Vegetable waste supplemented with human or animal excreta as substrate for biogas production

摘要

Theobjectiveofthisstudywastodeterminetheeffectofco-digestionwithvegetablewasteonbiogasproductionfromexcretafromcattle,pigsandhumans.Therewereseventreatmentsarrangedinacompletelyrandomizeddesignwiththreereplicates.Thetreatmentswereinitialloadingrates(DMbasis)ofvegetablewaste(V)supplementedwithhuman(H),cattle(C)orpig(P)excreta.V2H1:2partsvegetablewastewith1parthumanfeces;V2C1:2partsvegetablewastewith1partcowmanure;V2P1:2partsvegetablewastewith1partpigmanure;V1H2:1partvegetablewastewith1parthumanfeces;V1C2:1partvegetablewastewith2partscowmanure;V1P2:nbsp;1partvegetablewastewith2partspigmanure.ThepHofthecontentsofthebiodigesters,andthegasproduction,weremeasureddailyuntiltheendoftheexperimentafter60days.Thecontentofmethaneinthegaswasmeasuredinsamplestakenafter14,21,28,35,42,49and56days.Gasproductionoverthe60dayperiodwas5timeshigheronthecombinationofonepartvegetablewasteandtwopartscattleorpigmanure,comparedwiththelowestvalueonthesubstrateofvegetablewastealone.However,theseresultsdidnotreflectthepotentialgasproductionfromthesubstratesasthereweremajordifferencesinthepHofthefermentingsubstratesoverthewholeincubationperiod(highervaluesonthetreatmentswithcattleandpigmanureandlowestvalueonthevegetablewasteassolesubstrate).Overall,nbsp;therewasanegativerelationshipbetweenthepHofthedigestamediumandtheaveragedailygasproduction.OnallsubstratesthepHdroppedrapidlyduringthefirst5to7daysofincubation;however,nbsp;theextentofthefallwassmaller,andtherecoverymorerapid,whencattlemanurewasthecompanionsubstratecomparedwithpigmanureonwhichthepHrecoveredmorequicklythanwithhumanfeces.Onthe100%vegetablewastesubstrate,thedropinpHwasmorepronounced,andtherecoverymuchslower,thepHnotbeginingtoriseuntilsome50daysafterthestartoftheincubation.Thetrendsformethanecontentofthegasweresimilartothoserecordedfortotalgasproduction,withhighestvaluesforsubstratesrichestinmanureandlowestvaluesfortreatmentswithhigherproportionsofvegetablewaste.TherelativevaluesforpHofthedigestaandmethaneinthegaswerepositivelycorrelated.Subsequentresearchwithfoodwasteassubstrateshouldbedirectedtosystemsofmanagementofthebiodigester(ie:ensuringaslowbuildupofthesubstrateconcentrationinthefirst14to21daysoftheincubation)orinclusionofbufferingagentssuchassodiumbicarbonate.