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ORIGINALARTICLEOpenAccessReturns,setbacks,andfutureprospectsofbio-energypromotioninnorthernEthiopia:thecaseoffamily-sizedbiogasenergyHaftuEtsayKelebeAbstractBackground:Solidbiomass-basedenergyisexpectedtoretainitspositionasasolefuelsourceforhouseholdsintheruralpartofEthiopiaunlessalternativeenergysourcesareintroduced.
Synthesizingsmall-scalerenewablealternativeenergysources,suchasbiogasenergy,intotheenergymixhasbecomeanimportantstrategytoovercometheenergyhungerofitsruralresidents.
Aspartofthegovernmentpolicy,small-scalebiogasdigestershavebeeninstalledinselecteddistrictsandregionsofthecountrysince2007.
Thereis,however,limitedevidenceonwhetherornottheintendedobjectivesofthedomesticbiogasinitiativehavebeenactualizedbytheparticipantsoftheproject.
Thispaper,therefore,intendstoinvestigatetheeconomicbenefitsofdomesticbiogasplantsalongwiththechallengesfacingitandfutureprospectsofthebiogasinitiativeinselecteddistrictsofnorthernEthiopia.
Methods:Qualitativedataweregatheredusingfocusgroupdiscussionandkeyinformantinterviews.
Asurveyof400householdswasalsoadministeredtocapturecrosssectionaldatausingstructuredquestionnaires.
Thequalitativedatawereanalyzedusingcontentanalysis.
Apropensityscorematchingmodelwasemployedtoevaluatetheeffectsofdomesticbiogastechnologyonenergyexpenditure,cropyield,andthesubstitutionofchemicalfertilizers.
Results:Thestudyfindsthatbiogasadoptershavereducedtheirmonthlyenergyexpenditureonaverageby20–36%.
Moreover,theexistenceofapositivecropyieldpremiumof1.
5quintal/year/householdwasobservedasaresultofusingbio-slurryasafertilizer.
Thekeyfactorsthatlimittheextensionofbiogastechnologytopotentialbiogasadoptersarethepresenceoffaileddigesters,aninadequateplotoflandforthedigesterconstructionandawateravailabilityproblem.
Inlightofsuchbarriers,however,thestudyfindsthatmorefavorableenvironmentsforthewidespreaduseofthetechnologyexist.
Conclusions:Biogasuserhouseholdshavesignificantlyreducedtheirenergyexpenditurecomparedtonon-biogasadopters.
Nevertheless,despitethemodestincreaseincropyield,theoveralleffectofbio-slurryapplicationoncropproductivityandsubstitutingchemicalfertilizerswasnotsignificantbecauseofanimproperbio-slurryutilizationandmanagement.
Keywords:Biogasenergy,Bio-slurry,Energyexpenditure,Futureprospects,TigraiCorrespondence:haftu.
etsay@mu.
edu.
et;haftu04@gmail.
comDepartmentofAgriculturalandResourcesEconomics,MekelleUniversity,Mekelle,EthiopiaEnergy,SustainabilityandSocietyTheAuthor(s).
2018OpenAccessThisarticleisdistributedunderthetermsoftheCreativeCommonsAttribution4.
0InternationalLicense(http://creativecommons.
org/licenses/by/4.
0/),whichpermitsunrestricteduse,distribution,andreproductioninanymedium,providedyougiveappropriatecredittotheoriginalauthor(s)andthesource,providealinktotheCreativeCommonslicense,andindicateifchangesweremade.
KelebeEnergy,SustainabilityandSociety(2018)8:30https://doi.
org/10.
1186/s13705-018-0171-2BackgroundIndevelopingcountries,around2.
5billionpeoplerelyonsolidbiomasssuchasfuelwood,charcoal,agriculturalwaste,andanimaldungtomeettheirenergyneeds,pri-marilyforcookingandlighting[1].
Inmanycountries,particularlyinruralareas,theseresourcesaccountforover90%ofhouseholdenergyconsumption[2].
Suchahighbiomassenergyconsumptionhabitindevelopingcoun-trieshasresultedinvariousenvironmentalproblemslikedeforestation,soilerosion,andpoverty[3,4].
AreportbytheFAO[5],forinstance,showsthat5%ofglobaldefor-estationisduetofuelwoodconsumption,and55%ofthewoodextractedfromforestsisusedforfuelpurposes.
Sub-SaharanAfrica(SSA)inparticularisthehighestsub-regionintermsofbiomassenergyutilization,whichaccountsforabout85–95%oftotalenergy,whereas60–90%isusedforthedevelopingworldasawhole[6,7].
Inthissub-regionwheretraditionalenergysourcesentirelysatisfythemajorityoftheenergyneedsofruralhouseholds,biogastechnologycanbeviewedasoneoftherenewableandsustainabletechnologiestoreduceitsenergyhungerandenvironmentalproblems[8].
TheauthorfurtherassertsthatAfricancountrieshaveatremendousbiogaspotentialasitisproducedfromagriculturalresidues,isrelativelysimpleandcanoperateonasmallandalargescaleinbothurbanandrurallocations.
Moreover,themajorityofpeopleinSSAalsoexceedinglydependoncombustiblesfordo-mesticcookingandheatingpurposes.
Combustiblere-newableenergyresources,inparticularcharcoal,woodfuel,driedcrop,andanimalresidues,haveenvironmen-talandhealtheffectsduetoitsincompletecombustion[9].
Therehavebeenglobalandcontinentalinitiativestowardsthedevelopmentandpromotionofalternativeenergysourcesinthepastthreedecadestoaddresstheadverseimpactsofsolidbiomassenergyconsumption[10].
TheimportantcontinentalinitiativeinAfricaisthe"AfricaBiogasPartnershipProgramme,"whichwaslaunchedin2007todisseminatesmall-scalebiogasplantsinselectedcountriesofthecontinent.
TheAfricaBiogasPartnershipProgrammeisapartnershipbe-tweentwoDutchnon-profitorganizations,HumanistInstituteforDevelopmentCooperation(Hivos)andtheNetherlandsDevelopmentOrganization(SNV),whichsupportsdomesticbiogasprogramsintenSSAcoun-tries,ofwhichEthiopiaisoneamongthebeneficiariesoftheprogram[11].
Ethiopia'senergychallengeshavebeendescribedasacutedespitetheavailabilityofalargeenergyreserveinthecountry.
Thisenergyscarcityproblemismanifestedmainlyintheformofaverylowper-capitaelectricityconsumptionandthedominanceoftheuseoftrad-itionalbiomassfuels.
Therearereportswhichshowthattheper-capitaenergysupplyandconsumptionofEthiopiaislowerthaneventhatofmostofthesub-SaharanAfricancountries.
AreportbytheInter-nationalEnergyOrganization[12],forexample,showsthattheper-capitatotalprimaryenergysupplyinEthiopiawasmerely0.
4tonoftheoilequivalentwhiletheaverageforAfricaamountedto0.
67in2011.
Thesamesourcealsoindicatesthattheannualper-capitaelectricityconsumptioninEthiopiawasonly55kWhwhileitwas592kWhforthewholeofAfrica.
Moreover,thepercentageofpopulationwhoreliedonthetraditionaluseofbiomassfuelforcookingwas93%inEthiopiain2009,whileitwas65%inAfrica,77%insub-SaharanAfrica,and39%intheworldasawhole[13].
ThisoverdependenceontraditionalfuelsourcesinEthiopiahassignificantlycontributedtosevereenvironmentaldeg-radationssuchasdeforestation,soildegradation,andlossofbio-diversity[14].
Itisanticipatedthattraditionalbio-massfuelswillcontinuetobetheprimarycookingfuelsinmostruralcommunitiesofthecountryatleastinthenearfuture.
Hence,reducingenergy-povertyinsuchcontextdependsonthescaleofutilizingtechnologiesthatminimizetheharmfuleffectsoftraditionalbiomassfuels.
Amongothers,theuseofbiogasenergyhasbeenindi-catedtobevitaltoincreasecookingefficiency,reducesmoke,reducesolidfuelwoodconsumption,andimprovetheoverallsafetyofruralhouseholds[14].
Biogasenergyisgeneratedthroughanaerobicdiges-tion.
Itcontainsmainlymethane(50–70%)whiletherestismostlycarbondioxideandasmallamountofothergases[15].
Anaerobicdigestionconvertshumanexcreta,animaldungandotheragriculturalresiduesintoacleanandenvironmentallyfriendlyenergycommodity.
Biogashasalsobeenrecognizedasatechnologywiththepoten-tialforvastenvironmental,economic,andhealthbene-fits[16].
Regardingtheenvironmentalbenefits,anaerobicdigestioncansignificantlylowergreenhousegasemissionsfrommanureanddirectcombustionofsolidfuelwood.
Inadditiontothis,bysubstitutingthesolidfuelscommonlyusedforcookingindevelopingcountries,suchaswoodandcharcoal,alleviatespressureontheforests[17].
Furthermore,usingbiogasenergyasasubstituteforfossilfuelscansignificantlyreducetheamountofgreenhousegasemissions.
Italsosavessub-stantialtimebyreducingfuelwoodcollectionandcook-ingtimes[18].
Thetechnologycanalsooffersubstantialeconomicbenefitsespeciallytowomen,whoaretheprimevictimsofdirtyfueluse[19].
Apartfromthepro-ductionofbiogas(methane),anaerobicdigestiontrans-formstheaddedfeedstockintoabio-slurrythatcanbeusedasanorganicfertilizerandsubstitutechemicalfertilizerforcropproduction.
Itis,therefore,apparentthatbiogastechnologyessentiallymeetsmostofthekeyrequirementsforaddressingtheenergyaccessandenvir-onmentalproblems.
ItalsoprovidessomeeconomicKelebeEnergy,SustainabilityandSociety(2018)8:30Page2of14gains.
Biogastechnologycanalsobeappliedwherevertherearesufficientorganicandlocallyavailablemate-rials.
However,theconcernofmanystakeholdersofthebiogasprogramcannotbeneglected,whoaskwhythediffusionofthetechnologyremainslowandabandonedinmanypartsofEthiopiadespitetheinternationalandnationaleffortstopromotethetechnologyinthatplace.
Manystudieshavebeenconducteddealingwiththebenefitsandbarriersofbiogastechnologyinsomere-gionsofEthiopia.
Regardingitspotential,forinstance,KampandForn[20]statedthatthephysicalgeographyofmanypartsofEthiopiacomplieswiththetechnicalcriteriaoftheoperationofbiogasplantsintermsoftemperatureandavailabilityofwasteorganicmatter.
Similarly,theavailabilityofcheapfeedstocksfromlive-stockandagriculturalresiduesarereportedtobethecountry'sfuturepotentialforinstallingsmall-scalebiogastechnology[21].
Onthecontrary,someotherliteraturedatashowthatsocio-economicattributes,demography,technicalchallenges,andinstitutionalbarriersarethemajorchallengesfacingbiogastechnologyinEthiopia[20,22,23].
Besides,lackofproperlyeducatedpersonnel,inadequateaccesstobiogasappliancesandaccessories,poorprivatesectorparticipation,inadequatemaintenanceandrepairservices,andpoorqualityofdi-gestersarealsofoundtobeseriousbottlenecksthatin-hibitthediffusionofthetechnologyineastAfricaandparticularlyinEthiopia,Rwanda,andUganda[24–28].
Ontheotherside,therearealsostudiesconductedintermsoftheincentivestowardsthepromotionofbiogastechnologyinsub-SaharanAfricaandinEthiopiainpar-ticular.
AccordingtoAmigunetal.
[29],biogasadoptersinEthiopiahavealreadystartedexperiencingthebenefitsoftheproject;suchastheuseofcleancookingfuelandincomesavingsmadeintermsoftimeandmoneytosearchforfuelandtopurchaseothertraditionalfuels(firewood,charcoal,andkerosene),therebymotivatingotherpotentialbiogasuserstoadopt.
Inlightofsuchbenefits,thispaperasksthecriticalquestionofwhythewidespreaddisseminationofthistechnologyhasbeenprevented,asthepreviousstudiesintheTigrairegiondidnotfullyaddresswhetherornottheintendedobjectivesofthedomesticbiogasprogramofEthiopiahavebeenactualizedbytheparticipants.
Theaimofthispaper,whichfocusesonsmallholderfarmersinNorthernEthiopia,isthereforetoexaminetheimpactofthedomesticbiogasprogramonthethreemainout-comes:whethertheaccesstoadomesticbiogasplantleadstoreductionsinenergy-relatedexpenditure,whetheritaffectedthecropyieldandsubstitutionofchemicalfertilizer,andwhatarethechallengesfacingthealreadyinstalledbiogasplantsandthefuturepoten-tialfortheextensionofthedomesticbiogastechnologyintheTigrairegion.
TheoreticalframeworkThebasictheoreticalframeworkunderlyingthisstudyevolvesfromthetheoryofenergystacking,particularlytransitionandmultipleusesofenergysources.
Accordingtotheexistingliterature,therearetwowell-establishedandofcoursecontradictingviewstobefoundinenergytransitionmodelsonhowhouseholdsmovetowardstheuseofmodernfuels.
Theseincludeenergyladderanden-ergystackinghypotheses[30,31].
Theformeroneisbuiltontheideathatmodernfuelsareconsideredtohavemoreadvantagesthanthetraditionalfuelsinmanystandards,andarethusconsideredtobehigherrungsontheladder.
Themainargumentofthistheoryisthathouseholdsswitchfromtraditionalfuelstotransitionfuels(suchascharcoal,kerosene,andbio-fuels),andlaterontomodernfuels(suchasliquefiedpetroleumgas(LPG)andelectri-city)asaresultofariseinincome.
Inshort,themodelhy-pothesizesthathouseholdsmovealongtheenergyladderastheirincomeincreases.
Morerecently,however,variousstudieshavereportedanumberofpitfallsespeciallyintheapplicabilityofthetheoryoftheenergyladderinde-velopingcountriesandinparticularinaruralsetting.
Odihi[32],forinstance,hasdiscussedthechallengeswithregardtothepracticabilityofthismodelinde-velopingcountriesfortheobviousreasonsthatthepresenceofbothinadequatefueldistributionanden-ergyfacilitiesarebeyondthereachofmanyhouse-holdsregardlessoftheirlevelofincome.
Inreality,indevelopingcountriesparticularlyinruralareas,householdsdonotlinearlyswitchtomodernfuelswithariseinincomesincethechoiceoffuelsisnotde-terminedsolelybydisposableincome[33,34].
Accord-ingtotheenergystackingmodel,householdsmaydevelopastackingbehaviorsothattheycanusemorethanonefueltypesimultaneouslyinsteadofsimplysub-stitutingtheearlierones.
Besides,theenergyladderthe-oryhasbeencontestedinvariousliteraturesmainlyforthefollowingreasons.
Thefirstreason,asthemultiplefuelusebehaviorofhouseholdsisnotconsideredintheenergyladdermodel.
Indevelopingcountries,becauseofanunreliablesupplyofmodernenergy,householdspre-fertouseamixofenergytobeonthesafesideduringthetimeswhenprimaryenergysourcesarenoteasilyavailable.
Secondly,themulti-purposenatureofvariousenergysourcesisalsoanimportantconceptthatdeter-minesthedecisionofhouseholdstowardsfuelprefer-ence.
Thisfactorhasalsobeenoverlookedbytheexistingenergytransitionconcepts.
Nevertheless,theen-ergystackingmodelhasbeenreportedtobeamoreac-ceptabletheoreticalframeworktoexplaintheadoptionbehaviorofhouseholdsindevelopingcountries[34–37].
Therearesomeenergysourceswhichmayhaveimport-antcontributionsnotonlyinsolvingtheenergyproblembutalsoinplayingapivotalroleinothersectors.
ForKelebeEnergy,SustainabilityandSociety(2018)8:30Page3of14instance,theby-productsofsomeofthebiofuelsareusefulforagriculture(soilfertilityenhancementandfor-ageforlivestock).
Theexistingenergytransitionmodelsdonottakeintoconsiderationsuchmultipleservicesofagivenenergysourcewhenexplainingthebehaviorofhouseholdstowardsthepreferencesoffuels.
Inthispaper,theresearchfocusisontheconceptofenergytransitionconstraintsandmultipleusesofenergysources,whichareconsideredtobeimportantvariablesthatexplainthehouseholdbehaviortowardstheuseoffuelsamongasetofenergyoptions.
Thestudyaddressesthekeyconstraintsandprospectsoftransitiontowardsbiofuelsandhowthemulti-purposenatureofbiofuelsdeterminesthepreferenceofhouseholdstowardsvariousenergyoptionsbytakingfamily-sizedbiogasdigestersasacasestudy,asitsenergytechnologyproducesbiogasenergy(methane)andorganicfertilizer(bio-slurry)whichisusefulforenhancingcropproductionbysubsti-tutingchemicalfertilizer.
MethodsStudysitesThestudywasconductedinthreerandomlyselecteddis-trictsoftheTigrairegion.
TheseareOfla,Hintalo-Wajerat,andEnderta,wheredomesticbiogastechnologyhasre-centlybeenintroducedbytheNationalDomesticBiogasProgrammeofEthiopia.
Thestudyareasarespatiallydis-tributedacrossthreedistrictstocaptureheterogeneousdataonsocio-economicattributes,energyconsumptionpatternsandbiomassenergypotentials.
Thestudysitesarealsocharacterizedbyvariousclimaticandtopographicaldomainsrangingfromaltitudedifferencestotemperatureandrainfallvariationsaswellasendowmentofbiomassenergysources.
Thefarmingsystem,whichwasobservedtobeamixoflivestockandcropproductioninallstudysites,isalsoamongthesourcesoftraditionalenergy.
Theenergyconsumptionpatternacrossthethreestudysitesisobservedtobefairlysimilarwhichisinfactdominatedbybiomassenergy.
Sampledesign,procedures,anddatacollectionThestudyareaswereselectedusingmulti-stagesam-plingtechniques.
Inthefirststageofthesamplingpro-cedure,thethreedistrictswererandomlyselected.
Thenafter,basedonthenumberofdomesticbiogasplantsin-stalled,twohigh-achieving"tabias"1fromeachdistrictwerepurposivelychosenwithasupportofexpertsfromtheofficeofminingandenergyofthestudydistricts.
Thesamplingframeforthisstudywashouseholdswhousetheendproductsofdomesticbiogastechnology(methaneandbio-slurry)forfuelandfertilizerpurposes.
Asimplerandomsamplingtechniquewasthenappliedtoselecttherespondentsfromthelistofbiogasuserhouseholds(hereafterreferredastreatedobservations)andnon-biogasuserhouseholds(hereafterreferredtoascontrolobservations)ofeachselected"tabia.
"Thisstudyusedacross-sectionalsurveyof400ran-domlydrawnhouseholds,bothtreatedandcontrolobser-vationscomprisedof200each,from3districtsand6tabiascarriedoutbetweenFebruaryandApril,2016.
Thesampleforthetreatedobservationswasdrawnfromasetof1887households,whichintroducedafamily-sizedbio-gasplantinthethreedistrictsasofDecember,2015.
Anattemptwasmadetoincludedigesterswhoseconstructionhadbeencompletedatleast6monthspriortothesurveywithanintentionthatthistimelagprovidedadequatetimeforhouseholdstodeveloptheexperienceneededtooperateadigesterandatthesametimeexperiencethebenefitsofowningasmall-sizedbiogasplant.
Themajorityofthebiogasusers(1061)werefromtheHintalo-Wajeratdistrict.
TheOflaandEndertadistrictsalsohad516and310biogasusers,respectively,duringthesurvey.
FollowingWatson[38],thisstudyadoptsEq.
1tocalculatetherepresentativesamplesizefromthetargetpopulation.
Thedistributionofthesamplesizeacrossthedistrictswasbasedontheirrelativeshareofthebiogasuserstothetotalsamplingframe(targetpopulation)asshowninTable1.
np1pe2Z2p1pN1wheren=samplesize.
N=targetpopulation(1887).
e=precisionlevel(0.
065).
Z=1.
96,confidencelevelat95%.
P=0.
5,estimatedpopulationproportionn0:510:50:06521:9620:510:51887n200Therequireddatawerecollectedfromtheselectedheadsofhouseholdsusingstructuredquestionnaires.
Focusgroupdiscussions,keyinformantinterviews,andfieldobservationswerealsousedtovalidatethehouse-holdsurveyandtoacquirein-depthqualitativedata.
ATable1SamplesizefromeachstudysiteStudysiteTargetpopulationSamplesizeBiogasusers(treatment)Non-biogasusers(control)TotalOfla5165555110Hintalo-Wajerat1061112112224Enderta310333366Total1887200200400KelebeEnergy,SustainabilityandSociety(2018)8:30Page4of14pre-testedquestionnairewasdeployedtogatherthedatawithregardtoawiderangeofsocio-economicaspectsandhouseholddemographics,occupation,education,cookingbehavior,energy-relatedexpenses,andfueluse.
Inaddition,thequestionnairecontainedasectionaboutthereasonsfor(not)adoptingbiogas,thesourceoffundsforthedigesterandfollowupandtechnicalsup-portsbytheNationalBiogasProgrammeofEthiopia.
Furthermore,qualitativedataonchallengesandoppor-tunitiesofthebiogassectorwereacquiredusingfocusgroupdiscussionsandkeyinformantinterviews.
Thesecondarydatawerecollectedfrompublishedarticlesandunpublishedgovernmentalreports;inparticular,re-portsoftheNationalBiogasProgrammeofEthiopia,theTigraiRegionalBiogasProgrammeCoordinationOfficeandtheCentralStatisticalAgencyofEthiopia.
DataanalysisToanalyzethetrends,impedimentsandprospectsofthebiogassector,acontentanalysiswasused.
Descrip-tivestatisticssuchasmeasuresofcentraltendencyanddispersionswereemployed.
Statisticaltests(mainlyttests)werealsodeployedtodeterminethedifferencesbetweentreatedandcontrolobservationsinregardtovarioussocio-economicattributes.
Inordertoanalyzetheimpactofthebiogastechnologyinterventiononen-ergyexpenditure,cropyieldanduptakeofchemicalfertilizer,propensityscorematchingwasdeployedtore-ducethepossiblesamplingbiasastheparticipationinthedomesticbiogasprogramisnotrandom.
Propensityscorematchingmodel(PSM)Therearetwomainconcernswithregardtothepar-ticipationinabiogasprograminrelationtoemploy-ingPSMfortheanalysisinthisstudy.
First,thebiogasinitiativeisvoluntaryandhouseholdsneedtoapplyforabiogasplant.
Second,conditionalonappli-cation,programbeneficiariesarenotselectedatran-dombutneedtofulfilltheeligibilityconditionssuchasownershipofatleastfourcattle(localbread)toensureadequatecattledungforanaerobicdigestionandanadequatespaceforthebiogasdigestertanktobebuilt.
Duetothesetworeasons,self-selectiontoparticipateintheprogramandtheimpositionofeligi-bilityconditions,itismorelikelythatthosewhoapplyandobtainabiogasplantaresystematicallydif-ferentfromthosewhodonot.
Hence,comparisonbe-tweenhouseholdswhohaveabiogasplantandthosewhodonot,withoutaccountingforpotentialdiffer-encesinfactorsthatdetermineselectionintothepro-gramaremorelikelytoyieldincredibleestimates.
Tocapturesuchaproblemofbiasedness,householdsthathaveparticipatedinthenationaldomesticbiogaspro-gramofEthiopiawerebasicallycomparedtothosethathavenotyetparticipatedinemployingthepropensityscorematchingmodel.
Thetreatmentinthiscaseispar-ticipatinginthedomesticbiogasprogramwheretheout-comeswerechangeinenergyexpenditure,uptakeofchemicalfertilizerandcropyield.
Thestudypassedthroughtwostepstoanalyzetheimpactofthedomesticbiogasinitiativeontheoutcomevariables.
Initially,follow-ingBecherandIchino[39],theprobabilityofinstallingadomesticbiogasplant,alsoknownasthepropensityscore,forthetreatedandcontrolobservationswasestimatedbymeansofselectionEq.
2thatusesabinarylogitmodel(Table5).
ThefulllistsofexplanatoryvariablesincludedinthisstudyarepresentedinTable2.
Thesecondstepwascomputingtheaveragetreatmenteffectontreated(ATT)overtheoutcomeofEq.
5;(wheretheATTistheaverageeffectofthetreatmentforcasesthataretreatedandmustaverageovertheoutcomesoftreatmentforthetreatedobservations(Y1|T=1)presentedinEq.
5.
ThismeansthatATTistheaveragedifferenceinenergyex-penditure,cropyield,anduptakeofchemicalfertilizerbe-tweenhouseholdswithandwithoutbiogasenergyaftermatching(Tables6and7).
Thiswasachievedbymatchingbiogasuserandnon-userhouseholdsaccordingtotheirpropensityscoreusingthenearestneighbor,radius,kernel,andstratificationmatchingmethodsassuggestedbyBeckerandIchino[39].
TreatmentDisabinaryvariablethatdeterminesifthehouseholdusesbiogastechnologyornot,D=1fortheusersandD=0otherwise.
Xidenotesthepre-treatmentcharacteristics(charac-teristicsofhouseholdsthatmightaffecttheadoptionde-cisionofbiogastechnology).
PXiprobD1=XiED=Xi2Eq.
2indicatesthattheprobabilityofadoptiondeci-sionofhouseholdstowardsbiogastechnologyiscondi-tionaltothepre-treatmentcharacteristicsofhouseholds.
yy1ifD1y0ifD03InEq.
3,Ydenotesthetreatmenteffects(impactofadoptingbiogastechnologyonenergyexpenditure,cropyield,andutilizationofchemicalfertilizer).
Inordertoknowwhatwouldhavehappenedtotheoutcomevari-ables(energyexpenditure,cropyield,anduptakeofchemicalfertilizer)hadthehouseholdsnotusedbiogasenergyandbio-slurry,theoutcomeYamongthepartici-pants(Y1)andnon-participants(Y0)aftermatchingoughttobecompared.
Averagetreatmenteffect(ATE):TheATEshowsthedifferencebetweentheaverageenergyconsumption,cropKelebeEnergy,SustainabilityandSociety(2018)8:30Page5of14yield,andchemicalfertilizeramongthebiogasuserandnon-userhouseholdswithoutmatchingasshowninEq.
4.
Δy1y0ATEEΔEy1jx;D1Ey0jx;D04Equation4maybebiasedincasethetreatedandcon-trolvariablesarenotsimilar,whichisobviousinobser-vationalstudiesincontrasttoexperimentalstudies.
Toovercomethisproblem,itisrecommendedtousetheaveragetreatmenteffectonthetreatedcases(Eq.
5).
Averagetreatmenteffectonthetreated(ATT):Eq.
5isacounterfactualsituationwhichcomparestheaverageenergyexpenditure,cropyield,anduptakeofchemicalfertilizerofthebiogasadopterandnon-adopterhouse-holdsaftermatchingbasedontheirpropensityscorestoadoptbiogasenergytechnology.
ATTEΔjpx;D1Ey1jpx;D1Ey0jpx;D05ResultsanddiscussionDescriptionofthesampledhouseholdsTable3summarizesthesocio-economicanddemo-graphicattributesofsampledhouseholds.
Thereisasig-nificantdifferencebetweenthebiogasuserandnon-userhouseholdsinmanyofthesocio-economicalanddemo-graphicalvariablesthatareincludedinthisstudy.
Forinstance,theaverageage,levelofeducation,familysize,farmsize,andannualincomeofthetreatedcases(biogasusers)werefoundtobesignificantlyhighercomparedtothatofthecomparisonobservationsasshowninTable3.
Morespecifically,householdswhoadoptedbiogastech-nologyarefoundtobeolderthantheirnon-adoptercounterparts.
Thisgivestheimpressionthatolderhouseholdstendmoretousebetterenergysourcessuchasbiogasenergyduetothepossibilityofabetterwealthaccumulationcomparedtotheyoungsters.
Theprofileofthehouseholdsalsoindicatesthatthebiogasuserhouseholdswerefoundtohavehighereducationalat-tainmentsthanthatofnon-users,whichimplieseduca-tionisakeyelementformoderntechnologyadoptionanduse.
Besides,theaveragefarmsizeofbiogasusersandnon-userswas2.
5and2tsimad2respectivelywithasignificantdifferencebetweenthetwogroups.
Similarly,biogasuserswerefoundtohavehigherannualincomeandfamilysizethanthatofnon-userhouseholdswhichhighlightsthathigherincomemaybeassociatedwiththeutilizationofbetterenergyfacilities.
Thedescriptivestatisticsofthisstudyconfirmsthathouseholdsthathavealreadyadoptedbiogastechnologyhavehigherin-comesthanthatofnon-adopters(Table3).
Thecoeffi-cientofbinarylogitregression(Table5)alsoconfirmsapositiveandsignificantrelationshipbetweenthetwovariables.
Thisimpliesthatariseinincomeofhouse-holdsmaycauseapartialshifttorelativelybetterenergysourcessuchasbiogastechnology.
Ontheotherhand,ahouseholds'incomerisesasaresultofreductioninen-ergyexpenditure.
Therefore,abi-directionalrelationshipbetweenincomeandbiogasadoptionisevident.
Table2DescriptionoftheindependentvariablesusedtoexplaintheprobabilityofadoptingbiogastechnologyNameofthevariableNatureofthevariableHypothesizedrelationshipwiththedependentvariable(biogasadoption)DescriptionofthevariableAgeContinuousPositive/negativeAgeofthehouseholdheadinyearsSexDummyPositive/negativeSexofthehouseholdhead;adummyvariableforgenderrelationships(male=1,female=0)FamilysizeContinuousPositive/negativeFamilysizeofthehouseholdEducationContinuousPositiveEducationlevelofthehouseholdheadinyearsCattleholdingContinuousPositiveNumberofcattleownedbythehousehold(heads/hh)AnnualincomeContinuousPositiveAnnualincomeofthehouseholdinETBDistFireContinuousPositiveDistancetonearestfirewoodcollectionsiteinkilometerDistWaterContinuousNegativeDistancetonearestpermanentwaterpointinkilometerDistMarketContinuousPositive/negativeDistancetonearestmarketinkilometerAvailabilityofelectricityDummyNegativeAvailabilityofmodernfuelsmainlyelectricity(yes=1,otherwise=0)FarmsizeContinuousPositiveTotalsizeoffarmplotsownedandoperatedbythehouseholdinTsimadFertilitystatusCategoricalPositive/negativeFertilitystatusoffarmplot(1=poor,2=medium,3=good)FarmlocationContinuousNegativeDistancebetweenhouseandfarmofthehouseholdinkilometerExtensionserviceContinuousPositiveFrequencyofcontactsbetweenagriculturalextensionworkerandthehousehold(frequencyinayear)KelebeEnergy,SustainabilityandSociety(2018)8:30Page6of14Thestudyshowsthattherewerenostatisticallysignifi-cantdifferencesobservedinthecattleholdingbetweenthetwoobservationssignalingthatavailabilityoffeedstockisnolongerachallengeforabiogasadoptiondecisionatthestudysitessincetheaveragecattleholdingforbothobservedcaseswas5headswhichisquitehigherthantheminimumheadsofcattlerequiredtooperatea6m3biogasdigester(accordingtoNationalBiogasProgrammeofEthiopia,aminimumof4headsofcattleisrequiredinthecontextoftheruralpartofthecountry.
ChallengesfacingthebiogastechnologyandfutureprospectsThehouseholdsurveyshowsthatinadequateenergy(methane)production,frequentdamageofinstalleddi-gestersandinadequateinstitutionalsupportarethemajorchallengeshamperingthesmoothoperationofbiogasplantswhichaccountfor32%,31%,and22%ofthetotalbiogasuserrespondents,respectively(Table4).
Thesefiguresimplythataconsiderablenumberofbio-gasdigesterownersfacetechnical-relatedchallenges,asalowlevelofenergyproductionanddamageofthebio-gassystemusuallyinducedbytechnicalrelatedfaults.
ThereportoftheNationalBiogasProgrammeofEthiopia[40]alsoshowsthattheuptakeofbiogastech-nologyislaggingbehindthetargetwhichstrengthensthefindingsofthehouseholdsurvey(Fig.
1).
Despitetheplantoinstall15,100domesticdigestersinfourregionalstatesofEthiopiafrom2008to2014,only63%oftheplanwasachieved.
Similarly,intheTigrairegionalone,wherethisstudywasconducted,3873domesticbiogasdigestershavebeenbuiltcomparedtotheplanned5288digesters,whichis73%ofthatwhichwastargetedtobeinstalled.
Therefore,theuptakeofbiogasdiffusionoverthepastyearsseemstohaveexperiencedirregularitiesattheregional(Tigrai)anddistrictlevels.
Thisreportmayalsobeconsideredasanindicatorthatthetechnologyhasbeenhurdledbytheabovestatedbarriers.
Figure1showsthatduringtheearlyperiodsofthebiogasinitia-tive,theuptakeincreasedandreacheditspeakin2013.
Sincethen,however,itfacesstagnationandinfactslo-weddowninsomeofthestudysites.
Thiscouldalsobeconsideredasanindicatorofthetechnicalchallengesthatfacestheinstalleddigesters.
Besides,keyinformantsfrequentlyreportedthatbadhabitssuchasirregularorinsufficientfeedingofthebio-digestersignificantlyhin-derbiogasproductionandeventuallystopworking.
Thepresenceofsuchnon-operatingdigestersinneighbor-hoodsdefinitelyinfluencedthepromotionofthetech-nologyduetospillovereffectsasmanypeoplearemorecuriousaboutbadstoriesthansuccessstoriesofanewtechnology.
AstudybyParawira[8]supportsthefind-ingsofthecurrentstudybydisclosingthatlowperform-anceandpoorqualityofinstalledplantscontributedtothedis-adoptionofbiogasdigestersinsub-SaharanAfrica.
Moreover,thecurrentfindingscomplywithEshetieetal.
[21]whoreportedthatthemajorTable3Meanvalueofbasicsocio-economicanddemographicvariablesofrespondents(standarddeviationinparentheses)VariablesTreatedobservations(n=200)Controlobservations(n=200)Totalsample(n=400)PvalueSexofthehouseholdhead(female=0,male=1)0.
86(0.
34)0.
89(0.
31)0.
87(0.
33)–Ageofthehouseholdheadinyears47(9.
18)45(10.
3)46(9.
8)0.
03Educationlevelofthehouseholdhead(yearsofschooling)2.
5(2.
7)1.
5(2.
4)2(2.
64)0.
000Householdsize6.
3(1.
68)5.
7(1.
77)6(1.
75)0.
001Farmsizeintsimad2.
5(1.
32)2.
07(1.
57)2.
3(1.
47)0.
000Cattleholdinginheads5(2.
73)5(3.
24)5(2.
99)0.
32AnnualincomeinETB18,949.
78(12910)14,175.
5(8287.
5)16,562.
6(11095)0.
000Table4MajorchallengesandfutureprospectstowardsthetransitionofdomesticbiogasenergyVariablesPercent*Challengesfacinginstalleddigesters(n=200)Lowenergyproduction32%Damageofinstalleddigesters31%Inadequateinstitutionalsupport22%Shortageofmanure15%Reasonsfornotadoptingbiogastechnology(n=200)Lackoffeedstock13%Highcostofconstruction24%Nocreditaccess13.
8%Spillovereffectoffaileddigesters52.
3%Nospacefordigesterpitpreparation48.
5%Waterproblem37.
6%Limitedknowhow14.
2%Favorableconditionsforwiderpromotionofbiogastechnology(n=400)Availabilityofcheapfeedstocks39%Existenceofsubsidyforthetechnology25.
5%Multifacetedbenefitsofthetechnology39.
9%Scarcityofsolidfuels44.
5%Increasethepriceofsolidandfossilfuels36.
2%*Multipleresponsesispossible,nstandsfornumberofrespondentsKelebeEnergy,SustainabilityandSociety(2018)8:30Page7of14bottlenecksfacingtheextensionofthebiogastechnol-ogyincludetechnicalproblems,abandonment,andlossofinterest.
Regardingthereasonsfornotadoptingbiogastechnol-ogy,thesurveyednon-biogasadoptersrespondedthatthespillovereffectoffaileddigesters(52.
3%),inadequatespaceforpitpreparation(48.
5%),andwaterproblems(37.
6%)constitutedthecoreissues(Table4).
Itwasalsoobservedduringthefieldsurveythatasubstantialnumberofdigesterswerenotoperatingatallstudysites.
Thismighthavecontributedtothesluggishbehaviorofmanyeligiblehouseholdsfornotparticipatinginthedomesticbiogasprogram.
Lackofapermanentwatersupplyinthenearbyareawasalsoreportedtobeachallengeforpoten-tialadopters.
Anaerobicdigestionnormallyconsumesaconsiderableamountofwater,whichisaproportionequaltotheamountofmanuretobeloadedintothedigester.
Itis,therefore,unlikelyforhouseholdstoadoptbiogasen-ergywithoutensuringapermanentwatersupplywithinareasonabledistance,accordingtotheNationalBiogasProgrammeofEthiopiaatmost30minawayfromtheresidence.
Thekeyinformantsvalidatedtheresultsofthehouseholdsurveybydisclosingthatthesuitabilityofasiteandtheavailabilityofspacelimittheuptakeofbiogastechnologybyhouseholds.
Insomelocations,becauseoftherockynatureofthesurface,itisdifficultormorelabor-demandingandexpensivetodigapitforthedi-gester;consequentlyhouseholdsarereluctanttoadoptthetechnology.
Theparticipantsoffocusgroupdiscussionalsounderlinedthatthespillovereffectoffaileddigesters,inadequatetrainingandpoorfollowupoftechniciansandinadequatemaintenanceserviceshavepreventedwide-spreaddisseminationofthetechnology.
Similarresultshavebeenreportedregardingbarrierstothelarge-scaleadoptionofdigestersindifferentsub-SaharanAfricancountries.
Forinstance,inTanzania,inadequatewateravailability,poorperformanceofdigestersandpoorfollowupwerereportedtobemajorchallengesforthewide-spreaduseofbiogastechnology[24,26].
Similarchal-lengesonasmallerscalearealsoreportedfromothersub-SaharanAfricanandAsiancountries[41–46].
Lookingatthefutureprospectsofbiogastechnology,thesurveyedhouseholdsstatedthatthepresenceofscar-cityofsolidfuels(44.
5%),themultipleuseofbiogas(40%),andtheavailabilityofcheapfeedstocks(39%)arethefavorableconditionsandpressingfactorsforthefuturepromotionofthesector(Table4).
Equallyimportant,theexistenceofgovernmentsubsidyforthetechnologyandtheeverrisingpriceofbothsolidbiomassandmodernen-ergysourceswerealsoconsideredbytherespondentsasanopportunityforthefuturepromotionofthetechnol-ogy.
Fortoomanypeople,thescarcityofsolidfuels,de-pendenceontoofewforestedareas,alongwiththelargenumberofhouseholdswithindoorandoutdoorfedcattlewouldhelptomakebiogasasuitableandaccessibletech-nologyforsmallholderfarmhouseholds.
Theresultofthedescriptivestatisticsalsoshowsthathouseholdsthatadoptedbiogastechnologyarespatiallylocatedfarawayfromthenearestfirewoodcollectionsiteascomparedtothenon-adopters.
Biogasusershavetospendonaverage5h(roundtrip)fromtheirhousetothefuelwoodcollec-tionsiteandthenon-adopters4h.
Thissignalsthattheunavailabilityoffuelwoods(forestsandwoodlots)inanearbyareacompelsfarmerstolookintootheralternativeenergysourcessuchasbiogasenergyinsteadoffullyrely-ingonscarcesolidbiomassenergysources.
Fig.
1UptakeofbiogastechnologyinTigrairegionandstudydistrictsKelebeEnergy,SustainabilityandSociety(2018)8:30Page8of14AsshowninTable4,theavailabilityofcheapfeed-stockwasmentionedasoneofthefavorableconditionsforthefurtherpromotionofbiogastechnologyby39%ofthesurveyedhouseholds.
Thiscouldprobablybeduetothefactthattheaveragecattleholdingofthesurveyedhouseholdsisfoundtobefiveheadsforbothbiogasadoptersandnon-adopterswhichisslightlyhigherthantheminimumheadofcattlerequiredtooperatea6m3biogasdigester,fourheadsofcattleaccordingtonationalbiogasprogramofEthiopia.
Hence,thepresenceofcheapandlocallyavailablefeedstock(cattlemanure)whichisassociatedwithrelativelylargercattleholdingwouldmakethepromotionanddiffusionofbiogastech-nologymorepromising.
AreportbytheCSA[47]inthisregardalsoshowsthatthetotalestimatedcattleintheTigrairegionisnearly4.
6million,andoutofthisabout3.
8millionareaged2yearsandolder.
Theregionhas,therefore,anuntappedpotentialforbiogastechnologysincecattledunghasbeenusedasthemajorsourceoffeedstockforanaerobicdigestion.
Thebiogasdigestersinthestudyareasaremainlyloadedwithcattlemanure,humanexcreta,andwater.
Besides,stricttreecuttingmonitoringandzerograzingpoliciesinthecountrycouldindirectlyassistbiogaspromotion.
Paralleltothefindingsofthecurrentstudy,KampandForn[20]assertthatascarcityoffirewood,deforestation,depletionofsoilnutri-ents,anderosionarethedriversformorebiogastechnol-ogyinthefuture.
Moreover,suitableagro-ecologyandwidespreadrearingoflivestockarereportedtobeamongthefavorableconditionsforbiogastechnologydissemin-ationineasternAfrica[27,45].
Thepressingfactors,suchastheincreaseinthepricesoffossilfuels,woodfuels,andfertilizersinsub-SaharanAfricawouldalsomakeforabrighterfutureforbiogastechnologypromotioninthere-gion[27,48],whichisinagreementwiththefindingsofthecurrentstudy.
EconomicbenefitsofthedomesticbiogastechnologyTables6and7presentasummaryoftheoutcomesofthepropensityscorematchingusingthefourmatchingalgorithms.
Itincludesthenearestneighbor,radius,ker-nel,andstratification.
Thispaperadoptsthefourmatch-ingmethodsforthereasonthatanycomparisonstudyisfreetouseanyofthematchingalgorithms,andnoneofthemissuperiortotheothers,buttheirjointconsider-ationprovidesawaytoassesstherobustnessoftheesti-matesoftheoutcomevariables[39].
Table5showstheestimatedcoefficientsofthepro-pensityscore,whichareusedasapre-requisitefortheestimationoftheoutcomevariables.
Thediagnos-tictestconfirmstheoverallfitnessofthemodelasProb>chi2=0.
000.
Theageofthehouseholdhead,thesexofthehouseholdhead,theeducationlevelofthehouseholdhead,theincome,thehouseholdsize,theavailabilityofsolidfuels,andelectricityarefoundtobethekeyfactorsaffectingtheprobabilityofadoptingbiogastechnology(Table5).
Householdheadsthatareolderandwithrelativelyhigherincomewerefoundtobemoreinterestedininstallingthebiogastechnology.
Thisisprobablyduetothepossibilityofabetterwealthaccumulationaspeoplegetolder,andtherebycanaffordtoinstallabiogasdigester.
Femalesweremorelikelytoadoptbiogascomparedtotheirmalecounterparts.
Thereasonwhywomenaremoreinter-estedintheadoptionofbiogastechnologycouldbeduetothefactthatwomenaremoreresponsibleforcol-lectingfirewoodandarealsotheprimevictimsofindoorairpollutioninthekitchen.
Householdswhodonothavesolidfuelsourcesinnearbyareaswerefoundtobemoremotivatedtoadoptabiogasdigester.
Besides,householdswhouseelectricitywerealsofoundtobemoreinterestedinadoptingbiogastechnologycomparedtothosewhodonot.
Thereasonforthecomplementaritybetweenelectri-cityandbiogasenergymayariseduetoalowdisposablein-comeofruralhouseholdsingeneral.
Asaresult,theymaychoosetouseelectricityforonlylightingpurposesandtherelativelycheaperbiogasenergyforcookingandboiling.
Table6presentstheeffectofbiogasenergyutilizationonenergyexpenditureusingfourmatchingmethods.
Theresultsvaryasthematchingalgorithmchanges,al-thoughallmethodsreachedthesameconclusionregard-ingtheimpactofbiogasenergytechnologyonreducingenergyexpenditureofruralhouseholds.
Thisisbecausedifferentmatchingmethodsemploydifferentprinciplesandwaysofcomputingtheaveragetreatmenteffects.
Forinstance,usingthenearestneighbormethod,200treatedobservationswerematchedto93comparisonob-servations.
Whereas,inbothradiusandkernelmethods,200comparisonobservationswerematchedto200treatedobservationswhichisonetoone.
Similarly,199controlobservationswerematchedto200treatedobser-vationsusingastratificationmatchingmethod(Table6).
Despitethevariationinnumericalvalues,allmatch-ingmethodsconfirmthatthebiogastechnologyhassignificantlyinfluencedtheenergyexpenditureofsmallholderfarmers.
AsshowninTable6,theaveragemonthlyenergyexpenditureofbiogasadopterswaslessbyETB3108.
36,59,98,and82.
4thanthatofnon-adopters(Pchi2=0.
000likelihood=241.
58Table6EffectofbiogasenergyutilizationonenergyexpenditureofhouseholdsMatchingmethodTreatedobservationControlobservationEnergyexpenditure(ATT)tvalueNearestneighbor20093108.
35***4.
12Radius20020059***3.
42Kernel20020098.
2***4.
17Stratification20019982.
4***3.
6and*denotevaluesignificantat1%,5%,and10%respectivelyKelebeEnergy,SustainabilityandSociety(2018)8:30Page10of14energy[49],whichisroughlysimilartothefindingsofthecurrentstudy.
Likewise,thedomesticbiogasprogramhasresultedinareductionofhouseholds'energyexpenditureonaverageby45%inIndonesia[50]whichisslightlyhigherthanthefindingofthecurrentstudy.
Apartfromanalyzingtheimpactofthebiogasinitia-tiveonenergy-relatedexpenditures,thestudyfocusesonthesynergybetweenbiogastechnologyandagriculture.
Asthepotentialofthetargethouseholdsforfuturebio-gaspromotionisinruralareasinwhichagriculturalsec-torsremainsthesolesourceoflivelihood,thisstudytookacloserlookatthepossiblelinkagesbetweenagri-cultureandbiogasdigestersbycomputingtheeffectsofbio-slurryutilizationoncropyieldanddemandforchemicalfertilizer.
Thedominantcropsgrowninthestudysitesarecereals;mainlywheat,barely,teff,andmaize.
ThetypesofchemicalfertilizersthathavebeenutilizedbythefarmersareDAPandUREA.
Usingthefourmatchingmethodsstatedabove,thean-nualcropyieldofbiogasuserhouseholdswasfoundtobeonaveragehigherby1.
7,1.
4,1.
5,and1quintals/year/householdascomparedtonon-users,respectively,duetotheapplicationofabio-slurrytreatmentoncropfields.
Itisimportanttonotethatfieldtrialsarereportedtobeanap-propriatemethodologytocomparetheyielddifferencesofcropsasaresultofabio-slurryapplicationinsteadofapply-ingsuchanobservationalstudy.
However,fieldtrialscouldnotshowtheoverallimpactofabio-slurryapplicationonthecropyieldofparticipantsoftheinitiative(onacommu-nityandevenahouseholdlevel).
Insuchcases,animpactassessmentmethodologyismoreimportantthanfieldtrials,i.
e.
,thisanalysismethodis,therefore,theappropriatemethodforthecurrentstudy.
Nevertheless,thepapermaysufferfromsomelevelofbiassinceallfactorsthataffectcropproductioncouldnotbefullycontrolledinsuchanob-servationalstudyandmaythereforeinfluencetheaccuracyoftheabovestatedfindings.
Ontheotherhand,theannualuptakeofchemicalfertilizersofbiogasuserswasfoundtobeonaveragelessby0.
34,0.
22,0.
28,and0.
25quintal/householdcomparedtonon-userhouseholdsusingtheabovestatedmatchingmethodsinthatorder.
Unlikeenergyexpenditure,theeffectsofabio-slurryfertilizerapplicationonthecropyieldandsubstitutionofchemicalfertilizerarenotfullymaterialized.
Theproductivityeffectofthebio-slurryfertilizerwasfoundtobesignificant(P=0.
1)usingtheradiusandkernelmatchingmethods,whereastheresultsofnearestneigh-borandstratificationshownosignificantdifference.
Be-sides,therewasnosignificantdifferencetothechemicalfertilizeruptakeofbio-slurryuserandnon-userhouse-holdsusingallmatchingmethods,whichsignalsnosig-nificantsubstitutioneffectasshowninTable7.
Aconsiderablenumberofhouseholdswereobservedtohavealowlevelofunderstandingoftheimportanceandutilizationofbio-slurryasafertilizer.
Only20%ofthebiogasadopterswerefoundtobeusersofbio-slurryontheirplots.
Lackofadequateknowledgeandsocialtaboowereamongthefrequentlystatedreasonsfornotyetusingabio-slurrybytheremaining80%ofbiogasadopters.
Itwasobservedduringthesurveythatfarmersusuallydisposethebio-slurryintoanopenpitwithoutadequatecaretoprotectnutrientevaporation.
Thekeyin-formantsalsorevealedthattheapplicationofabio-slurryisoftendoneinaccuratelyandatthewrongtime.
Further-more,themasonsandthebiogasenergypromotionexpertsusuallytrainthebiogasusersonbio-slurryutilizationalthoughthefocusandexpertiseofthesepersonnelisnotrelatedtoagriculture.
Thisgivestheinsightthatbio-slurryutilizationispoorlytaughttobiogasusersbymasons,energypromotersandtechnicianswhichareinfactoutsidersintermsofthefieldofagriculture.
Thekeyinformantsfurtherstressedthatpoortech-nicalknowledge,lowawareness,andacceptanceofthistypeoffertilizerandpoorextensionsupportcoupledwithsometraditionaltaboosaretobeclaimedfortheinsignificantcontributionofbio-slurrytocropproduct-ivityandsubstitutionofchemicalfertilizer.
Besides,thefocusgroupdiscussantsunderlinedthatthenegativeconnotationattachedtothebio-slurry,asitisproducedfromcattledungandfaecalsludge,hindersitsrateofapplication.
Thesemaycontributetonotfullymaterial-izedbenefits.
Furthermore,thefactthattheBureauofAgricultureandRuralDevelopmentoftheregiondidnotplayanactiveroleintheimplementationofthedo-mesticbiogasprogramofthecountrymighthavealsocontributedtothetechnicalfaultsonthebio-slurryap-plicationandtheknowledgegaps.
Thismayhavealsoledtotheinsignificantcontributionofthebio-slurrytotheexistingcroppingsystem.
Previousstudiesreportedparallelfindingsinthisre-gard.
Inlinewiththecurrentfinding,inRwanda,forin-stance,thebenefitsofthenationaldomesticbiogasprogramincludemeetingalltheenergyneedsforcook-ingandreducingtheenergyexpenditureofhouseholds[49,51].
Inadditiontothis,Mwakaje[24]revealsthattheadoptionofbiogasenergyinTanzaniaandRwandahashelpedinempoweringthesocio-economicstatusparticularlybyenhancingtheincomeofhouseholdsandcreatingjobopportunities.
AnotherstudybyWarnarsandOppenoorth[52]indicatedthatusingbio-slurryleadstoahighercropyieldincrementdespiteitsprod-uctivityeffectvaryingfromcroptocrop.
Itis,however,importanttonotethattheresultsofthecurrentstudyshouldbecalibratedusingexperimentalstudies,suchasfieldtrials,astheestimatesfromsuchobservationalstudiesmaynotbeabletocontrolallun-observedbiaseswhichcouldaffecttherobustnessoftheestimatedresults.
KelebeEnergy,SustainabilityandSociety(2018)8:30Page11of14ConclusionsThecomparisonofenergyexpenditurebetweenbiogasuserandnon-userhouseholdsshowsasubstantialdiffer-ence.
Theaveragemonthlyenergyexpenditureofbiogasuserhouseholdshasbeenreducedby20–36%asaresultofpartiallyswitchingtobiogasenergyparticularlyforlightingandcookingpurposes.
Furthermore,thestudyfindstheexistenceofapositivecropyieldpremiumofroughlyabout1.
5quintal/year/householdasaresultofusingbio-slurryasafertilizerSuchareductioninenergyexpenditureandanincrementincropyieldhaveaposi-tivecontributiontoenhancetherealincomeofhouse-holds.
Thesefindingshaveimportantimplicationsonthefurtherpromotionoffamily-sizedbiogasdigesters.
Thismeansthatbiogastechnologyshouldnotonlybepromotedforthepurposeofsupplyingcleanenergybutalsoforfosteringtheincomeofruralhouseholdsbyre-ducingtheenergyexpenditureandenhancingcropproductivity.
Despitethis,theoveralleffectofabio--slurryapplicationoncropproductivityandsubstitutionofchemicalfertilizerwasnotasmuchasexpectedduetothepoormanagementandknowledgeinbio-slurryutilization.
Theinstalledbiogasunitsareconfrontedbyaninadequateenergyproduction,frequentdamage,andaninadequateinstitutionalsupportformaintenanceandrepairthathin-dersthetransitionfromsolidwoodfuelstobetterenergyfacilitiessuchasbiogas.
Thekeyfactorsthatlimittheex-tensionofthebiogastechnologytopotentialbiogasadoptersarethepresenceoffailedanddamageddigesters,aninadequateplotoflandfordigesterconstructionandthewateravailabilityproblem.
Inthefaceofsuchbarriers,therearestillenablingenvironmentsforthewidespreaduseofthetechnologysuchasascarcityofsolidfuels,ariseinpriceofmodernenergysources,theavailabilityofacheapinputforbiogasproduction,andmulti-faceteduseofthetechnology.
Theleadingagency,NationalBiogasProgrammeofEthiopia,whichisinchargeofbiogaspromotion,shouldensuretheactiveengagementofrelevantagenciessuchasenvironmentalprotection,naturalresourcesmanagement,agriculture,andhealthcareatadistrictandcommunitylevelsinordertoovercomethechallengesfacingthetech-nologyandtorealizeitsmultifacetedbenefits.
Theactorsinvolvedinthisbiogasprogramarealsoadvisedtoquicklyfocusonaddressingthetechnicalandattitudinalbarriershamperingbiogasenergyandbio-slurryutilizations.
Fur-therplotlevelandcrop-specificresearchworkisrecom-mendedtoexplorethecontributionofdomesticbiogastocropproductivityandclimatesmartagriculture.
Endnotes1A"tabia"inthispaperreferstothesmallestadminis-trationunitinTigrainexttoadistrict2Tsimadisalocalunstandardizedmeasurementofsizeoffarmplots(onetsimadisroughlyequivalentto0.
25ha)3EthiopianBirr(ETB),currencyofEthiopia(US$1=27.
2ETBasofDecember,2017exchangerate)AdditionalfileAdditionalfile1:Rawdatacollectedfromsurveyedhouseholdheads.
(XLSX91kb)AbbreviationsEq.
:Equation;ETB:Ethiopianbirr;hh:Household;UNDP:UnitedNationsDevelopmentProgramme;WHO:WordHealthOrganizationAcknowledgementsTheauthorisverygratefultotheMekelleUniversityandPanAfricanUniversityforfundingpartofthedatacollectioncosts.
Theauthorextendshisgratitudetotheenumeratorsandhouseholdswhoparticipatedinthisstudy.
Theauthoristhankfultotheanonymousreviewersandeditorofthejournalfortheirhelpfulandcriticalrecommendationstotheearlierversionofthispaper.
TheauthoralsoextendsappreciationtoMr.
HaftuKahsayforhisinvaluablecontributiontocorrectgrammaticalerrors.
FundingThefundfordatacollectionwasobtainedfromMekelleUniversityandPanAfricanUniversity.
AvailabilityofdataandmaterialsTherawdatahasbeensubmittedonlineasAdditionalfile1.
Authors'contributionsHEdevelopedtheconcept,designedthedatacollectioninstruments,andsuperviseddatacollection.
Inaddition,dataanalysisandtheinterpretationoftheresultsandwritingthismanuscriptwerecarriedoutbythesameauthor.
Theauthoralsoreadandapprovedthefinalmanuscript.
CompetinginterestsTheauthordeclaresthathehasnocompetinginterests.
Publisher'sNoteSpringerNatureremainsneutralwithregardtojurisdictionalclaimsinpublishedmapsandinstitutionalaffiliations.
Table7Effectofbio-slurryapplicationoncropyieldanduptakeofchemicalfertilizer(t-valueinparentheses)MatchingmethodTreatedobservationControlobservationCropyield(ATT)Chemicalfertilizeruptake(ATT)Nearestneighbor50251.
7(1.
5)0.
34(0.
6)Radius47711.
46(1.
87)*0.
22(1.
256)Kernel50711.
56(1.
9)*0.
28(1.
6)Stratification50711.
06(1.
24)0.
255(1.
96)*Denotesvaluessignificantat10%KelebeEnergy,SustainabilityandSociety(2018)8:30Page12of14Received:8February2018Accepted:12September2018References1.
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Synthesizingsmall-scalerenewablealternativeenergysources,suchasbiogasenergy,intotheenergymixhasbecomeanimportantstrategytoovercometheenergyhungerofitsruralresidents.
Aspartofthegovernmentpolicy,small-scalebiogasdigestershavebeeninstalledinselecteddistrictsandregionsofthecountrysince2007.
Thereis,however,limitedevidenceonwhetherornottheintendedobjectivesofthedomesticbiogasinitiativehavebeenactualizedbytheparticipantsoftheproject.
Thispaper,therefore,intendstoinvestigatetheeconomicbenefitsofdomesticbiogasplantsalongwiththechallengesfacingitandfutureprospectsofthebiogasinitiativeinselecteddistrictsofnorthernEthiopia.
Methods:Qualitativedataweregatheredusingfocusgroupdiscussionandkeyinformantinterviews.
Asurveyof400householdswasalsoadministeredtocapturecrosssectionaldatausingstructuredquestionnaires.
Thequalitativedatawereanalyzedusingcontentanalysis.
Apropensityscorematchingmodelwasemployedtoevaluatetheeffectsofdomesticbiogastechnologyonenergyexpenditure,cropyield,andthesubstitutionofchemicalfertilizers.
Results:Thestudyfindsthatbiogasadoptershavereducedtheirmonthlyenergyexpenditureonaverageby20–36%.
Moreover,theexistenceofapositivecropyieldpremiumof1.
5quintal/year/householdwasobservedasaresultofusingbio-slurryasafertilizer.
Thekeyfactorsthatlimittheextensionofbiogastechnologytopotentialbiogasadoptersarethepresenceoffaileddigesters,aninadequateplotoflandforthedigesterconstructionandawateravailabilityproblem.
Inlightofsuchbarriers,however,thestudyfindsthatmorefavorableenvironmentsforthewidespreaduseofthetechnologyexist.
Conclusions:Biogasuserhouseholdshavesignificantlyreducedtheirenergyexpenditurecomparedtonon-biogasadopters.
Nevertheless,despitethemodestincreaseincropyield,theoveralleffectofbio-slurryapplicationoncropproductivityandsubstitutingchemicalfertilizerswasnotsignificantbecauseofanimproperbio-slurryutilizationandmanagement.
Keywords:Biogasenergy,Bio-slurry,Energyexpenditure,Futureprospects,TigraiCorrespondence:haftu.
etsay@mu.
edu.
et;haftu04@gmail.
comDepartmentofAgriculturalandResourcesEconomics,MekelleUniversity,Mekelle,EthiopiaEnergy,SustainabilityandSocietyTheAuthor(s).
2018OpenAccessThisarticleisdistributedunderthetermsoftheCreativeCommonsAttribution4.
0InternationalLicense(http://creativecommons.
org/licenses/by/4.
0/),whichpermitsunrestricteduse,distribution,andreproductioninanymedium,providedyougiveappropriatecredittotheoriginalauthor(s)andthesource,providealinktotheCreativeCommonslicense,andindicateifchangesweremade.
KelebeEnergy,SustainabilityandSociety(2018)8:30https://doi.
org/10.
1186/s13705-018-0171-2BackgroundIndevelopingcountries,around2.
5billionpeoplerelyonsolidbiomasssuchasfuelwood,charcoal,agriculturalwaste,andanimaldungtomeettheirenergyneeds,pri-marilyforcookingandlighting[1].
Inmanycountries,particularlyinruralareas,theseresourcesaccountforover90%ofhouseholdenergyconsumption[2].
Suchahighbiomassenergyconsumptionhabitindevelopingcoun-trieshasresultedinvariousenvironmentalproblemslikedeforestation,soilerosion,andpoverty[3,4].
AreportbytheFAO[5],forinstance,showsthat5%ofglobaldefor-estationisduetofuelwoodconsumption,and55%ofthewoodextractedfromforestsisusedforfuelpurposes.
Sub-SaharanAfrica(SSA)inparticularisthehighestsub-regionintermsofbiomassenergyutilization,whichaccountsforabout85–95%oftotalenergy,whereas60–90%isusedforthedevelopingworldasawhole[6,7].
Inthissub-regionwheretraditionalenergysourcesentirelysatisfythemajorityoftheenergyneedsofruralhouseholds,biogastechnologycanbeviewedasoneoftherenewableandsustainabletechnologiestoreduceitsenergyhungerandenvironmentalproblems[8].
TheauthorfurtherassertsthatAfricancountrieshaveatremendousbiogaspotentialasitisproducedfromagriculturalresidues,isrelativelysimpleandcanoperateonasmallandalargescaleinbothurbanandrurallocations.
Moreover,themajorityofpeopleinSSAalsoexceedinglydependoncombustiblesfordo-mesticcookingandheatingpurposes.
Combustiblere-newableenergyresources,inparticularcharcoal,woodfuel,driedcrop,andanimalresidues,haveenvironmen-talandhealtheffectsduetoitsincompletecombustion[9].
Therehavebeenglobalandcontinentalinitiativestowardsthedevelopmentandpromotionofalternativeenergysourcesinthepastthreedecadestoaddresstheadverseimpactsofsolidbiomassenergyconsumption[10].
TheimportantcontinentalinitiativeinAfricaisthe"AfricaBiogasPartnershipProgramme,"whichwaslaunchedin2007todisseminatesmall-scalebiogasplantsinselectedcountriesofthecontinent.
TheAfricaBiogasPartnershipProgrammeisapartnershipbe-tweentwoDutchnon-profitorganizations,HumanistInstituteforDevelopmentCooperation(Hivos)andtheNetherlandsDevelopmentOrganization(SNV),whichsupportsdomesticbiogasprogramsintenSSAcoun-tries,ofwhichEthiopiaisoneamongthebeneficiariesoftheprogram[11].
Ethiopia'senergychallengeshavebeendescribedasacutedespitetheavailabilityofalargeenergyreserveinthecountry.
Thisenergyscarcityproblemismanifestedmainlyintheformofaverylowper-capitaelectricityconsumptionandthedominanceoftheuseoftrad-itionalbiomassfuels.
Therearereportswhichshowthattheper-capitaenergysupplyandconsumptionofEthiopiaislowerthaneventhatofmostofthesub-SaharanAfricancountries.
AreportbytheInter-nationalEnergyOrganization[12],forexample,showsthattheper-capitatotalprimaryenergysupplyinEthiopiawasmerely0.
4tonoftheoilequivalentwhiletheaverageforAfricaamountedto0.
67in2011.
Thesamesourcealsoindicatesthattheannualper-capitaelectricityconsumptioninEthiopiawasonly55kWhwhileitwas592kWhforthewholeofAfrica.
Moreover,thepercentageofpopulationwhoreliedonthetraditionaluseofbiomassfuelforcookingwas93%inEthiopiain2009,whileitwas65%inAfrica,77%insub-SaharanAfrica,and39%intheworldasawhole[13].
ThisoverdependenceontraditionalfuelsourcesinEthiopiahassignificantlycontributedtosevereenvironmentaldeg-radationssuchasdeforestation,soildegradation,andlossofbio-diversity[14].
Itisanticipatedthattraditionalbio-massfuelswillcontinuetobetheprimarycookingfuelsinmostruralcommunitiesofthecountryatleastinthenearfuture.
Hence,reducingenergy-povertyinsuchcontextdependsonthescaleofutilizingtechnologiesthatminimizetheharmfuleffectsoftraditionalbiomassfuels.
Amongothers,theuseofbiogasenergyhasbeenindi-catedtobevitaltoincreasecookingefficiency,reducesmoke,reducesolidfuelwoodconsumption,andimprovetheoverallsafetyofruralhouseholds[14].
Biogasenergyisgeneratedthroughanaerobicdiges-tion.
Itcontainsmainlymethane(50–70%)whiletherestismostlycarbondioxideandasmallamountofothergases[15].
Anaerobicdigestionconvertshumanexcreta,animaldungandotheragriculturalresiduesintoacleanandenvironmentallyfriendlyenergycommodity.
Biogashasalsobeenrecognizedasatechnologywiththepoten-tialforvastenvironmental,economic,andhealthbene-fits[16].
Regardingtheenvironmentalbenefits,anaerobicdigestioncansignificantlylowergreenhousegasemissionsfrommanureanddirectcombustionofsolidfuelwood.
Inadditiontothis,bysubstitutingthesolidfuelscommonlyusedforcookingindevelopingcountries,suchaswoodandcharcoal,alleviatespressureontheforests[17].
Furthermore,usingbiogasenergyasasubstituteforfossilfuelscansignificantlyreducetheamountofgreenhousegasemissions.
Italsosavessub-stantialtimebyreducingfuelwoodcollectionandcook-ingtimes[18].
Thetechnologycanalsooffersubstantialeconomicbenefitsespeciallytowomen,whoaretheprimevictimsofdirtyfueluse[19].
Apartfromthepro-ductionofbiogas(methane),anaerobicdigestiontrans-formstheaddedfeedstockintoabio-slurrythatcanbeusedasanorganicfertilizerandsubstitutechemicalfertilizerforcropproduction.
Itis,therefore,apparentthatbiogastechnologyessentiallymeetsmostofthekeyrequirementsforaddressingtheenergyaccessandenvir-onmentalproblems.
ItalsoprovidessomeeconomicKelebeEnergy,SustainabilityandSociety(2018)8:30Page2of14gains.
Biogastechnologycanalsobeappliedwherevertherearesufficientorganicandlocallyavailablemate-rials.
However,theconcernofmanystakeholdersofthebiogasprogramcannotbeneglected,whoaskwhythediffusionofthetechnologyremainslowandabandonedinmanypartsofEthiopiadespitetheinternationalandnationaleffortstopromotethetechnologyinthatplace.
Manystudieshavebeenconducteddealingwiththebenefitsandbarriersofbiogastechnologyinsomere-gionsofEthiopia.
Regardingitspotential,forinstance,KampandForn[20]statedthatthephysicalgeographyofmanypartsofEthiopiacomplieswiththetechnicalcriteriaoftheoperationofbiogasplantsintermsoftemperatureandavailabilityofwasteorganicmatter.
Similarly,theavailabilityofcheapfeedstocksfromlive-stockandagriculturalresiduesarereportedtobethecountry'sfuturepotentialforinstallingsmall-scalebiogastechnology[21].
Onthecontrary,someotherliteraturedatashowthatsocio-economicattributes,demography,technicalchallenges,andinstitutionalbarriersarethemajorchallengesfacingbiogastechnologyinEthiopia[20,22,23].
Besides,lackofproperlyeducatedpersonnel,inadequateaccesstobiogasappliancesandaccessories,poorprivatesectorparticipation,inadequatemaintenanceandrepairservices,andpoorqualityofdi-gestersarealsofoundtobeseriousbottlenecksthatin-hibitthediffusionofthetechnologyineastAfricaandparticularlyinEthiopia,Rwanda,andUganda[24–28].
Ontheotherside,therearealsostudiesconductedintermsoftheincentivestowardsthepromotionofbiogastechnologyinsub-SaharanAfricaandinEthiopiainpar-ticular.
AccordingtoAmigunetal.
[29],biogasadoptersinEthiopiahavealreadystartedexperiencingthebenefitsoftheproject;suchastheuseofcleancookingfuelandincomesavingsmadeintermsoftimeandmoneytosearchforfuelandtopurchaseothertraditionalfuels(firewood,charcoal,andkerosene),therebymotivatingotherpotentialbiogasuserstoadopt.
Inlightofsuchbenefits,thispaperasksthecriticalquestionofwhythewidespreaddisseminationofthistechnologyhasbeenprevented,asthepreviousstudiesintheTigrairegiondidnotfullyaddresswhetherornottheintendedobjectivesofthedomesticbiogasprogramofEthiopiahavebeenactualizedbytheparticipants.
Theaimofthispaper,whichfocusesonsmallholderfarmersinNorthernEthiopia,isthereforetoexaminetheimpactofthedomesticbiogasprogramonthethreemainout-comes:whethertheaccesstoadomesticbiogasplantleadstoreductionsinenergy-relatedexpenditure,whetheritaffectedthecropyieldandsubstitutionofchemicalfertilizer,andwhatarethechallengesfacingthealreadyinstalledbiogasplantsandthefuturepoten-tialfortheextensionofthedomesticbiogastechnologyintheTigrairegion.
TheoreticalframeworkThebasictheoreticalframeworkunderlyingthisstudyevolvesfromthetheoryofenergystacking,particularlytransitionandmultipleusesofenergysources.
Accordingtotheexistingliterature,therearetwowell-establishedandofcoursecontradictingviewstobefoundinenergytransitionmodelsonhowhouseholdsmovetowardstheuseofmodernfuels.
Theseincludeenergyladderanden-ergystackinghypotheses[30,31].
Theformeroneisbuiltontheideathatmodernfuelsareconsideredtohavemoreadvantagesthanthetraditionalfuelsinmanystandards,andarethusconsideredtobehigherrungsontheladder.
Themainargumentofthistheoryisthathouseholdsswitchfromtraditionalfuelstotransitionfuels(suchascharcoal,kerosene,andbio-fuels),andlaterontomodernfuels(suchasliquefiedpetroleumgas(LPG)andelectri-city)asaresultofariseinincome.
Inshort,themodelhy-pothesizesthathouseholdsmovealongtheenergyladderastheirincomeincreases.
Morerecently,however,variousstudieshavereportedanumberofpitfallsespeciallyintheapplicabilityofthetheoryoftheenergyladderinde-velopingcountriesandinparticularinaruralsetting.
Odihi[32],forinstance,hasdiscussedthechallengeswithregardtothepracticabilityofthismodelinde-velopingcountriesfortheobviousreasonsthatthepresenceofbothinadequatefueldistributionanden-ergyfacilitiesarebeyondthereachofmanyhouse-holdsregardlessoftheirlevelofincome.
Inreality,indevelopingcountriesparticularlyinruralareas,householdsdonotlinearlyswitchtomodernfuelswithariseinincomesincethechoiceoffuelsisnotde-terminedsolelybydisposableincome[33,34].
Accord-ingtotheenergystackingmodel,householdsmaydevelopastackingbehaviorsothattheycanusemorethanonefueltypesimultaneouslyinsteadofsimplysub-stitutingtheearlierones.
Besides,theenergyladderthe-oryhasbeencontestedinvariousliteraturesmainlyforthefollowingreasons.
Thefirstreason,asthemultiplefuelusebehaviorofhouseholdsisnotconsideredintheenergyladdermodel.
Indevelopingcountries,becauseofanunreliablesupplyofmodernenergy,householdspre-fertouseamixofenergytobeonthesafesideduringthetimeswhenprimaryenergysourcesarenoteasilyavailable.
Secondly,themulti-purposenatureofvariousenergysourcesisalsoanimportantconceptthatdeter-minesthedecisionofhouseholdstowardsfuelprefer-ence.
Thisfactorhasalsobeenoverlookedbytheexistingenergytransitionconcepts.
Nevertheless,theen-ergystackingmodelhasbeenreportedtobeamoreac-ceptabletheoreticalframeworktoexplaintheadoptionbehaviorofhouseholdsindevelopingcountries[34–37].
Therearesomeenergysourceswhichmayhaveimport-antcontributionsnotonlyinsolvingtheenergyproblembutalsoinplayingapivotalroleinothersectors.
ForKelebeEnergy,SustainabilityandSociety(2018)8:30Page3of14instance,theby-productsofsomeofthebiofuelsareusefulforagriculture(soilfertilityenhancementandfor-ageforlivestock).
Theexistingenergytransitionmodelsdonottakeintoconsiderationsuchmultipleservicesofagivenenergysourcewhenexplainingthebehaviorofhouseholdstowardsthepreferencesoffuels.
Inthispaper,theresearchfocusisontheconceptofenergytransitionconstraintsandmultipleusesofenergysources,whichareconsideredtobeimportantvariablesthatexplainthehouseholdbehaviortowardstheuseoffuelsamongasetofenergyoptions.
Thestudyaddressesthekeyconstraintsandprospectsoftransitiontowardsbiofuelsandhowthemulti-purposenatureofbiofuelsdeterminesthepreferenceofhouseholdstowardsvariousenergyoptionsbytakingfamily-sizedbiogasdigestersasacasestudy,asitsenergytechnologyproducesbiogasenergy(methane)andorganicfertilizer(bio-slurry)whichisusefulforenhancingcropproductionbysubsti-tutingchemicalfertilizer.
MethodsStudysitesThestudywasconductedinthreerandomlyselecteddis-trictsoftheTigrairegion.
TheseareOfla,Hintalo-Wajerat,andEnderta,wheredomesticbiogastechnologyhasre-centlybeenintroducedbytheNationalDomesticBiogasProgrammeofEthiopia.
Thestudyareasarespatiallydis-tributedacrossthreedistrictstocaptureheterogeneousdataonsocio-economicattributes,energyconsumptionpatternsandbiomassenergypotentials.
Thestudysitesarealsocharacterizedbyvariousclimaticandtopographicaldomainsrangingfromaltitudedifferencestotemperatureandrainfallvariationsaswellasendowmentofbiomassenergysources.
Thefarmingsystem,whichwasobservedtobeamixoflivestockandcropproductioninallstudysites,isalsoamongthesourcesoftraditionalenergy.
Theenergyconsumptionpatternacrossthethreestudysitesisobservedtobefairlysimilarwhichisinfactdominatedbybiomassenergy.
Sampledesign,procedures,anddatacollectionThestudyareaswereselectedusingmulti-stagesam-plingtechniques.
Inthefirststageofthesamplingpro-cedure,thethreedistrictswererandomlyselected.
Thenafter,basedonthenumberofdomesticbiogasplantsin-stalled,twohigh-achieving"tabias"1fromeachdistrictwerepurposivelychosenwithasupportofexpertsfromtheofficeofminingandenergyofthestudydistricts.
Thesamplingframeforthisstudywashouseholdswhousetheendproductsofdomesticbiogastechnology(methaneandbio-slurry)forfuelandfertilizerpurposes.
Asimplerandomsamplingtechniquewasthenappliedtoselecttherespondentsfromthelistofbiogasuserhouseholds(hereafterreferredastreatedobservations)andnon-biogasuserhouseholds(hereafterreferredtoascontrolobservations)ofeachselected"tabia.
"Thisstudyusedacross-sectionalsurveyof400ran-domlydrawnhouseholds,bothtreatedandcontrolobser-vationscomprisedof200each,from3districtsand6tabiascarriedoutbetweenFebruaryandApril,2016.
Thesampleforthetreatedobservationswasdrawnfromasetof1887households,whichintroducedafamily-sizedbio-gasplantinthethreedistrictsasofDecember,2015.
Anattemptwasmadetoincludedigesterswhoseconstructionhadbeencompletedatleast6monthspriortothesurveywithanintentionthatthistimelagprovidedadequatetimeforhouseholdstodeveloptheexperienceneededtooperateadigesterandatthesametimeexperiencethebenefitsofowningasmall-sizedbiogasplant.
Themajorityofthebiogasusers(1061)werefromtheHintalo-Wajeratdistrict.
TheOflaandEndertadistrictsalsohad516and310biogasusers,respectively,duringthesurvey.
FollowingWatson[38],thisstudyadoptsEq.
1tocalculatetherepresentativesamplesizefromthetargetpopulation.
Thedistributionofthesamplesizeacrossthedistrictswasbasedontheirrelativeshareofthebiogasuserstothetotalsamplingframe(targetpopulation)asshowninTable1.
np1pe2Z2p1pN1wheren=samplesize.
N=targetpopulation(1887).
e=precisionlevel(0.
065).
Z=1.
96,confidencelevelat95%.
P=0.
5,estimatedpopulationproportionn0:510:50:06521:9620:510:51887n200Therequireddatawerecollectedfromtheselectedheadsofhouseholdsusingstructuredquestionnaires.
Focusgroupdiscussions,keyinformantinterviews,andfieldobservationswerealsousedtovalidatethehouse-holdsurveyandtoacquirein-depthqualitativedata.
ATable1SamplesizefromeachstudysiteStudysiteTargetpopulationSamplesizeBiogasusers(treatment)Non-biogasusers(control)TotalOfla5165555110Hintalo-Wajerat1061112112224Enderta310333366Total1887200200400KelebeEnergy,SustainabilityandSociety(2018)8:30Page4of14pre-testedquestionnairewasdeployedtogatherthedatawithregardtoawiderangeofsocio-economicaspectsandhouseholddemographics,occupation,education,cookingbehavior,energy-relatedexpenses,andfueluse.
Inaddition,thequestionnairecontainedasectionaboutthereasonsfor(not)adoptingbiogas,thesourceoffundsforthedigesterandfollowupandtechnicalsup-portsbytheNationalBiogasProgrammeofEthiopia.
Furthermore,qualitativedataonchallengesandoppor-tunitiesofthebiogassectorwereacquiredusingfocusgroupdiscussionsandkeyinformantinterviews.
Thesecondarydatawerecollectedfrompublishedarticlesandunpublishedgovernmentalreports;inparticular,re-portsoftheNationalBiogasProgrammeofEthiopia,theTigraiRegionalBiogasProgrammeCoordinationOfficeandtheCentralStatisticalAgencyofEthiopia.
DataanalysisToanalyzethetrends,impedimentsandprospectsofthebiogassector,acontentanalysiswasused.
Descrip-tivestatisticssuchasmeasuresofcentraltendencyanddispersionswereemployed.
Statisticaltests(mainlyttests)werealsodeployedtodeterminethedifferencesbetweentreatedandcontrolobservationsinregardtovarioussocio-economicattributes.
Inordertoanalyzetheimpactofthebiogastechnologyinterventiononen-ergyexpenditure,cropyieldanduptakeofchemicalfertilizer,propensityscorematchingwasdeployedtore-ducethepossiblesamplingbiasastheparticipationinthedomesticbiogasprogramisnotrandom.
Propensityscorematchingmodel(PSM)Therearetwomainconcernswithregardtothepar-ticipationinabiogasprograminrelationtoemploy-ingPSMfortheanalysisinthisstudy.
First,thebiogasinitiativeisvoluntaryandhouseholdsneedtoapplyforabiogasplant.
Second,conditionalonappli-cation,programbeneficiariesarenotselectedatran-dombutneedtofulfilltheeligibilityconditionssuchasownershipofatleastfourcattle(localbread)toensureadequatecattledungforanaerobicdigestionandanadequatespaceforthebiogasdigestertanktobebuilt.
Duetothesetworeasons,self-selectiontoparticipateintheprogramandtheimpositionofeligi-bilityconditions,itismorelikelythatthosewhoapplyandobtainabiogasplantaresystematicallydif-ferentfromthosewhodonot.
Hence,comparisonbe-tweenhouseholdswhohaveabiogasplantandthosewhodonot,withoutaccountingforpotentialdiffer-encesinfactorsthatdetermineselectionintothepro-gramaremorelikelytoyieldincredibleestimates.
Tocapturesuchaproblemofbiasedness,householdsthathaveparticipatedinthenationaldomesticbiogaspro-gramofEthiopiawerebasicallycomparedtothosethathavenotyetparticipatedinemployingthepropensityscorematchingmodel.
Thetreatmentinthiscaseispar-ticipatinginthedomesticbiogasprogramwheretheout-comeswerechangeinenergyexpenditure,uptakeofchemicalfertilizerandcropyield.
Thestudypassedthroughtwostepstoanalyzetheimpactofthedomesticbiogasinitiativeontheoutcomevariables.
Initially,follow-ingBecherandIchino[39],theprobabilityofinstallingadomesticbiogasplant,alsoknownasthepropensityscore,forthetreatedandcontrolobservationswasestimatedbymeansofselectionEq.
2thatusesabinarylogitmodel(Table5).
ThefulllistsofexplanatoryvariablesincludedinthisstudyarepresentedinTable2.
Thesecondstepwascomputingtheaveragetreatmenteffectontreated(ATT)overtheoutcomeofEq.
5;(wheretheATTistheaverageeffectofthetreatmentforcasesthataretreatedandmustaverageovertheoutcomesoftreatmentforthetreatedobservations(Y1|T=1)presentedinEq.
5.
ThismeansthatATTistheaveragedifferenceinenergyex-penditure,cropyield,anduptakeofchemicalfertilizerbe-tweenhouseholdswithandwithoutbiogasenergyaftermatching(Tables6and7).
Thiswasachievedbymatchingbiogasuserandnon-userhouseholdsaccordingtotheirpropensityscoreusingthenearestneighbor,radius,kernel,andstratificationmatchingmethodsassuggestedbyBeckerandIchino[39].
TreatmentDisabinaryvariablethatdeterminesifthehouseholdusesbiogastechnologyornot,D=1fortheusersandD=0otherwise.
Xidenotesthepre-treatmentcharacteristics(charac-teristicsofhouseholdsthatmightaffecttheadoptionde-cisionofbiogastechnology).
PXiprobD1=XiED=Xi2Eq.
2indicatesthattheprobabilityofadoptiondeci-sionofhouseholdstowardsbiogastechnologyiscondi-tionaltothepre-treatmentcharacteristicsofhouseholds.
yy1ifD1y0ifD03InEq.
3,Ydenotesthetreatmenteffects(impactofadoptingbiogastechnologyonenergyexpenditure,cropyield,andutilizationofchemicalfertilizer).
Inordertoknowwhatwouldhavehappenedtotheoutcomevari-ables(energyexpenditure,cropyield,anduptakeofchemicalfertilizer)hadthehouseholdsnotusedbiogasenergyandbio-slurry,theoutcomeYamongthepartici-pants(Y1)andnon-participants(Y0)aftermatchingoughttobecompared.
Averagetreatmenteffect(ATE):TheATEshowsthedifferencebetweentheaverageenergyconsumption,cropKelebeEnergy,SustainabilityandSociety(2018)8:30Page5of14yield,andchemicalfertilizeramongthebiogasuserandnon-userhouseholdswithoutmatchingasshowninEq.
4.
Δy1y0ATEEΔEy1jx;D1Ey0jx;D04Equation4maybebiasedincasethetreatedandcon-trolvariablesarenotsimilar,whichisobviousinobser-vationalstudiesincontrasttoexperimentalstudies.
Toovercomethisproblem,itisrecommendedtousetheaveragetreatmenteffectonthetreatedcases(Eq.
5).
Averagetreatmenteffectonthetreated(ATT):Eq.
5isacounterfactualsituationwhichcomparestheaverageenergyexpenditure,cropyield,anduptakeofchemicalfertilizerofthebiogasadopterandnon-adopterhouse-holdsaftermatchingbasedontheirpropensityscorestoadoptbiogasenergytechnology.
ATTEΔjpx;D1Ey1jpx;D1Ey0jpx;D05ResultsanddiscussionDescriptionofthesampledhouseholdsTable3summarizesthesocio-economicanddemo-graphicattributesofsampledhouseholds.
Thereisasig-nificantdifferencebetweenthebiogasuserandnon-userhouseholdsinmanyofthesocio-economicalanddemo-graphicalvariablesthatareincludedinthisstudy.
Forinstance,theaverageage,levelofeducation,familysize,farmsize,andannualincomeofthetreatedcases(biogasusers)werefoundtobesignificantlyhighercomparedtothatofthecomparisonobservationsasshowninTable3.
Morespecifically,householdswhoadoptedbiogastech-nologyarefoundtobeolderthantheirnon-adoptercounterparts.
Thisgivestheimpressionthatolderhouseholdstendmoretousebetterenergysourcessuchasbiogasenergyduetothepossibilityofabetterwealthaccumulationcomparedtotheyoungsters.
Theprofileofthehouseholdsalsoindicatesthatthebiogasuserhouseholdswerefoundtohavehighereducationalat-tainmentsthanthatofnon-users,whichimplieseduca-tionisakeyelementformoderntechnologyadoptionanduse.
Besides,theaveragefarmsizeofbiogasusersandnon-userswas2.
5and2tsimad2respectivelywithasignificantdifferencebetweenthetwogroups.
Similarly,biogasuserswerefoundtohavehigherannualincomeandfamilysizethanthatofnon-userhouseholdswhichhighlightsthathigherincomemaybeassociatedwiththeutilizationofbetterenergyfacilities.
Thedescriptivestatisticsofthisstudyconfirmsthathouseholdsthathavealreadyadoptedbiogastechnologyhavehigherin-comesthanthatofnon-adopters(Table3).
Thecoeffi-cientofbinarylogitregression(Table5)alsoconfirmsapositiveandsignificantrelationshipbetweenthetwovariables.
Thisimpliesthatariseinincomeofhouse-holdsmaycauseapartialshifttorelativelybetterenergysourcessuchasbiogastechnology.
Ontheotherhand,ahouseholds'incomerisesasaresultofreductioninen-ergyexpenditure.
Therefore,abi-directionalrelationshipbetweenincomeandbiogasadoptionisevident.
Table2DescriptionoftheindependentvariablesusedtoexplaintheprobabilityofadoptingbiogastechnologyNameofthevariableNatureofthevariableHypothesizedrelationshipwiththedependentvariable(biogasadoption)DescriptionofthevariableAgeContinuousPositive/negativeAgeofthehouseholdheadinyearsSexDummyPositive/negativeSexofthehouseholdhead;adummyvariableforgenderrelationships(male=1,female=0)FamilysizeContinuousPositive/negativeFamilysizeofthehouseholdEducationContinuousPositiveEducationlevelofthehouseholdheadinyearsCattleholdingContinuousPositiveNumberofcattleownedbythehousehold(heads/hh)AnnualincomeContinuousPositiveAnnualincomeofthehouseholdinETBDistFireContinuousPositiveDistancetonearestfirewoodcollectionsiteinkilometerDistWaterContinuousNegativeDistancetonearestpermanentwaterpointinkilometerDistMarketContinuousPositive/negativeDistancetonearestmarketinkilometerAvailabilityofelectricityDummyNegativeAvailabilityofmodernfuelsmainlyelectricity(yes=1,otherwise=0)FarmsizeContinuousPositiveTotalsizeoffarmplotsownedandoperatedbythehouseholdinTsimadFertilitystatusCategoricalPositive/negativeFertilitystatusoffarmplot(1=poor,2=medium,3=good)FarmlocationContinuousNegativeDistancebetweenhouseandfarmofthehouseholdinkilometerExtensionserviceContinuousPositiveFrequencyofcontactsbetweenagriculturalextensionworkerandthehousehold(frequencyinayear)KelebeEnergy,SustainabilityandSociety(2018)8:30Page6of14Thestudyshowsthattherewerenostatisticallysignifi-cantdifferencesobservedinthecattleholdingbetweenthetwoobservationssignalingthatavailabilityoffeedstockisnolongerachallengeforabiogasadoptiondecisionatthestudysitessincetheaveragecattleholdingforbothobservedcaseswas5headswhichisquitehigherthantheminimumheadsofcattlerequiredtooperatea6m3biogasdigester(accordingtoNationalBiogasProgrammeofEthiopia,aminimumof4headsofcattleisrequiredinthecontextoftheruralpartofthecountry.
ChallengesfacingthebiogastechnologyandfutureprospectsThehouseholdsurveyshowsthatinadequateenergy(methane)production,frequentdamageofinstalleddi-gestersandinadequateinstitutionalsupportarethemajorchallengeshamperingthesmoothoperationofbiogasplantswhichaccountfor32%,31%,and22%ofthetotalbiogasuserrespondents,respectively(Table4).
Thesefiguresimplythataconsiderablenumberofbio-gasdigesterownersfacetechnical-relatedchallenges,asalowlevelofenergyproductionanddamageofthebio-gassystemusuallyinducedbytechnicalrelatedfaults.
ThereportoftheNationalBiogasProgrammeofEthiopia[40]alsoshowsthattheuptakeofbiogastech-nologyislaggingbehindthetargetwhichstrengthensthefindingsofthehouseholdsurvey(Fig.
1).
Despitetheplantoinstall15,100domesticdigestersinfourregionalstatesofEthiopiafrom2008to2014,only63%oftheplanwasachieved.
Similarly,intheTigrairegionalone,wherethisstudywasconducted,3873domesticbiogasdigestershavebeenbuiltcomparedtotheplanned5288digesters,whichis73%ofthatwhichwastargetedtobeinstalled.
Therefore,theuptakeofbiogasdiffusionoverthepastyearsseemstohaveexperiencedirregularitiesattheregional(Tigrai)anddistrictlevels.
Thisreportmayalsobeconsideredasanindicatorthatthetechnologyhasbeenhurdledbytheabovestatedbarriers.
Figure1showsthatduringtheearlyperiodsofthebiogasinitia-tive,theuptakeincreasedandreacheditspeakin2013.
Sincethen,however,itfacesstagnationandinfactslo-weddowninsomeofthestudysites.
Thiscouldalsobeconsideredasanindicatorofthetechnicalchallengesthatfacestheinstalleddigesters.
Besides,keyinformantsfrequentlyreportedthatbadhabitssuchasirregularorinsufficientfeedingofthebio-digestersignificantlyhin-derbiogasproductionandeventuallystopworking.
Thepresenceofsuchnon-operatingdigestersinneighbor-hoodsdefinitelyinfluencedthepromotionofthetech-nologyduetospillovereffectsasmanypeoplearemorecuriousaboutbadstoriesthansuccessstoriesofanewtechnology.
AstudybyParawira[8]supportsthefind-ingsofthecurrentstudybydisclosingthatlowperform-anceandpoorqualityofinstalledplantscontributedtothedis-adoptionofbiogasdigestersinsub-SaharanAfrica.
Moreover,thecurrentfindingscomplywithEshetieetal.
[21]whoreportedthatthemajorTable3Meanvalueofbasicsocio-economicanddemographicvariablesofrespondents(standarddeviationinparentheses)VariablesTreatedobservations(n=200)Controlobservations(n=200)Totalsample(n=400)PvalueSexofthehouseholdhead(female=0,male=1)0.
86(0.
34)0.
89(0.
31)0.
87(0.
33)–Ageofthehouseholdheadinyears47(9.
18)45(10.
3)46(9.
8)0.
03Educationlevelofthehouseholdhead(yearsofschooling)2.
5(2.
7)1.
5(2.
4)2(2.
64)0.
000Householdsize6.
3(1.
68)5.
7(1.
77)6(1.
75)0.
001Farmsizeintsimad2.
5(1.
32)2.
07(1.
57)2.
3(1.
47)0.
000Cattleholdinginheads5(2.
73)5(3.
24)5(2.
99)0.
32AnnualincomeinETB18,949.
78(12910)14,175.
5(8287.
5)16,562.
6(11095)0.
000Table4MajorchallengesandfutureprospectstowardsthetransitionofdomesticbiogasenergyVariablesPercent*Challengesfacinginstalleddigesters(n=200)Lowenergyproduction32%Damageofinstalleddigesters31%Inadequateinstitutionalsupport22%Shortageofmanure15%Reasonsfornotadoptingbiogastechnology(n=200)Lackoffeedstock13%Highcostofconstruction24%Nocreditaccess13.
8%Spillovereffectoffaileddigesters52.
3%Nospacefordigesterpitpreparation48.
5%Waterproblem37.
6%Limitedknowhow14.
2%Favorableconditionsforwiderpromotionofbiogastechnology(n=400)Availabilityofcheapfeedstocks39%Existenceofsubsidyforthetechnology25.
5%Multifacetedbenefitsofthetechnology39.
9%Scarcityofsolidfuels44.
5%Increasethepriceofsolidandfossilfuels36.
2%*Multipleresponsesispossible,nstandsfornumberofrespondentsKelebeEnergy,SustainabilityandSociety(2018)8:30Page7of14bottlenecksfacingtheextensionofthebiogastechnol-ogyincludetechnicalproblems,abandonment,andlossofinterest.
Regardingthereasonsfornotadoptingbiogastechnol-ogy,thesurveyednon-biogasadoptersrespondedthatthespillovereffectoffaileddigesters(52.
3%),inadequatespaceforpitpreparation(48.
5%),andwaterproblems(37.
6%)constitutedthecoreissues(Table4).
Itwasalsoobservedduringthefieldsurveythatasubstantialnumberofdigesterswerenotoperatingatallstudysites.
Thismighthavecontributedtothesluggishbehaviorofmanyeligiblehouseholdsfornotparticipatinginthedomesticbiogasprogram.
Lackofapermanentwatersupplyinthenearbyareawasalsoreportedtobeachallengeforpoten-tialadopters.
Anaerobicdigestionnormallyconsumesaconsiderableamountofwater,whichisaproportionequaltotheamountofmanuretobeloadedintothedigester.
Itis,therefore,unlikelyforhouseholdstoadoptbiogasen-ergywithoutensuringapermanentwatersupplywithinareasonabledistance,accordingtotheNationalBiogasProgrammeofEthiopiaatmost30minawayfromtheresidence.
Thekeyinformantsvalidatedtheresultsofthehouseholdsurveybydisclosingthatthesuitabilityofasiteandtheavailabilityofspacelimittheuptakeofbiogastechnologybyhouseholds.
Insomelocations,becauseoftherockynatureofthesurface,itisdifficultormorelabor-demandingandexpensivetodigapitforthedi-gester;consequentlyhouseholdsarereluctanttoadoptthetechnology.
Theparticipantsoffocusgroupdiscussionalsounderlinedthatthespillovereffectoffaileddigesters,inadequatetrainingandpoorfollowupoftechniciansandinadequatemaintenanceserviceshavepreventedwide-spreaddisseminationofthetechnology.
Similarresultshavebeenreportedregardingbarrierstothelarge-scaleadoptionofdigestersindifferentsub-SaharanAfricancountries.
Forinstance,inTanzania,inadequatewateravailability,poorperformanceofdigestersandpoorfollowupwerereportedtobemajorchallengesforthewide-spreaduseofbiogastechnology[24,26].
Similarchal-lengesonasmallerscalearealsoreportedfromothersub-SaharanAfricanandAsiancountries[41–46].
Lookingatthefutureprospectsofbiogastechnology,thesurveyedhouseholdsstatedthatthepresenceofscar-cityofsolidfuels(44.
5%),themultipleuseofbiogas(40%),andtheavailabilityofcheapfeedstocks(39%)arethefavorableconditionsandpressingfactorsforthefuturepromotionofthesector(Table4).
Equallyimportant,theexistenceofgovernmentsubsidyforthetechnologyandtheeverrisingpriceofbothsolidbiomassandmodernen-ergysourceswerealsoconsideredbytherespondentsasanopportunityforthefuturepromotionofthetechnol-ogy.
Fortoomanypeople,thescarcityofsolidfuels,de-pendenceontoofewforestedareas,alongwiththelargenumberofhouseholdswithindoorandoutdoorfedcattlewouldhelptomakebiogasasuitableandaccessibletech-nologyforsmallholderfarmhouseholds.
Theresultofthedescriptivestatisticsalsoshowsthathouseholdsthatadoptedbiogastechnologyarespatiallylocatedfarawayfromthenearestfirewoodcollectionsiteascomparedtothenon-adopters.
Biogasusershavetospendonaverage5h(roundtrip)fromtheirhousetothefuelwoodcollec-tionsiteandthenon-adopters4h.
Thissignalsthattheunavailabilityoffuelwoods(forestsandwoodlots)inanearbyareacompelsfarmerstolookintootheralternativeenergysourcessuchasbiogasenergyinsteadoffullyrely-ingonscarcesolidbiomassenergysources.
Fig.
1UptakeofbiogastechnologyinTigrairegionandstudydistrictsKelebeEnergy,SustainabilityandSociety(2018)8:30Page8of14AsshowninTable4,theavailabilityofcheapfeed-stockwasmentionedasoneofthefavorableconditionsforthefurtherpromotionofbiogastechnologyby39%ofthesurveyedhouseholds.
Thiscouldprobablybeduetothefactthattheaveragecattleholdingofthesurveyedhouseholdsisfoundtobefiveheadsforbothbiogasadoptersandnon-adopterswhichisslightlyhigherthantheminimumheadofcattlerequiredtooperatea6m3biogasdigester,fourheadsofcattleaccordingtonationalbiogasprogramofEthiopia.
Hence,thepresenceofcheapandlocallyavailablefeedstock(cattlemanure)whichisassociatedwithrelativelylargercattleholdingwouldmakethepromotionanddiffusionofbiogastech-nologymorepromising.
AreportbytheCSA[47]inthisregardalsoshowsthatthetotalestimatedcattleintheTigrairegionisnearly4.
6million,andoutofthisabout3.
8millionareaged2yearsandolder.
Theregionhas,therefore,anuntappedpotentialforbiogastechnologysincecattledunghasbeenusedasthemajorsourceoffeedstockforanaerobicdigestion.
Thebiogasdigestersinthestudyareasaremainlyloadedwithcattlemanure,humanexcreta,andwater.
Besides,stricttreecuttingmonitoringandzerograzingpoliciesinthecountrycouldindirectlyassistbiogaspromotion.
Paralleltothefindingsofthecurrentstudy,KampandForn[20]assertthatascarcityoffirewood,deforestation,depletionofsoilnutri-ents,anderosionarethedriversformorebiogastechnol-ogyinthefuture.
Moreover,suitableagro-ecologyandwidespreadrearingoflivestockarereportedtobeamongthefavorableconditionsforbiogastechnologydissemin-ationineasternAfrica[27,45].
Thepressingfactors,suchastheincreaseinthepricesoffossilfuels,woodfuels,andfertilizersinsub-SaharanAfricawouldalsomakeforabrighterfutureforbiogastechnologypromotioninthere-gion[27,48],whichisinagreementwiththefindingsofthecurrentstudy.
EconomicbenefitsofthedomesticbiogastechnologyTables6and7presentasummaryoftheoutcomesofthepropensityscorematchingusingthefourmatchingalgorithms.
Itincludesthenearestneighbor,radius,ker-nel,andstratification.
Thispaperadoptsthefourmatch-ingmethodsforthereasonthatanycomparisonstudyisfreetouseanyofthematchingalgorithms,andnoneofthemissuperiortotheothers,buttheirjointconsider-ationprovidesawaytoassesstherobustnessoftheesti-matesoftheoutcomevariables[39].
Table5showstheestimatedcoefficientsofthepro-pensityscore,whichareusedasapre-requisitefortheestimationoftheoutcomevariables.
Thediagnos-tictestconfirmstheoverallfitnessofthemodelasProb>chi2=0.
000.
Theageofthehouseholdhead,thesexofthehouseholdhead,theeducationlevelofthehouseholdhead,theincome,thehouseholdsize,theavailabilityofsolidfuels,andelectricityarefoundtobethekeyfactorsaffectingtheprobabilityofadoptingbiogastechnology(Table5).
Householdheadsthatareolderandwithrelativelyhigherincomewerefoundtobemoreinterestedininstallingthebiogastechnology.
Thisisprobablyduetothepossibilityofabetterwealthaccumulationaspeoplegetolder,andtherebycanaffordtoinstallabiogasdigester.
Femalesweremorelikelytoadoptbiogascomparedtotheirmalecounterparts.
Thereasonwhywomenaremoreinter-estedintheadoptionofbiogastechnologycouldbeduetothefactthatwomenaremoreresponsibleforcol-lectingfirewoodandarealsotheprimevictimsofindoorairpollutioninthekitchen.
Householdswhodonothavesolidfuelsourcesinnearbyareaswerefoundtobemoremotivatedtoadoptabiogasdigester.
Besides,householdswhouseelectricitywerealsofoundtobemoreinterestedinadoptingbiogastechnologycomparedtothosewhodonot.
Thereasonforthecomplementaritybetweenelectri-cityandbiogasenergymayariseduetoalowdisposablein-comeofruralhouseholdsingeneral.
Asaresult,theymaychoosetouseelectricityforonlylightingpurposesandtherelativelycheaperbiogasenergyforcookingandboiling.
Table6presentstheeffectofbiogasenergyutilizationonenergyexpenditureusingfourmatchingmethods.
Theresultsvaryasthematchingalgorithmchanges,al-thoughallmethodsreachedthesameconclusionregard-ingtheimpactofbiogasenergytechnologyonreducingenergyexpenditureofruralhouseholds.
Thisisbecausedifferentmatchingmethodsemploydifferentprinciplesandwaysofcomputingtheaveragetreatmenteffects.
Forinstance,usingthenearestneighbormethod,200treatedobservationswerematchedto93comparisonob-servations.
Whereas,inbothradiusandkernelmethods,200comparisonobservationswerematchedto200treatedobservationswhichisonetoone.
Similarly,199controlobservationswerematchedto200treatedobser-vationsusingastratificationmatchingmethod(Table6).
Despitethevariationinnumericalvalues,allmatch-ingmethodsconfirmthatthebiogastechnologyhassignificantlyinfluencedtheenergyexpenditureofsmallholderfarmers.
AsshowninTable6,theaveragemonthlyenergyexpenditureofbiogasadopterswaslessbyETB3108.
36,59,98,and82.
4thanthatofnon-adopters(Pchi2=0.
000likelihood=241.
58Table6EffectofbiogasenergyutilizationonenergyexpenditureofhouseholdsMatchingmethodTreatedobservationControlobservationEnergyexpenditure(ATT)tvalueNearestneighbor20093108.
35***4.
12Radius20020059***3.
42Kernel20020098.
2***4.
17Stratification20019982.
4***3.
6and*denotevaluesignificantat1%,5%,and10%respectivelyKelebeEnergy,SustainabilityandSociety(2018)8:30Page10of14energy[49],whichisroughlysimilartothefindingsofthecurrentstudy.
Likewise,thedomesticbiogasprogramhasresultedinareductionofhouseholds'energyexpenditureonaverageby45%inIndonesia[50]whichisslightlyhigherthanthefindingofthecurrentstudy.
Apartfromanalyzingtheimpactofthebiogasinitia-tiveonenergy-relatedexpenditures,thestudyfocusesonthesynergybetweenbiogastechnologyandagriculture.
Asthepotentialofthetargethouseholdsforfuturebio-gaspromotionisinruralareasinwhichagriculturalsec-torsremainsthesolesourceoflivelihood,thisstudytookacloserlookatthepossiblelinkagesbetweenagri-cultureandbiogasdigestersbycomputingtheeffectsofbio-slurryutilizationoncropyieldanddemandforchemicalfertilizer.
Thedominantcropsgrowninthestudysitesarecereals;mainlywheat,barely,teff,andmaize.
ThetypesofchemicalfertilizersthathavebeenutilizedbythefarmersareDAPandUREA.
Usingthefourmatchingmethodsstatedabove,thean-nualcropyieldofbiogasuserhouseholdswasfoundtobeonaveragehigherby1.
7,1.
4,1.
5,and1quintals/year/householdascomparedtonon-users,respectively,duetotheapplicationofabio-slurrytreatmentoncropfields.
Itisimportanttonotethatfieldtrialsarereportedtobeanap-propriatemethodologytocomparetheyielddifferencesofcropsasaresultofabio-slurryapplicationinsteadofapply-ingsuchanobservationalstudy.
However,fieldtrialscouldnotshowtheoverallimpactofabio-slurryapplicationonthecropyieldofparticipantsoftheinitiative(onacommu-nityandevenahouseholdlevel).
Insuchcases,animpactassessmentmethodologyismoreimportantthanfieldtrials,i.
e.
,thisanalysismethodis,therefore,theappropriatemethodforthecurrentstudy.
Nevertheless,thepapermaysufferfromsomelevelofbiassinceallfactorsthataffectcropproductioncouldnotbefullycontrolledinsuchanob-servationalstudyandmaythereforeinfluencetheaccuracyoftheabovestatedfindings.
Ontheotherhand,theannualuptakeofchemicalfertilizersofbiogasuserswasfoundtobeonaveragelessby0.
34,0.
22,0.
28,and0.
25quintal/householdcomparedtonon-userhouseholdsusingtheabovestatedmatchingmethodsinthatorder.
Unlikeenergyexpenditure,theeffectsofabio-slurryfertilizerapplicationonthecropyieldandsubstitutionofchemicalfertilizerarenotfullymaterialized.
Theproductivityeffectofthebio-slurryfertilizerwasfoundtobesignificant(P=0.
1)usingtheradiusandkernelmatchingmethods,whereastheresultsofnearestneigh-borandstratificationshownosignificantdifference.
Be-sides,therewasnosignificantdifferencetothechemicalfertilizeruptakeofbio-slurryuserandnon-userhouse-holdsusingallmatchingmethods,whichsignalsnosig-nificantsubstitutioneffectasshowninTable7.
Aconsiderablenumberofhouseholdswereobservedtohavealowlevelofunderstandingoftheimportanceandutilizationofbio-slurryasafertilizer.
Only20%ofthebiogasadopterswerefoundtobeusersofbio-slurryontheirplots.
Lackofadequateknowledgeandsocialtaboowereamongthefrequentlystatedreasonsfornotyetusingabio-slurrybytheremaining80%ofbiogasadopters.
Itwasobservedduringthesurveythatfarmersusuallydisposethebio-slurryintoanopenpitwithoutadequatecaretoprotectnutrientevaporation.
Thekeyin-formantsalsorevealedthattheapplicationofabio-slurryisoftendoneinaccuratelyandatthewrongtime.
Further-more,themasonsandthebiogasenergypromotionexpertsusuallytrainthebiogasusersonbio-slurryutilizationalthoughthefocusandexpertiseofthesepersonnelisnotrelatedtoagriculture.
Thisgivestheinsightthatbio-slurryutilizationispoorlytaughttobiogasusersbymasons,energypromotersandtechnicianswhichareinfactoutsidersintermsofthefieldofagriculture.
Thekeyinformantsfurtherstressedthatpoortech-nicalknowledge,lowawareness,andacceptanceofthistypeoffertilizerandpoorextensionsupportcoupledwithsometraditionaltaboosaretobeclaimedfortheinsignificantcontributionofbio-slurrytocropproduct-ivityandsubstitutionofchemicalfertilizer.
Besides,thefocusgroupdiscussantsunderlinedthatthenegativeconnotationattachedtothebio-slurry,asitisproducedfromcattledungandfaecalsludge,hindersitsrateofapplication.
Thesemaycontributetonotfullymaterial-izedbenefits.
Furthermore,thefactthattheBureauofAgricultureandRuralDevelopmentoftheregiondidnotplayanactiveroleintheimplementationofthedo-mesticbiogasprogramofthecountrymighthavealsocontributedtothetechnicalfaultsonthebio-slurryap-plicationandtheknowledgegaps.
Thismayhavealsoledtotheinsignificantcontributionofthebio-slurrytotheexistingcroppingsystem.
Previousstudiesreportedparallelfindingsinthisre-gard.
Inlinewiththecurrentfinding,inRwanda,forin-stance,thebenefitsofthenationaldomesticbiogasprogramincludemeetingalltheenergyneedsforcook-ingandreducingtheenergyexpenditureofhouseholds[49,51].
Inadditiontothis,Mwakaje[24]revealsthattheadoptionofbiogasenergyinTanzaniaandRwandahashelpedinempoweringthesocio-economicstatusparticularlybyenhancingtheincomeofhouseholdsandcreatingjobopportunities.
AnotherstudybyWarnarsandOppenoorth[52]indicatedthatusingbio-slurryleadstoahighercropyieldincrementdespiteitsprod-uctivityeffectvaryingfromcroptocrop.
Itis,however,importanttonotethattheresultsofthecurrentstudyshouldbecalibratedusingexperimentalstudies,suchasfieldtrials,astheestimatesfromsuchobservationalstudiesmaynotbeabletocontrolallun-observedbiaseswhichcouldaffecttherobustnessoftheestimatedresults.
KelebeEnergy,SustainabilityandSociety(2018)8:30Page11of14ConclusionsThecomparisonofenergyexpenditurebetweenbiogasuserandnon-userhouseholdsshowsasubstantialdiffer-ence.
Theaveragemonthlyenergyexpenditureofbiogasuserhouseholdshasbeenreducedby20–36%asaresultofpartiallyswitchingtobiogasenergyparticularlyforlightingandcookingpurposes.
Furthermore,thestudyfindstheexistenceofapositivecropyieldpremiumofroughlyabout1.
5quintal/year/householdasaresultofusingbio-slurryasafertilizerSuchareductioninenergyexpenditureandanincrementincropyieldhaveaposi-tivecontributiontoenhancetherealincomeofhouse-holds.
Thesefindingshaveimportantimplicationsonthefurtherpromotionoffamily-sizedbiogasdigesters.
Thismeansthatbiogastechnologyshouldnotonlybepromotedforthepurposeofsupplyingcleanenergybutalsoforfosteringtheincomeofruralhouseholdsbyre-ducingtheenergyexpenditureandenhancingcropproductivity.
Despitethis,theoveralleffectofabio--slurryapplicationoncropproductivityandsubstitutionofchemicalfertilizerwasnotasmuchasexpectedduetothepoormanagementandknowledgeinbio-slurryutilization.
Theinstalledbiogasunitsareconfrontedbyaninadequateenergyproduction,frequentdamage,andaninadequateinstitutionalsupportformaintenanceandrepairthathin-dersthetransitionfromsolidwoodfuelstobetterenergyfacilitiessuchasbiogas.
Thekeyfactorsthatlimittheex-tensionofthebiogastechnologytopotentialbiogasadoptersarethepresenceoffailedanddamageddigesters,aninadequateplotoflandfordigesterconstructionandthewateravailabilityproblem.
Inthefaceofsuchbarriers,therearestillenablingenvironmentsforthewidespreaduseofthetechnologysuchasascarcityofsolidfuels,ariseinpriceofmodernenergysources,theavailabilityofacheapinputforbiogasproduction,andmulti-faceteduseofthetechnology.
Theleadingagency,NationalBiogasProgrammeofEthiopia,whichisinchargeofbiogaspromotion,shouldensuretheactiveengagementofrelevantagenciessuchasenvironmentalprotection,naturalresourcesmanagement,agriculture,andhealthcareatadistrictandcommunitylevelsinordertoovercomethechallengesfacingthetech-nologyandtorealizeitsmultifacetedbenefits.
Theactorsinvolvedinthisbiogasprogramarealsoadvisedtoquicklyfocusonaddressingthetechnicalandattitudinalbarriershamperingbiogasenergyandbio-slurryutilizations.
Fur-therplotlevelandcrop-specificresearchworkisrecom-mendedtoexplorethecontributionofdomesticbiogastocropproductivityandclimatesmartagriculture.
Endnotes1A"tabia"inthispaperreferstothesmallestadminis-trationunitinTigrainexttoadistrict2Tsimadisalocalunstandardizedmeasurementofsizeoffarmplots(onetsimadisroughlyequivalentto0.
25ha)3EthiopianBirr(ETB),currencyofEthiopia(US$1=27.
2ETBasofDecember,2017exchangerate)AdditionalfileAdditionalfile1:Rawdatacollectedfromsurveyedhouseholdheads.
(XLSX91kb)AbbreviationsEq.
:Equation;ETB:Ethiopianbirr;hh:Household;UNDP:UnitedNationsDevelopmentProgramme;WHO:WordHealthOrganizationAcknowledgementsTheauthorisverygratefultotheMekelleUniversityandPanAfricanUniversityforfundingpartofthedatacollectioncosts.
Theauthorextendshisgratitudetotheenumeratorsandhouseholdswhoparticipatedinthisstudy.
Theauthoristhankfultotheanonymousreviewersandeditorofthejournalfortheirhelpfulandcriticalrecommendationstotheearlierversionofthispaper.
TheauthoralsoextendsappreciationtoMr.
HaftuKahsayforhisinvaluablecontributiontocorrectgrammaticalerrors.
FundingThefundfordatacollectionwasobtainedfromMekelleUniversityandPanAfricanUniversity.
AvailabilityofdataandmaterialsTherawdatahasbeensubmittedonlineasAdditionalfile1.
Authors'contributionsHEdevelopedtheconcept,designedthedatacollectioninstruments,andsuperviseddatacollection.
Inaddition,dataanalysisandtheinterpretationoftheresultsandwritingthismanuscriptwerecarriedoutbythesameauthor.
Theauthoralsoreadandapprovedthefinalmanuscript.
CompetinginterestsTheauthordeclaresthathehasnocompetinginterests.
Publisher'sNoteSpringerNatureremainsneutralwithregardtojurisdictionalclaimsinpublishedmapsandinstitutionalaffiliations.
Table7Effectofbio-slurryapplicationoncropyieldanduptakeofchemicalfertilizer(t-valueinparentheses)MatchingmethodTreatedobservationControlobservationCropyield(ATT)Chemicalfertilizeruptake(ATT)Nearestneighbor50251.
7(1.
5)0.
34(0.
6)Radius47711.
46(1.
87)*0.
22(1.
256)Kernel50711.
56(1.
9)*0.
28(1.
6)Stratification50711.
06(1.
24)0.
255(1.
96)*Denotesvaluessignificantat10%KelebeEnergy,SustainabilityandSociety(2018)8:30Page12of14Received:8February2018Accepted:12September2018References1.
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