(英)市政固废的卫生填埋与焚烧处理的生命周期分析

(英)市政固废的卫生填埋与焚烧处理的生命周期分析

Vol.12　№.3　　　　　　　　Trans.NonferrousMet.Soc.China　　　　　　　　Jun.2002[ArticleID]1003-6326(2002)03-0545-04

Lifecycleanalysisofsanitarylandfillandincinerationof

①

municipalsolidwaste

NIJin2ren(倪晋仁),WEIHong2lian(韦洪莲),LIUYang2sheng(刘阳生),ZHAOZhi2jie(赵智杰)

(CenterforEnvironmentalSciences,TheKeyLaboratoryforWaterandSedimentSciences,

MinistryofEducation,PekingUniversity,Beijing100871,China)[Abstract]Environmentalconsequencesfromsanitarylandfillaswellaswithwerecom2

paredintermsoflifecycleanalysis(LCA)forLaohukengWaste2isShenzhen.AvarietyofdifferenceswillberesultedfromthetwotheconclusionisifthecompensatoryphaseinpowercantheofLCA.Uponthecompensatoryphaseconsequencesfromthelandfillwillbegeneration,althoughthereversedresultscanbeob2tainedasisInaddition,mitigationofenvironmentalimpactsthroughthepollutanttreatmentinprocesswillbemoreeffectivethaninthelandfillprocess.[Keywords]sanitarylandfill;incineration;lifecycle;compensatoryphase[CLCnumber]X705[Documentcode]A

1　INTRODUCTION

Therapideconomicdevelopmentandurbaniza2tioninChinainrecentyearshasresultedinsubstan2tialincreaseofsolidwaste.Itwasestimatedthatthetotalproductionofmunicipalsolidwaste(MSW)in2000hasbeenupto120～140milliontons.Howev2er,thetreatmentrateisverylow,andthustheenvi2ronmentalconsequenceofMSWbecomesaseriousprobleminmorethan200largecities[1].

Consideringthenegativeimpactstolivingenvi2ronments,landscapesandhumanhealth,moreandmoreattentionhasbeenpaidtothetreatmentanddisposalofMSW.Atthepresentstage,theMSWtreatmenttechnologiesprimarilyincludesanitarylandfill,incineration,compostingandrecovery/recy2cling.Byuseofpropertreatmentanddisposaltech2nologies,theenvironmentalimpactofMSWcouldbegreatlymitigated,althoughsomesecondarypollutioncouldbestillinevitableinthewholeprocessesandtheimpactmechanismsorextentscouldbedifferentfordifferenttechnologies.Finnveden[2]studiedsomeis2suesthatmustbeconsideredinthelifecycleassess2ment(LCA)forsolidwastemanagementsystems,andfiveissueswereindicated,i.e.theupstreamanddownstreamsystemboundaries,theopen2loopalloca2tionproblem,themulti2inputallocationproblem,thetimeasasystemboundaryandthelifecycleimpactassessment.Denison[3]comparedthemajoroptionsformanagingMSWprevailedinthestudiesinNorthAmericanonthebasisofenvironmentalconsidera2tions.

Inordertoevaluatetheenvironmentalconse2quencesofMSWtreatment/disposalinthewholelife2

①[Receiveddate]2001-10-16;[Accepteddate]2002-01-28

cycle,acasestudyismadeforLaohukengWaste2dis2posalPlantunderconsiderationinShenzhen,whereMSWtreatment/disposalbecomesoneoftheprimaryconcernsbythelocalgovernment.Twotechnologiesareconsidered,i.e.thesanitarylandfillorincinera2tionwithpowergeneration.Forcomparison,theLCAisappliedforbothtechnologieswithfullconsid2erationofthedifferentprocessesandenvironmentalconsequences.

2　LIFECYCLEASSESSMENT

Lifecycleassessment(LCA)[2,4,5]isatooltoquantifyenvironmentalburdensassociatedwithprod2uctsoractivitiesthroughouttheirlifecycle,or“fromcradletograve”.Sinceitsbirthandfirstapplicationtoindustrialproductin1960s,manystudycaseshavebeendevelopedintheworld.LCAdevelopedrapidlyduringthe1990sandhasreachedcertainlevelofhar2monizationandstandardization.

LCA[6～8]studiedtheoverallenvironmentalbur2densgeneratedbyproducts,processesoractivitiesduringtheirentirelifecycle,whichincludesthestagesfromtheextractionandprocessingofrawma2terials,manufacturing,throughproduction,packag2ing,transportation,distribution,useandreuse,andmaintenance,recycling,tothefinaldisposal.Thegeneralcategoriesofenvironmentalimpactsneedingconsiderationincluderesourceuse,humanhealth

,andecologicalconsiderations.TherearefourphasesforLCA,whichinclude:(1)goaldefinitionandscoping;(2)inventoryanalysis;(3)assessmentofpotentialenvironmentalimpacts;(4)interpretationorimprovementanalysis.

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Jun.2002Trans.NonferrousMet.Soc.China　　　　　　　　　

Table1.

3　LCAOFLANDFILLANDINCINERATION3.1　Goaldefinitionandscoping

The“functionalunit”istakenas600tMSWforbothlandfillandincinerationtechnologies,whichisdeterminedaccordingtothedailydisposalcapacityoftheLaohukengWasteIncinerationPlant.Forthedefinitionofsystemboundariesforlandfillandincin2erationofMSW[2],anequivalentamountofelectrici2tygeneratedfromtheincinerationprocessisassumedtoaddtothelandfillsystem,andthealternativeheatsourceisassumedtobecoalfuels.,disposalcapacityofationplant1.918×105Forcompen2sationoftheamountofelectricity,81.32tofstandardcoalisneededaccordingtotheaverageconsumptionrateof0.424kgstandardcoalperkW?h.Thelifecycleconcernedhereinincludesthetrans2portation,treatment/disposalandstabilization.Notethatthedifferentwastecompositionandenvironmen2talfactors,thedegradationrateofChineseMSWismuchhigher.Therefore,a102yeartime2periodisusedherein[9].

3.2　Inventoryanalysis

ThecontentpercentagesofMSWcomponentssuchasC,H,N,S,Cl,FandH2Oare39.43%,6.24%,1.41%,0.81%,0.069%,0.017%and38.46%,respectively.Transportationdistanceisas2sumedtobe40km.Dieselconsumptionisabout0.04L/(t?km),so960Ldieselwillbeconsumedbycon2veying600tMSW.Withregardtotheemissions,twoconditionscouldbeconsidered:treatmentornot.Inthispaper,thegasfromlandfillisassumedtore2leaseintotheairdirectlywithoutgasrecovery.Thepollutantcontentoflandfillleachatedependsonifitistreatedornotbeforedischargedintosurfacewaterbodies.Thefluegasofincineratorcouldbereleasedintotheairdirectlyorbetreatedwithsemi2drypro2cess.Theaveragetotalleachatefromlandfillisabout163m3for600tofMSWduringthelifecycle.Thetotalmassofbottomslagandflyashisabout150t.Theemissiondataduringthelifecycleareshownin

3.3　Impactassessment

Accordingtothelife2cyclecharacteristicsofwastetreatment/disposal,itsenvironmentalimpactsareclassifiedintofivekinds[10,11]:energydepletionpotential(EDP),globalwarmingpotential(GWP),acidificationpotential(AP),eutrophicationpotential(EP),andphotochemicaloxidantpotential(POCP).Theequivalentrelationship[12]environmentalandisTable2.Theof,undertwoaretreatmentbeforedischarge,foranyspecificpotentialenvironmentalim2pactfromthelandfillisassumedtobe1.0unitforreference,thentherelativelevelsofstandardizedpo2tentialenvironmentalimpacts,includingthoseoftheincinerationprocesswithpowergenerationareevalu2atedrespectively.TheresultsareshowninTable4.Therelativeweightcoefficientforanyimpactcouldbeobtainedaccordingtotheanalytichierarchypro2cess(AHP).Theimportancelevel[11]ofeachfactorisshowninTable5.TheweightcoefficientsofEDP,GWP,AP,EPandPOCPare0.43,0.35,0.13,0.03and0.06,respectively.Theintegratedstan2dardizedfactorsoftheenvironmentalimpactsfromthetwotreatmentprocessesareobtainedwiththefol2lowingindex

5

Q=

i=1

∑q

i

η×i(1)

where　Qisanindexthatintegratesvariousenviron2

mentalimpacts,qithevalueofafactorforanyspe2cificimpact,ηitheweightcoefficientforafactor.Itshouldbeindicatedthatanyofthetwoprocessesdis2cussedherecouldresultinnewpollutants.Forrefer2ence,assumeQ1=1.0forthelandfillprocess,thenQ2wouldbe0.78forincinerationincaseofnotreat2mentatall.Similarly,ifpollutanttreatmentwereconsidered,Q′1wouldbeequalto0.98forlandfill,andQ′2wouldbe0.49forincineration.Therefore,itisclearthatthelandfillprocesswouldresultinmoresignificantenvironmentalconsequencesthanthosefromincinerationwithpowergenerationinbothcasesdiscussedabove.3.4　Improvementanalysis

()

HF

CxHy0.410.41

0.43

0.11

COD3.260.

033

NH32N0.0820.0057

ProcessLandfill

TreatmentNoYesNoYes

CO2230.01230.01869.08869.08

CO0.0780.0781.090.55

CH417.1917.19

NOx0.300.301.070.30

SO24.894.899.730.19

H2S0.00770.0077

HCl

Incineration

0.00400.00250.0016

0.0720.00360.00400.00250.0016

Vol112　№13　　Lifecycleanalysisofsanitarylandfillandincinerationofmunicipalsolidwaste

Impact

PollutantCO2

GWP

COCH4NOx

EP

NH32NCODNOx

AP

SO2HClHF2SO2NO3-CO2Reference

constituent

Significance

12251.353.640.230.701.000.6088

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treatmentintheincinerationismoreeffectivethaninthelandfillprocess.Withthetreatmentconsidera2tion,theintegratedindexforoverallenvironmentalimpactscouldbereduced37%(from0.78to0.49)intheincinerationprocess,whereasonly2%(from1.0to0.98)reductioncouldbeobtainedintheland2fillprocess.AnotheraspectthatisnotconsideredhereinisthereuseofproducedgasessuchasCH4,whichisbeneficialtobothenvironmentalprotectionandeffectiveuseofenergy.4thecompensatorypowergener2inlandfillsystemisnotconsidered,thenpoten2tialenvironmentalimpactswouldbequitedifferent,therelevantresultsareshowninTable6.Withthesamereferencesforvariousimpactsasusedintheaforementioned,thecalculatedresultsforno2compen2satorycasearegiveninTable7.Forlandfillsystem,wehavetheintegratedindexQ??1=0.28,andQ??2=0.78forincinerationsystem,ifneglectingthepollutanttreatment.However,Q??′??′1=0.26andQ2=

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