Environmental and economic modelling: A case study of ... and... · Environmental and economic...

Resources, Conservation and Recycling 49 (2007) 244–263

Environmental and economic modelling: A casestudy of municipal solid waste management

scenarios in Wales

Andrew Emery a,∗, Anthony Davies a,1,Anthony Griffiths b,2, Keith Williams b,3

a eCommerce Innovation Centre,Cardiff Business School, Cardiff University, Cardiff CF24 4AY, United Kingdom

b Cardiff School of Engineering, Cardiff University, Cardiff CF24 3AA, United Kingdom

Received 22 March 2006; accepted 24 March 2006Available online 2 May 2006

Abstract

In recent years the burdens that waste puts on the environment has been widely publicised. Toaddress the earth’s dwindling resources and the growing mountains of waste many countries haveintroduced statutory waste minimisation and recovery targets. The general public are generally moreconcerned with the effects that waste has on the environment. Whereas waste managers and plannersneed to consider the financial costs of collection, processing and disposal. This paper investigatesand reports on the findings for both of these areas of concern. A case study area in a typical SouthWales valley location was selected to model the environmental and economic impacts of a numberof waste disposal scenarios. The environmental impacts of a number of waste management scenarioswere compared using a life cycle assessment (LCA) computer model. An interactive microsoft excelspreadsheet model was also developed to examine the costs, employment and recovery rates achievedusing various waste recovery methods including kerbside recycling and incineration. The LCA analysisshowed the incineration option to be more favourable than the landfill and recycling/compostingoptions. However, the economic modelling results showed higher running costs and lower associatedjobs when compared to the other options such as recycling. The paper concludes by suggesting that

∗ Corresponding author. Tel.: +44 29 2064 7028; fax: +44 29 2064 7029.E-mail address: [email protected] (A. Emery).

1 Tel.: +44 29 2064 7028; fax: +44 29 2064 7029.2 Tel.: +44 2920 874316; fax: +44 2920 874716.3 Tel.: +44 2920 874847; fax: +44 2920 874716.

0921-3449/$ – see front matter © 2006 Elsevier B.V. All rights reserved.doi:10.1016/j.resconrec.2006.03.016

mailto:[email protected]

dx.doi.org/10.1016/j.resconrec.2006.03.016

A. Emery et al. / Resources, Conservation and Recycling 49 (2007) 244–263 245

integrated waste management will ultimately be the most efficient approach in terms of both economicsand also environment benefits.© 2006 Elsevier B.V. All rights reserved.

Keywords: Life cycle assessment; Economic model; Municipal solid waste; Waste management

1. Introduction

What is the correct balance between environmental, economic, technical, social andregulatory factors of one waste treatment system compared to another? What is the correctmix of waste recycling, composting, reduction and recovery options? These are some of thekey questions that should be addressed before commencement of any waste managementoperation. For such a system to be truly effective it needs to be environmentally sustainable,economically viable and socially acceptable (Nilsson-Djerf and McDougall, 2000). A studyconducted by Morrissey and Browne (2004) concluded that no computer software wastemanagement tools currently integrate all three aspects so and so cannot be considered fullysustainable.

There is no escaping the fact that today’s society has a throwaway culture, producingvast quantities waste. Advances in environmental measurement techniques have shown thatthe current demand on the earth’s resources is not sustainable and needs addressing imme-diately (York et al., 2004). The last 20 years, for example, has seen a substantial increase inthe use of plastic packaging. Before this time many products such as foodstuffs were pur-chased loose or in reusable containers. Factors such as the continuing strength of the UKeconomy, high consumer confidence, low interest rates and low unemployment has resultedin increased consumer spending and ultimately an increase in the amounts of householdwaste produced. To try to combat the increasing levels of waste the European Union (EU)Landfill Directive was introduced in 1999, which set ambitious targets for the reduction ofbiodegradable municipal waste sent to landfill (European Parliament and Council Directive,1999). Subsequently, waste targets for England and Wales were introduced in 2000 and2002, respectively, which concentrated on recycling, composting and energy from waste(EfW) technologies for the recovery of municipal solid waste (MSW). MSW is the wastecollected by a local authority, which consists mainly of household waste, but also containsa range of other wastes such as trade waste and street sweepings. Household waste makesup about 85–90% of the total MSW content for the majority of local authorities in the UK(Environment Agency, 2003).

This paper examines the environmental and economic impacts of a number of wastedisposal systems used in a typical South Wales valley location. To undertake this inves-tigation a case study authority was selected, this being Rhondda Cynon Taf CountyBorough Council. A number of waste management scenarios were compared using theLCA computer model known as ‘Waste Integrated Systems Assessment for Recoveryand Disposal’ (WISARD) to model the environmental impacts. The scenarios modelledwere based upon the EU Landfill Directive targets for MSW using data collected froma number of household waste classification exercises and a desk study of the case study

246 A. Emery et al. / Resources, Conservation and Recycling 49 (2007) 244–263

area. An interactive microsoft excel spreadsheet model was also developed to examinethe costs, employment and recovery rates achieved using various waste recovery meth-ods including kerbside recycling and incineration. The model produced estimations of therealistic costs (gross and net) that would be incurred as a result of implementing differentwaste management scenarios. Varying household participation and recovered recyclablematerials rates were calculated. Local employment generated as a direct result of thesescenarios was investigated as well as the costs of complying with the proposed Waleswaste recovery targets. The model inputs were based on a waste classification exercisewhich was conducted to determine the composition of household waste (Emery et al.,2000).

2. Theoretical background

The life cycle of a product initially starts from the point when raw materials are extractedfrom the earth, followed by manufacturing, transport and use. The life cycle of the productends with waste management, which includes recycling, composting, EfW and final dis-posal. At every stage of the life cycle there are emissions and consumption of resources.Efficient planning for municipal solid waste management systems requires accounting forthe complete set of environmental effects and costs associated with the entire life cycle ofMSW. A LCA is a process used both to evaluate the environmental burdens associated witha product, process or activity and to consider opportunities that can effect environmentalimprovements. The International Organisation for Standardisation (ISO), a worldwide fed-eration of national standards bodies, has standardised this framework within the ISO 14040series on LCA (Standards ISO, 1997). While LCA use for waste management decision-making is constantly increasing in the UK there are still a number of barriers that hinderits widespread acceptance. The main barriers are a lack of awareness of the importance ofusing the life cycle concept, the quality of the data and a general lack of understanding ofhow to conduct a LCA correctly and interpret the results.

In terms of economics, the costs of diverting waste from the traditional practice oflandfilling are largely determined by a number of factors. One of the main challenges fora local authority in trying to achieve recovery targets through recycling composting andEfW are to reduce costs whilst maintaining customer satisfaction. The costs of collectingand sorting/processing of materials need to be considered for which there are numerousvariables. It has been estimated that the total cost of collection and disposal of MSW inEngland and Wales for 2000/2001 was about £1.5 billion (Defra, 2002).

The majority of households in the UK have recyclables collected via kerbside collectionschemes (National Statistics, 2005). Recyclable materials such as non-ferrous metals ordense plastics have a higher market value than materials such as paper or green waste.Paper and green waste make up a large proportion of the waste stream by mass and so arepopular materials for collection when taking into consideration recycling targets (Defra,2005). Dense plastics which include drinks bottles only take up a small proportion of thewaste stream by mass but a high proportion by volume. There are numerous designs ofvehicles for sale or for hire, used in the UK for collecting recyclables which can vary quitewidely in price. Variables such as the number of people per vehicle employed to collect


the recyclables, wages, vehicle storage capacities and compaction ratios need to be takeninto consideration. Recyclable materials collected in bags tend to be sorted at a materialsrecycling facility (MRF). A typical MRF is normally comprised of a mixture of manual andmechanised sorting operations. Recyclables sorted at the kerbside tend to go to a storagefacility where they are simply bulked up before being transported to a reprocessor. Theeconomies of scale to be gained from MRFs and other waste management processes suchas EfW plants need to be taken into consideration.

The scenarios modelled in this report are based upon several drivers for waste reductionin the UK. These are the EU Landfill Directive targets (European Parliament and CouncilDirective, 1999) for MSW and Wales’s recovery targets for MSW set out in Wise AboutWaste (National Assembly of Wales, 2002). The EU Landfill Directive, was adopted on 26April 1999 and came into force on the 16 July 1999. The obligatory targets will mean thatby 2010 the UK and other countries in the EU will have to reduce the biodegradable fractionof municipal waste sent to landfill to 75% of the 1995 level. Similarly, this will have to befurther reduced to 50% by 2013 and to 35% by 2020. The Welsh Assembly Governmentpublished a National Waste Strategy for Wales ‘Wise About Waste’ in 2002, which seeks toensure compliance with the European Directives on waste management. The targets statethat by 2003/2004 a minimum 15% of MSW must be recycled/composted with a minimumobjective for each category of 5%. The target then increases to 25% by 2006/2007 with aminimum objective for each category of 10%. The final target is set at 40% by 2009/2010with a minimum objective for each category of 15%.

3. Case study area

3.1. Introduction

A large proportion of the LCA and economic modelling calculations in this paper arebased on data that was collated from a case study area, a local authority based in SouthWales known as Rhondda Cynon Taf County Borough Council. The case study area has apopulation of about 240,000, which makes up 8% of the total Welsh population with around100,000 households (National Statistics, 2001).

3.2. Waste arisings in the case study area

Local authorities in Wales have a statutory obligation to collect and dispose of householdwaste (National Assembly of Wales, 2002). The most recently published figures for Walesfor 2004/2005 showed an average MSW recycling/composting figure of 21.7% (NationalStatistics, 2005), a great improvement on the 1996/1997 figure of just 3.8% (Defra, 2002).The recycling/composting rate for the case study area for the period 2004/2005 was lowerthan the Welsh average at 15.6% (National Statistics, 2005). The recycling rate for Eng-land for this period was 23% (Defra, 2005). The total amount of MSW produced inWales increased from 1.39 million tonnes in 1996/1997 to 1.94 million tonnes in 2004/2005(National Statistics, 2005). The case study local authority collected a total of 101,000 tonnesof MSW of which about 91,000 tonnes was household waste.


3.3. Waste recovery in the case study area

In January 2002, Rhondda Cynon Taf County Borough Council launched its roll outweekly kerbside recycling scheme to 28,000 households in the case study area (Emery etal., 2003). The materials chosen for collection for the kerbside scheme were paper andcardboard, dense plastics, metal packaging (beverage and food cans), ‘kitchen’ and gardenwaste and glass. Three different methods of storing recyclables were originally trialled asthese the most popular schemes across the UK. These were a box scheme, the re-use ofsupermarket bags and a clear bag scheme of which the clear bag scheme proved the mostpopular (Woollam et al., 2004). The clear bag recycling scheme is currently available totwo-thirds of households in the case study area.

3.4. Household waste analysis

To accurately conduct a LCA or an economical analysis of a waste management sce-nario, the quantities of waste materials disposed of by a typical household needs to beestablished. Household waste composition and weights are subject to a number of fluctua-tions throughout the year. The most significant weight change that would be expected andhas been recorded in previous waste studies is garden waste (National Assembly for Wales,2003). To gain an insight into weight variations, monthly tonnage data were analysed forhousehold waste arisings over a 6-year period (Emery et al., 2000), from 1995 to 2000 forthe case study area. The average increase in household waste arisings over the 6-year periodwas found to be 1.96% per year. The Government’s predicted annual domestic increase iscommonly thought of being in the region of between 1 and 3% (DETR, 2000) which agreeswith the case study area waste analysis. It was interesting to note that the population in thecase study area actually dropped by about 1.3% between 1991 and 2001 (National Statistics,2001) even though the waste arisings increased. This clearly showed that households dis-posed of more waste in 2000 than 1995 and that the increase in waste arisings was a not aresult of an increase in population.

A full household waste analysis was conducted over a 3-week period in June 2000 todetermine the quantities of waste materials produced in the case study area (Emery et al.,2003). Table 1 shows the results of the waste analysis and also a breakdown of the materialsthat would be expected from a 101,000 tonnes of MSW (the waste generated in the casestudy area).

4. Life cycle modelling

4.1. Introduction

The WISARD LCA tool was developed for the Environment Agency by the EcobilanGroup and utilises a range of data, much of which was collected under the Agency’swaste research programme (WS Atkins Environment, 1997). WISARD was officiallylaunched on the 9 December 1999. It was designed so that those making waste managementdecisions such as local authorities can use the LCA approach to aid in the development


Table 1Breakdown of waste components found in 101,000 tonnes of MSW

Material Percentage Mass (tonnes)

Ferrous metals 4 4040Fines 6 6060Glass 7 7070Miscellaneous combustibles 5 5050Miscellaneous non-combustibles 6 6060Non-ferrous metals 1 1010Paper (total)/recyclable element 25 25250Plastic dense 6 6060Plastic film 4 4040Putrescibles (green waste) 32 32320Textiles 4 4040

Total 100 101000

of such activities as waste management strategies. This is achieved by considering theenvironmental effects of different options for managing MSW such as an integratedapproach and understanding where the main environmental effects of the chosen wastemanagement systems arise. The tool enables the user to model existing and theoreticalwaste management systems for operations such as landfill, recycling, composting andEfW. The tools underlying software platform and interface is also used by Eco-Emballagesin France, by the Scottish Environmental Protection Agency (SEPA) and by authoritiesin New Zealand. In each case, separate databases have been employed to reflect nationalcircumstances, including energy sources. To date WISARD has been used by many localauthorities in the UK and by consultancies acting on their behalf.

Removing any waste material from the waste stream by recycling or composting wouldhave an influence on the composition of the waste subsequently sent either to landfill or,for example, energy recovery. A number of waste management options were modelled.The options consider a range of recovery methods that conform to the 2009/2010 Wales(National Assembly of Wales, 2002) and 2020 Landfill Directive (European Parliament andCouncil Directive, 1999) waste targets. The environmental impacts for present day wastearisings were considered and also the predicted waste arisings for 2020 assuming a 3% peryear increase. EfW (incineration) was considered as an option, but it should be noted thatthe only options available in the WISARD model database are for large scale facilities of250,000 tonnes capacity and greater. The case study area only produced 101,000 tonnes ofMSW in 2000/2001 although this would rise to 182,400 tonnes by 2020 if a 3% increaseper year is applied. Gasification would be suitable for smaller quantities of waste of about30,000 tonnes per year but this was not a modelling option available in the software tool.

4.2. Outline of options modelled

The following four waste management options were modelled:

• Option 1: A ‘Do Nothing’ scenario. This option considered 100% of the MSW recov-ered in the case study area being disposed of in a landfill site. This option considered


present day tonnages of MSW and also waste arisings for 2020 assuming a 3% per yearincrease.

• Option 2: Meet 2009/2010 Wales recovery targets. This option meets the Wise AboutWaste Wales recovery targets for 2010 through a combination of recycling and compost-ing. No thermal treatment was considered and all remaining MSW was disposed of in alandfill site. This option considered present day tonnages of MSW with no increase inwaste arisings and also waste arisings assuming a 3% per year increase.

• Option3: Meet 2020 Landfill Directive targets. This option meets the Landfill Directivetargets for 2020 through a combination of recycling, composting and EfW (incineration).All remaining MSW was disposed of in a landfill site. This option considered presentday tonnages of MSW and also waste arisings for 2020 assuming a 3% per year increase.

• Option 4: A ‘Burn All’ scenario. This option considered 100% of the MSW recoveredin the case study area sent to an incinerator. This option considered present day tonnagesof MSW and also waste arisings for 2020 assuming a 3% per year increase. This optiondoes not conform to the waste recovery targets but is able to meet the Landfill Directivetarget.

Table 2 shows the numbers of facilities and tonnages of waste required for each option.Based on typical capacities it was found that for Option 1 only one landfill site was requiredbased on no annual increase in waste arisings. Two landfill sites were required by 2020based on a 3% increase per year in waste arisings. Based on the limited choice of compostfacilities available in the model a large number of compost facilities were needed to satisfyOptions 2 and 3. Again due to the limited facility options available, only one incineratorwas required to process all the MSW for Option 4.

4.3. General assumptions

The majority of input data used to conduct the LCA for the different options was keptconsistent. The general assumptions used were as follows:

• The percentages of materials that make up MSW were kept consistent for all wastemanagement options. However, it should be noted that the composition of MSW couldchange significantly by 2020, for example, plastics packaging becoming even more pop-ular, replacing cardboard.

• The average distance travelled by a caged vehicle used to collect recyclables from thekerbside was estimated to be about 17,000 miles year. Each caged vehicle collected2 tonnes of recyclables per journey. A rigid 3.5–7.5 tonnes vehicle was chosen from thesoftware tool vehicle list to represent a caged vehicle.

• It was assumed that the overall population of the case study area did not increase overthe time period (2000–2020). This would result in no increases in the total numbers of‘wheelie’ bins, waste sacks and kerbside boxes.

• As there are currently no thermal treatment facilities in the case study area, one wasassumed to be located at either the same location as the landfill site or another site ofsimilar distance. In this way the distances travelled by collection vehicles would not varyand hence the results of the LCA modelling would be consistent. A ‘new 250,000 tonnesper year’ incinerator was chosen.

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Table 2Facilities data used for modelling of waste management options

Description Waste management facility

Landfill site MRF Well manageda Covereda Incinerator

Tonnes Number Tonnes Number Tonnes Number Tonnes Number Tonnes Number

Option 1 (100% landfill)101,000 tonnes (no increase) 101000 1 0 0 0 0 0 0 0 0182,400 tonnes (3% increase—2020) 182400 2 0 0 0 0 0 0 0 0

Option 2 (2010 Wales recovery targets)101,000 tonnes (no increase—2010) 60600 1 20200 1 17700 2 2500 3 0 0132,000 tonnes (3% increase—2010) 79000 1 26350 2 23200 3 3150 3 0 0

Option 3 (2020 Landfill Directive targets)101,000 tonnes (no increase) 56200 1 18400 1 19400 3 2600 3 4400 1182,400 tonnes (3% increase—2020) 84700 1 27400 2 40200 5 5300 5 24800 1

Option 4 (thermal recovery)101,000 tonnes (no increase) 0 0 0 0 0 0 0 0 101000 1182,400 tonnes (3% increase—2020) 0 0 0 0 0 0 0 0 182400 1

a Compost facility


4.4. Environmental effect categories

The outputs from each option modelled were analysed under five environmental effectcategories. These are also the key effect categories recommended in the software tool helpfile (Pricewaterhouse Coopers, 2006). The impact assessment categories chosen are asfollows:

• CML-air acidification. Some of the principle effects of air acidification include lakeacidification and forest decline. The two primary acidifying species are compounds ofsulphur and nitrogen.

• CML-eutrophication (water). Eutrophication is the enrichment of mineral salts and nutri-ents in marine or lake waters from natural processes and man-made activities such asfarming.

• Depletion of non-renewable resources. Resource depletion is the decreasing availabilityof natural resources such as fossil and mineral resources.

• IPCC-greenhouse effect (direct 20 years). The greenhouse effect allows solar radiationto penetrate the earth’s atmosphere but absorbs the infrared radiation returning to space.The gases responsible for this effect are water vapor, methane and carbon dioxide.

• WMO depletion of ozone layer. Man-made emissions of CFCs and other chemicals usedin refrigeration, aerosols and cleansing agents are thought to cause destruction of ozonein the stratosphere, letting through more of the harmful ultra-violet radiation.

5. Life cycle modelling results and discussion

The environmental effect assessment results of the modelling for the four options arerepresented in Figs. 1–5. It was immediately apparent from the results that of the fourwaste management options, Options 2–4 represented a significant improvement on Option1 as would be expected. Option 1 was the ‘Do Nothing’ scenario where all the MSW waslandfilled.

Several of the figures showed a negative result for a particular option. It should be notedthat a negative result refers to a saving (gain) to the environment and a positive result refersto a loss to the environment. In the case of net gains of a waste management scenario, i.e.recovery options such as materials that are recycled, composted or burnt as fuel to generateenergy (steam or electricity), an ‘avoided inputs and outputs’ approach was used to offsetrequirements for primary materials.

A summary of the differences between the 0 and 3% increase in waste arisings forOptions 1–4 for each of the environmental effect categories is shown in Table 3. The wastearisings increased by about 80% for Options 1, 3 and 4 (i.e. 101,000–182,400 tonnes).There was a 30% increase for Option 2 where the waste arisings increased from 101,000to 132,000 tonnes. These increases were also mirrored in the environmental effect categoryresults for Options 1–4 as shown in Table 3. The higher than average increase for the ‘deple-tion of non-renewable resources’ effect category for Option 4 were due to the incinerationof all the MSW. This would result an increased consumption of non-renewable resourcesin the production of new products and hence a larger difference than the other options.


Fig. 1. Air acidification results for Options 1–4.

The results of Options 1–4 were assigned a performance ranking for each of the fiveenvironmental effect categories as shown in Table 4. For each effect category, a ranking of1 was assigned to the most beneficial environmental result and 4 was the worst result. Aswould be expected it was found that Option 1 (the ‘Do Nothing’ scenario) performed far

Fig. 2. Eutrophication results for Options 1–4.


Fig. 3. Depletion of non-renewable resources results for Options 1–4.

worse than any of the other options for all five of the environmental effect results. For thefive effect categories chosen, Option 4 (the ‘Burn All’ scenario) had the highest rankingfor three of the effect categories. The incineration option was only included to use as acomparison to the other options. Unfortunately, treating 100% of MSW in an incinerator

Fig. 4. Greenhouse effect (direct 20 years) results for Options 1–4.


Fig. 5. Depletion of ozone results for Options 1–4.

Table 3Differences between 0 and 3% increase for Options 1–4

Environmental effect category Option number

Option 1 (%) Option 2 (%) Option 3 (%) Option 4 (%)

Air acidification 57 32 59 81Eutrophication 80 28 81 79Depletion of non-renewable resources 75 34 63 171Greenhouse effect 80 29 59 83Depletion of the ozone layer 81 31 14 79

would not comply with the Wales recovery targets for 2010, as at least 30% needs to berecovered through recycling and composting. However, the EU Landfill Directive targets for2020 could be achieved through EfW technologies such as incineration. It should be notedthat the Landfill Directive targets do not include recovery rates for specific processes such

Table 4Environmental effect category ranking of Options 1–4

Environmental effect category Option ranking

Option 1 Option 2 Option 3 Option 4

CML-air acidification (g eq. H+) 4 2 1 3CML-eutrophication (g eq. PO4) 4 2 3 1EB(R × Y)-depletion of non-renewable resources (year 1) 4 1 3 2IPCC-greenhouse effect (direct 20 years) (g eq. CO2) 4 3 2 1WMO-depletion of the ozone layer (g eq. CFC-11) 4 3 2 1

Note: 1 is the best result and 4 is the worst result.


as recycling and composting. Care should be taken though when viewing and interpretingthe results. Even though Option 4 was ranked number one for three of the effect categoriesa lower ranked category could easily be more important in term of major environmentalconsequences. The software tool does not provide the user with a definitive answer. Itprovides objective information on broad scale environmental costs and benefits. Decidingthe weight that should be given to different effects is a problematic process.

Although not as favourable as Option 4, the overall environmental effect category resultsof Option 3 were also very encouraging. This option incorporated an integrated wastemanagement system that would comply with both the Wales recovery targets for 2010 andalso the Landfill Directive targets for 2020. Compared to Option 1, significant savings wereachieved for all the effect categories. The Landfill Directive targets are only concerned withthe reduction of biodegradable waste from landfill sites and no mention is made of otherwaste materials such as metals, plastics and glass. The majority of recycling schemes in theUK collect a range of materials (both biodegradable and non-biodegradable) and if otherwaste materials were collected then results could be even more favourable.

Overall the software tool was very limited for the types of recovery facilities available.New technologies such as gasification and pyrolysis are currently not available and shouldbe included. These types of facilities can handle much smaller quantities of waste. Therecycling processes available under each recovery category (such as sorting–recycling) andthe material reprocessing options are also limited. For example, there is no sorting/recyclingprocess available for textiles or batteries. For a local authority to get a reasonably accuratepicture of an integrated waste management scenario the model would require a facility toallow for regular updates as new technologies and data becomes available. The softwaretool gives a good indication of the environmental benefits of different waste managementsystems but unfortunately was not designed to take account of social impacts or local issuessuch as nuisance or noise. In making choices, waste managers would also need to take theseinto account.

6. Economic modelling

6.1. Introduction

An interactive microsoft excel spreadsheet model was developed to study different wastemanagement scenarios (Emery et al., 2002). The model incorporates costs, employmentand recovery rates achieved using various recovery vehicles and waste processing methods.Fig. 6 shows a typical flow diagram for the various recovery and disposal options that themodel incorporates. The scenario output results are presented via a number of graphs andtables. The scenario results tables and graphs present the net and gross costs for a numberof participation verses recovery targets. For example, 75% of the available recyclablesrecovered and 75% participation rate. Also presented are several comparative scenariographs which are; cost per year, cost per tonne and numbers of job created. The outputresults also show the minimum recovery, participation rates and costs required to achievethe Welsh recovery target of 40%. To make the model as transparent as possible all scenariocalculations can be accessed and viewed.


Fig. 6. Flow diagram for economic model.

A number of waste management scenarios were investigated which mirrored the optionspreviously modelled for the LCA. The waste management scenarios associated with Options1, 2 and 4 were modelled. All the economic modelling was based on the collection of101,000 tonnes of MSW.

The waste management scenarios that were modelled were as follows:

• Landfill where 100% of the MSW waste produced in the case study area each year islandfilled. This scenario was the equivalent of Option 1.

• Kerbside recycling, operating a fleet of typical caged kerbside collection vehicles withseparate compartments for the recyclable materials. This scenario was the equivalent ofOption 2.

• Kerbside recycling operating a fleet of specialist collection vehicles. The specialist vehicleis a mechanised 16 tonnes kerbside collection vehicle with separate compartments forthe recyclable materials. This scenario was the equivalent of Option 2.

• Split vehicle collection round, operating a fleet of modified refuse collection vehicles(RCVs), which are split into two collection compartments. This scenario was the equiv-alent of Option 2.

• A combination of split vehicle collection with a dedicated MRF and a separate MRFinvolving a thermal pre-treatment step. A thermal pre-treatment system utilises a pressurevessel, fitted with rotating internal drum that accepts waste materials in unopened bags.The system creates an initial vacuum to extract any air present in the chamber that wouldotherwise prevent the effective and immediate heat-up of the waste to be processed.Heat and moisture are introduced in the form of steam. The heat initially causes the


bags to soften and, during rotation, to break open. The combination of high temperature,pressure moisture and rotating drum ensures that all materials will contact the necessarysterilizing steam. The presence of moisture, high heat and pressure during the processcauses pulpable materials such as paper to become repulped and for plastics to deformand shrink. This action decreases the volume of material being processed by about 50%or more of its original volume. The result is a complete sterilization of all processedmaterials.

• Incineration where a variable percentage of the MSW waste produced in the case studyarea was transported outside of the local authority to an incinerator. The incinerationoption includes variable gate costs. This scenario was the equivalent of Option 4.

6.2. Waste components

The composition of the waste materials used for the cost analysis scenarios were based onthe findings of the waste classification trial conducted in the case study area in 2000 (Emeryet al., 2000). The total weight of MSW produced in the case study area was assumedto be 101,000 tonnes. A breakdown of the different waste components from the wasteclassification trial is shown in Table 1. The recyclable materials chosen for the modellingof the kerbside collection scenarios were: ferrous and non-ferrous metals, glass, paper(recyclable element) dense plastic and green waste. These waste materials constitute 55%of the waste stream and are also typical of materials recovered by a large proportion ofrecycling schemes across the UK (Emery et al., 2000). The percentage of recyclable papercollected (17%) is less than that shown in Table 1 (25%) as not all paper is collected by localauthorities due to an element that is difficult to recycle. It should be noted that the collectedgreen waste total is made up of 10% garden waste and 10% kitchen waste. The kitchen wasteelement consists of fruit, vegetables, peelings, eggshells, tea leaves and coffee grounds ascurrently collected by the case study unitary authority. The remaining 12% kitchen waste,which consists of cooked foods such as meats, was classed as non-recyclable and collectedfor landfilling. Although this practice has now ceased and only garden waste is collecteddue to the Animal By-products Regulations.

Expected revenue for recovered recyclable materials delivered to a local reprocessorwere sourced from Materials Recycling Week magazine (2003). The prices as shown inTable 5 should be regarded with some caution because the price ultimately depends on

Table 5Revenue generated from 100% of recovered materials

Material Mass (tonnes) Price (£/tonne) Total price (£)

Ferrous metals 4040 20 80800Glass 7070 22 155540Non-ferrous metals 1010 670 676700Paper—recyclable element 17170 10 171700Plastic dense 6060 60 363600Green waste 20200 n/a 0

Total 55550 1448340

Note: n/a stands for not applicable.


Table 6Variables associated with waste collection vehicles

Variables Units Refusecollectionvehicle

Split refusecollectionvehicle

Regularkerbsidevehicle

Specialistkerbsidevehicle

Annual mileage miles 22000 17000 17000 17000Number of workers per vehicle number 3 3 3 3Waste collected/run tonnes 9 6 2 2Number collections/day number 2 2 2 2

the quality of recyclate produced, transport costs and the quantities sent to the reprocessor.There is also price volatility, but costs selected are a good representation of the differentgroups. A garden waste price (compost) was not included, as further research needs to beconducted to ascertain the true value of green waste as a compost or soil conditioner. Itshould also be noted that the net costs quoted in this paper are the total costs of a particularscenario inclusive of the materials revenue. The gross costs are the total costs exclusive ofthe recyclable materials revenue.

6.3. Collection vehicles

The key variables associated with the different collection vehicles modelled for thisexercise are shown in Table 6. All the figures shown can be altered in the model to suit anyscenario. Four collection vehicles are available to collect the recyclables and general MSW.The collection figures shown are based on data gathered from similar vehicles that wereused in the case study area at the time the model was created. The four types of vehicles usedto collect the recyclables and MSW were a regular RCV, a two compartment split RCV, aregular kerbside caged vehicle and a specialist kerbside vehicle. The split RCV collecteddry recyclables in one compartment and green waste in the other. A typical example of theaverage total weight that a RCV collected was 9 tonnes of waste per collection round andtwo loads per day. It was assumed that the split vehicle could collect 6 tonnes of recyclablesper journey, which would be transported in a semi-compacted state.

The annual total costs for the running of the four different collection vehicles are shownin Table 7. The RCV annual mileage is higher than the other collection vehicles due tothe larger distance travelled to the landfill site located on the north boundary the casestudy area. It was assumed that the other recovery vehicles travelled to a centralised MRFand hence lower overall journey distances. Overheads of 30% have been included for thedriver and operatives wages to include office administration charges and national insurancecontributions.

7. Results of economic modelling

From the analysis of the different waste management options the most cost-effectiveoption for the case study area was found to be the split vehicle mixed bag recyclable col-lection round. This option incorporated a MRF to separate the various recyclable materials.


Table 7Assumed total annual running costs for different collection vehicles

Variables Units Refusecollectionvehicle

Split refusecollectionvehicle

Regularkerbsidevehicle

Specialistkerbsidevehicle

Annual mileage miles 22000 17000 17000 17000Fuel £/year 6906 5336 3169 3169Oil £/year 105 81.04 48 48.01Wages—driver £/year 18200 18200 18200 18200Wages—operatives (×2) £/year 31200 31200 31200 31200Insurance £/year 4000 4000 1000 4000Hire costs £/year 39260 51480 10400 42640

Total £/year 99671 110298 64017 99258

Fig. 7 shows the total net costs of the different waste management options with varyingparticipation rates. The figure also shows the cost comparison for recovery of 100 and65% of the potential recyclable materials and participation of 100 and 50% of households,respectively. From previous experience it is likely that 50% of the households participatingin the kerbside collection scheme recover 65% of the potential recyclable materials wouldbe a more realistic scenario.

The kerbside collection scenario net costs increased quite dramatically with an increasein participation rates and the quantities of recovered recyclable materials. The specialistkerbside vehicle scenario costs actually increased as more materials were recovered due tothe high hire costs of the recovery vehicles and larger numbers of vehicles required dueto a lower collection capacity. The specialist, kerbside vehicle option also had the greatestassociated costs out of all the options considered. The incineration scenario would not beconsidered since the Wales recovery targets would not be reached, although the EU Landfill

Fig. 7. Waste management option net costs for varying participation and recovery rates.


Fig. 8. Total number of jobs associated with different waste management scenarios. Asterisk (*) indicates 100%participation and 100% recovery, (**) 50% participation and 65% recovery and (***) proposed Welsh WasteStrategy Target for 2010.

Directive would be satisfied. It was interesting to note that all of the scenarios, with theexception of one of the split vehicle scenarios, had higher associated costs than the existinglandfill scenario. When compared to the landfill results the caged kerbside vehicle, specialistkerbside vehicle and thermal pre-treatment results only varied between 2 and 14%. A highparticipation and recovery rate combined with a collection vehicle with a large capacity forholding recyclables was the most cost-effective option.

Due to the large number of kerbside collection vehicles required to collect the recyclablematerials the kerbside collection option had the greatest number of associated jobs as shownin Fig. 8. The kerbside collection options generated about 30% more associated jobs thanthe split vehicle collection option. The thermal pre-treatment option had the fewest associ-ated employment opportunities but this increased quite substantially when a split vehicle,materials recovery scheme was introduced with the overall costs only marginally higherthan the regular, kerbside collection vehicle option.

It should be noted that changing the inputs can lead to quite significant changes infinancial model results. Fig. 9 shows the gross results after including the recyclable materialsrevenue. The inclusion of the materials revenue for the scenarios altered the total costsquite significantly. The most notable changes occurred in the reduction of total costs for thescenarios modelled on the 100% participation and 100% recovery option. The gross costsfor the majority of the scenarios were very similar to the costs of the landfill scenario.

Altering the scenario inputs can lead to quite significant differences in outputs. Forexample, reducing the split vehicle capacity from 6 to 2 tonnes to reduce the compactionof the recyclable materials for increased ease of sorting at the MRF. The net cost of the


Fig. 9. Waste management option—gross costs for varying participation and recovery rates.

new split vehicle scenario with 100% participation and 100% recovery, was £92/tonnecompared with the original result of £53/tonne. This actually increased the split vehicleoption from being the most cost-effective scenario to the least cost-effective option out ofall the scenarios modelled. The results showed that modelling a variety of participationand recovery rates together with different waste recovery options is advisable to get a clearpicture of the potential cost variation before making any decisions. Initial input data suchas vehicle costs, wages and materials revenue should also be varied to determined a bestand worst case scenario.

8. Conclusions

The modelling conducted for the case study area was successful in demonstrating thatthere are many positive environmental and economic benefits in choosing an integrated wastemanagement approach. The modelling has shown that software tools can aid those in thewaste management industry in making environmentally and economically sound decisions.A LCA software tool should only be used for identifying opportunities for improvementand not used as the sole basis for a final decision on a waste strategy. Even though the useof WISARD and other LCA tools in the UK are increasing there are still several barriersthat hinder their widespread adoption. The three key barriers are: lack of awareness ofthe importance of using the life cycle concept, the difficultly in obtaining input data andsufficient knowledge of how to input the data correctly and the lack of understanding ofimpact assessment methodology and identifying what type of modelling is appropriate forthe specific application.

The effects of variables such as new legislation, vehicle storage capacities and unpre-dictable markets can all lead to quite significant differences when conducting an economic


analysis. Waste disposal via landfill played a significant role in the economic modelling ofall the waste management options investigated. It is highly unlikely that the need for land-fill sites will be totally eliminated in the immediate future. An integrated approach to themanagement of household waste will ultimately be the most efficient approach in terms ofboth economics and also environment benefits. Unfortunately, LCA and economic softwaretools are not designed to take account of social impacts or local issues such as nuisance ornoise which also need to be considered.

References

Defra, Department for the Environment Food and Rural Affairs. Municipal waste management survey 2000/2001.Defra; 2002, ISBN 0 85521 014 1.

Defra, Department for the Environment Food and Rural Affairs. New figures reveal surge in recycling, retrieved21 January 2006, from http://www.defra.gov.uk/news/2005/050914a.htm; 2005.

DETR. Waste strategy 2000 (England and Wales). Norwich: Her Majesty’s Stationery Office; 2000, ISBN 0 10146932 2.

Emery A, Gibbs A, Griffiths AJ, Myrddin S, Williams KP. Analysis of waste entering a typical small landfillsite in the South Wales valleys, phase 2, report on further composition and weight data. Cardiff University;November 2000 [report no. 2683].

Emery A, Griffiths AJ, Williams KP. An in depth study of the effects of socio economic conditions on householdwaste recycling practices. Waste Manage Res 2003;21:180–90.

Emery AD, Dey M, Griffiths AJ, Williams KP. Economic modelling of collection, treatment and disposal methodsfor household waste in a typical South Wales community. Cardiff University; 2002 [report no. 2920].

Environment Agency. Household waste and recycling—background and data, retrieved 18 January 2006,from http://www.environment-agency.gov.uk/yourenv/432430/432434/432453/435561/435649/?version=1&lang= e; 2003.

European Parliament and Council Directive. EU Landfill Directive 1999/31/EC, retrieved 20 November 2005,from http://europa.eu.int; 1999.

Materials Recycling Week. Markets. Materials Recycling Week; November 2003 ed.; 2003.Morrissey AJ, Browne J. Waste management models and their application to sustainable waste management. Waste

Manage 2004;24:297–308.National Assembly for Wales. Pilot study on municipal waste composition in Wales. Cardiff: NAW; 2003.National Assembly of Wales. Wales waste strategy—wise about waste. Part 2. Cardiff: National Assembly of

Wales; 2002.National Statistics. Census 2001, retrieved 25 November 2005, from http://www.statistics.gov.uk/census2001;

2001.National Statistics. Municipal waste management survey 2004–2005: results of the survey for Wales. Cardiff:

Statistical Directorate, National Assembly for Wales; 2005.Nilsson-Djerf J, McDougall F. Social factors in sustainable waste management. Warmer Bull 2000;73:18–20.Pricewaterhouse Coopers. WISARD reference guide, version 3.7. Pricewaterhouse Coopers; 2006.Standards ISO. ISO 14040—life cycle assessment, retrieved 15 January 2006, from http://www.iso-

14001.org.uk/iso-14040.htm; 1997.Woollam T, Marsh R, Griffiths AJ, Williams KP, Emery A. Box, bag or re-using a supermarket carrier bag: a trial of

different recycling receptacles. In: 19th international conference on solid waste technology and management;2004.

WS Atkins Environment. Life cycle research programme for waste management: inventory development for wastemanagement operations: landfill, final report. Environment Agency; 1997.

York R, Rosa EA, Dietz T. The ecological footprint intensity of national economies. J Ind Ecol 2004;8:139.

http://www.defra.gov.uk/news/2005/050914a.htm

http://www.environment-agency.gov.uk/yourenv/432430/432434/432453/435561/435649/%3fversion=1%26lang=_e

http://europa.eu.int/

http://www.statistics.gov.uk/census2001

http://www.iso-14001.org.uk/iso-14040.htm

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