Sewagesludgehandlingwithphosphorusutilizationlifec

SewagesludgehandlingwithphosphorusutilizationelifecycleassessmentoffouralternativesKristinJohanssona,MariaPerzona,MorganFro¨lingb,AgnesMossakowskac,MagdalenaSvanstro¨ma,*aChemicalEnvironmentalScience,ChalmersUniversityofTechnology,SE-41296Go¨teborg,SwedenbLaboratoryforEnergyandtheEnvironment,MassachusettsInstituteofTechnology,77MassachusettsAvenue,Cambridge,MA02139,USAcEnvironmentandDevelopment,StockholmWaterCo.,SE-10636Stockholm,SwedenReceived31January2005;receivedinrevisedform8September2006;accepted1December2006Availableonline15February2007AbstractFourhandlingoptionsforsewagesludgewerestudiedfromanenvironmentalsystem’sperspectiveusinglifecycleassessment.Thestudiedoptionswererestorationofminingareas,compostingwithotherbiomaterialsforuseongolfcourses,hygienisationthroughstorageforagricul-turaluse,andsupercriticalwateroxidationwithphosphorusrecovery.Theresultsarediscussedintermsofimpactonglobalwarming,acidi-fication,eutrophication,andtheuseoffiniteresourcesandprimaryenergy.Averylargeimpactofincludingbiogeochemicalemissionsfromsludgehandlingandspreadingonlandcanbeseen.Systemexpansionsforreplacedartificialfertilizersalsohadamajorinfluenceontheresults.Itisclearthatitisimportantfortheenvironmentaloutcomeofsludgetreatmentoptionsthatbiogeochemicalemissionsfromsludgearemin-imizedandthatnutrientsandotherresourcesareutilizedefficiently.2006ElsevierLtd.Allrightsreserved.Keywords:Municipalsludgetreatment;Restorationofminingarea;Composting;Agriculture;Supercriticalwateroxidation;SCWO;LCA1.IntroductionLinearmaterialflowsleadtodepletionatthesourceandpollutionatthesink.Theuseofrenewablematerialsanden-ergysourcesinadditiontotheefficientrecoveryofresourcesfromallwasteflowsaresomeofthemeasuresthatneedtobetakeninordertoachievemorecyclicalflowsinsociety.Sew-agesludgeisaflowthathasbeendiscussedinsuchterms.Sludgegeneratedinurbanareasamountstovolumeslargeenoughtobecomeproblematicwithoutproperhandlingoptions.Thepresent25EUmemberstatestogetherproducedaround10milliondrytonnesofsewagesludgeintheyear2000[1],whiletheUnitedStatesproducedanestimated7milliondrytonnesthatsameyear[2].Thisisasubstantialamountofmaterialtohandle.Thecompositionofthesludgeimpliesapotentialhealthandenvironmentalriskaswellasanopportunitytocreatevalueforsociety.Theorganicmaterialandthenutrientsinthesludgemakeitanexcellentsoilcondi-tionerandfertilizer,butalsoleadtoariskofeutrophication.Theenergycontentmakesitapotentialbiofuelthatcanaidinthechangetowardsarenewableenergysystem.However,theissueofgreatestconcerninthecurrentdebateonhowthesludgeshouldbehandledisthepresenceofheavymetalsandpathogensaswellasendocrinedisruptersandotheror-ganicmicropollutants[3e5].Inspiteofthefactthat,since1990,theSwedishgovernmenthasstressedtheimportanceofrecyclingnutrientsfromsewagesludge,littlesludgeisusedinagriculture,despitethelowlevelsofcontaminationcomparedtoothercountries[5].In2000,aSwedishgovern-mentinvestigationproposedthegoalofrecycling75%ofthephosphorusfromwasteandsludgetoproductivesoilsby*Correspondingauthor.Fax:þ46317722995.E-mailaddress:[e-mail](M.Svanstro¨m).0959-6526/$-seefrontmatter2006ElsevierLtd.Allrightsreserved.doi:10.1016/j.jclepro.2006.12.004JournalofCleanerProduction16(2008)135e151[6].In2003,theSwedishEnvironmentalProtectionAgencysuggestedamoremodestgoalof60%forrecyclingofphosphorustoproductivesoilsby2015,ofwhichatleasthalftoagriculture[7].Policy-makers,decision-makers,farmersandconsumersneedtoknowifandhowthiscanbeachievedwithoutputtinghealthandtheenvironmentatrisk.Thisstudyevaluatesselectedpotentialenvironmentalimpacts,fromalifecycleperspective,offourdifferentwaysofutilizingthephosphorusinsewagesludge.StockholmWaterCo.[8]isthelocalwaterandsewagecompanyinStockholm,Sweden.Theirlargestwastewatertreatmentplant(WWTP),inHenriksdal,generates50700tonnesofdewatered,digestedsludgeannually[9].Intheirsearchtoidentifyasustainable,long-termsludgetreatmentstrategythatwillfulfilfutureregulationsanddemands,Stock-holmWaterCo.ispresentlyfocusingonfourdifferentoptions:restorationofminingareasbyBolidenMineralAB,compost-ingwithotherbiomaterialsbyEconovaABforuseongolfcourses,hygienisationthroughstoragebyRagn-SellsABwithsubsequentuseinagriculture,andsupercriticalwaterox-idation(SCWO)withphosphorusrecoverybasedontheAquaReciprocessdevelopedbyChematurEngineeringABandFeralcoAB.Inthispaper,thesemethodswillbereferredtoasBoliden,Econova,Ragn-SellsandAquaReci.BolidenMineralABisoneoftheworld’sleadingcompa-niesintheminingandsmeltingsector.Inordertorestoremin-ingareasthathavebeentakenoutofuse,largeamountsofmaterialareneededtocoverthegroundandtoestablishveg-etation.Byusingsewagesludge,theuseofmoraineandarti-ficialfertilizerforthesepurposescanbeavoided.EconovaABisaSweden-basedcompanythatconvertsresidualmaterialsfromindustryandsocietyintoproducts.Hygienisedsewagesludgeisusedasoneoftherawmaterialsfortheproductionofsoil,fore.g.theconstructionofgolfcourses.Whenusingthesludgeproductforconstructionofagolfcourse,theuseoftopsoilandartificialfertilizerisavoided.Ragn-S