INPUT-OUTPUTANDHYBRIDLCA
Towardsatriplebottom-linesustainabilityassessmentoftheU.S.constructionindustry
MuratKucukvar&OmerTatari
Received:26April2012/Accepted:2January2013/Publishedonline:14February2013#Springer-VerlagBerlinHeidelberg2013
Abstract
PurposeTheconstructionindustryhasconsiderableimpactsontheenvironment,economy,andsociety.Althoughquantifyingandanalyzingthesustainabilityimpli-cationsofthebuiltenvironmentisofgreatimportance,ithasnotbeenstudiedsufficiently.Therefore,theoverarchinggoalofthisstudyistoquantifytheoverallenvironmental,economic,andsocialimpactsoftheU.S.constructionsec-torsusinganeconomicinput–output-basedsustainabilityassessmentframework.
MethodsInthisresearch,thecommodity-by-industrysup-plyandusetablespublishedbytheU.S.BureauofEconomicAnalysis,aspartoftheInternationalSystemofNationalAccounts,aremergedwitharangeofenvironmen-tal,economic,andsocialmetricstodevelopacomprehen-sivesustainabilityassessmentframeworkfortheU.S.constructionindustry.Afterdeterminingthesesustainabilityassessmentmetrics,thedirectandindirectsustainabilityimpactsofU.Sconstructionsectorshavebeenanalyzedfromatriplebottom-lineperspective.
ResultsWhenanalyzingthetotalsustainabilityimpactsbyeachconstructionsector,“ResidentialPermanentSingleandMulti-FamilyStructures\"and\"OtherNon-residentialStructures\"arefoundtohavethehighestenvironmental,economic,andsocialimpactsincomparisonwithotherconstructionsectors.Theanalysisresultsalsoshowthatindirectsuppliersofconstructionsectorshavethelargestsustainabilityimpactscomparedwithon-siteactivities.Forexample,forallU.S.constructionsectors,on-siteconstruc-tionprocessesarefoundtoberesponsibleforlessthan5%
Responsibleeditor:AlessandraZamagni
M.Kucukvar:O.Tatari(*)
DepartmentofCivil,EnvironmentalandConstructionEngineering,UniversityofCentralFlorida,Orlando,FL32816,USA
e-mail:tatari@ucf.edu
oftotalwaterconsumption,whereasabout95%oftotalwaterusecanbeattributedtoindirectsuppliers.Inaddition,Scope3emissionsareresponsibleforthehighestcarbonemissionscomparedwithScopes1and2.Therefore,usingnarrowlydefinedsystemboundariesbyignoringsupplychain-relatedimpactscanresultinunderestimationoftriplebottom-linesustainabilityimpactsoftheU.S.constructionindustry.
ConclusionsLifecycleassessment(LCA)studiesthatcon-sideralldimensionsofsustainabilityimpactsofcivilinfra-structuresarestilllimited,andthecurrentresearchisanimportantattempttoanalyzethetriplebottom-linesustain-abilityimpactsoftheU.S.constructionsectorsinaholisticway.Webelievethatthiscomprehensivesustainabilityas-sessmentmodelwillcomplementpreviousLCAstudiesonresourceconsumptionofU.S.constructionsectorsbyeval-uatingthemnotonlyfromenvironmentalstandpoint,butalsofromeconomicandsocialperspectives.
KeywordsEconomicinput–outputanalysis.Lifecycleassessment.Sustainabilityassessment.Triplebottomline.U.S.constructionindustry
1Introduction
1.1TheU.S.builtenvironment
Theconstructionindustryconsistsprimarilyofestablish-mentsrelatedtoconstructing,renovating,anddemolishingbuildingsandotherengineeringstructures.Theconstructionindustryincludescontractorsincommercial,residential,highway,heavyindustrial,andmunicipalutilityconstruc-tion(U.S.EPA2010).IntheUnitedStates,theconstructionsectorsaccountedfor$611billion,or4.4%ofthegrossdomesticproduct(GDP),morethanmanyindustries,in-cludinginformation,artsandentertainment,utilities,
IntJLifeCycleAssess(2013)18:958–972agriculture,andmining(BEA2010).Additionally,construc-tionsectorsareoneofthemaincontributorstothedepletionofnaturalcapital,andasignificantsourceofenvironmentalpollutions,suchasair,water,andsoil,solidwastegenera-tion,landuse,toxicwastes,healthhazards,andglobalclimatechange.Forexample,intheU.S.,80%ofallresourcesbymassareemployedinconstruction,renovation,andretrofitofbuildingsandinfrastructures(GradelandAllenby2009).Buildingsandinfrastructurealsoaccountforapproximately30%oftherawmaterialsand25%ofthewaterusedannuallyintheU.S.Inaddition,constructionprojectsannuallygenerate164,000milliontonsofwasteanddemolitiondebris,whichaccountsforabout30%ofthecontentinlandfills(NRC2009).1.2Environmentallifecycleassessment
Duetothefactthatthebuiltenvironmenthassignificantimpactsontheenvironment,itisnecessaryfortheconstructionindustrystakeholderstoaddresstheissuesrelatedtosustain-ableconstruction.Today,manyconstructioncompanieshavegivenasubstantialimportancetosustainabilityandresourceconservation,andthereforetheenvironmentallifecycleas-sessment(LCA)ofconstructionactivitieshavebecomeasubjectofconsiderableinterestglobally(Sharrardetal.2005).LCAwasintroducedintheearly1990sasahands-ontooltoevaluatethepotentialenvironmentalinterventionsbyprovidingcomplimentaryinsights,apartfromcurrentregu-latorypracticesandtohelpreducetheoverallenvironmentalimpacts(Rebitzeretal.2004).LCAisawidelyusedap-proachtoassessthepotentialenvironmentalimpactsandresourcesusedthroughoutaproduct’slifecycle,includingrawmaterialacquisition,production,use,andend-of-lifephases(Finnvedenetal.2009).Themostsignificantstrengthofthisapproachisthatitconsidersthewholeproductlifecyclesoastoavoidproblemsassociatedwithdefiningalimitedscope.
LCA-baseddecisionsupporttoolshavealsobeendevel-opedforanalyzingtheenvironmentalimplicationsofbuild-ingsandbuildingmaterialsbothintheEuropeandUnitedStates(HaapioandViitaniemi2008).Togiveafewexam-ples,ENVESTwasdevelopedinUKtoquantifytheenvi-ronmentalimpactsofbuildingsconsideringmaterialsutilizedinconstructionandmaintenance(TatariandKucukvar2012a).Inadditiontothat,theBuildingEnvironmentalAssessmentTool,whichwasdevelopedbytheDanishBuildingandUrbanResearchInstitute,providesaLCA-basedinventoryanddatabaseforthelifecycleassessmentofbuildingproducts,aswell(ForsbergandMalmborg2004).ATHENA,whichestimatesthelifecycleenvironmentalimpactsofconstructionmaterialsandbuild-ingsystems,wasdevelopedbytheAthenaSustainabilityInstituteinNorthAmericaasadecisionsupporttoolfor
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buildings(SeoandHwang2001).TheU.S.NationalInstituteofStandardsandTechnologyhasalsodevelopedBuildingsforEnvironmentalandEconomicSoftwaretoselectenvironmentalandeconomicallybalancedbuildingmaterialsforcommercialandresidentialbuildings(Lippiat2007).TheNationalRenewableEnergyLaboratory(NREL)LifeCycleInventorydatabasewhichwasdevelopedbytheAthenaInstituteandNRELprovidessomedataonbuildingmaterialproductionandtransportation;however,itdoesnotprovideanyinformationregardingconstructionprocesses(NRL2012).
1.3ApplicationsoftheEIO-LCAtoconstructionindustryTheaforementionedLCA-basedenvironmentaldecisionsupportmodelsanalyzethelifecycleenvironmentalimpactsofsomebuildingmaterials;however,theyarenotabletoconsidertheindirectimpactsofconstructionsectors,includ-ingnon-residentialheavycivilinfrastructures.Inthisregard,economicinput–output-basedlifecycleassessment(EIO-LCA)hasbeenutilizedextensivelytoanalyzetheenviron-mentalimpactoftheconstructionindustry.TheEIO-LCAmodelaugmentstheenvironmentalimpactdatawiththeeconomicinput–outputtablestoformacomprehensivesys-temboundaryandiswidelyusedforquantifyingtheenvi-ronmentalpressuresofproductsorprocessesbytracingtheentiresupplychain(Hendricksonetal.2005;Joshi2000;Lenzenetal.2003).
SeveralinterestingapplicationsoftheEIOanalysisarefoundintheliteraturefortheenvironmentalanalysisofbuildingsandotherengineeringstructures.Forinstance,HendricksonandHorvath(2000)estimatedthemajorcom-modityandserviceinputs,resourcerequirements,environ-mentalemissions,andwastesforfourmajorU.S.constructionsectors,includinghighway,bridge,andotherhorizontalconstruction,industrialfacilities,andcommercialandofficebuildings,residentialone-unitbuildings,andotherconstructionssuchastowers,water,sewerandirriga-tionsystems,railroads,etc.HendricksonandHorvathquan-tifiedalldirectandindirectmaterial,energy,andserviceinputsfortheseconstructionsectorsusingtheEIO-LCAmodel.Inaddition,Ochoaetal.(2002)estimatedthetotalresource,fossilenergy,greenhousegasemissions(GHG),hazardouswastegeneration,andtoxicreleasesintoairfortheconstruction,use,anddemolitionphasesoftheU.S.residentialbuildingsbyusingtheEIO-LCAmodel,whichconsideredtheinteractionamong480sectorsintheUnitedStates.JunnilaandHorvath(2003)analyzedthelifecycleenergyuseandatmosphericemissionsofnewlyconstructedEuropeanandU.S.officebuildingsfrommaterialsproduc-tionthroughconstruction,use,andmaintenancetoend-of-lifetreatmentusingtheprocess-basedLCA(P-LCA)andEIO-LCAmethodologies.
960Inanotherstudy,Bilecetal.(2006)developedacompre-hensivehybridLCAmodelcombiningboththeP-LCAandEIO-LCAmethodologiestoquantifytheatmosphericemis-sionsrelatedtoconstructionofaprecastconcreteparkinggarage.Inaddition,Sharrardetal.(2005)constructedaninput–output-basedhybridLCAmethodologytoestimatetheenvironmentalimpactsofconstructionprocesses,com-prehensively.Ontheotherhand,TatariandKucukvar(2012b)broughtadifferentapproachbyusinganecologi-callybasedLCAtooltoquantifythecumulativeecologicalresourceconsumptionsofthebuildingsandcivilinfrastruc-turesforthefirsttime.TatariandKucukvarholisticallyevaluated13U.S.constructionsectorsbyusingseveralkeysustainabilityassessmentmetrics,suchasresourcein-tensity,efficiencyratio,renewabilityratio,andloadingratio.1.4Motivationandorganizationoftheresearch
ThepreviousLCAstudieshavesuccessfullyanalyzedtheenvironmentalimpactsofbuildingsandothercivilinfra-structuresfromasystem-wideperspective.Inadditiontotheenvironment,sustainableconstructionshouldalsoin-cludetheeconomicandsocialaspects.Hence,theEIOmethodologycouldbeexpandedtoestimatetheenviron-mental,aswellastheeconomicandsocialimpactsofdifferentU.S.constructionsectors,includingresidentialandnon-residentialstructures.Thecurrentstudyaimstofillthisimportantresearchgapandaccountforthetotalsus-tainabilityimpactsoftheconstructionindustry,includingitssupplychain.ThisanalysisisachievedbyusingseveralsustainabilitymetricsaugmentedwiththeU.S.economicinput–outputtablestoreachtobetterinsightsregardingatriplebottom-linesustainabilityperformanceofthenation’sconstructionsectors.
Therestofthepaperisstructuredasfollows.First,acomprehensiveeconomicinput–outputmethodologyhasbeenpresented.Second,sustainabilityindicatorssuchasenvironmental,economic,andsocialarebrieflydefined,andtheircorrespondingdatasourcesarepresented.Next,sustainabilityimpactsoftheU.S.constructionindustryincludingresidentialandnon-residentialcon-structionsectorshavebeenpresentedwithdetails.Finally,thefindingsarediscussed,andthelimitationsarepointedout.
2Methodology
Inthisresearch,weutilizedtheEIO-basedsustainabilityaccountingapproachtoanalyzethesustainabilityoftheU.S.constructionsectorsfromaholisticperspective.TheEIOanalysisisawell-establishedmodel,whichwastheo-rizedanddevelopedbyWassilyLeontiefin1970s,basedon
IntJLifeCycleAssess(2013)18:958–972
hisearlierworksinthelate1930s,forwhichhereceivedtheNobelPrize(Leontief1936).Initsoriginalform,theEIOanalysisisatop-downtechnique,whichconsistsprimarilyoffinancialflowsandinterdependenciesbetweendifferentsectorsthatmakeuptheeconomicstructureofanation(Suhetal.2004).Intheliterature,thismethodologyhasbeenextensivelyusedtoanalyzeawiderangeofpolicyissuesinenvironmental,economic,andsocialareas,andseveralresearcherscomprehensivelyanalyzedthesustainabilityimpactsofproducts,infrastructures,energysystems,privatesectors,internationaltrade,andhouseholddemand(Huangetal.2009a;Huppesetal.2008;Lenzenetal.2003;SuhandLippiat2012;Tatarietal.2012;WeberandMatthews2007;Wiedmannetal.2011).
Inthisstudy,thesupplyandusetablespublishedbytheU.S.BureauofEconomicAnalysis(BEA2002),aspartoftheInternationalSystemofNationalAccounts,aremergedwitharangeofenvironmental,economic,andsocialsus-tainabilitymetricstodevelopacomprehensivesustainabilityassessmentframeworkfortheU.S.constructionindustry.Thecommodity-industryformatisutilizedsincethebasicinput–outputmodelpresentsthefinancialflowsbetweenindustrialsectorswithoutdistinguishingbetweenprimaryandsecondaryproducts.However,usingcommodity-industryformat,itispossibletoaccountforthefactthatanindustrycanproducemorethanonecommodity,suchassecondaryproductsandby-products(Wachsmannetal.2009).Especially,theEurostatmanualprovidesacompre-hensiveanddetaileddiscussionontheuseofthisformatintheEIOmodels(Eurostat2008).
Inthisapproach,theUsematrix,whichisusuallydenotedasU,providesinformationontheconsumptionofcommoditiesbyindustriesorbyfinaldemandcategories,suchashouseholds,government,investment,orexport.AsanelementofU,uijdenotesthevalueofcommoditypur-chaseofcommodityibyindustryjandxjrepresentsthetotaloutputofindustryj,includingimports.Therefore,bijistheamountofcommodityirequiredforproducingone-dollaroutputofindustryj.Byusingthetotalindustrialoutputofindustryj,thetechnicalcoefficientmatrixBcanbewrittenas(MillerandBlair2009):
!
B¼Âbüuijijxjð1Þ
InadditiontotheUsematrix,theMakematrix,whichisusuallydenotedascalledasV,providesdetailedinformationonproductionofcommoditiesbyindustries.Inthemaketable,eachrowrepresentstheproductionofcommoditiesbydifferentindustries.AsanelementoftheMakematrix,vjiisthevalueoftheoutputofcommodityibyindustryjandqirepresentsthetotaloutputofcommodityi.Hence,djirep-resentsthefractionoftotalcommodityioutputwhichis
IntJLifeCycleAssess(2013)18:958–972producedbyindustriesbothasmainproductaswellasby-product.Usingthetotaloutputofcommodityi,theindustry-basedtechnologycoefficientmatrixDcanbewrittenas(MillerandBlair2009):
D¼Âdà v!
ji¼jiqið2Þ
AfterdefiningBandDmatrices,anindustry-by-industryinput–outputmodelcanbeformulatedasfollows(MillerandBlair2009):
x¼hðIÀDBÞÀ1
i
fð3Þwherexrepresentsthetotalindustryoutputvector,Ireferstotheidentitymatrix,andfisthetotalfinaldemandvectorforindustries.Inaddition,Bistheinputrequirementsforprod-uctsperunitofoutputofanindustrymatrix,andDissometimescalledasmarket-sharematrix.Also,theterm[(I−DB)−1]representsthetotalrequirementmatrix,whichisalsoknownastheLeontiefinverse,andDBisthedirectrequirementmatrix,whichisrepresentedbyAmatrixintheLeontiefinput–outputmodel(Leontief1970).Formoredetailedinformationontransformationofthesupplyandusetablesintoasymmetricindustry-by-industrymodel,pleaseseethereferencereportspreparedbytheEurostatandtheUnitedNations(Eurostat2008;UN1999).
Afteranindustry-by-industryinput–outputframeworkhasbeenestablished,totalsustainabilityimpacts(directandindirect)caneasilybecalculatedbymultiplyingthefinaldemandofasectorwiththemultipliermatrix.Then,avectoroftotalsustainabilityimpactscanbeformulatedasfollows:
r¼Ehdirx¼EdirðIÀDBÞÀ1
i
fð4Þwhererdenotesthetotal-impactsvectorthatrepresentsoverallsustainabilityimpactsperunitoffinaldemand,andEdirrepresentsadiagonalmatrix,whichconsistsofthedirectenvironmental,economic,orsocialimpactvaluesperdollarofoutputforeachindustrialsector.Eachelementofthisdiagonalmatrixissimplycalculatedbydividingthetotaldirectsectoralimpact(e.g.,waterconsumption,GHGemissions,income)withtotaleconomicoutputofthatsec-tor.Inaddition,−1theproductofEdirandthebracketedterm[(I−DB)]representsthemultipliermatrix.
UsingapowerseriesexpansionoftheLeontiefinverse,itisalsopossibletoaccountfortheimpactsofdirectandindirectsuppliersonenvironmental,economic,andsocialimpactcategories.Equation5presentsthemathematicalframeworkofthepowerseriesapproximationoftheLeontiefinversethatisappliedinourresearch(Hendricksonetal.2005):
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x= [(I+(DB) + (DB)2+ (DB)3+. . . ...)]fL1 L2L3 and higherð5Þ
Usingthispowerseriesapproximation,theresultsarepresentedinthreedifferentlayerstoaccountforthecontri-butionofhigh-ordersupplierstoeachsustainabilityindica-tor.Inthisanalysis,Layer1(L1)representseachconstructionsectoritself,whichiscontributingwithon-siteactivitiesthroughdirectuseofenergyorwater,aswellasdirecteco-nomicandsocialimpacts.Layer2(L2)accountsforcontribu-tionsfromalldirectsupplierstoU.S.constructionssectors.Finally,Layer3(L3)andhigherrepresentthesuppliersofthesuppliersandotherhigh-ordersuppliersintheU.S.economy.
3Sustainabilityassessmentindicators
Weutilizedtheinput–outputanalysistobuildacomprehensivesustainabilityassessmentframeworkoftheU.S.economyusingnumerousenvironmental,economic,andsocialindica-tors.Thesesustainabilityindicatorsareconsideredasmulti-pliersandwillbethenusedtoanalyzeeachoftheU.S.constructionsectors.Afterdeterminingthesesustainabilityassessmentmetrics,wequantifythedirectandindirectsustain-abilityimpactsoftheU.Sconstructionindustryfromatriplebottom-lineperspective.3.1Economicindicators
Firstly,grossoperatingsurplus(GOS),contributiontoGDP,andimportareselectedaskeyeconomicindicatorsandarepresentedintermsofmillionsofdollars($M).ThevaluesoftheseeconomicindicatorsareobtainedfromtheU.S.input–outputtables(BEA2002).Althoughitwasnotusedforasustainabilityanalysisofconstructionsec-tors,theseindicatorsweremergedwiththeEIOanalysisbeforetoprovideamacro-levelsustainabilityaccountingframework(Foranetal.2005;WiedmannandLenzen2008).Theseeconomicindicatorsofsustainabilityaredefinedasfollows:&
GOSisobtainedasaresidualformostindustriesaftersubtractingtotalintermediateinputs,compensationofemployees,andtaxesfromtotalindustryoutput(Eurostat2008).GOSisapositiveeconomicindicatorsinceitrepresentsthecapitalavailabletosectors,whichallowthemtorepaytheircreditors,topaytaxes,andtofinancetheirinvestments.
&
GDPisusedasanotherusefuleconomicindicator.GDPrepresentsthemarketvalueofgoodsandserv-icesproducedwithinthecountryinagivenperiodoftime.GDPisapositiveeconomicindicatorthat
962monitorsthehealthofanation’seconomyandincludescompensationofemployees,grossoperatingsurplus,andnettaxesonproductionandimports(LenzenandDey2002).Thispositiveeconomicindi-catoristhedirectandindirectcontributionofonesectortoGDP.
&
Importsrepresentthevalueofgoodsandservicespurchasedfromforeigncountriestoproducedomesticcommoditiesbyindustries(Wiedmannetal.2009)Importscanbeconsideredasanegativeindicatorduetothefactthatanexcessofimportsmeansanincreaseinthecurrentdeficitthroughtheflowofmoneyoutofthecountry.Thiseconomicindicatoraccountsforthedirectandindirectcontributionsofonesectortoforeignpurchases.
3.2Socialindicators
Socialindicatorsofsustainabilityarealsocriticalsincetheyareconsideredanintegralpartofthelifecyclesustainabilityassessmentframeworkthatanalyzesenvironmental,eco-nomic,andsocialdimensionsofsustainabledevelopment(Guinéeetal.2011;Klöpffer2008;Zamagni2012).Inthisstudy,threesocialindicatorssuchasincome($M),taxes($M),andwork-relatedinjuries(numberofemployee)areselectedasprominentsocialindicatorsandobtainedfromfederallyavailablepublicdatasources.Thesesocialsustain-abilityindicatorsaredefinedasfollows:&
Incomeisconsideredanimportantsocialindicatorsinceitcontributestothesocialwelfareofhouseholdsandrepresentsthecompensationofemployees,includingwagesandsalaries(Wiedmannetal.2009).TheincomegeneratedbyeachindustrialsectorisobtainedfromtheU.S.input–outputtables(BEA2002).
&
Taxesarechoseninthisstudyasapositivesustainabilityindicatorsincecollectedtaxeswillbeusedforsupport-ingthenationalhealthandeducationsystems,publictransportation,highways,andothercivilinfrastructures(Foranetal.2005).Taxesarereferredtoasgovernmentrevenue,whichincludesthetaxesonproductionandimports.ThedatasourcefortaxesgeneratedbyeachsectoristheU.S.input–outputtables(BEA2002).&
TheU.S.constructionindustryaccountsforthelargestshareofwork-relatedinjuriesandillnesses,andresultsinlosesinwageandproductivityofhouseholds(Waehreretal.2007).Hence,injuryisacriticalindicatorofsocialsustainabilitythathasasignificantimpactonthequalityoflife.Thisnegativeindicatorrepresentsthetotalnumberofnon-fatalinjuriesatindustrialfacilities.ThedataincludingthenumberoftotalworkplaceinjuriesaregatheredfromtheU.S.BureauofLabor
IntJLifeCycleAssess(2013)18:958–972
Statistics(BLS)toinvestigatethecontributionsoftheU.S.constructionsectorstowork-relatedinjuries(BLS2002).TheBLSprovidespubliclyavailabledata,whichpresenttherateofnon-fatalinjuriesper100equivalentfull-timeemployees.TocalculatethetotalnumberofdirectinjuriesforeachU.S.sector,thetotalnumberoffull-timeemployeesisthenmultipliedwithcorrespondingincidenceratesper100full-timeworkers.
3.3Environmentalindicators
TheUnitedNationsEnvironmentProgram(UNEP)hasrecent-lyreleasedemergingenvironmentalconcernsandrankedwaterscarcity,globalclimatechange,andenergyresourcedepletionamongthemostimportantemergingissuesrelatedtotheglobalenvironment(UNEP2012).WiththeaimofanalyzingthedirectandindirectcontributionsoftheU.S.constructionsec-torstotheaforementionedmajorthemesoftheglobalenviron-ment,water,carbon,andenergyfootprintcategorieshavebeenpresentedinouranalysis.Thediagonalenvironmentalimpactmatrixesincludingthevalueoftheseenvironmentalindicatorsper$MoutputofeachindustrialsectorisobtainedfromtheEIO-LCAmodel,whichwasdevelopedbytheGreenDesignInstituteatCarnegieMellonUniversity(CMU2002).TheseenvironmentalfootprintcategorieswereusedinconjunctionwiththeEIOanalysisforsector-levellifecycleimpactassess-ment(Blackhurstetal.2010;Matthewsetal.2008;Williams2004).
Severalecologicalfootprinttypes,suchasfishery,graz-ing,forestry,cropland,andcarbondioxide(CO2)uptakelandarealsoanalyzedforeachconstructionsector.Theecologicalfootprintisdefinedasameasureofhowmuchareaofbiologicallyproductivelandandwateranindividual,population,oractivityrequirestoproducealltheresourcesitconsumesandtoabsorbthewaste(Wackernagel2009).Inthisanalysis,ecologicalfootprintindicatorsarealsoconsid-eredasapartoftheenvironmentaldimensionofthesus-tainability,andtheseindicatorshavealreadybeenusedasameasureofenvironmentalsustainabilityinpreviousinput–outputstudies(LenzenandMurray2001;McDonaldandPatterson2004;Wiedmannetal.2009).Theglobalhectarevaluesassociatedwithfishery,grazing,forestry,cropland,andCO2uptakelandareobtainedfromtheGFNandallo-catedto426U.S.sectorsbasedontheirresourceconsump-tionsandCO2emissions(GFN2010a).Theaforementionedenvironmentalindicatorsarebrieflyexplainedasfollows:&
Thewaterfootprintisameasureofdirectandindirectwaterusedbyeachindustrialsector.TheEIO-LCAmodelusestheUnitedStatesGeologicalSurvey(USGS)datatoestimatedirectwaterwithdrawals
IntJLifeCycleAssess(2013)18:958–972foreachconsumptioncategorysuchaspowergener-ation,irrigation,industrial,livestockandaquaculture,mining,publicsupply,anddomesticwateruse.SomeoftheseUSGScategoriesarethenallocatedtodiffer-entindustrialsectorsthatareintheU.S.economicinput–outputtable(Blackhurstetal.2010).Allwaterfootprintresultsarepresentedintermsofcubicmeter.&
Thecarbonfootprintisameasureofthetotalamountofcarbondioxide,nitrogenoxides,andmethaneemis-sionsfromfossilfuelcombustion.Inthisanalysis,carbonfootprintcalculationsarebasedondifferentscopeswhicharesetbytheWorldResourcesInstitute(WRI)andtheWorldBusinessCouncilforSustainableDevelopmentinwhichallpossibleindirectemissionsfromaconstructionsectorareconsidered(WRI2004).Scope1includesdirectGHGemissionsfromacon-structionsector,includingon-siteemissionsfromnatu-ralgas,oil,anddieselcombustion.Scope2GHGemissionsaccountforindirectemissionsfromthegen-erationofelectricityusedbyeachconstructionsector(WoodandDey2009).Finally,Scope3emissionsareallindirectemissions(notincludedinScope2)thatoccurinthevaluechainoftheconstructionsectors,includingallupstreamemissions.Allscope-basedcar-bonfootprintresultsarepresentedintermsofmetrictonsofCO2equivalents.
&
Theenergyfootprintofeachsectoriscalculatedbysummingtheenergycontentofdifferentfossilfuelsandelectricityfromnon-fossilsources.Theconsump-tionvaluesofmajorfuelsbyindustrialsectorsareobtainedfromtheusingtheU.S.input–outputtables(Joshi2000).Thequantitiesoffuelconsumptionsarebasedontheaverageproducerpriceofindividualfuelsandarepresentedintermsoftera-joules.
&
Thecroplandfootprintrepresentsthemostbio-productiveofallthelandusetypesandincludesareasusedtoproducefoodandfiberforhumanconsumption,feedforlivestock,crops,andrubber(GFN2010b).TheNationalFootprintAccountscalculatethecroplandfootprintaccordingtotheproductionquantitiesof164differentcropcategories.Thetotalecologicalfootprintofcroplanduse(1.08globalhectares(gha)percapita)isallocatedtotheU.S.agriculturalsectorscompletely.&
Thegrazinglandfootprintiscalculatedbycomparingtheamountoflivestockfeedavailableinacountrywiththeamountoffeedrequiredforthelivestockproducedinthatyear,withtheremainderoffeeddemandas-sumedtocomefromgrazingland(GFN2010b).Thetotalecologicalfootprintofgrazinguse(0.14ghapercapita)isallocatedtotheU.S.agriculturalsectors.&
Theforestlandfootprintiscalculatedbasedontheamountoflumber,pulp,timberproducts,andfuelwoodconsumedbyacountryonayearlybasis(GFN2010b).
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Thetotalecologicalfootprintofforestuse(1.03ghapercapita)isallocatedtotheU.S.forestrynurseries,forestproducts,andtimbertrackssector.
&
Thefisherylandfootprint,inotherwords,fishinggroundsfootprintiscalculatedusingestimatesofthemaximumsustainablecatchforavarietyoffishspecies.Thecalculationisbasedontheestimatedprimarypro-ductionrequiredtosupportthefishcaught(GFN2010b).AssignedcompletelytotheU.S.fishingsectoristhetotalecologicalfootprintoffishingground(0.10ghapercapita).
&
TheCO2uptakelandiscalculatedastheamountofforestlandrequiredtoabsorbgivencarbonemissions(GFN2010b).CO2emissions,generat-edprimarilyfromthefossilfuelcombustion,ac-countforthelargestportionofnation’secologicalfootprint.ThetotalCO2emissionsrelatedtofuelconsumptionofindustrialsectors,transportation,households,andgovernmentareobtainedfromtheU.S.EnergyInformationAdministration(EIA2010).Then,thetotalecologicalfootprintforCO2uptake(4.79ghapercapita)isallocatedtotheU.S.sectorsbasedontheirCO2emissions.
4ConstructionsectorsandsustainabilityassessmentTheeconomicoutputvaluesofeachU.S.constructionsec-torwereobtainedfromtheU.S.DepartmentofCommerceinput–outputtables(BEA2002).Table1listssevendiffer-entconstructionsectorsalongwiththeiracronymsand2002industryoutputs.AmongtheU.S.constructionsector,“Non-residentialCommercialandHealthCareStructures”(NR-CHCS)consistsprimarilyofdifferentstructuressuchasofficebuilding,educationalbuilding,airportbuilding,industrialwarehouse,hospital,hotel,etc.“Non-residentialManufacturingStructures”(NR-MS)includesmanufacturingplantssuchascement,aluminum,chemical,incinerator,etc.,and“OtherNon-residentialStructures”(NR-OTR)compro-misesofheavycivilinfrastructuresincludinghighway,bridge,dams,water,sewer,petroleum,gas,power,andcommunica-tionlines.Inaddition,residentialconstructionsectorsincludethe“ResidentialPermanentSingleandMulti-FamilyStructures”(R-PSMFS),and“OtherResidentialStructures”(R-OTR),andmaintenanceandrepairworksarerepresentedbythesectorsof“Non-ResidentialMaintenanceandRepair”(NR-MR)and“ResidentialMaintenanceandRepair”(R-MR),respectively.
ThedevelopedEIO-basedsustainabilityassessmentmod-elwasusedtoidentifytheenvironmental,economic,andsocialimpactsofpreviouslymentionedconstructionsectorsinaholisticway.Toachievethisgoal,theresultsarepresentedusingtwodifferentmetrics,suchas“multiplier”
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Table1U.S.constructionsectorsandtotaleconomicoutputs($M)SectorDescription
Totalindustryacronym
output($M)NR-CHCSNon-residentialCommercialand
129,239HealthCareStructures
NR-MSNon-residentialManufacturingStructures23,465NR-OTROtherNon-residentialStructures292,328R-PSMFSResidentialPermanentSitesingle
304,950andMultiFamilyStructures
R-OTROtherResidentialStructures133,483NR-MRNon-residentialMaintenanceandRepair101,516R-MRResidentialMaintenanceandRepair
47,379
and“totalimpact.”First,multiplierincorporatesdirectplusindirectsustainabilityeffects(e.g.,waterfootprint,income,tax)per$Moutputofeachconstructionsector.Second,totalimpactistheproductofmultiplierandtotaleconomicoutputofconstructionsectorforeachsustainabilityindicator.4.1Economicimpacts4.1.1GOS
WhenwelookmorecloselyatGOSmultiplier,whichisdefinedastotalGOSper$Meconomicoutput,R-MRshowsthehighestvaluescomparedwithothers.Thisresultalsoindicatesthatresidentialmaintenanceandrepairworkrequiresmorecapitaloutlaythannewcon-struction.Inaddition,residentialconstructionsectorsarefoundtohavehigherGOSmultiplierthannon-residentialconstructionsectors.R-MRsectoristhenfollowedbyR-OTRandR-PSFMSintermsofGOSmultiplier.Theon-siteconstructionactivitiescontributehighlyontotalGOSmultipliersfortheseresidentialsectors,aswell.
Fornon-residentialsectors,indirectsuppliers,includingL2,L3,andhigherareresponsibleforover60%oftotalGOS(Fig.1a).FortotalGOS,R-PSFMSandNR-OTRshowthehighestvaluesincomparisonwithotherconstructionsectors(seeFig.1b).4.1.2GDP
InadditiontoGOS,thedirectandindirectcontributionsofeachconstructionsectortoGDPisalsoinvestigated.TheanalysisresultsrevealthatGDPmultiplieristhesameforallconstructionsectors.Thisisbecausethismultiplierrepre-sentsthedualoftheinput–outputequationwhichsimplygivestheunitprice.Thecontributionofon-siteconstructionactivities(representedbyL1)toGDPhasthehigher
IntJLifeCycleAssess(2013)18:958–972
percentagevaluesfornon-residentialsectorscomparedwith
residentialones.Ontheotherhand,theindirectsuppliersareresponsibleforapproximately60%oftotalGDPgeneratedbyper$MoutputofU.S.residentialsectors(seeFig.1c).Inparallelwithtotaleconomicoutputs,R-PSFMSandNR-OTRrepresenttheconstructionsectorswiththehighestcontributiontoGDP(seeFig.1d).4.1.3Import
TheimportanalysisresultsshowthatNR-MShasthehighestimportmultiplierincomparisonwithothercon-structionsectors.L2suppliersofthissectorarerespon-sibleformorethan60%oftotalimports(seeFig.1e).ThissectorisfollowedbyR-PSFMSandR-MR,re-spectively.Fortheremainingconstructionsectors,L2supplierscontributedtoapproximately40%oftotalimport,andtherestisfoundinthehigher-ordersuppli-ers.Ontheotherhand,thereisnodirectimportrelatedtoconstructionsectors.Fortotalimportgeneratedbyeachsector,R-PSMFSandNR-OTRshowthehighestvaluesincomparisonwithotherssectors(seeFig.1f).Afurtheranalysisisalsoconductedtogainvaluableinsightsregardingtheimportsofmetallicandnon-metallicmineralssinceconstructionisthelargestconsumeroftheserawmaterialsinU.S.byweight(Horvath2004).IntheU.S.input–outputtables,themetallicandnon-metallicminerals,whicharehighlyutilizedinconstruction,arerepresentedbythesectorsof“IronOreMining(IO-M),”“Copper,Nickel,LeadandZincMining(CNLZ-M),”“StoneMiningandQuarrying(S-MQ),”“Sand,Gravel,ClayandCeramicandRefractoryMineralsMiningandQuarrying(SGCCR-MQ),”and“OtherNon-metallicMineralMiningandQuarrying(ONMM-MQ),”respectively.
Figure2apresentstotaleconomicoutput(TEO)(ex-cludingimports),aswellasoverallimportsrelatedtodirectandindirectconsumptionofmetallicandnon-metallicmineralsbasedonper$Moutputofeachconstructionsector.Analysisresultsindicatethatimportedmineralshavethelowesteconomicshare,andthehighestpercentageofmineralsconsumedbycon-structionsectorsisproduceddomestically.Toillustrate,forNR-CHCSandNR-MS,TEO(excludingimports)relatedtoproductionoftheserawmaterialsarefoundtobeover80%,andtherestisimportedfromothercountries.Amongtheconstructionsectors,residentialconstructionshavethehighestimportofmineralprod-ucts,whereasnon-residentialconstructionswhichshowthehighestTEOarefoundtohavetheminimumtotalimportofmetallicandnon-metallicminerals.Inaddi-tion,NR-CHCSshowmoreimportsofmetallicminer-als,suchasironorcopperthanotherconstructionsectors,whereasthehighestshareoftotalimportsare
IntJLifeCycleAssess(2013)18:958–972965
a)
R-MRNR-MRR-OTR
b)
R-MRNR-MRR-OTRR-PSMFSNR-OTR
c)
R-MRNR-MRR-OTRR-PSMFSNR-OTRNR-MSNR-CHCS0
0.20.40.60.8GDP Multiplier ($M)
1
R-PSMFSNR-OTRNR-MSNR-CHCS
0
0.10.20.30.4GOS Multiplier ($M)
0.5
NR-MSNR-CHCS
0.0E+003.0E+046.0E+049.0E+041.2E+05Total GOS ($M)
d)
R-MRNR-MRR-OTR
e)
R-MRNR-MR
f)
R-MRNR-MRR-OTRR-PSMFSNR-OTRNR-MSNR-CHCSR-OTRR-PSMFSNR-OTRNR-MSNR-CHCS
R-PSMFSNR-OTRNR-MSNR-CHCS
0.0E+008.0E+041.6E+052.4E+053.2E+05Total GDP ($M)
00.020.040.060.080.10.120.14
Import Multiplier ($M)
L1
L2
L3 and higher
0.E+001.E+042.E+043.E+044.E+045.E+04Total Import ($M)
Fig.1EconomicimpactsaGOSmultiplier($M),btotalGOS($M),cGDPmultiplier,dtotalGDP($M),eimportmultiplier($M),ftotalimport($M)
attributedtonon-metallicmineralsconsumptionforres-identialbuildings,asshowninFig2b.4.2Socialimpacts
generatedbyeachconstructionsector,R-PSMFSandNR-OTRshowthehighestvaluesincomparisonwithothers(seeFig.3b).4.2.2Tax
4.2.1Income
Presentedinthissectionaretheincomeresults.Basedonstudyfindings,R-PSMFSandNR-OTRhavethehighestvalueofincomemultipliercomparedwithotherconstructionsectors(Fig.3a).Ingeneral,non-residentialconstructionsectorshavehigherincomemultiplierthanresidentialsectors.Twonon-residentialconstructionsectors,suchasNR-MSandNR-MR,havethelargestincomemultiplierincomparisonwithothersectors.Additionally,forallnon-residentialU.S.con-structionsectors,approximately60%oftotalincomeisgenerateddirectly,whichisrepresentedbyL1.Onthecontrary,directemploymentimpactsarefoundtobelessthan50%oftotalincomeforU.S.residentialsectors.Amongtheupstreamsuppliers,servicesectors,in-cluding“RetailTrade,”“WholesaleTrade,”“ManagementofCompaniesandEnterprises,”“Employmentservices,”and“Architectural,EngineeringandRelatedServices”providethehighestcontributionstototalincomegeneratedbyeachresidentialsector.Whenanalyzingthetotalincome
Directandindirecttaxesgeneratedbyeachsectorarealsoinvestigated,andtheresultsarepresentedinFig.3c.L2andL3suppliersrepresent80%oftotalgovernmenttaxgener-atedfromeachconstructionsector.Inotherwords,theU.S.constructionsectorsgeneratemoretaxindirectlythantheydodirectly.Theresultsalsorevealthatresidentialconstruc-tionsectorsgenerateahigheramountoftotaltaxper$Moftheireconomicoutputincomparisonwithnon-residentialsectors,includingNR-MS,NR-OTR,andNR-MR.Fortheresidentialsectors,over90%oftotaltaxisgeneratedbyindirectsuppliers,whicharelocatedinL2,L3,andhigherlayers.Amongthesesuppliers,“RetailandWholesaleTrade,”“RealEstate,”“ElectricPowerGeneration,”“OilandGasExtraction,”“Telecommunications,”and“TruckTransportation”areresponsibleforaround80%ofindirecttaxgeneratedinthevaluechainofresidentialsectors.Whenwelookmorecloselyattotalgovern-menttaxgeneratedbyeachsector,NR-OTRandR-PSMFSrepresentthesectorswiththehighesttotaltaxgeneration(seeFig.3d).
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Fig.2Economicanalysisofmetallicandnon-metallicmin-eralconsumptionbasedonper$Moutputofconstructionsec-torsaTEO($M),bimports($M)
IntJLifeCycleAssess(2013)18:958–972
a)
R-MR
TEO (excluding imports)
Imports
NR-MRR-OTRR-PSMFS
NR-OTRNR-MSNR-CHCS
0
0.0008
0.0016
0.0024
0.0032
TEO ($M)
b)
R-MRNR-MRR-OTRR-PSMFS
IO-MCNLZ-MS-MQ
SGCCR-MQONMM-MQ
NR-OTRNR-MSNR-CHCS
00.0002
0.0004Imports ($M)
0.00060.0008
4.2.3Work-relatedinjuries
Inadditiontoincomeandtax,thedirectandindirectcon-tributionsofeachconstructionsectortowork-relatedinju-riesisalsoinvestigated.Theanalysisresultsindicatethat
injurymultiplierofeachsectorisfoundtobesimilarfornon-residentialconstructionsectors.Thecontributionofon-siteconstructionactivities(representedbyL1)toinjurieshasthehigherpercentagevaluesfornon-residentialsectorscomparedwithallresidentialconstructionsectors.ForNR-CHCS,NR-MS,andNR-MR,theon-siteactivitiesarere-sponsibleforover60%oftotalwork-relatednon-fatalinjuries(seeFig.3e).Onthecontrary,itwasfoundthatresidentialsectorhavemoreinjuriesindirectlythantheydodirectly.Inaddition,non-residentialconstructionsectorsarefoundtohavehigherinjurymultiplierincomparisonwithresidentialsectors.Fromtheanalysisresults,itisapparentthatR-PSFMSandNR-OTRrepresenttheconstructionsectorswiththehighesttotalwork-injuriesamongtheU.S.
constrictionsectors(seeFig.3f).Itisshouldalsobenotedthatincomeandinjurymultipliersshowasimilartrendandsectorswithhighincomemultiplieralsohavethehighesttotalwork-relatedinjuriesper$Meconomicoutput.4.3Environmentalimpacts4.3.1Energyfootprintanalysis
Presentedinthissectionarethetotalenergyfootprintresults.Initiallycalculatedweretheenergymultipliersofdifferentconstructionsectors.Amongtheconstructionsec-tors,R-MRhadthehighestenergymultipliercomparedwithothersectors.FollowingthissectorweretheR-PSMFSandNR-MR,respectively(Fig.4a).Theanalysisresultsalsoshowthatlessthan40%oftotalenergyfootprintcanbeattributedtodirectoron-siteconstructionactivities(repre-sentedbyL1)forallconstructionsectors.Togiveanexam-ple,forR-MR,aboutonethirdoftotalenergyconsumption
IntJLifeCycleAssess(2013)18:958–972967
a)
R-MRNR-MRR-OTRR-PSMFSNR-OTRNR-MSNR-CHCS
0
0.10.20.30.40.50.60.70.8
Income Multiplier ($M)
b)
R-MRNR-MRR-OTRR-PSMFSNR-OTRNR-MSNR-CHCS0.E+005.E+041.E+052.E+052.E+05
Total Income ($M)
c)
R-MRNR-MRR-OTRR-PSMFSNR-OTRNR-MSNR-CHCS
0
0.0090.0180.0270.0360.045Tax Multiplier ($M)
d)
R-MR
e)
R-MRNR-MRR-OTRf)
R-MRNR-MRR-OTR
NR-MRR-OTRR-PSMFSNR-OTRNR-MSNR-CHCS
0.0E+004.0E+038.0E+031.2E+041.6E+04
Total Tax ($M)
R-PSMFSNR-OTRNR-MSNR-CHCSR-PSMFSNR-OTRNR-MSNR-CHCS
00.25L1
L2
0.50.7510.0E+001.0E+052.0E+053.0E+05
Injury Multiplier (employee)
L3 and higher
Total Injury (employee)
Fig.3Socialimpactsaincomemultiplier($M),btotalincome($M),ctaxmultiplier($M),dtotaltax($M),einjurymultiplier(employee),ftotalinjury(employee)
isfoundtobeinL1,whereastwothirds(63%)oftotalenergyutilizationcanbeattributedtoindirectsuppliersofthissector,whicharelocatedinL2,L3,andhigherlayersofthesupplychain.ForR-OTR,about25%oftotalenergyconsumptioncanbeattributedtoon-siteconstructionpro-cesses,whereas75%oftotalenergyuseisfoundtobeinhigherordersuppliers.Forthisreason,itshouldbenotedthat,althoughenergyefficiencyofon-siteconstructionac-tivitiesareimportantforresidentialandnon-residentialsec-tors,supply-chain-basedenergyconsumptionstillhasadominantimpactonoverallenergyfootprint.
Basedontotalenergyconsumptionresults,R-PSMFSandNR-OTRsectorsshowthelargestenergyfootprintvaluescomparedwithotherconstructionsectors(seeFig.4b).AnalysisresultsalsoshowthattheU.S.sectors,including“ElectricPowerGeneration,Transmission,andDistribution,”“CementManufacturing,”“Trucktransportation,”“Petroleumrefineries,”“IronandSteelMillsandFerroAlloyManufacturing,”and“OilandGasExtraction”havethehigh-estcontributionstototalenergyfootprintofU.S.constructionindustryandshouldbeconsideredformoreeffectiveenergyfootprintreductionstrategies.Forexample,theU.S.GreenBuildingCouncil(USGBC2009)developedagreenbuildingratingsystem,namelyLeadershipinEnergyandEnvironmentalDesign(LEED).Inmaterialsandresources
categoryofthisratingsystem,theuseofregionallyproducedbuildingmaterialsandproductsreceivescredittowardLEEDcertification.Thefindingsofenergyfootprintanalysisalsosupportthiscreditstrategyinordertominimizetransportationdistanceofconstructionmaterialssincetrucktransportationisamongthetopthreesupplysectorswhichhavethehighestshareontotalenergyfootprints.4.3.2Waterfootprintanalysis
Figure4calsopresentsthetotalwatermultipliersofeachconstructionsector.First,R-MRandR-PSMFSarefoundtohavethehighesttotalwaterfootprintper$Meconomicoutput.Amongtheconstructionsectors,residentialcon-structionsconsumehigheramountsofwaterthannon-residentialconstructionsectorsbasedonper$Meconomicactivity.Inaddition,forallconstructionsectors,on-sitecon-structionprocessesarefoundtoberesponsibleforlessthan5%oftotalwaterconsumption,whereasabout95%oftotalwaterusecanbeattributedtoindirectsuppliers,whicharelocatedinL2,L3,andhigherlayers.Hence,itisimportanttonotethatconstructionsectorusesmoreon-sitethantheydooff-site.Basedontotalwaterfootprintresults,R-PSMFSandNR-OTRrepresenttheconstructionsectorswiththehighesttotalwaterconsumptionamounts(seeFig.4d).
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Fig.4Environmentalimpactsaenergyfootprintmultiplier(tera-joules),btotalenergyfootprint(tera-joules),cwaterfootprintmultiplier(cubicmeter),dtotalwaterfootprint(cubicmeter)
IntJLifeCycleAssess(2013)18:958–972
a)
R-MRNR-MRR-OTRR-PSMFSNR-OTRNR-MSNR-CHCS
b)
R-MRNR-MRR-OTRR-PSMFS
NR-OTRNR-MSNR-CHCS
0123456789Energy Footprint Multiplier (TJ)
0.E+008.E+052.E+062.E+063.E+06
Total Energy Footprint (TJ)
c)
R-MRNR-MRR-OTRR-PSMFSNR-OTRNR-MSNR-CHCS
0
120024003600480060007200Water Footprint Multiplier (m3)
L1
L2
d)
R-MRNR-MRR-OTRR-PSMFSNR-OTRNR-MSNR-CHCS
0.0E+00
6.0E+08
1.2E+09
1.8E+09
Total Water Footprint (m3)
L3 and higher
Whenanalyzingthesupplychainofthesetwoconstructionsectorsweremoreclosely,sectorssuchas,“ElectricPowerGeneration,Transmission,andDistribution,”“PaintandCoatingManufacturing,”“Grainfarming,”and”StoneMiningandQuarrying”arefoundtoberesponsiblefornearly80%oftotalsupply-chain-relatedwaterconsumptions.Especially,directsuppliers(representedbyL2)ofresidentialconstructionsectorsarefoundtoberesponsiblefornearly40%ofwaterfootprint,andthelargestportionofthiswaterconsumptionisattributedtoelectricpowerutiliza-tion.Therefore,anyimprovementinelectricityconsump-tionthroughincreasedenergyefficiencyoruseofnon-fossilrenewableenergysourcesmighthaveaconsiderableimpactonminimizingtheindirectwaterconsumption.4.3.3Scope-basedcarbonfootprintanalysis
TheEIOanalysisisalsoabletoidentifythebiggestcarbonhot-spotsacrosstheentiresupply-chain,andpaststudiessuggestthatusingnarrowlydefinedsystemboundarieswillgenerallyleadtosignificantunderestimatesofcarbonemis-sionsforprovidingproductsandservices(Matthewsetal.2008;Huangetal.2009b).Hence,weusedtheEIOanalysistoaccountfortheScope1,2,and3carbonemissionsofdifferentconstructionsectors.
Tohaveabetterinsightintotheemissionsofconstructionsectors,carbonfootprintmultiplier,whichaccountsforthetotalGHGemissionsper$Moutputofeachsector,hasbeenfirstlypresentedinFig.5a.AnalysisresultsrevealedthatR-MR,R-PSMFS,andNR-MRarefoundtohavethehighestcarbonfootprintmultiplierscomparedwithotherconstruc-tionsectors.ForR-MR,NR-OTR,andR-PSMFS,Scope3emissionsarefoundtobeover70%oftotalGHGemis-sions.Inaddition,NR-MRandNR-CHCSshowthehighestScope1emissionsduetohigherfossilfuelconsumptionper$Meconomicoutput.Forallconstructionsectors,Scope2emissions,whichaccountforelectricityproductionrelatedGHGemissions,havethelowestcontributiontooverallcar-bonfootprintcomparedwithScope1and3GHGemissions.Anotherimportantpointtobemadewithregardtocarbonemissionsisthatsectorswithhighertotalenergymultiplier,suchasR-MR,NR-MR,andR-PSMFS,showhightotalcarbonfootprintmultipliersinrespecttoothersectors.Thisisbasicallyduetothefactthatcarbonfootprintcalculationsofconstructionsectorsarebasedonthefossilfuelconsump-tion,suchasnaturalgas,oil,anddiesel.
IntJLifeCycleAssess(2013)18:958–972Fig.5Scopes1,2,and3carbonfootprintanalysisresults;acarbonfootprintmultiplier(tonsofCO2equivalents),btotalcarbonfootprint(tonsofCO2equivalents)
969
a)
R-MRNR-MRR-OTRR-PSMFSNR-OTR
b)
R-MRNR-MRR-OTRR-PSMFSNR-OTR
NR-MSNR-CHCS
0
120
240
360
480
600
720
NR-MSNR-CHCS
0.0E+005.0E+071.0E+081.5E+082.0E+08Total Carbon Footprint (t CO2-eqv)
Scope 2
Scope 3
Carbon Footprint Multiplier (t CO2-eqv)
Scope 1
Figure5bpresentsthetotalcarbonfootprintresultsbasedondifferentscopes.R-PSMFShavethehighestamountofcarbonfootprintincomparisonwithothers.ThissectorisfollowedbyNR-OTRandRS-OTR,respectively.Onthecontrary,NR-MSandR-MRhavethelowestGHGemis-sionscomparedwithotherconstructionsectors.Althoughthelatterhasthehighesttotalcarbonfootprintper$Meconomicoutput,itisfoundtohavethelowesttotalGHGemissionsduetoitsloweconomicoutput.
Afterquantifyingthetotalcarbonfootprint,itisimportanttoaccountforthepercentagecontributionsofdifferentindus-trialsectorstoScope3carbonemissions.Ascanbeseenfrompreviousdiscussion,Scope3emissionsareresponsibleforthehighestGHGemissionscomparedwithScopes1and2.Itiscriticaltonotethat,althoughenergyreductioninon-siteconstructionactivitiesthroughincreasedenergyefficiencyofbuildingmachineryorreducedelectricityconsumptionisimportant,thelargestportionoftotalcarbonfootprintisstillfoundinthesupplychainofthesesectors.Therefore,theimprovementsaimingtominimizethesupply-chain-relatedcarbonfootprintscanmakeasignificantimpactonoverallcarbonemissions.Whenlookedmorecloselyatsupplysec-tors,“ElectricPowerGeneration,Transmission,andDistribution,”“IronandSteelMillsandFerroalloyManufacturing,”“CementManufacturing,”“OilandGasExtraction,”“PetroleumRefineries,”and“TruckTransportation”sectorsarefoundtohavethelargestcontri-butionstototalScope3emissions.Thesesectorsareapprox-imatelyresponsiblefor80%oftotalScope3emissionsforU.S.constructionsectors.Toachieveacost-effectivecarbonfootprintreduction,thespecialfocusmightbegivenonthesesupplychainsectorstominimizethenetcarbonfootprint.4.3.4Ecologicalfootprintanalysis
Presentedinthissectionaretheecologicalfootprintanalysisresultsthatareintheunitvaluesofglobalhectares.First,ecologicalfootprintmultiplier,whichpresentstotaleco-logicalfootprintsper$Moutputofeachconstructionsector,havebeenquantifiedandpresentedinFig.6a.AnalysisresultsrevealthatR-MR,R-PSMFS,andR-OTRhavethehighesttotalecologicalfootprintmultiplierincomparisonwithnon-residentialconstructionsectors.Onthecontrary,threenon-residentialconstructionsec-tors,suchasNR-MS,NR-CHCS,andNR-OTRarefoundtohavethelowesttotalecologicalfootprintper$Meconomicoutput.Amongtheecologicalfootprintcategories,CO2uptakeland,whichisrequiredforse-questeringCO2emissionsrelatedtofossilfuelcombus-tionandelectricitygeneration,isresponsibleforthehighestecologicalfootprintforallconstructionsectors.Followedbythisareboththecroplandandforestrylandfootprints,respectively.Ontheotherhand,totalfisheryandgrazinglandfootprintsarefoundtobeminimalwhencomparedwithotherecologicalfootprintcategories.Figure6balsopresentsthetotalecologicalfootprintsofU.S.constructionsectorsbasedontheirtotaleconomicout-puts.TheresultsindicatethatR-PSMFSandNR-OTRarefoundtohavethelargestecologicalfootprints,respectively.Onthecontrary,NR-MSandR-MRhavethelowestcumu-lativeecologicalfootprintcomparedwithothersectors.Althoughthelatterhasthehighesttotalecologicalfootprintmultiplier,itshowsthelowestcumulativeecologicalfoot-printduetoalowtotaleconomicoutput.Ingeneral,totalforestlandfootprintsarefoundtobehigherforresidentialconstructionsectors.Thisresultcanberelatedtothehigheruseofwoodproductssuchastimberinbuildingconstruc-tionasopposedtoheavyconstruction.Amongtheecolog-icalfootprintcategories,CO2uptakelandsrepresentthehighestlandconsumptionvaluesforallresidentialandnon-residentialconstructionsectors.Therefore,specialem-phasisshouldbeplacedonreducingthetotalGHGemis-sionsbyconsideringtheScope3carbonfootprintswhichhavethelargestshare.
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Fig.6Ecologicalfootprintresults;aecologicalfootprintmultiplier(globalhectares),btotalecologicalfootprint(globalhectares)
IntJLifeCycleAssess(2013)18:958–972
a)
R-MR
NR-MRR-OTRR-PSMFS
NR-OTRNR-MSNR-CHCS
0
30
6090120150Ecological Footprint Multiplier (gha)
180
210
b)
R-MRNR-MR
R-OTRR-PSMFSNR-OTRNR-MSNR-CHCS
0.0E+00
1.2E+07
2.4E+07
3.6E+07
4.8E+07
6.0E+07
Total Ecological Footprint (gha)
Fishery (gha)
Grazing (gha)
Forestry (gha)
Cropland (gha)
Carbon Fossil Fuel (gha)Carbon Electricity (gha)
5Conclusions
Thispaperanalyzedthetriplebottom-linesustainabilityimplicationsofconstructionindustrybyproposingadistinc-tionbetweensevendifferentU.S.constructionsectors.TheresultsofsuchaholisticEIOanalysisprovidevaluableinsightsintothelocationofsustainabilityimpactsandcanproposeavitalguidancefordecisionmakerstodevelopsoundpoliciesforsustainableconstruction.Especially,LEEDwhichisawell-knownandwidelyusedbuildingratingsystemintheU.Scanbenefitfromsuchananalysisinordertodevelopeffectivegreenbuildingratingstrategiesconsideringtheconstructionsupplychain.
Theresultsindicatethatupstreamsuppliersofconstruc-tionsectorshavethelargestimpactscomparedwithon-siteactivities.Hence,usingnarrowlydefinedestimationmodelsbyneglectingsupply-chain-relatedimpactscanresultinlargeunderestimatesoftriplebottom-linesustainabilityimpactsoftheU.S.constructionindustry.ThefindingsofourresearchalsoshowthatNR-OTRandR-PSMFSarefoundtohavethelargesttotalsustainabilityimpactsforallsustainabilityimpactcategories.Scope3carbonemissionsareresponsibleforthehighestshareoftotalGHGemissionsforallconstructionsectors.Inaddition,itisseenthatap-proximately95%oftotalwateruseofconstructionsectorscanbeattributedtoindirectsuppliers,whicharelocatedinL2,L3,andhigherlayers.Intermsofwork-relatedinjuries,non-residentialconstructionsectorspresenthigherinjurymultiplierincomparisonwithresidentialconstructionsector,andon-siteconstructionworksaccountforover60%oftotalinjuries.
Incombinationwithrelevantenvironmentaldata,EIOanal-ysisisusefulforunderstandingthesupply-chain-relatedindi-rectenvironmentalimpactsofconstructionandcanminimizetheunderestimationofenvironmentalinterventionsduetonarrowlydefinedsystemboundaries.However,sustainabilityisnotonlylimitedtotheenvironment,andotherindicatorsofsustainability,suchaseconomicandsocial,shouldalsobetakenintoconsiderationforamoreholisticanalysis.LCAstudiesthatconsideralldimensionsofsustainabilityimpactsofcivilinfrastructuresareverylimited,andthecurrentresearchisafirstdetailedstudywhichintegrateseconomicandsocialindicatorswiththeEIOframeworkasanadditiontoenviron-mentalindicators.
Themethodologydescribedinthispaperhasbeenusedtoanswerthequestionrelatedtosustainableconstructionusingseveralkeysustainabilitymetrics.Datacollectionprocessforthesemetricsrequiredaconsiderabletimeandeffort,andmostwereobtainedfrompubliclyavailabledatasources.Infutureresearch,weproposetoextendourenvi-ronmentalfootprintmetricstoprovideamorerobustsus-tainabilityaccountingmodel.Asanexample,thebuilt-uplandfootprint,whichiscalculatedbasedontheareaoflandusedbyhumaninfrastructure,suchastransportation,hous-ing,industrialstructures,andreservoirsforhydroelectricpowergeneration,canbeallocatedtoeachconstructionsector.However,thelackofcomprehensivedatasetontotallandusesbyeachconstructionsectorisoneofthemain
IntJLifeCycleAssess(2013)18:958–972challengesthatshouldbeaddressedinfutureresearch.Furthermore,thispaperanalyzedtheenergy,water,andcar-bonfootprintsbasedontheuseofnaturalresources,includingcrudeoil,naturalgas,iron,copper,crushedstone,sandandgravel,clay,limestone,wood,etc.However,arelativecontri-butionoftheseresourcestoecologicalfootprintofeachcon-structionsectorisstillimportant,andthestudyconductedbyTatariandKucukvar(2012b)presentsafulldiscussionontheecologicalfootprintoftheseresourcesusingexergyanalysis.Althoughthefindingsofthisresearchcouldbeveryhelpfultodecisionmakerstoanalyzeandcomparethesustainabilityimplicationsofconstructionsectorsbyproposinganalterna-tivemethodology,ithasseveralimportantlimitationsthatshouldbetakenintoaccountforfuturestudies.First,theanalysisresultsarebasedontheU.S.nationalinput–outputaccounts,andtherefore,therearecertainuncertaintiesindataduetoregionalvariations.Forexample,Scope2carbonfoot-printscanvaryfromstatetostateorregiontoregiondepend-inguponelectricitygenerationfrommixes,includingcoal,naturalgas,oil,nuclear,hydropower,solar,andothersources.Hence,thesetypesofgeographicvariationsinemissionsshouldbeconsideredforfuturecarbonfootprintestimationsusingtheU.S.regionalinput–outputanalysisframework.Itisalsoimportanttonotethattheenvironmentalinterven-tionsrelatedtoconstructionphaseanddifferentend-of-lifescenariosarenotwellaccountedinpureEIOanalysis,andhybridLCAmodelwhichcombinestheP-LCAandEIO-LCAcanprovidemorespecificanddetailedlifecyclesustainabilityanalysisofconstructionwork,particularlyforconstruction,demolition,andwastedisposal.Moreover,thiscurrentstudymainlyusedtheEIOmethodology,whichisbaseduponnationalinput–outputdatathatgeneratesaggregationprob-lems.Althougheconomy-widecomprehensiveEIOmodelisdeveloped,therearestillimportantuncertaintiesembeddedinourresultsduetotheuseofaggregatedataforconstructionsectors.Forinstance,heavycivilinfrastructures,includinghighway,bridge,dams,watertreatmentfacilities,sewersys-tems,petroleum,gasandpowerplants,andcommunicationlinesareanalyzedtheundertheconstructionsectorofNR-OTR.Formoredetailedlifecyclesustainabilityassessmentmodel,theseconstructionsectorscouldbedisaggregatedandanalyzedunderNR-OTRasseparatesub-sectors.
Lastbutnotleast,thesustainabilityimpactsofimportedmaterialsusedbyU.S.sectorsareassumedtobeproducedwithdomestictechnologyeventhoughtheyareimportedfromothercountries.Tohaveatrade-linkedEIOmodel,multi-regionalinput–outputmodelscanbedevelopedinordertoaccountfortheimpactsofinternationaltradeinawaythatsustainabilityanalysisresultswillaccountforthetechnologicaldifferencesrelatedtoproductionofimportedmaterials.Animportanceofapplyingmulti-regioninput–outputframeworksininput–out-putanalysiscanbefoundintheliterature(Lenzenetal.2004;HertwichandPeters2009).
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References
BEA(2002)Benchmarkinput–outputdata.U.S.BureauofEconomic
Analysis.http://www.bea.gov/industry/io_benchmark.htm.AccessedJanuary5,2012
BEA(2010)Grossdomesticproductbyindustryaccounts.U.S.Bureauof
EconomicAnalysis.http://www.bea.gov/iTable/index_industry.cfm.AccessedJanuary5,2012
BilecM,RiesR,MatthewsHS,SharrardAL(2006)Exampleofa
hybridlife-cycleassessmentofconstructionprocesses.JInfrastSyst12:207–215
BlackhurstBM,HendricksonCT,VidalJSI(2010)Directandindirect
waterwithdrawalsforU.S.industrialsectors.EnvironSciTechnol44:2126–2130
BLS(2002)Industryinjuryandillnessdata.U.S.BureauofLaborStatistics.
http://www.bls.gov/iif/oshsum.htm.Accessed15March2012
CMU(2002)EIO-LCA(economicinput–outputlifecycleassessment).
http://www.eiolca.net/cgi-bin/dft/display.pl.Accessed5January2012EIA(2010)Historicaldataseries-totalenergy-relatedcarbondioxide
byend-usesectorandtheelectricpowersectorbyfueltype.U.S.EnergyInformationAdministration.http://www.eia.doe.gov/oiaf/1605/ggrpt/excel/historical_co2.xls.Accessed5January2012Eurostat(2008)Eurostatmanualofsupply,useandinput–output
tables.EuropeanCommission,Luxembourg
FinnvedenG,HauschildMZ,EkvallT,GuinéeJ,HeijungsR,Hellweg
S,KoehlerA(2009)Recentdevelopmentsinlifecycleassess-ment.JEnvironManage91:1–21
ForanB,LenzenM,DeyC(2005)Atriplebottomlineanalysisofthe
Australianeconomy.InCsiro(ed)BalancingAct.1:1–111
ForsbergA,MalmborgF(2004)Toolsforenvironmentalassessment
ofthebuiltenvironment.BuildEnviron39:223–228
GFN(2010a)Nationalfootprintaccounts:ecologicalfootprintandbio-capacity.GlobalFootprintNetwork.http://www.footprintnetwork.org/en/index.php/GFN/page/footprint_for_nations/.AccessedFebruary152012
GFN(2010b)Calculationmethodologyforthenationalfootprintaccounts.
GlobalFootprintNetwork.http://www.footprintnetwork.org/images/uploads/National_Footprint_Accounts_Method_Paper_2010.pdf.Accessed15February2012
GradelT,AllenbyB(2009)Industrialecologyandsustainableengi-neering,3rdedn.PrenticeHall,UpperSaddleRiver,NJ
GuinéeJB,HeijungsR,HuppesG,ZamagniA,MasoniP,Buonamici
R,EkvallT,RydbergT(2011)Lifecycleassessment:past,presentandfuture.EnvironSciTechnol45:90–96
HaapioA,ViitaniemiP(2008)Acriticalreviewofbuildingenviron-mentalassessmenttools.EnvImpAssesRev28:469–482
HendricksonCT,HorvathA(2000)Resourceuseandenvironmentalemis-sionsofUSconstructionsectors.JConstrEngManage126:38–44HendricksonCT,LaveLB,MatthewsS(2005)Environmentallife
cycleassessmentofgoodsandservices:aninput–outputap-proach,1stedn.RFFPress,Washington,DC
HertwichEG,PetersGP(2009)Carbonfootprintofnations:aglobal
trade-linkedanalysis.EnvironSciTechnol43:6414–6420
HorvathA(2004)Constructionmaterialsandtheenvironment.Annu
RevEnvironResour29:181–2004
HuangYA,LenzenM,WeberC,MurrayJ,MatthewsHS(2009a)The
roleofinput–outputanalysisforthescreeningofcorporatecarbonfootprints.EconSystRes21:217–242
HuangYA,WeberC,MatthewsHS(2009b)Categorizationofscope3
emissionsforstreamlinedenterprisecarbonfootprinting.EnvironSciTechnol43:8509–8515
HuppesG,KoningA,SuhS,HeijungsR,VanOersL,GuineeJB
(2008)EnvironmentalimpactsofconsumptionintheEuropeanUnion:high-resolutioninput–outputtableswithdetailedenviron-mentalextensions.JIndEcol10:129–146
972
JoshiS(2000)Productenvironmentallifecycleassessmentusing
input–outputtechniques.JIndEcol3:95–120
JunnilaS,HorvathA(2003)Life-cycleenvironmentaleffectsofan
officebuilding.JInfrastSyst9:157–166
KlöpfferW(2008)Lifecyclesustainabilityassessmentofproducts.Int
JLifeCycleAssess13:89–95
LenzenM,MurrayS(2001)Amodifiedecologicalfootprintmethod
anditsapplicationtoAustralia.EcolEcon37:229–255
LenzenM,DeyCJ(2002)Economic,energyandemissionsimpactsof
someconsumerchoices,technologiesandgovernmentoutlays.EnergEcon24:377–403
LenzenM,MurraySA,KorteB,DeyCJ(2003)Environmentalimpact
assessmentincludingindirecteffects:acasestudyusinginput–outputanalysis.EnvironImpAssessRev23:263–282
LenzenM,PadeL,MunksgaardJ(2004)CO2multipliersinsingle-region
andmulti-regioninput–outputmodels.EconSystRes16:391–412LeontiefW(1936)Quantitativeinputandoutputrelationsinthe
economicsystemoftheUnitedStates.RevEconStat18:105–125LeontiefW(1970)Environmentalrepercussionsandtheeconomic
structure:aninput–outputapproach.RevEconStat52:262–277LippiatB(2007)BEES4.0:Buildingforenvironmentaland
economicsustainabilitytechnicalmanualanduserguide.NationalInstituteofStandardsandTechnology,Gaithersburg,MD,USA
MatthewsHS,HendricksonCT,WeberCL(2008)Theimportanceof
carbonfootprintestimationboundaries.EnvironSciTechnol42:5839–5842
McDonaldGW,PattersonMG(2004)Ecologicalfootprintsandinter-dependenciesofNewZealandregions.EcolEcon50:49–67MillerR,BlairP(2009)Input–outputanalysis:foundationsandexten-sions,2ndedn.CambridgeUniversityPlace,UK
NRC(2009)Sustainablecriticalinfrastructuresystems:aframework
formeeting21stcenturyimperatives.Towardsustainablecriticalinfrastructuresystems:framingthechallengesworkshopcommit-tee.NationalResearchCouncil,Washington,DC
NRL(2012)U.S.life-cycleinventorydatabase.NationalRenewable
EnergyLaboratory.https://www.lcacommons.gov/nrel/search.Accessed5September2012
OchoaL,HendricksonCT,MatthewsHS(2002)Economicinput–output
life-cycleassessmentofU.S.residentialbuildings.JInfrastSyst8:132–138
RebitzerG,EkvallT,FrischknechtR,HunkelerD,NorrisG,Rydberg
T,SchmidtWP(2004)Lifecycleassessmentpart1:framework,goalandscopedefinition,inventoryanalysis,andapplications.EnvironInt30(5):701–720
SeoS,HwangY(2001)EstimationofCO2emissionsinlifecycleof
residentialbuildings.JConstrEngManage127(5):414–418
SharrardAL,MatthewsHS,RiesRJ(2005)Estimatingconstruction
projectenvironmentaleffectsusinganinput–output-basedhybridlife-cycleassessmentmodel.JInfrastSyst14:327–336
SuhS,LenzenM,TreloarGJ,HondoH,HorvathA,HuppesGetal
(2004)Systemboundaryselectioninlife-cycleinventoriesusinghybridapproaches.EnvironSciTechnol38(3):657–664
IntJLifeCycleAssess(2013)18:958–972
SuhS,LippiatBC(2012)Frameworkforhybridlifecycleinventory
databases—acasestudyontheBuildingforEnvironmentalandEconomicSustainability(BEES)database.IntJLifeCycleAssess17:604–612
TatariO,KucukvarM(2012a)Eco-efficiencyofconstructionmaterials:a
dataenvelopmentanalysis.JConstrEngManage138(6):733–741TatariO,KucukvarM(2012b)SustainabilityassessmentofU.S.
constructionindustry:anecosystemsperspective.JConstrEngManage138(8):918–922
TatariO,NazzalM,KucukvarM(2012)Comparativesustainability
assessmentofwarm-mixasphalts:athermodynamicbasedhybridlifecycleanalysis.ResConserRecy58:18–24
UN(1999)Studiesinmethods:handbookofnationalaccounting.United
NationsDepartmentforEconomicandSocialAffairs,StatisticsDivision,NewYork,USA
UNEP(2012)21Issuesforthe21stcentury:resultoftheUNEP
foresightprocessonemergingenvironmentalissues.UnitedNationsEnvironmentProgramme,Nairobi,Kenya
U.S.EPA(2010)Buildingsandtheenvironment:astatisticalsum-mary.USEnvironmentalProtectionAgency,Washington,DC,USA
USGBC(2009)LEED2009fornewconstructionandmajorrenova-tionsratingsystem.UnitedStatesGreenBuildingCouncil,WashingtonDC,USA
WachsmannU,WoodR,LenzenM,SchaefferR(2009)Structural
decompositionofenergyuseinBrazilfrom1970to1996.AppEnerg86:578–587
WackernagelM(2009)Methodologicaladvancementsinfootprint
analysis.EcolEcon68:1925–1927
WaehrerGM,DongXS,MillerT,HaileE,MenY(2007)Costsof
occupationalinjuriesinconstructionintheUnitedStates.AccidAnalyPrev39:1258–1266
WeberCL,MatthewsHS(2007)EmbodiedemissionsinU.S.interna-tionaltrade:1997–2004.EnvironSciTechnol41:4875–4881WiedmannT,LenzenM(2008)Unravelingtheimpactsofsupply
chains:anewtriple-bottom-lineaccountingapproachandsoft-waretool.EnvManAccCleanProd24:65–90
WiedmannT,LenzenM,BarrettJ(2009)Companiesonthescale:
comparingandbenchmarkingthesustainabilityperformanceofbusinesses.JIndEcol13:361–383
WiedmannT,SuhS,FengK,LenzenM,AcquayeA,ScottK,Barrett
JR(2011)Applicationofhybridlifecycleapproachestoemergingenergytechnologies—thecaseofwindpowerintheUK.EnvironSciTechnol45:5900–5907
WilliamsE(2004)Energyintensityofcomputermanufacturing:hybrid
assessmentcombiningprocessandeconomicinput–outputmeth-ods.EnvironSciTechnol38:6166–6174
WoodR,DeyCJ(2009)Australia’scarbonfootprint.EconSyst
Res21:243–266
WRIandWBCSD(2004)Greenhousegasprotocol:acorporateac-countingandreportingstandard.Washington,DC,USA
ZamagniA(2012)Lifecyclesustainabilityassessment.IntJLife
CycleAssess17:373–376
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