1.SchoolofBusiness,CentralSouthUniversity,Changsha410083,China;2.SchoolofMathematicsandStatistics,CentralSouthUniversity,Changsha410083,China;3.InstituteofMetalResourcesStrategy,CentralSouthUniversity,Changsha410083,ChinaReceived10September2018;accepted21May2019Abstract:Assessingandaccountingformaterialconsumptionandenvironmentalimpactarenecessarytomeasureenvironmentalexternalitiesofthealuminumindustryandtoconstructanecologicalcivilization.Inthisresearch,lifecycleassessment(LCA)theorywasusedtoassesstheenvironmentalimpactofprimaryaluminumbasedonthelimesodaBayerprocessanddifferentpowergenerationmodes,andthesourcesanddistributionsofthefourselectedimpactcategorieswereanalyzed.Theresultsshowthat,(1)Negativeenvironmentalimpactofaluminumindustrygenerallyoccursfromaluminaextraction,carbonanodefabricationandelectrolysis,particularlyelectrolysisandaluminaextraction.Primaryenergydemand(PED),wateruse(WU),globalwarmingpotential(GWP)andfreshwatereutrophicationpotential(FEP)aremainenvironmentalimpactcategories.(2)Theenvironmentalloadwiththermalpowerishigherthanthatwithhydropower,e.g.,fortheformer,thegreenhousegasemissioncoefficientof21800kgCO2eq/t(Al)willbegenerated,whileforthelatter,4910kgCO2eq/t(Al)willbegenerated.(3)Bothpowermodemethodsreflecttheenergystructure,whereasdirectemissionsreflectthetechnicallevel,indicatingthepotentialforlargeenergysavingsandemissionreductions,andsomepolicies,relatedtocleanpower,energyefficiencyandtechnologicalprogress,shouldbemadeforemissionreduction.Keywords:primaryaluminum;environmentalimpact;lifecycleassessment;emissionreductionpotential1Introduction
Sincethebeginningofthiscentury,China’saluminumindustryhaswitnesseda10-yearperiodofrapidgrowthduetourbanizationandindustrialization.Theprimaryaluminumoutputincreasedrapidlyfrom5.55×106tin2003to22.06×106tin2013,withanaverageannualgrowthrateofapproximately15.2%,whichisfarhigherthantheglobalaverageforthissector.In2017,Chinareportedanoutputof53.78×106tof10kindsofnonferrousmetals,anincreaseof3%,andChinahasbeenthetopglobalproducerofnonferrousmetalsforconsecutive16years.Accordingtothisreport,thealuminumoutputwas32.27×106t,accountingfor60%ofthetotalamountofthesekindsof10nonferrousmetals.Therefore,Chinaisthemostimportantglobaleconomyregardlessoftheabsolutedemandforaluminummetalorconsumptionincrease.However,theprocessesutilizedbythealuminumindustry,e.g.,bauxitemining,aluminaextraction,anodefabrication,electrolysisandingotcasting,requirehighenergyconsumptionandproducelargequantitiesofharmfulsubstancesandhighemissions.Inrecentyears,Chinahascontinuedtoimproveitsaluminumindustrytechnologies,althoughthenegativeenvironmentalimpactofthealuminumindustryremainsdifficulttoeliminate,resultinginanationalsituationwhenthermalpowerisusedasthemainenergysource.Inthecurrentcontextofconstructinganecologicalcivilization,continuousprogresshasbeenmadeinanalyzingresourcesandtheenvironment.However,animportantandurgentproblemthatneedstobesolvedishowtoaccountformaterialconsumptionandtheenvironmentalimpactandtoassesstheenvironmentalandeconomicimpactofthedevelopmentandutilizationofnonferrousmetalresources.Accordingtoexistingstudies,theenvironmentalimpactofthealuminumindustryprocessflowhasbeenassessedtosomeextent.Forexample,theEuropeanAluminumAssociationFoundationitem:Projects(71633006,71403298)supportedbytheNationalNaturalScienceFoundationofChina;Projects(14YJCZH045,15YJCZH019)supportedbytheMinistryofEducationofHumanitiesandSocialScience,ChinaCorrespondingauthor:Yao-qiGUO;Tel:+86-13787798224;E-mail:guoyaoqi@csu.edu.cnDOI:10.1016/S1003-6326(19)65086-7YiYANG,etal/Trans.NonferrousMet.Soc.China29(2019)1784−17921785(EAA)collectedlifecycleindexdataonaluminumproductionandmanufacturingenterprisesinmajorEuropeancountriesin1992andreleasedthefirstecologicalprofilereportin1996[1].TheInternationalAluminumInstituteissuedthelifecycleinventoryoftheworldwidealuminumindustrywithregardtoenergyconsumptionandemissionofgreenhousegases(section1:automobilesin2000)[2],thelifecycleassessment(LCA)ofaluminum:inventorydatafortheworldwideprimaryaluminumindustryin2003andanupdatedversionofthereportin2007[3].Moreover,theEAApublishedtheenvironmentalprofilereportfortheEuropeanaluminiumindustryin2008[4].Theseresearchreportswerebasedonquestionnairesurveydatafromthealuminumindustryin27EUcountries,NorthAmericancountriesandmemberstatesofothereconomiccooperationorganizations.Inacademicresearch,LCAofaluminumanditsapplicationcanbefoundthroughouttheinternationalliterature.TANandKHOO[5]usedtheLCAmethodtoconductaquantitativeanalysisontheenvironmentalimpactofdifferentprocessesinAustralia.ZAREandIZADIKHAH[6]comparedthepotentialenvironmentalimpactofthreecategoriesofaluminuminIran:primaryaluminumingot,secondaryaluminumingotandmixedaluminumingot.However,mostresearcheshavebeenlimitedtoaspecificprocess,suchasbauxitemining[7],casting[8]andrecycling[9−11].Somestudiesdiscussedthefeasibilityofusingaluminummaterialforapplicationsorasasubstituteforothermaterials,e.g.,vehicles[12]andpackaging[13,14].LCAontheenvironmentalimpactofChina’saluminumindustryhasgenerallyfocusedonspecificprocessesandrecycling[15],alloysandtransportationapplications[16,17],resourcemanagement[18,19],andgreenhousegas(GHG)emissions[20,21].LIUandMÜLLER[22]summarizedsomenotablefeaturesandtrendsinaluminumLCAstudies,includingthelimitedscopeanddifferentiatedsystemboundaries,thecommonpracticeofusingindustry-widegenericinventorydata,challengesofallocationforaluminumrecycling,andthepredominantfocusonenergyandGHGemissionsasenvironmentalmetrics.Inparticular,ZHANGetal[23]evaluatedtheenvironmentalimpactofaluminumproductioninChina,includingprimaryaluminumandsecondaryaluminum,viaLCA.Thisstudyisquitecomprehensiveandrepresentative,althoughthealuminaextractionandpowerstructurewerenotclearlydescribed.China’saluminumindustryisakeysectorfacingincreasingpressuretoreduceemissions.Thus,China-focusedLCAisandwillbealwaysimportantandrequiredforreducingenergyusageandimplementingeffectivepolicies.Thisresearch,combiningfieldsurveysfromspecificenterprisesbasedontheliteratureandotherinformation,attemptedtocomprehensivelyevaluateprocessflowsandmaterialinput/outputfortheLCAofChina’saluminumindustry.Moreover,owingtothepriorusageofLCAthatfocusedonglobalaverageconditionsinChina,China’sLifeCycleDatabase(CLCD)wasusedtofurtherstudytheenvironmentalimpactofthermalpowerandhydropowerintotheLCAofthealuminumindustry.Thisevaluationwillallowamorecompleteandupdatedlifecycleimpactassessment(LCIA)ofChina’saluminumindustry.2Assessmentobjectivedefinition
Inaccordancewiththeresearchobjectivesandscoperequirementsandtoguaranteetheintegrityofimportantprocessesanddata,effectiveclassificationanddivisionofsystemboundariesarebeneficialtothesubsequentinventoryanalysisandassessmentinterpretation.Theselectedrulesareasfollows.(1)Inputsfromfixedassets,suchasmachinerooms,factorybuildingsandpersonnel-relatedconsumption,arenotincluded.(2)Whentheweightofthecommonmaterialis<1%ortheweightofthematerialcontainingrareorhigh-puritycomponentsis<0.1%oftheproductweight,theupstreamproductiondataareignored,althoughthetotalweightofthematerialignoredisnomorethan5%.(3)Themainpollutants(seetherelevantindustrialstandard)andpollutantswithacontributionof>1%shouldbeincluded,althoughitisnotnecessarytorejectthosewithacontributionof<1%.Usingtheabovecriteriaasabasis,thisworkdidnotconsidertheenvironmentalimpactcausedbytransportationduetodifferencesinregionaldistancesandconditions.Instead,thisworkcoveredtheprocessflows,suchasbauxitemining,aluminaextraction,carbonanodefabrication,electrolysisandingotcasting(fromcradletogate)becauseoftheirabsoluteresourceandenergyconsumptionandpollutiondomination.AluminaextractionwasanalyzedbasedonthelimesodaBayerprocess,andprebakedcarbonanodefabricationprovidedauxiliaryrawmaterialsforelectrolysis;theinputconsistedofrawmaterialandenergyinputs,andtheoutputmainlyincludedgaseouseffluents,liquidwaste,solidwaste,byproductsandproducts.Wastepollutantsweredischargedbothdirectlyandindirectly;theemissionsofthematerialflowinventoryshowninFig.1werealldirectemissions,whileindirectemissionswerereferredtointheCLCDandtheonlineLCAanddatabasedevelopmenttooleFootprintofIKEEnvironmentalTechnologyCo.,Ltd.1786YiYANG,etal/Trans.NonferrousMet.Soc.China29(2019)1784−1792Fig.1Materialandenergyinputintensityofsystemboundaries(PM:Particulatematter)3Materialflowinventoryofprimaryaluminum
Afieldsurveyofactualproductionsituationsinaluminumenterprisesfoundthatthemainfuelsinvolvedinthealuminumsmeltingprocessarefueloil,coal,naturalgas,keroseneandcoke.Figure1showstheinputandemissionintensitytoobtain1tofthenextmainproduct.UsingfuelconsumptionandcorrespondinggaseouspollutantemissioncoefficientsobtainedorcalculatedbytherelevantparametersfromIPCC(IntergovernmentalPanelonClimateChange),thedirectemissionsofgaseouspollutantsfromfueluseinarelevantprocessflowcanbecalculated.ThegaseouseffluentsfromfuelcombustionmainlyincludeCO2,CO,SO2,NOxandCH4.ProductiondataforprimaryaluminumwereobtainedfromtheChinaNonferrousMetalsIndustryYearbook.Inputsforbauxitemining,aluminaextraction,carbonanodefabrication,electrolysisandingotcastingwerecollectedin2017,andthoseforothermaterialsandenergy,suchasfueloil,electricity,sodaash,carbideslag,flocculant,coal,steam,naturalgas,water,metallurgicalcoke,asphalt,petroleumcoke,aluminumfluoride,cryolite,graphitepowder,ACpower,scorchedparticle,andkerosene,wereobtainedfromtheCLCD-China-ECER0.8,representingtheindustryaveragein2013.Directemissionsoffluoride,SO2,solidwasteandliquidwastewereobtainedfrommonitoringreports.Bauxiteisthemainrawmaterialofprimaryaluminum,andChinaobtainsbauxitemainlythroughstripminingandimportsfromothercountries.Afterignoringbauxitequalitydifferencesandenvironmentalimpacttransferfactorsandcarryingoutasurveyofaluminumenterprises,thebauxiteminingmaterialflowinventoryissorted.Gaseouseffluentsareexpressedbydirectemissiondatafortheprocess,i.e.,mainlyfromfueloilcombustion,andcanbedeterminedbycalculatingtheemissioncoefficientslistedinTable1andotherparameters,suchasthefueloilheatvalue.YiYANG,etal/Trans.NonferrousMet.Soc.China29(2019)1784−17921787Table1GaseousemissioncoefficientsofdifferentfuelsGasFueloilCoalNaturalgasKeroseneCokeCO22.38kg/kg2.77kg/kg2.09kg/m32.56kg/L3.14kg/kgCO4.81mg/kg0.43kg/kg1.12g/m3−0.60kg/kgSO23.00g/kg1.74g/kg10.00g/m3−1.98g/kgNOx5.84g/kg7.5g/kg1.50g/m35.97g/L9.00g/kgCH49.28g/kg0.28g/kg0.19g/m310.7g/L29.30mg/kgThesinteringprocess,thelimesodaBayerprocessandthesinter-Bayercombinationprocessareavailableforaluminaproduction.ChinahasestablishedaproductionprocesshighlightingthelimesodaBayerprocesswiththedevelopmentofaluminatechniques.Therefore,inthiswork,ananalysisisconductedbasedonthelimesodaBayerprocess.Bothaself-bakedanode(anodepaste)andaprebakedanodecanbeusedascarbonanodesinanaluminumelectrolytictankbasedoncertaindifferencesintheusedmodes.Prebakedanodesfeaturelowvoltage,lowpollution,convenientmechanicaloperation,advancedprocessesandsuitabilityforhigh-capacityelectrolytictanks;thus,mostaluminumenterprisescurrentlyhaveusedprebakedanodes.Aprebakedanodeismadefrompetroleumcoke,asphaltandmetallurgicalcokerawmaterials,andnaturalgasisusedasthemainfuel.Theproductionprocessincludesthecalcining,roastingandcarbonanodefabrication,andresultsinthedischargeofsolidwaste,chemicaloxygendemand(COD)andgranuleparticulatesinadditiontogaseousemissionsofCO2,CO,SO2,NOxandCH4.Thedatafortherawmaterialinput,energyinputandenvironmentalemissiondataaretakenfromRef.[24].Thematerialinputsforelectrolysisincludecarbonanodes,cryolite,sodaash,calciumfluoride,electrolyteblocks,graphiteandscorchedparticles.Ofthesematerials,cryoliteisasolvent,andcalciumfluorideismainlyusedformendingelectrolytictanks.Electrolytesincludemagnesiumfluoride,aluminumfluorideandalumina.Scorchedparticleshaveasulfurcontentofnomorethan0.6%,andphosphoruspigironhasasulfurcontentofnomorethan0.2%.WhenconvertingACpowertoDCpowerwithaconverterandconnectingtheDCpowertoelectrolytictanksforelectrolysis,thecathodeproducesliquidaluminum,andtheanodegeneratesgas.GaseouspollutantsfromtheelectrolysisprocessincludeCO2,CO,SO2,NOxandCH4fromelectrolysisandfuelcombustion,andotherGHGsandperfluoro-carbongases,mainlyCF4andC2F6,aregeneratedfrommoltensaltelectrolysiswithagenerationproportionofapproximately10:1.Thefluorinecontentintheemittedgasesiscalculatedtobe0.835kg/t(Al)[25].Intheelectrolysisprocess,theconsumptionofgraphitepowderandasbestoscordissolowthatwecanignoretheirenvironmentalloadincompliancewiththeselectedrules.Currently,thealuminumingotcastingprocessusesprimarilynaturalgasandelectricpowerforenergy.Areleasingagentandafluxmediumareusedforthedegassinganddeslaggingtreatments,respectively,andasbestosrope,steelbalingbandsandpackage/bagclampsareusedforpackaging.Exceptforprimaryaluminumliquid,thelimitedmaterialsthatareconsumedcanbeignored.Thepurealuminumlossis0.4%−0.5%inthecastingprocess,andthisworkuses0.5%asastandard.4Environmentalandanalysis
impactassessmentresults4.1SelectionofenvironmentalimpactcategoriesThisworkconsiderstheproductenvironmentalfootprint(PEF)forgreenproductassessment.ThePEFmethodology,releasedbasedonLCAtheorybytheEuropeanCommissionin2013andwidelyappliedinEUcountries,analyzes13categoriesofenvironmentalimpact,namely,theglobalwarmingpotential(GWP),primaryenergydemand(PED),abioticdepletionpotential(ADP),wateruse(WU),acidificationpotential(AP),freshwatereutrophicationpotential(FEP),respiratoryinorganics(RI),ozonedepletionpotential(ODP),photochemicalozoneformationpotential(POFP),humantoxicity-cancereffects(HT-cancer),humantoxicity-noncancer(HT-noncancer),ecotoxicity(ET),andionizingradiationpotential-humanhealtheffects(IRP).4.2CharacterizationCharacterizationistheassessmentofthemagnitudeofthepotentialimpactofeachinventoryflowbasedonthecorrespondingenvironmentalimpact(e.g.,modelingthepotentialimpactofcarbondioxideandmethaneonglobalwarming).CharacterizationfactorsarecommonlyreferredtoasequivalencyfactorsandprovideawaytodirectlycomparetheLCIresultswithineachcategory[26].TwoLCAmodelsofprimaryaluminumbasedonthelimesodaBayerprocessareestablishedaccordingtodifferentelectricpowergenerationmodesusedforenergyinputs,namely,LCA-Al-TP(withthermalpower)andLCA-Al-HP(withhydropower),forcomparisonandanalysis.(1)CharacterizationofLCA-Al-TPThecharacterizationresultsandcontributiontotheenvironmentalimpactcategoriesofLCA-Al-TPareshowninTable2andFig.2,respectively.The1788ImpactfactorGWP/kgCO2eqPED/MJADP/kgSbeqWU/tAP/kgSO2eqFEP/kgPeqRI/kgPM2.5eqODP/mgCFC-11eqPOFP/kgNMVOCeqHT-cancer/10−6CTUhHT-noncancer/10−6CTUhET/CTUeIRP/kgU235eqYiYANG,etal/Trans.NonferrousMet.Soc.China29(2019)1784−1792IngotcastingElectrolysis4.75×1025.86×1032.61×10−4
1.492.494.41×1020.7270.5610.1822.08×10−22.82×10−20.4350.1021.73×1041.99×1050.19157.386.81.62×104
2519.56.330.7881.1315.95.03Aluminaextraction3.51×1034.38×1042.49×10−3
20.223.23.25×1038.883.651.110.1830.2852.898Anodefabrication4.39×1021.36×1042.48×10−3
8.632.773.5×1021.1750.70.711.031.68243.64Bauxitemining1.15×1021.24×1031.02×10−40.2970.5071.07×1020.1421.474.43×10−23.11×10−24.97×10−20.6430.105Total2.18×1042.63×1050.19687.91162.03×10435.975.98.372.053.1743.816.9Table2CharacterizationresultsofLCA-Al-TPFig.2ContributionstoenvironmentalimpactcategoriesofLCA-Al-TPelectrolysisprocesshasthehighestcontributiontoADP,FEP,GWP,POFPandPED,withcorrespondingtotalvaluesof0.196kgSbeq,2.03×104kgPeq,2.18×104kgCO2eq,8.37kgNMVOCeq,and2.63×105MJ,respectively,andthecontributionpercentagereaches97.4%forADP.IntermsofFEP,GWP,POFPandPED,thecontributionpercentagesarecloseto80%.AluminaextractionhasthehighestcontributiontoIRP,accountingfor47.3%.CarbonanodefabricationhasthehighestcontributiontoODP,HT-cancer,HT-noncancerandET,andthecontributionpercentagesare66.8%,50.2%,53.0%and54.8%,respectively.Thecontributionpercentagesofthealuminumingotcastingandbauxiteminingprocessestovariousenvironmentalimpactsaregenerallynomorethan2.2%.(2)CharacterizationofLCA-Al-HPTable3andFig.3showthecharacterizationresultsandcontributionstotheenvironmentalimpactcategoriesofLCA-Al-HP,respectively,whichindicatethattheelectrolysisprocesshasthehighestcontributiontoADP,PEDandHT-noncancer,withtotalvaluesof0.187kgSbeq,1.06×105MJand1.61×10−6CTUhandaccountingfor97.3%,50.3%and50.1%,respectively.ThealuminaextractionprocesshasthehighestcontributiontoGWP,WU,AP,FEP,RI,POFPandIRP,andthecorrespondingcontributionpercentagesreach58.7%,53.4%,76.4%,60.0%,82.1%,44.8%and57.1%,respectively.CarbonanodefabricationhasthehighestcontributiontoODP,HT-cancerandET,accountingfor88.9%,64.1%and76.6%,respectively.Thealuminumingotcastingprocessandbauxitemininghavemuchlowercontributionpercentagesofnomorethan2.4%tovariousenvironmentalimpacts.AllofthetotalimpactvaluesinTable3aregenerallysmallerthanthoseinTable2exceptforHT-noncancer,whichiscausedbydifferentpowergenerationmodes,suggestingtheenvironmentalfriendlinessofhydropowerandtheverylargeenergysavingandemissionreductionpotentialofChina’saluminumindustry.TheaccumulatedcharacterizationresultsfordifferentenvironmentalimpactcategoriesfromtwoLCAmodesofprimaryaluminumsystemsareshowninthe“total”columnsofTables2and3.TheaccumulatedvaluesshowthattheenvironmentalloadofprimaryYiYANG,etal/Trans.NonferrousMet.Soc.China29(2019)1784−1792Table3CharacterizationresultsofLCA-Al-HPImpactfactorGWP/kgCO2eqPED/MJADP/kgSbeqWU/tAP/kgSO2eqFEP/kgPeqRI/kgPM2.5eqODP/mgCFC-11eqPOFP/kgNMVOCeqHT-cancer/10−6CTUhHT-noncancer/10−6CTUhET/CTUeIRP/kgU235eqIngotcastingElectrolysis7.481.51×1031.42×10−54.86×10−31.09×10−2
4.012.93×10−33.45×10−25.13×10−38.59×10−35.68×10−28.58×10−21.59×10−2
1.66×1035.33×1040.1827.623.751.53×1030.7191.870.3890.3782.094.192.15Aluminaextraction2.88×1033.8×1042.16×10−3
18.219.82.66×1037.902.940.8680.1670.3232.427.88Anodefabrication3.33×1021.26×1042.42×10−3
8.292.212.5×1021.0150.50.671.031.6823.93.62Bauxitemining284.33×1025.6×10−52.16×10−24.57×10−2
26.27.74×10−3
1.371.14×10−22.88×10−25.51×10−20.5788.94×10−2
1789Total4.91×1031.06×1050.18734.125.94.47×1039.6456.81.941.614.2031.213.8Fig.3ContributionstoenvironmentalimpactcategoriesofLCA-Al-HPaluminumforthermalpowerishigherthanthatforhydropower.Moreover,GWP,AP,FEPandRIexhibitlargedifferencesunderdifferentpowergenerationmodes.Forexample,forGHGs,whenaunitofprimaryaluminumisproducedunderthermalpower,21800kgCO2willbegenerated,whileonly4910kgCO2willbegeneratedwithhydropower.4.3SourcesanddistributionsofmainenvironmentalimpactcategoriesNormalizationisanoptionalstepwithinLCIAthatmaybeusedtoassistintheinterpretationoflifecycleinventorydataaswellasLCIAresults.NormalizationtransformsthemagnitudeoftheLCIandLCIAresultsintorelativecontributionsbysubstanceandlifecycleimpactcategory[27].However,normalizationinsoftwaresuchasGaBihasgraduallybeeneliminated.Thus,weselect4ofthe13environmentalimpactcategoriesbasedonthecharacterizationresultsandemissionspollutionaccuracy,wherethelatterincludesdirectsolid,liquid,andgaseousemissionsinprimaryaluminumproduction.MostenterprisesmayownmonitoringequipmentforCO2andsulfideorutilizesophisticatedstatisticaldata;however,theylackdataforindicatorsofODPandHT-(non)cancer.Specifically,PED,WU,GWPandFEParechosentoanalyzethekeysourcesanddistributionsoftheimpactcategoriesowingtotheirrelativelysmallrelativeerrors.Theemissionsourcesaredividedintodirectemissionsthatoccurinchemicalreactionsinownedorcontrolledprocessequipment,suchasaluminaextractionandelectrolysis,andindirectemissionsthatcomefromthematerialsandenergyusedintheproductionofprimaryaluminum,suchasemissionsatthefacilitywherepurchasedelectricityisgeneratedandemissionsfromtheextractionandproductionofpurchasedmaterials.(1)SourceanddistributionofmainimpactcategoriesinLCA-Al-TPAsshowninFig.4,thekeyfactorsinfluencingPEDareACpower,withaproportionof74%usedinACpowerforelectrolysis,andsteam,alkali,coaland1790YiYANG,etal/Trans.NonferrousMet.Soc.China29(2019)1784−1792electricityusedinaluminaextraction,approximately15%(Fig.4(a)).TheWUmostlycomesfromACpowerandaluminumfluorideintheelectrolysisprocess,accountingforasmuchas63%.Secondly,alkaliandsteaminaluminaextractionaccountfor12%and9%ofWU,respectively,andcarbonanodefabricationconsumes8%(Fig.4(b)).ACpowerusedinelectrolysisproduces72%oftheGWP,anddirectemissionsofelectrolysisandaluminaextractiongenerateabout10%(Fig.4(c)).FEPissimilartoGWP.Directemissionsofelectrolysisandaluminaextractionaccountforabout11%oftheFEP(Fig.4(d)).Overall,thesefourimpactcategoriesarestilldominatedbyindirectemissions,andemissionsfromthermalpoweraccountforasignificantproportion.(2)SourcesanddistributionofmainimpactcategoriesinLCA-Al-HPTheACpowerusedinelectrolysisisstillthemainsourceofPEDsinceitaccountsforlessthan47%.Steam,coalandalkaliinaluminaextractionproduce16%,8%and7%ofthePED,respectively(Fig.5(a)).ThekeyfactorsinfluencingtheWUarealkaliandsteaminthealuminaextractionprocess,accountingfor53%intotal.Electrolysisandcarbonanodefabricationalsomakesignificantcontributions(Fig.5(b)).GWPmainlyresultsfromindirectemissionsgeneratedbyACpowerforelectrolysis(26%)aswellassteam(25%)andalkali(11%)foraluminaextraction,anddirectemissionsfromaluminaextractionaccountfor20%(Fig.5(c)).Morethan59%oftheFEPisgeneratedduringthealuminaextractionprocess,nearlyhalfofFEPisrelatedtodirectemissions,accountingforupto49%whencombinedwiththatoftheelectrolysisprocess(Fig.5(d)).ThesefourenvironmentalimpactcategoriesselectedforChina’saluminumindustryaredominantinelectrolysisandaluminaextraction.Moreover,theenvironmentalimpactofbauxiteminingandingotcastingissmaller.Differentpowergenerationmodesresultinalargegapintheenvironmentalimpact,whichiscausedbytherequirementformoreresourcesandenergyconsumptionforthermalpower.However,thesituationinChinaisthatthermalpowerstillaccountsformorethan80%ofproduction.Theseresultsurgethetransitiontocleanpowergenerationmodes,includinghydropower,windpowerornuclearpower,atlargerscales.Additionally,directemissionsfromelectrolysisandaluminaextractionwithhydropowerstillhaveasubstantialenvironmentalimpact(e.g.,morethan20%oftheGWPandnearly47%oftheFEP),indicatingthatthereisroomfortechnologicalprogress.Bothmethodsofgeneratingelectricpower,whichreflecttheenergystructure,andtheproportionofdirectemissions,whichreflectthetechnicallevel,revealaverylargepotentialforenergysavingsandemissionreductionsinChina’saluminumindustry.Fig.4SourcedistributionofimpactcategoriesselectedinLCA-Al-TP:(a)PED;(b)WU;(c)GWP;(d)FEPYiYANG,etal/Trans.NonferrousMet.Soc.China29(2019)1784−17921791Fig.5SourcedistributionofimpactcategoriesselectedinLCA-Al-HP:(a)PED;(b)WU;(c)GWP;(d)FEP5Conclusions
(1)NegativeenvironmentalimpactofChina’saluminumindustryisgenerallyrelatedtoaluminaextraction,carbonanodefabricationandelectrolysis,particularlyelectrolysisandaluminaextraction.ThecharacterizationresultsshowthatthenormalizedvaluesofPED,WU,GWPandFEParehigherthanthoseoftheothercategories.(2)Theenvironmentalcontaminationofprimaryaluminumproductionusingthermalpowerisgreaterthanthatusinghydropower.AsignificantenvironmentalimpactdiscrepancyexistsinGWP,AP,FEPandRIunderdifferentpowergenerationmodes;pollutioncomesmainlyfromindirectemissions,anddirectemissionsfromhydropoweronlycontributealimitedproportion(e.g.,morethan20%oftheGWPandnearly47%oftheFEP)aswell.(3)Bothmethodsofgeneratingelectricpower,whichreflectstheenergystructure,andtheproportionofdirectemissions,whichreflectsthetechnicallevel,indicateaverylargepotentialforenergysavingsandemissionreductionsinChina’saluminumindustry.Theresultsencouragecorrespondingpoliciesandmeasures,suchasdevelopingcleanpowergeneration(suchashydropower,windpowerornuclearpower),improvingenergyefficiencyandpromotingtechnologicalprogress.References
[1]EuropeanAluminiumAssociation.EcologicalprofilereportfortheEuropeanaluminiumindustry[R].Brussels:EuropeanAluminiumAssociation,1996.IPAILifeCycleWorkingCommittee.Lifecycleinventoryoftheworldwidealuminumindustrywithregardtoenergyconsumptionandemissionsofgreenhousegases[R].London:InternationalAluminiumInstitute,2000.SAURK.Lifecycleassessmentofaluminum:inventorydatafortheworldwideprimaryaluminiumindustry[R].London:InternationalAluminiumInstitute,2003.EuropeanAluminiumAssociation.EnvironmentalprofilereportfortheEuropeanaluminiumindustry[R].Brussels:EuropeanAluminiumAssociation,2008.TANRBH,KHOOHH.AnLCAstudyofaprimaryaluminumsupplychain[J].JournalofCleanerProduction,2005,13(6):607−618.ZARER,IZADIKHAHM.Multi-criteriadecisionmakingmethodsforcomparingthreemodelsofaluminumingotproductionthroughlifecycleassessment[J].AppliedEcologyandEnvironmentalResearch,2017,15(3):1697−1715.NORGATET,HAQUEN.Energyandgreenhousegasimpactsofminingandmineralprocessingoperations[J].JournalofCleanerProduction,2010,18(3):266−274.KOLTUNP,THARUMARAJAHA,GRANDFIELDJF.Greenhouseemissionsinprimaryaluminiumsmeltercasthousesea[2][3][4][5][6][7][8]1792[9]YiYANG,etal/Trans.NonferrousMet.Soc.China29(2019)1784−1792lifecycleanalysis[J].MaterialsScienceForum,2010,630:27−34.OLIVIERIG,ROMANIA,NERIP.Environmentalandeconomicanalysisofaluminiumrecyclingthroughlifecycleassessment[J].InternationalJournalofSustainableDevelopment&WorldEcology,2006,13(4):269−276.DAMGAARDA,LARSENAW,CHRISTENSENTH.Recyclingofmetals:Accountingofgreenhousegasesandglobalwarmingcontributions[J].WasteManagement&Research,2009,27(8):773−780.PARASKEVASD,KELLENSK,DEWULFW,DUFLOUJR.Environmentalmodellingofaluminiumrecycling:Alifecycleassessmenttoolforsustainablemetalmanagement[J].JournalofCleanerProduction,2015,105:357−370.DASS.Lifecycleenergyandenvironmentalassessmentofaluminum-intensivevehicledesign[J].SAEInternationalJournalofMaterialsandManufacturing,2014,7(3):588−595.NIEROM,NEGRELLIAJ,HOFFMEYERSB,OLSENSI,BIRKVEDM.Closingtheloopforaluminumcans:lifecycleassessmentofprogressionincradle-to-cradlecertificationlevels[J].JournalofCleanerProduction,2016,126:352−362.STOTZPM,NIEROM,BEYN,PARASKEVASD.Environmentalscreeningofnoveltechnologiestoincreasematerialcircularity:Acasestudyonaluminiumcans[J].Resources,ConservationandRecycling,2017,127:96−106.HONGJian-ping,WANGJun,CHENHai-yan,SUNBao-de,LIJia-jing,CHENChong.ProcessofaluminumdrossrecyclingandlifecycleassessmentforAl−Sialloysandbrownfusedalumina[J].TransactionsofNonferrousMetalsSocietyofChina,2010,20(11):2155−2161.HONGJing-min,ZHOUJing,HONGJing-lan,XUXu.Environmentalandeconomiclifecycleassessmentofaluminum−siliconalloysproduction:AcasestudyinChina[J].JournalofCleanerProduction,2012,22(1):11−19.YIQiu-ping,TANGChang-ping.Environmentalimpactassessmentofmagnesiumalloyautomobilehubbasedonlifecycleassessment[J].JournalofCentralSouthUniversity,2018,25(8):1870−1878.[18]YUEQiang,WANGHe-ming,LUZhong-wu,ZHISheng-ke.AnalysisofanthropogenicaluminumcycleinChina[J].TransactionsofNonferrousMetalsSocietyofChina,2014,24(4):1134−1144.DINGNing,YANGJian-xin,LIUJing-ru.SubstanceflowanalysisofaluminumindustryinmainlandChina[J].JournalofCleanerProduction,2016,133:1167−1180.LIUZhe,GENGYong,ADAMSM,DONGLiang,SUNLi-na,ZHAOJing-jing,DONGHui-juan,WUJiao,TIANXu.UncoveringdrivingforcesongreenhousegasemissionsinChina’saluminumindustryfromtheperspectiveoflifecycleanalysis[J].AppliedEnergy,2016,166:253−263.GAOFeng,NIEZuo-ren,WANGZhi-hong,LIHong-mei,GONGXian-zheng,ZUOTie-yong.GreenhousegasemissionsandreductionpotentialofprimaryaluminumproductioninChina[J].ScienceinChinaSeriesE:TechnologicalSciences,2009,52(8):2161−2166.LIUGang,MÜLLERDB.Addressingsustainabilityinthealuminumindustry:Acriticalreviewoflifecycleassessments[J].JournalofCleanerProduction,2012,35:108−117.ZHANGYan-lu,SUNMing-xing,HONGJing-lan,HANXiao-fei,HEJing,SHIWen-xiao,LIXiang-zhi.EnvironmentalfootprintofaluminumproductioninChina[J].JournalofCleanerProduction,2016,133:1242-1251.ZHANGPing.Theapplicationoflifecycleassessmentinthecleanerproductioninacarbonenterprise[D].Zhengzhou:HenanAgriculturalUniversity,2008.(inChinese)TANGChang-ting,JIANGHai-tao,ZHOUPing.Calculationofaluminumfluorideconsumptioninaluminumreductionproduction[J].LightMetals,2016(2):28−33.(inChinese)ROYP,NEID,ORIKASAT,XUQY,OKADOMEH,NAKAMURAN,SHIINAT.Areviewoflifecycleassessment(LCA)onsomefoodproducts[J].JournalofFoodEngineering,2009,90(1):1−10.BAREJ,GLORIAT,NORRISG.DevelopmentofthemethodandUSnormalizationdatabaseforlifecycleimpactassessmentandsustainabilitymetrics[J].EnvironmentalScience&Technology,2006,40(16):5108−5115.[19][10][20][11][21][12][22][13][23][14][24][15][25][26][16][27][17]基于生命周期评价的我国原铝生产的环境影响评估杨毅1，郭尧琦2,3，朱文松2，黄健柏1,3
1.中南大学商学院，长沙410083；2.中南大学数学与统计学院，长沙410083；3.中南大学金属资源战略研究院，长沙410083摘要：在当前生态文明建设的背景下，对原铝生产过程中的物料消耗、环境影响进行评估和核算，是进行环境外部性计量和促进铝行业绿色发展的基础性工作。为此，本文作者利用生命周期评价理论，采用拜耳法制备氧化铝工艺，根据不同发电方式分别对原铝生命周期内的环境影响进行评估，并分析4种主要环境影响类型的来源和分布。结果表明：(1)铝工业的负面环境影响一般来自于氧化铝冶炼、碳阳极制备和电解工艺，尤其是电解和氧化铝工艺。初级能源消耗(PED)、水资源消耗(WU)、温室效应(GWP)和淡水富营养化(FEP)是主要的环境影响类型。(2)火力发电模式生产原铝产生的环境负荷明显高于水力发电模式(前者温室气体排放系数为21800kgCO2eq/t(Al)，后者为4910kgCO2eq/t(Al))。(3)反映能源结构的发电方式和反映技术水平的直接排放所占比重揭示中国铝行业巨大的节能减排潜力，可制定发展清洁发电、提高能源效率和促进技术进步等相关的政策和措施。关键词：原铝；环境影响；生命周期评价；减排潜力(EditedbyWei-pingCHEN)
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