07Effectsofbiodryingprocessonmunicipalsolidwastepr

EffectsofbiodryingprocessonmunicipalsolidwastepropertiesF.Tambonea,B.Scagliaa,S.Scottib,F.Adania,⇑aGruppoRicicla,BiomassandBioenergyLaboratories,DiProVe,UniversityofMilan,ViaCeloria2,20133Milan,ItalybEcodecoS.r.l.,A2AGroup,Loc.CassinazzadiBaselica,27010Giussago,PV,ItalyarticleinfoArticlehistory:Received21February2011Receivedinrevisedform3May2011Accepted4May2011Availableonline23May2011Keywords:BiodryingofMSWHeatheatingvaluesofMSWMunicipalsolidwaste(MSW)Physicalpropertiesofbiodried-MSWPotentialbiogasproductionofbiodried-MSWabstractInthispaper,theeffectofbiodryingprocessonmunicipalsolidwaste(MSW)propertieswasstudied.Theresultsobtainedindicatedthatafter14d,biodryingreducedthewatercontentofwaste,allowingtheproductionofbiodriedwastewithanetheatingvalue(NHV)of16,779±2,074kJkg1wetweight,i.e.41%higherthanthatofuntreatedwaste.Thelowmoisturecontentofthebiodriedmaterialreduced,also,thepotentialimpactsofthewaste,i.e.potentialself-ignitionandpotentialodorsproduction.Lowwasteimpactssuggesttolandfillthebiodriedmaterialobtainingenergyviabiogasproductionbywastere-moistening,i.e.bioreactor.Nevertheless,resultsofthisworkindicatethatbiodryingprocessbecauseofthepartialdegradationoftheorganicfractioncontainedinthewaste(lossesof290gkg1VS),reducedofabout28%thetotalproduciblebiogas.2011ElsevierLtd.Allrightsreserved.1.IntroductionThelandfilldirective(EC,1999)leadstoimprovetherecyclingofmaterialsandenergyproduction(fuelfromwaste)frommunici-palsolidwaste(MSW).Thisdirectiveindicatesawellestablishedhierarchyinwastefate,i.e.prevention/reduction,reuseandrecy-cling,recoveryintheformofenergyandfinallylandfilling(Gargetal.,2009).Betweenthedifferentoptions,fortheMSWmanage-menttheproductionoffuelhasrecentlyfoundanewinterestasconsequenceofthepossibilitytoproducesolidrecoveredfuel(SRF),thatpresentssomebenefitsinitsutilization(Gargetal.,2009;Séverinetal.,2010).Theuseofwastetoproducefuelmeetstwodifferentgoals:toreducetheamountofwastetobelandfilledandtoprovideasub-stituteorasupplementtotheconventionalfossilfuels(Gargetal.,2009).Inaddition,becauseofthepresenceofbiogenicfractioninSRF(Séverinetal.,2010),greenhouseemissionsofburnedSRFcouldbepartiallyconsideredascarbonneutral,therebyreducingthetotalglobalinventoryofCO2emission(Gargetal.,2009;Morris,2010).Differenttechnologicalprocessesarenormallyadoptedtopro-duceSRF.ThemostsimpletechnologyconsistsinthemechanicalscreeningofMSWaimedatseparatingtheoversizefractionchar-acterizedbylowwatercontent(water250–300gkg1wetweight–w.w.)andhighNHV(NHV12,000kJkg1w.w.)(e.g.plasticsandpaper),i.e.SRF,fromtheundersizefractioncharacter-izedbyahighwatercontent(water500gkg1w.w.)andlowNHV(NHV9000kJkg1w.w.)(e.g.kitchenandgardenrefusewaste),beingthisfractionsuccessivelybiostabilizedbyanaerobicbiologicalprocess.Thecombinationofthesetreatmentsisknownasmechanicalbiologicaltreatment(MBT)(Velisetal.,2010).BiodryingprocessrepresentsanalternativetoMBTtoproduceSRFand,inthisway,itreceivedattentionbecauseofitsabilitytoproduceSRFwithhighNHVandlowmoisturecontent(200gkg1w.w.)(WiemerandKern,1995;Adanietal.,2002).Biodryingrep-resentsarelativenewtechnologywithlimitedresearcharticlespublishedonthistopic(e.g.Adanietal.,2002;Sugnietal.,2005;Zhangetal.,2008).Nevertheless,recently,Velisetal.(2009,2010),improvedgreatlytheknowledgeonbiodryingprocessresumingallinformationacquiredintotwoveryinterestingandcompletereviews.Biodryingisasolidstateaerobicprocessthatsubstantiallydif-fersfromMBTprocessbecauseMSWundergoesentirelytothebio-logicalprocess.Biodryingprocess,degradingpartoftheeasilybiodegradableorganicfraction(OF)containedinwaste,producesheatthatcombinedwithanadequateairflow-rate,allowsthefastevaporationofwastemoisturecontent(Adanietal.,2002).Thesuccessivemechanicaltreatment(sieving),appliedtoremovethefinefractionwithlowcalorificcontent(ash,stonesandglasses),allowstogetfinalSRFwithaNHVcomparabletothatofbrowncoal(NHVof16,000–19,000kJkg1w.w.1)(WiemerandKern,1995).Thankstotheefficientwaterremoval,biodryingrepresents,also,asuitablemethodtotreatveryhumid(e.g.watercon-tent550gkg1w.w.)whichwoulddeterminehighquantityofleachatereleaseifwasteisdirectlyburnedwithoutanypre-treatment(Zhangetal.,2008).Moreoverthedryingeffectandthepartialwastebiostabilizationthatoccursduringbiodrying0960-8524/$-seefrontmatter2011ElsevierLtd.Allrightsreserved.doi:10.1016/j.biortech.2011.05.010⇑Correspondingauthor.Tel.:[phone];fax:[phone].E-mailaddress:[e-mail](F.Adani).BioresourceTechnology102(2011)7443–7450ContentslistsavailableatScienceDirectBioresourceTechnologyjournalhomepage:(Yasuharaetal.,2010).ThebiodegradableorganicmattercontainedinMSW/SRFisresponsiblefort