FEASIBILITY STUDY OF PROMOTION.docx
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FEASIBILITYSTUDYOFPROMOTION
FEASIBILITYSTUDYOFPROMOTION
OFLARGEANDMEDIUMSCALEBIOGASPLANTSINCHINA
I.SeriouspollutionbylivestockwastesrestrictsthefurthereconomicdevelopmentinruralareasinChina
Withtheeconomicdevelopmentandtheimprovementofpeople'slivingstandard,demandsforlivestockproductsarecontinuouslyincreasing.Sincetheimplementationof"VegetableBasketEngineering",livestockfeedinghasdevelopedrapidly,andthescaleoflivestockfarmshasincreaseddramatically.Accordingtostatistics,bytheendof1997,thereweremorethan14,000large-andmedium-scalelivestockfarmsinChina(seeTable1).Developmentoflivestockfeedingnotonlymeetstheincreasingdemandforlivestockproductbutalsocontributestotheeconomicdevelopmentinruralareasandtheimprovementofpeople'slivingstandard.
Modernfeedingtechnologiespromotedthedevelopmentoflivestockfeeding,butbecausethiscausedtheseparationoflivestockfarmsfromplantationresulted,thecentraldisposalofwasteshasharmfulimpacttotheenvironment.Basedonthelivestockproducedinintensivepig,chicken,andcowfarmsin1997,thetotalamountofmanureandsewageproducedoverayearcanbecalculatedtobemorethan1.7billiontons.Besides,alargeamountofwaterisusedtowashthefarm.Therefore,theactualsewagedisposalshouldbefarlargerthanthatnumber.Becausemostfarmsarelocatedinsuburb,itisdifficulttotreatsuchalargequantityofmanureandsewagebyreturningtothefield.Thus,itisinevitableofthewastestopollutepotablewater,agriculturalecology,andlivingenvironment.
Suchalargequantityofmanureandsewagehasbecomeabigpollutantsourcearoundeachcity.Accordingtothetestresultofsewageoflarge-scalelivestockfarmsbyenvironmentalprotectionsector,thecontentofCODexceedsstandardby50~60times,BODexceeding70~80times,SSexceeding12~20times.Theenvironmentofmostlivestockfarmsisabominable.Inregionswheretheintensivelivestockfarmsconcentrate,theproblemofpollutionoflivestockwastebecomesveryserious.BureauofEnvironmentalProtectionofShanghaistatedthat,contentofammoniaandnitrogeninwaterinDaliugangexceededthenationalstandard(1mg/l)by4~5times,oreven8~9timesasthehighest;25.2%ofammoniaandnitrogenand47.7%ofCODinHuangpuRiverwasfrommorethan30large-andmedium-scalelivestockfarmslocatedinDaliugang.Table2showsthesituationofpollutionin
Disposaloflivestockmanurewithouttreatmentnotonlypollutesthesurroundingenvironmentbutalsothreatensthesustainableandhealthydevelopmentofthesefarmsthemselves.Untreatedmanurewillpolluteundergroundwater,andwilleventuallydecreasethequalityofwaterforlivestocktodrinkandwashingwater.Theviciouscyclehasseriouslythreatenedthefurtherdevelopmentoftheselivestockfarms.TheinvestigationofpigfarmsinBeijingandShanghaishowsthat,inrecentyears,thedeathrateofpigletandsowiskeptatahighlevel.Themajorreasonistheuseofundergroundwaterthathasbeenpolluted.Thesameresultcanbeseenintheinvestigationof6large-scalechickenfarmsinBeijing:
deathrateofchickenincreasesinrecentyears,whichhasrestrictedthedevelopmentofthesefarms.Inaddition,becausemanureandsewageseriouspollutedthesurroundingagriculturalfieldandwaterbody,peoplelivingaroundthefarmsarecontinuallycomplaining,andso-causedeconomicdisputesfrequentlyoccur.
Withthedeteriorationofenvironment,people'sawarenessofenvironmentalprotectionisstrengthened.Localgovernmentshaveissuedregulationstolimitthedisposaloflivestockmanurebyidentifyingthedisposalstandard.Iftheproblemoflivestockmanurecannotbeproperlysolved,thedevelopmentof"VegetableBasketEngineering"willbehampered,andthehealthydevelopmentofruraleconomicwillberestricted.
Atpresent,mostlivestockfarmsareinterestedin"energy-environmentengineering"inordertogetridofthedualrestrictionofmanurepollutionandrelativelawsandregulationsandthepredicamentthatfasterdevelopmentcausesmoreseriouspollution.Therecentsurveyshowsthat,80%ofthelivestockfarmsarewillingtoconstruct"energy-environmentengineering"inthenearfuture,ifthefundisavailable;16%ofthesurveyedfarmswillconstructthe"energy-environmentengineering"before2010;andonly4%willconstructtheengineeringafter2010.
II.CurrentSituationof"Energy-EnvironmentEngineering"ConstructioninChina
TheChineseGovernmentattachedmuchimportancetothedevelopmentof"energy-environmentengineering".TheMinistryofScienceandTechnologyandtheMinistryofAgricultureprovidespecialfundfortheprojectfromthe6thFive-Year-Planperiod(1981~1985),andorganizedrelativeinstitutestoresearchonthisproject.Bytheendof8thFive-Year-Planperiod,seriestechnologiesofdifferenttypes,usage,andproductsconcerningtreatment,development,andutilizationofagriculturalwastessuchaslivestockmanureweredeveloped.Thesetechnologiesincludepre-treatment,anaerobicdigestion,biogastransfer,fertilizerproduction,post-treatmentofliquidafterdigestion,basedonthespecialtyofpigmanure,chickenmanure,andcowmanure.Someoftheindividualtechnologiesandcriteria,suchasresearchonbiologicalanaerobicfermentationmechanism,designoffermentationprocessofdifferentmanure,rationofbiogasproduction,ratioofCODremoval,havereachedtheinternationalleadinglevel.The"energy-environmentalengineering"technologyhasmulti-functions,i.e.environmentalprotection,energydevelopment,fertilizerproduction,andwatersaving.Thatistosay,thetechnologywillbringeconomicbenefitandsocialbenefit,andtheinvestmentislowerthanothercountries'technologies.
Afewdemonstrativeprojectswerecarriedouttoassisttheresearchduringthe6th,7th,and8thFive-Year-Planperiod(1981~1995),suchasinShanghaiXinhouFarm,ZhejiangFushanLivestockFarm,ShenyangMasanjiaPigFarm,andShanghaiJiadingBreedingFarm.Thesedemonstrativeproject,whichhavebeenconstructedindifferentregionsandunderdifferentnaturalcondition,havebeensuccessfullyoperatingformorethan5years.
Besides,onthebasisofcompletionof8thFive-Year-Planresearchproject,thedesignstandard,constructionandevaluationstandardfortreatmentandutilizationoflivestockmanurewereformulated.Thisshowsthatthetechnologieshavebeenmature,andthattheprimaryphaseofresearchonintegratedutilizationoflivestockmanureinChinahasended.
Becausetherawmaterialforfermentationinlivestockfarmsismainlylivestockmanure,andtheproportionsofsuspendingsubstanceandsolidsubstancearehigh,thecommontechnologicalprocessesarethefollowing:
first,full-mixingbiogasfermentationequipment,fermentedatnormaltemperature,therawmaterialiskeptforabout40days,andthebiogasproductionrateislow,approximately0.13~0.3m3/m3day;second,塞流式fermentationprocesswithstirring,slurrycircling,andtemperaturepreservingequipment,thefermentationtemperatureisbetween15~32C,andthebiogasproductionrateus1.2~2.0m3/m3day;third,up-flowslurrybed上流式污泥床反应器(UASB)reactororanaerobicfilter(AF),ortheprocessthatcombinestheabovetwotogether,theadvantageofthisprocessisanaerobicmicroorganismcanbewelladheredtoimprovethereactionspeedandbiogasproductionquantity.
BiogastechnologyforlivestockfarmsinChinahasbeengraduallymaturesincethe1980s,andtheefficientengineeringandtechnologysystemwithmulti-functionshasbeenformed.Atpresent,thenormaltechnologicalprocessincludes:
1)pre-treatmentequipment,2)anaerobicdigester,3)equipmentforbiogascollection,storage,andtransfer,4)equipmentforpost-treatmentofliquidafterdigestion,and5)systemofsolidresiduetreatment.Theimprovementoftheseequipmentorsystemhasprovidedtechnologicalconditionsforincreaseofbiogasproductionrate,steadyoperationofsystem,decreaseofpollution,aswellasensuringtheefficientandsteadybiogassupplyforusers.
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Biogasuse
Compostfromsolidresidue
Wastewater
Manurepool
Irrigationusingliquidafterdigestion
Full-mixingorimprovedanaerobicdigester
后沉池
Figure1isthetechnologicalprocessforanaerobictreatmentinpigfarms
Figure1
(1)Combinationofanaerobictreatmentandagriculturalutilization
Wastewater
Sandsedimentpool
Separatorofsolidandliquid
Adjustingpool
Biogas
Waterdisposal
Secondsandsedimentpool
Anaerobicdigester
Acidificationpool
曝气池
Partialcircling
Compost
Figure1
(2)Commontreatment
Biogas
Biogasdigester
Storagepool
Compoundfertilizerfromsolidresidue
Slurry
Feed
Fishfeedingpool
Aquaticplantpool
Irrigation
Liquidafterdigestion
Figure1(3)Ecologicaltreatmentandutilization
Generalspeaking,alarge-scalebiogasplantproducesbiogas1,000~2,000m3/day,andthetotalinvestmentis3~10millionRMByuan;amedium-scalebiogasplantproducesbiogas50~1,000m3/day,andthetotalinvestmentis0.8~3.0millionRMByuan.Becausethelivestockfarmsaredevelopingtowardsmorecentralized,thedevelopmentofbiogasplantinthe21stcenturywillfocusonlarge-scalebiogasplant.
III.ExistingProblemsandBarriers
1.Conditionsfortechnologyindustrializationneedimproving
Intermsoftechnologyindustrialization,thecommercializationoflarge-andmedium-scalebiogasplantsisfacingthefollowingproblems:
✧Therearenostandardizedsystemofdesignandconstructionforlarge-andmedium-scalebiogasplants,andthestandardforqualificationappraisalofbiogasplantconstructionisinsufficient.
✧Automat