Steps towards more environmentally sustainable municipal solid waste management – A life cycle assessment study of São Paulo

S eps owa ds mo e en i onmen ally sus ainable municipal solid was e managemen eA li e cycle assessmen s udy o S~ ao Paulo, B azil Miia Liikanen a , * , Jouni Ha ukainen a , Ednilson Viana b , Mika Ho anainen a a Depa men o Sus ainabili y Science, Lappeen an a Uni e si y o Technology, P.O. Box 20, FI-53851, Lappeen an a, Finland b Uni e si y o S~ ao Paulo, EACH, Rua A lindo Be io, 1000, CEP: 03828-000, S~ ao Paulo, B azil a icle in o A icle his o y: Recei ed 4 Janua y 2018 Recei ed in e ised o m 15 May 2018 Accep ed 1 June 2018 A ailable online 1 June 2018 Keywo ds: Was e managemen Li e cycle assessmen Landfilling Compos ing Anae obic diges ion Mechanical-biological ea men abs ac Landfill disposal has hus a been he p edominan ea men me hod o municipal solid was e (MSW) h oughou B azil, including S~ ao Paulo ci y. En i onmen ally sus ainable de elopmen o MSW man- agemen in S~ ao Paulo necessi a es a s epwise educ ion o landfilling. Howe e , e e inc easing MSW gene a ion poses he challenge o managing inc easing MSW olumes while simul aneously mode n- izing he MSW managemen sys em. In his s udy, he en i onmen al impac s o he cu en MSW managemen sys em and u u e al e na i es in he ci y we e assessed by means o li e cycle assessmen (LCA) o de e mine a pa hway owa ds mo e en i onmen ally sus ainable MSW managemen . The assessed impac ca ego ies we e global wa ming, acidifica ion and eu ophica ion po en ials. Po en ial u u e al e na i es included he s epwise educ ion o landfilling by he in oduc ion o compos ing, anae obic diges ion and mechanical-biological ea men (MBT). The esul s o he s udy indica ed ha he en i onmen al impac s o MSW managemen in S~ ao Paulo can be mos e ec i ely diminished by anae obic diges ion o sou ce sepa a ed o ganic was e and MBT o MSW, on condi ion ha he p oduced e use-de i ed uel (RDF) is u ilized in cemen p oduc ion as a subs i u e o coal. The o he u iliza ion op ion o RDF, incine a ion, would inc ease he en i onmen al impac s o MSW managemen due o he low amoun o a oided emissions esul ing om elec ici y subs i u ion since a e age elec ici y p o- duc ion in B azil is domina ed by hyd opowe . Sensi i i y analyses indica ed, howe e , ha he en i- onmen al impac s o incine a ion migh dec ease wi h di e en modeling assump ions, e.g. he modeling assump ion ega ding he kind o elec ici y p oduc ion subs i u ed by elec ici y p oduc ion om MSW. Ne e heless, he main findings o he s udy emained he same and hey a e in line wi h he p e ious li e a u e. ©2018 The Au ho s. Published by Else ie L d. This is an open access a icle unde he CC BY license (h p://c ea i ecommons.o g/licenses/by/4.0/). 1. In oduc ion E e g ea e gene a ion o municipal solid was e (MSW) is becoming an inc easingly p essing issue globally, pa icula ly in eme ging economies and de eloping coun ies, whe e he local in as uc u e and MSW managemen sys ems canno always keep up wi h he la ge MSW olumes esul ing om apid popula ion and economic g ow h as well as inc eased u baniza ion (Gue e o e al., 2013). The Wo ld Bank (2012) has o ecas ha global MSW gene a ion will double by 2025 (2012 as a e e ence yea ). Eme ging economies, in pa icula , China, India and B azil, will play a c ucial ole in add essing his global issue. In olume, China is he wo ld's la ges gene a o o MSW, and India and B azil a e hi d and ou h la ges , espec i ely (Was e A las, 2017). B azil gene a es app oxima ely 63 million onnes o MSW annually (Was e A las, 2017). Annual MSW gene a ion pe capi a is app oxima ely 380 kg, which is lowe han ypically ound in uppe middle income coun ies (app oxima ely 440 kg acco ding o Wo ld Bank (2012)). Taking in o accoun he s ong co ela ion be ween MSW gene a ion and income le el, MSW gene a ion pe capi a can be expec ed o inc ease o e he ollowing yea s, should B azil, as o ecas , eco e om he cu en ecession (Wo ld Bank, 2017a). Despi e unce ain y su ounding he economic p ospec s o he coun y, o al MSW gene a ion will howe e con inue o in- c ease due o popula ion g ow h (Wo ld Bank, 2012). S a is ics o he na ional economy o 2013 o 2016 show ha while g oss na- ional income (GNI) pe capi a dec eased by 30.6%, he o al pop- ula ion inc eased by 2.6%. Al hough popula ion g ow h has *Co esponding au ho . E-mail add ess: miia.liikanen@lu .fi(M. Liikanen). Con en s lis s a ailable a ScienceDi ec Jou nal o Cleane P oduc ion jou nal homepage: www.else ie .com/loca e/jclep o h ps://doi.o g/10.1016/j.jclep o.2018.06.005 0959-6526/©2018 The Au ho s. Published by Else ie L d. This is an open access a icle unde he CC BY license (h p://c ea i ecommons.o g/licenses/by/4.0/). Jou nal o Cleane P oduc ion 196 (2018) 150e162 decele a ed sligh ly, due o he poo economic si ua ion, he g ow h cu e has ne e heless emained posi i e (Wo ld Bank, 2017b). B azil will hus ace he ough challenge o managing inc easing MSW gene a ion while simul aneously de eloping i s MSW man- agemen sys ems in a mo e sus ainable di ec ion. S~ ao Paulo is he mos populous ci y in B azil and he case a ea o his s udy (see Fig. 1). The ci y is he capi al o S~ ao Paulo s a e, which is he wo ld's la ges MSW gene a o a a egional le el, gene a ing app oxima ely 20 million onnes o MSW annually, o which 4.7 million onnes a e gene a ed in S~ ao Paulo ci y (CCAC, 2015a;Was e A las, 2017). I has been es ima ed ha 97.8% o MSW gene a ed in S~ ao Paulo is unde he o mal MSW manage- men sys em. In addi ion o he o mal MSW managemen sys em, indi idual picke s and picke o ganiza ions collec ecyclables in o mally. Fo mally collec ed MSW is disposed o in he ci y's wo sani a y landfills (i.e. landfills wi h landfill gas (LFG) and leacha e collec ion sys ems). In addi ion, S~ ao Paulo has wo mechanical so ing plan s o sepa a ely collec ed ecyclables such as plas ic, pape , ca dboa d, me al and glass. Fo mally collec ed ecyclables cons i u e, howe e , only a mino p opo ion o o al MSW gene - a ed (app oxima ely 1%, 50 000 onnes/a) (CCAC, 2015a;CCAC, 2015b). The u u e s a egy o MSW managemen in S~ ao Paulo is desc ibed in PGIRS (Plano de Ges ~ ao In eg ada de Residuous Sol- idos), he MSW managemen plan o he ci y, launched in 2014 (P e ei u a de S~ ao Paulo, 2014). One o he main p io i ies o PGIRS is educ ion o he olume o MSW disposed o in landfills. O ganic was e managemen can play an impo an ole in achie ing his objec i e, since app oxima ely hal o MSW is o ganic was e. Consequen ly, sou ce sepa a ion and sepa a e ea men o o ganic was e would e ficien ly educe he olume o MSW landfilled, and hus he en i onmen al impac s. Bo h compos ing (including home compos ing) and anae obic diges ion (AD) a e p oposed in PGIRS as po en ial ea men me hods o o ganic was e. Some small-scale ini ia i es p omo ing home compos ing al eady exis (Compos a S~ ao Paulo, 2017) bu no compos ing o AD plan s a e cu en ly ope a ional in S~ ao Paulo, based on in o ma ion om 2016, when he da a o his s udy was collec ed. In addi ion o he abo e- men ioned ea men me hods, mechanical-biological ea men (MBT) is p oposed in PGIRS as a po en ial ea men me hod (CCAC, 2015a;P e ei u a de S~ ao Paulo, 2014). Li e cycle assessmen (LCA) is a me hod o es ima ing he po- en ial en i onmen al impac s o p oduc s o sys ems (EN ISO 14040, 2006;EN ISO 14044, 2006). LCA has been u ilized in he field o MSW managemen since he 1990s, and i is cu en ly a widely used echnique o assess he en i onmen al impac s o MSW managemen sys ems (Lau en e al., 2014). LCA enables compa ison o di e en MSW managemen s a egies and ea - men me hods in e ms o hei en i onmen al impac s, which makes i a use ul ool o decision- and policy-making (e.g. Ka mpe is e al., 2013;Tu ne e al., 2016). A as numbe o s udies ha e been published ha in es iga e di e en aspec s o MSW managemen in di e en pa s o he wo ld eand B azil is no excep ion. Fo example, he elec ici y p oduc ion po en ial o MSW in B azil was he ocus o Leme e al. (2014),Lino and Ismail (2011) and Mambeli Ba os e al. (2014). LCA s udies ocusing on compa ison o al e na i e MSW ea men me hods in a gi en case a ea a e also common. Fo ins ance, Goula Coelho and Lange (2016) and Be ns ad Sa ai a e al. (2017) ecen ly assessed he en i onmen al impac s o MSW managemen al e na i es in Rio de Janei o by means o LCA. LCA s udies o MSW managemen in S~ ao Paulo, he case a ea o his s udy, ha e also been published. Mendes e al. (2003) assessed he en i onmen al impac s (namely global wa ming, acidifica ion and nu ien en ichmen ) o o ganic was e ea men in S~ ao Paulo using LCA. They compa ed h ee di e en ea men me hods o o ganic was e: landfilling, compos ing and AD. Bo h compos ing and AD had lowe en i onmen al impac s han landfilling, wi h one excep ion: compos ing had he highes acidifica ion po en ial o he h ee ea men me hods. AD had lowe en i onmen al impac s han compos ing (con en ional compos ing wi hou biofil a ion). In ano he s udy, i.e. Mendes e al. (2004), he same au ho s used LCA o compa e he en i onmen al impac s ( o he same impac ca ego ies as abo e) o landfilling and MSW incine a ion o S~ ao Paulo. I was ound ha landfilling had highe en i onmen al impac s han incine a ion. Howe e , he di e ences we e no g ea due o he s uc u e o he elec ici y p oduc ion sec o in B azil, whe e a as majo i y o elec ici y is p oduced by hyd opowe (94% in Mendes e al. (2004)). The e o e, elec ici y p oduc ion om MSW did no yield a significan amoun o a oided emissions. Mo e ecen ly, Soa es and Ma ins (2017) conduc ed a ga e- o- g a e LCA o 1 onne o MSW ecei ed in CTVA Caiei as landfill, one o he sani a y landfills in S~ ao Paulo. In he s udy, he en i- onmen al impac s o a ious was e- o-ene gy op ions - LFG com- bus ion wi h ene gy eco e y, MBT combined wi h AD, and incine a ion ewe e e alua ed. I was ound ha MBT combined wi h AD had he lowes en i onmen al impac s o he scena ios assessed in he s udy. Being a si e-specific ga e- o-g a e LCA, he s udy did no co e he en i e li e cycle o MSW, i.e. om MSW gene a ion o i s final ea men o disposal. As e iden om he abo e examples, p e ious LCA s udies o he MSW managemen sys em o S~ ao Paulo ha e ocused mo e on specific ea men me hods and hei en i onmen al impac s, a he han assessing comp ehensi ely he en i onmen al impac s o he MSW man- agemen sys em as a whole consis ing o di e en ea men op- ions and me hods o di e en MSW flows (e.g. o ganic and esidual ac ion o MSW). Fig. 1. Backg ound in o ma ion abou S~ ao Paulo. M. Liikanen e al. / Jou nal o Cleane P oduc ion 196 (2018) 150e162 151 This s udy uses LCA o assess he en i onmen al impac s o di e en managemen al e na i es o MSW in S~ ao Paulo in o de o de e mine a pa hway owa ds mo e en i onmen ally sus ainable MSW managemen in he ci y. The s udy akes in o accoun he en i e li e cycle o MSW: om MSW gene a ion o i s final ea - men o disposal. Bo h o ganic and esidual ac ions o MSW a e assessed in he s udy. The scena ios he s udy a e based on he de elopmen p oposals and objec i es o PGIRS, and hey p esen po en ial imp o emen s eps o he sys em. The esea ch ques- ions o he s udy a e he ollowing: Wha a e he en i onmen al impac s o MSW managemen in S~ ao Paulo? In which di ec ion should he sys em be de eloped in o de o diminish he en i onmen al impac s o MSW managemen in he ci y? 2. Ma e ials and me hods 2.1. MSW managemen in S~ ao Paulo Household was e, s ee cleaning was e as well as was e om ma ke s and comme cial ac i i ies gene a ing less han 50 kg pe day a e ega ded as MSW in S~ ao Paulo. To al MSW gene a ion in S~ ao Paulo is app oxima ely 4.7 million onnes/a (CCAC, 2015a). The as majo i y o MSW in S~ ao Paulo is mixed MSW om households; in 2015, 3.8 million onnes o mixed MSW was collec ed and ea ed (AMLURB, 2016). Mixed MSW e e s o he emaining pa o MSW a e he sou ce sepa a ion o ecyclables. This s udy ocuses on his pa icula MSW flow, i.e. o mally collec ed and ea ed mixed MSW om households, since o mal in o ma ion is a ailable and such was e cons i u es he majo i y o o al MSW gene a ed (hence o h in his s udy MSW e e s solely o mixed MSW om households due o abo e-men ioned easons). Fo mally collec ed and ea ed ecyclables a e no aken in o accoun in he s udy since hey compose only a mino p opo ion o he o al MSW gene a ion, and hey a e al eady ea ed in an en i onmen ally sus ainable manne , on he p esump ion ha he collec ed ma e ials a e uly eclaimed. In o mally collec ed ecyclables a e no assessed in he s udy since no o mal in o ma ion was a ailable. The MSW managemen au ho i y o S~ ao Paulo, AMLURB, has con ac ed ou MSW managemen ac i i ies o wo p i a e com- panies: Loga and Ecou bis (CCAC, 2015a). The di ision be ween he companies is geog aphical. Loga is esponsible o managemen o MSW gene a ed in he no he n and wes e n pa s o S~ ao Paulo, whe eas Ecou bis is in cha ge o he MSWgene a ed in he sou he n and eas e n o he ci y (AMLURB, 2016). The e a e wo landfills in S~ ao Paulo: he Cen al de T a amen o Les e (CTL) landfill (Ecou bis) and he Cen al de T a amen o e Valo izaç~ ao Ambien al (CTVA) Caiei as landfill (Loga). MSW is anspo ed ei he di ec ly o ia ans e s a ions o he landfills. The e a e h ee ans e s a ions in he ci y; Ecou bis owns and ope a es wo o hem (San o Ama o and Ve guei o), and Loga one (Pon e Pequena). Bo h companies ha e hei own collec ion and anspo a ion flee s. The e a e wo me- chanical so ing plan s in he ci y. Howe e , onlya mino p opo ion o MSW is ea ed in hese plan s, and he as majo i y o MSW is disposed o in landfills, as men ioned ea lie (CCAC, 2015a). Di e en MSW s eams and he a e age composi ion o mixed MSW in S~ ao Paulo a e p esen ed in Fig. 2. As can be seen, o ganic was e p edomina es, o ming 49% o he composi ion o mixed MSW. Fig. 2. Di e en MSW s eams and he composi ion o mixed MSW in S~ ao Paulo (AMLURB, 2016;CCAC, 2015b). M. Liikanen e al. / Jou nal o Cleane P oduc ion 196 (2018) 150e162152 2.2. Li e cycle assessmen The LCA was conduc ed in acco dance wi h he ISO s anda ds 14040 (2006) and 14044 (2006). The impac ca ego ies assessed in he s udy we e global wa ming po en ial (GWP) o a 100 yea ime span, acidifica ion po en ial (AP) and eu ophica ion po en ial (EP), since he equi ed li e cycle in en o y (LCI) da a was a ailable (see Sec ion 2.2.2 and Supplemen a y ma e ial A-D o u he in o - ma ion abou he LCI da a). Su ficien ly comp ehensi e LCI da a abou o he possibly ele an impac ca ego ies (e.g. human oxici y po en ial) was no a ailable, and hey we e he e o e excluded om he s udy. The modeling o he s udy was done wi h GaBi LCA modeling so wa e ( e sion 7) (Thinks ep, 2017), and he CML 2001 (Ap il 2015) was used o impac assessmen . The unc- ional uni is he ea men o o mally collec ed mixed MSW in S~ ao Paulo in one yea . 2015 was selec ed as he e e ence yea : 3.8 million onnes o MSW we e o mally collec ed and ea ed in ha yea (AMLURB, 2016). The s udy akes in o accoun he en i e li e cycle o MSW in S~ ao Paulo, i.e. gene a ion, collec ion, ea men and he final disposal o was e. The ele an uni p ocesses ega ding he di e en li e cycle phases a e included in he sys em bounda ies o he s udy (see Sec ion 2.2.2 o u he in o ma ion). The s udy has a consequen ial app oach, i.e. in addi ion o he di ec emis- sions esul ing om he uni p ocesses, he s udy akes in o accoun a oided emissions esul ing om ene gy and ma e ial subs i u ion (i.e. ene gy eco e y om MSW and ecycling). The con ex si ua- ion o he s udy was conside ed as a mic o-le el decision suppo , i.e. he s udy was assumed o ha e no la ge-scale consequences on he backg ound sys em (e.g. he na ional elec ici y p oduc ion ma ke ) (EC-JRC, 2010). The e o e, he p oduced elec ici y om MSW was assumed o subs i u e a e age elec ici y p oduc ion in B azil. Hyd o (75.2%), na u al gas (8.5%), biomass (6.3%), hea y uel oil (3.5%) and nuclea (2.9%) a e he main ene gy sou ces o elec- ici y p oduc ion in B azil (Thinks ep, 2016). 2.2.1. Scena ios The scena ios conside ed in he s udy ep esen po en ial ea men me hods o MSW in S~ ao Paulo and a e s epwise im- p o emen s owa ds a mo e en i onmen ally sus ainable MSW managemen sys em in he ci y. The s a egic MSW managemen de elopmen plans o he ci y a e aken in o accoun in he sce- na ios: he ea men me hods employed in he scena ios a e p oposed in PGIRS as po en ial ea men me hods o MSW in S~ ao Paulo ecompos ing, AD and MBT. The e a e fi e main scena ios in he s udy (Scena ios 0e4). Addi ionally, he e a e sub-scena ios in Scena ios 2, 3 and 4. The sub-scena ios indica e he ea men me hod o sepa a ely collec ed o ganic was e: compos ing (X.1) o anae obic diges ion (X.2). In he baseline scena io (Scena io 0), which is he s a us quo, 100% o collec ed MSW is disposed o in landfills. Scena io 1 is a combina ion o home compos ing and landfilling: 5% o o ganic was e (i.e. 2.5% o he o al MSW) is home compos ed and he e- sidual MSW (i.e. he emaining MSW a e he sepa a ion o o ganic was e) is disposed o in landfills. A 5% home compos ing a e was chosen since he objec i e ega ding home compos ing in PGIRS is highly ambi ious: 33% home compos ing a e o o ganic was e by 2033 (P e ei u a de S~ ao Paulo, 2014). Howe e , in a sho e ime span he objec i e is no ealis ic since app oxima ely 5% o o ganic was e is compos ed in B azil a p esen (CCAC, 2015a). The e o e, we employed a mo e ealis ic a e o home compos ing in he s udy. In Scena io 2, he home compos ing o o ganic was e is accompanied by he sepa a e collec ion and ea men o o ganic was e: 20% o o ganic was e (i.e. 9.8% o he o al MSW) is ei he compos ed (Scena io 2.1) o anae obically diges ed (Scena io 2.2) and he esidual MSW is landfilled. We selec ed a 20% sepa a e collec ion a e based on he PGIRS s a egy objec i e o es ablishing new o ganic was e ea men acili ies. The aim is ha he o al ea men capaci y o he acili ies would be 19% o o al MSW gene a ion, and 40% o o ganic was e gene a ion by 2023 (CCAC, 2015a). In iew o he cu en si ua ion, no ope a ing compos ing o AD plan s, a mo e ealis ic mid- e m goal o a 20% sepa a e collec ion and ea men a e o o ganic was e was employed in he s udy. In Scena ios 3 and 4, MBT o he esidual MSW is included in he assessmen : 20% o he esidual MSW (i.e.17.6% o he o al MSW) is ea ed in MBT plan s, while he es o he MSW is disposed o in landfills. PGIRS con ains no specific objec i es ega ding he MBT o MSW. The e o e, a ealis ic mid- e m MBT capaci y was employed, as wi h he o ganic was e ea men plan s. Scena ios 3 and 4 di e in he u iliza ion o he e use-de i ed uel (RDF) p oduced. The RDF is incine a ed in was e- o-ene gy plan s in Scena io 3, whe eas in Scena io 4, i is u ilized in cemen p oduc ion as a subs i u e o coal, which is ypically used as he p ima y uel in cemen kilns. The ea men me hod o he gene a ed o ganic ejec is ei he com- pos ing o AD, depending on he sub-scena io (Scena ios 3.1 and 4.1 /compos ing; Scena ios 3.2 and 4.2 /AD). The scena ios a e hie a chical (see Fig. 3), i.e. he imp o emen s eps aken in p e- ious scena ios a e also included in he ollowing scena ios. The MSW mass flows o he scena ios a e p esen ed in Table 1. 2.2.2. Sys em bounda ies and calcula ion p inciples The sys em bounda ies o he s udy (see Fig. 4) include di ec emissions om anspo a ion and ea men o MSW (including elec ici y and diesel consump ion) as well as a oided emissions esul ing om ma e ial and ene gy subs i u ion. The en i e MSW managemen sys em o S~ ao Paulo was assessed in he s udy, i.e. he s udy akes in o accoun he MSW managemen ope a ions o bo h Ecou bis and Loga. S~ ao Paulo ci y has 32 dis ic s, o which 19 a e in he ope a ion a ea o Ecou bis and 13 in he ope a ion a ea o Loga (AMLURB, 2016). The collec ion and anspo a ion o MSW was modeled o each dis ic indi idually (see supplemen a y ma e ial A). The calcula ion p inciples o anspo a ion dis ances a e p esen ed in Fig. 5. The ollowing assump ions we e made. The payload capaci y o a uck was ei he 11 o 25 onnes depending on whe he MSW was di ec ly anspo ed o a MSW managemen si e o ia a ans e s a ion. T ucks ca ied a ull payload o a MSW ea men si e and e u ned back emp y. O ganic was e was di ec ly ans- po ed o a MSW ea men si e due i s high mois u e con en . All MSW ea men plan s (i.e. compos ing, AD and MBT plan s) we e assumed o be loca ed a he cu en landfill si es, CTL and CTVA Caiei as. Using he abo e-men ioned assump ions, he emissions om anspo a ion we e calcula ed wi h he GaBi so wa e (i.e. he uni emissions o ucks we e de i ed om GaBi's da abase). Landfilling o he MSW was modeled mainly based on in o - ma ion ecei ed du ing isi s o he CTL and CTVA Caiei as landfills (si e-specific da a). The modeling was complemen ed wi h li e a- u e da a i necessa y. The me hane (CH 4 ) gene a ion po en ial (L 0 ) o MSW is one o he mos c i ical pa ame e s in e ms o he en i onmen al impac s o landfilling, pa icula ly GWP (Liikanen e al., 2017). CH 4 gene a ion po en ial was calcula ed using he ollowing equa ion: L0¼DOC DOC MCF F16 12 (1) whe e L 0 ¼CH 4 gene a ion po en ial [Gg CH4 /Gg MSW ] DOC ¼F ac ion o deg adable o ganic ca bon [Gg C /Gg MSW ] M. Liikanen e al. / Jou nal o Cleane P oduc ion 196 (2018) 150e162 153 DOC ¼Decomposable ac ion o DOC [%] MCF ¼CH 4 co ec ion ac ion [-] F¼Sha e o CH 4 in landfill gas (LFG) [%] 16/12 ¼The molecula weigh a io be ween CH 4 and C [-] (IPCC, 2006). L 0 is he o al amoun o CH 4 gene a ed in he decomposi ion o MSW. Since CH 4 gene a ion con inues o decades a e he disposal o MSW (IPCC, 2006), L 0 was employed in modeling in o de o ake in o accoun he en i e li e cycle o MSW. Da a used in he modeling o landfilling, including he abo e-desc ibed L 0 , is p esen ed in supplemen a y ma e ial B. The home compos ing o o ganic was e was modeled based on li e a u e da a (Ande sen e al., 2012;Bold in e al., 2009). I was assumed ha he gene a ed compos subs i u ed mul inu ien e ilize s in domes ic use. The subs i u ed mul inu ien e ilize was a NPK e ilize con aining ni ogen, phospho us and po as- sium a he same p opo ion (each 15% o he o al con en ). Da a used o model he en i onmen al impac s o home compos ing is p esen ed in supplemen a y ma e ial C. Since he e we e no ope a ional compos ing o AD plan s in S~ ao Paulo in 2016, when he da a o he s udy was collec ed, bo h ea men p ocesses we e modeled based on li e a u e da a. The s udies o Bold in e al. (2009),B own e al. (2008) and Pagans e al. (2006) we e u ilized in modeling o he compos ing p ocess (see supplemen a y ma e ial C o u he in o ma ion). Wind ow compos ing was assumed o he compos ing echnology. I was conside ed as a po en ial compos ing echnology in he case a ea since i is a a he simple and consequen ly low-cos compos ing echnology, and i has been applied in B azil (San os e al., 2017). The gene a ed compos was assumed o subs i u e simila mul i- nu ien e ilize as in he home compos ing p ocess. The AD p ocess was modeled based on he s udies o Angelidaki e al. (2006),Be glund and B€ o jesson (2006),Ha ukainen e al. (2017), Mølle e al. (2002) and Nielsen e al. (2010) (see supplemen a y ma e ial C o u he in o ma ion). The gene a ed diges a e was assumed o be wind ow compos ed. As in he compos ing p ocess, he gene a ed compos om pile compos ing was assumed o subs i u e con en ional NPK e ilize . MBT o he MSW was also modeled based on li e a u e da a due o a lack o si e-specific da a - he e we e no ope a ing MBT plan s in S~ ao Paulo in 2016. The s udies o Damgaa d e al. (2009),Leme e al. (2014) and Nas ullah e al. (2015) we e employed in he modeling o MBT (see supplemen a y ma e ial D o u he in o - ma ion). Compos gene a ed om mechanically sepa a ed o ganic ejec (app oxima ely 28% o inpu MSW) was assumed o be used as a landfill co e ma e ial ins ead o e ilize due o he lowe compos quali y. Mechanically sepa a ed o ganic ejec con ains mo e ha m ul subs ances (e.g. hea y me als) and o he unwan ed ma e ials (e.g. plas ic) han sou ce sepa a ed o ganic was e (Di Lona do e al., 2012), which may es ic he u iliza ion o compos in e ilizing, soil imp o emen and landscaping pu poses. The ea men o o ganic ejec (i.e. compos ing o AD) was Fig. 3. Scena ios o he s udy. Table 1 Mass flows o MSW in he scena ios. Scena io Landfill [k ] T ea men o o ganic was e [k ] MBT [k ] P Home compos ing Compos ing plan AD Incine a ion Cemen kiln 0 3800 eeeee3800 1 3707 93 eeee3800 2.1 3335 93 372 ee e 3800 2.2 3335 93 e372 ee 3800 3.1 2668 93 372 e667 e3800 3.2 2668 93 e372 667 e3800 4.1 2668 93 372 ee 667 3800 4.2 2668 93 e372 e667 3800 M. Liikanen e al. / Jou nal o Cleane P oduc ion 196 (2018) 150e162154 o he wise modeled simila ly as desc ibed abo e. Incine a ion o he RDF was modeled based on he s udies o As up e al. (2009),Bi gisd o i e al. (2006),Consonni e al. (2005), Ha ukainen e al. (2017),Hupponen e al. (2015),Leme e al. (2014) and Mendes e al. (2004) (see supplemen a y ma e ial D o u he in o ma ion). The u iliza ion o RDF in cemen p oduc ion as a subs i u e uel o coal was calcula ed based on he ene gy con en (lowe hea ing alue, LHV) o RDF. A oided acquisi ion (i.e. mining, p ocessing and anspo a ion) and combus ion o ha d coal in cemen p oduc ion we e aken in o accoun in he s udy, whe eas o he emissions om cemen p oduc ion we e excluded om he assessmen . 3. Resul s and discussion 3.1. Con ibu ion analysis In con ibu ion analysis, he o al esul is decomposed in o indi idual p ocess con ibu ions (Cla eul e al., 2012). The GWPs o he scena ios a e p esen ed in his manne in Fig. 6. Scena ios 4.2 and 4.1 clea ly had he lowes GWPs, whe eas he GWPs o he Scena ios 3.1 and 0 we e he highes . The GWPs o he o he Fig. 4. Sys em bounda ies o he s udy. M. Liikanen e al. / Jou nal o Cleane P oduc ion 196 (2018) 150e162 155 scena ios (Scena ios 1, 2.1, 2.2 and 3.2) we e lowe compa ed o he baseline scena io (Scena io 0) bu no significan ly. I is no ewo hy ha he MBT o MSW and incine a ion o RDF (Scena io 3) did no dec ease he GWP o MSW managemen in S~ ao Paulo due o he a e age elec ici y p oduc ion in B azil (app oxima ely 75% hy- d opowe ) equi e he con a y. Indeed, elec ici y p oduc ion om Fig. 5. Calcula ion p inciples o anspo a ion dis ances. Fig. 6. GWPs o he s udied scena ios. M. Liikanen e al. / Jou nal o Cleane P oduc ion 196 (2018) 150e162156 RDF gene a ed no ably mo e emissions compa ed o he a e age elec ici y p oduc ion in B azil. In o he wo ds, he di ec emissions o elec ici y p oduc ion om RDF incine a ion ou weighed he a oided emissions om elec ici y subs i u ion (a e age elec ici y p oduc ion in B azil), which led o an un a o able ou come o u iliza ion o he RDF in was e incine a ion plan s. The e o e, RDF should a he be u ilized in cemen p oduc ion (Scena io 4). As ega ds di e en ea men op ions o sepa a ely collec ed o ganic was e, he GWP esul s indica e ha AD (Scena ios 2.2, 3.2 and 4.2) is be e op ion han compos ing (Scena ios 2.1, 3.1 and 4.1). Home compos ing o o ganic was e (Scena io 1) dec eased he GWP o MSW managemen sligh ly. The APs o he scena ios a e p esen ed in Fig. 7. Scena ios 4.2 and 4.1 had he lowes APs, while he APs o Scena ios 3.1 and 3.2 we e he highes . I is no ewo hy ha he APs o all scena ios, excep Scena ios 3.1 and 3.2, we e nega i e, i.e. a oided emissions we e g ea e han di ec emissions, mainly due o elec ici y sub- s i u ion. The esul s ma ched obse a ions ound in he GWP ca ego y e he MBT o MSW and incine a ion o RDF a e no beneficial in his impac ca ego y ei he due o he low amoun o a oided emissions esul ing om elec ici y subs i u ion and, espec i ely, he high amoun o di ec emissions gene a ed in he incine a ion p ocess. Combus ion in a cemen kiln is he e o e a be e u iliza ion op ion o RDF han was e incine a ion o elec- ici y gene a ion in his ega d, oo. The AP o he baseline scena io was also nega i e, i.e. beneficial o he en i onmen . The landfill p ocesses inflic ed conside ably less di ec emissions (e.g. he use o bulldoze s) compa ed o he a oided emissions achie ed in elec- ici y p oduc ion om LFG. As in he GWP impac ca ego y, i was mo e beneficial o he sepa a ely collec ed o ganic was e o be anae obically diges ed a he han compos ed. The compos ing o o ganic was e, including home compos ing, inc eased he AP o MSW managemen compa ed o Scena io 0. The EPs o he scena ios a e p esen ed in Fig. 8. As can be seen, he esul s we e consis en wi h he p e ious main findings in he GWP and AP impac ca ego ies: AD is a be e ea men op ion o Fig. 7. APs o he s udied scena ios. M. Liikanen e al. / Jou nal o Cleane P oduc ion 196 (2018) 150e162 157 sepa a ely collec ed o ganic was e, and usage in cemen p oduc ion is a be e u iliza ion op ion o RDF han incine a ion. As in he AP impac ca ego y, he home compos ing o o ganic was e inc eased he EP o MSW managemen . Howe e , in his ega d, he esul s we e no consis en ac oss he impac ca ego ies because home compos ing dec eased he GWP o MSW managemen . 3.2. Sensi i i y analysis The modeling assump ion ega ding he kind o elec ici y p oduc ion subs i u ed by elec ici y p oduc ion om MSW was c ucial in e ms o he o al esul s in all he impac ca ego ies. In he s udy, i was assumed ha he elec ici y p oduced would subs i u e a e age elec ici y p oduc ion in B azil, which is mainly (~75%) hyd opowe . Ins ead o a e age elec ici y p oduc ion, he p oduced elec ici y could also subs i u e ma ginal ene gy p o- duc ion. Na u al gas is ega ded as he mos likely uel o ma ginal elec ici y p oduc ion in B azil in he o eseeable u u e (Be ns ad Sa ai a e al., 2017). Na u al gas, as he second la ges ene gy sou ce a e hyd opowe , cons i u es a a he la ge p opo ion (8.5%) o he a e age elec ici y p oduc ion mix in B azil. The e o e, i is easonable o selec i o sensi i i y analysis as an al e na i e subs i u ed elec ici y p oduc ion. In addi ion o na u al gas, hea y uel oil was chosen as ano he al e na i e ene gy sou ce o elec ici y subs i u ion in sensi i i y analysis. Hea y uel oil is he ou h la ges ene gy sou ce (3.6%) in he a e age elec ici y p o- duc ion mix in B azil and is en i onmen ally he mos un a o able (GWP, AP and EP impac ca ego ies) al e na i e o he main ene gy sou ces in a e age elec ici y p oduc ion in B azil. The e o e, i p esen s simul aneously he wo s -case scena io o elec ici y p oduc ion and he bes -case scena io o elec ici y subs i u ion e he mo e a oided emissions esul ing om elec ici y subs i u ion, he mo e a o able he ou come o elec ici y p oduc ion om MSW. The influence o di e en elec ici y subs i u ion op ions on he esul s was in es iga ed by de e mining he weigh ed esul s o he scena ios wi h al e na i e ene gy sou ces (a e age elec ici y p o- duc ion mix e sus na u al gas and hea y uel oil). Thus, he anking be ween he scena ios wi h di e en elec ici y subs i u- ion assump ions can be iden ified. The aim was o find ou whe he di e en elec ici y subs i u ion assump ions make ce ain ea men me hods (e.g. incine a ion) en i onmen ally mo e a o able ela i e o he baseline scena io. The esul s we e weigh ed ela i e o he esul o he baseline scena io, Scena io 0 (see Fig. 9). The esul o Scena io 0 is ze o (0.0). I he ela i ely weigh ed esul (RWR) o a gi en scena io is >0.0, he scena io is a be e op ion han Scena io 0. Respec i ely, i he RWR o a gi en scena io is <0.0, he scena io is wo se op ion han Scena io 0. Thus, Fig. 8. The EPs o he scena ios. M. Liikanen e al. / Jou nal o Cleane P oduc ion 196 (2018) 150e162158