Waste Management 32 (2012) 1019 1030. Contents lists available at SciVerse ScienceDirect. Waste Management

Wste Mngement 32 (2012) 1019 1030 Contents lists vilble t SciVerse ScienceDirect Wste Mngement journl homepge: www.elsevier.com/locte/wsmn The environmentl comprison of lndfilling vs. incinertion of MSW ccounting for wste diversion Berndette Assmoi, Yuri Lwryshyn Deprtment of Chemicl Engineering nd Applied Chemistry, University of Toronto, 200 College Street, Toronto, Ontrio, Cnd M5S 3E5 rticle info bstrct Article history: Received 30 April 2011 Accepted 15 October 2011 Avilble online 17 November 2011 Keywords: Life cycle ssessment (LCA) Municipl solid wste (MSW) Incinertion Lndfill Greenhouse gses Emissions modelling This study evlutes the environmentl performnce nd discounted costs of the incinertion nd lndfilling of municipl solid wste tht is redy for the finl disposl while ccounting for existing wste diversion inititives, using the life cycle ssessment (LCA) methodology. Prmeters such s chnging wste genertion quntities, diversion rtes nd wste composition were lso considered. Two scenrios were ssessed in this study on how to tret the wste tht remins fter diversion. The first scenrio is the sttus quo, where the entire residul wste ws lndfilled wheres in the second scenrio pproximtely 50% of the residul wste ws incinerted while the reminder is lndfilled. Electricity ws produced in ech scenrio. Dt from the City of Toronto ws used to undertke this study. Results showed tht the wste diversion inititives were more effective in reducing the orgnic portion of the wste, in turn, reducing the net electricity production of the lndfill while incresing the net electricity production of the incinertor. Therefore, the scenrio tht incorported incinertion performed better environmentlly nd contributed overll to significnt reduction in greenhouse gs emissions becuse of the displcement of power plnt emissions; however, t noticebly higher cost. Although lndfilling proves to be the better finncil option, it is for the shorter term. The lndfill option would require the need of replcement lndfill much sooner. The finncil nd environmentl effects of this expenditure hve yet to be considered. Ó 2011 Elsevier Ltd. All rights reserved. 1. Introduction The disposl of municipl solid wste (MSW) is one of the more serious nd controversil urbn issues fcing locl governments globlly. Incresing wste genertion due to popultion growth, societl lifestyle chnges, development nd consumption of products tht re less biodegrdble, hve led to the diverse chllenges for MSW mngement in vrious cities round the world (Asse et l., 2009). Over the pst few decdes, governments nd citizens hve become especilly wre nd concerned bout how wstes re mnged (Sttistics Cnd, 2005). In Cnd, the vilbility of non-developed lnd hs mde lnd disposl or lndfilling, the most populr nd chepest method of wste disposl (Ministry of Environment, 2004). However, with 30% of lndfills in Cnd expected to be full by 2010, recycling is viewed s preferred method of reducing the mount of wste going to lndfills while biologicl tretment of wste such s Corresponding uthor. Address: Centre for Mngement of Technology nd Entrepreneurship, Deprtment of Chemicl Engineering nd Applied Chemistry, University of Toronto, 200 College Street, Rm 256, Toronto, Ontrio, Cnd M5S 3E5. Tel.: +1 416 946 0576; fx: +1 416 978 8605. E-mil ddress: yuri.lwryshyn@utoronto.c (Y. Lwryshyn). composting is becoming more widespred (Sttistics Cnd, 2005). In the pst, the presence of pproprite lndfill sites close to mjor urbn centres hs limited the development of incinertion fcilities in Cnd. Furthermore, therml tretment of wste hs received strong locl opposition due to beliefs tht incinerting: thretens humn helth nd the environment; nd is incomptible with the concept of reducing, reusing, nd recycling (Swell et l., 1996). Although incinertion is not very populr in Cnd, there re currently seven municipl solid wste (MSW) therml tretment fcilities operting tht hve cpcity greter thn 25 tonnes per dy (tpd); in 2006, these therml tretment fcilities hndled pproximtely 3% of Cnd s MSW. There hve been no therml tretment fcilities constructed in Cnd since 1995, with the exception of demonstrtion fcilities in Ontrio nd Quebec (Environment Cnd, 2007). Vrious municiplities view the bsic mngement options: (1) wste prevention (2) recycling (3) biologicl tretment (4) therml tretment (5) lndfilling, s hierrchicl nd not n integrted wste mngement system (Tchobnoglous et l., 2002). However, the ide behind integrted solid wste mngement (ISWM) is tht, rther thn ccepting simple hierrchy, lterntives should be exmined systemticlly so tht wste is mnged in the most resourceful nd environmentlly friendly mnner (Clift et l., 2000). 0956-053X/$ - see front mtter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.wsmn.2011.10.023

1020 B. Assmoi, Y. Lwryshyn / Wste Mngement 32 (2012) 1019 1030 Therml tretment is currently mngement option tht is being dismissed s possible method for treting wste tht hs been lredy reduced through wste prevention, recycling nd biologicl tretment. In mking use of the ISWM concept, this study ssesses the environmentl implictions of implementing wste incinertion to reduce the mount of wste being lndfilled in n existing Cndin wste mngement system tht currently hs wste reduction nd diversion mesures in plce. A life cycle ssessment (LCA) ws used to crry out this study. In ddition to n environmentl study, generic discounted cost nlysis ws done in order to compre the cost of the wste mngement technologies. Few studies such s Rigmonti et l. (2009), Emery et l. (2007) nd Cherubini et l. (2009) hve incorported method of ccounting for different wste compositions. Rigmonti et l. (2009) evlute possible optimum levels of source-seprted collection tht led to the most fvourble energetic nd environmentl results. Emery et l. (2007) exmined the environmentl nd economic impcts of number of wste disposl systems used in typicl South Wles vlley loction. Four options were nlyzed using one constnt MSW composition; however wste risings ssuming 3% per yer increse ws included. Cherubini et l. (2009) who evlutes emissions, totl mteril demnds, totl energy requirements nd ecologicl footprints of four wste mngement scenrios, included scenrio tht splits the inorgnic wste frction (used to produce electricity vi Refuse Derived Fuels, RDF) from the orgnic wste frction (used to produce biogs vi nerobic digestion); Severl other studies, such s, Zho et l. (2009), Limsngun nd Gheewl (2008), Moberg et l. (2005) use one constnt wste composition to undertke the LCA. Similrly to Rigmonti et l. (2009), the source-seprted collection level is prmeter in the nlysis, long with the increse in wste genertion included in Emery et l. (2007). This study focuses on how the current wste diversion inititives nd the gol of incresing the diversion rte ffect wste mngement methods tht tret residul wste. 2. Methodology 2.1. Life cycle ssessment An LCA is useful tool to evlute the performnce of MSW mngement systems (Ekvll et l., 2007; Limsngun nd Gheewl, 2008). The interntionl stndrd ISO 14040-43 defines LCA s compiltion nd evlution of the inputs, outputs nd the potentil environmentl impcts of product system throughout its life cycle (Aren et l., 2003). Life-cycle ssessments were initilly developed for the purpose of nlysing products, lthough recently, it hs lso been pplied to the tretment of wste. The use of LCA for resources nd wste mngement issues implies slightly different focus thn trditionl product-oriented LCAs (Obersteiner et l., 2007). The populrity of LCAs in nlyzing MSW mngement systems is illustrted by the numerous published studies of the life cycle emissions of these systems, s well s by the substntil number of LCA computer models ddressing MSW mngement (Clery, 2009). The structure of LCA consists of four distinct phses, which contribute to n integrted pproch (Aren et l., 2003): (1) Gol nd scope definition, which serves to define the purpose nd extent of the study, to indicte the intended udience nd to describe the system studied s well s the options tht will be compred. (2) Inventory nlysis or life cycle inventory (LCI) focuses on the quntifiction of mss nd energy fluxes. (3) Impct ssessment or LCIA, which ims t understnding nd evluting the mgnitude nd significnce of potentil environmentl impcts of system (Clift et l., 2000). The LCIA orgnises the LCI inputs nd outputs into specific, selected impct ctegories nd models the inputs nd outputs for ech ctegory into n ggregte indictor; such finl ggregtion is controversil, whereby mny uthors terminte the ssessment without ttempting ny synthesis of different impct indictors (Consonni et l., 2005). (4) Interprettion, evlutes the results from the previous phses in reltion to the gol nd scope in order to rech conclusions nd recommendtions (Finnveden et l., 2009). Although LCAs llow for holistic view of the environmentl consequences of process, product or service, it is importnt to be wre of the limittions of the methodology nd to understnd tht the environmentl informtion it genertes is neither complete, nor bsolutely objective or ccurte. LCA results re dependent on methodologicl decisions, such s ssumptions mde in the study nd sources of input dt tht my be influenced by the vlues nd perspectives of the LCA prctitioner (Ekvll et l., 2007). 2.2. Gol nd scope definition The objective of this study is to evlute the environmentl performnce of the incinertion nd lndfilling of MSW tht is redy for the finl disposl while ccounting for existing wste diversion inititives, using the LCA methodology. Prmeters such s chnging wste genertion quntities, diversion rtes nd wste composition re lso considered. A generic discounted cost nlysis ws done in order to compre the cost of the incinertion. 2.3. Selected study site The City of Toronto ws used s selected study site for this life cycle ssessment due to its incresing number of wste diversion inititives; resistnce to considering MSW therml tretment s potentil wste mngement technology; s well s ccessible detiled documenttion of its wste diversion inititives nd lndfill opertions. The City of Toronto diverts wste from the lndfill through vrious progrmmes, such s, progrmmes tht: offer curbside collection of orgnic mterils (i.e. fruit nd vegetbles scrps, pper towels, coffee grinds, etc.) turns it into compost; encourge residents to leve grss clippings on the lwn in order reduce the need for fertilizer nd wter; promote the reuse of glss bottles; nd enble residents to combine both pper nd continer recyclbles into single strem. Simplifying ssumptions tht were mde in this study do not reflect the current or future ctivities of the City of Toronto nor of the Green Lne Lndfill. 2.4. Scope In this nlysis, two different wste mngement scenrios, with both recovering electricity only, were investigted: The sttus quo Scenrio: The lndfilling option. All the residul wste is sent to the lndfill without ny further tretment. Scenrio 2: The incinertion option. 1000 tonnes/dy of residul wste will be incinerted while the reminder will be sent to lndfill.

B. Assmoi, Y. Lwryshyn / Wste Mngement 32 (2012) 1019 1030 1021 Wste Diversion Inititives Mteril Seprtion Reusble & Recycled Mterils Residul Wste Lndfilling Fcility Lechte Energy Recovery Fugitive Air Emissions Air Emissions Lechte Tretment Fcility Fig. 1. Scenrio 1, the lndfilling option with electricity recovery only. The life cycle of MSW in this study begins fter the mteril recovery processes. Therefore, it is ssumed tht the wste collection, seprtion processes, nd trnsfer sttion opertions will be the sme for both wste mngement scenrios nd cn be omitted from the LCA. The scope of this LCA is on the trnsporttion nd the tretment of the wste. The system boundries for where the LCA pplies in ech scenrio re illustrted in Figs. 1 nd 2. The term residul wste ws used to define the wste tht remins fter the diversion of wste through recycling, composting or prevention hs occurred. The residul wste is combintion of residentil nd ICI (Industril, Commercil nd Institutionl) wste. The residentil wste refers to the wste tht is collected by the City of Toronto nd tht re required to meet certin specifictions. The ICI wste refers to the wste tht is not collected by the City of Toronto, but tht is dropped off t trnsfer sttions by compnies for disposl. Construction nd demolition debris, nd wstewter residuls were not included in this nlysis. The diversion inititives pply only to the residentil wste nd the ICI wste remins unsorted. Furthermore, ny increse or chnge in the diversion of wste will ffect the wste composition for both scenrios in the sme mnner. For ech scenrio, detiled LCI hs been used to determine the environmentl emissions. The emissions produced from the construction of fcilities re not included in this study. Other studies such s Limsngun nd Gheewl (2008), Eriksson et l. (2005), nd Wnichpongpn nd Gheewl (2007) hve mde similr ssumptions by considering these emissions smller compred to those relesed during the use of the fcility. The environmentl effects of uxiliry mterils such s supplementl fuels, dily covers 1 nd pollution control chemicls were not exmined. All of the 1 Dily cover is the mteril such s ntive soil tht is pplied to the working fces of the lndfill t the end of ech operting period (O Lery nd Tchobnoglous, 2002). methods nd emissions fctors used to develop the LCI re described in the following sections. The environmentl performnce nd cost of the incinertion nd lndfilling options were nlyzed over period of 30 yers, from 2011 to 2040. This study focused on the ctive life phse of the lndfill nd did not include the environmentl implictions of lndfill closure nd post-closure emissions. The functionl unit of this study is tonnes of MSW from the City of Toronto between 2011 nd 2040. Using n verge of previous dt, it ws estimted tht in 2011, pproximtely 875,000 tonnes of residentil wste would be generted while the diversion rte would be 46%. The quntity of industril residul wste during tht sme yer ws estimted to be 202,500 tonnes. In this study the following emissions were considered: emissions from the stck of incinertion plnts; emissions from the trnsport of solid residues to the wste mngement fcilities; emissions from lndfill opertions; voided emissions from power sttions nd therml plnts displced by the WTE plnt nd lndfill; The following elements were not considered: uxiliry fuel requirements; emissions relted to sh disposl; emissions relting to lechte tretment from the lndfill; emissions relting to the use nd trnsport of dily nd finl cover for the lndfill fcility. Lechte tretment ws not included in the scope. The Green Lne lndfill opertes n on-site wstewter tretment plnt for the lechte. In order to reduce the complexity of this initil

1022 B. Assmoi, Y. Lwryshyn / Wste Mngement 32 (2012) 1019 1030 Wste Diversion Inititives Mteril Seprtion Reusble & Recycled Mterils Residul Wste Incinertion Fcility Lndfilling Fcility Ash Energy Lechte Energy Fugitive Air Emissions Air Emissions Air Emissions Ash Disposl Lechte Tretment Fig. 2. Scenrio 2, the incinertion option with electricity recovery only. Residentil Wste Generted = WG (Tonnes) Wste Diverted = WD(Tonnes) Industril Wste = ID(Tonnes) Residul Wste = Σ((WG - WD) + ID) Wste Distribution % Wste Generted (Tonnes) Wste Distribution % Wste Diverted (Tonnes) Wste Distribution % Residul Wste (Tonnes) Wste Distribution Residul Wste (Tonnes) Wste Composition % Pper 26 WGPper Pper 31 WD Pper Pper 27 ID Pper Pper ((WG-WD)+ID) Pper ((WG-WD)+ID) Pper /Σ((WG - WD) + ID) Food 27 WGFood Food 23 WD Food Food 26 ID Food Food ((WG-WD)+ID) Food ((WG-WD)+ID) Food /Σ((WG - WD) + ID) Yrd 19 WGYrd Yrd 33 WD Yrd Yrd 3 ID Yrd Yrd ((WG-WD)+ID) Yrd ((WG-WD)+ID) Yrd /Σ((WG - WD) + ID) Wood 2 WGWood Wood - WD Wood Wood 9 ID Wood Wood ((WG-WD)+ID)Wood ((WG-WD)+ID) Wood /Σ((WG - WD) + ID) Plstics 8 WGPlstics - Plstics 2 WD Plstics + Plstics 15 ID Plstics = Plstics ((WG-WD)+ID) Plstics ((WG-WD)+ID) Plstics/Σ((WG - WD) + ID) Textile 1 WGTextile Textile - WD Textile Textile 1 ID Textile Textile ((WG-WD)+ID) Textile ((WG-WD)+ID) Textile /Σ((WG - WD) + ID) Lether <1 WGLether Lether - WD Lether Lether <1 ID Lether Lether ((WG-WD)+ID) Lether ((WG-WD)+ID) Lether /Σ((WG - WD) + ID) Rubber <1 WGRubber Rubber - WD Rubber Rubber 1 ID Rubber Rubber ((WG-WD)+ID) Rubber ((WG-WD)+ID) Rubber /Σ((WG - WD) + ID) Ferrous 1 WGFerrous Ferrous 1 WD Ferrous Ferrous 4 ID Ferrous Ferrous ((WG-WD)+ID) Ferrous ((WG-WD)+ID) Ferrous /Σ((WG - WD) + ID) Non-Ferrous <1 WGNon-Ferrous Non-Ferrous <1 WD Non-Ferrous Non-Ferrous 1 ID Non-Ferrous Non-Ferrous ((WG-WD)+ID) Non-Ferrous ((WG-WD)+ID) Non-Ferrous/Σ((WG - WD) + ID) Glss 5 WGGlss Glss 8 WD Glss Glss 2 ID Glss Glss ((WG-WD)+ID) Glss ((WG-WD)+ID) Glss/Σ((WG - WD) + ID) Others 10 WGOther Others 2 WD Other Others 13 ID Other Others ((WG-WD)+ID) Other ((WG-WD)+ID) Other /Σ((WG - WD) + ID) Fig. 3. Methodology used to determine nnul wste compositions. Note: The wste generted increses by 0.2% nnully, the Residentil Diversion rte progresses from 46% to 70% nd the Industril residul wste decreses by 0.05% nnully. nlysis, the tretment of lechte from the lndfill ws not included. Furthermore, the more substntil spect of mnging sh lndfills is the mngement of lechte. Therefore, the disposl of the sh ws lso not included to keep the scenrios comprble. 2.5. Wste quntity nd compositions An importnt spect of this work is its bility to ccount for chnges in wste quntity nd composition s well s diversion rtes. The method used to ccount for the vrious chnges is summrised in the process chrt (Fig. 3) below. Fig. 3 describes the process undertken for every yer from 2011 to 2040 in order to determine the composition of the wste nnully. In n ttempt to better simulte relistic wste mngement scenrios, the mount of residentil wste generted nnully increses by 0.2%, which is projected popultion increse for the City of Toronto between 2011 nd 2030 (City of Toronto, 2011); lthough, it is evident tht fctors, such s societl lifestyles nd trends, in ddition to popultion growth, ffect the mount of wste being generted. The diversion rte which is initilly 46% will increse to 70%, using n nnul growth of 5% nnully, in order to ccount for continuous improvement in wste diversion effectiveness. The mximum residentil diversion rte used in this model ws 70%, which corresponds with the City s Getting to 70% wste diversion from lndfill pln tht would stretch the lndfill lifetime expectncy of the lndfill to 28 yers (City of Toronto, 2011). It ws estimted tht the City of Toronto would go from 46% diversion to 70% residentil wste diversion in the yer 2020, t the rte which the mount of wste diverted is currently incresing. It is importnt to note tht due to lck of dt regrding industril wste diversion for the City of Toronto, only the residentil wste ws diverted in this study. There is currently no relible ICI wste genertion or diversion bseline dt for the province of Ontrio. Informtion regrding other industril wste trends

B. Assmoi, Y. Lwryshyn / Wste Mngement 32 (2012) 1019 1030 1023 Tble 1 Wste compositions used in this study. Composition (% by weight) Residentil wste Industril wste MSW Components Het vlues (Gj/t) Generted Diverted Residul Pper 16 26 31 27 Food 4 27 23 26 Yrd 11 19 33 3 Wood 17 2 9 Plstics 35 8 2 15 Textiles 18 1 1 Lether 17 <1 <1 Rubber 25 <1 1 Ferrous 1 1 1 4 Non-ferrous 1 <1 <1 1 Glss <1 5 8 2 Others 0 10 2 13 MSW components re currently not included in the residentil wste diversion progrmme. for the purpose of this study ws unvilble. ICI genertors use the wste mngement industry for recycling services when the quntity, qulity, frequency nd vlue of wste generted mke it unttrctive for them to investigte, estblish nd execute diversion options outside the wste mngement system. Furthermore, ICI genertors choose to divert recyclble mteril from wste destined for disposl when the quntity, qulity nd frequency mke it economiclly ttrctive to do so (OWMA, 2006). Due to the fct tht no figure supported by reference could be found, nd tht the mount of wste is of dynmic nture, conservtive percentge to represent wste trend ws chosen. The industril residul wste ws ssumed to decrese by n rbitrry vlue of 0.05%. This decrese represents trend of compnies ttempting to improve industril processes in order to reduce the mount of wste being disposed for finncil nd environmentl resons. All compositions, presented in Tble 1, were determined bsed on the tonnge of wste, nd re ssumed to remin constnt throughout the life of the study. The composition of the wste diverted ws determined by nlysing 5 yers-worth of diversion dt from the City, which showed tht the composition of diverted wste remined firly constnt without ny introduction of new wste diversion inititives. The residul residentil nd industril wste compositions were bsed on detiled wste udit done for nother Cndin city, Metropolitn Vncouver, s they were not vilble for the City of Toronto. 2.6. Life cycle inventory The life cycle inventory ws developed using combintion of publicly vilble LCA model technicl reports, greenhouse gs inventory guidelines nd LCA literture. Unfortuntely, there ws no publicly vilble softwre with the bility of providing the flexibility needed to incorporte vrious chnging prmeters. The technicl documents reviewed in the development of this life cycle inventory (LCI) re from the following models: the Cndin Integrted Wste Mngement Model for Municiplities (IWM), developed jointly by the commission of the Environmentl Plstics Industry Council nd Corportions Supporting Recycling (Hight, 2004); the Wste Reduction Model (WARM), developed by the US Environmentl Protection Agency (US EPA, 2006); nd the Municipl Solid Wste Decision Support Tool (MSW-DST) developed by Reserch Tringle Institute (RTI) for the US EPA Office of Reserch nd Development. Other key literture used to develop this model include, the 2006 IPCC Guidelines for Ntionl Greenhouse Gs Inventories, the Cnd s Ntionl Green House inventory Report (NIR) nd the US EPA Compiltion of Air Pollutnt Tble 2 Incinertion fcility emission fctors. Pollutnts Prmeters Units References Arsenic 2.12 10 3 kg/mg US EPA (1996) Cdmium 1.36 10 5 kg/mg US EPA (1996) Chromium 1.50 10 5 kg/mg US EPA (1996) Nickel 2.58 10 5 kg/mg US EPA (1996) Led 1.31 10 4 kg/mg US EPA (1996) CDD/CDF 3.31 10 8 kg/mg US EPA (1996) Mercury 2.80 10 4 kg/mg US EPA (1996) NO x 2.75 10 1 kg/mg US EPA (1996) Sulphur dioxide 2.77 10 1 kg/mg US EPA (1996) Hydrogen chloride 1.06 10 1 kg/mg US EPA (1996) Prticulte mtter 3.11 10 2 kg/mg US EPA (1996) CO 2.31 10 2 kg/mg US EPA (1996) Note: Emission fctors were clculted from concentrtions using n F-fctor of 9570 dscf/mbtu (0.26 dscm/joule (J)) nd heting vlue of 4500 Btu/lb (10,466 J/ g). Other heting vlues cn be substituted by multiplying the emission fctor by the new heting vlue nd dividing by 4500 Btu/lb. Tble 3 Lndfill prmeters. Lndfill gs Prmeters Units References Methne content 55 % Pichtel (2005) CO 2 content 45 % Pichtel (2005) Energy content 19,730 kj/m 3 Pichtel (2005) Gs collection efficiency 75 % US EPA (2008) Lechte chrcteristics BOD 279 mg/l Green Lne Lndfill (2006 2010) COD 967 mg/l Green Lne Lndfill (2006 2010) TSS 191 mg/l Green Lne Lndfill (2006 2010) NH 3 247 mg/l Green Lne Lndfill (2006 2010) Totl nitrogen 352 lg/l Green Lne Lndfill (2006 2010) Phosphorus 3 mg/l Green Lne Lndfill (2006 2010) Emission Fctors (AP-42). The emission fctors used in this model re outlined in Tbles 2 5. 2.6.1. Air emissions This study estimted the following ir emissions of compounds for both the lndfilling nd incinertion systems: Criteri Air contminnts (CAC); Greenhouse gses (GHGs); nd cid gses. CACs re ozone precursors tht consist of nitrogen oxides (NO x ), sulphur dioxide (SO 2 ), crbon monoxide (CO), voltile orgnic compounds

1024 B. Assmoi, Y. Lwryshyn / Wste Mngement 32 (2012) 1019 1030 Tble 4 Emissions from power genertion for col. Pollutnts Prmeters Units References CO 2 1082 Mg/net-GWh OPG (2009) CH 4 n.. Mg/net-GWh OPG (2009) CO 0.19 Mg/net-GWh OPG (2009) NO X 1.40 Mg/net-GWh OPG (2009) SO X 3.09 Mg/net-GWh OPG (2009) TPM 0.28 Mg/net-GWh OPG (2009) HCl 0.11 Mg/net-GWh OPG (2009) N 2 O n.. Mg/net-GWh OPG (2009) VOCs n.. Mg/net-GWh OPG (2009) Tble 5 Wste hulge emissions. Pollutnts Prmeters Units References CO 2 2263 g/l Environment Cnd (2009) CH 4 0.14 g/l Environment Cnd (2009) N 2 O 0.082 g/l Environment Cnd (2009) NO x 10.2 g/vehicle-km ICF (2007) CO 1.64 g/vehicle-km ICF (2007) SO X 0.20 g/vehicle-km ICF (2007) TPM 0.22 g/vehicle-km ICF (2007) HCl 0.11 g/vehicle-km ICF (2007) VOCs 0.3 g/vehicle-km ICF (2007) (VOCs), nd prticulte mtter, including totl prticulte mtter (TPM), prticulte mtter with dimeter less thn or equl to 10 microns (PM 10 ), nd prticulte mtter with dimeter less thn or equl to 2.5 microns (PM 2.5 )(Environment Cnd, 2009). This study only considered the totl prticulte mtter emissions. GHGs re comprised of crbon dioxide (CO 2 ), methne (CH 4 ), nitrous oxide (N 2 O), sulphur hexfluoride (SF 6 ), perfluorocrbons (PFCs) nd hydrofluorocrbons (HFCs) (Environment Cnd, 2009). However, only CO 2,CH 4 nd N 2 O emissions were included in this study s emission fctors for the rest of the GHGs were not common. The emissions of hydrogen chloride (HCl) were the only cid gs emissions reported for both technologies. Only CO 2 emissions of fossil origin (e.g., plstics) were included in the CO 2 emissions estimte. It is importnt to note tht, ccording to the IPCC 2006, textiles nd rubber re comprised of pproximtely 0 50% nd 20% of fossil fuel crbon respectively. However the defult % of fossil fuel crbon suggested by IPCC (2006) is 20% for both textile nd rubber, nd tht is tken into ccount in the clcultions of nthropogenic crbon. The CO 2 emissions from the combustion of biomss mterils (e.g., pper, food, nd wood wste) contined in the wste re biogenic emissions nd were not included in the CO 2 emission estimtes (IPCC, 2006). 2.6.2. Incinertion plnt emissions The incinertion fcility ws modelled using mss burn/ wterwll design with cpcity of 1000 tonnes/dy. The ir pollution equipment in the WTE fcility includes: spry dryer for cid gs control; injection of ctivted crbon for mercury control; mmoni or ure injection by mens of selective ctlytic for reduction of NO x ; nd fbric filter for PM control. The WTE fcility is ssumed to be zero dischrge with respect to wterborne pollutnts. The greenhouse gses (CO 2,CH 4, nd N 2 O) for the incinertion fcility were clculted ccording to the methodology provided in IPCC (2006) while the hevy metls nd cid gses emissions fctors listed in Tble 2 were from US EPA Compiltion of Air Pollutnt Emission Fctors (AP-42). The nthropogenic CO 2 ws clculted by determining the mount of fossil fuel crbon in ech MSW component while the other emissions were determined bsed on the heting vlue of the wste. Both the mount of fossil fuel crbon in the MSW components nd the heting vlue of the MSW components re dependent on the MSW compositions nd would be djusted s the MSW composition chnges. The energy produced is recovered only s electricity, of which 20% will be used for in-house purpose with the reminder sold to the grid. The mss burn incinertor is ssumed to hve conservtive energy recovery efficiency of 20%. This efficiency corresponds to n incinertor tht ws built to minimise investment costs nd is not optimised for power genertion (AECOM, 2009). All uxiliry fuels required to run the fcility re not included in this study. The resulting bottom sh nd fly sh re hndled seprtely. The bottom sh nd fly sh would ccount for 20% nd 5% of the originl weight of the wste, respectively. This ssumption is consistent with wht hs been reported in literture (i.e. Sbbs et l., 2003; Hickmn, 1999; Quin et l., 2010). In this study, no bottom sh ws reused. Insted, the bottom sh ws mixed with the fly sh for hzrdous wste disposl. The environmentl benefits nd burdens of the sh reuse nd sh disposl re not investigted in this LCA. 2.6.3. Lndfill fcility emissions The lndfill fcility ws designed s snitry lndfill. Lndfill gs is composed of minly CO 2 nd CH 4, but cn contin trce concentrtions of compounds such s VOCs nd HCl. The quntity of CO 2 nd CH 4 were determined using the Scholl Cnyon model (see Eqs (1) nd (2)), which is the most commonly used model for determining methne gs genertion (US EPA, 2005). This model ssumes tht the lg phse is negligible nd tht CH 4 production is highest in the erly phse, followed by slow stedy decline in nnul production rtes nd tht first-order kinetic rtes pply. Although, the Scholl Cnyon hs been widely used, this study follows the lndfill modelling method specificlly used in Environment Cnd (2009). Q T;x ¼ km x L o e kðt xþ where Q T,x = the mount of CH 4 generted in the current yer, (T) by the wste, M x, tonnes CH 4 /yer, X = the yer of wste input, M x = the mount of wste disposed of in yer x, tonnes, K =CH 4 genertion rte constnt/yr, L 0 =CH 4 genertion potentil, kg CH 4 /t wste, T = current yer. Q T ¼ X Q T;x where Q T = the mount of CH 4 generted in the current yer (T), tonnes CH 4 /yer. The CH 4 genertion potentil (L 0 ) represents the mount of CH 4 tht could be theoreticlly produced per tonne of wste lndfilled. It is determined using the mount of orgnic crbon tht is ccessible to biochemicl decomposition, which is bsed on the composition of the wste (Environment Cnd, 2009); therefore, s the wste composition is ltered, the nnul lndfill gs emissions re lso modified through L 0. Lndfill gs (LFG) is composed of mny constituents such s nitrogen, oxygen nd hydrogen, in ddition to methne nd crbon dioxide. However, only compounds contributing to the formtion of HCl, SO 2 nd voltile orgnic compounds (VOCs) were included in this nlysis for consistency purposes. The concentrtion of VOCs ws expressed in terms of hexne. In estimting HCl emissions, it ws ssumed tht ll of the chloride from the combustion of chlorinted LFG constituents is converted to HCl. The chlorinted constituents used in this nlysis were: dichloromethne, 1,1,1-Trichloroethne (methyl chloroform), nd perchloroethylene; these compounds represent the LFG constituents tht re tht re most prevlent in LFG. Concen- ð1þ ð2þ

B. Assmoi, Y. Lwryshyn / Wste Mngement 32 (2012) 1019 1030 1025 trtions of reduced sulphur compounds within the LFG were used to estimte of SO 2 emissions. The sulphur compounds consisted of hydrogen sulphide nd dimethyl sulphide s these gses pper in the gretest concentrtions (US EPA, 2008). The quntity of HCl, SO 2 nd VOCs compounds emitted by the lndfill ws estimted using methods nd emission fctors provided by US EPA (2008). Lndfill lechte is produced from precipittion tht flls directly on the site nd percoltes through the lndfill cover (dily, intermedite, or finl) into the wste. For the purpose of this study, method tht relted the quntity of lechte directly to the verge precipittion ws used for simplifiction. The following vlues of lechte production s percentge of precipittion re bsed on field dt (Environmentl Reserch nd Eduction Foundtion, 1999). These constnts were developed by EREF (1999) using empiricl dt nd the US EPA HELP (Hydrologic Evlution of Lndfill Performnce) model s resources. Lechte Production Period 1: wste 0 1.5 yers old, 20% of precipittion. Lechte Production Period 2: wste 1.5 5 yers old, 6.6% of precipittion. Lechte Production Period 3: wste 5 10 yers old, 6.5% of precipittion. Lechte Production Period 4: wste 10 yers old nd older, 0.04% of precipittion. This lechte estimtion method nd the defult prmeters re vlid for the grdul covering of lndfill. In relity, some prts of the site my never be covered with intermedite cover nd be directly covered by finl cover (EREF, 1999). A volume of precipittion cn be clculted given the precipittion in depth/yer nd n re of lndfill surfce. A certin percentge of tht volume ends up s lechte depending on the time fter the plcement of the wste. Together, these vlues provide the mount of lechte generted per re of lndfill surfce. Furthermore, if the tonnes of wste plced per re of lndfill surfce re known, then the quntity of lechte per tonne of wste cn lso be determined. For numericl exmple of how to use these constnts nd further detils on the methodology used to obtin these, see EREF (1999). The lechte qulity informtion shown in Tble 3 is n verge of the concentrtions reported by the Green Lne Lndfill progress nnul reports between 2005 nd 2009. As stted in Tble 3, this study ssumes tht 75% of the lndfill gs is collected, s suggested by US EPA (2008). The lndfill gs collected is used for energy recovery in the form of electricity. Other energy recovery technologies such s combined het nd power were not nlyzed. The reminder of the gs escpes to the environment nd is considered source of greenhouse gses. As the reminder of the gs psses through the lndfill cover, portion of the methne is oxidized. It is ssumed tht 10% of the methne tht is not cptured will be oxidized (IPCC, 2006), lthough, ccording to Spoks et l. (2006), totl methne oxidtion rtes cn from 4% to 50% of the methne flux through the cover t sites with positive emissions. Finlly, the defult energy recovery efficiency from LFG ws reported to be 30% (in gs turbines). The energy recovery efficiency is consistent with tht stted in Diz nd Writh (2006) nd Bove nd Lunghi (2006). Auxiliry fuels needed to operte the technology re out of the scope of this study. It is ssumed tht 20% of the electricity generted ws used for in-house purposes while the reminder is sold to the grid. 2.6.4. Avoided emissions from power plnts The electricity generted from the wste mngement fcilities offsets only emissions from therml power plnts of which four re fuelled by col nd the fifth by oil nd nturl gs. The therml sttions (col nd nturl gs) role is to generte electricity, complementing genertion produced by lower cost nucler nd hydroelectric fcilities. Therml sttions provide flexible source of energy nd cn operte s bse lod, intermedite nd peking fcilities depending on the needs of the electricity system (Ontrio Power Genertion [OPG], 2009). These power plnts re significnt source of nthropogenic CO 2,NO x nd SO x mongst other pollutnts. In Ontrio, nucler nd Hydro re used primrily for meeting bse lod demnd (i.e. the minimum mount of electricity demnd, regrdless of time of dy or seson). The therml sttions role is to generte electricity, complementing genertion produced by lower cost nucler nd hydroelectric fcilities. The pollutnts emitted by the therml power plnts re presented in Tble 4. 2.6.5. Wste hulge emissions This study exmines the environmentl burdens for only the trnsporttion of the wste from the City to the wste fcility. The vehicles re clssified s Clss 8 vehicles nd run on diesel fuel. These trucks hve n verge fuel efficiency of 41.5 L/100 km (ICF, 2007). It ws ssumed tht the trucks would hve lod of 37 tonnes. The truck lod is bsed on the figures used in the contrct for Wste Trnsporttion/Hulge Services from the City of Toronto s Trnsfer Sttions to the Green Lne Lndfill (City of Toronto, 2007). The Criteri Air Contminnts (CACs) emission fctors nd Greenhouse Gs (GHG) emissions were provided by Environment Cnd nd re listed in Tble 5. 3. Results 3.1. Wste composition The chnges in composition cused by residentil wste diversion re importnt becuse the wste composition determines the energy content for incinertion nd the methne genertion potentil for lndfilling. These prmeters determine the mount of energy tht cn be recovered from both wste mngement methods. The chnges in wste composition re presented in Tble 5. The wste groups tht were subjected to diversion were: pper; food; yrd; plstics; ferrous nd non-ferrous mteril; nd other wste. The increse in residentil wste diversion from 46% to 70% cused the presence of selected wste group to lso increse in the wste strem (see Fig. 4). Plstics nd other wste ccount for pproximtely 20% of the wste generted wheres only less Wste Composition (%) 35 30 25 20 15 10 5 Residul Wste Compositions 0 2010 2015 2020 2025 2030 2035 2040 Yer Fig. 4. Compositions of totl residul wste. Food Yrd Plstics Ferrous Non-Ferrous Glss Others Pper

1026 B. Assmoi, Y. Lwryshyn / Wste Mngement 32 (2012) 1019 1030 35.00 Compositions of Residentil Residul Wste 74 Methne Genertion Potentil, L 0 (kg CH 4 /yr) 30.00 72 Wste Composition (%) 25.00 20.00 15.00 10.00 5.00 Pper Food Yrd Plstics Ferrous Non-Ferrous Glss Others Methne Genertion Potentil (kg/yr) 70 68 66 64-2010 2015 2020 2025 2030 2035 2040 Yer Fig. 5. Composition of residentil residul wste. 62 2010 2015 2020 2025 2030 2035 2040 Yer Fig. 7. Methne genertion potentil for the lndfill option. 12.3 12.2 Heting Vlue (GJ/t) 250,000 Incinertion Lndfill Energy Genertion (MWh) Wste Composition (%) 12.1 12 11.9 11.8 11.7 Energy Generted (MWh) 200,000 150,000 100,000 Yer Fig. 6. The residul heting vlue (Gj/t). 50,000 thn 4% of tht wste mkes up the wste being diverted. Therefore, the significnt decrese in the tonnge of pper, yrd nd food wste through diversion cuses the distribution of the plstic nd other wste strems to increse. Ferrous nd non-ferrous metls constitute such smll percentge of the diverted wste tht their composition is not noticebly ffected. A plteu is creted once 70% diversion is rech becuse once the mximum diversion is rech, the diversion rte becomes constnt nd the wste composition becomes influenced only by the wste genertion rte, which is currently 0.2%. Since the industril residul wste hs slightly different wste distribution nd ws unsorted, the influence of the residentil wste diversions ws slightly diminished; however, the residul wste follows the wste composition trend of the residentil wste (see Fig. 5). 3.1.1. Energy content nd methne genertion potentil The reduction of orgnic wstes (i.e. pper, food nd yrd) nd the increse in other wstes such s plstics, lether nd rubber wste, s result of n increse in diversion rte, enhnces the energy content of the residul wste. This in turn increses the mount of electricity tht could be potentilly produced through incinertion (see Fig. 6). On the other hnd, the reduction in the orgnic content of the wste, minly pper nd yrd wste, reduces the methne tht cn be potentilly generted nd recovered for energy from lndfilling (see Fig. 7). 0 Fig. 8. Comprison of energy generted from incinertion nd lndfilling. With regrds to the mount of energy generted, the incinertion option genertion significntly more energy thn the lndfilling option (Fig. 8). The energy genertion from the incinertion option is more constnt s opposed to the lndfill energy genertion tht will pek nd then decrese to point where energy recovery is no longer possible. 3.2. Life cycle impct ssessment Environmentl impct ctegories were used to fcilitte the environmentl comprison between the two wste mngement technologies nd to llow for cler presenttion of the results. This nlysis only included the following ctegories: globl wrming potentil (GWP), cidifiction potentil (AP) nd nutrient enrichment potentil (NEP), which re the most common impct ctegories included in the LCIA phse. The impct ctegories, their respective emissions, nd equivlency impct fctors pplied in this study re presented in Tble 6. Globl wrming potentil (GWP) ccounts for the emission of greenhouse gses (CO 2,CH 4,N 2 O), whose chrcteristion fctors re bsed on the model developed by the Intergovernmentl Pnel

B. Assmoi, Y. Lwryshyn / Wste Mngement 32 (2012) 1019 1030 1027 Tble 6 Impct ctegories, emissions, nd equivlency fctors. Globl wrming c potentil 100 yers (kg CO 2 ) Acidifiction (g SO 2 ) d Nutrient enrichment d potentil (g NO 3 ) Emissions Equivlency fctors Emissions Equivlency fctors Emissions Equivlency fctors CO 2 CH 4 1.00 SO 2 1.0 Totl b nitrogen 4.43 21 NO 2 0.70 NO x 1.35 N 2 O 320 HCl 0.88 N 2 O 2.82 Totl b phosphorus 32.03 b Emissions to ir. Emissions to wter. c Source: Environment Cnd (2009). d Source: Mendes et l. (2004). Fig. 9. Globl wrming potentil results for incinertion nd lndfilling option. Fig. 11. Nutrient enrichment potentil results for incinertion nd lndfilling option. Tble 7 Summry of ll the costs nd revenues included in the model. Scenrio Incinertion fcility Lndfill fcility Revenues Electricity genertion Electricity genertion ICI disposl fees ICI disposl fees Mteril recovery Lndfilling disposl fees Costs Cpitl costs Cpitl costs Opertion costs Opertion costs Wste hulge to incinertion fcility cost Wste hulge to lndfilling fcility costs Ash disposl costs Lndfill disposl costs Wste hulge to lndfilling fcility costs Fig. 10. Acidifiction potentil results for incinertion nd lndfilling option. on Climte Chnge (IPCC, 2006) nd referred to time horizon of 100 yers (GWP100). Greenhouse gses (GHGs) refers to the gses (primrily wter vpour, crbon dioxide, methne nd nitrous oxide) present in the erth s tmosphere which contribute to globl tempertures through the greenhouse effect (Feo nd Mlvno, 2009). Fig. 9 shows the GWP expressed in tonnes CO2e. The mjority of the emissions come from the opertion of the wste mngement fcilities s the emissions from trnsporting the wste to the fcility cn be considered insignificnt. The CO 2 emissions result from the lndfilling option minly due to the combustion of methne, wheres the CO 2 emissions from the incinertion fcility result from the combustion of plstics. In ddition, the gs recovery system significntly decresed the uncontrolled methne nd VOCs emissions. As stted previously, only nthropogenic CO 2 ws considered in this nlysis, consequently, lrge quntity of CO 2 relesed by the lndfill were disregrded. Furthermore, plstics re stble elements nd therefore contribute little to the methne genertion. Acidifiction potentil (AP) is the process whereby ir pollution, minly mmoni, sulphur dioxide nd nitrogen oxides, re converted into cidic substnces. Some of the principl effects of ir cidifiction include lke cidifiction nd forest decline (Feo nd Mlvno, 2009). Acidifiction Potentil (AP) ccounts for the emissions of NO x,so x nd mmoni. Fig. 10 shows the AP, expressed s kg of SO 2 equivlent per kg of emission. The incinertion option performed more poorly from n environmentl perspective thn the lndfill option in terms of AP. Compounds such s sulphur

1028 B. Assmoi, Y. Lwryshyn / Wste Mngement 32 (2012) 1019 1030 Tble 8 Incinertion cost prmeters. Prmeters Vlue Units Cpitl investment 300,000,000 $ Lndfill disposl costs 20 $/tonne Operting nd mintennce costs 47 $/tonne Residue disposl costs 100 $/per tonne Trnsporttion costs Wste hulge costs 18 $/per tonne Fuel surchrge costs 4 $/per tonne Revenue Electricity price 0.04 h/kwh Tipping fees 40 $/tonne Customer price index 2 % Discount rte 5 % Dys of opertion 320 Dys Tble 9 Lndfill cost prmeters. Prmeters Vlue Units Cpitl investment 260,000,000 $ Operting nd mintennce costs 18 $/tonne Trnsporttion costs Wste hulge costs 18 $/per tonne Fuel surchrge costs 4 $/per tonne Revenue Electricity price 0.04 h/kwh Tipping fees 40 $/tonne Customer price index 2 % Discount rte 5 % Dys of opertion 320 Dys The cpitl investment includes the cost of the lnd s the lndfill is lredy built nd operting. dioxide, nitrogen dioxide nd hydrogen chloride re emitted t much higher concentrtions with incinertion compred to lndfilling. The mount of sulphur dioxide nd hydrogen chloride emitted from incinertion is dependent on the sulphur nd chlorine content in the wste. Furthermore, lndfill gses such s sulphur dioxide, nitrogen dioxide nd hydrogen chloride; typiclly occur in concentrtions less thn 1% (v/v). Nutrient enrichment potentil (NEP) or Eutrophiction is the enrichment of minerl slts nd nutrients in mrine or lke wters from nturl processes nd mnmde ctivities such s frming (Emery et l., 2007). Fig. 11 illustrtes the NEP is expressed s g NO 3 which includes both emissions to ir nd to wter. It ccounts for the totl phosphorus nd nitrogen in the wter nd the NO x nd N 2 O emissions in the ir. The lndfilling option hs noticebly smller eutrophiction impct on the environment. The mjority of the emissions tht contribute to the lndfilling option s NEP result from the lechte produced. However, the incinertion emissions include greter NO x nd N 2 O ir emissions, in ddition to the totl dissolved nitrogen nd phosphorus wter emissions, which originte from the lechte produced by the remining wste lndfilled. In this study, it ws ssumed tht the energy produced by both options would displce the emissions generted by therml power plnts. When the environmentl offsets re pplied, incinertion outperforms lndfilling in ll environmentl ctegories (Figs. 9 11). Nitrogen oxides (NO x ), sulphur dioxide (SO 2 ) re mong the most prominent ir emissions from therml energy fcilities. As result, the cidifiction potentil is significntly impcted by the electricity offset. The incinertion option receives environmentl offsets from the electricity produced both from the combustion s well s from the reminder wste tht is lndfilled. With the inclusion of the electricity offset, the incinertion option performs better environmentlly becuse incinertion genertes significntly more electricity thn lndfilling. 3.3. Finncil nlysis An economic nlysis ws done in ddition to the environmentl LCA, in order to crry out more complete comprison of the technologies. The costs include opertionl nd mintennce costs nd costs ssocited with the hulge of the wste, while the revenues re comprised of wste-drop off fees, electricity sles nd mteril recovery. A summry of ll of the costs nd revenues 80 Wste Mngement Cost 70 Cost ($/tonne of residul wste) 60 50 40 30 20 Incinertion - 50 km Incinertion - 100 km Incinertion - 200 km Incinertion - 500 km Lndfill Fcility Cost 10 0 50 100 200 500 Lndfill Distnce (km) Fig. 12. Wste mngement cost with respect to distnce from city core.

B. Assmoi, Y. Lwryshyn / Wste Mngement 32 (2012) 1019 1030 1029 cn be found in Tbles 7 9. In this study, the costs re reported on per tonne bsis nd in ctul Cndin dollrs to fcilitte comprisons. The results for the bseline scenrio indicte tht the incinertion option costs net $48.54/tonne wheres the lndfill option costs net $32.85/tonne 2. In the time spn nlyzed (2011 2040), the lndfilling option genertes pproximtely $400 million in revenue compred to incinertion tht genertes pproximtely $610 million. The elevted cost of incinertion option is due to the greter number of costs incurred compred to lndfilling, which re listed in Tble 7. In ttempt to identify scenrios in which the incinertion option my become more finncilly fesible, the effects of distnce on the finncil results were evluted becuse trnsporttion ccounts for significnt prt of the costs (see Fig. 12). The proximity of the incinertion fcility nd the lndfill fcility to the City core were vried. It is importnt to the note tht due the limited incinertor cpcity, the reminder of the wste is sent to lndfill. The distnce of this lndfill is lso considered in this sensitivity nlysis. All the fcilities re locted 200 km one-wy from the City core in the bseline scenrio. Distnces of 50, 100, nd 500 km for the incinertor nd lndfill from the City core were used in the sensitivity nlysis. No distnces bove 500 km were exmined becuse these types of distnces would most likely require wste trnsport by trin. In the finncil model, the cost for the hulge services of the wste to the fcilities re function of distnce. Consequently, the cost of both wste mngement options increses s the fcilities re locted further wy from the City. The incinertion fcility becomes competitive finncilly when the lndfill fcility is locted 500 km wy from the City nd the incinertion fcility is locted 50 to 100 km wy with its corresponding lndfill fcility locted 50 to 200 km wy from the City. Lndfilling ll the wste remins the preferred finncil option with ll the other scenrios exmined in this model. 4. Conclusion The gol of this study ws to compre the use of n incinertion nd lndfilling fcility in the mngement of residul wste while ccounting for residentil wste diversion inititives, from both n environment s well s finncil perspective. Wste diversion inititives hve become n integrl prt of the wste mngement process nd it is importnt to be ble to understnd how these inititives ffect the wste composition. The wste composition will ultimtely dictte the type of wste mngement method tht is the most suitble. The results indicted tht the use of n incinertion fcility to mnge portion of the wste ws better environmentlly while lndfilling ll of the wste would be preferred finncilly. The wste mngement option tht included the incinertion fcility performed better environmentlly becuse the incinertion fcility produced significntly more electricity compred to the lndfilling fcility, nd therefore noticebly greter environmentl offset. The residul wste composition ws significntly impcted by the residentil diversion inititives nd incresing diversion rte. The residentil wste diversion inititives proved to be more successful for the orgnic wste strems (i.e. pper, food nd yrd wste). Consequently, s the diversion rte incresed from 46% to 70%, the significnt removl in the orgnic wste strems cused the composition of other wste groups such s plstics nd other wste to increse considerbly. The removl of orgnic content lso reduced the mount of energy tht could be recovered from 2 Costs represent net discounted costs per tonne. the lndfill by decresing the mount of methne generted by the lndfill. Conversely, the rise in inert wstes like plstics improved the energy recovery cpbility of the incinertion option by incresing in the energy content of wste. The diversion of these inert wste groups is importnt becuse they reduce the lndfill cpcity without contributing to the genertion of methne nd energy recovery process. Consequently, the most effective mnner of hndling these wste groups would be through the increse wste reduction nd diversion inititives s well s incinertion. The incinertion technology would ctully benefit gretly from the presence of plstics in the residentil wste strem due to its high energy content, while reducing the quntity to wste being lndfilled. The only benefit to incinerting other wste since this wste component hs no clorific vlue would be the volume reduction, which would lso extend the life of n existing lndfill. This study is n improvement in the undertking of municipl solid wste (MSW) life cycle ssessments where mny studies hve ssumed constnt MSW composition. More updted emission fctors nd more dvnced wste quntity predictive methods would yield more ccurte nd relistic results. The inclusion of current wste diversion inititives nd chnging wste composition is one step closer towrds crrying out n nlysis tht better reflects the relities in MSW mngement. However, n LCA typiclly does not yield objective nswers nd the methodology lso suffers from lrge uncertinties. Furthermore, n LCA entils drstic simplifiction of the complex relity (Ekvll et l., 2007). Simplifictions nd ssumptions mde to reduce the complexity of this nlysis diminished the completeness of the LCA. A more complete nlysis is required if the results re to be used for decision-mking purposes. A mjor ssumption tht ws mde in this study ws tht the composition of the wste diverted would remin constnt over the life of the study. This ssumption implies tht no new diversion inititives would be introduced or tht technologicl dvncements would not ffect the wste diverted. Therefore, in order for the results to remin relevnt, future LCAs should be done s new wste diversion inititives re lunched or s new wste mngement technologies become minstrem. Other ssumptions included the omissions such s the effects of ncillry processes nd of lechte tretment for both the hzrdous sh nd lndfill. The processes should be included in future studies to improve the completeness of the nlysis. Furthermore, this study considered electricity s the only form of energy recovery for simplifiction purposes, however, the effects other forms of energy recovery systems, such s combined het nd power, should be explored further. The cpcity of the lndfill is n importnt prmeter tht ws not included in this study, but should be considered in future studies. 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