration is better than landfills for

environmental and society

WEEK 10 TUTE

1. Explain the difference between 1st, 2nd and 3rd generation biofuels.

Difference is based on the feedstock used. 1st gen uses food feedstocks, 2nd gen uses waste

biofeedstocks or non-food crop feedstocks and 3rd gen uses microalgae feedstocks.

2. Name three key products that can be produced from bio-feedstocks.

Bioethanol, biodiesel, syngas, synoil, biogas.

3. Why is land-use change a critical component of the life cycle GHG emissions from certain

biofuels?

Land use change includes factors such as CO2 and methane being released from natural forests or

grasslands which are removed and can dominate the life cycle GHG emissions for biofuels.

4. 1st and 2nd generation biofuels have a key disadvantage in that they compete with food crops.


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Explain the social and economic impacts of this competition.

Competition with food crops can result in a reduction in the supply of food to market, resulting in

higher food prices. It also reduces food supply to animal producers, raising meat and dairy prices.

This can have significant social impacts in poorer areas where food costs dominate a familys

budget.

5. Life cycle GHG emissions from corn-derived ethanol can be worse than those from fossil

derived petrol, despite being produced from a biological feedstock with no net CO2 emissions

from combustion of the fuel. How is this possible?

Corn bioethanol can have high life cycle GHG emissions due to the large amount of fertiliser

required. Fertiliser production produces CO2 and CH4 emissions from combustion to drive

processes to produce the fertiliser. The breakdown of these fertilisers also produces a lot of N2O

which further increases GHG emissions from corn.

6. Biofuels also have some key social impacts. Name three of these and explain how they may

be of interest to policy makers (i.e. governments).Social impacts: increased rural development for the cultivation and processing of biofeedstocks.

Impact on food security and affordability. Impact on indigenous peoples who may be displaced by

biofeedstock production. Impacts on land ownership and human rights. Impacts on labour rights,

particularly in developing countries.


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WEEK 11 = REVISION TOPICS

Intro to sustainability concepts, sustainable development

Cleaner Production

PFD development - flowsheeting, fuels, steam/heating, cooling utilities, electricity

Waste identification and minimisation - reactors, separation processes, startup shutdown,

maintenance, abnormal operationEconomics - capital and operating costs, externalities, environmental cost factors

Life cycle assessment

Industrial ecology and industrial symbiosis (plus case study)

Materials recycling

Greenhouse gas measurement and reporting

Case Study 1 - sustainability assessment of biofuels

Case study 2 - sustainability of energy from waste

Case study 3 - fuel cells in distributed generation

WEEK 11 TUTE1. Draw a flow diagram of a typical EfW facility and describe each part.

MSW discharge - MSW is delivered by road/rail/other means

MSW storage

Incinerator - location within the plant where combustion occurs

Boiler - heat exchanger between the hot flue gas and water to make steam

Turbine - converts steam enthalpy into mechanical work

Generator - converts mechanical energy to electrical work

Water loop - cools the steam condenser to provide waste heat rejection point to increase the

electricity generation efficiency. Also acts as a way to take waste heat to an end user eg a town

Bottom ash - heavy ash yield from the combustion. Contains non-combustibles, unburnt carbon


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Activated carbon - secondary pollution control of dioxins and heavy metals

Fabric filter - secondary pollution control of fly ash

2. Why is a combined heat and power plant so much more efficient than an electricity-only plant?

Why do you think CHP plants are still comparatively uncommon, despite this efficiency

advantage?CHP plants enable the waste heat as well as the electricity to be more effectively used. More of the

fuels energy content is actually being used up and ends up serving people. In electricity-only

plants, the waste heat is thrown away. CHP plants are comparatively uncommon as they are more

expensive.They also require the generation to occur close to the end users. People would not

want this close to their homes which is why CHP is uncommon.

3. List the main incineration technologies and describe the suitability of each depending on the

waste to be treated.

mass burn plants - two or three combustion units, accepts waste of little preprocessing,

generates heat and electricity Modular plants - small capacity burning, produces steam as the only form of energy

output. Lower capital costs, good for small communities

Refuse-derived fuel (RDF) plant - generate electricity, highest capital cost,

Pyrolysis and gasification - heating without and less oxygen. Materials and energy

recovery

4. List the air pollutants generated by incineration of MSW. Describe how each of these pollutants

is formed in the plant.

Dust, SOx, NOx, CO, organic vapours (VOCs), heavy metals, CO2, water vapour. Combustion forms

CO2, CO, SOx and water vapour. The acids, HF and HCl are formed between water and F/Cl at hightemperatures. The heavy metals present in the fuel are liberated by burning. Dioxins/furans are

formed by reactions with chlorine in the fuel

5. What methods are available for primary and secondary treatment of the air pollutants in

the previous question?

Primary treatment - control of incinerator conditions - excess air, mass rate of fuel, temperature

control, residence time. Secondary treatment involves activated carbon, fabric or other filters,

scrubbing of NOx, acid gas scrubbing.

6. Emissions from dioxins are one of the main objections of the public to incineration and EfW

plants. However, dioxins are also emitted from open fires, such as home fireplaces. It is known

that the human health effects of fireplaces are greater than that from incinerators. Why do you

think people accept this health risk and yet they object to incinerators?

People are more likely to not object to data when it makes them feel good. Fireplaces bring about

positive human emotions and are a pre-industrial piece of technology. New heavy industry

technology often arouses suspicion, even if their effects on pollution are lower.


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7. Show that burning 28.6 tonnes/hour of waste with a LHV of 9800 kJ/kg will release 77.9

MW of heat.

28.6 t/h/3600*1000 = 7.944 kg.s.

Energy = EC*mass rate = 9800*7.944 = 77855kJ/s= 77.9MW.

8. If the EfW plant is generating 20 MW of electricity and 15% of that is used to run the plant,calculate the net export of electricity from the site.

85% of generated electricity is sent out. 0.85*20 = 17 MW sent out

9. Explain in basic terms how a fuel cell works. What distinguishes fuel cells from heat engines as

a means of producing electricity?

Fuel cells divide the electrochemical half-reactions of a fuel and oxygen so they occur at the

anode and cathode respectively. This is possible because the electrolyte only allows the flow of

ions and not the direct contact of fuel and oxygen. Fuel cells provide electricity directly through

the electrochemical reaction, rather than requiring a two step process of producing heat through

combustion followed by a heat engine to convert that heat into work.

10. How does operating temperature influence the efficiency of a fuel cell? Given that some fuel

cells require elevated temperatures to enable the initiation of the electrode reactions, how does

this influence the selection of the fuel cell type?

The fuel efficiency drops as temperature rises. Higher temperatures however are needed to

enable the half reactions to get started at the anode and the cathode. So there is a compensating

trade off. Catalysts can reduce the operating temperatures required to get the reactions to occur

but these generally cost a lot more as they are made from precious materials such as platinum.

11. Why do distributed electricity generation systems (such as fuel cells) reduce transmissionand distribution losses?

Producing electricity close to the point of use means that there is a shorter distance for the

electricity to travel. This means less resistance losses and also fewer losses from multiple voltage

transformations.

12. Over the life cycle of a PEFC, where do the majority of greenhouse gas emissions occur?

What might be done to render these greenhouse gas emissions as close to zero?

Most life cycle GHGs are from the CO2 made in the fuel cells reformer - reforming fuel to make

H2 with CO2 as a byproduct. You could reduce these byproducts by using methane from a

biogenic source such as landfill gas or something derived from biomass. Biogenic fuel sources are

taken to have zero effective GHG emissions because the CO2 from their use is simply returning

the CO2 back into the atmosphere from where it was taken when the biomass was formed.

Another method is to produce H2 directly through the electrolysis of water, using a renewable

source of energy such as wind or solar. In this case, you could directly store the electricity in a

battery rather than making H2 and then using a fuel cell to convert it back into electricity.


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13. Heat is a coproduct of fuel cell operation. If a heat user is not located nearby, how would the

impact the efficiency of the fuel cell?

If no heat user is available nearby, the heat will have to be thrown away. This will therefore not

be a CHP operation and the efficiency will only include the electrical energy. This efficiency will

therefore be much lower. CHP is critically dependent on the heat users being located close to the

fuel cell.

14. Electricity and heat are not considered equivalent in terms of allocating the impacts of the

fuel cell between the two products. Why not?

There are many limitations with converting heat into work and we know that the potential to do

work for a unit of heat is limited by the carnot efficiency. Eg. 1 unit of heat at 80 C with a sink

temp of 15C can only be converted to work at an efficiency of 18.4% in a perfect reversible

system. Therefore 1 unit of work is only worth 0.184 units of work. 1 unit of electricity however

can be theoretically converted fully into other forms of work.

Allocation of a fuel cells impacts needs to fairly attribute the impact to the useful energy which

means converting the heat to work potential first.

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Che 3163 Sustainability Notes