1s20S0301479712003933main英国

Foodwasteco-digestionwithsewagesludgeeRealisingitspotentialintheUKEleniIacovidou,Dieudonné-GuyOhandja,NikolaosVoulvoulis*CentreforEnvironmentalPolicy,ImperialCollegeLondon,SouthKensingtonCampus,LondonSW72AZ,UKarticleinfoArticlehistory:Received6March2012Receivedinrevisedform26July2012Accepted27July2012Availableonline30August2012Keywords:FoodwasteSewagesludgeAnaerobicco-digestionBenefitsConstraintsRegulatoryframeworkabstractTheapplicationofanaerobicco-digestionoffoodwastewithsewagesludge,althoughwellestablishedinmanyEuropeancountries,isstillinitsinfancyintheUK.Thisprocesshasmanybenefitstooffer,withasuccessfulapplicationoftenassociatedwithincreasedrenewableenergypotential,outweighingconstraintsassociatedwiththevariabilityoffoodwasteanditshandlingrequirementspriortoco-digestion.Withbothregulationsandwaterinfrastructuresdesignedandconstructedonthebasisoflinearviewsandsectorialrequirementsandconditionsandtechnologiesfromthepastinmanypartsoftheworld,intheUK,sewagesludgeandfoodwastedigestionoperationsarealsounderverydifferentregulatoryandmanagementregimes.Withsustainabilityrequiringthatwedonotaddresssingleissuesinisolation,butthroughasystemsapproachthatdeliversintegratedsolutions,co-digestionoffoodwastewithsewagesludgecouldbecomesuchasolution.Ifcarefullyapplied,co-digestioncandeliverbeneficialsynergiesforthewaterindustryandauthoritiesresponsibleforfoodwastemanagement.Thecollaborationofallrelevantstakeholdersandregulatorstosupportchangestocurrentregulatoryframeworkstoenablethis,isproposedasthewayforward,particularlyastheircomplexityhasbeenidentifiedasthemajorhurdletotheimplementationofco-digestionintheUK.
2012ElsevierLtd.Allrightsreserved.1.IntroductionAnaerobicdigestion(AD)convertsorganicmatterintobiogasarenewablesourceofenergy,anddigestate,avaluablefertilizerandsoilconditioner.ADiswidelyusedforthestabilisationofsewagesludgethatisamixtureofprimaryandbiologicalsludge.Thissludgeisthemajorby-productofthewastewatertreatmentprocessesandassuchADisawell-establishedprocessinmanywastewatertreatmentplantsworldwide(Arnaizetal.,2006;ParkinandOwen,1986).Inrecentyears,theneedforrenewableenergygenerationandtheneedtodivertbiodegradablewastefromlandfillhavepushedADintothemarketforthetreatmentofbiodegradablemunicipalwaste.Outofthebiodegradablefractionofmunicipalwaste,foodwasteisthemostchallengingbecauseofitshighmoisturecontentandreadilybiodegradablenature(Davidssonetal.,2008;Strootetal.,2001).Althoughmanyoptionshavebeensuggestedforthemanagementoffoodwaste,includingincineration,composting,theuseoffoodwastedisposalunits(FWDs)andAD,ADhasattractedmoreinterest,particularlyinpolicymaking,duetoitspotentialforenergygeneration(Banksetal.,2008;Gallertetal.,2003;Iacovidouetal.,2012b;Zhangetal.,2005,2007b).However,foodwastecanbehighlyvariabledependingonitssource,anditscompositionmightdiffersignificantlyfromoneplacetoanother,whichcanbeahindrancetoitssuccessfulandefficientdigestion(Zhangetal.,2007b).Oneapproachaimingtoovercomethislimitationistheuseoffoodwasteasaco-substrateinsewagesludgedigestion,aprocessknownasco-digestion.Co-digestioninvolvesthedigestionoftwosubstratestogetherasawaytoimprovedigestionefficiencyandincreasetheenergyoutput.Itisawell-establishedprocessinEurope,withGermanyandScandinaviabeingthepioneers,havingover20yearsofexperience(Appelsetal.,2011;BraunandWellinger,2009;EnvironmentAgency,2010).Thenumberofco-digestionplantsiscontinuouslyincreasinginmanyEuropeancountriesandhasbecomeastandardpracticeintheagriculturalsector(BraunandWellinger,2009).Newplantsforsewagesludgeandfoodwasteco-digestionhaverecentlybeenbuiltinDenmark,GermanyandSwitzerland(BraunandWellinger,2009).IntheUK,thefirstco-digestionplanthasbeeninstalledatHolsworthy,Devonforthetreatmentofanimalmanureandfoodwaste(EnvironmentAgency,2010).Nevertheless,theco-digestionofsewagesludgewithfoodwastedoesnotasofyetexist.Tochangethis,decisionshaverecentlybeentakenintheUKtopromotetheuseofco-digestionoffoodwastewithsewagesludge,withthewaterindustrybeingdesignatedasamajorpotential*Correspondingauthor.Tel.:þ44(0)2075947459.E-mailaddress:[e-mail](N.Voulvoulis).ContentslistsavailableatSciVerseScienceDirectJournalofEnvironmentalManagementjournalhomepage:
2012ElsevierLtd.Allrightsreserved.(2012)267e274implementer(Defra,2009,2011).Thiscouldbeamajoropportunityforthewaterindustrytoincreaseitsrenewableenergygeneration,therebyreducingitsenvironmentalfootprint(Defra,2009;Kielyetal.,1997).Atthesametime,theapplicationofco-digestionoffoodwastewithsewagesludgewillhelptheUKtomeettheEULandfillDirectivetargets(1999/31/EC),whichrequirethereductionofbiodegradablewastedisposedoftolandfillto35%by2020,basedonthe1995levels(EuropeanCouncil,1999).Additionally,thisprocesscouldcontributetotheachievementoftargetssetbytheClimateChangeActandtheEURenewableEnergyDirective.TheClimateChangeActrequiresthereductionofcarbonemissionsby34%by2020,basedonthe1990levels,whereastheEURen