ARB Report Final Draft Transmittal Feb 26 2016 · 2017-11-02 · i Evaluation of Dairy Manure Management Practices for Greenhouse Gas Emissions Mitigation in California1 FINAL TECHNICAL

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EvaluationofDairyManureManagementPracticesforGreenhouseGas

EmissionsMitigationinCalifornia1

FINALTECHNICALREPORTtotheStateofCaliforniaAirResourcesBoardContract#14‐456

February26,2016

StephenKaffka,DepartmentofPlantSciences,UniversityofCalifornia,Davis;and

CaliforniaBiomassCollaborative(PrincipalInvestigator);530‐752‐8108;[email protected]

TylerBarzee,DepartmentofBiologicalandAgriculturalEngineering,UniversityofCalifornia,Davis

HamedEl‐Mashad,DepartmentofBiologicalandAgriculturalEngineering,UniversityofCalifornia,Davis

RobWilliams,DepartmentofBiologicalandAgriculturalEngineering,UniversityofCalifornia,DavisandCaliforniaBiomassCollaborative

SteveZicari,DepartmentofBiologicalandAgriculturalEngineering,UniversityofCalifornia,Davis

RuihongZhang,DepartmentofBiologicalandAgriculturalEngineering,UniversityofCalifornia,Davis(Co‐Investigator)

1Photosource:http://manure.ucdavis.edu/Illustrations/Dairy_Lagoons/

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Table of Contents

1. EXECUTIVESUMMARY................................................................................................................................11.1.METHODS.........................................................................................................................................................................11.2.MAINFINDINGS..............................................................................................................................................................21.2.1. SupplyCurveandGHGMitigationCostSummaryCurves..............................................................21.2.2. GHGMitigationScenarioTabularResults.............................................................................................6

1.3.CONCLUSIONS..................................................................................................................................................................71.4.LONGANDSHORTTERMRESEARCHNEEDS..............................................................................................................9

2. INTRODUCTION.........................................................................................................................................122.1.GHGEMISSIONSFROMDAIRYMANUREMANAGEMENTINCALIFORNIA...........................................................122.2.GHGMITIGATIONOPTIONSFROMANAEROBICLAGOONS....................................................................................152.3.REPORTMETHODOLOGY.............................................................................................................................................162.4.LIMITATIONSOFTHISSTUDY.....................................................................................................................................19

3. ANAEROBICDIGESTION..........................................................................................................................213.1.OVERVIEWOFSCENARIOSEVALUATED.....................................................................................................................213.2.DIGESTER‐ENERGYANDTIER1UPGRADEWITHCOVER‐AND‐FLARE:METHODSANDASSUMPTIONS.......223.2.1. EmissionsReductionModeling.................................................................................................................223.2.2. EnergyConversionPerformanceandNOxEmissionAssumptions..........................................233.2.3. SystemCostAssumptions............................................................................................................................24

3.3.GREENHOUSEGASMITIGATION,CUMULATIVECOSTS,ENERGYANDNOXEMISSIONS.....................................283.4.LIMITATIONS.................................................................................................................................................................33

4. CONVERTINGFROMFLUSHTOSCRAPEANDSOLIDMANUREMANAGEMENT....................344.1.CONVERTINGFROMFLUSHTOSCRAPE.....................................................................................................................344.1.1. KeyAssumptionsandOptions...................................................................................................................354.1.2. Costs......................................................................................................................................................................354.1.3. GreenhouseGasEmissionsfromScraping..........................................................................................40

4.2.SCRAPETODRYMANUREMANAGEMENTOPTIONS–DESCRIPTIONANDKEYASSUMPTIONS..........................404.2.1. OpenSolarDrying..........................................................................................................................................414.2.2. ClosedSolarDrying.......................................................................................................................................444.2.3. ForcedEvaporationwithNaturalGasFueledDryers...................................................................444.2.4. Composting........................................................................................................................................................45

4.3.ESTIMATEDSYSTEMCOSTS........................................................................................................................................484.3.1. Opensolardrying...........................................................................................................................................484.3.2. ClosedSolarDrying.......................................................................................................................................494.3.3. ForcedEvaporationUsingNaturalGasFueledDryers.................................................................494.3.4. Composting........................................................................................................................................................50

4.4.GHGMITIGATIONCOSTS.............................................................................................................................................514.5.IMPACTONDAIRYMANAGEMENT..............................................................................................................................534.6.ENVIRONMENTALDISCUSSION...................................................................................................................................544.7.REVENUESANDINCENTIVES.......................................................................................................................................544.8.BARRIERSTOADOPTION.............................................................................................................................................55

5. SOLID/LIQUIDSEPARATION.................................................................................................................565.1.OVERVIEWOFTECHNOLOGYANDADOPTIONSTATUS............................................................................................565.2.KEYASSUMPTIONS.......................................................................................................................................................565.3.COSTS..............................................................................................................................................................................575.4.GREENHOUSEGASMITIGATION..................................................................................................................................585.5.IMPACTONDAIRY.........................................................................................................................................................58

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5.6.ENVIRONMENTALDISCUSSION....................................................................................................................................595.7.REVENUES/INCENTIVES..............................................................................................................................................595.8.BARRIERSTOADOPTION..............................................................................................................................................59

6. LAGOONAERATION..................................................................................................................................606.1.OVERVIEWOFTECHNOLOGYANDADOPTIONSTATUS............................................................................................606.2.KEYASSUMPTIONS.......................................................................................................................................................616.3.COSTS..............................................................................................................................................................................616.4.GREENHOUSEGASMITIGATION..................................................................................................................................626.5.IMPACTONDAIRY.........................................................................................................................................................626.6.ENVIRONMENTALDISCUSSION...................................................................................................................................636.7.REVENUESANDINCENTIVES.......................................................................................................................................636.8.BARRIERSTOADOPTION.............................................................................................................................................64

7. MANUREMANAGEMENT,WATERQUALITY,GHGEMISSIONSANDOTHERENVIRONMENTALEFFECTS.............................................................................................................................657.1OVERVIEWOFMANUREMANAGEMENTISSUES.........................................................................................................657.2THEEFFECTSOFADSYSTEMSONDAIRYMANURE..................................................................................................707.3PROCESSINGOFMANUREANDADDIGESTATE........................................................................................................717.3.1Solid/LiquidSeparation.........................................................................................................................................737.3.2NutrientConcentrationinManuresandADDigestates..........................................................................75

7.4CODIGESTIONOFEXOGENOUSBIOMASSFEEDSTOCKSWITHMANUREINADSYSTEMS.....................................777.5COMPLICATIONSFROMSALTS......................................................................................................................................787.6COSTS...............................................................................................................................................................................797.7WATERUSEIMPLICATIONS.........................................................................................................................................79

8. FUTUREWORKANDRECOMMENDATIONS......................................................................................83

APPENDICES.........................................................................................................................................................86

ABBREVIATIONS...............................................................................................................................................113

REFERENCES.......................................................................................................................................................114

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Table of Tables

Table1.1:ScenarioSummary:MitigationPotentialand10‐yrCost..................................................6Table1.2:CumulativeEnergyandNOxfromAnaerobicDigestionScenarios...............................7Table2.1:CaliforniaDairyandAgricultureSectorGHGEmissions................................................12Table2.2:CADairyManureManagementSystemsShowingGHGEmissionsFactorsand

Emissions...................................................................................................................................................15Table2.3:DairymanuremanagementGHGmitigationscenariosevaluatedinthisreport.17Table2.4:Statewidedairysizedatabaseinformation..........................................................................19Table3.1:DigestertoEnergyandUpgradetoTier1withCover&Flarescenariomatrix...21Table3.2:Keyparametersandresultsfrommethaneproduction/emissionsmodel..........23Table3.3:Conversionefficiencyandpercowenergyproductionbyscenario..........................24Table3.4:NOxemissionfactors......................................................................................................................24Table3.5:Powersystemcostadders............................................................................................................27Table3.6:ComprehensiveDigester‐Energyresults...............................................................................32Table4.1:Summarizedcostsforthreescrapesystemsasmodeled...............................................36Table4.2:MonthlyaverageprecipitationandevaporationdataforBakersfieldandFresno,

CA...................................................................................................................................................................42Table4.3:OpensolardryingCo‐Composterv2amajormodelassumptions.............................43Table4.4:CompostingscenarioCo‐Composterv2amajormodelassumptions........................46Table4.5:OpenSolarDryingestimatedpadsizesandcostsfor6and8monthscenarios..48Table4.6:ClosedSolarDryingscenariocostssummary......................................................................49Table4.7:ForcedEvaporationscenariocostsummaryusingnaturalgasfueleddryers......49Table4.8:Compostingscenariocostssummary......................................................................................50Table4.9:Mitigationpotentialand10‐yearcumulativecostsfordairiesover300and2000

headonly....................................................................................................................................................53Table5.1:Averagemechanicalsolid/liquidseparationcostsandemissions.............................57Table5.2:AverageemissionreductioncostsforSolid‐LiquidSeparationatdifferentsized

dairies..........................................................................................................................................................58Table6.1:Aerationscenarioestimatedsystemcosts............................................................................62Table6.2:AerationGHGmitigationpotentialsforlowandhigheffectivenessscenarios.....62Table7.1:Comparisonoftechnologiesformanuresolidsprocessing...........................................74Table7.2:Energyconsumptionandtotalcostsforammoniarecovery........................................76Table0.1:Relationshipsbetweendissolvedoxygen(DO),redoxpotential,andbiochemical

reactions.....................................................................................................................................................88

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Table of Figures

Figure1‐1:ManureManagementMitigationCostSupplyCurves‐FullIndustryTreatment‐Summary........................................................................................................................................................3

Figure1‐2:ManureManagementMitigationCostSupplyCurves‐FullIndustryTreatment‐Detailed..........................................................................................................................................................4

Figure1‐3:ManureManagementMitigationCostSupplyCurves–Largest225Dairies.........5Figure2‐1:TypicalDairyManureManagementHandlingOptions.................................................13Figure2‐2:Dairysizesandnumbersincludedinstatewidefullreportdatabaseused.........19Figure3‐1:Mitigationcostcurvevs.no.ofmilkcowsonadairy,CoverandFlarescenario25Figure3‐2:Digesterandcover‐and‐flareinstalledcostcurves........................................................26Figure3‐3:Highestandlowestmitigationcostcurves;digester‐electricityandcoverand

flare...............................................................................................................................................................28Figure3‐4:CNGscenarios:Highestandlowestmitigationcostcurves........................................29Figure3‐5:AnaerobicDigestionMitigationcostsupplycurve,largesttosmallestdairies

($/MgCO2eqvs.CumulativeMitigation).......................................................................................30Figure3‐6:Annualmitigationvs.10‐yr.mitigationcost‐2000‐cowandlargerdairies........31Figure4‐1:Estimatedtotalannualizedcostsfordifferentscrapingtechnologies...................36Figure4‐2:Averageestimatedtotalannualizedcostsforallscrapingsystemswithdifferent

loanpayoffperiods................................................................................................................................36Figure4‐3:Anexampleofavacuummanurecollectiontruck..........................................................37Figure4‐4:Exampleofanautomatedmechanicalscrapingsystem...............................................38Figure4‐5:Exampleschematicofanautomatedmechanicalscrapersystem...........................38Figure4‐6:Exampleofarubberfrontmountedscraperaddedtoaskid‐steerloader..........39Figure4‐7:Averageestimatedoperationaldirectgreenhousegasemissionsfromthree

differentscrapingstrategies..............................................................................................................40Figure4‐8:Totalannualizedsystemcostsforscrapemanuremanagementscenarios.........51Figure4‐9:GHGmitigationcostsforscrapescenarios.........................................................................52Figure4‐10:GHGmitigationpotentialandcostsforscrapescenarios.........................................52Figure5‐1:Estimatedannualizedcostsformechanicalsolidliquidseparatorsforfarmsof

differentsize.............................................................................................................................................57Figure7‐1:MajorComponentsoftheNitrogenCycleinaForageCropFertilizedwithDairy

Manure........................................................................................................................................................66Figure7‐2:Nmineralizationandcropuptake..........................................................................................67Figure7‐3:Nutrientuptakepotentialvarieswithtimeofyearandcrop.....................................69Figure7‐4:PotentialManureProcessingOptions..................................................................................72Figure7‐5:Flowchartofanintegratedsystemfortheproductionofbiogasandfertilizers

fromorganicwastes..............................................................................................................................77Figure7‐6:Onemethodofcoolingcowswhiletheyfeed....................................................................80Figure7‐7:Anexampleofmilkingparlorflushing.................................................................................81

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1. Executive Summary Theobjectiveofthisresearchprojectistodevelopinformationtohelpinformpoliciestopromotereductionofgreenhousegas(GHG)emissionsfromdairymanuremanagementinCalifornia.Thisresearch(1)describesandevaluatesmanuremanagementtechnologyoptionscurrentlyorpotentiallyavailabletodairyfarmsinCalifornia,(2)comparestechnologiesbasedonGHGemissionsreductionpotential,costsandlimitations,and(3)estimatesGHGmitigationcost(orsupply)curvesforvariousmanuremanagementstrategiesifappliedacrosslargefractionsoftheCaliforniadairyindustry.Airandwaterqualityimplicationsarediscussedbasedonlimiteddataandothertechnicalstudiesavailable,especiallythosefocusedonCaliforniaconditions.

1.1. Methods Workfocusedonmitigatingemissionsfromanaerobiclagoonmanurestoragesystems(lagoons)becausetheyaccountforabout80%ofmethaneemissionsfromCaliforniadairymanure.2Methaneemissionsfromlagoonstoragesystemscanbedecreasedbyreducingtheamountormodifyinganaerobicstorage(i.e.solidsseparationanddiversionfromlagoon,modifyingdominantflushcollectiontomanurescrapingwithdrying/compostingorotherlagoondiversion,etc.),aeratingthelagoon(toreduceoreliminateanaerobicconditions),coveringthelagoon(lagoondigester)andcollectingandburningthemethane(flareorenergyrecovery),oraddinganengineeredanaerobicdigestersystemtotreatthemanureandrecovermethane.Thespecificscenariosinvestigatedhereare:

• UpgradinglagoontoTier1construction3andcoveringandflaringgas• Anaerobicdigestionwithenergyrecovery• Convertingflushtoscrapesystems,with

– Drying(Opensolar,closedsolar,andforceddrying)– Composting(Withbulkingagentandincombinationwithopensolardrying

scenarios)• Solids/liquidseparationbeforeexistingflushlagoonstorage• Lagoonaeration

2Californiadairiescontributeapproximately4%ofthestate’sGHGemissions,mostlyasmethanefromentericfermentationandmanuremanagement.Manuremanagementcontributesabout60%ofdairymethane.Anaerobiclagoonsaccountfor80%ofmanuremanagementGHGemissions(CARB,2014)3“Tier1:Aponddesignedtoconsistofadoublelinerconstructedwith60‐milhighdensitypolyethyleneormaterialofequivalentdurabilitywithaleachatecollectionandremovalsystem(constructedinaccordancewithSection20340ofTitle27)betweenthetwoliners..”http://www.waterboards.ca.gov/rwqcb5/board_decisions/tentative_orders/0705/dairies/dairies‐general‐info‐att1.pdf

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Costsandmitigationpotentialsweredevelopedforeachscenariobasedon“model”dairiesthatrangedinsizefrom300to10,000milkingcows.Manuremanagementata“model”orrepresentativedairybeforemitigationincludedflushingtolagoonstorage,whereabout60%ofadultcowmanurewasdeposited.4Conservativecostandperformanceassumptionsweregenerallychosenand,wherepossible,basedonrecentCaliforniasystemcosts(i.e.,recentliteratureandinformationonCaliforniadigestercosts).ThescenariocostswerethenintegratedwithaCaliforniadairyinventorycompiledfromreportsprovidedbytheCentralValleyandSantaAnaRegionalWaterQualityControlBoardsandusedtoapproximatestatewide“mitigationcostsupplycurves”forthegivendistributionofdairysizes5,orotherwisesummedtoestimateindustry‐widemitigationandtotalten‐yeartreatmentcosts.Methaneandnitrousoxidewereassignedrespectiveglobalwarmingpotentials(GWPs)of25and298timesthatofcarbondioxide(100‐yeartimescale)tofacilitateGHGassessmentonacarbondioxideequivalent(CO2eq)basis.Individualscenariocostsandmitigationpotentialsestimatedformodeldairysizesarenotintendedtoapplyforanyindividualdairyoruniformlytoalldairiesofaparticularsize.

1.2. Main Findings Resultsfromapplyingeachscenariotoessentiallythefullindustry(alldairieswith≥300milkcows,~1.65millioncowstotal)andthelargest225dairies(≥2000cowsperdairy;~800,000cowstotal)aredescribedbelow.

1.2.1. Supply Curve and GHG Mitigation Cost Summary Curves ArangeofmitigationcostsupplycurvesgroupedbyscenariotypeappearsinFigure1‐1andFigure1‐2presentsdetailedindividualscenariocurves,forindustry‐widemitigationandtreatmentcosts.Figure1‐3detailsestimatedmitigationcostsupplycurvesforthelargest225dairiesonly.TherangesexpressedinFigure1‐1aregeneratedbyselectingthehighestandlowestmitigationcurvesfordifferentscenariotypesasestimatedinFigure1‐2.Scenarioswhereonlyasinglecostcurvewasestimated(i.e.UpgradeLagoonwithCoverandFlare,andSolid‐LiquidSeparation)aredisplayedasindividualcurves,howeveritshouldbenotedthatallcostestimatesarepreliminarywithasignificantdegreeofuncertainty.

4Thismimicstotalstatewidedairymanuremanagementestimates.5Theinventorylistsmorethan1200dairiesincludingmilkcowpopulationateachdairy.1.66millionadultcows(orabout94%ofCAadultdairycows)areaccountedforintheinventory.

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Figure1‐1:ManureManagementMitigationCostSupplyCurves‐FullIndustryTreatment‐Summary

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Figure1‐2:ManureManagementMitigationCostSupplyCurves‐FullIndustryTreatment‐Detailed(SeeTable1.1,1.2andtextforscenariodetails)

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Figure1‐3:ManureManagementMitigationCostSupplyCurves–Largest225Dairies(SeeTables1.1,1.2andtextforscenariodetails)

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1.2.2. GHG Mitigation Scenario Tabular Results ResultsforfullindustryandlargestdairytreatmentsareshowninTable1.1.FullIndustryTreatmentForthefullindustrytreatment(1.66millionproducinganddrycows),mitigationpotentialrangesfrom1.2TgCO2eq/y6fortheSolid/LiquidSeparationscenario,upto8.3TgCO2eq/yforaTank/PlugFlowDigesterscenario.Averagemitigationcostsrangedfrom$35/MgCO2eq(Tier1LagoonUpgradewithCoverandFlare)to$232/MgCO2eqfortheScrapetoClosedSolarDryingscenario.Total10‐yearcostsrangedfrom$600million(Solid/LiquidSeparation)to$10billion(ScrapetoClosedSolarDrying). Largest225DairiesTen‐yeartreatmentcostsforthelargest225dairies(≥2000cows/dairy)aremuchlessthanhalfthatforthefullindustryduemostlytoeconomiesofscale(lowercostpercow,orpertonneatlargerdairies).Theyrangefrom$200millionto$3.7billion(Table1.1).Mitigationpercowbyscenarioisroughlyconstantinourassumptionssomitigationpotentialsforthelargest225dairiesareroughlyhalfofthefullindustrytreatmentcaseandrangefrom0.6to4.1TgCO2eq/y(Table1.1).Averagepertonnemitigationcostforthistreatmentsizerangesfrom$29to$183.Table1.1:ScenarioSummary:MitigationPotentialand10‐yrCost

Scenario Description

≥ 300 milk cows/dairy or 1110 dairies

(~1.65 million cows)

≥ 2000 milk cows/dairy or largest 225 dairies (~800,000 cows)

Mitigation Potential

(Tg/y)

Average Cost

($/Mg)

10-yr cost (Billion $)


(Tg/y)

Average Cost

($/Mg)

10-yr cost (Billion $)

Scrape to Open Solar Drying (6 mo.) 2.2 71 $1.6 1.1 54 $0.6 Scrape to Open Solar Drying (8 mo.) 3.0 82 $2.4 1.4 69 $1.0 Scrape to Closed Solar Drying (12 mo.) 4.3 232 $10.0 2.1 179 $3.7 Scrape to Forced Evap.(Nat.Gas Fuel) (12 mo.) 5.4 116 $6.3 2.6 98 $2.6 Scrape to Compost with Bulking (12 mo.) 4.9 195 $9.5 2.4 183 $4.3 Aeration (Low Effectiveness) 4.1 68 $2.7 2.0 65 $1.3 Aeration (High Effectiveness) 7.3 38 $2.7 3.5 36 $1.3 Solid/Liquid Separation 1.2 55 $0.6 0.6 39 $0.2

Tier 1 Upgrade with Cover and Flare 8.1 35 $2.8 4.0 29 $1.1

Lagoon Digester - Uncovered Effluent Pond*

Recip. Engine

7.3

41 $3.0

3.5

31 $1.1 Microturbine 46 $3.4 36 $1.3 Fuel Cell 59 $4.3 45 $1.6 RNG fuel 54 $3.9 33 $1.2

Tank / Plug Flow Digester -Covered Effluent Pond**

Recip. Engine

8.3

55 $4.6

4.1

41 $1.7 Microturbine 60 $5.0 46 $1.9 Fuel Cell 72 $6.0 55 $2.2 RNG fuel 65 $5.5 42 $1.7

*Representslowestcost/lowestmitigationpotentialofDigesterScenarios**Representshighestcost&mitigationpotentialofDigesterScenarios

6Mgmeansmetrictonne(Mg=1000kg=1metrictonne).Tg=millionMg=millionmetrictonnes.

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CumulativeenergyandNOxemissionpotentialsforthehighest&lowestcostDigester‐to‐EnergyscenariosandtheTier1CoverandFlarescenarioappearinTable1.2.Table1.2:CumulativeEnergyandNOxfromAnaerobicDigestionScenarios

Scenario Description



≥ 2000 milk cows/dairy or largest 225 dairies

(~800,000 cows)

Energy Potential (MW)

NOx (tons/y)

Energy Potential (MW)

NOx (tons/y)

Lagoon Digester - Uncovered Effluent. Pond

Recip. Engine 190 382 92 186 Microturbine 145 153 71 74

Fuel Cell 316 28 154 13

RNG fuel (million gde/y)

Tailgas flare (tons NOx)

(million gde/y)

Tailgas flare (tons NOx)

93 71 45.1 34.5

(MW) NOx

(tons/y) (MW) NOx (tons/y)

Tank / Plug Flow Digester -Covered Effluent Pond

Recip. Engine 222 447 108 217 Microturbine 170 179 83 87

Fuel Cell 370 32 180 16

RNG fuel (million gde/y)

(tons/y) (million gde/y)

(tons/y)

108 83 52.7 40.3

1.3. Conclusions Thisreportisafirstattemptatquantifyingmitigationcostsforawiderangeofcomplexanddynamicmanuremanagementscenarios.TheresultsofthisworkprovideabasisforestimatingexpensesformethanereducingstrategiesformanuremanagementonCaliforniadairies.Theaspectmostusefulforpolicymakersmaybetocomparetheexpectedrangesofcostsassociatedwitheachmanuremanagementstrategyandtheexpectedmitigationpotential.However,itshouldbereiteratedthattheestimatedcostsarenotintendedtoberepresentativeforanyspecificdairy.Furtheranalysisandinvestigationintomanyoftheassumptionsusedineachmodelisneeded.Additional,researchforimprovedmodellingandquantitativemeasurementisneededinmanyareastoaddressmodelandparameteruncertaintiesandsupportpromisingbutlessdevelopedtechnologies.Specificexamplesoftheseneedsarediscussedforeachscenario,althoughtheyarenotcompleteorinclusive.

Mitigationpotentialsrangedfrom1.2to8.3TgCO2eq/yifappliedtoessentiallythefullindustryand0.6‐4.1TgCO2eq/yfortreatmentatthelargest225dairies.

Averagemitigationcostsrangedfrom$35to$232Mg/TgCO2eqamongscenariosfor

thefullindustrytreatmentcaseand$29to$183Mg/TgCO2eqforthelargest225dairies.Thesecosts(Figure1‐2andFigure1‐3)areestimateswithlikely±30%uncertainty,thoughwehavenotcalculateduncertaintiesnorconductedasensitivityanalysis.

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ScenarioswiththelowestaveragemitigationcostswereUpgradetoTier1Lagoon

withCoverandFlare,Aeration(HighEffectivenessassumption)andtheTier1LagoonDigesterwithUncoveredEffluentPondfuelingaReciprocatingEngine.

ThehighestmitigationcostscenarioswereallConversiontoScrapewith;a)

CoveredSolarDrying,b)CompostwithaBulkingAgentandc)ForcedDryingUsingNaturalGas.

DigesterScenariosDigestersoffersignificantpotentialforGHGreductions,areproventechnologies(thoughnotnecessarilyeconomicinCalifornia),andcouldbeimplementedwithmoderatechangestomanurehandlinganddairyoperation.Mitigationcostsaresensitivetoassumptionswhichmaybeincorrect,thoughmorerecent(andhigher)installedcostvalueswereusedherethaninearlierstudies.DairydigestershavehadadifficultpathinCalifornia.Comparativelyfewareinexistenceandseveralhaveceasedoperation.Theyhaveexperiencedissueswithutilityconnectivity(delays,unexpectedorhighcosts),permittingdelays,higherthanexpectedoperatingcostsandotherissues.ConversiontoScrapewithDrying/CompostingConversionstoincreasedscrapedmanurecollectionwithvariousdryingandcompostingalternativesgenerallyhavehigherGHGmitigationcoststhanthedigesterscenarios.MajorimpactstoadairyoperationshiftingtoScrape‐and‐Drymanuremanagementincludeincreasedoperatingcostsforlaborandequipmenttomanagefreshmanureslurry,solidandbulkingmaterial,andincreasedcostsrelatedforsolidmanureapplicationcomparedtoconveyanceandapplicationthroughlagoondischarge.SolidsSeparationSolidsseparationpriortosendingresultingliquidstoalagoonoffersmoderatemitigationpotentialatmoderatemitigationcost, thoughsaleofsolidsascompostoruseasbeddingmayimprovetheeconomicsofsolidseparationsystems.SolidseparationoccursonmanyCAdairiesbutthescaleofitsuseandpotentialforfurtherGHGmitigationareuncertain.AerationAeratedlagoonscouldhavemoderatetohighmitigationpotentialandcouldbeimplementedwithminortomoderateimpactsonflushdairyoperation.ActualperformanceishighlyuncertainduetolimitedinformationaboutthesesystemsondairiesforpurposesofGHGreduction.Odor,hydrogensulfide,VOCsandammoniaemissionstheoreticallyshouldbereducedwithefficientaeration;however,theiremissionscouldbeincreasedifinefficientaerationoroverloadingoccurs.AerationcouldreducetheBODinwastewater.Itcanalsoproducenitratethatmayleachwithpotentialgroundandsurfacewatercontamination.AerationcouldalsocouldincreaseemissionsofammoniaandNOxandreducetheemissionsofmethane.

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Toachieveemissionreductiongoals,aerationsystemswouldrequireacarefulbalancebetweencreatinganoxidizingenvironmenttoreducemethaneemissions,whileavoidingsignificantnitrification(N2Oemissions).NitrogenemissionsasammoniaorotherNOxcompoundsmayalsobesignificantandcompoundlocalairqualityconditions.Ifsludgeaccumulationoccurs,itcanbealargesourceofVSthatneedstobecarefullymanagedsoasnottoallowanaerobicdecompositioninsubsequentmanagementprocesses.Manuremanagement,waterquality,GHGemissions,andotherenvironmentaleffects

Manurehandlingsystemshavebeendesignedtofacilitatethehandlingoflarge

quantitiesofanimalwastescheaplyandefficiently;GHGemissionreductions(Methane,nitrousoxide)werenotcommonlypartofdesigncriteria.

Manurehandlingsystemsinfluencetheformandbehaviorofnutrientspresentinrawmanure,especiallyN,andGHGemissionsassociatedwithmanure.

Changesinmanurehandlingsystemstomitigatemethanelosswillalsoinfluencenutrientretentionorloss,andinfluencethevalueofmanureasafertilizer.

InsomepartsofCaliforniawherelargenumbersofdairyfarmsarelocated,nitrateNlossestogroundwaterexceedgroundwaterqualitystandards.

Manureisavaluablebutdifficulttomanagesourceforcropnutrients.OrganicallyboundNandothernutrientsinmanurearesubjecttopoorlycontrolledtransformationprocesseswhenappliedtocropsthatmaketimelycorrelationofnutrientavailabilitywithcropuptakedifficult.

Energyrecoverysystemsusingmanureasafeedstockmayprovideaneconomicbasisforfertilizerby‐productcreationfrommanureandtheiroff‐farmuseorsale,helpingtomitigatesurplusnutrientapplicationtocropswhilereducingfugitivemethaneemissionsfrommanurestorageandhandling.

1.4. Long and Short Term Research Needs GeneralManureManagement

EffortisneededtobetterunderstandandquantifythetrendsinmanuremanagementonCaliforniadairyfarms.Itwouldbeespeciallyhelpfultounderstandhowmanuremanagementchangeswithfarmsizeorlocation.

Morepeerreviewedstudiesofemissionsfromactualfarmsandtheassociatedcorrelationtomanuremanagementstrategyareneeded.ThiswouldimproveprecisionofMCFfactorsandothervariablesusedinGHGprotocolandaccountingtools.

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Theagronomic(cropproduction)andenvironmentalconsequences(emissionstoairandsurfaceandgroundwater)ofpotentiallylarge‐scalechangesinmanuremanagementstrategiesonCaliforniadairyfarmsrequirefurthermeasurementandmodeling.

AnaerobicDigestion

Althoughthepracticeofanaerobicdigestioniswelldemonstratedandunderstood,questionsremainrelatedtomethaneemissionsincludingimpactsofeffluentponds(coveredoruncovered)andfugitivemethanefrombiogascollectionandenergysystems(methaneleaks).Academicinquiryandmeasurementsofthistypeonactual,representativefarmswouldgreatlyimprovetheestimates.

Thereisaneedtoimproveestimatesofcapitalandoperatingandmaintenancecostsfordairybioenergysystems.Theliteratureingeneralappearstounderestimatethesecosts.Ifpublicgrantsorotherfinancialincentivesareusedtohelpdefrayinvestmentcosts,thenthereshouldbeamechanisminthecontracttomonitortheprojectandgatheractualenergyperformanceandoperatingcostdata(andunforeseencapitalcostsnotknownattimeofproposal).Improvedknowledgeofrealcostsandperformancecanbeusedtoinformpolicyandcalibratefuturepublicgrantprograms.

Researchisneededonthetechnologyfortreatingdigestereffluents(digestate)toconvertitnewfertilizerproductsandonitsuseslikefertilizersubstitutes,soilamendments,andotherproducts.

ResearchonGHGimpactsandlife‐cycleassessmentsofdairydigestatesandnewfertilizerby‐productsisneeded.

TransitioningtoScrapeSystemswithDryingandComposting

Costdatafrommorefarmsthatsuccessfullyuseorhavetransitionedtoscrapemanuremanagementwouldimprovemodelingofthisscenario.

Investigationofwaterqualityandirrigationstrategyimpactsduetotransitiontoscapeisneeded.

AbetterunderstandingoftheGHGconsequencesandotheremissionsfromscrapedmanureisneeded,particularlywhetherscrapedandprocessedmanurebehavesasanaerobicslurry,forwhatduration,andwhatappropriateMCFshouldbeapplied.

Thedryingandcompostscenariossufferfromalackofdataoneffectsonairandwaterqualityunderfarmconditions.

Forcomposting,abetterunderstandingofthecurrentandfuturemarketandvalue

forcompostedproductsandbulkingagentsneededforon‐farmcompostingwouldimprovecostestimates.Aswiththeanaerobicdigestionscenarios,significant

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nutrientsmaybeaccumulatedthiswayandpotentialuseasfertilizersandsoilorganicmatteramendmentsmaybepossible.

SolidLiquidSeparation

Anaccurate,currentestimateofhowmuchsolid/liquidseparationiscurrentlypracticedonCaliforniadairiesandwhatadditionalfractionofmanurecanbetargetedwiththistechniqueisneeded.

Abetterunderstandingofthecostsassociatedwithsolidliquidseparationsystemsisneeded.TherearemoreinstancesofthistechnologyalreadyadoptedonCAdairiescomparedtootherscenarios.

Researchisneededtobetterdeterminemethaneconversionfactorsassociatedwithdifferentsizedsolidsforbetteremissionsreductionsestimates.

LagoonAeration

AerationisastandardprocessusedinwastewatertreatmentplantsforBOD(BiologicalOxygenDemand)reductionbutthereislittletechnicalliteratureontheapplicationofthistechnologytodairymanurelagoons.Generally,ithasbeeninvestigatedforodorcontrolinmanurelagoons,andsomeauthorsconcludethatitisnoteffectiveortoocostly.However,thetheoreticalpotentialforGHGmitigationexistsandresultsinthisreportindicateitmaybeacostcompetitive.Researchonaeratedlagooncost,GHGreductioneffectiveness,andeffectsonemissionsisneededbeforeadvocatingthesetechniques.Thereisaneedtounderstandthepotentialeffectsofeffluentsfromaeratedlagoonsonthechemicalandphysicalcharacteristicsofmanuresandonsurfaceandgroundwatercontamination.Thisincludesmonitoringofthefugitivegasesfromaeratedlagoonandtheireffectsonairandwatercontamination.

Wateruseimplications

Reductionsinfreshwateruseondairiesmaybepossiblewithanaerobicdigestionorscrapingscenarios,primarilyfromminimizingevaporativelosses.Butlogicallysavingsappearunlikelytobelarge.Combined,boththedairyfacilityandassociatedcroppingsystemmayhavefreshwaterneedsdominatedquantitativelybycropirrigationrequirements.Reductionsinavailablewastewatervolumesapplieddirectlytofieldslikelyrequirecorrespondingincreasesinirrigationwaterfromirrigationdistrictsourcesorwells.Additionalresearchandevaluationareneededtoquantifytowhatextentwatermightbesavedbychangingthedominantformofmanuremanagementondairies.

12

2. Introduction AssemblyBill32(AB32),theCaliforniaGlobalWarmingSolutionsActof2006,declaresthatglobalwarmingposesaseriousthreattoCaliforniaandchargestheCaliforniaAirResourcesBoard(ARB)with“monitoringandregulatingsourcesofemissionsofgreenhousegases(GHGs)inordertoreduceemissions.”AB32providedinitialdirectiononcreatingacomprehensivemulti‐yearprogramtolimitCalifornia’sgreenhousegas(GHG)emissionsat1990levelsby2020andinitiatethetransformationsrequiredtoachievetheState’slong‐rangeclimateobjectives.TheARBdevelopedascopingplanandsetforthrecommendationsaimedatreducingGHGemissionsfromsixmajorfocusareas:energy,transportation,agriculture,water,wastemanagement,andnaturalandworkinglands.SpecificrecommendationsforagricultureincludedthedevelopmentofaMethaneCaptureorAbatementStandardandestablishmentofamulti‐agencyworkinggroupfocusedonpromotingdairydigesterresearchanddevelopmentrecommendations.MorerecentlyaspartofatargetedstrategytoaddresssomeofthemostpotentGHGs,SB605(Lara,Chapter523,Statutesof2014)directstheARBtodevelopastrategy,byJanuary2016,toreduceemissionsofshort‐livedclimatepollutants(SLCP).TheARBhasreleasedaninitialSLCPreductionconceptpaperhighlightingtheimportanceofreducingmethane,fluorinatedgases,blackcarbon,andtroposphericozone,aswellaspossibleavenuesfordoingso(CARB2015).Significantlycuttingmethanefromdairiesisanintegralelement.Inordertostructureeffectivepolicyandincentiveprograms,additionalinformationandshort‐termresearchisneededtohelpdevelopasustainable,well‐informed,agriculturalGHGmitigationplan.Thisresearchsupportstheseeffortsbyevaluatingpotentialoptionsspecifictomethanereductionfromdairymanureanaerobiclagoons.

2.1. GHG Emissions from Dairy Manure Management in California InCalifornia,GHGemissionsfromdairylivestockareestimatedtobe19.6TgCO2eqperyear,accountingfor4.3%ofallCaliforniaGHGemissionsand57%ofthosefromCaliforniaAgriculture(Table2.1).GHGemissionsfromdairymanureaccountsfor11.4TgCO2eq/yr,ofwhich9.04Tgareattributedtoemissionsfromanaerobiclagoonmanurestorage,whicharepredominantlymethane.Table2.1:CaliforniaDairyandAgricultureSectorGHGEmissions

Activity 2012 GHG Emissions (Tg CO2eq)

Fraction of State Total

(%) Dairy Manure - Anaerobic Lagoon 9.04 2.0 Dairy Manure – Other 2.36 0.5 Dairy Enteric Fermentation 8.22 1.8 Dairy Total 19.6 4.3

All Agriculture 34.1 7.4 State Total GHG emissions are ~459 Tg Co2eq. *Source: http://www.arb.ca.gov/cc/inventory/data/data.htm ,March2014update.Accessed Feb., 2015

13

Thereareanestimated1,780,000adultdairycattleinthestatewithanadditional800,000heifers(younganimalsnotyetbeingmilked)(Table2.2)distributedonmorethan1600registereddairies(CDFA,2013).Approximately80%oftheadultcowsarelactating(milking)withtheremaining20%dry(betweenlactations)atanytimeduringtheyear.Foreverypoundofmilkproduced,alactatingdairycowmightalsobeexpectedtoproduceover1.7‐poundsofmanureandurine(ASABE,2005).Manureasexcretedfrombothadultcowsandheifersisgenerallyaround13%solidscontentwithaslurry‐likeconsistencysimilartoamilkshake.Dairymanurecanbemanagedonfarmsinseveralwaysandchangesconsistencywiththeadditionofwater,othersolids,orifallowedtodryordehydrate.Figure2‐1illustratesmanyofthemanurehandlingoptionspracticedonarepresentativedairy,whichgenerallyfallintosolid‐orliquid‐manuremanagementcategories.

Figure2‐1:TypicalDairyManureManagementHandlingOptions.

AdaptedfromFigure9‐3ofAWMFH(USEPA,1992)http://directives.sc.egov.usda.gov/OpenNonWebContent.aspx?content=31493.wba

(Slurrymanurefromfreestallbarnandanaerobicdigesteradded)Asshowninthefigureabove,manuremanagementsystemsaremulti‐facetedandmightbedefinedbyacombinationofseveralelementsincludinganimaltype(lactating,dry,heifer,calf,etc.),housing(milkingcenter,freestallbarn,corral,pasture,etc.),collectionsystem(flush,scrape,deep‐pit,etc.),andoneormoreprocessingorstoragesystem(solidsseparation,solidorliquidstorages,anaerobicdigestion,aerobictreatment,composting,etc.).Solidandliquidmanureproductsareprimarilyreusedfornutrientandwaterrecoveryon‐farmorinmostlylocalagriculturalcroppingsystem.Biodegradationoforganicmaterialoccursinnatureprincipallythroughtheactionofeitheraerobicoranaerobicmicroorganisms.Aerobically,completeoxidationofcarbonaceous

14

organicmaterialresultsintheproductionofcarbondioxide(CO2)andwater(H2O).Intheabsenceofoxygen,anaerobicmicroorganismsdegradetheorganicmatterwithultimateproductsbeingCO2andmethane(CH4)andsomebiomassdegradesveryslowlyorincompletely.Inorganicnitrogencanbebiologicallyassimilatedintoorganicnitrogenoroxidizedtonitratesunderaerobicconditions,andphosphates,sulfates,andsomeammoniaorvolatileorganiccompounds(VOC’s)mayalsobeproduced.Anaerobically,ammonia,VOC’sandhydrogensulfidemaybeproducedandnitratescanbedenitrifiedtonitrousoxide(N2O),apotentgreenhousegas.AdditionalinformationonthecomplexbiologicaltransformationsoccurringinaerobicandanaerobicsystemsisprovidedinAppendix2.1.TheIntergovernmentalPanelonClimateChange(IPCC)hasestablisheddefinitionsforthepredominantmanuremanagementsystems(Appendix2.2)inordertostandardizeGHGquantificationmethodology(IPCC,2006).GHGemissionsfromdairymanuresystemsareestimatedannuallyinCaliforniabytheAirResourcesBoardandgenerallyfollowUSEPAandIPCCmethodsandsources(CARB,2014).Formethane,thesemethodsestimatevolatilesolids(VS)excretionvaluesforclassesofdairycowsandapplyanaveragecalculatedmethaneemissionfactor(MCF)toanassumedtheoreticalmaximumformajortypesofmanuremanagementsystems.Similarly,fornitrousoxide(N2O),emissionsfactorsareappliedbasedonnitrogencontentinthemanureforthreecategories;1)directemissions,2)othervolatilizedN‐emissions,and3)emissionsfromrunoff/leachedfractions(Table2.2).Methaneandnitrousoxideareassignedrespectiveglobalwarmingpotentials(GWPs)of25and298timesthatofcarbondioxide(100‐yeartimescale)tofacilitateGHGassessmentonacarbondioxideequivalent(CO2eq)basis.ThemanuremanagementinformationdescribedinTable2.2reflectsthecurrentassumedcownumbers,distributionofmanureinvariousmanagementsystems,andmethaneandnitrousoxideemissionsestimatesgiventhestatedemissionsfactors.InCalifornia,thefollowingsystemspredominate:

UncoveredAnaerobicLagoons:Designedforliquidstorageandwastestabilizationwithstoragetimesofseveralmonthstoayearormore.Lagoonwater(supernatant)istypicallyrecycledtoflushbarnareasorirrigateandfertilizefields.

Liquid/Slurry:Manureisstoredasexcretedorwithminimaladditionofwaterintanksorearthenpondsusuallyforperiodsofaboutamonth.

SolidStorage:Storageofmanure,usuallyforseveralmonths,inunconfinedpilesorstacks.Manureisabletobestackedduetothepresenceofasufficientamountofbeddingmaterialorlossofmoisturebyevaporation.

DailySpread:Manureisroutinelyremovedandappliedtocroplandorpasturewithin24hoursofexcretion.

DryLot:Apavedorunpavedopenconfinementareaswithlittlevegetativecoverwhereaccumulatingmanuremayberemovedperiodically.

15

Anaerobicdigestion,pasture,anddeep‐pitmanagementtypesarealsoaccountedforwithsmallmagnitudes(Table2.2).Asreiteratedagainbelow,anaerobiclagoonstorageconstitutesalmost80%oftheassumedGHGemissionsfromdairymanuremanagement,followedbyliquidslurrystorage,andtoalesserextentheiferdrylotmanure,accountingforacumulativetotalofalmost98%ofdairymanureemissions.

Table2.2:CADairyManureManagementSystemsShowingGHGEmissionsFactorsandEmissions

Source: http://www.arb.ca.gov/cc/inventory/data/data.htm , March 2014 update, accessed Feb., 2015: year 2012 Data (most recent).

2.2. GHG Mitigation Options from Anaerobic Lagoons Methaneemissionsfromlagoonstoragesystemscanbereducedbychangingstorageconditions,thedurationofstorageorreducingtheamountofmanureinanaerobicstorageand/orcapturinganddestroyingmethaneproducedbyanaerobicsystems.Avenuesfordiversionmightincludemodifyingexistingcollectionandprocessingmethods(i.e.increasedvolatilesolidsseparationanddiversionfromlagoons,modifiedmanurecollectionsuchasscrapingfollowedbydrying/compostingorotherlagoondiversion,etc.)oraeratingthelagoontoeliminatetheanaerobiccondition.Systemsthatcapturemethanemightinvolvecoveringorbuildinganewlagoon(lagoondigester)oraddinganengineereddigestersystemtotreatthemanureandrecovermethane,whichcanbeburnedfordestructionorenergyrecovery(inaflare,boiler,engine,etc.),orupgradedforalternativeuse(i.e.compressedrenewablenaturalgas(RNG)vehiclefuel,industrialfeedstock,etc.).Severaloftheseoptionshavebeendiscussedintheliterature.Gloy(2011)estimatedmitigationcosts(offsetprices)atUSdairiesusinganaerobicdigestioninplaceofanaerobic

Livestock Group Number of

cowsRelative Fraction

MCFDirect

N20Volatile

Fraction-N*Runoff

Fraction-N**GHG's

from CH4

GHG's from N2O

GHG's Total

Management System (% of cows) (fraction)[g-N20/

g-N](fraction) (fraction)

[Tg

CO2e/yr]

[Tg

CO2e/yr]

[Tg

CO2e/yr]

Dairy Cows

Anaerobic Lagoon 1,035,710 58.2% 0.748 0 0.43 0.008 8.71 0.33 9.04

Liquid/Slurry 359,444 20.2% 0.332 0.005 0.26 0.008 1.34 0.2 1.55

Daily Spread 187,833 10.6% 0.005 0 0.10 0 0.01 0.01 0.02

Solid Storage 162,001 9.1% 0.04 0.005 0.27 0 0.07 0.09 0.16

Anaerobic Digestion 21,221 1.2% 0.181 0 0.43 0.008 0.04 0.01 0.05

Pasture 11,948 0.7% 0.015 0 0 0 0 0 0

Deep Pit 1,843 0.1% 0.332 0.002 0.24 0 0.01 0 0.01

Total Dairy Cows 1,780,000 100% 10.18 0.64 10.83

Heifers

Dry Lot 728,455 87.4% 0.015 0.02 0.15 0.02 0.04 0.51 0.55Daily Spread 90,032 10.8% 0.005 0 0.10 0 0 0 0Liquid/Slurry 7,712 0.9% 0.332 0.005 0.26 0.008 0.01 0 0.01Pasture 7,285 0.9% 0.015 0 0 0 0 0 0Total Heifers 833,484 100% 0.05 0.51 0.56

TOTAL 2,613,484 10.2 1.2 11.4

* N 2O volatilization factor used is 0.01 g-N 20/g-excreted N for all systems

** N 2O runoff/leaching factor used is 0.0075 g-N 20/g-excreted N for all systems

Dairy Cows and Manure Management Systems GHG Emissions Factors GHG Emissions

16

lagoonsfromzeroto$20/MgCO2eqforupto13TgCO2eqmitigation(acrosstheUS)andeventuallyreachingabout$200/MgCO2eqat22TgCO2eqmitigation(Gloy,2011).ICFInternationalevaluatedGHGmitigationcostsbyUSregion(as“break‐even”carbonprices)forUSagriculturalandlivestockactivities(ICF,2013).Foranaerobicdigestionoptionsatdairies,mitigationcostsvariedfrom$2‐$239perMgCO2eqdependingonfarmsize,digestertype,andbiogasuse(USPacificregion),withthecoveredlagoon‐and‐flarescenarioonthefarlowendofthisrange.Increasedsolidsseparationpriortothelagoonwasalsoevaluatedandreportedmitigationcostswereabout$5perMgCO2eqregardlessofdairysize,location,orwhethercompostingofsolidswereperformed.WhilevaluesintheICFreportattemptedtoaddressregionalandanimaltypespecificity,conditionsandcostsspecifictoCaliforniawerenotexplicitlyevaluated.CaliforniaEnvironmentalAssociatesrecentlypreparedareportforSustainableConservationdescribingGHGmitigationstrategiesspecificallyforCaliforniadairiesthatincludedanaerobicdigestion,conversionofflushtoscrapesystems,andimprovedsolidsseparationpriortolagoonsasoptions.Withanaerobicdigestion,amitigationpotentialof6.6MgCO2eq/yrwasproposedbasedoninstallationofdigestersatalllagoonsystemsinCalifornia(SustainableConservation,2015).Statewideabatementcostswerenotestimatedcitinglackofrepresentativedata,althoughtwodigestercasestudieswerereferencedwhichreportedapproximatecostspossiblyrangingfrom$10‐60/MgCO2eq.Similarlywiththeincreasedsolidsseparationandflush‐to‐scrapeconversionstrategies,costswerenotevaluatedduetoawiderangeofreporteddesign,cost,andperformancevariables,althoughamaximummitigationpotentialof40‐88%ofGHGsfromlagoons,respectively,weredescribedaspossible.ManningandHadrich(2015)estimatessocialcostbenefits(valuedascarboncredits),butnotmitigationcosts,fromconvertingCaliforniadairylagoonstomanuremanagementwithanaerobicdigestion.UsingaCO2eqvalueof$36/Mg,theycalculatedthatsocialvaluewouldvarybetween$142‐$206percowperyearbenefitthatwouldaccruetothedairyifGHGreductionwasmonetized(ManningandHadrich,2015).Althoughnotaddressedinthescopeofthisreport,emissionsfromentericfermentationmightbereducedthroughimprovedfeedandproductionefficiency,feednutritionadjustmentsanddietarysupplements(Gerberetal.2013).Moraesetal.(2014)modeledentericmethanemitigationthroughdietarychangesforCaliforniadairiesandsawestimatedemissionreductionsthatrangedfrom1%to25%costing$239‐$956perMgCO2eq,howevertheseoptionsneedadditionaltestinginacommercialsettingbeforerecommendationforuse(Moraesetal.2014).

2.3. Report Methodology Inthisreport,alternativedairymanureGHGmitigationscenarioswereevaluatedwiththegoalofestimatingcostsandmitigationpotentialsforstatewideapplication.Thisapproachhassignificantlimitations,whicharediscussedinmoredetaillaterinthissectionandineachsubsequentsection.Thisworkismeanttoserveasastartingpointfor

17

discussionandfuturedevelopmentknowingthatthesescenariosarenecessarilymodelleduponimperfectdataandassumptions.Fourprimarymanuremanagementstrategies,eachwithvaryingassociatedsubcomponents,wereselectedformoredetailedinvestigation(Table2.3):Table2.3:DairymanuremanagementGHGmitigationscenariosevaluatedinthisreport

Therearemanyotherpossiblemitigationstrategiesnotevaluatedordiscussedqualitativelyduetolimitedinformationavailabilityorperceivedstatewideapplicabilitygivencurrentconditions,althoughsomemaybeofinterestforfutureevaluationorapplicationonanyindividualdairy.Apartiallistingoftheseotheroptionsincludes:

Increasedpasturemanagementordailyspreading Thermochemicalmanureconversion(i.e.combustion,gasification,pyrolysis,etc.) Advancedsolid/liquidseparationtechniques Nitirification/denitirificationoradvancedwastewatertreatmenttechnologies Co‐digestionorcommunitydigestionconfigurations Heatrecoveryorcoproductvaluationoptions Advancedproductgenerationfrommanureorbiogas Lagoonadditivestoinhibitmethaneproduction(i.e.acidification,enzymes,etc.)

ForeachofthemajorcategoriesselectedinTable2.3,informationwascollectedontherelevanttechnologyandusedtoquantifypossiblecostsandgreenhousegasmitigationpotentials.Additionally,impactson‐sitetodairies,environmentalairandwaterimpactsatthelocalorregionalscale,andpossiblesourcesofadditionalrevenueorbarrierstoadoptionarediscussedqualitativelyforeachscenario.Detailedinformationonindividualmanuremanagementpracticesforeachofthe1600+dairiesinthestateisnotreadilyavailableandthereforeacriticalsimplifyingassumptionwasmadetoassumethatforanysizedairy,thefractionofmanureineachmanuremanagementtypeisasreportedinthestatewideGHGestimate(Table2.2).Most

Category

Subcategory Uncovered Covered Engine Microturbine Fuel Cell RNG 12 8 6

Anaerobic Digestion

Upgrade Existing Lagoon to Tier‐I, Cover, and Flare n/a Covered Lagoon Digester Plug Flow/Tank Digester

Scraping to Solids Production

Open Solar Drying Closed Solar Drying Forced Drying (Natural Gas Fuel) Composting with Bulking Agent

Solid Liquid Separation

Mechanical Separator Aeration

Low Effectiveness High Effectiveness

With Effluent Pond With Energy RecoveryDuration

(mo./yr.)

18

importantly,thisassumesthatapproximately60%ofadultcowvolatilesolidsaremanagedinanaerobiclagoonsandalldairieshavealagoon.Thisisanimperfectassumption;however,Meyeretal.(2011)reportedthatfordairysurveyrespondentsinGlennandTularecounties,approximately96%ofdairieshadstorageortreatmentponds(Meyer,etal.2011).Withthisassumedmanuredistributionforanysizedairy,costsforimplementationcanbeestimatedgiventhesupportingassumptionsdescribedlaterineachsection.ToestimatecostsovertheknownrangeofdairysizesinCaliforniafrom1‐10,000+adulthead,sixmodeldairysizeswereselectedtoexploreeconomiesofscale;300,750,1500,3000,5000,and10,000adulthead,with80%assumedmilkingand20%dryatanytime.Oncecostswereestimatedforthemodelleddairies,aregressionequations(powercurve)forcostswereestimatedandreappliedtoastatewidedatabaseofdairiestoestimatethehypotheticalcostincurredforanygivendairysize.Itisimportanttonotethatprojectedcostsforagivendairysizedonotrepresentthecostsforanyactualdairy.Methodsforcostestimationaredescribedlaterforeachcategory,butgenerallyattempttoutilizerepresentativecostsavailableintheliterature,orwherelacking,estimatecostsfromavailablevendororengineeringdata.Resultsarereportedin2015$USandperMgCO2eqmitigated,where“Mg”representsonemetrictonne(1000kg).Financialcalculationsperformedareexclusiveoftaxesanddepreciationandalsoexcludesitespecificanalysesforprojectdevelopmentthatmightincludespecialtyengineering,insurance,orpermittingcosts,amongothers.An8%interestrateand10‐yearloantermisassumedforannualizationofcapitalcosts,whichwhenaddedtoannualoperatingcosts,resultinatotalannualizedcostestimate.20‐yearloantermsmayalsobedisplayedintheappendicesorsupportingmaterialforadditionalreference.Economiccalculationsrepresentabudgetcostassessmentandnotaproject‐scalelifecyclecostassessment.Astatewidedatabasecontainingadultcowpopulationsforover1200farmswithapproximately1.66millioncows(93.5%ofthetotalstatewideestimate),wascompiledfromreportsprovidedbytheCentralValleyandSantaAnaRegional,WaterQualityControlBoards(RWQCB‐5&8)andusedinconjunctionwiththeaforementionedmanuremanagementscenariocostcurvestoapproximatestatewideimplementationcostsforthegivendistributionofdairysizes(Figure2‐2).Aslargerdairieshavelowerimplementationcostsperhead,itwasassumedthatadoptionwouldoccurbydairiesstartingfromlargesttosmallest.Twosubsetsofdairieswereusedtocomparecosts;thoseinthedatabasewith>300head,usedtoeliminateexponentiallyballooningcostsonverysmalldairieswithlittlemitigationimpact;anddairieswith>2000head,usedtoassessimplementationonthelargest225dairiesrepresentingalmost45%ofthestatewidepopulation(Table2.4).

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Table2.4:StatewidedairysizedatabaseinformationGrouping NumberofAdultCows NumberofDairies %ofStatewide

PopulationStatewideTotal 1.78Million 1650 100%

Fullreportdatabase 1.66Million 1230 94%Dairieswith>300head 1.65Million 1100 92%Dairieswith>2000head 0.8Million 225 45%

Figure2‐2:Dairysizesandnumbersincludedinstatewidefullreportdatabaseused

InordertocalculateGHGreductionsforeachmanuremanagementscenario,methodsconsistentwiththeprojectbasedCARBComplianceOffsetProtocolforLivestockProjectsCapturingandDestroyingMethanefromManureManagementPracticeswerefollowed(CARB,2014)wherebyemissionswiththenewmanuremanagementpracticesinplaceweresubtractedfromoriginalassumedbaselineemissions.Detailsonassumptionsusedforeachscenarioevaluatedaredescribedfurtherineachsubsequentsection.Sincetherewerenoassumeddifferencesinmanuremanagementpracticesondifferentdairysizes,therelativemitigationofGHGsperheadwascalculatedtobethesameindependentofdairysize.

2.4. Limitations of this Study ThisworkproposescostsandGHGmitigationpotentialsforvariousdairymanuremanagementalternativestargetinganaerobiclagoonemissions.Lackofaccurateinformationdescribingindividualmanuremanagementpracticesondairies,aswellaslimitedorhighlyvariablecostsandmitigationpotentialsreportedforalternativemanagementscenariosmakethisanextremelydifficulttask.Themethodsappliedinthisreportarenecessarilylimitedinthefollowingways:

0

2,000

4,000

6,000

8,000

10,000

12,000

0

200,000

400,000

600,000

800,000

1,000,000

1,200,000

1,400,000

1,600,000

1,800,000

0 200 400 600 800 1,000 1,200 1,400

Dairy Size (ad

ult cows)

Number of ad

ult cows (cumulative)

Number of Dairies (Largest to Smallest)

Number of adult cows(cumulative)

Dairy size (adultcows)

20

Scenariosarenotexhaustive:Thisstudyhasfocusedonseveralmajoralternativescenarios.Theremaybeothersthatwarrantsimilarinvestigation.Inventoryinformationisuncertain:Whilemanyreferencesexist,thetransparencyofhowtherelativefractionofanimalsineachmanagementsystemwasestimatedandmanurecollectionefficiencyarenoteasilydetermined,mostsignificantlyforthelagoonandliquidslurrycomponents.GHGemissioncalculationmethodsareuncertain:BaselineandexistingGHGemissionsestimatesareacknowledgedsimplificationsofcomplex,dynamicprocesses.Methodsmayexistorcanbedevelopedovertimetomoreaccuratelyassessemissionsgivenmoredetailedunderlyinginventoryandbiogeochemicalinformation.Initialcostestimatesareused:Formanyofthesescenarios,limitedornooperationalinformationexistforsimilarinstallationsinCalifornia,resultinginahighdegreeofcostuncertainty.Whereoperationalexamplesdidnotexist,costshavebeenestimatedusingpreliminaryengineeringestimationpracticesconsistentwithmethodscommonlyusedforafeasibilitystudyorpreliminarybudgetestimate.Additionaldesign,implementation,andcommercialvalidationdataarerequiredforimprovedaccuracyandconfidence.SpeculativeGHGemissionsfactorsareusedinsomecases:Inmanyofthescenariosinvestigatedinthisreport(drying,aeration),emissionrateshavenotbeenwellstudiedorreportedspecifictotheseapplicationsandarehighlyuncertain.Tofacilitateinitialestimation,speculativevalueshavebeenassumedfrominformedreviewofavailableinformation.Attemptstouseconservativevalueshavebeenmade,howeveradditionalresearchandvalidationisrequiredtoimproveaccuracyinpractice.Assumesapplicationofeachtechnologyonallfarmsizesispossible:Forstatewidemitigationpotentialsandcostestimates,theassumptionismadethatallscenarioscanbeappliedonallsizesofdairyfarmspertheprojectedcosts.Individualsiteconstraintsmaymakethisassumptioninvalidorhighlyinaccurate.Withthesecaveats,itiscriticaltonotethattheseresultsdonotapplytoanyindividualdairyoruniformlytoalldairiesofalistedsize.Inallcases,additionalresearchiswarrantedandadditionallimitationsspecifictoeachsectionareelaboratedonintheaccompanyingreport.

21

3. Anaerobic Digestion Addinganaerobicdigesters(AD)todisplaceopenanaerobiclagoonsortreatalargeportionofmanurebeforethematerialreacheslagoonstorageareattractiveoptionsforGHGmitigation.ThetechnologyiswidelyrecognizedasaneffectivemethodforGHGreductionandisconsideredmatureworldwide(ifnoteconomicinCalifornia)(USEPA,2011,ICF,2013,LeeandSumner2014,Owen,etal.2014,SustainableConservation,2015),ADsystemscouldbeintegratedintomanyCaliforniadairyoperationswithlow‐to‐moderateimpactorchangestodairyoperations,atleastcomparedtosomeoftheotherscenariosevaluatedinthisreport.RecentstudiesthatevaluatedADasaGHGreductiontoolhaveusedcostestimatesbasedonUSaveragesorolderCalifornia‐basedcosts.ThosestudiesgenerallyrecognizethatcurrentCaliforniainstallationcostsarelikelyhigherandmitigationcostsmaybeunderestimatedornotevaluated(ICF2013,LeeandSumner2014,SustainableConservation,2015).ThisworkattemptstoaddressthisbyusingupdatedCaliforniadairydigestercostestimates.

3.1. Overview of scenarios evaluated ThissetofscenariosincludesupgradingtoaTier1double‐linedlagoonandcoveringandflaringtherecoveredbiogas(i.e.,T1CoverandFlare)andscenarioswithfourdigestervariations.Thedigesterscenarioshaveenergyrecoveryandarecomprisedoftwodigesterclasses;(1)coveredTier1lagoonand(2)abovegroundtankcompletemixorplugflowdigestersystems(tank/PF).Eachdigestersystemincludesaneffluentpondorcontainmentvolumetoholddigestateuntilitisusedasirrigationorspreadonfields.Becausetheeffluentpondsareessentiallyanaerobiclagoonsoranaerobicslurrypits,theyareeitherasourceofGHGemissionsifopentotheatmosphere,orasourceofadditionalbiogasifcoveredandgascollected.Therefore,thedigesterscenariosincludecoveredanduncoveredeffluentpondcases.Finally,eachdigestercaseisanalyzedwithfourdifferentenergyrecoverydevices(reciprocatingengine,microturbine,fuelcell,andupgradetocompressedbiomethanevehiclefuel[referredtoasrenewablenaturalgasorRNG),resultinginsixteendigester‐to‐energyscenariosandtheonecoverandflarescenario(Table3.1).Table3.1:DigestertoEnergyandUpgradetoTier1withCover&Flarescenariomatrix

Energy Recovery Device

Lagoon digester Tank / Plug Flow Cover & Flare - Tier 1

Lagoon Uncovered

effluent pond Covered

effluent pond Uncovered

effluent pond Covered

effluent pond

Recip Engine

no Microturbine Fuel Cell CNG

22

3.2. Digester‐Energy and Tier 1 Upgrade with Cover‐and‐Flare: Methods and Assumptions

3.2.1. Emissions Reduction Modeling EmissionsreductionestimatesforthedigesterandT1cover&flarescenariosweredevelopedbasedonmethodsandassumptionsintheCARBLivestockProtocol(CARB,2014).Themethodincludesestimatinganaerobiclagoonbaselineandprojectemissionsforamodeldairywiththedifference(baselineminusproject)beingemissionreductions.EachdigesterenergyorT1cover&flarescenariomentionedaboveisa“project”withitsdiscreteGHGemission.BaseLineEmissionsThe“model”dairyutilizesflush‐to‐anaerobiclagoonmanuremanagement.It’sassumedthattheamountofmanurethatreachesthelagoonfromallanimalsonthedairyisequivalentto60%ofadultcowmanureproduction.7Basedonthe60%manure‐to‐lagoonassumptionandusingcalculationmethodsintheCARBlivestockprotocol,thebaselineGHGemissionforanaerobiclagoonis5.24(MgCO2eq/y)8peradultanimal.Appendix3.7showsallassumptionsusedtocalculatethebasecaseGHGemission.ProjectEmissionsProjectemissionsconsistoffugitivemethaneemissionsfromthelagooncoverordigester,methaneslipintheenergyconversionapplianceandmethaneemissionsfromuncoveredeffluentponds.FossilordirectCO2emissionsfortheprojectareassumedthesameasthoseinthebasecaseandarenotcalculated.Forbiogasproductionestimates,simpledigestermodelswereusedwhichwerealsobasedonfactorsandassumptionsfoundintheLivestockprotocol.Thisincludesultimatemethanepotentialperkgvolatilesolid(Bo),methaneconversionfactors(MCFordegradationfraction)forlagoonsanddigesters,andmethaneslipanddestructionfactorsforenginesandflares.Sixtyper‐centofmilkcowmanureissenttothedigesterscenarios.Thisisthesamemanurefractionreachingalagooninthebasecasesothatemissionsreductionsduetochangeinmanuremanagementmethodcanbecompared.9Modelresultsindicatethatmethaneproductionrangesfrom305m3cow‐1yr‐1fortheTier1coveredlagoonw/flare

7Areviewofseveraldairywastemanagementplansandmanureflowsinproposalsfordigestergrantfundswasconductedanditwasfoundthattheamountofmanurevolatilesolids(VS)reachingthelagoonfromallanimals(adultcows,heifers,calves),wheresomemanureisflushed,otherisdepositedincorralsorpasture,wasequivalentto~60%ofVS(manure)productionfromthemilkcows.The60%assumptionisalsoessentiallythesamefractionofadultcowmanureassumedtoreachlagoonsinthestatewidedairymanuremanagementGHGinventory.8Mgmeansmetrictonne(Mg=1000kg=1metrictonne)(seealsofootnote6)9Adigesterprojectatanactualdairymayincludemeanstoincreasetheamountofmanuresenttotreatmentinordertoincreasegasproduction.

23

scenarioto381.3m3cow‐1yr‐1fortheTank/PlugFlowdigesterwithcoveredeffluentpond.GHGmitigationrangesfrom4.44to5.08MgCO2eqcow‐1yr‐1(Table3.2).Appendix3.8containsafulllistingofmodelinputassumptionsandper‐cowoutputs.Table3.2:Keyparametersandresultsfrommethaneproduction/emissionsmodel

Parameter or Result Units

Tier 1 Covered

Lagoon & Flare

Lagoon Digester

Above Ground Tank/ Plug

Flow Digester

VS collected (60% of manure) (kg/cow/yr) 1699 1699 1699

MCF (lagoon or digester) - 0.748 0.8 0.9

Methane produced in BCS - uncovered effluent pond

(m^3/cow/year) 305.0 326.2 367.0

(ft^3/day/cow) 29.5 31.6 35.5

VS to effluent pond (kg/cow/yr) - 340 170

MCF (eff. pond) - - 0.35 0.35 Effluent pond methane emission (or production)

(m^3/cow/year) - 28.5 14.3

Methane produced in BCS - w/ Covered effluent pond

(m^3/cow/year) - 354.8 381.3

(ft^3/day/cow) - 34.3 36.9

Project Emissions - uncovered eff. pond (Mg CO2eq /cow/y) 0.29 0.80 0.40

Project Emissions - w/ Covered eff. pond (Mg CO2eq /cow/y) - 0.33 0.16 Mitigation – digester w/ uncovered eff. pond

(Mg CO2eq /cow/y) 4.95 4.44 4.84

Mitigation - w/ Covered eff. pond (Mg CO2eq /cow/y) - 4.91 5.08

3.2.2. Energy Conversion Performance and NOx Emission Assumptions Conversionefficienciesforreciprocatingengines,microturbinesandfuelcellsareassumedtobe30%,23%and50%,respectively(higherheatingvaluebasis).ProductyieldfortheRNGscenarioassumes70%ofthemethaneinbiogasisrecoveredascompressedbiomethane,basedonBioCNGsingle‐passmembraneseparationtechnology.Energyproductionoryieldonpercowbasisisshownbelowforeachofthedigestertypes(Table3.3).Thetailgasmethanefromtheupgradingprocessisflaredinthisscenario.Table3.4listsNOxemissionfactorsusedforeachenergyappliance.

24

Table3.3:Conversionefficiencyandpercowenergyproductionbyscenario

Parameter or Result Units Lagoon Digester

Above Ground Tank/ Plug Flow Digester

Uncoverd Eff. Pond

Coverd Eff. Pond

Uncoverd Eff. Pond

Coverd Eff. Pond

Methane produced in BCS m3/cow/yr 326.2 354.7 367 381.3 Energy in gas - per cow basis (before conversion)

kW (Btu/h)

0.385 (1314)

0.419 (1430)

0.434 (1481)

0.45 (1535)

Reciprocating Engine (@ 30% conversion eff.)

kW/cow 0.116 0.126 0.13 0.135

MicroTurb. (@ 23% conversion eff) kW/cow 0.089 0.096 0.1 0.104

Fuel Cell (@ 50% conversion eff) kW/cow 0.193 0.21 0.217 0.225 CNG Fuel Recovery (70% methane capture)

gde/cow/day 0.155 0.168 0.174 0.181

Table3.4:NOxemissionfactors

Technology NOx Emission

Factor (lb/MWh) Notes

Reciprocating Engine

0.46 11 ppmvd @15% O2, 30% HHV efficiency

Micro Turbine 0.24

Source test: Microturbines MT250 Ingersall Rand, Ralph's Groceries (there are no CARB Certified DG microturbines meeting 0.07 & 0.02 lb/MWh emissions factor for NOx and VOC respectively http://www.arb.ca.gov/energy/dg/eo/eo-current.htm)

Fuel Cell 0.02 (lb/MMBtu) Permit: FuelCell Energy, DFC300MA [3 x 300] (Eastern Muni, Perris)

Flare 0.025 Low-NOx flare information from Ramon Norman, SJVAPCD. Flare is used in 'Cover and Flare Scenario' and the CNG model for disposing of tail gas

3.2.3. System Cost Assumptions Tier1Upgrade‐with‐Cover‐and‐FlareCostsThecoverandflarescenarioincludescostsofupgradingtoaTier1lagoon,as,.basedonconversationswiththeCentralValleyWaterQualityControlBoard,itisuncertainwhatTier2lagoondesignswillbeadequateforwaterprotectionfromseepageandmayrequireupgradetoTier1design.CDFA,intheirdigestergrantsolicitation,requiredlagoondigesterproposalsincludeTier1lagoonconstruction.Wethereforeassumethatifstatefundsareusedtohelpoffsetcostsofmethanemitigationfromdairymanuremanagement,suchascoveranaerobiclagoonsandflarethegas,thenTier1lagoonupgradewouldlikelybearequirement.Tier1lagoonconstructioncostisbasedoninformationinaProvost&PrichardMemototheWaterQualityControlBoard(SchaapandBommelje,2013).FlareandequipmentcostsweretakenfromtheICFInternationalreport(ICF,2013)andcurrentinstalledcoversystemcostsarebasedonEnvironmentalFabrics,Inc.quotes.

25

AdetailedtableandotherassumptionsandnotesforTier1upgradewithcoverandflarecostareinAppendix3.1.ThemitigationcostcurveforTier1CoverandFlareisshowninFigure3‐1.TheTier1lagoonconstruction(upgrade)representsabout46%ofthecapitalcostinthisscenario.

Figure3‐1:Mitigationcostcurvevs.no.ofmilkcowsonadairy,CoverandFlarescenarioDigester‐EnergyScenarioCostsCapitalandoperatingcostsfornewdairydigesterinstallations(whichincluderecip.engine‐generatorsanduncoveredeffluentponds)weremodeledbasedonrecentconsultantreportsonCaliforniadairydigesterinstallationsandCDFAdigestergrantproposals(CDFA,2015;BlackandVeatch,2013;ICF,2013;SummersandWilliams,2013).Costsofabovegroundtankorplugflowdigesterswereconsistently~20‐25%higherthancoveredlagoonsystemsinthereviewedliterature(onapercowbasis).Forcapitalcostmodeling,apowercurvewasfitfirstusingallcapitalcostdatafromtheliterature(alldigestertypes)fromwhichtwoadditionalcurveswereconstructedtorepresent(1)covered(Tier1)lagoondigestersand(2)engineeredabovegroundtankorplug‐flowtechnology.Thetank/plugflow(PF)systemscurvewassetat5%higherthanthe"alldata"oraveragecurve.Thelagoondigestersystemcurvewascreatedtobeabout30%lessthanTank/PlugFlowatsmallscaleandabout20%lessthanTank/PlugFlowatthelargerscale(onaper‐milk‐cowbasis).Thesecapitalcostcurvesincludegasengine‐generatorpowertechnology(andappropriategascleaningandemissionstreatment)anduncoveredeffluentpondsareshowninFigure3‐2alongwithcapitalcostfortheUpgradetoTier1LagoonCoverandFlarescenario.

0

10

20

30

40

50

60

0 1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000 9,000 10,000

($/ Mg CO2eq

)

No. Adult Cows

Mitigation Cost ‐ Tier 1 Upgrade with Cover and Flare

10 yr. debt

20yr. debt Term

26

Figure3‐2:Digesterandcover‐and‐flareinstalledcostcurvesNote:Orange/yellowdatarepresentcoveredTier1lagoondigesters.DarkBlue/Browndataareabovegroundtankorplug‐flowsystems.DataarefromBlack&Veatch,2013;SummersandWilliams,2013;ICF,2013;CDFA,2015.

It'salsoassumedthatalldigestersystemsemptythedigestateintoaneffluentpondorbasin.Thesearetreatedasanaerobicstoragecontainmentwithfurtherfermentationofvolatilesolids.Iftheeffluentcontainment(pond)isuncovered(whichisthecaseformostdairydigesterinstallations),itisasourceofmethaneemissionsandismodeledassuchintheGHGcalculations.Iftheeffluentpondiscovered,themethanefromthisportionofthesystemcanalsoberecoveredandaddedtotheflowforuseinenergyrecoveryandfugitiveemissionsarereduced.Thedigesterscenariosincludecoveredeffluentpondcases.Incrementalcostsforthesecasesarebasedonlagooncoveringsystemsonly(i.e.,noincrementaleffluentlagoonconstructionasthatfacilitycostisalreadyincludedinthe'uncovered'effluentpondcases).CoveredEffluentPondCostAdderAdditionalcapitalcostforthe‘coveredeffluentpond’digestercasesisbasedonthecovercostsderivedfortheTier1CoverandFlarescenario.Weassumetheeffluentpondistwo‐thirds(2/3)thesize(surfacearea)ofthestand‐alonelagoonmodeledintheCoverandFlarescenario.Thereasonbeingthatdigestercapacity,plusaneffluentpond,isassumedsufficienttomeetfacilitymanureretentionandstormrun‐offrequirements.Appendix3.9showsthedetailedcostestimate(bydairysize)whichisusedasacapitalcostadderforthecoveredeffluentlagoonscenarios.

27

Energy Device Cost Adders MircoturbinesAsmentionedabove,thecapitalcostestimatesforthebasicdigesterscenariosincludereciprocatingengine‐generatorsystems.Microturbinesystems(withoutexhaustgasaftertreatment)areassumedtohavesameinstalledcostasreciprocatingengine,sothereisnocostaddertothebasedigester.FuelCellsTheFuelcellsystemcostadderis$3,500/kWabovereciprocatingenginesystems.Thisisbasedonacostdifferenceanalysisofinstalledbiogasfuelcellsandreciprocatingenginesfromliteratureandprojectcasestudies(Table3.5andAppendix3.10fordetailsontheanalysis).OperationsandMaintenance(O&M)Operationandmaintenancecostforenginesystemswithdairybiogasis$0.0377/kWhwhichisanaverageofvaluesreportedinSummersandWilliams(2013).ThesameO&Mcostispresumedformicroturbinesystems.FuelcellO&MscaleswithcapacityandisderivedfrominformationinanNRELreportindicating$500,000annualmaintenancefora1.4MWfuelcellsystemandincludesstackreplacementat5years(Table3.5andAppendix3.10)(RemickandWheeler2010).Table3.5:Powersystemcostadders

Digester Systems with: Cost Differential ($/kW) O&M ($/kWh)

Recip. Engine Base (with NOx control, i.e., SCR) 0.0377 *

Micro Turbine Approx. same cost as engine (no

exhaust after treatment) 0.0377 *

Fuel Cell 3,500/kW (above recip. engine

cost) ‡ = 0.2166x-0.216, where x=

capacity in kW. ‡ * Source: Summers, M. D. and D. Williams (2013). ‡ See Appendix 3.10

Biogasupgradedtofuel‐RNGscenarioCostforupgradingtocompressedbiomethanewithvehiclefuelingequipment(fuelingstation)isbasedonBioCNGprojectsheets,conferencepresentationsandaGeosyntecreporttoFlagstaffLandfill(Geosyntec,2013,Robillard,2014,BioCNG,2015).Appendix3.11hasdetailedassumptionsforRNGmodelcostdevelopment.BioCNGemploysasingle‐passmembraneseparationtechnologyforCO2/CH4separation.Theyreportabout70%ofincomingmethaneisupgradedtofuelwiththeremaining30%remainingwiththeCO2inthetailgas(70%productyield).Thistailgasmustbedisposedof,notvented,andcanpossiblybeburnedinanengine.Thetailgas(methanebypass)isflaredinthisscenario.Flarecapitalandoperatingcostsareaddedusingdatafrom"Tier1coverandflare"flareequipmentcosts‐scaledtotailgasflowfortheRNGscenarios.NOxemissionsare0.025lb/Mbtuasincoverandflare

28

scenario.ReciprocatingenginecostissubtractedfromdigestercapitalcostandthentheRNGsystemisaddedinthescenariocostcalculation.

3.3. Greenhouse Gas Mitigation, cumulative costs, energy and NOx emissions Mitigationcosts(i.e.,$/MgCO2eqmitigated)weredevelopedforallseventeenscenariosusingestimatedcapitalandoperatingcostsforarangeofdairysizes(300–10,000cows)10,estimatedGHGreductionpercowforeachscenario,andcapitalcostamortizationover10years,eachat8%annualinterest.Curveswerefittotheresultsforestimatingmitigationcostsforotherdairysizes.Additionaldetailsonassumptionsandmethodsareprovidedintheappendices.Forthedigester‐to‐electricityscenarios,mitigationcostsforsmalldairies(300cows)rangedfrom80toabout135$/MgCO2eq.Atthelargestdairysize(10,000cows),mitigationcostwas$20‐$40perMgCO2eq(Figure3‐3).Mitigationcostfor“Tier1CoverandFlare”wassomewhatloweratsmallerdairysizesandconvergedwiththelowestcostelectricitycast[“LagoonDigester‐UncoveredEff.Pond‐Recip.Enginecase](Figure3‐3).

Figure3‐3:Highestandlowestmitigationcostcurves;digester‐electricityandcoverandflareForthedigester‐to‐RNGscenarios,mitigationcostishigherthantheelectricityscenariosatthesmalldairies($140‐$170perMgCO2eq)andthendeceasesfairlyrapidlyasdairysizeincreasestoabout$20/MgCO2eqatthelargestdairysize(Figure3‐4).AcompletesetofmitigationcostcurvedevelopmenttablesandindividualplotsfortheTier1CoverandFlarescenarioandalldigester‐to‐energycasesareinAppendices3.1through3.6.

10Dairysizes(milkcows):300,750,1500.3000,5000,10,000.

0

20

40

60

80

100

120

140

0 2,000 4,000 6,000 8,000 10,000

($/ Mg CO2eq

)

Number of Adult Cows

Highest & Lowest Mitigation Cost‐Curves: Electricity & "Tier 1 Cover & Flare"

Tank/Plug Flow w/ Covered Pond‐Fuel Cell

Lagoon Digester ‐ Recip. Engine

Tier 1 upgrade w/ Cover and Flare

29

Figure3‐4:CNGscenarios:HighestandlowestmitigationcostcurvesCostsandmitigationpotentialacrossdairyindustryUsinganinventoryofCaliforniadairies11withmilk‐cowpopulationforeachdairy,themitigationcostcurveswereusedtocalculateannualmitigationpotential(and10‐yearcosts)foreachdairy(with≥300cows).Resultsforindividualdairieswerethenusedtocreateamitigationcostsupplycurve(Figure3‐5)orotherwisesummedtoestimateindustry‐widemitigationandtreatmentcosts.Figure3‐5showsmitigationcostsupplycurves(cumulativestartingwiththelargestdairies)fortheTier1CoverandFlarescenarioandthehighestandlowestcostofeachdigester‐energyappliancegroupexceptmicroturbines(becausetheircostcurvesareapproximatelythesameasthereciprocatingenginecases).Totalannualmitigationpotentialrangesfromabout7.3Tg/yearto8.3Tg/yearforthedigesterscenarios.

11CAdairyinventorycompiledfromreportsprovidedbytheCentralValleyRegionalandtheSantaAnaRegionalWaterQualityControlBoards(RWQCB‐5&RWQCB‐8).Theinventorylistsmorethan1200dairiesincludingmilkcowpopulationateachdairy.1.66millionadultcows(orabout94%ofCAadultdairycows)areaccountedforintheinventory.

0

20

40

60

80

100

120

140

160

180

0 2,000 4,000 6,000 8,000 10,000

($/ Mg CO2eq

)


Mitigation Cost‐Curves: RNG(highest & lowest)

Tank/Plug Flow w/ Covered Pond

Lagoon Digester

30

Figure3‐5:AnaerobicDigestionMitigationcostsupplycurve,largesttosmallestdairies($/MgCO2eqvs.CumulativeMitigation)Acomprehensivetableshowingmitigationpotential,10‐yearcost,totalenergycapacity(MWorgallons‐diesel‐equivalent/year(gde/y)),andannualNOxemissionsforall17digester‐energy+T1coverandflarescenariosforthefullindustryaswellasthelargest225dairiesappearsbelow(Table3.6PartAandPartBforfullindustryandlargest225dairies,respectively).Largest225dairies:treatmentcostandmitigationIt’snotlikelythatalldairieswithflushlagoonmanuremanagementwouldinstalladigester‐energysystemandit’snotcertainthatalldairieshavelagoonmanurestoragethoughMeyeretal.(2011)catalogedlagoonson96%ofdairiesinatwo‐countysurveyintheCentralValleyIt’smorecostefficient($/Mgbasis)totreatthelargerdairiesfirstbecauseofanexpectedeconomyofscaleofdigester‐energysystems.Ten‐yearcoststotreatdairieswith2000ormorecows(thelargest225dairiesinourinventory)rangefromabout$1.1to$2.2billionandcouldmitigatebetween3.6‐4.1TgCO2eq/y(Figure3‐6andTable3.6).Averagemitigationcostswouldrangefrom$29‐$55/MgCO2eqforthesescenariosasmodeled.

0

20

40

60

80

100

120

140

160

180

0 1 2 3 4 5 6 7 8 9

Mitigation Cost ($/M

g CO2eq

)

Mitigation (Tg CO2eq/y)

Mitigation Cost vs. Cumulative Mitigation‐ Digester Scenarios

Covrd Lagoon‐ UNcovrd eff.Pond‐ Recip. Eng.

Tank/Plug flow‐covrd effPond‐Recip Eng

Covrd Lagoon‐ UNcovrd eff.Pond‐Fuel Cell

Tank / PF w/ COVERED EFF.Pond‐ Fuel Cell

Covrd Lagoon‐ UNcovrd eff.Pond‐CNG

Tank/Plug flow‐covrd effPond‐CNG

Covered Tier 1 Lagoon withFlare

31

Figure3‐6:Annualmitigationvs.10‐yr.mitigationcost‐2000‐cowandlargerdairies

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

0.0 0.5 1.0 1.5 2.0 2.5

Mitigation (Tg CO2eq/y)

10‐Year Mitigation Cost (Billion $)

Annual Mitigation vs. 10‐Year Cost: 2000‐cow and larger Dairies

Covrd Lagoon‐ UNcovrd eff.Pond‐ Recip. Eng.

Tank/Plug flow‐covrd effPond‐Recip Eng

Covrd Lagoon‐ UNcovrd eff.Pond‐Fuel Cell

Tank / PF w/ COVERED EFF.Pond‐ Fuel Cell

Covrd Lagoon‐ UNcovrd eff.Pond‐CNG

Tank/Plug flow‐covrd effPond‐CNG

Covered Tier 1 Lagoon withFlare

32

Table3.6:ComprehensiveDigester‐Energyresults

Part A) ≥ 300 milk cows/dairy or 1110 dairies (1.65 million cows)

Mitigation Potential (Tg/y)

10-year cost

(Billion $) MW Tons Nox


10-year cost



10-year cost



10-year cost



10-year cost

(Billion $)

Tons Nox

Recip. Eng. 3.00 190 382 3.59 206 416 3.93 213 430 4.59 222 447Microturb. 3.35 145 153 3.96 158 166 4.34 164 172 5.02 170 179Fuel Cell 4.27 316 28 4.93 344 30 5.36 356 31 6.02 370 32

Potential (million gde/y)

Tailgas f lare (tons Nox)







92.7 71 101 77 104 80 108 83

Part B) Largest 225 dairies [those w/ ≥ 2000 milk cows/dairy] (~800,000 cows)


10-year cost



10-year cost



10-year cost



10-year cost



10-year cost

(Billion $)

Tons Nox

Recip. Eng. 1.10 92 186 1.32 100 202 1.42 104 209 1.68 108 217Microturb. 1.27 71 74 1.51 77 81 1.62 80 84 1.88 83 87Fuel Cell 1.61 154 13 1.86 167 15 1.99 173 15 2.24 180 16









45.1 34 49 38 51 39 53 40

Tier 1 Upgrade- Cover and Flare

3.95 1.13 107

Tier 1 Upgrade- Cover and Flare

8.13 2.84 221

Energy Device

Lagoon Digester Tank / Plug Flow Digester

Uncovered effluent pond Covered effluent pond Uncovered effluent pond Covered effluent pond

3.55 3.92 3.86 4.05

RNG 1.16 1.35

Covered effluent pond

Tank / Plug Flow Digester

4.814.45

1.44 1.68

Energy Device

Covered effluent pond

Lagoon Digester

Uncovered effluent pondUncovered effluent pond

5.46

7.29 7.948.05 8.33

3.91RNG

33

3.4. Limitations WhilethesepredictedcostsarebasedonupdatedCaliforniadigesterinstalledcostsestimates,theresultshavesignificantuncertainty,likelyontheorder±30%(thoughnotanalyzed).TimeavailableforthisanalysisundercontractwithARBwasnotsufficienttoconductasensitivityanalysisofthecostandfinancialassumptions.Keyassumptionsincludeenergyrevenueprices($0.127/kWhand$3.00/gde),costofmoneyat8%/yearandprojectpay‐offperiod(orloanterms)of10years.Nograntbuydownorotherproductrevenuestreamswereconsidered.Itisimportanttonotethatwhenconsideringenergyasthesolesourceofrevenues,digestersinCaliforniaarenoteconomicatmostcurrentlypublishedenergysalespricesinCalifornia,includingtheearlyestimatedBIOFITpriceof$0.127/kWh.Iftheywereprofitableundertheseconditions,themitigationcostswouldhavebeenlessthanzerofortheADscenarios.Finally,digesterprojectshaveexperiencedissueswithutilityconnectivity(delays,unexpectedorhighcosts),permittingdelays,higherthanexpectedoperatingcostsandotherissues(Camarilloetal.2012).

34

4. Converting from Flush to Scrape and Solid Manure Management ConversionfromflushtoscrapedmanuremanagementhasthepotentialtoreduceGHGemissionsbyfacilitatingdiversionofmanurefromanaerobicstoragelagoons;however,itisimportanttoacknowledgethatscrapingalonedoesnotachievethisgoal.Scraping,whichcaninterceptmanureathighersolidscontents(typically8‐14%)thanflushsystems(typically1‐2%solids),wouldlikelyonlyresultinamarginalreductioninGHGemissionsiffollowedbystorageinliquid/slurrysystems,which,evenwithcrustformation,stillfosterssignificantanaerobicactivityandassociatedemissions(Table2.2).Scraping,followedbydailyspreadingandincorporationofslurrymanurewouldpresumablyresultinlessCH4andNH3emissionscomparedtolagoonstorage.However,itrequiresspecializedtrucksandspreadersnecessarytotransportslurrymanureandtheabilitytoenteranddistributemanurewithinthenearbycroppingsystemonadailybasisformuchoftheyear.Manurecannotalwaysbeappliedtogrowingcrops,likecorn,inthisway,solandusewouldhavetobealteredfromcurrentpatternsdevisedtomaximizefeedproductionfromfarmedlands.Thisscenariowasnotevaluatedhereduetotheuncertainorspeculativeconsequencesforcurrentdairycroppingsystemsandlanduse.Scrapedmanureismorelikelytobestoredandthenappliedasdriermaterialatpointsintimeincroprotationsthatallowfieldaccessandincorporation.Therefore,systemswhichscrapemanureandconvertittoasolidformareinvestigatedinfurtherdetailhereandincludescenariosfor1)SolarDryingonOpenPads,2)SolarDryingusingClosedDryingHouses,3)ForcedEvaporationusingNaturalGasFueledDryers,and4)Composting.Solid/liquidseparationisalsodiscussedinasubsequentsectionsinceitdoesnotrequirescrapingtobeeffective.

4.1. Converting from flush to scrape ThemajorityofCaliforniadairiesusesomeformofflushmanuremanagementintheiroperations.A2011surveyof394representativeCaliforniaherdsfoundthatupwardsof62%ofthefarmsusedflushingaloneorincombinationwithscrapingtocollectmanurefromlactatingcowhousingareas(Meyeretal,2011).Theflushwatertypicallyconsistsofrecycledwaterfromatreatmentorstoragepondorrinsewaterfromthemilkingparlor.Theliquidmanuremaythenbeseparatedbyavarietyofmeansbutthemajorityofvolatilesolids(VS)generallyeventuallymakeittoastoragelagoon.BasedonresponsestotheARB’sSLCPconceptpaper12,theindustryhasadoptedflushsystemsduetovariousbenefitsofliquidhandlingoversolidhandlingincludingincreasedworkerandcowsafety,moreconvenientandefficientmanurehandling,easeofdistributiontocrops,andfavorableeconomics.Accordingtoanotherrecentreport,someoftheseclaimsarequestionable,butlittledataisavailabletosupportcompetingclaims(SustainableConservation,2015).Scrapesystemsaremorecommoninotherpartsofthecountry,especiallyincolderclimatesthatcannotflushduetofreezingtemperaturesinwinter.Ingeneral,threetypesofscrapingsystemsexist:VacuumTruckScrapers,AutomatedMechanicalScrapers,andTractororFrontLoaderRubberMountedScrapers.Each12http://www.arb.ca.gov/lists/com‐attach/52‐slcpstrategy‐ws‐B2NRNlw0VncBfgBj.pdf

35

systemhaspossibleadvantagesanddifficultiesaswellasdifferingeconomicimpacts.Thefollowingsectionsgiveanideaofthecostsandrequirementsforswitchingtosuchsystemsbasedonasamplingofvendorquotesandinterviewswithdairiesthathaveimplementedaswitch.Again,models,charts,anddiscussionincludedarerepresentationofaveragecostsforthemodeldairy;anyspecificdairymayexperiencesignificantlyhigherorlowercosts.

4.1.1. Key Assumptions and Options Amodelwasdevelopedtoestimatetheannualcostsfortransitioningfromflushtothreetypesofscrapingsystemsfordairiesranginginsizefrom300–10,000head(milkinganddry).Akeyassumptionisthatthedairyusesfreestalllanesforadultcowhousing500ftinlengthandhaslimitedinfrastructurecurrentlyinplaceforanykindofscrapingsystem.FortheVacuumTruckscenario,capitalcostswereestimatedfromavendorquoteforthreedifferentsizedtrucks.FortheAutomatedMechanicalScraperscenario,quotesfromavendorandalsoestimatedcostsfromascrape‐transitioneddairywith1,500headwereusedtoestimatecapitalandoperatingcostsforsystemsutilizingchainsorcables.TheFrontMountedRubberScraperscenariotookintoaccountvendorquotesandalsotheinfrastructureandconcrete/constructioncostsfromtheAutomatedScraperscenario.Forallcases,aloaninterestrateof8%wasassumedwitha10‐yearloanperiod.Whenapplicable,anexponentialscalingfactorof0.675wasusedinabsenceofempiricaldatatoestimatecostsforlargerdairies.13AmoredetailedoverviewofassumptionsandmethodologiesusedforeachscenariocanbefoundinAppendix4.1.

4.1.2. Costs Theestimatedtotalannualizedcosts(capitalandoperationandmaintenance)forthreescrapingoptionsarepresentedinTable4.1andFigure4‐1.Economicdifferencesbetweentheoptionsexistandfarmsofdifferentsizesmaybeimpacteddifferentlyand/orfindthatcertainsystemsarebettersuitedforsomefarmsthanothers.Figure4‐2showstheaveragecostsofscrapingfor10‐and20‐yearloanperiods.AveragevaluesareusedinFigure4‐2,maskingthewiderangethatexistsbetweentheoptionsasinFigure4‐1.

13Economiesofscalecanusuallybeestimatedbyanexponentialmethodincorporatinganexponentintherangeof0.5–0.85(Dysert,2005).Intheabsenceofdata,theaverage(0.675)waschosenwhenmodeling.AdditionalinformationcanbefoundintheAppendix.

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Table4.1:Summarizedcostsforthreescrapesystemsasmodeled

Scrape System Total Installed

Cost ($)

Total Operational Cost ($/yr)

Total Annualized Cost

($/yr/head)*

Main Influence on Annual Cost

Vacuum Truck 190,000 -220,000

1,000 -50,000

8-100 Truck purchase for small systems, operating costs

for large system

Automated Scrapers 100,000 -1,000,000

3,000 -100,000

25-60 Labor and construction

costs

Front Mounted Scrapers

75,000 -615,000

1,000 -40,000

10-40 Labor and construction

costs

*Assumes 8% interest and 10 year loan payoff period

Figure4‐1:Estimatedtotalannualizedcostsfordifferentscrapingtechnologies

Figure4‐2:Averageestimatedtotalannualizedcostsforallscrapingsystemswithdifferentloan

payoffperiods

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Vacuum Truck Scraping Vacuumtruckscurrentlyonthemarketmayconsistofafullyintegratedtruckandvacuumoravacuumtankthatcanbetowedbehindatractor.Thetruckstravelslowlythroughthealleystypicallywithadjustablewingsthatspanthelane’swidthandcollectdepositedmanure.Themanurecanthenbetransportedelsewherewithsomemodelsincorporatingsprayingmodulestofacilitatelandapplication.Thesesystemsgenerallyareonlyoperatedinthelaneswhencowsarenotpresent,sothenumberofscrapingeventsperdayusuallyrangesfrom2‐3times,dependingonhowoftenthecowsaresenttothemilkingparlor.Figure4‐3displaysanexampleofamanurevacuumtruck14.ThreeVacuumTruckscenariosweremodeledusingtrucksof2,200,3,000,and4,300galloncapacities.Themodelassumesupfrontcapitalcostssuppliedforthevendorandextrapolatesoperatingcostsfromexpecteddistancestraveledupanddownlanesandalsotoamanuredropofflocation.AsseeninFigure4‐1,thetotalannualizedcostsofthethreesizesystemsarerelativelysimilar.Thistypeofsystemappearstobethemostexpensiveoptionforsmalldairieslessthan750headbutbecomestheleastexpensiveforlargerdairies,withthecostslevelingouttolessthan$15/head/yearfordairieswithgreaterthan2,000head.Thehighcostsforsmalldairiesareduetothelargeupfrontcostsassociatedwiththepurchaseofascrapertruck(Table4.1).Capitalcostsdominatethetotalannualizedcostforsmallerdairieswhileoperationalcostsassociatedwithdieselpurchaseandlabortendtodominatecostsforbiggerdairiesthatrequiremoretimeandfueltocollectallofthemanuregenerated.Thereareafewimportantpointsthatthemodelfailstotakeintoaccount.Firstly,itisassumedthatexistingfreestalldrivelanesaresuitabletowithstandrepeatedpassageofheavilyloadedmachinesthatcanexceed60,000pounds.Thismaybeinaccurateespeciallyforolderdairies,wherepossiblemodificationsmightincludethickeningconcreteinthelanesorreinforcingexistingconcreteandremovingobstaclespreventingalarge(upto11’talland14.25’wide)trucktopass.Additionally,somefarms,especiallylargerones,mightneedtopurchasetwoormoretrucks,eithertohaveonhandasabackuportousetheminconjunctionforlogisticalreasons.Themodelisespeciallysensitivetothiscostandaffectscostsonsmalltomediumsizeddairiesmuchmorethanlargerones.Lastly,thepotentialexistsforthirdpartycompaniestoprovideaservicethatcollectsmanurefromoneormorefarmsinanarea.Thisscenariowouldtransfermostoftheupfrontcostsfromthedairytotheserviceprovider,acasenotconsideredhere.

14Photosouce:http://www.menschmfg.com/manure_vac.html.

Figure4‐3:Anexampleofavacuummanurecollectiontruck

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Automated Mechanical Scrapers AutomatedMechanicalScrapersfunctiononapulleysystemintegratedwithacableorchainandelectricmotorthatpullscraperbladesupanddownthelanesoffreestallbarnsdepositingmanureintoacollectionandremovalsystemfortransportelsewhere.Twoautomatedmechanicalscrapingsystemcostsweremodeledusingvendorquotesforcableandchainsystemsandalsoinfrastructureconstructioncostsfroma1,500headdairythatsuccessfullyinstalledthistypeofsystem.Thetotalinstalledcostsofthesesystemsareestimatedtorangefrom$100,000and$1,000,000dependingonthesizeofthedairy.Theactualmechanicalscrapingsystemaccountedforonly20‐30%ofthetotalinstalledcostsoftheconversionfromflushtoscrape,whilelabor,construction,andmiscellaneousequipmentmakeupthedifference.Thetotalannualizedcostsforthistypeofsystem(Figure4‐1)arepredictedtobeamongthemostexpensivescrapingoptionsformostdairysizes,althoughthedifferentialbetweenfarmsizesislesspronouncedthanwiththeVacuumTruckscenario.Theannualoperatingandmaintenancecostsforthesesystemsareexpectedtorangebetween15and35%ofthetotalannualcostsdependingonthedairysize.Chainandcablereplacementcostsareexpectedtocontributeabout50%oftheannualoperatingcosts.Cablesmayrequirereplacementonceeveryyearwhilechainsrequirereplacementapproximatelyonceevery5years,butaregenerallymoreexpensivethancables.Figure4‐4andFigure4‐515displayautomaticscrapingsystemelements.

Afewimportantlimitationsofthemodelarethatconstructioncostsforinfrastructuresuchastrenches,gutters,holdingtanks,rubberpadding,andcable/chainhousingcanvarysignificantlydependingonthespecificlayoutofeachdairy.Forinstance,largerbarnsgreaterthan500’inlengthmayrequirespecialsystemswithmorethanonescrapingbladeperlanetoavoidexcessivemanureaccumulationinfrontofthescraper.Amoredetailed

15Source:http://extension.missouri.edu/p/G2531

Figure4‐5:Exampleschematicofanautomatedmechanicalscrapersystem

Scraper

ScrapedFloor

Figure4‐4:Exampleofanautomatedmechanicalscrapingsystem

39

assessmentofconstructionneedsandcostsforvarioussizeddairieswouldsignificantlyimprovemodelconfidence.

Tractor or Front Loader Rubber Mounted Scraping Frontmountedscraperscomeinavarietyofsizesandconfigurationsbuttheiroperatingprincipleissimilartoautomaticmechanicalscrapingsystemsexceptthattheyrequireamannedtractororskid‐steerloadertopushthemanuredownthelanestoacollectionpoint.Theyrequiresimilarinfrastructureastheautomatedsystemssuchasaconcretegutteranddrainagesystemandpossiblyastoragetank.Similartothevacuumtrucks,theyusuallyareonlyoperatedinemptybarnswhenthecowsareouttomilk(2or3timesperday).Figure4‐6depictsatypicalfrontmountedrubberscraper16.Threemodelsofrubbermountedscraperswereanalyzedinconjunctionwithpurchaseofamid‐sizedskidsteerloader.TheconcreteworkandlaborestimatesweresimilartotheAutomatedScraperscenarios.Thetotalinstalledcostofthesesystemsrangedfromabout$75,000–$610,000withtheskidsteerloaderandrubberscraperonlycontributing3‐25%ofthetotalinstalledcostscomparedtolaborandconstructioncostsforbarnmodifications(trenchesandholdingtanks).Thesetypesofsystemsmightbebestsuitedforsmallerdairieslessthan1,500headandrepresentthemid‐rangeexpenseoptionforlargerdairies(Figure4‐1).Operationalcostsforrubbermountedscrapersare10‐30%oftheannualtotalsystemcostestimated,withdieselfuelandlaborbecomingincreasinglydominantasdairysizeincreases.Limitationsofrubberscrapingaregenerallysimilartolimitationsfortheautomatedsystemsandvacuumtrucks.Abetterunderstandingofthespecificconstructioncostsrequiredforbarnmodificationsformanurehandlinginfrastructureandespeciallyhowthesecostsscalewithdairysizewouldimproveestimatessinceupfrontconstructioncostsarethemaindriveroftheinstalledcostsforallsizeddairies.LiketheVacuumTruckscenario,abetterunderstandingofhowdairieswouldultimatelyimplementthisstrategywouldalsobeextremelyhelpful.Forinstance,itispossiblethatlargerdairiesmightpurchasemultiplescrapersand/orfrontloaders/tractorsormightalreadyhavevehicles,leavingjusttheaddedcostsforthescraperitselfandassociatedmaintenancecostsfromuse.

16Photosource:http://www.menschmfg.com/manure_scrapers.html

Figure4‐6:Exampleofarubberfrontmountedscraperaddedtoaskid‐steerloader

40

4.1.3. Greenhouse Gas Emissions from Scraping Thegreenhousegasemissionsfromscrapingoperationsstemfromthedieselfuelenergy(VacuumTruckandFrontMountedScraper)orelectricity(AutomatedMechanicalScraping)needsofeachsystemandcanbecalculatedusingstandarddieselorelectricityemissionfactors.Thethreesystemshadmodeledannualemissionsrangingupto45MgCO2eq/yr(Figure4‐7).Theaveragedirectemissionsfromthethreescrapingtypesestimatedareaddedtosubsequentdirectemissionscalculatedforthedownstreamsolidsproductionsystems.

Figure4‐7:Averageestimatedoperationaldirectgreenhousegasemissionsfromthreedifferent

scrapingstrategies

4.2. Scrape to dry manure management options – Description and key assumptions MostCaliforniadairiesarelocatedinthestate’sCentralValleywheresemi‐aridorhotMediterraneanclimatesexist,characterizedbylongdryseasonsandhighnetannualevaporationrates.Californiadairiesalreadytakeadvantageofwarm,drytemperaturestohelpdryanddehydrateaportionofthemanuregenerated.The2012CAGHGinventoryestimatesthat87%ofmanurefromheifers(15%oftotaldairymanurevolatilesolids)(Table2.2)isalreadyunderdry‐lotmanagementwhichresultsfrommatchinganimalexcretionratesandpatternswithhousingandbeddingconditions,producingsolidmanurethatcanbecollectedperiodicallythroughouttheyear.SolidanddrylotmanurestorageshavefarlowerMCFvaluesthanliquidstorages(Table2.2),howeversolidmanuresutilizedfornutrientrecoveryoncroplandrequireverydifferentmanagementpracticesthanliquidmanures,primarilyincludingtransportationandapplicationusingspecializedtrucksor

41

tractorspullingmanurespreaderswhichtypicallylimitsusetopre‐plantapplicationsratherthanonestablishedcropsthroughoutthegrowingseason.Thedryingscenariosdiscussedhereconsiderpartialorfullyeardryingoftheavailablescrapedmanureassumedinthisreport(approximately45%ofmanureVSfromadultcowsor37%oftotalannualdairyVS)inadditiontothatalreadymanagedasadriedsolid(Table2.2).

4.2.1. Open Solar Drying Duetothelargeevaporativepotentialoftheclimateinmostareaswithdairies,solardryingofscrapedslurrymanurecanbeconsidered.However,itisimportanttonotethatasmallnumberofCAdairiesarebelievedtocurrentlyemployalargelyscrapedmanurecollectionsystemandnodairieswithasolardryingpadandoperationsasenvisionedherewereinterviewed.Thisscenarioshouldbeconsideredspeculativeandmaynotbeapplicabletomanydairies,givenvariablefarmtofarmconditions.AverageevaporationandprecipitationratesfortheBakersfieldandFresnoregionsareusedforillustration(Table4.2).Generally,thewintermonthsofNovemberthruFebruaryexperiencesmallornegativenetevaporationandwouldnotbepracticalforopensolarmanuredryingdesigns.Duringthesemonthsitisassumedthatmanureisdeliveredtoananaerobiclagoonasinthebaselinescenario.Foran8monthdryingseasonfromMarchthruOctober,anevaporationrateof2.09”forMarch(Fresno)isselectedasthedesignmonthconditionwithminimumnetevaporation.Ashorter6monthdryingseasonfromAprilthruSeptemberisalsoconsideredastheAprildesignnetevaporationrateof4.95”(Fresno)ismorethantwicethatofthepreviousmonth.Dryingrateinverselyreducestherequiredpadsize.Duringsummermonths,netevaporationratesare2‐3timesthatofthedesignmonthswhichmeansthepadswillbeproportionallyoversizedandprovideadditionalspaceforstorageandhandlingofsolidsfromothermonthsasneeded.

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Table4.2:MonthlyaverageprecipitationandevaporationdataforBakersfieldandFresno,CA.

Bakersfield Airport (inches) Fresno Airport (inches)

Month Average Precip.1

Average Evap.2

Net Evap.3 Average Precip.1

Average Evap.2

Net Evap.3

Jan 1.04 1.44 0.4 2.01 1.26 -0.75

Feb 1.18 2.25 1.07 2.08 2.08 0.00

Mar 1.00 4.13 3.13 1.85 3.94 2.09

Apr 0.74 5.95 5.21 1.08 6.03 4.95

May 0.23 8.35 8.12 0.28 8.75 8.47

Jun 0.06 9.58 9.52 0.06 10.43 10.37

Jul 0.06 9.94 9.88 0.06 11.02 10.96

Aug 0.06 8.85 8.79 0.06 9.67 9.61

Sep 0.06 6.62 6.56 0.06 6.99 6.93

Oct 0.31 4.47 4.16 0.48 4.42 3.94

Nov 0.55 2.24 1.69 1.11 2.25 1.14

Dec 0.84 1.35 0.51 1.76 1.21 -0.55

Year 6.12 65.17 59.05 10.89 68.05 57.16 1http://www.water.ca.gov/floodmgmt/hafoo/hb/sss/precipitation/.2AverageClass‘A’panevaporationrates,averagedfromover40yearsdatathru2010:

http://www.water.ca.gov/landwateruse/annualdata/agroclimatic/.3Netmonthlyevaporationcalculatedbysubtractingprecipitationfromevaporation.

Toestimatethepadsizeneededforopensolardryingofthescrapedmanureproductionvolume,manureiscollectedatleastdaily(13%TS)andspreadintocurbedconcretelanestoadepthnogreaterthanthemonthlynetevaporativerate.Fortherangeofdairysizesevaluatedwith300‐10,000adulthead,approximately3,000‐100,000tonsofwetmanureperyearisgenerated,respectively.Onceindividuallanesarefilled(i.e.1‐7days),freshmanurewillneedtobedistributedtosubsequentlaneswhilethepreviouslanesdrytotheselectedsolidscontentof70%.Thetotalevaporativelossvolumeestimatedfromdryingfrom13%to70%TS[ac‐ft],dividedbythedesignmonthevaporationrate[ft/month]givestheestimatedpadsizeforanOpenSolarDryingscenarios.Evaporationratesformanureslurrydryingarenotexpectedtoequalevaporationratesasmeasuredforwaterfromevaporationpans(Hjorthetal.2010),anddryingtomoreorlessthan70%TSmaybeacceptable,however,thesevaluesareusedheretofacilitateafirstorderestimate.Inorderforamanuredryingoperationtobeincompliancewithlocalwaterandbuildingcodes,itmustbeprotectiveofsurfaceandgroundwaterresources.Thedryingareamustpreventsignificantleaching,beabletowithstandfrequentheavyequipmentuse,andhaverainwaterandrunoffcollectionsystemsinplace,ataminimum.Specificdesignrequirementswillrequiredevelopmentandreviewinconjunctionwithlocal,state,andregionalpermittingagenciesonacasebycasebasis.Forthesescenarios,a6‐8”thickreinforcedconcretepadisproposedatanestimatedcostof$3.50/ft2.Thispricewasselectedasamidrangevaluelistedfor6”reinforceddairysilageslabs,feedlanes,andtankerpadsinthe2015CAAssessorsHandbookforRuralBuildingCosts(CSBOE,2015)

43

althoughrangesfrom$2.95‐$6.80wereprovidedandindicatecostsmightvaryconsiderablyduetosite,design,andmarketdetailsnotevaluatedhere.Alternativesurfacessuchasasphaltorcompactedengineeredsoilsmeetinggroundwaterprotectionstandardsmightbeavailableatlowerinstalledcostsalthoughalsolikelyaccompaniedbyhigheroperationalandmaintenancecostsandwerenotconsideredhere.Forsimplification,itisassumedthatthedryingareawillutilizethedairiesexistingrunoffmanagementsystemandstoragelagoon,whichshouldalreadybesizedtoaccommodatethedivertedmanure.Thisassumptionmaynotbevalidifspacewithinanexistingdairyisnotavailable.Evenifspaceisavailable,landisavaluableresourceinandaroundCAdairyfarmsandalandrentvalueof$250peracreperyearhasbeenassignedtoacknowledgethisaspect.Thisvaluewasselectedasamoderatevalueforcroplandintheregion(CASFMRA,2013),althoughitmayvarygreatlycontingentonmanyfactors.Operationaldemandsforopensolardryingareexpectedtoincludeperiodicscrapingandhandlingofthemanuresolidsduringandafterdrying.Inordertofacilitateestimationofequipment,labor,andutilitiescosts,aspreadsheetmodeldevelopedfortheplanningofco‐compostingfacilitiesformixturesofdairymanureandotherorganicwasteswasadaptedandutilized(CornellUniveristy,2001).KeyassumptionsusedinthemodelarelistedbelowinTable4.3withotherinputsleftattheirdefaultvalues.Table4.3:OpensolardryingCo‐Composterv2amajormodelassumptionsInput Field Description

Dairy Sizes 300, 750, 1500, 3000, 5000, and 10000 adult head

Management System Windrows turned with 135 hp, 3yd3 bucket loader

Windrow Dimensions 8’ height x 16’ width x 100’ length

Composting Period 30 days

Turning Frequency 7 days

Curing Period none

Fresh or Finished Storage none

New Leachate Detention Pond none

Final Compost Screening none

Labor Cost $20/hr

Electricity Cost $0.148/kWhr* Inflation Rate (1991 or 2000 to year 2015)

2.5%/year**

*(http://www.eia.gov/electricity/monthly/epm_table_grapher.cfm?t=epmt_5_6_a) **(http://data.bls.gov/cgi‐bin/cpicalc.pl)Outputsfromthemodelincludeequipmentcapitalcosts,dieselandelectricityestimates,andlaborestimatesforhandlingandturningofthematerial.DieselandelectricalusageestimatesareusedtoestimateresultingdirectGHGemissionsbymultiplicationwithappropriateconversionfactors(CARB,2014).ToestimateGHGemissionsincurredduringthedryingprocess,itisassumedthattherewillbesomeanaerobicactivityastheslurrydehydratesandtransitionstoasolid‐likeemissionsprofileasthematerialdehydratesmorefully.Asactualdryingrateswilldepend

44

onmanyfactorsincludinginitialsolidscontent,layerthickness,precipitationfrequency,windspeed,andmanyotherfactors,itisdifficulttoconfidentlyselectanappropriateMCFvaluewithoutadditionalresearchandassessmentinthisarea.Asaninitialestimate,theaverageofliquid/slurryGHGemissionsfactorsandsolidsstoragevalues(Table2.2)areusedhereforeachmonthdryingisperformed.Capitalcosts(padandequipment)wereannualizedfora10‐yeartermat8%interestandoperationalcosts(labor,utilities,landrent)addedforthemonthsoperatedtoarriveatanaveragetotalannualizedcost.Itisimportanttorecognizethatadditionalcosts,including,butnotlimitedto,specializedengineering,development,insuranceandpermittingthatmayberealizedarenotincludedintheexistingcostestimates.Also,anycostsassociatedwithadditionalequipment,infrastructure,transportation,orlaborfortransportationandutilizationofthesolidsproducedarenotconsidered.NorevenueforsaleorexportofsolidsisassumednoranyGHGemissionsfromtransportationoruse.

4.2.2. Closed Solar Drying

Inordertoextendthepotentialforsolardryingthroughouttheyear,closedsolardryingtechnologysimilartospeciallyengineeredgreenhouseswasalsoconsidered.Thistechnology,whichhasinstallationsinuseinCaliforniaandthroughoutNorthAmerica,isusedprimarilyfordryingofbio‐solidsandimprovessolarcollectionefficiency,blocksprecipitationandrunofffromsolidswhiledrying,andaddsconvectiveaircirculationandautomaticagitationtomaximizedryingrateandefficiency.Greenhousetypesolardryershavehighcapitalcostsandrelativelylowoperationalcostsprimarilyfromfanstoenhanceaircirculationandfromautomatedsolidsagitationequipment.SolardryinggreenhouseshavebeendemonstratedtoreducepathogensinsewagesludgetocomplywithEPArecommendlevels(Bennamoun,2012).WhereodorsorVOCemissionsfromdryingareaconcern,specializedbio‐filterscanbeconstructedtotreattheairfromthedryinghouse,furtheraddingtothecostandcomplexity.Severalvendorsforthistypeoftechnologyexist,howeveronlyoneUSvendorprovidedbudgetarycostandperformancedata,whichwasusedtoextrapolatecostsfor300‐10,000headdairiesdryingthescrapedmanureassumedavailableinthisreport.Assuch,theseresultsareexploratorywithahighdegreeofuncertainty.Thesystemisassumedcapabletoincreasesolidscontentfrom13%TSto70%TSwitha15‐20dayresidencetimeanda0.7exponentialscalingfactorwasusedtoextrapolatecostswherenotspecificallyprovidedbythevendor.Abaselinelaborcostof$70,000/yearanda$750,000capitalcostforabio‐filtrationsystemwereincludedforalldairysizes.Electrical,labor,interestratessimilartothesolardryingscenarioswerealsousedforcostestimation(Table4.3).AswiththeOpenSolarDryingscenarios,GHGemissionsfromsolardryingarenotwellunderstoodandadditionalevaluationwouldbenecessarytoestimatewithconfidence,thereforetheaverageofliquid/slurryGHGemissionsandsolidsstorageemissionfactorvalues(Table2.2)werealsousedinthissolardryingscenario.

4.2.3. Forced Evaporation with Natural Gas Fueled Dryers

45

Anotheroptionconsideredfordryingofscrapedmanureisdehydrationinengineereddryersusingnaturalgasfuel,asiscommonlyemployedfordryinginthebio‐solidsorethanolbyproductsindustries.Thisoptionhastheprimarybenefitofbeingabletoconvertscrapedmanuretodriedsolidsondemandandcontinuouslythroughouttheyearwithamuchsmallerfootprintcomparedtosolardryingoptions.Notalldairieshaveeasyaccesstonaturalgas,however,forthisestimateitisassumednaturalgassupplyisavailableonsiteandcostsforinfrastructureupgradesnecessarytoensurenaturalgasdeliveryhavenotbeenincluded.Solar‐thermaldryingsystemsmayalsoexistorcanbedevelopedforthisapplication,butwerenotevaluatedaspartofthiswork.BudgetarycapitalandtheinstallationcostswereprovidedbytwoconfidentialUSvendorsofhotairdryersoperatedwithnaturalgasfordryingofbetween900‐29,000wettonsofmanure(13%TS)toafinalconcentrationof70%TS.Anexponentialeconomicscalefactorof0.7wasusedtoextrapolatecostsfordairiesupto10,000head.Electricityandnaturalgaspriceswereassigned$0.148/kWhand$5.52/MBTU(EIA,2015).Laborcostsforeachsystemwereassumedtobe$70,000/yearandcapitalinterestratetobe8%fora10‐yearterm.DirectGHGemissionfactorsfromprocessingwereassumedtobe0.277kgCO2eq/kWhand66.8kgCO2eq/MMBTU(CARB,2014),andusedtoestimatenetGHGmitigationpotential.

4.2.4. Composting Composting,differentiatedfromsimplemanuredryinghere,requirescreatingandmaintainingconditionsforrawmanuresthatallowforproperaerobicdecompositiontooccur.Compositingoforganicmaterialsisgenerallyoptimumforsolidscontentsbetween40‐60%,carbon‐to‐nitrogen(C:N)ratiosof20‐40,andbulkdensitiesunder40lb./ft3,.Theseconditionsallowaerationtobeaccomplishedbyfrequentturningofpilesorforcedaerationinstaticpiles.Unfortunately,freshlyscrapeddairymanurewithoutbeddingisnotsuitablefordirectcompostingwithsolidscontentscommonlybetween8‐14%andahighbulkdensitysimilartowater.HowevertheC:Nratioofaround20isacceptable.Inordertoincreasesolidscontentanddecreasebulkdensity,abulkingagentmustbeconsidered.Optionsforbulkingagentsarediverseandincludestraw,hay,woodchips,sawdust,cardboardorpaperproducts,agriculturalbyproductssuchasshellsandhulls,ordriedmanuresorcomposts.Selectionofanyofthesematerialswillultimatelybebasedonavailability,cost,andattentiontotheinitialsolids,C:Nratio,density,andotherparametersthatmightbeaffectedwhenmixedwithmanure.Duringcomposting,organicmatterbreaksdownaerobicallyatsustainedelevatedtemperaturesandthesolidsvolumeisreducedsignificantly,which,withvaryingamountsofhandlingandmanagement,canproduceahighqualityfertilizerandsoilamendmentproduct.CompostingcanbeconductedyearroundinCaliforniawithproperattentiontorunoffcollectionandmanagementfromthecompostingsite.Advancedfabriccoversorstructuresaresometimesemployedtominimizetheimpactofprecipitation.AswiththeOpenSolarDryingscenariosdescribedpreviously,theCoComposterv2aspreadsheetmodeldescribedpreviously(CornellUniveristy,2001)wasutilizedtofacilitatecostestimationsforthepad,equipment,labor,materials,andlaborforthe

46

fractionofscrapedmanurecollectedformodeleddairies.WheatstrawwasselectedasaninitialbulkingagentduetoitsstatewideavailabilityanduniformitythroughoutthestateandbeneficialbulkingandC:Nproperties,althoughmanyotheravailablebulkingagentsmaybepreferredforusedependingonlocalavailabilityandcost.KeyassumptionsusedinthemodelarelistedbelowinTable4.4withotherinputsleftattheirdefaultvalues.Table4.4:CompostingscenarioCo‐Composterv2amajormodelassumptionsInput Field Description

Dairy Sizes 300, 750, 1500, 3000, 5000, and 10000 adult head

Manure Characteristics Total Solids = 13%, C:N ratio = 19, Density = 62 lb/ft3, Added wastewater per cow = 0.5 ft3/head

Bulking Agent Wheat Straw: Total Solids = 90%, C:N ratio = 80, Density = 8 lb/ft3, $130/ton delivered

Mixed Compost Total Solids = 75%, C:N ratio = 40, Density = 32 lb/ft3

Compost Management Systems (averaged results from 4 systems listed)

Windrows turned with 135 hp, 3yd3 bucket loader Windrows turned with tractor (100 hp) drawn PTO turner Windrows turned with medium self-propelled turner Extended aerated static piles/bio-drying

Pad Specifications 6-8” reinforced concrete, $3.50/ft2

Windrow Dimensions 8’ height x 16’ width x 100’ length

Composting Period 90 days

Turning Frequency 7 days

Curing Period none

Fresh or Finished Storage none

New Leachate Detention Pond none

Final Compost Screening none

Labor Cost $20/hr

Electricity Cost $0.148/kWhr* Inflation Rate (1991 or 2000 to year 2015)

2.5%/year**

*(http://www.eia.gov/electricity/monthly/epm_table_grapher.cfm?t=epmt_5_6_a) **(http://data.bls.gov/cgi‐bin/cpicalc.pl)FortheCompostscenariosasmodelled,theinitialmoisturecontentof75%isstillhigherthanthedesiredrangeof40‐60%,howeveritisdifficulttoincreasedrymattersufficientlyusingstrawforbulkingwithoutexceedingaC:Nratioof40.Forthisanalysis,theseconditionsweredeemedacceptablewithestimatedinitialbulkdensityof32lb/ft3.Themassofbulkingagentaddedisalmost20%ofthemanuremass,althoughitapproximatelydoublestheinitialvolumeofthecompostmatrix.Duringcomposting,thesolidsvolumeisexpectedtoshrinkagainbyabout50%suchthattheinitialvolumeisestimatedtobecomparabletotheinitialmanurevolume.ItisimportanttonoteinthisscenariothattheVSadditionfromthebulkingagentresultsinaVSincreasecomparedwith

47

theinitialmanureofapproximately1.5times,whichincreasesthepotentialforGHGemissionsifimproperlyallowedtodecomposeanaerobically.Aswithallmanuremanagementscenariosproposed,surfaceandgroundwaterresourcesmustbeprotectedtobeincompliancewithlocalwaterandbuildingcodes,however,therequirementsforachievingthisarenotstraightforward.Thecompostareamustpreventsignificantleaching,beabletowithstandfrequentheavyequipmentuse,andhaverainwaterandrunoffcollectionsystemsinplace,ataminimum.Specificdesignrequirementswillrequiredevelopmentandreviewinconjunctionwithlocal,state,andregionalpermittingagenciesonacasebycasebasis.Mostdairiesinthestateoperateunderageneraldairywastedischargerequirementorder(CRWQCB,2013),howeverrequirementsfordairymanurecompostingoperationsarenotexplicitlydescribed.Ageneralcompostingwastedischargerequirementsorderisalsocurrentlyinthedraftprocess(CSWRCB,2015),whichproposesthatfacilitiescompostingmanures(TierII)mayrequirecompostpadstomeetahydraulicconductivityof1x10‐5cm/s,eitherthroughaminimumofonefootofcompactedsoils,orwithasphaltorconcrete,orthroughalternativeengineereddesignspossiblyinconjunctionwithagroundwatermonitoringplan.However,thisguidanceiscurrentlyindraftstageandisunclearwhetheritwillberelevanttodairiesalreadysubjecttotheexistinggeneralorder.Dairiesandcompostfacilitiesarealsoabletopursueindividualpermitsshouldtheybeneeded,howeverwithmuchgreatertimeandcostincurred.Forthesescenarios,a6‐8”thickreinforcedconcretepadisproposedatanestimatedcostof$3.50/ft2asassumedinthepreviousscenarios,aswellasanannuallandrentorleasecostof$250/acre/year.Also,aswiththeOpenSolarDryingscenarios,itisassumedthatnonewleachatedetentionpondisneededasanexistinganaerobiclagoonmightbeabletoaccommodatethenecessaryvolumes.OutputsfromtheCo‐CompostermodelwereobtainedforeachofthefourmanagementscenarioslistedinTable4.4wereaveragedtoobtainasingleaveragecostforcompostoperationsasmodelled.Thefirstthreescenariosinvolvingturningofwindrowswithdifferenttypesofequipmentwereallverysimilarandthefourthoptioninvolvingextendedaeratedpilesconsistedofslightlyhighercapitalcostsandloweroperationalcosts,butverysimilarannualizedtotalcosts.Theaeratedpileoptionalsohadlowerdieselusage,buthigherelectricaluseforuseofairblowers.InordertoestimatetheGHGreductionpotentialfromcomposting,thedivertedscrapedmanurewasassignedMCFandN2Oemissionsvaluesforcompostingwhicharesimilartothatofdrylotmanure(Table2.2).IPCCCompostMCFvaluesrangefrom0.005‐0.015andavalueof0.015wasusedhere(CARB2014).ReferencedirectN2Oemissionfactorsforcompostingrangefrom0.006‐0.1gN20/gN(IPCC,2006)andastheyareexpectedtobeslightlyhigherthanthatseenfromsolidstoragealone(0.005),avalueof0.02gN20/gNwasselected.Thesearebothsimilartothedry‐lotemissionsnumbers,sothedrylotN2Oemissionsfactorsforvolatilizationandrunoff/leachingwerealsoapplied.

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4.3. Estimated System Costs Detailedsummariesofcapitalcosts,operatingcosts,directemissions,andemissionreductionestimatesforarangeofmodelleddairysizesareprovidedinthefollowingAppendices:

Appendix4.2:ScrapetoOpenSolarDrying(6monthscenario) Appendix4.3:ScrapetoOpenSolarDrying(8monthscenario) Appendix4.4:ScrapetoClosedSolarDrying Appendix4.5:ScrapetoForcedEvaporationwithNaturalGasFueledDryer Appendix4.6:ScapetoCompostingwithBulking

4.3.1. Open solar drying

EstimatesofrequiredevaporationpadareasandcostsareshowninTable4.5forboth6monthand8monthscenariosandrangefrom0.4‐29.9acres,orfromapproximately$65,000toover$4.5millioninstalledcost,dependentonmodeleddairysize.Table4.5:OpenSolarDryingestimatedpadsizesandcostsfor6and8monthscenarios

Dairy Size Evap. Pad Ave.

Area (6 mo.) Evap. Pad Ave.

Cost (6 mo.) Evap. Pad Ave.

Area (8 mo.) Evap. Pad Ave.

Cost (8 mo.)

Adult Cows acres $ acres $

300 0.4 $65,660 0.9 $142,100

750 0.9 $138,005 2.2 $329,105

1,500 1.9 $284,060 4.5 $685,370

3,000 3.8 $577,535 9.0 $1,370,600

5,000 6.3 $961,100 14.9 $2,270,135

10,000 12.6 $1,920,695 29.9 $4,557,875

Equipmentcostsforallscenariosareestimatedat$214,000forafrontendbucketloaderregardlessofdairysize.Forsmallerdairies,thecapitalcostsforpadareonlyabout15‐30%ofthetotalcapitalasthescrapingandloadercostsdominate,howeverpadcostsincreaseto70‐85%ofthetotalcapitalfora10,000headdairyasmodeled,dependingonwhether6or8monthoperationsareassumed.Landrent/leasecostsrepresentabout20‐30%ofthetotalO&Mamountforalldairysizes,respectively.Directemissionsfromscrapinganddryingoperationsareapproximately1%oftheestimatedGHGsavingspotential.Thetotalestimatedannualizedcostperheadforascrapinganddryingscenariorangesfrom$222/headfora300headdairyto$60/headfora10,000dairywithsixmonthoperations,or$271‐109/headforeightmonthoperations(Figure4‐1).Norevenuesareassumedforsaleofexportofsolidsasitisassumedthatallsolidsandnutrientswillcontinuetoberecycledonsite,however,ifamarketforsolidsexisted,breakevensalesrevenuefromsolidsdriedto70%TSwouldneedtorangefrom$35‐165/ton.

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4.3.2. Closed Solar Drying Closedsolardryingtechnologyisalsoestimatedtorequireasignificantarea,andatanextremelyhighcost,asshowninTable4.6.TheO&Mcostsforallsizedairiesinvestigatedonlyaccountforapproximately10‐20%oftheannualizedcostestimate,furtherillustratingthecapitalintensity(Figure4‐1).Table4.6:ClosedSolarDryingscenariocostssummary

Dairy Size Closed Solar Dry

Area Required Solar Drying Capital Cost

Total Annualized Cost per head

Adult Cows acres $ $/head/yr

300 0.3 $1,715,047 $1,179

750 0.7 $3,224,457 $797

1,500 1.5 $5,198,359 $614

3,000 3.0 $8,380,616 $484

5,000 5.0 $11,915,980 $410

10,000 10.0 $19,210,533 $332

Itisunlikelyacapitalinvestmentofthismagnitudewouldbemadeforthispurposeunlessahigh‐valueproductorcoproductwasalsoproduced,asthebreakevensalesrevenuefromsolidsalonedriedto70%TSwouldneedtorangefrom$200‐700/ton.

4.3.3. Forced Evaporation Using Natural Gas Fueled Dryers

Unlikeforthesolardryingscenariosdescribed,aForcedEvaporationscenariowouldrequireamuchsmallerfootprintforinstantaneousandcontinualproductionofdriedsolidsandcapitalinvestmentdominatedbyequipmentandinstallationcosts;howeveroperationscostswillbehigherprimarilyduetonaturalgasfueluseasshowninTable4.7.Table4.7:ForcedEvaporationscenariocostsummaryusingnaturalgasfueleddryers

Dairy Size Forced Drying Capital Costs

Forced Drying O&M, Labor,

Utilities Costs

Total Annualized Cost per head

Adult Cows $ $/yr $/head/yr

300 $288,329 $135,489 $659

750 $542,087 $233,773 $453

1,500 $873,934 $397,581 $374

3,000 $1,408,926 $725,362 $327

5,000 $2,003,282 $1,162,572 $304

10,000 $3,229,622 $2,256,556 $282

Thedryingequipmentaccountsfor70‐85%ofthesystemcapitalcostwiththescrapingsystemasthebalance.O&Mcostsaredominatedbytheutilitiescostsforfuelandelectricity,whichaccountfor50%(300headdairy)to95%(10,000headdairy)ofthecost.Asestimated,theoperationalcostsaccountfor70‐80%oftheannualizedcostslistedfor

50

smalltolargedairies,respectively.Aswiththeotherscenarios,abreakevenpriceforsolidssalesalonedriedto70%TSwouldneedtorangefrom$150‐400/ton.

4.3.4. Composting KeyCompostingscenariocostsareshownbelowinTable4.8.Compostingscenariosassumeanareaof1‐20acreswouldbeneeded,dependentondairysize,whichissimilartotheOpenDryingscenarios.EquipmentcostsareslightlyhigherthanthoseforOpenDrying,duetoadditionalspecializedequipmentnecessary.Labor,maintenance,andutilitiescostsareapproximately2‐3timesthoseestimatedfortheOpenSolarDryingcases,mainlyduetotheextendedduration(90‐days)assumedforcompostingcompletion.ThemajordifferenceanddominatingO&Mcostasmodelled,isforthecostforabulkingagent,whichhereisassumedtobewheatstrawatpriceof$130/tondelivered.Withtheseassumptions,thetotalannualizedcostsrangefromover$500‐700perheadperyearconsideringa10‐yearterm.Table4.8:Compostingscenariocostssummary

Dairy Size

Compost Pad Ave.

Area

Compost Pad Ave.

Cost

Compost Equipment Ave. Costs

Compost Bulking

Materials Ave. Cost

Compost O&M, Labor, Utilities, Ave.

Costs

Total Annualized Ave. Cost per head

Adult Cows

acres $ $ $/yr $/yr $/head/yr

300 0.9 $130,839 $287,949 $120,815 $14,709 $740

750 1.8 $266,998 $300,449 $302,037 $36,732 $613

1,500 3.2 $494,839 $320,949 $604,072 $73,383 $567

3,000 6.3 $959,849 $361,949 $1,208,144 $146,684 $546

5,000 10.3 $1,567,956 $484,483 $2,013,553 $166,457 $536

10,000 20.3 $3,087,429 $667,816 $4,027,146 $332,917 $515

Itisestimatedthatuptofivetimesmorecompostmassandvolumewillbeproducedthanfromsimplesolidsdryingbecausemassisaddedforbulkingagentandmoisturewillberetainedthroughthecompostingprocess.Aswiththeotherscenarios,abreakevenpriceforcompostsalescanbecalculatedandwouldrangefromapproximately$60‐85/tonasmodelled.Forcomparison,ifitisassumedthatano‐costbulkingagentwereavailable,thisbreakevenpricewoulddropto$10‐35/ton,stillinclusiveofbulkingmaterialandcomposthandlingcosts.Additionalcombinationscenarioswherebyopensolardryingispracticedduringthedryseason,andcompostingduringthewetseason,canbeevaluatedandthecostsareexpectedtoliebetweenthetwocostextremesforcompostingwithbulkingandopensolardrying.Apilotprojectco‐compostingdairymanureandgreenwastewasconductedin2003‐2005attheHighway59LandfillinMerced,CAandevaluatedcompostingofapproximately65%manurewith35%greenwastebymass(50%/50%byvolume)(SustainableConservation,2005).Netproductioncostsbetween$10‐20/ton,withsalespricesfrom$10‐30/tonforvariousqualityproductswerereported,however,itshouldbenotedthatthisproject

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utilizeddrymanureatanetcostincurredonlyfortransportationandgreenwastewasavailableatanegativecost(tippingfeereceived).Asummaryoftotalannualizedcostsperheadfora10‐yeardebttermisshownformultiplescrapescenariosinFigure4‐8.

Figure4‐8:Totalannualizedsystemcostsforscrapemanuremanagementscenarios

4.4. GHG mitigation costs GHGmitigationcostsforscrapescenariosondairysizesfrom300‐10,000adultheadareshownbelowinFigure4‐9.Aneconomyofscaleexistssuchthatlargerdairieshavelowermitigationcostsperanimal,which,ifaparticularscenariowasimplementedondairiesstatewidestartingwiththelargestdairiesfirst,wouldresultinGHGmitigationpotentialsandcostswouldasshowninFigure4‐10.

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Figure4‐9:GHGmitigationcostsforscrapescenarios

Figure4‐10:GHGmitigationpotentialandcostsforscrapescenarios

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Aswiththeanaerobicdigestionscenariosdiscussedpreviously,itmaybeunreasonabletoassumethatwidespreadadoptionofaparticularmanuremanagementscenariowouldoccuronalldairieswithinarapidtimeframe,especiallygiventhedis‐economiesofscaleexpected.Estimatedmitigationpotentialsforalldairiesover300head,aswellasforasubsetofdairiesover2000headareshowninTable4.9andindicatethatapproximately50%ofthemitigationpotentialmightbeachievedfor35‐40%ofthecostwhentargetedtothelargest225dairies.TheScrapetoOpenSolardryingscenarioshavealowerpotentialmitigation(2‐3TgCO2eq/yr)thantheotheroptionsprimarilyduetotheirpartialoperationthrutheyearaswellasrelativelyhigherMCFfactorselected.IfactualMCFfactorswerefoundtobelowerinthesescenarios,mitigationpotentialwouldbehigherandatalowercostperton.Table4.9:Mitigationpotentialand10‐yearcumulativecostsfordairiesover300and2000headonly



≥ 2000 milk cows/dairy or largest 225 dairies (~800,000 cows) Scenario Descriptions

Scrape diversion, and Mitigation Potential

(Tg /y)

10-year cost (Billion $)


(Tg/y)

10-year cost

(Billion $) Open Solar Drying (6 mo.) 2.2 1.6 1.1 0.6

Open Solar Drying (8 mo.) 3.0 2.4 1.4 1.0

Closed Solar Drying (12 mo.) 4.3 10.0 2.1 3.7

Forced Evap. (Nat. Gas) (12 mo.) 5.4 6.3 2.6 2.6

Compost with Bulking (12 mo.) 4.9 9.5 2.4 4.3

4.5. Impact on dairy management Thereareseveralmajorimpactsonadairy’soperationthatwouldbeincurredbyshiftingasignificantportionofmanuretowardsascraped,drymanureproducingmanagementsystem,inadditiontothecapital,land,andoperationalcostsdiscussedpreviously.Flushingwithrecycledwaterallowsmultiplecleaningsoflanesthroughouttheday,regardlessofwhethercowsarepresent,whichdairiespreferforcowcleanlinessandhealth.Automatedscrapingsystemscanbeoperatedfrequently,butalsocanhaveahighercostthanotherscrapingoptionssuchasvacuumingandtractorscraping,whichneedtobeperformedwhencowsareoutofthebarn2‐3timesperdayformilking,requiringgreateroperationalcoordination.Also,whetherduetotractor,vacuumtruck,orsolidsmanurehandlingoperations,trafficinandaroundthedairywouldincreasesignificantly,increasingwearonsurfacesandsafetyliabilityonexistingfacilitieswhichlikelywerenotdesignedforsuchuse.Asscrapingof100%ofthemanuremaynotbeeconomicallyfeasible,mostscrapetodryoperationswouldbeadditivetotheexistingflushsystemratherthanreplacingit.Redundantsystemscanbemorerobust,howeveralsocanbeinefficientandmoredifficult

54

tomanageandmaintain.Itisunclearwhetherodors,vectors,ordustandparticulateswouldbesignificantlydifferentonthedairy.Also,asnotedalready,manuresolidstobeusedforfertilizerandsoilamendmentrecoveryvaluehavedrasticallydifferenthandlingandapplicationrequirementsinvolvingincreasedtrucktrafficthroughouttheyear.Forceddryingmaynotbeapracticaloptionformanydairiesifanaturalgassupplyisnotalreadyavailableatornearthedairy.

4.6. Environmental discussion Asnotedpreviouslyinthecostdiscussionsection,protectionofwaterqualityondairiesrequiresthatareaswheremanureismanagedbeconstructedandmaintainedinaccordancewithsuitableengineering,operational,andregulatoryparametersforeachdairy.Overallwateruseondairyfarmsisnotexpectedtobegreatlyimpactedbyaswitchtoscrapingalonesinceflushwaterisnormallyrecycledwaterfromthelagoonandmilkparlor,andlagoonwatermakesuponlypartoftheirrigationwaterdemandforcrops,whichwouldnotbeinfluencedbyashifttodrymanagementsystems.However,additionalinvestigationintothistopiciswarranted.Watercurrentlycontainedinliquidmanuresmighttypicallyconstitute5‐20%ofwaterusedforirrigationwater(Changetal,2005),andthereforelossofwaterthroughevaporationmightrequireacommensurateincreasefromirrigationsources.Inarecentreport,itwasclaimedthattheswitchtoscrapesystemshaspotentialtoincreaseparticulatematter,volatileorganiccompounds,andammoniaemissions(SustainableConservation,2015),althoughlittledatawasprovidedandtheseclaimsneedfurtherresearchandsubstantiationforCaliforniaconditions.GHGemissionsfromelectricityandfuelconsumptionwillincreaseduetoscrapingandprocessingactivity,(capturedintheexistingestimates),howevermanuredistributionwillfurtherincreasethisnumberandadditionalaircontaminantssuchasNOxandSOxfromincreasedtransportationemissionsmayalsobesignificant.InparticularfortheForcedEvaporationscenarioemployingnaturalgasfueleddryers,additionalcriteriapollutantsmayposeasignificantenvironmental,health,orcostburdenforadditionalmitigation.

4.7. Revenues and incentives Dewateringandconcentratingmanurenutrientsmayfacilitatetheabilitytoeconomicallyexportnutrientsfurtheroffsite,howeveramarketforsuchproductswouldneedtobedevelopedandthefarmlevelneedsfornutrientswouldneedtobesupplementedaccordinglyforfarmswherenutrientswerenotsurplustocropneeds.Compostorstandardizedsolidsmanureproductsmightcurrentlybeabletosellfor$10‐20/tontoday,howevermarketdynamicswoulddictatewhetherahigherqualityproductcouldcommandahigherpriceorifasubstantialamountofdriedmanureorcompostbecameavailableonthemarket,whetherpricingwouldbesuppressed.Increasedsolidsproductiononsitecouldalsooffsetexistingbeddingcostsalthoughitispossiblethatexistingsolidmanureproductionfromheiferordry‐lotsystemsmayalreadybesatisfyingthisneedtosomeextent.

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4.8. Barriers to adoption Themajorbarriertoadoptionforimplementingincreasedscrapeanddrymanureproduction,asidefromcost,willbetheeffectsofusingmanureswithincreasedsolidsonmanagementofmanure,farmlaborandnutrientrecoveryinthecroppingsystem.Mostlargedairieshaveinterconnectednetworksofpipingorirrigationfurrowsthroughouttheirfieldsallowingthemtodeliverwaterandnutrientsefficientlythroughoutagrowingseason.Useofsolidsfornutrientorsoilamendmentrequirestransporttothefieldandmorerestrictedacceptabletimesforapplicationofnutrients.

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5. Solid/Liquid Separation

5.1. Overview of technology and adoption status Dairiescommonlyusesolid‐liquidseparationtoseparatesolidsfrommanureforreuseforbeddingortodivertsolidsfromanaerobiclagoons.Separatingsolidscanreducegreenhousegasemissionsfromlagoonsbecauseitdivertssomeorganicmaterialsuitableformethanogenesisfromlagoons.Ithasbeenreported,however,thatthemostlylargersolidsremovedbythesesystemshavelowerdegradabilityandlowermethanepotential(Ricoetal.,2007).Therefore,thedegreetowhichgreenhousegasemissionscanbereducedisafunctionofboththepropertiesandcompositionofthesolidsandtheefficiencywithwhichtheyareremoved.ForCaliforniadairies,authorsofarecentreporthypothesizethatmanyofthedairiesthatareinapositiontousemanuresolidsforbeddingmayhavedonesoalreadyduetocostsavingsfrombeddingmaterials(SustainableConservation,2015).Therearethreemaintypesofsolid‐liquidseparationtechnologies:gravity,chemical,andmechanical.Gravityseparationisusuallyaccomplishedthroughtheuseofsettlingbasinsorinclinedscreensalsoknownasweepingwallsthatdon’tallowpassageoflargesolids.Accordingtoa2011two‐countysurvey,mostdairies(60‐70%)reportedusingsomesolidseparationwhile30‐40%ofdairiesusegravityseparationsolely(Meyeretal,2011).ItisdifficulttoknowhowmuchpotentialGHGreductioncanberealizedfromgravityseparatorssincesettlingbasinsmaybehavesimilarlytoanaerobiclagoons.Chemicalseparationuseschemicalcoagulants/flocculantstoincreasetheparticlesizeofsolidsandfacilitatesprecipitationand/orincreasedsedimentationrates.Duetotheexpenseofchemicalsandcomplicationsrelatedtolandapplicationafterchemicaladdition,chemicalseparationisnotcommononCAdairies.Mechanicalseparatorscanincludeawiderangeofequipmentsuchas:vibratingscreens,screwpresses,stationaryinclinedscreens,andothers(Table7.1andAppendix2.1).TheuseofmechanicalseparationsystemsinCAincreasedbetween1997and2011andincombinationwithgravityseparationwereinuseonabout15‐30%ofdairyfarmsinCA(Meyeretal,2011).Onlyscreen/presstypemechanicalseparatorswerechosenforanalysisinthisreport.

5.2. Key assumptions Asimplecostestimatemodelwasdevelopedformechanicalseparatorsondairiesranginginsizefrom300‐10,000head(milkinganddry).Tworeportsonmechanicalseparatorcapitalandoperatingcostswereused(Shepherd,2010andICF,2013)todetermineaverageexpectedcostsfromthetwosystems.Thereareotherusesfortheseparatedsolids,buttobeconsistentwiththecompostingstrategiesdiscussedinSection4,noadditionalrevenueswereassumed.Ascalingfactorof0.675wasusedtoestimatethecapitalandoperatingcostsfromeachreporttoallsizedairiesandtheaveragevaluesforbothwereused.AmoredetailedoverviewofassumptionsandmethodsformodelingthecostsofthesescenarioscanbefoundinAppendix5.

57

5.3. Costs Scalingthecostsestimatedfromthetwosourcesshowsthattheestimatedcapitalcostsofmechanicalseparatorsystemsrangedwidelyfromlessthan$100,000toaround$700,000dependingonthesizeofthedairy.Operatingcostsmeanwhilewereestimatedtorangefromlessthan$6,000peryeartoover$160,000peryearovertherangeofdairysizes.Averagingresultsfromthetwosources,theexpectedcapitalcostsrangedfrom$112,000to$550,000andoperatingcostsrangedfrom$14,300/yearto$132,000/year(Table5.1).Thisresultsintotalannualizedcostsfrom$21to$104/year/headfora10‐yearloantermand8%interestrate(Figure5‐1).

Table5.1:Averagemechanicalsolid/liquidseparationcostsandemissions

Dairy Size

Total Average Capital Cost

Total O&M Average Cost

Total Annualized Average Cost per head*

Total Annualized Average Cost per head

Adult Cows

$ $/yr $/head - 10 yr term $/head - 20 yr term

300 $112,093 $14,394 $104 $86

700 $130,127 $19,263 $55 $46

1500 $166,195 $29,002 $36 $31

3000 $233,822 $47,261 $27 $24

5000 $323,992 $71,607 $24 $21

10000 $549,417 $132,472 $21 $19

Asstatedearlier,theestimatedcostsshownhereareintendedasgeneralestimatesandshouldnotbeinterpretedasexpectedcostsforanyspecificdairy.Iftheseparatedsolidsareusedforbeddingtheannualizedcostsmaybelower,howeveritmaybelikelythatmanydairiesinCAalreadyareusingon‐sitesolidsforbedding.Forinstance,in2011,73%ofsurveyeddairiesinGlennCountyreportedusingseparatedsolidsforbedding.Thiscost

Figure5‐1:Estimatedannualizedcostsformechanicalsolidliquidseparatorsforfarmsofdifferentsize

y=1122.7x‐0.449R²=0.93953

y=845.74x‐0.432

R²=0.936$0

$20

$40

$60

$80

$100

$120

0 2000 4000 6000 8000 10000 12000TotalAnnualizedAverageCost($/

hd/yr)

DairySize(Adultcows)

10yr

20yr

58

estimatecanbesignificantlyimprovedwithmoredatafromdifferentvendorsandfarmsinCAthathavealreadyimplementedthistechnology.Additionally,evaluationofabroaderrangeofmechanicalseparatorsmaybewarranted.Unforeseendownstreamcostsformanurehandlingmayalsosignificantlyimpactthismodel.

5.4. Greenhouse gas mitigation Mechanicalsolid/liquidseparatorscanhaveawiderangeofsolidremovalefficiencies.Forthepurposesofthisreport,aconservativeestimateofanaverageof15%manure(VS)diversionfromlagoonsmaybepossible.TheseparatedsolidsareassumedtobemovedtosolidstoragewithamuchlowerMCFfactor(Table2.2).Underthisassumption,about11%ofthetotalmethaneemissionsinCAmaybemitigatedwiththisstrategy.Thisestimateislowcomparedtoothersintheliterature(SustainableConservation,2015)butduetotheuncertaintiessurroundingthedegradabilityoftheseparatedsolidsfromthesesystemsingeneralcombinedwiththefactthatmanyfarmsalreadyusesomeformofmechanicalseparation,thisestimatewasdeemedconservativeandappropriate.Theoperationofthemechanicalseparatorsisexpectedtocontributeanegligibleamountofemissionscomparedtotheemissionsoffsetfromtheseparatedsolids(lessthan3%),butdirectGHGemissionsmightvarygreatlyamongdifferenttechnologyoptionsavailable.Overall,forthelargestdairies,anannualgreenhousegasemissionreductionpotentialofabout7,000MgCO2eqisestimated.Emissionreductioncostsrangebetween$31‐$153/MgCO2eq/yr(Table5.2).Undertheseassumptions,mechanicalsolid/liquidseparationrepresentsoneofthelowercostoptionstomitigateemissionsbutwithlimitedreductionpotential(Figure1‐2).Table5.2:AverageemissionreductioncostsforSolid‐LiquidSeparationatdifferentsizeddairies

Dairy Size

Net Average Emissions Reductions

Average Emissions Reduction Cost

Average Emissions Reduction Cost

Adult Cows

Mg CO2eq/yr $/Mg CO2eq - 10 yr term $/Mg CO2eq - 20 yr term

300 203 $153 $127

700 477 $81 $68

1500 1029 $52 $45

3000 2065 $40 $34

5000 3450 $35 $30

10000 6918 $31 $27

5.5. Impact on dairy Thepurchaseandoperationofmechanicalsolid/liquidseparatorscanintroducesignificantcoststoadairywhiletheultimateenduseoftheseparatedsolidscangreatlyimpacttheemissionreductionpotentialandpotentialrevenuesintheformofcompostorbedding.Laborcostsmayalsoincreaseforthedairysincetheseparatedsolidswillneedtobemanagedand/orstoredonsite.Thereductionofsolidsenteringalagooncanreducethecleanoutfrequencyneededforsettledsolidsresultingincostsavings.

59

5.6. Environmental discussion Thewaterandairqualityconsiderationsofmechanicalsolid/liquidseparatorsarealmostentirelyassociatedwiththemanagementoftheseparatedsolids(seeSection4).

5.7. Revenues/incentives Asstatedearlier,potentialoffsetsofexpensesmayexistforthesaleofseparatedsolidsbutmarkets,especiallyforcompost,aredifficulttomodelaccuratelyatthistime.Revenuesforpotentialgreenhousegasreductionsorotherenvironmentalbenefitsfromthistypeofsystemarealsonotwelldeveloped.Areductioninsolidsaccumulationinalagoonmayresultinpotentialsavingsfromrequiringlessfrequentcleanout.

5.8. Barriers to adoption Theknownbarrierstoadoptionarethatmanydairieshavealreadyimplementedthisstrategyandsimpletooperatetechnologiesmayhaveloweffectiveness,whilemoreefficientseparatorsmayrequiresignificantcapitalandoperationalcosts.Asmentionedearlier,mechanicalsolid/liquidseparatorschangethewaythatmanureismanagedonthefarmsoincreasedcostsandtheneedforadditionalhandlingtechniquesneedtobedevelopedsimultaneously.

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6. Lagoon Aeration

6.1. Overview of technology and adoption status Aerobicmanurestoragelagoonsareusedtostabilizeorganicmaterialsusingaerobicandfacultativemicroorganisms.Underaerobicconditionsorganicmatterisdegradedintocarbondioxide,water,ammonium(ornitrate),andphosphate,withasmallaccompanyingamountofcellgrowth.Theperformanceofaerobiclagoonsdependsontheactivityofaerobicbacteriathatneedoxygentosustaintheirmetabolismandgrowth.Aerationisapotentialairemissionmitigationtechniquetocontrolvolatileorganiccompounds(VOCs)andmethanereleasedfromdairylagoons(Mitloehneretal.,2004)byinhibitinganaerobicbacteriasufficientlytoreducemethaneproduction,howeverlittleexperienceanddataforthisapplicationexistsfordairylagoonaeration.However,aerobiclagoonscanalsobeasourcefornitrousoxide(N2O)andammoniaemissions.N2Owouldnotbeproducedatlowoxidation‐reduction‐potential(ORP)of‐100‐200mV,duetothefactthatnitrificationdoesnotoccuratsuchlowvalues(Brownetal.,2000),howeverachievingstableoperationpreciselybetweenlevelswhereanaerobicmethaneproductioncancontinue(<‐300mV)andaerobicnitrificationandrapidbiomassaccumulationoccurs(>0mV)ischallenging(SeeAppendix2.1foradditionalinformation). Aerationmustbeprovidedtoavoidtheformationofanaerobicconditions.Lagoonscanbenaturallyaeratedbyairdiffusionatthelagoonsurfaceorbytheoxygenproducedfromthephotosynthesisofalgaeandcyanobacteria.Naturallyaeratedlagoonsarenecessarilyshallow,withadepthlessthan2feet,toensureadequatepenetrationofsunlighttosupportthegrowthofalgae.Lagoonsalsocanbeartificiallyaeratedusingmechanicalaerators.Severalaerationtechnologieshavebeenappliedtothetreatmentofwastewaterincludingcompressedair,mechanicalsurface,mechanicalsubsurface,combinedcompressedair/mechanical,andpumpedliquid(Cumby,1987).Surfaceaerationispromisingformanurelagoonsbecauseitneedslowerenergyrequirementsthansubsurfacesystemsandcanbeinstalledintoexistingsystemsrelativelyeasily.Somefloatingaeratorsaredesignedtodrawoxygendeficientwaterupfromthebottomandspreaditacrossthesurfaceofthelagoontocontactatmosphericoxygenandsunlight.Vendorclaimsarethatthistechnologycanhaveupto8timesmoreeffectiveoxygentransferperwattofenergyusedascomparedtodiffusebubbleblowers.Thistechnologywasinstalledonselectedswineanddairymanurelagoonsat11sitesacrossWisconsin,SouthDakotaandNebraskaandORPwasmaintainedinthedemonstrationlagoonsintherangeof±150mV,however,nodatawaspresentedonreductionofmethaneemissions(Tooley,2013).Despitethepotentialadvantagesoftheaerationinreducingmethaneemissionsfromlagoonstoragesystems,aeratorsneedmaintenanceandhavehighenergyrequirementstoprovideasufficientamountofoxygenneededformicroorganisms.AccordingtotheSanJoaquinValleyDairyManureTechnologyFeasibilityAssessmentPanelReport(Changetal,2005),highenergycostsandlackofprovenoperationalexperiencearekeyhurdlesforadaptinglarge‐scaleaerationfordairywastewatersinCalifornia.Oneofthelimitationsoftheapplicationofaerationonfarmsisthehightotalsolids(1‐3%)ofthe

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flushedmanure.Foroptimumperformanceofaeration,totalsolidsshouldgenerallybebelow1%(Cumby,1987).

6.2. Key assumptions Aslittledirectcostandperformancedataareavailableforthisapplicationondairies,estimatesofcapitalandoperationscostsformechanicalaeratorswereobtainedfromtwoUSvendorsandarangeofspeculativeGHGmitigationpotentialswereusedforestimatingpotentialcostsforGHGmitigationfromaerationofexistingmanurelagoons.Foranygivensizedairy,itisassumedthat58.2%ofthemanureexcretedfromadultcowsismanagedinthelagoon,whichwillbeaerated(Table2.2).Individualaeratorsconsideredrangedfrom3to15hpinsizeandthenumberofaeratorsneededfordifferentdairysizeswerecalculatedbasedonadailybiologicaloxygendemand(BOD)of1.3kg/animal/day(ASABE,2005)andaerationforcompleteBODreduction.ForcompletedestructionofBOD,oxygenationsupplywasassumedtobe1.5timestheBODload.Aerationefficiencywasassumedtobe1.2kgO2/kWh.ForanimalslurriesatTSof1‐5%,usingjettypeandothersubsurfaceaerators,aerationefficiencyrangedfrom0.6to3.5kgO2/kWh(Cumby,1987),dependingonmanydesignfactorsandrepresentsalargepotentialsourceoferrorinestimatingwide‐spreadimplementation.AsthenumberofaeratorsrequiredislinearlydependentontheamountofBODremoved,thereisnoeconomyofscaleassumedforinstalledcapitalcosts.Operationsandmaintenancecostsassumedincludedlabor,increasinglinearlyfrom$12,000/yearfora300cowdairy,to$70,000/yearfora10,000dairy;maintenanceas5%ofinstalledcapitalcostsperyear;andelectricityat$0.148/kWh.DirectGHGemissionsfromelectricityusewerecalculatedassuming0.277kgCO2eq/kWh(CARB,2014).Acapitalinterestrateof8%fora10‐‐yeartermswasusedtodeterminetotalannualizedsystemcosts.Twoemissionsfactorsformethanefromaeratedlagoonswereconsidered,representingarangeofhighandloweffectiveness.TheMCFfortheloweffectivenessscenariowas0.3,whichrepresentsavalueforpoorlymanaged,overloadedaerobicindustrialwastewatertreatmentplantsystems(IPCC,2006),andtheMCFforthehigheffectivenessscenariowaszero,representingawellaeratedsystem.TheemissionsfactorforN2Ofromaeratedlagoonswasassumedtobe0.01gN20/gNnitrogen,areferencevalueforaerobicmanuretreatmentsystems;howeveranuncertaintyrangeofatleastafactoroftwoisstated,whichmaypossiblebehighergiventhelackofrelevantdataforthisapplication(IPCC,2006).

6.3. Costs AdetailedsummaryofestimatedcostsforaerationofdairylagoonsareshowninAppendix6.1(loweffectiveness)andAppendix6.2(higheffectiveness).Asummaryoftotalcostsareshownbelow(Table6.1).

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Table6.1:Aerationscenarioestimatedsystemcosts

Dairy Size Total Average Capital

Cost Total O&M Average

Cost Total Annualized Average

Cost per head

Adult Cows $ $/yr $/head/yr (10 yr term)

300 $57,754 $45,011 $179

750 $144,386 $111,378 $177

1,500 $288,771 $218,929 $175

3,000 $577,543 $422,549 $170

5,000 $962,571 $670,228 $163

10,000 $1,925,143 $1,170,353 $146

Electricitycostsrepresent65‐85%oftheO&Mcostsestimatedforsmalltolargedairies,respectively.Fordairiesconstrainedbyexistingelectricalcapacity,theadditionalelectricalloadrequiredmayberelativelylargeandpotentiallyincurtheneedforcostlyinfrastructureupgradeswhichhavenotbeenconsideredhere.

6.4. Greenhouse gas mitigation Unlikemanyoftheotherscenariosevaluatedinthisreport,capitalandoperationscostsscalealmostlinearlywithdairysizeandthereforeGHGreductionscostsarefairlyflatacrosstherangeofdairysizesevaluated(Table6.2).Table6.2:AerationGHGmitigationpotentialsforlowandhigheffectivenessscenarios

Dairy Size Net GHG Mitigation (High Effectiveness)

Average Emissions

Reduction Cost

Net GHG Mitigation (Low Effectiveness)

Average Emissions

Reduction Cost

Adult Cows Mg CO2eq /yr $/Mg CO2eq Mg CO2eq /yr $/Mg CO2eq

300 1,273 $42 686 $78

750 3,183 $42 1,716 $77

1,500 6,367 $41 3,432 $76

3,000 12,733 $40 6,863 $74

5,000 21,222 $38 11,439 $71

10,000 42,443 $34 22,877 $64

Becauseelectricityuseisasignificantinput,netGHGmitigationpotentialisreducedby4‐8%fromwhatitwouldbeotherwise.

6.5. Impact on dairy Inadditiontosignificantadditionalcostandmaintenanceburden,theadditionofanaerationsystemtolagoonswouldlikelyhaveminimalimpactonexistingflushdairymanuremanagementoperationsthatprimarilyutilizeliquidmanuresfornutrientrecoveryoncrops.Asstatedpreviously,somedairiesmayrequiresignificantupgradestoelectricalinfrastructuretobeabletosupportlarge‐scaleaeration.Odor,hydrogensulfide,VOCsandammoniaemissionsshouldtheoreticallybereducedwithefficientaeration,however,have

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thepotentialtobeexacerbatedshouldinefficientaerationoroverloadingoccur.Similarly,settledsludgelevelscandecreaseafteraeratingexistinglagoons,howeveranincreasecanalsooccurshouldaerationconditionsnotbeoptimumastheaerobictreatmentofmanurecanyieldalargeamountofactiveaerobicmicroorganismsthatcouldbuildupinthelagoon,reducingtheavailablestoragevolumeandrequiringadditionallagooncleaningfrequencywhichmaybemademoredifficultbythenewlyinstalledaerationequipment.Somereportsindicateaerationsystemsinanimalmanurelagoonsaretypicallyinitiallyunder‐designedorlessefficientthancalculated,leadingtopoorperformanceandlimitedoperation(Cumby,1987,Rumburgetal.,2004),highlightingtheneedforadditionaldesignandoperationsdataspecifictouseinCaliforniadairylagoons.

6.6. Environmental discussion AerationforGHGreductionwillrequireacarefulbalancebetweencreatinganoxidizingenvironmenttoreducemethaneemissions,butnotenoughofonewheresignificantnitrificationmayoccur.SignificantincreasesinN2Oemissionswithaglobalwarmingpotential300timesthatofCO2ona100‐yeartimescalecandrasticallyreduceanygainsachievedfrommethanemitigation.NitrogenemissionsfromammoniavolatilizationorotherNOxcompoundsmayalsobesignificantandcompoundlocalairqualityconditions.Additionally,thevolatilizationofthesenitrogenouscompoundsreducesthenutrientscontentinlagooneffluentsanditsassociatedfertilizervalue.Ifsignificantsludgeaccumulationoccurs,itcanrepresentalargesourceofVSthatneedstobecarefullymanagedsoasnottoallowanaerobicdecompositioninsubsequentmanagementprocesses(CARB,2014).Aswithairemissions,waterqualityimpactswithaerationhavethepotentialtobeeitherpositiveandnegativeanddependentonseveraldynamicfactors.TheprimarybenefitfromaerationisthereductioninwastewaterBODandstabilizationforsubsequentdistributionoruse,althoughitrequireshighenergyinputtoachieve.Nitrification,whilenotaproblemforplantuse,increasesthepotentialforleachingorrunoffatasignificantrisktowaterqualityandsafety.Additionalcommentaryontheintricaciesofnitrogencyclinginmanuremanagementsystemsisdiscussedinasubsequentsection.Phosphorussettlesinlagoonsandcanbepreservedformanyyears(Lorimoretal.,2006).Whilesometreatmentandstabilizationoccurs,effluentfromaerobiclagoonsinmostofthecasesisstillnotsuitablefordischargeintosurfacewaterbecauseitwillnotmeetstandardsforBOD,phosphate,andnitrogeninmoststates,however,theeffluentcanbesuitableforlandapplicationbyfurroworsprinklerirrigation(HermansonandKoon,1973).

6.7. Revenues and incentives Aerationofanaerobiclagoonscouldfacilitatecontinued“business‐as‐usual”fordairyflushandliquidmanuremanagementsystems,withlittleassumedimpactonexistingfinancialmodels.Mechanicalaeratorscouldbeappliedintheexistinglagoonswithoutestablishingsignificantnewmanuremanagementinfrastructure.BOD,nitrogen,andodorreductionfromlagoonscouldbeattractiveco‐benefitsfordairieswheresignificantlocalconstraints

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onsuchparametersexist.Forexample,thereductionofnitrogenisabenefitforfarmswithinsufficientcroplandtoutilizeallofthenitrogenavailableinthatfarm.Theremovalofnitrogenisagoodopportunityfordairyfarmstomaintainstocklevelswithoutexceedingnitrogenuptakecapacityoftheavailablecropland(SanJoaquinValleyDairyManureTechnologyFeasibilityAssessmentPanel,2005).

6.8. Barriers to adoption Asidefromprojectedhighcapitalandoperationscosts,amajorcurrentbarriertoadoptionisthatthereisinsufficientscientific(peer‐reviewed)andoperationaldataavailabletosupporttheclaimthataeratorscanbeappliedeffectivelyinCaliforniadairylagoonstoachieveappreciableimprovementsinairquality.Despitepotentialadvantagesofaerationinreducingmethaneemissionsfromlagoonstoragesystems,aeratorsneedmaintenanceandhavehighenergyrequirementstoprovideasufficientamountofoxygenneededformicroorganismgrowthandactivity.AccordingtotheSanJoaquinValleyDairyManureTechnologyFeasibilityAssessmentPanel(2005),highenergycostsareamajorhurdleforadaptingthelarge‐scaleaerationofdairywastewaterinCalifornia.Useofaerationaftersolid‐liquidseparationorafteranaerobicdigestioncouldreducethemaintenancecostsandincreasetheaeratorslifetimeandmaybemoreattractivethanaerationofflusheddiarymanure.Thereisaneedformoreresearchtoevaluatetheperformanceandthecostsofaeratorsappliedtotheliquidfractionsofflushed,separatedliquid,andpost‐digestionmanures.

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7. Manure Management, Water Quality, GHG Emissions and Other Environmental Effects

7.1 Overview of manure management issues Ingeneral,dairyfarminginmodernagriculturalsystemshasbecomemuchmoreresourceuseefficient(RUE)thaninthepast(Capperetal.,2009).GainsinRUEhavepositiveeffectsbyreducingGHGemissionsperunitofmilkorotherlivestockproducts.CaremustbetakentopreservegainsinRUEinlivestockproductionsystemsandtheirtrajectorytowardsevergreaterRUE,whilegraduallyreducinganyadverseenvironmentaleffects.TheaccumulationofsurplusnutrientsinconfinedanimalfeedingoperationslikedairyfarmsinCAischaracteristicofmodern,intensiveanimalagriculture.Therearemanybenefitsthatderivefromsuchsystems,butalsosomecosts.Benefitsincludelowcostsforlivestock‐basedfoods,improvedresourceuseefficiencyforbothdairyproducersandforthestate’sagriculturalsystemsasawholeduetoproductiveuseofresidualby‐productsfromcropproductionandfoodprocessingindairyrations,andgeneralcontributionstotheeconomyofruralregionsandthestateingeneral.Problemsassociatedwithmodern,intensiveConfinedAnimalFeedingOperations(CAFOs)includenuisancefactorsassociatedwithlargepopulationsofanimalsandemissionsfrommanurestoair(NH3,CH4,N2O)andgroundwater(NO3)(Harteret.al,2012;Changetal.,2005).ToaddressnutrientsurplusesassociatedwithdairyoperationsintheSanJoaquinValleyandelsewhere,economicwaysmustbefoundtoconcentratenutrientsinmanureandremovethemfromthoselivestockfarmswherenutrientsinexcessofcropneedsarepresent.Thesenutrientsandmanureorganicmattercanbeusedbeneficiallyonotherfarmswithoutlivestockaspartialsubstitutesforconventionalfertilizers,orfordiverseagronomicandhorticulturaluses(Coppegeetal.,2012;InformaEconomics,2012).Currently,varyingbutsignificantamountsofmanuresareusedfornon‐dairycropsoroff‐farm,inpartinresponsetotheadoptionofthestate’sgeneraldairymanagementorderin2007(CRWQCB,2013;Viersetal.,2012).Themanagementofnutrientsindairymanuresisacomplextask,especiallyforN,whichissubjecttodiversetransformation,uptakeandlossprocesses(Figure7‐1andFigure7‐2).Thereisalong,extensivehistoryofresearchonbestmanagementpracticesformanures(SalterandShollenberger,1939;Prattetal.,1979;;Changetal.,2005),butrelativelylessworkhastakenplaceinCalifornia,despiteitsstatusasthestatewiththenation’slargestdairysector(Czruellaetal.,2012;Changetal.,2005).ImportantdifferencesbetweenCaliforniaandtemperateenvironmentsincludeayear‐roundgrowingseasonwiththeuseofdoubleortriplecroppingsystems,longerperiodsoftimewithtemperaturessuitableforNtransformingmicroorganisms,andarelianceonirrigation.TheseaffectthecomplexNtransformationpathwaysthatoccurandtheopportunitiesformanureapplication.ThereviewofdairymanuremanagementproducedbytheUniversityofCaliforniain2005(Changetal.,2005)stillrepresentsthebestreviewoftheparticularissuesassociatedwith

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manuremanagementinCalifornia.MorerecentevaluationbyHarteretal,(2012)andinrelatedpublications(Viersetal.,2012;Dzruellaetal,2012)reinforceandmakemoreexplicitforthesouthernSanJoaquinValleyregion,thechallengesassociatedwithmanuremanagement.Nutrientscanbeappliedtogrowingcropsinwaysthataresynchronouswithratesofcropuptakeusingwatersolublefertilizersandappropriateirrigationmanagement,butthisismuchmoredifficulttoachievewhenmanureisusedasafertilizer.Summarizingsomeofthesefindings:basedoncalculations,modeling,andalimitedamountofappliedresearch,between34%and68%oftheNinmanureappliedtocropsisrecoveredbycrops,buttheremainderislosttotheatmosphereandtogroundwater.Thisisalargerangeandalsoindicatesthatpotentiallossesarelargeandthatpotentialimprovementinnutrientmanagementandcorrelatedenvironmentalemissionsfrombothmanurestorageandinapplicationtocropsispossible.EmissionsincludeGHGslikeCH4(Houetal.,2015;Thomaetal.,2012).

Figure7‐1:MajorComponentsoftheNitrogenCycleinaForageCropFertilizedwithDairyManure(FromChangetal.,2005,Figure5.1)

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Figure7‐2:Nmineralizationandcropuptake.Source:NitrogenInAgriculturalSystems:ImplicationsForConservationPolicy/ERR‐127EconomicResearchService/USDA;MarcRibaudo,[email protected];JorgeDelgado,LeRoyHansen,MichaelLivingston,RobertoMosheim,JamesWilliamsonPracticalconstraintslimitingmorecompleterecoveryofmanurenutrientsbycropsincludetheorganiccharacterofmuchmanureNinitsrawform,difficultiesinhandlingandapplyingmanureinatimelymannerfromtheperspectiveofcropuptake,sometimesweakcorrelationbetweenmanurenutrientavailabilityandpatternsofcropuptake,thelargeamountsofmanureavailableonsomedairyfarms,anddifficultiesinapplyingmanurenutrientsuniformlyacrossafield(Changetal.,2005,USDA‐ERS;Dzruellaetal.,201217).If

17“WhileimprovementsinNuseefficiencyarepossible,apracticalupperlimitissetbyunpredictablerainfall,difficultyinpredictingtherateofmineralizationoforganicN,andmostespecially,soilspatialvariabilityandtheneedtoleachsaltfromthecroprootzone.Itisestimatedthatbyimplementingrecommendedpractices,cropNrecoverycanreach60‐80%ofNinputs.Whileimprovedmanagementwill

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manureisappliedwithirrigationwater,irrigationuniformityislimiting(Pangetal.,1997;LeteyandVaughn,2013)18,andifappliedassolidmaterials,uniformdistributioncanbedifficult(Changetal.,2005).EstimatesofmeasuredormodeledlossesofNO3‐Nfromdairysystemsvarywidely(USDA‐ERS,2012;Changetal.,20015,Dzruellaetal.,2012).Whennutrientsareprimarilyorganicinform,mineralizationprocessesareneededtoallowcropnutrientuptake(Figure7‐2).Theseprocessesarenotwell‐coordinatedwithcropneeds,especiallyformaize,whichhasshort,criticalperiodsofNrecoveryandothertimeswhennutrientsarelesscritical(Figure7‐3).Altogether,atypicaldoublecroppedfield19intheSanJoaquinValleywasestimatedtobeabletoabsorb400to600lboftotalNperacreperyear,recoveringbetween60%to70%ofavailableNfromallsources.Amountsappliedcorrespondingtotheselevelsofuptakewereestimatedtobebetween660and990lboftotalNperacre.Bothendsofthisestimatedrateofrecoveryarehigherthanmanyotheragronomicstudiessupport(USDA‐ERS,2012)andestimatedbyMedillien‐Azuaraetal(2012;[inDzruellaetal.,2012])whoused50%asabaselineintheirmodelingofnutrientuseefficiency.UnrecoveredNwasassumedemittedtotheatmosphereorgroundwaterorretainedinsoilsforcropuptakeinfollowingseasons.20TohavesufficientamountsofavailableNpresentforcornatstrategictimesfromorganicsourcesrequireslargeamountsoforganicNwhichcontinuetomineralizeevenwhencropdemandisreduced.Matchingcropneedswithmineralizationprocessesclearlyisimperfect,andsomefarmerssupplementmanureapplicationwithwater‐runfertilizer,evenifpotentialnutrientavailabilityonatotalnutrientappliedbasisissufficient.Toimprovethemanagementofmanureandfertilizernutrientsondairyfarms,TheUCCommitteeofExperts(Changetal.,2005)recommendedthedevelopmentofbestmanagementpracticesthatimprovecalculationoftheamountofNandothernutrientsneededbycrops.ThesepracticeshadtoincludeafullaccountingofallsourcesofNavailabletothecrop,includingresidualmineralandorganicNappliedtopreviouscrops,Npresentinirrigationwater(especiallyifgroundwaterwithnitratesisused),atmosphericdeposition,andin‐seasonmanureandfertilizerapplications.

leadtoareductioninthemassofnitratelostbyleaching,itisunlikelythattheconcentrationofnitratecanbereducedtotheMCL,especiallywherethesoleormainsourceofaquiferrechargeispercolatefromirrigatedcropfields.”Page15018ManydairiesinCAhaveintegratedtheirirrigationandmanurehandlingsystemstomanageatleastaportionoftheirmanure,especiallythosewithflushmanagementsystems(ibid).Convertingtodripirrigationmightincreaseirrigationuniformity,reducesurfaceevaporation,andpreventtailwaterrunoff,butitisunclearifmanurewastewaterscanbeusedefficientlyovertimeinsuchsystems,orifthecostsofmodifyingmanuremanagementsystemsneededtousedripirrigationwillbeeconomic.AlsouncleararetheGHGconsequencesofchangestomanurehandlingandapplicationassociatedwithdripirrigation.19Cornforsilageinspring/summerandfall/winterannualcerealmixturesforsilage‐assumingaverageyields.20“…nitrate‐nitrogenleachinglosses–underoptimalirrigationandnutrientmanagement–willbeintherangeof55to150lbsNac‐1yr‐1.Assumingrechargeratesinirrigatedsystemsof1–2acre‐feetperacreperyear(300–600mmperyear),thenitrateconcentrationintheleachateisintherangeof10to55ppm(mgL‐1NO3‐N,whichisatorabovetheregulatorylimitfordrinkingwaterquality(10mgL‐1)…Changetal.,2005.page9.

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Figure7‐3:NutrientuptakepotentialvarieswithtimeofyearandcropFromChangetal.,2005.Asecondmethodofimprovingnutrientuseefficiencyandreducingemissionswastobettertimenutrientapplicationtocropuptake.Asnoted,thisisdifficultfororganicallyboundformsofN,whicharesubjecttovariablemineralizationprocesses.Itisespeciallydifficultformanureswithlargeamountsofsolidmaterials,whichareonlyslowlymineralized,withnutrientsbecomingavailableovertime.Lastly,themeansofapplyingmanurebasednutrientsaffecthowmuchisrecoveredbycropsandthefateofexcessnutrients,includingrelativelossestoairorgroundwater.AnymethodofmanuremanagementadoptedondairyfarmstoreducemethaneemissionsfrommanurestoragethatalterstheformofNinmanures,orthetotalamountavailableonthefarm,willinfluencethebestmanuremanagementpracticesneededonindividualfarms,perhapsindifferentways.AdditionalpotentialcomplicationsarisewithrepeatedapplicationsofmanuresorADdigestatesovertimeasorganicmatterandorganicNaccumulateandcontinuetoprovidenutrientstocrops,orintheabsenceofcropuptake,forlossoff‐farm.Eachofthemanuremanagementandtreatmentpathwaysanalyzedherewillaffectthemanagementandfateofmanurenutrients.AnactivenutrientrecoveryprocessisneededfromADeffluent,leavingresidualwateronthefarm.Theseprocessescurrentlyareexpensiverelativetothevalueofthenutrientsrecovered.Policiesshouldsupportmoreefficientuseofmanurenutrients,bothon‐andoff‐farm.

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7.2 The effects of AD systems on dairy manure TheuseofADsystemsformanuretreatmentondairyfarmswillhelpcapturefugitiveCH4emissionsandallowitsuseforpowerproductionorfortransportationfuels.Duringanaerobicdigestionthecharacteristicsofmanurearechanged.MostoftheorganicallyboundNinraworfreshmanureistransformedtoNH4+‐N,intheliquidADdigestatematerial,andPsolubilityisreduced21.Buttotalamountsofnutrientsareunaffectedandmuststillbemanagedsubsequentlytominimizeemissionstoairandgroundwater.Inadditiontoreducingfugitivemethane(CH4),ADreducesthenitrousoxide(N2O)andothertracegasemissionsfromdairyfarms(shortlivedclimatepollutants,SLCP),whileusingthebiogasforenergy(i.e.,heat,powerorfuels).AMethaneCaptureandAbatementStandardisbeingdevelopedbytheAirResourcesBoardandtheCaliforniaDepartmentofFoodandAgriculturehasatooltohelpidentifytargetsforagriculturalmethanesourcestoachieve..ButevenifmethaneemissionsarereducedthroughuseofADandpolicy,thenutrientsandsaltspresentinrawmanureremaininADdigestates.Currently,thesenutrientsmaynotbeusedoptimallyonfarmsifmoremanurenutrientsareappliedthancanberecoveredbycrops.Whilethemanuremanagementliteratureisextensive,ADresidualsarediverseanddifferfrommanures.Thesedifferencesrequirecharacterizationandevaluationsothatlandapplicationcanbeimproved(Nkoa,2014).SinceADresidualsarebiologicallyactiveandmayincludediversecontaminants,potentialfoodsafetyeffectsfromtheiruseneedtobeassessedifusedoff‐farmoncropsdirectlyconsumedbypeople.GivenCalifornia’sexceptionalagro‐ecologicaldiversity,arangeofusesarepossibleforapotentiallylargenumberofnewfertilizerandsoilamendmentmaterialsderivedfromnewADsystems,includingthestate’sgrowingdemandfororganicfertilizersforfarmsandgardens,andtoreplaceconventionalfertilizersonnon‐livestockfarms.NutrientsinpostADtreatmentmanuresstillfollowthatsamesetofpathwaysendingwithcropuptakeorlosstotheenvironment.TheUCcommitteeofexperts22summarizestheseas:

Ammoniavolatilizationfromthesoilsurface.Oncemanureisapplied,ifsoilpHisneutraltoalkalineandisnotincorporatedorcovered,NH3inmanuretendstovolatilizetotheair.Theamountvarieswiththespecificconditionsofthe

21“Digestateshavehigherammonium(NH4+):totalnitrogen(N)ratios,decreasedOMcontents,decreasedtotalandorganiccarbon(C)contents,reducedbiologicaloxygen(BOD)demands…,elevatedpHvalues,smallercarbontonitrogenratios(C:Nratios),andreducedviscositiesthanundigestedanimalManures….ThedigestateNH4+‐NcontentisdirectlyrelatedtotheoriginalfeedstocktotalNcontent….Digestatesfromfeedstockswithahighdegradability…withadiethighinconcentrates…arecharacterizedbyhighNH4+‐N:totalNratiosandnarrowC:Nratios….CattlemanuresorfibrousfeedstockslowinN(e.g.silagemaize)leadtoalowNH4+N:totalNratio…Analysesofparticlesizedistributionsinrawanddigestedslurriesshowedageneralshiftindistributiontowardlargersizes.Largerparticles(i.e.>10μm)aremoreresistanttodegradation”.MoellerandMueller,2012.page242‐3.Totalamountsofnutrientsandsaltsdonotdiffer(El‐MashadandZhang,2007)22Changetal.,2005.page40

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application.AnaerobicstorageofmanureincreasestheamountofmanureNfoundasNH4+‐N,soriskoflossfromthispathwaymaybeincreasedrelativetocurrentmanagementconditions.

Ammoniaandothernitrogengasesvolatilizingfromplantsurfaces.PlantsemitsomeNH3asaresultofphysiologicalprocesses,andmanureappliedtogrowingcropswhichmaycoatleaves,mayvolatilizefromthoseleafsurfaces.

DenitrificationlossesofnitrateandnitriteasN2,N2O,andNOgasses.ManureappliedascoarsesolidscontainsalargeamountoforganicallyboundN.ThisNdenitrifies,formingnitriteandthennitrate.Undersuitableconditions,nitratemayoxidizetogaseousforms,includingN2O,aGHGgas.Theamountoccurringdependsonthespecificconditionsatthetimeofapplicationandsubsequentlyandmanureorg‐Nmineralizesandcropremovaloccurs.Theseprocessesaredifficulttotimeandregulateefficiently.

Leachingofnitrateandnitritebeyondtherootzone.SurplusnutrientsfromfertilizerormanuremayformNO3,asolubleionsubjecttoleaching.SomeNH3mayalsoleach,buttheriskislower.

Surfacerunoffinsolutionorinsediment.Surfaceirrigatedmanuresmayresultinsometail‐waterrunoff.Surfaceappliedsolidmanuresmayrunoffinirrigationeventsorduringwinterifwaterrunofforsoilerosionoccurs.ThesearenotconsideredtobeimportantpathwaysondairiesinCaliforniasincefieldsmostcommonlyareinusewithcrops,whichreduceserosionlossestoverylowamountsandfarmersalreadymustminimizetailwaterlossesfromfieldsundercurrentregulatoryconditions.

7.3 Processing of Manure and AD Digestate Manureanddigestateshouldbemanagedbasedonfarmcropnutrientbudgets.Ifsurplusnutrientsarepresentonthefarminexcessofamountsneededbycropsorallowedundernutrientmanagementplans,off‐farmusesmustbedeveloped.Thiscanincludethedevelopmentofby‐productsorvalueaddedfertilizerproductsandorganicsoilamendments,foruseandsaleoffthefarm(Coppegeetal.,2012;InformaEconomics,2012).AnumberofrawmanureandADdigestatetreatmentprocessesarepossible;leadingtodiversefertilizerproductsormaterials.Mostprocessesstartbyseparatingcoarsesolidsfromliquids.Particlesizedistributionofmanure,applicationsofseparatedfractions,andthedistributionofvariouschemicalconstituentsindifferentsizesareimportantparametersfordesigningandselectionofliquid‐solidseparationequipment(ZhangandWesterman,1997).SeveralprocessesforseparatingandconcentratingthenutrientsofrawandanaerobicallydigestedmanureareshowninFigure7‐4.

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Figure7‐4:PotentialManureProcessingOptions

Variousmanuretreatmenttechnologiescouldbeusedtoalterthenutrientprofilesandnutrientratiosinmanure,makingnutrienttransportationoverlongerdistancesandutilizationasfertilizersubstitutespotentiallymoreefficient.Forexample,mostorganicnitrogenandphosphorusinmanureiscontainedinthesolids.Separatingsolidsfromrawordigestedmanurewillcreatetwofractions,solidsrichinorganicnitrogenandphosphorus,andliquidsrichinammonia,solublephosphorusandpotassium.Theymaybefurtherprocessedorusedtomatchaparticularcrop’sneeds.Thesolidfractioncouldbeseparatedintocoarseandfinefractionsbasedonparticlesizes.Coarsesolidsmainlyconsistoffibersandaregoodmaterialsforanimalbeddingorforsoilorganicmatterimprovement.Theymaybeusedtomakeotherbiomaterialsorproductslikecompostandbiomasspellets.Finesolidshavehighernutrientcontentsandmaybeusedasorganicfertilizerproducts.Producingmanurebasedfertilizerswithspecificcharacteristicsfromeachfractioncouldreducethecostoftheirtransportationcomparedwithwholemanureordigestate.TheliquidfractioniseasilymovedusingpumpsandpipestransportationsystemsandcanbeappliedtolandusingsimpleirrigationequipmentandsystemscommonlyusedonCaliforniadairiesforsurfaceapplicationwithouttheriskofclogging.Moreoverwater

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meteringwillbemoreaccurateandusefulforcalculatingtheamountofnutrientsapplied(HuijsmansandLindley,1984).

7.3.1 Solid/Liquid Separation Solid‐liquidseparationisnormallythefirststepinmanuretreatment.Sedimentation,screening,filtering,pressesandcentrifugationarecommonseparationmethods.Particlesizedistributionofmanuresolids,usesofseparatedfractions,andthedistributionofvariouschemicalconstituentsindifferentparticlesizesareimportantparametersfordesigningandselectingsolid‐liquidseparationequipment.Sedimentationandscreeningarethemostcommonlyusedtechniquesforanimalmanuretreatment.Althoughsedimentationisasimpleandcheapmethodforremovingsolidsfrommanure,itneedslongperiodsoftimeandlargestructuresforsettling,suchasbasinsortanks.Screenseparatorsincludestationaryscreen,vibratingscreen,androtatingscreenseparators.ThedescriptionofeachseparatorandprocessparametersareprovidedbyZhangandWesterman(1997).Centrifugationcanbeveryeffectiveforthesolidsseparationbutthehighcapitalcostandenergyrequirementhavehinderedtheusesofcentrifugesonfarms.Screwpressesarecommonlyusedforseparatinganddewateringsolidsbuttheirseparationefficiencyislimited.Capitalcostsofequipmentandtheirlimitedlifespanandmaintenancerequirements,processcontrolsystemsandpowerneedsarefactorsaffectingtheadoptionofefficientsolid/liquidseparationonfarms.Thecostsforsolid/liquidseparationshouldbebalancedagainstthereductionintransportationcostsforoff‐farmuseandthevalueofthefertilizerby‐products.

Manureanditsdigestatescontaincolloidalparticlesthatdonotnaturallyaggregatebecausetheyarenegativelychargedandrepeleachother.Theadditionofmultivalentcationsand/orpolymerscausescoagulationandhenceflocculation.Coagulationisaprocessthatdestabilizesthepotentialenergyofrepulsionbetweensuspendedsolidparticlesindilutedwastewatersothatparticlescanbeflocculated.Toassistinsolidseparation,coagulationand/orflocculationchemicalscouldbeaddedtorawmanuresandpriortomechanicalseparators.Severalmultivalentcationshavebeensuccessfullyappliedtocoagulateorganicmatterandprecipitatephosphorusinanimalslurry(Hjorthetal.,2010)23.AcomparisonofchemicaltreatmentwithothertechnologiesisshowninTable7.1.

23Theselectionofchemicaltypeanddosedependsontotalmanuresolids,pH,particlesize,andtemperature.Moreover,theselectionofthecoagulantdependsonitsenvironmentalandhealthimpacts,toxicityoftheproduct(s)ofthedegradationoforganicpolymers,andtheintendeduseoftheresultingseparationproducts.Selectedchemicalsshouldbe‘generallyrecognizedassafe’asdesignatedbytheFoodandDrugAdministration(FDA).Comparedwithorganicpolymers,largeamountsofinorganicchemicalssuchasalum,ferricchloride,orlimeareusuallyneededtoachievedsimilarsolidremovalefficiencies.Thiscouldresultinincreasedamountsofchemicalrichsolidsthatrequirecarefulmanagementanddisposal.Syntheticcationicandanionicpolymersandchitosanwereeffectiveforcoagulationofdairymanurebutnotfordigestereffluent(Sieversetal.,1994).However,cationicpolymersaresuperiortoanionicandneutralpolymers.Naturalflocculants,suchaschitosan,areimportantfortheseparationofmanurenutrientsfororganicfarmingthathasanincreasinginterest.Thehighcostofnaturalchitosanrequiresthedevelopmentofcheapnaturalflocculants.Phosphorusseparationcouldbeenhancedbycrystallization of struvite.

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Table7.1:Comparisonoftechnologiesformanuresolidsprocessing(adaptedfromZarebskaetal.,2014)Technology System Complexity Pros Cons Operation on

farm Operational costs

Uncertainty

Sedimentation Settling basins and Thickener

Periodical change of thickener

60% removal of TS for slurry with 10-20 g/l

5% removal of TS for slurry with 60 g/L; long time

Simple Low Initial TS affect the removal efficiency

Screening Stationary vibrating, and rotating screens

Periodical change of screens

Simple and low energy needs

Low efficiency 8%-16%

Simple Low Ratio between the flow rate of slurry and the screens surface area

Centrifugation Decanter centrifuge Initial tests are needed to adjust process parameters

High separation efficiency

High energy consumption for high gravity centrifuge

Moderate High Robustness of decanter for mechanical damage

Pressurized filtration

Screw press Cleaning of screw and perforated cylinder

High dry matter of solid fraction

Low efficiency of fine solids removals

Moderate Low/medium Screen blinding

Drainage Belt separator Needs determination of the filtration resistance in lab scale for designing full-scale

Need to remove filter cake from belt

Particles between 1-100 μm hinder filtration

Simple/moderate Low/medium Clogging filter media

Chemical Flocculation/ Coagulation

Testing flocculent efficiency

Enhancement of separation efficiency

Chemical remains in the separated solids

Simple/moderate Medium/high Dosage and type of flocculants

Microfiltration Pretreatments steel filter membrane, cellulose ester pump

Air backwashing and chemical cleaning

Suspended solids are removed

Inorganic and biofouling

Moderate Medium Membrane

Ultrafiltration Pretreatment centrifugation, screening, screw press

Washing with water

Suspended solids are removed

Double ultrafiltration

Moderate Medium Membrane lifetime

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7.3.2 Nutrient Concentration in Manures and AD Digestates ThelowconcentrationofnutrientsinmanureandADdigestatesrequiresacombinationofcreativeresearchandpolicyconstructiontobettermanagemanureasaresourceandpotentialenvironmentalpollutant.Policymustaccountfornetbenefits.ReducingNandPlossesfromCAFOs,(andreducingNlossesfromagricultureingeneral)willinvolvecosts,eitherdirectlyforinterventions,orindirectlythroughhigherfoodprices,orlossoffarmbusinesses.Integratingnutrientmanagementwithenergyproductionandgreenhousegasreductionofferspromisingopportunitiestoaddressseveralenvironmentalandeconomicproblemsinanintegratedmanner.Thismaybeonewaytominimizepubliccostsgenerallyfortheenvironmentalimprovementsdesired.Developmentofbio‐fertilizerproductsfromanaerobicallydigestedmanureisimportanttoimprovetheeconomicsoftheanaerobicdigesters.Producingcoproductsfromtheanaerobicallydigestedmanurecouldaddabout10%tothecapitalcostoftheADsystem(Gorrie,2014).Someofthecostsofnutrientconcentrationfromdigestereffluentmaybeoffsetfromon‐farmenergyproductionusinganaerobicdigestionsystems,orfromsalesorinternaluseofcompressednaturalgas(CNG)fuelsmadefrombiogas,withthedigesterresidualsthenbeingtreatedfornutrientrecovery.Otherportionsofthetotalcostmaybereducedthroughacombinationoffertilizersales,carboncreditsanddirectpublicsubsidies.Developingnewproductsfromdigestedandrawmanurecouldcreatenewjobsforthestateandreducethefossilfuelsconsumptionandtheemissionsintheproductionofsyntheticfertilizers.Theuseofmembranesmaybenecessaryforconcentrationofnutrientsandsaltremoval.Removingmostofthesolidsfrommanureordigestateisnecessarypriortousingmembraneseparation.Membranefoulingisoneoftheoperationalchallengesofapplyingmembraneseparationforwastewatertreatment.Foulingdependsonfeedstockproperties(pH,ionicstrength,concentration,andtemperature),membranecharacteristics(poregeometry,surfacecharge,surfaceroughness,andhydrophobicity),thefoulants’nature,andhydrodynamicconditions(LiandElimelech,2004).Membraneseparationequipmentthathasself‐cleaningmechanismsorusedurablemembranesisdesirable.Zarebskaetal.(2014)providedagoodreviewofmembraneseparationtechnologiesandtheirapplicationsonwastewatertreatment.Ifammoniaremovalfromliquidmanureisdesired,severalphysicochemicalprocessessuchaselectro‐dialysis,membranedistillation,airstripping,chemicalprecipitation,andionexchangecouldbeconsidered.Zarebskaetal.(2014)estimatedenergyandcapitalandoperationalcostsforseveralmethodsforammoniarecoveryfrommanureasshowninTable7.2.

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Table7.2:Energyconsumptionandtotalcostsforammoniarecovery(Zarebskaetal.,2014)

Technology Energy

consumption [kWh/m3 feed]

Energy cost [US$/m3 feed]

Chemical cost [US$/m3 feed]

Operating cost (Energy cost + chemical cost) [US$/m3 feed]

Ultrafiltration/Nanofiltration 4.5-11 0.3-0.8 0.7a 1.0-1.5 Ultrafiltration/Reverse

osmosis 6.6-14.4 0.5-1.0 0.7a 1.2-1.6

Membrane distillation 0.2 0.02 1.1b-3.5c 1.12-3.52 Ultrafiltration/ Membrane

distillation 2.5-9.1 0.2-0.6 1.1b-3.5c 1.3-4.1

Air stripping 4.1 0.3 1.1b-3.5c 1.4-3.8

Chemical precipitation 0.8 0.1 12.9 13.0

Ultrafiltration/ ion exchange 2.3-8.9 0.2-0.6 8.7 9.3

a cost for acid to decrease pH below 4.5 b costs for lime to increase pH above 10.5 c cost for NaOH to increase pH above 10.5 Comparedwithmembraneprocesses,physicochemicalprocessesaresimplerandlessenergyintensive.Ionexchangecanbeusedtoremoveammoniafromtheliquidfractionofmanure.Henriksenetal.(1998)usedclaymineralbentonitetopurifyandmodifythenitrogencontentoftheliquidfractionofswinemanure.Usinglargequantitiesofbentonite,10%‐12%oftheliquidmass,about62%ofnitrogencontainedinmanurewasremovedviaionexchange.Waterandvolatilecompoundssuchasammoniaandfreefattyacidscouldbeseparatedfromtheliquidfractionbyevaporation.However,evaporationisanenergyintensiveprocess.Useofexpensive,multi‐stepevaporatorscouldsubstantiallyreducetheenergyconsumption.Calcium,magnesium,carbonate,andphosphate,canberemovedbyprecipitation.AnexampleofADdigestatetreatmentsandpossiblebyproductstrategiesfromcurrentresearchatUCDavisisdescribedhere.OtherworkisoccurringintheUSbuttherearefewcommercialprojectsyetestablished(Coppegeetal.,2013;Gorrie,2014).Dr.RuihongZhangandherresearchteamatUCDavishavedevelopedintegratedbiologicaltreatment,filtrationandmembraneseparationtechnologies(USPatent7045063,Zhangetal.,2004,Zhang,2007)toproduceandcharacterizeliquidandsolidfertilizers.Membraneseparationwasusedtoseparateandconcentratenutrientsfromthedigestedswinemanureandfoodwastes.IncurrentworksupportedbytheCaliforniaDepartmentofFoodandAgricultureandCentralValleyWaterControlBoard,theydevelopedanintegratedsetoftechnologiesforproducingliquidandsolidfertilizerproductsfromtheanaerobicallydigestedmanure.AflowchartofthesystemisshowninFigure7‐5.Theyhaveconductedlaboratoryandpilotscaleexperiments.Digestedmanurewasprocessedusingathreestageseparationsystemusingascrewpress,screening,andmembranefiltrationprocesses.

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Figure7‐5:Flowchartofanintegratedsystemfortheproductionofbiogasandfertilizersfromorganicwastes(Zhangetal.,2015)

7.4 Codigestion of exogenous biomass feedstocks with manure in AD systems Codigestionoffoodwastewithdairymanurecouldgenerateeconomicbenefitsasaresultofpotentiallysubstantiallyincreasedbiogasproductionandpossibleincomefromtippingordisposalfees(El-Mashad and Zhang, 2007),butatthesametime,itwillincreasestheamountofnutrientsandsaltsthatmustbemanagedonadairyfarm.Thestate’sGeneralDairyOrder(CVRWQCB,2013)requiresnutrientmanagementplansthatlimitNapplicationtoamountsthatdonotexceed1.4timestheamountofnutrientsrecoveredincropbiomass.Addingnewsourcesofnutrientsandsaltsinco‐digestatesbroughtontothefarmincreasesthedifficultyofmeetingtheseobjectivesandrequiresastrategytoremovesurplusnutrientsfromdairyfarms.Thecurrentgeneralorderhasalreadyhasforcedtheoff‐farmuseofaportionofthemanurenutrientscreatedonsomedairyfarms(Viersetal.,2012).Thereislimitedinformationavailableaboutco‐digestionofadditionalorganicmaterialsondairyfarmswithADsystems,especiallyforthespecialconditionsthataffectCaliforniadairies(Westeinde,2009;Informa,2013).Zhangetal.(2007),inacasestudyofadairyfarmnearSacramento,analyzedthelandarearequiredtoabsorballofthemajornutrientelementscontainedinthedigestereffluentswhentwolevelsofadditionalcodigestedfeedstockswereadded.Thefarmanalyzedhad850lactatingcows,210drycow,200calvesand885heifers,and252acres.Thedairyfarmusedatwocroprotation.A120daysilagecornvarietywasplantedinspring(May)andthenannualryegrasscropinfall(September).No‐tillpracticeswereusedfortheryegrass.Threescenarioswerecompared:thefirstforananaerobicdigestertreatingonlythemanureproducedonthedairyfarm.Thesecondandthirdscenariosincludedaddingeither25or50tonsperdayoffoodwaste,for280daysperyear.Thedigestereffluentwasassumedtobeseparatedintosolidsand

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liquidsusingasolids/liquidseparatorthatcanremove37.2%ofthetotalsolidsfromdairymanure.Thesolidfractioncouldbeusedasadigester‐derivedfertilizerthatcouldbeeasilyshippedoutoffarm.Theacreageneededforeachcropasasinglecropinayearwascalculatedbydividingthetotalamountofnutrientscontainedintheeffluentproducedinayearbythenutrientuptakebythecornandryegrassrotationeveryyear.ThetotalamountofsaltsappliedperacrewerecalculatedbysummingtheconcentrationsofNH4+,K+,Cl‐,Ca2+,Mg2+,andNa+intheliquideffluentofthedigester.Thenutrientscontainedinthesolidfractionwerenotincludedinthecalculationsoftheneededacreage.Theareaneededtoabsorbtheeffluentwascalculatedonthebasisof1.4timestheneedednitrogen,andtheexactamountsofphosphorusandpotassium.Fortheeffluentofthedairydigesterwithoutaddedfoodwaste,theliquidmanurehadsufficientNtofertilize248.5acres.Adding25or50tonsperdayoffoodwastetothedigesterincreasedtheadditionalacreageneededby144or319acres,respectively.Whenthelandapplicationofthedigestereffluentwasbasedonnitrogen,theamountsofexcessP,KandsaltsappliedperacreindigestereffluentsdecreasedsincefoodwasteresiduesaddedhadahigherNconcentrationrelativetoPandK.Whenthelandapplicationwaslimitedtocrop’sPrequirements(similartopoliciesinTheNetherlands;Oenema,2001),thedigestereffluentdoesnotsupplysufficientNorKforthecrop’suptakerate,andsupplementalNwasrequired,thoughlessNwasneededwithadditionalfoodwaste.InthePandKbasedlandapplicationschemes,thetotalexcesssaltsappliedperacreslightlyincreasedwithfoodwasteadditions.

7.5 Complications from salts Saltsincowdietsandmanureareanimportantinputwhenmanureordigestateisusedasfertilizer.SaltremovalcomplicatestheproblemofnutrientconcentrationinmanuresorADdigestates,makingitmoredifficultandexpensive.Overtime,sincecattlearefedsaltsaspartofnormaldairyrations,andsincemanureisconcentratedonfarmfields,saltscanaccumulateinfields,andbesubjecttoleaching,inwayssimilartoNO3‐N.SaltcontentcanbequantitativelysimilartoNinmanures(Changetal.,2005).Theestimatedannualinorganicsaltproductionfromadairywith1000cowsisabout350ton(CVRWQCB,2007).Applyingexcessamountsofsaltscouldreducecropyields,especiallyifmanuresareappliedinquantity,repeatedlyovertime.IntheSanJoaquinValley,saltsinmanure,particularlysodium(Na),mustbeconsideredandinsomecircumstancesmayrequiremanagement.SaltsandnitrateloadinglimittheapplicationrateofthedigestateasfertilizerintheCentralValley(ESA,2011).However,theapplicationratesdependonsoilconditionsandsoiltype.Irrigationwaterandrainfallcouldleachsaltsinwell‐drainedsoil.However,forsoilswithhighsalinityandpoordrainage,leachingeffectscouldbeminimal.Moreover,underthecurrentseveredrought,saltaccumulationonafarmcouldbecomeworse.TheamountofsaltpresentinmanureislessthantheamountofsaltappliedinirrigationwaterifhighqualitywateroriginatingtheSierraisused,butequaltoorlessthansaltsinwaterfromthestateandfederalwaterprojecttomostfields.Thisisanunresolvedregulatoryissueandrequiresfurtherresearchandpolicyattention.Thereareseveraltechnologiessuchasreverseosmosiscombinedwithotherphysicalprocessesormembranetechnologiesthatcouldbeappliedforsaltremovalfromwastewatersandtheycanbeappliedformanureanddigestates.However,therearenoknowndemonstrationorcommercialscalesystemsondairyfarms(Maetal.,2013).Co‐digestionwithexogenousfeedstocksincreasestheneedforcreativeADresidualtreatmentoptions.

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7.6 Costs Thecostsofchangingmanuremanagementanduseonfarmsandcorrelatedirrigationpracticesaredifficulttoestimatesincetheywillvarysignificantlyfromfarmtofarm,andbylocationwithintheregion(soiltype,farminfrastructure,localclimate24).ThesameistrueforthecostofneworexperimentaltreatmentstocreateADdigestateproducts.Thereisalackofinformationonthecostsofmanuretreatmentandonthevalueofnewfertilizerproductsthatmightbemadefromthem.Estimatingthesecostswasbeyondthescopeofthisanalysis.Halpern(2013),citedbyMaetal.(2013),estimatedcostsforanintegratedscaled‐upsystemfordigestatemanagementthatconsistedofprimaryscreeningandchemicallyassistedliquidsolidseparationforremovalofsolidsandPseparation;anultrafiltrationprocesstoproduceconcentratecontainingthebulkofthelargerorganicNsolidsandaliquidstream;reverseosmosistotreatthepermeatetoproducecleanwaterandaconcentratedsaltsolutioncontainingdissolvednutrients;andvacuumevaporationtofatherconcentratethenutrientsolution.Theestimatedoperatingcostwas$900‐1000percowperyear.Theauthorsdidnotreportcapitalcosts,buttheselikelyarehighduetothesystem’scomplexity.Althoughthecurrenthighcostsofdigestatetreatment,consideringtheincreasingpricesofthesynthetic,highvalueproductsfrommanureanddigestate,wouldbeagoodsourceofrevenueforadairy.Moreover,innovativetechnologies,improvementinenergyuseandprocessefficienciesincurrentindustriesandtheinstallationofdemonstrationsystemsonfarmsareneededtopromotethefurtheradoptionofmanuremanagementonfarms.

7.7 Water Use Implications Dairyfarmsusewaterforlivestocktodrink,operationandcleaningofthemilkingparlorandmilkhandlingequipment,otherlivestockcareandhousingneeds,andtoproducecropsforfeed.Therearealargenumberofreportsavailablequantifyingtypicalamountsofwateruseondairiesindifferentstatesforthesetypesofuses(Meyeretal.,2006;Bray,2014;Harneretal.,2013;Falk,2014;CMAB,2015).ThemostrelevantassessmentofwateruseonCaliforniadairiespublishedbyMeyeretal.(2006)examined16dairiesacrossthestateranginginsizefrom125–2,830milkingcowsandfoundthatwaterdestinedforliquidstorageponds(notincludingdrinkingorirrigationwaters)primarilyconsistedofwaterformilkingparlorandudderhygieneneeds(56%),followedbysiterunoff(24%),manure(11%),anddirectrainfallonponds(9%).Overallwaterusedidnotvarymuchseasonally,buthadhighcross‐farmvariability(77±39gal/cow/day).Noneofthedairiesinthestudyreportedusingfreshwaterforflushingofmanurefromhousingareas,presumablyusingonlyrecycledlagoonwater,orforcoolinganimalsduringhotweather.SummersandWilliams(2013),recentlydetailedone850milkingcowCaliforniadairywhichaddedanaverageof11gal/cow/dayoffreshwaterthroughthemilkingparlorand24“Costsformitigationorabatementvarywidelyandcansometimesbedifficulttoestimate.Inparticular,theamountofnitrateleachedfromirrigatedcropfields(thelargestsource)isdeterminedbyacomplexinteractionofNcycleprocesses,soilproperties,andfarmmanagementdecisions;itisthereforevirtuallyimpossibletogeneralizemitigationcostsperunitofnitrateloaddecrease,allowingforonlybroadestimations.”Dzruellaetal.,2012Page1.

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enteringthemanuremanagementsystem,whileover750gal/cow/daywererecycledfromthesecondarylagoonforfreestallflushingneeds.BjornebergandKing(2014)examinedgroundwateruseonsixdairiesinsouthernIdahoranginginsizefrom660‐6,400milkingcowsemployingparlorflushingandvacuummanurecollectionfromhousingareas,whichaveraged57±14gal/cow/day(includingdrinkingwater),whichislowerthanthenumbersreportedbyMeyeretal,althoughnotdirectlycomparable.Milkcowdrinkingwaterneedscanvarysignificantlyandmayrangefromapproximately12‐45gal/cow/day,ormore(BjornebergandKing2014).Duringveryhottemperatures,cowstendtoreducefeedintakeandcorrespondinglymilkproduction.Tohelpoffsetthistendency,manydairiesusemistorsprinklersystemstocooloffcowsastheyeatandelsewhere(Figure7‐6).Theamountofwaterusedwillvarywiththetemperatureswherethedairyislocated,andhowcoolingwaterisapplied.

Figure7‐6:Onemethodofcoolingcowswhiletheyfeed25

25Source:http://www.google.com/search?q=cows+under+sprinklers&nord=1&biw=1190&bih=819&site=webhp&tbm=isch&tbo=u&source=univ&sa=X&ved=0ahUKEwja4cuOv97JAhVL5mMKHcO4BAQQ7AkILQ&dpr=1.25#imgrc=2Qr6lNALCqL4NM%3A

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Figure7‐7:Anexampleofmilkingparlorflushing26

PossibleeffectsonfreshwaterusewithassociatedmanuremanagementscenariosAnaerobicDigestion(CoveredLagoons):Theprimaryeffectonwateruseofcoveringstoragelagoonstocreateanaerobicdigesterswouldbetoreduceevaporationfromlagoonsurfaces.Usinganaverageevaporationrateof65”peryearasanexample,approximately4800gallons/day/lagoon‐acremightberetainedforirrigationuses.Lagoonsurfacerainwatercollectionwouldbeexcluded,althoughalternativecollectionmethodscouldbeemployedtocapturerunoffsothat,forexample,asitewith10”peryearofprecipitationcouldretaintheapproximately750gal/day/lagoon‐acrethatisalreadycollectedbyexistingopenlagoons.Overthecourseofayear,thiscouldequalapproximately5acftperlagoonacreperyear.Fora1000cowdairy,50acrefeetperyearmightbesaved,enoughtoirrigateapproximately5acresofcrops.ButthedigestatesremovedfromADsystemsareequallymoist.Wetdigestateor(Ifsolid–liquidseparationoccurs)liquiddigestatestorage,presumablyinopenlagoons,wouldbesubjecttothesameevaporationlossesastraditionallagoons.Somestorageofthiswaterwouldoccursinceitcannotallbeappliedtofieldsimmediatelyafterremoval.Theamountofliquiddigestatesstoredandthelengthofstoragewouldvarybyseasonandfarm,butlikelyresemblecurrentarrangementsforrawmanurestorageinlagoons.ScrapeScenarios(withADordrying/composting):Assumingthatflushingoperationsmainlyuserecycledlagoonwater,theextentofwatersavingspossiblebyswitchingtodryscapeoperationsmaynotbeasdrasticasinitiallyenvisioned.Energyinputrelatedtowatercirculationwouldbereduced.Althoughpoorlyquantifiedintheliterature,operationswherefreshwaterisusedtodirectlyflushconcretehousinglanesortodiluteflushingwaterwouldpresentopportunitiesfordirectsavings.Additionalsavingsarepossiblethroughminimizingevaporativelossesviareducingnecessarylagoonstorage

26Source:Ludington,etal.,2004

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areasorcontinuallywettedsurfaceswithinadairy(withexampleimpactperacreasillustratedabove).However,thescrapescenariosevaluatedinthisreportassume6‐12monthsofscrapingmightoccurwithparlormanureandwashwatersstillassumedtobedepositedintoalagoonthroughouttheyear.Currently,dairiesthatutilizeflushsystemstakeadvantageofliquidwastewaterandnutrientdistributionmethodsanditispossiblethatupstreammethodsformilkcooling,parlorwashing,udderwashing,cowcooling,andequipmentandfacilitysanitationwillshifttohavedifferentoptimumconfigurationsgivenachangeindownstreammanuremanagementmethods,althoughtheseshiftsarespeculativeanddifficulttoquantifywithoutfurtherresearch.SolidSeparationorAeration:Assumingothermanuremanagementpracticesareunchanged,littlechangeinoverallwaterusewouldbeexpectedwiththesescenarios.Somesolidsseparationtechnologiesmayrequireperiodicfreshorrecycledwaterrinsecycles.Conversely,increasedsolidsseparationfromwastewatersmayenableimprovedopportunitiesfordownstreamwaterreuseorrecyclingtotakeplace,butstorage,likelyinopenlagoons,wouldstillbeinvolved.Aerationoflagoonsstillreliesonopenlagoonswithassociatedwaterlossthroughevaporationandmaypromoteincreasedevaporationrates,butthishasnotbeenmeasuredtoourknowledge.

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8. Future Work and Recommendations TheresultsofthisworkprovideabasisforestimatingexpensesforvariousmethanereducingstrategiesofmanuremanagementonCaliforniadairies,butthequalityofindividualestimatesarenotequal.Preliminarycostsassociatedwithimplementationofseveralmanuremanagementstrategiesandassociatedexpectedmitigationpotentialsarepresented.Insomecases,estimatesarebasedonlargeamountsofdataorexperiencewiththetechnologymodeled,butinothers,muchless.Whereimportantlimitationsexist,recommendationsaremadehereforfurtherquantificationandresearch.Insomecase,estimatesanddatamaybeinsufficientasabasisforpolicychoicesatthecurrenttime.Estimatedcostsarenotintendedtoberepresentativeforanyspecificdairyandthisreportisafirstattemptatquantifyingmitigationcostsforawiderangeofcomplexanddynamicscenarios.Furtherworkandinvestigationiswarrantedintomanyoftheassumptionsusedineachmodel.Additionally,researchisneededinmanyareastoaddressuncertaintiesandboostpromisingbutlessdevelopedtechnologies.Specificexamplesoftheseneedsarehighlightedbelow.GeneralManureManagement

Manuremanagementpracticesonindividualdairiesinthestateneedtobebetterquantified.AnnualGHGestimatesrelyonstatewideestimatesofthemostcommonmanuremanagementpractices,howeverthedetailedsupportforsuchestimatesisnotwellreported.Theproportionofmanureinmanagementusingscraping,solid‐liquidseparation,lagoonstorage,andothersystemsarepoorlydocumentedandmayvarybasedondairysizeorlocation.RecentregulationsrequiringthatCAFO’shavecertifiedwastemanagementplans(WMPs)andnutrientmanagementplans(NMPs)mayenablereadyaccesstosomeofthisinformation,howeveranalysisandsynthesisoftheinformationisneeded.

Emissionsfromexistingoperationsneedtobestudiedanddocumentedmorefully.Mostimportantly,methaneandGHGemissionsfromdiverselagoonsinCalifornianeedtobemorefullymeasuredanddocumented,asdolessprevalentpracticessuchassolidsstorage,drying,andcomposting.EmissionsfromsolidssettlingbasinswhichaccompanymanylagoonsinthestatearenotwellcharacterizedforGHGemissionsnoraddressedincurrentinventoriesormethanemitigationprotocols.

Thescopeofevaluationforalternativemanuremanagementsystemsneedstobeextendedandintegratedwithlandapplication,use,ordisposalscenarios.Thequantitativescopeofthisreportwaslimitedtomethanemitigationfromlagoonsandevaluatingalternativeemissionsfromprocessingorstorage,however,theagronomic(cropproduction)andenvironmentalconsequences(emissionstoairandsurfaceandgroundwater)ofpotentiallylarge‐scalechangesinmanuremanagementstrategiesonCaliforniadairyfarmsrequirefurthermeasurementandmodeling.

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AnaerobicDigestion

BetterdataonGHGemissionsfromADsystemsorcoveringofexistinglagoonsareneeded.Althoughthepracticeofanaerobicdigestioniswelldemonstratedandunderstood,questionsremainrelatedtomethaneemissionsincludingimpactofeffluentponds(coveredoruncovered)andfugitivemethanefrombiogascollectionandenergysystems(methaneleaks).Academicinquiryandmeasurementsofthistypeonactual,representativefarmswouldgreatlyimprovetheestimates.

Thereisaneedtoimproveestimatesofcapitalandoperatingandmaintenancecostsfordairybioenergysystems.Theliteratureingeneralappearstounderestimatethesecosts.Ifpublicgrantfundsareusedtohelpdefrayupfrontcosts,thenthereshouldbeamechanisminthecontracttomonitortheprojectandgatheractualenergyperformanceandoperatingcostdata(andunforeseencapitalcostsnotknownattimeofproposal).Improvedknowledgeofrealcostsandperformancecanbeusedtoinformpolicyandcalibratefuturepublicgrantprograms.

Researchontechnologiesforhighervalueproductsorco‐productsisneeded.Researchisneededonnewandexistingtechnologyfortreatingdigestereffluents(digestate)toconvertitnewfertilizerproductsandusessuchasfertilizersubstitutes,soilamendments,andotherproducts.Alternativeorupgradedproductsfrommethaneordigestatemayalsoimproveprojecteconomics.

Life‐cycleassessmentsareneeded.ResearchonGHGimpactsandlife‐cycleassessmentsofdairydigestatesandnewfertilizerby‐productsareneeded.

TransitioningtoScrapeSystemswithDryingorComposting

Additionalcostdataareneeded.Costdatafrommorefarmsthatpractice,or

successfullytransitionedto,scrapemanuremanagementsystemswouldimprovemodelingofthisscenario.

Waterimpactsneedfurtherevaluation.Investigationofwaterqualityandirrigationstrategyimpactsduetotransitiontoscapeisneeded.

ActualGHGemissionsneedtobemeasured.AbetterunderstandingoftheGHGconsequencesandotheremissionsfromscrapedmanureisneeded,particularlywhetherscrapedandprocessedmanurebehavesasanaerobicslurry,forwhatduration,andwhatappropriateMCFshouldbeapplied.Thedryingandcompostscenariossufferfromalackofdataoneffectsonairandwaterqualityunderfarmconditions.

Marketanalysisanddevelopmentformanureproductsareneeded.Forcomposting,abetterunderstandingofthecurrentandfuturemarketandvalueforcompostedproductsandbulkingagentsneededforon‐farmcompostingwouldimprovecostestimates.Aswiththeanaerobicdigestionscenarios,significant

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nutrientsmaybeaccumulatedthiswayandpotentialuseasfertilizersandsoilorganicmatteramendmentsmaybepossible.

SolidLiquidSeparation

Bettercurrentadoptioninformationneeded.Anaccurate,currentestimateof

howmuchsolid/liquidseparationiscurrentlypracticedonCaliforniadairiesandwhatadditionalfractionofmanurecanbetargetedwiththistechniqueisneeded.

Bettercostdataneededforexpandedrangeofseparationstechnologiesavailable.Abetterunderstandingofthecostsassociatedwithsolidliquidseparationsystemsisneeded.Moreeffectiveorsophisticatedtechnologiesforsolidsremovalexist,andwhilemayincurhighercosts,canhavegreaterGHGmitigationpotentials.Thevalueoftheseparatedfractionsshouldbecomparedwiththecostsofthesolid/liquidseparationtechnologies.

Additionalcorrelationsbetweensolidstype/sizeandmethaneemissionsareneeded.Researchisneededtobetterdeterminemethaneconversionfactorsassociatedwithdifferentsizedsolidsforbetteremissionsreductionsestimates.

Aeration

Additionalresearchandpracticaldemonstrationnecessary.AerationisastandardprocessusedinwastewatertreatmentplantsforBODreductionbutthereislittletechnicalliteratureontheapplicationofthistechnologytodairymanure.Generally,ithasbeeninvestigatedforodorcontrolinmanurelagoons,andmanyauthorsconcludeitisnoteffectiveortoocostly.However,thetheoreticalpotentialforGHGmitigationsexistsandresultsinthisreportindicateitmaybeacostcompetitive.Researchonaeratedlagooncost,GHGreductioneffectiveness,andeffectsonemissionsisneededbeforeadvocatingthesetechniques.Thereisaneedtounderstandtheimpactoftheeffluentsofaeratedlagoonsonthechemicalandphysicalcharacteristicsofsurfaceandgroundwatercontamination.Thepersistenceandsolubilityofdifferentchemicalsintheaeratedlagoonwatershouldbedeterminedunderdifferentweatherconditions.Thereisalsoaneedtoconductlongtermmonitoringofthefugitivegasesfromaeratedlagoonandtheireffectsonairandwatercontamination.

86

Appendices Appendix2.1:BackgroundonAnaerobicandAerobicBiologicalDegradation.........................87Appendix2.2:IPCCManureManagementSystemDefinitions..........................................................89Appendix3.1:Tier1LagoonUpgradewithCoverandFlareScenario:MitigationCostCurve

Development.............................................................................................................................................90Appendix3.2:MitigationCostCurves:AllDigester‐to‐EnergyScenarios....................................91Appendix3.3MitigationCostCurveDevelopment‐Digesters–ReciprocatingEngine..........92Appendix3.4MitigationCostCurveDevelopment‐Digesters–Microturbines........................93Appendix3.5MitigationCostCurveDevelopment‐Digesters–FuelCells..................................94Appendix3.6MitigationCostCurveDevelopment‐Digesters–RNGwithFuelingStation..95Appendix3.7.GHGModel:LagoonbasecaseandTier1Cover&Flare........................................96Appendix3.8.DigesterScenarioModelandper‐cowoutputs...........................................................97Appendix3.9.EffluentPondCoverCostadderfordigesterscenarios...........................................98Appendix3.10.FuelCellCapitalCostAdderandO&MAnalysis......................................................99Appendix3.11.RNGModelCapitalCostAdderandO&MAnalysis...............................................100Appendix4.1:Convertingfromflushtoscape:Supportinginformation....................................101Appendix4.2:Scrapetoopensolardrying(6mo.)scenariocostdevelopmenttable..........105Appendix4.3:Scrapetoopensolardrying(8mo.)scenariocostdevelopmenttable..........106Appendix4.4:Scrapetoclosedsolardryingscenariocostdevelopmenttable.......................107Appendix4.5:Scrapetoforceddryingwithnaturalgasscenariocostdevelopmenttable108Appendix4.6:Scrapetocompostingwithbulkingagentscenariocostdevelopmenttable

.......................................................................................................................................................................109Appendix5:SolidLiquidseparationscenariocostdevelopmenttable.......................................110Appendix6.1:Aerationscenario(loweffectiveness)costdevelopmenttable........................111Appendix6.2:Aerationscenario(higheffectiveness)costdevelopmenttable.......................112

87

Appendix2.1:BackgroundonAnaerobicandAerobicBiologicalDegradation MethaneemissionsfromanaerobiclagoonmanurestorageManure storage lagoons, a source of methane emissions, are common for wastewatertreatment in confined animal feeding operations (CAFOs). Anaerobic conditionspredominate in animal manure lagoons. Under anaerobic condition organic material isdegradedbyamixedextracellular enzymesand culturesofbacteria in anumberof sub‐processes that occur in series and parallel manners. The particulate organic matter ishydrolyzed by extracellular enzymes of microorganisms to soluble compounds such asaminoacids,sugarsandlong‐chainfattyacids.Thentheproductsofthehydrolysissteparefermented into short‐chain volatile fatty acids (VFAs), alcohols, ammonia and hydrogensulfide.TheVFAs(otherthanacetate)andalcoholsarefurtherconvertedbyacetogenesisbacteriatoaceticacid,hydrogenandcarbondioxide,whicharethenconvertedtomethaneand carbon dioxide a specialized group ofmicroorganism calledmethanogens. The finalproductsof theanaerobicdecompositionoforganicmatteraremethane, carbondioxide,hydrogensulfideandammonia.Theanaerobicdigestionmineralizes theorganicnitrogenintoammoniathatisadesirableformofnitrogenforplantuptake.The microbial activity of aerobic and anaerobic microorganisms (methanogenesis) inlagoons is an important factor affecting the removal rates of organic matter. There areseveral factors affecting the growth and activity of methanogenesis including pH,temperature and the presence of chemical inhibitors and oxygen. The preferred pH formethanogenesis growth is near‐neutral. However they can also grow at pH between 5.5and9.7.Thebicarbonate‐ammoniabufferistheprimaryparametercontrollingthepHandprocess stability. Generally,manure lagoonshavepH ranging from7.0‐8.0 depending onanimaltypeandration,manureloading,andweatherconditions.Anaerobic digestion of organicmaterials occurs in awide range of temperatures. It canoccuratatemperatureaslowas4°C,butthedegradationrateoforganicmaterialincreaseswith the increase of temperature. Three temperature ranges have been explored foranaerobicdigestion,includingthepsychrophilicrange(10‐20°C),themesophilicrange(20‐ 45°C, typically 35°C), and thermophilic range (45‐60°C, typically 55°C). Depending onweatherandsoilconditions,psychrophilicandlowtemperaturerangesofmesophiliccouldbe found in manure lagoons. Anaerobic digesters, however, are commonly designed tooperate in either mesophilic or thermophilic range. This is because digestion at hightemperatures allows higher organic loading rates and requires shorter solids retentiontime and is therefore more space‐efficient. Moreover, high temperatures increase thedestructionofpathogensthatmaybepresentinmanure.Highconcentrationsofdegradation intermediateproducts suchasammoniaandVFAs inthe digestion media could inhibit the activity of methanogenesis. High ammoniaconcentrations coincidewith high pH values could cause inhibition or total cessation ofanaerobicdigestion, especially in the anaerobicdigestersoperatedathigh temperatures.ThisisduetothefactthatathighdigestiontemperaturesandpHvalues,thefreeammoniaconcentrationincreases.Theincreaseofammoniaconcentrationinlagooncould increaseitsemissionstotheenvironment.Ammoniaemissionfrommanurestoredinopenlagoonsishigherthanthecoveredlagoons.

88

Methanogensareobligateanaerobesandarekilledwhenexposedtoair.Methanogenesiscan growwell at Oxidation Reduction Potentials (ORP) below ‐200mV (Conrad, 1989).Dissolved oxygen concentrations in manure lagoons are low that can barely supportautotrophicnitrification.DuceyandHunt (2013)measured lowORP(‐86 to ‐330mV) inswinelagoonsanddeducedthatmethanogenesisoccursifnotinthewatercolumnitoccursin thesludge layerof lagoons.Table 0.1shows the relationshipbetweendissolvedoxygen(DO),redoxpotential,andbiochemicalreactions(Mitloehneretal.,2004).

Table0.1:Relationshipsbetweendissolvedoxygen(DO),redoxpotential,andbiochemicalreactionsDissolved Oxygen (mg DO/L)

Oxidation/Reduction Potential (ORP, Emv)

Biochemical Reactions

Biological Processes

Very low -400 H2& CO2 to CH4* Anaerobic

Low -300 SO4 to H2S, HS- Anaerobic Intermediate 0 Facultative Anaerobic/aerobic Medium high +200 NH4

+ to NO2- Aerobic

High (> 1 mg/L) +250 NH4+ to NO3

-, NO2- Aerobic

*Bold reagents are the major products developed under the corresponding oxygenation level

89

Appendix2.2:IPCCManureManagementSystemDefinitions

90

Appendix3.1:Tier1LagoonUpgradewithCoverandFlareScenario:MitigationCostCurveDevelopment

Dairy

Size1

Lagoon surface

area 2

New Tier 1

lagoon 2

Cover

Costs 3

Flare + balance of

plant 4

Total Capital

Flare equipment

&Cover Costs only (for

reference)

O&M

($/y) 5

Annual Cost ($, 10 year

loan) 6

Annual Cost ($, 20 year

loan) 7

Emission reduction

(Mg/y, capture and

destroy) 8

Mitigation Cost (10 yr debt term)

Mitigation Cost (20 yr debt term)

Adult Cows

acres $$

($2.60/ft 2̂)$ $ $ $/yr $/yr $/yr MgCO2e/yr $/Mg $/Mg

300 2.1 252,000 237,838 53,846 543,684 291,684 11,667 92,692 67,043 1,486 62.36 45.11750 3.4 399,000 385,070 105,044 889,114 490,114 19,605 152,109 110,163 3,716 40.94 29.65

1,500 6.0 714,000 679,536 174,146 1,567,682 853,682 34,147 267,778 193,819 7,432 36.03 26.083,000 10.7 1,321,000 1,211,839 288,705 2,821,544 1,500,544 60,022 480,515 347,402 14,863 32.33 23.375,000 14.5 1,772,724 1,646,069 419,033 3,837,826 2,065,102 82,604 654,553 473,495 24,772 26.42 19.1110,000 23.8 2,926,021 2,695,634 694,687 6,316,342 3,390,321 135,613 1,076,934 778,946 49,544 21.74 15.72

Modeled Assumptions1 Dairy size characterized by # of adult cows (80% lactating/20% dry animals)

2

3 $2.60 per square foot installed. Cover Costs from Environmental Fabrics, Inc. (EFI)

4

5 4% of cover and balance of plant. - ICF (2013)6 8% interest rate, 10-year term for capital loan, plus annual O&M7 8% interest rate, 20-year term for capital loan, plus annual O&M8 Assumes 60% manure from adult cows reaches lagoon (base case and project assumptions)

Total 20-year annualized cost per head, multiplied by dairy size, divided by average GHG emissions reduction per dairy size.

References:A http://www.waterboards.ca.gov/centralvalley/water_issues/dairies/historical_dairy_program_info/reissue_dairy/provost_pritchard_memo.pdf.B http://www.usda.gov/oce/climate_change/mitigation_technologies/GHG_Mitigation_Options.pdf

Environmental Fabrics, Inc. (EFI), CDFA Digester proposals

Cost Curves ‐ (Power Law Regression Fits Shown)

From: Schaap, J. and Bommelje (2013). Costs to Retrofit Existing Dairies That Do Not Have Tier 1 or Tier 2 Lagoons. Provost & Pritchard Consulting Group. Memo to Central Valley Regional Water Quality Control Board.

From: ICF International, (2013). Greenhouse Gas Mitigation Options and Costs for Agricultural Land and Animal Production w ithin the United States, Contractor report to USDA. Contract No. AG-3142-P-10-0214.

y = 290.72x‐0.282

R² = 0.9733

y = 210.61x‐0.282

R² = 0.97380

10

20

30

40

50

60

0 2,000 4,000 6,000 8,000 10,000

($/ M

G CO

2EQ)

NO. ADULT COWS

MITIGATION COST ‐ COVER AND FLARE

10 yr. debt

20yr. debt Term

91

Appendix3.2:MitigationCostCurves:AllDigester‐to‐EnergyScenarios

0

20

40

60

80

100

120

140

0 2,000 4,000 6,000 8,000 10,000

($/ Mg CO2eq

)


Mitigation Cost‐Curves: Recip. Engine

Tank/Pllug Flow w/ Covered Pond

Tank/Plug Flow Digester

Lagoon w/ Covered Eff. Pond

Lagoon Digester

0

20

40

60

80

100

120

140

0 2,000 4,000 6,000 8,000 10,000

($/ Mg CO2eq

)


Mitigation Cost‐Curves: Microturbine




Lagoon Digester

0

20

40

60

80

100

120

140

0 2,000 4,000 6,000 8,000 10,000

($/ Mg CO2eq

)


Mitigation Cost‐Curves: Fuel Cell




Lagoon Digester

0

20

40

60

80

100

120

140

160

180

0 2,000 4,000 6,000 8,000 10,000

($/ Mg CO2eq)


Mitigation Cost‐Curves: CNG




Lagoon Digester

92

Appendix3.3MitigationCostCurveDevelopment‐Digesters–ReciprocatingEngine.

Lagoon Digester, Uncovered Eff. Pond, Recip Engine y = 696.38x-0.378

Adult Cows

Total Capital

($)

Energy

Capacity

(kW, 100%

cap factor)

Total Energy

(kWh/y,

100% cap

fact)

O&M ($/y)

Annual Cost

($, 10 year

loan)

Annual Cost

($, 20 year

loan)

Energy

Revenue

($/y)

Net Cost, 10 yr.

loan term ($/y)

Net Cost, 20

yr. loan term

($/y)

Emission

reduction

(Mg/y)

Mitigation

Cost ($/Mg ‐

10 yr debt

term)

Mitigation

Cost ($/Mg ‐

20 yr debt

term)

300 875,536 35 303,886 11,451 141,932 100,627 38,594 103,339 62,033 1,333 77.51 46.53750 1,740,721 87 759,715 28,629 288,047 205,925 96,484 191,564 109,441 3,333 57.48 32.84

1500 2,927,532 173 1,519,431 57,257 493,546 355,433 192,968 300,578 162,465 6,666 45.09 24.373000 4,923,503 347 3,038,861 114,515 848,262 615,984 385,935 462,326 230,049 13,332 34.68 17.265000 7,222,055 578 5,064,769 190,858 1,267,157 926,440 643,226 623,931 283,214 22,220 28.08 12.75

10000 12,146,000 1156 10,129,538 381,716 2,191,828 1,618,812 1,286,451 905,376 332,361 44,440 20.37 7.48

Complete mix or Plug flow digester w/UNCOVERED eff pond

Adult Cows

Total Capital

($)

Energy

Capacity

(kW, 100%

cap factor)

Total Energy

(kWh/y,

100% cap

fact)

O&M ($/y)

Annual Cost

($, 10 year

loan)

Annual Cost

($, 20 year

loan)

Energy

Revenue

($/y)

Net Cost, 10 yr.

loan term ($/y)

Net Cost, 20

yr. loan term

($/y)

Emission

reduction

(Mg/y)

Mitigation

Cost ($/Mg ‐

10 yr debt

term)

Mitigation

Cost ($/Mg ‐

20 yr debt

term)300 1,146,424 39 341,872 12,883 183,734 129,649 43,418 140,316 86,231 1,452 96.65 59.40750 2,227,675 98 854,680 32,207 364,197 259,101 108,544 255,652 150,557 3,629 70.44 41.48

1500 3,682,126 195 1,709,359 64,414 613,160 439,447 217,089 396,071 222,359 7,259 54.57 30.633000 6,086,188 390 3,418,719 128,829 1,035,851 748,721 434,177 601,673 314,543 14,517 41.45 21.675000 8,814,258 650 5,697,865 214,715 1,528,299 1,112,467 723,629 804,670 388,838 24,196 33.26 16.07

10000 14,569,092 1301 11,395,730 429,430 2,600,654 1,913,324 1,447,258 1,153,397 466,066 48,391 23.83 9.63

Covered Lagoon Digester w/ COVERED EFF. Pond

Adult Cows

Total Capital

($)

Energy

Capacity

(kW, 100%

cap factor)

Total Energy

(kWh/y,

100% cap

fact)

O&M ($/y)

Annual Cost

($, 10 year

loan)

Annual Cost

($, 20 year

loan)

Energy

Revenue

($/y)

Net Cost, 10 yr.

loan term ($/y)

Net Cost, 20

yr. loan term

($/y)

Emission

reduction

(Mg/y)

Mitigation

Cost ($/Mg ‐

10 yr debt

term)

Mitigation

Cost ($/Mg ‐

20 yr debt

term)

300 1,023,507 38 330,476 12,453 164,986 116,700 41,970 123,016 74,729 1,472 83.55 50.76750 2,024,871 94 826,190 31,134 332,899 237,371 104,926 227,973 132,445 3,681 61.94 35.98

1500 3,393,023 189 1,652,381 62,267 567,928 407,854 209,852 358,075 198,002 7,361 48.64 26.903000 5,686,064 377 3,304,762 124,535 971,926 703,673 419,705 552,221 283,968 14,723 37.51 19.295000 8,319,172 629 5,507,936 207,558 1,447,360 1,054,884 699,508 747,852 355,376 24,538 30.48 14.48

10000 13,943,283 1258 11,015,872 415,116 2,493,076 1,835,270 1,399,016 1,094,060 436,254 49,076 22.29 8.89

Complete mix / Plug flow w/ COVERED EFF. Pond

Adult Cows

Total Capital

($)

Energy

Capacity

(kW, 100%

cap factor)

Total Energy

(kWh/y,

100% cap

fact)

O&M ($/y)

Annual Cost

($, 10 year

loan)

Annual Cost

($, 20 year

loan)

Energy

Revenue

($/y)

Net Cost, 10 yr.

loan term ($/y)

Net Cost, 20

yr. loan term

($/y)

Emission

reduction

(Mg/y)

Mitigation

Cost ($/Mg ‐

10 yr debt

term)

Mitigation

Cost ($/Mg ‐

20 yr debt

term)

300 1,294,395 41 355,167 13,384 206,287 145,221 45,106 161,181 100,115 1,523 105.80 65.71750 2,511,825 101 887,917 33,460 407,796 289,295 112,765 295,030 176,529 3,809 77.46 46.35

1500 4,147,617 203 1,775,835 66,920 685,037 489,363 225,531 459,506 263,832 7,617 60.32 34.643000 6,848,749 405 3,551,669 133,839 1,154,505 831,399 451,062 703,443 380,337 15,235 46.17 24.975000 9,911,375 676 5,919,449 223,065 1,700,152 1,232,560 751,770 948,382 480,790 25,391 37.35 18.94

10000 16,366,375 1351 11,838,897 446,130 2,885,202 2,113,081 1,503,540 1,381,663 609,541 50,782 27.21 12.00

RECIP ENGINES

y = 696.38x‐0.378

y = 944.08x‐0.5110

10

20

30

40

50

60

70

80

90

100

0 2,000 4,000 6,000 8,000 10,000

($/ Mg CO

2eq)


Mitigation Cost ‐ Lagoon Digester, uncovered effluent Pond Recip Engine

10 yr. debt

20yr. debt Term

y = 962.72x‐0.397

y = 1186.2x‐0.51

0

10

20

30

40

50

60

70

80

90

100

0 2,000 4,000 6,000 8,000 10,000

($/ M

g CO2

eq)

Number of. Adult Cows

Mitigation Cost ‐ Above Ground Tank or Plug Flow Digester with uncovered effluent Pond,

Recip

10 yr. debt

20yr. debt Term

y = 731.44x‐0.374

y = 894.19x‐0.488

0

10

20

30

40

50

60

70

80

90

100

0 2,000 4,000 6,000 8,000 10,000

($/ M

g CO2

eq)


Mitigation Cost ‐ Lagoon Digester with COVERED effluent Pond, Recip

10 yr. debt

20yr. debt Term

y = 982.16x‐0.385

y = 1078.3x‐0.478

0

10

20

30

40

50

60

70

80

90

100

0 2,000 4,000 6,000 8,000 10,000

($/ Mg CO2eq

)


Mitigation Cost ‐ Above Ground Tank or Plug Flow Digester with COVERED effluent Pond,

Recip.

10 yr. debt

20yr. debt Term

93

Appendix3.4MitigationCostCurveDevelopment‐Digesters–Microturbines.

Lagoon Digester, Uncovered Eff. Pond, Microturbine

Adult Cows

Total Capital

($)

Energy

Capacity

(kW, 100%

cap factor)

Total Energy

(kWh/y, 100%

cap fact)

O&M ($/y)

Annual Cost

($, 10 year

loan)

Annual Cost

($, 20 year

loan)

Energy

Revenue

($/y)

Net Cost, 10 yr.

loan term ($/y)

Net Cost, 20

yr. loan term

($/y)

Emission

reduction

(Mg/y)

Mitigation

Cost ($/Mg ‐

10 yr debt

term)

Mitigation

Cost ($/Mg ‐

20 yr debt

term)

300 875,536 27 232,979 8,779 139,260 97,955 29,588 109,672 68,366 1,333 82.26 51.28750 1,740,721 66 582,448 21,949 281,367 199,245 73,971 207,396 125,274 3,333 62.23 37.59

1500 2,927,532 133 1,164,897 43,897 480,186 342,073 147,942 332,244 194,131 6,666 49.84 29.123000 4,923,503 266 2,329,794 87,795 821,542 589,264 295,884 525,658 293,380 13,332 39.43 22.015000 7,222,055 443 3,882,989 146,324 1,222,623 881,907 493,140 729,484 388,767 22,220 32.83 17.50

10000 12,146,000 887 7,765,979 292,649 2,102,761 1,529,745 986,279 1,116,481 543,466 44,440 25.12 12.23

Complete mix or Plug flow digester w/UNCOVERED eff pond

Adult Cows

Total Capital

($)

Energy

Capacity

(kW, 100%

cap factor)

Total Energy

(kWh/y, 100%

cap fact)

O&M ($/y)

Annual Cost

($, 10 year

loan)

Annual Cost

($, 20 year

loan)

Energy

Revenue

($/y)

Net Cost, 10 yr.

loan term ($/y)

Net Cost, 20

yr. loan term

($/y)

Emission

reduction

(Mg/y)

Mitigation

Cost ($/Mg ‐

10 yr debt

term)

Mitigation

Cost ($/Mg ‐

20 yr debt

term)300 1,146,424 30 262,102 9,877 180,728 126,643 33,287 147,441 93,356 1,452 101.56 64.31750 2,227,675 75 655,254 24,692 356,682 251,586 83,217 273,464 168,369 3,629 75.35 46.39

1500 3,682,126 150 1,310,509 49,384 598,130 424,417 166,435 431,695 257,982 7,259 59.47 35.543000 6,086,188 299 2,621,018 98,769 1,005,790 718,661 332,869 672,921 385,791 14,517 46.35 26.575000 8,814,258 499 4,368,363 164,615 1,478,199 1,062,366 554,782 923,417 507,584 24,196 38.16 20.98

10000 14,569,092 997 8,736,726 329,230 2,500,454 1,813,124 1,109,564 1,390,890 703,560 48,391 28.74 14.54

Covered Lagoon Digester w/ COVERED EFF. Pond

Adult Cows

Total Capital

($)

Energy

Capacity

(kW, 100%

cap factor)

Total Energy

(kWh/y, 100%

cap fact)

O&M ($/y)

Annual Cost

($, 10 year

loan)

Annual Cost

($, 20 year

loan)

Energy

Revenue

($/y)

Net Cost, 10 yr.

loan term ($/y)

Net Cost, 20

yr. loan term

($/y)

Emission

reduction

(Mg/y)

Mitigation

Cost ($/Mg ‐

10 yr debt

term)

Mitigation

Cost ($/Mg ‐

20 yr debt

term)

300 1,023,507 29 253,365 9,548 162,080 113,794 32,177 129,903 81,617 1,472 88.23 55.44750 2,024,871 72 633,413 23,869 325,635 230,107 80,443 245,191 149,663 3,681 66.62 40.66

1500 3,393,023 145 1,266,825 47,738 553,399 393,325 160,887 392,512 232,438 7,361 53.32 31.583000 5,686,064 289 2,533,651 95,477 942,868 674,615 321,774 621,094 352,841 14,723 42.19 23.975000 8,319,172 482 4,222,751 159,128 1,398,930 1,006,454 536,289 862,640 470,164 24,538 35.16 19.16

10000 13,943,283 964 8,445,502 318,255 2,396,216 1,738,409 1,072,579 1,323,637 665,831 49,076 26.97 13.57

Complete mix / Plug flow w/ COVERED EFF. Pond

Adult Cows

Total Capital

($)

Energy

Capacity

(kW, 100%

cap factor)

Total Energy

(kWh/y, 100%

cap fact)

O&M ($/y)

Annual Cost

($, 10 year

loan)

Annual Cost

($, 20 year

loan)

Energy

Revenue

($/y)

Net Cost, 10 yr.

loan term ($/y)

Net Cost, 20

yr. loan term

($/y)

Emission

reduction

(Mg/y)

Mitigation

Cost ($/Mg ‐

10 yr debt

term)

Mitigation

Cost ($/Mg ‐

20 yr debt

term)

300 1,294,395 41 355,167 13,384 206,287 145,221 45,106 161,181 100,115 1,523 105.80 65.71750 2,511,825 101 887,917 33,460 407,796 289,295 112,765 295,030 176,529 3,809 77.46 46.35

1500 4,147,617 203 1,775,835 66,920 685,037 489,363 225,531 459,506 263,832 7,617 60.32 34.643000 6,848,749 405 3,551,669 133,839 1,154,505 831,399 451,062 703,443 380,337 15,235 46.17 24.975000 9,911,375 676 5,919,449 223,065 1,700,152 1,232,560 751,770 948,382 480,790 25,391 37.35 18.94

10000 16,366,375 1351 11,838,897 446,130 2,885,202 2,113,081 1,503,540 1,381,663 609,541 50,782 27.21 12.00

MICROTURBINES

y = 574.86x‐0.337

y = 541.92x‐0.405

0

10

20

30

40

50

60

70

80

90

100

0 2,000 4,000 6,000 8,000 10,000

($/ Mg CO2eq)


Mitigation Cost ‐ Lagoon Digester, uncovered effluent Pond, Microturbine

10 yr. debt

20yr. debt Term

y = 803.31x‐0.359

y = 740.47x‐0.42

0

10

20

30

40

50

60

70

80

90

100

0 2,000 4,000 6,000 8,000 10,000

($/ Mg CO2eq

)


Mitigation Cost ‐ Tank / PF Digester, uncovered effluent Pond, Microturbine

10 yr. debt

20yr. debt Term

y = 615.07x‐0.337

R² = 0.9981

y = 560.6x‐0.398

0

10

20

30

40

50

60

70

80

90

100

0 2,000 4,000 6,000 8,000 10,000

($/ Mg CO2eq)


Mitigation Cost ‐ Lagoon Digester, COVERED effluent Pond ‐Microturbine

10 yr. debt

20yr. debt Term

y = 841.01x‐0.352

R² = 0.9984

y = 740.94x‐0.405

0

10

20

30

40

50

60

70

80

90

100

0 2,000 4,000 6,000 8,000 10,000

($/ Mg CO2eq

)


Mitigation Cost ‐ Tank/PF Digester, COVERED effluent Pond ‐Microturbines

10 yr. debt

20yr. debt Term

94

Appendix3.5MitigationCostCurveDevelopment‐Digesters–FuelCells.

Lagoon Digester, Uncovered Eff. Pond, Fuel Cell

Adult Cows

Total

Capital ($)

Energy

Capacity

(kW, 100%

cap factor)

Total Energy

(kWh/y,

100% cap

fact)

O&M

($/y)

Annual

Cost ($, 10

year loan)

Annual

Cost ($, 20

year loan)

Energy

Revenue

($/y)

Net Cost,

10 yr. loan

term ($/y)

Net Cost,

20 yr.

loan

term

Emission

reductio

n (Mg/y)

Mitigation

Cost

($/Mg ‐10

yr debt

Mitigation

Cost

($/Mg ‐20

yr debt Fuel Cell adder (+3500 $/kW)*

300 1,077,896 58 506,477 45,668 206,306 155,454 64,323 141,984 91,132 1,333 106.50 68.36 202,359750 2,246,620 145 1,266,192 93,670 428,482 322,493 160,806 267,676 161,686 3,333 80.31 48.51 505,899

1500 3,939,330 289 2,532,384 161,290 748,366 562,519 321,613 426,753 240,906 6,666 64.02 36.14 1,011,7973000 6,947,098 578 5,064,769 277,724 1,313,047 985,302 643,226 669,821 342,076 13,332 50.24 25.66 2,023,5955000 10,594,713 964 8,441,281 414,518 1,993,443 1,493,613 1,072,043 921,400 421,570 22,220 41.47 18.97 3,372,658

10000 18,891,316 1927 16,882,563 713,758 3,529,121 2,637,880 2,144,085 1,385,036 493,795 44,440 31.17 11.11 6,745,316* Which is then reflected in Total Capital

Complete mix or Plug flow digester w/UNCOVERED eff pond - Fuel Cell

Adult Cows

Total

Capital ($)

Energy

Capacity

(kW, 100%

cap factor)

Total Energy

(kWh/y,

100% cap

fact)

O&M

($/y)

Annual

Cost ($, 10

year loan)

Annual

Cost ($, 20

year loan)

Energy

Revenue

($/y)

Net Cost,

10 yr. loan

term ($/y)

Net Cost,

20 yr.

loan

term

Emission

reductio

n (Mg/y)

Mitigation

Cost

($/Mg ‐10

yr debt

Mitigation

Cost

($/Mg ‐20


300 1,374,079 65 569,786 50,086 254,864 190,039 72,363 182,502 117,676 1,452 125.71 81.06 227,654750 2,796,811 163 1,424,466 102,731 519,539 387,593 180,907 338,631 206,685 3,629 93.30 56.95 569,136

1500 4,820,398 325 2,848,932 176,893 895,274 667,861 361,814 533,460 306,047 7,259 73.49 42.16 1,138,2723000 8,362,733 650 5,697,865 304,591 1,550,885 1,156,354 723,629 827,256 432,725 14,517 56.98 29.81 2,276,5445000 12,608,498 1084 9,496,442 454,618 2,333,656 1,738,822 1,206,048 1,127,608 532,774 24,196 46.60 22.02 3,794,240

10000 22,157,573 2168 18,992,883 782,807 4,084,939 3,039,605 2,412,096 1,672,842 627,508 48,391 34.57 12.97 7,588,481

Covered Lagoon Digester w/ COVERED EFF. Pond - Fuel Cell

Adult Cows

Total

Capital ($)

Energy

Capacity

(kW, 100%

cap factor)

Total Energy

(kWh/y,

100% cap

fact)

O&M

($/y)

Annual

Cost ($, 10

year loan)

Annual

Cost ($, 20

year loan)

Energy

Revenue

($/y)

Net Cost,

10 yr. loan

term ($/y)

Net Cost,

20 yr.

loan

term

Emission

reductio

n (Mg/y)

Mitigation

Cost

($/Mg ‐10

yr debt

Mitigation

Cost

($/Mg ‐20


300 1,243,573 63 550,794 48,772 234,101 175,433 69,951 164,151 105,482 1,472 111.49 71.65 220,066750 2,575,036 157 1,376,984 100,037 483,793 362,310 174,877 308,916 187,433 3,681 83.93 50.92 550,165

1500 4,493,353 314 2,753,968 172,253 841,895 629,911 349,754 492,141 280,157 7,361 66.85 38.06 1,100,3303000 7,886,723 629 5,507,936 296,602 1,471,957 1,099,883 699,508 772,449 400,375 14,723 52.47 27.19 2,200,6595000 11,986,938 1048 9,179,894 442,694 2,229,102 1,663,591 1,165,846 1,063,255 497,744 24,538 43.33 20.28 3,667,766

10000 21,278,814 2096 18,359,787 762,275 3,933,446 2,929,569 2,331,693 1,601,753 597,876 49,076 32.64 12.18 7,335,531

Complete mix / Plug flow w/ COVERED EFF. Pond - Fuel Cell

Adult Cows

Total

Capital ($)

Energy

Capacity

(kW, 100%

cap factor)

Total Energy

(kWh/y,

100% cap

fact)

O&M

($/y)

Annual

Cost ($, 10

year loan)

Annual

Cost ($, 20

year loan)

Energy

Revenue

($/y)

Net Cost,

10 yr. loan

term ($/y)

Net Cost,

20 yr.

loan

term

Emission

reductio

n (Mg/y)

Mitigation

Cost

($/Mg ‐10

yr debt

Mitigation

Cost

($/Mg ‐20


300 1,530,902 68 591,945 51,607 279,756 207,533 75,177 204,579 132,356 1,523 134.28 86.88 236,508750 3,103,094 169 1,479,862 105,850 568,303 421,907 187,942 380,361 233,965 3,809 99.87 61.43 591,269

1500 5,330,155 338 2,959,724 182,264 976,614 725,152 375,885 600,729 349,267 7,617 78.86 45.85 1,182,5383000 9,213,826 676 5,919,449 313,840 1,686,971 1,252,288 751,770 935,201 500,518 15,235 61.39 32.85 2,365,0775000 13,853,169 1126 9,865,748 468,422 2,532,953 1,879,398 1,252,950 1,280,003 626,448 25,391 50.41 24.67 3,941,794

10000 24,249,963 2252 19,731,495 806,575 4,420,535 3,276,487 2,505,900 1,914,635 770,587 50,782 37.70 15.17 7,883,588

FUELCELLS

y = 800.28x‐0.349

y = 1362.2x‐0.507

y = 800.28x‐0.349

R² = 0.9967

y = 1362.2x‐0.507

0

10

20

30

40

50

60

70

80

90

100

110

120

0 2,000 4,000 6,000 8,000 10,000

($/ Mg CO2eq)


Mitigation Cost ‐ Lagoon Digester, uncovered effluent Pond, Fuel Cell

10 yr. debt

20yr. debt Term

y = 1045.1x‐0.366

y = 1656.3x‐0.5120

10

20

30

40

50

60

70

80

90

100

110

120

130

140

0 2,000 4,000 6,000 8,000 10,000

($/ Mg CO

2eq)


Mitigation Cost ‐ Complete Mix /PF, uncovered effluent Pond, Fuel Cell

10 yr. debt

20yr. debt Term

y = 836.73x‐0.349

y = 1325.8x‐0.4960

10

20

30

40

50

60

70

80

90

100

110

120

130

0 2,000 4,000 6,000 8,000 10,000

($/ Mg CO

2eq)


Mitigation Cost ‐ Lagoon Digester, COVERED effluent Pond, Fuel Cell

10 yr. debt

20yr. debt Term

y = 1077.8x‐0.361

y = 1536.4x‐0.4890

30

60

90

120

150

0 2,000 4,000 6,000 8,000 10,000

($/ Mg CO2eq)


Mitigation Cost ‐ Complete Mix /PF, COVERED effluent Pond, Fuel Cell

10 yr. debt

20yr. debt Term

95

Appendix3.6MitigationCostCurveDevelopment‐Digesters–RNGwithFuelingStation.

Lagoon Digester, Uncovered Eff. Pond - CNG

Adult Cows

Digester

Capital ($)

Minus

Engine

Equip.

Capital ($)

Upgrading &

fueling

Capital ($)

Total

Capital ($)

Diesel

Equivalent

(gals/day)

Diesel eq.

(gallons/y)

O&M

($/y)

Annual

Cost ($, 10

year loan)

Annual

Cost ($, 20

year loan)

Energy

Revenue

($/y)

Net Cost,

10 yr. loan

term ($/y)

Net Cost,

20 yr. loan

term ($/y)

Emission

reductio

n (Mg/y)

Mit. Cost

($/Mg ‐10

yr debt

term)

Mit. Cost

($/Mg ‐20

yr debt

term)300 875,536 -166,488 677,613 1,386,661 46.5 16,955 33,473 240,126 174,707 50,864 189,262 123,843 1,333 142 93750 1,740,721 -271,570 972,410 2,441,561 116 42,387 60,119 423,984 308,798 127,161 296,823 181,636 3,333 89 54

1500 2,927,532 -393,217 1,277,955 3,812,271 232 84,774 93,627 661,768 481,915 254,322 407,445 227,593 6,666 61 343000 4,923,503 -569,354 1,679,506 6,033,655 465 169,548 145,811 1,045,003 760,352 508,645 536,358 251,707 13,332 40 195000 7,222,055 -747,910 2,054,160 8,528,305 774 282,580 202,103 1,473,072 1,070,730 847,741 625,330 222,988 22,220 28 10

10000 12,146,000 -1,082,928 2,699,606 13,762,678 1548 565,161 314,747 2,365,792 1,716,506 1,695,483 670,309 21,023 44,440 15 0

Complete mix or Plug flow digester w/UNCOVERED eff pond - CNG

Adult Cows

Digester

Capital ($)

Minus

Engine

Equip.

Capital ($)

Upgrading &

fueling

Capital ($)

Total

Capital ($)

Diesel

Equivalent

(gals/day)

Diesel eq.

(gallons/y)

O&M

($/y)

Annual

Cost ($, 10

year loan)

Annual

Cost ($, 20

year loan)

Energy

Revenue

($/y)

Net Cost,

10 yr. loan

term ($/y)

Net Cost,

20 yr. loan

term ($/y)

Emission

reductio

n (Mg/y)

Mit. Cost

($/Mg ‐10

yr debt

term)

Mit. Cost

($/Mg ‐20

yr debt

term)300 1,146,424 -177,295 709,816 1,678,945 52.3 19,074 36,090 286,302 207,094 57,223 229,079 149,871 1,452 158 103750 2,227,675 -289,200 1,018,624 2,957,100 131 47,685 64,819 505,514 366,006 143,056 362,458 222,950 3,629 100 61

1500 3,682,126 -418,743 1,338,690 4,602,072 261 95,371 100,947 786,791 569,678 286,113 500,679 283,565 7,259 69 393000 6,086,188 -606,314 1,759,324 7,239,199 523 190,742 157,210 1,236,064 894,539 572,226 663,839 322,313 14,517 46 225000 8,814,258 -796,462 2,151,784 10,169,580 871 317,903 217,904 1,733,471 1,253,698 953,709 779,762 299,989 24,196 32 12

10000 14,569,092 -1,153,227 2,827,904 16,243,769 1742 635,806 339,354 2,760,154 1,993,818 1,907,418 852,736 86,399 48,391 18 2

Covered Lagoon Digester w/ COVERED EFF. Pond - CNG

Adult Cows

Digester

Capital ($)

Minus

Engine

Equip.

Capital ($)

Upgrading &

fueling

Capital ($)

Total

Capital ($)

Diesel

Equivalent

(gals/day)

Diesel eq.

(gallons/y)

O&M

($/y)

Annual

Cost ($, 10

year loan)

Annual

Cost ($, 20

year loan)

Energy

Revenue

($/y)

Net Cost,

10 yr. loan

term ($/y)

Net Cost,

20 yr. loan

term ($/y)

Emission

reductio

n (Mg/y)

Mit. Cost

($/Mg ‐10

yr debt

term)

Mit. Cost

($/Mg ‐20

yr debt

term)300 1,023,507 -174,115 700,393 1,549,785 50.5 18,438 35,316 266,280 193,165 55,315 210,965 137,850 1,472 143 94750 2,024,871 -284,011 1,005,102 2,745,962 126 46,096 63,430 472,659 343,112 138,288 334,371 204,824 3,681 91 56

1500 3,393,023 -411,231 1,320,918 4,302,711 253 92,192 98,783 740,014 537,024 276,576 463,438 260,448 7,361 63 353000 5,686,064 -595,436 1,735,969 6,826,597 505 184,384 153,841 1,171,205 849,145 553,151 618,054 295,993 14,723 42 205000 8,319,172 -782,173 2,123,219 9,660,218 842 307,306 213,233 1,652,891 1,197,148 921,919 730,972 275,229 24,538 30 11

10000 13,943,283 -1,132,538 2,790,364 15,601,109 1684 614,613 332,080 2,657,106 1,921,088 1,843,838 813,268 77,250 49,076 17 2

Complete mix / Plug flow w/ COVERED EFF. Pond - CNG

Adult Cows

Digester

Capital ($)

Minus

Engine

Equip.

Capital ($)

Upgrading &

fueling

Capital ($)

Total

Capital ($)

Diesel

Equivalent

(gals/day)

Diesel eq.

(gallons/y)

O&M

($/y)

Annual

Cost ($, 10

year loan)

Annual

Cost ($, 20

year loan)

Energy

Revenue

($/y)

Net Cost,

10 yr. loan

term ($/y)

Net Cost,

20 yr. loan

term ($/y)

Emission

reductio

n (Mg/y)

Mit. Cost

($/Mg ‐10

yr debt

term)

Mit. Cost

($/Mg ‐20

yr debt

term)300 1,294,395 -180,945 720,572 1,834,022 54.3 19,816 36,980 310,304 223,779 59,448 250,856 164,332 1,523 165 108750 2,511,825 -295,152 1,034,059 3,250,733 136 49,540 66,419 550,874 397,514 148,620 402,255 248,894 3,809 106 65

1500 4,147,617 -427,362 1,358,975 5,079,230 271 99,080 103,438 860,393 620,769 297,239 563,154 323,530 7,617 74 423000 6,848,749 -618,793 1,785,983 8,015,940 543 198,160 161,091 1,355,702 977,532 594,479 761,223 383,053 15,235 50 255000 9,911,375 -812,854 2,184,390 11,282,910 905 330,266 223,282 1,904,768 1,372,471 990,798 913,971 381,673 25,391 36 15

10000 16,366,375 -1,176,963 2,870,756 18,060,168 1810 660,532 347,730 3,039,227 2,187,198 1,981,596 1,057,632 205,602 50,782 21 4

CNG - BIOGAS UPGRADING & FUELING STATION

y = 5540.6x‐0.626

R² = 0.9866

y = 318708x‐1.311

R² = 0.79390

25

50

75

100

125

150

175

200

0 2,000 4,000 6,000 8,000 10,000

($/ Mg CO2eq)


Mitigation Cost ‐ Lagoon Digester, uncovered effluent Pond ‐ CNG

10 yr.

20yr. debt Term

y = 5693.2x‐0.613

R² = 0.9873

y = 63990x‐1.053

R² = 0.87680

25

50

75

100

125

150

175

200

0 2,000 4,000 6,000 8,000 10,000

($/ Mg CO2eq

)


Mitigation Cost ‐ Tank/ PF Digester uncovered eff Pond ‐ CNG

10 yr. debt Term

20yr. debt Term

y = 4875.3x‐0.604

R² = 0.9885

y = 60319x‐1.059

R² = 0.87460

20

40

60

80

100

120

140

160

180

0 2,000 4,000 6,000 8,000 10,000

($/ Mg CO2eq)


Mitigation Cost Lagoon Digester COVERED eff Pond ‐ CNG

10 yr. debt

20yr. debt Term

y = 4849.3x‐0.58

R² = 0.9904

y = 21476x‐0.88

R² = 0.92950

25

50

75

100

125

150

175

200

0 2,000 4,000 6,000 8,000 10,000

($/ Mg CO2eq

)


Mitigation Cost Tank/PF Digester COVERED eff Pond ‐ CNG

10 yr. debt

20yr. debt Term

96

Appendix3.7.GHGModel:LagoonbasecaseandTier1Cover&Flare

Variable or Factor Units Value Notes and references

Daily VS production kg VS/day/1000 lb 11.41 CARB Livestock Protocol, Nov, 2014

Cow weight kg 680 CARB Livestock Protocol, Nov, 2014

Daily VS production (kg/cow) 7.7588 CARB Livestock Protocol, Nov, 2014

VS/cow/year (kg/y) 2832Ultimate Methane yield (Bo) m3/kg VS 0.24 CARB Livestock Protocol, Nov, 2014

Methane Conversion Factor 0.748CARB Protocol, Nov, 2014 / Documentation of California's Greenhouse Gas Inventory (8th Edition ‐ Last updated on 04‐24‐2015)

http://www.arb.ca.gov/cc/inventory/doc/docs3/3a2ai_manuremanagement_anaerobiclagoon_livestockpopulation_dairycows

ch4 2013.htmMethane emission potential yield m3/kg VS 0.180

Global warming potential of methane kg[CO2]/kg[CH4] 25 CARB Livestock Protocol, Nov, 2014

Methane density kg/m3 0.662

(m^3/cow/y) 508.39

ft^3/cow/day 49.19

kg/cow/y 336.56

Mg CO2e/y/cow 8.41

N2O emissions (100% manure to lagoon) (Mg CO2e/y/cow) 0.322

Documentation of California's Greenhouse Gas Inventory (8th Edition ‐ Last updated on 04‐24‐2015)

http://www.arb.ca.gov/cc/inventory/doc/docs3/3a2ai_manuremanagement_anaerobiclagoon_livestockpopulation_dairycows

n2o 2013.htmTotal GHG Potential, Anaerobic Lagoon (Mg CO2e/y/cow) 8.736 Methane and N2O

Manure collection efficiency -portion of adult cow manure (manure destined for lagoon or digesters -

base case and project)0.6

Population seving lagoon in state inventory 1,035,710 Documentation of California's Greenhouse Gas Inventory (8th Edition - Last updated on 04-24-2015)

Lagoon Dairy Manure GHG (Mg CO2e/y) 9,047,877 Matches State Inventory

Methane: Scenario Lagoon emission

[for 60% manure to lagoon](Mg CO2e/y/cow) 5.05

N2O: Scenario Lagoon emission


Total GHG Lagoon Emission= Baseline


This is total annual baseline emission per cow from anaerobic lagoon for 60% manure collection. Represents maximum that

can be mitigated.

Covered lagoon capture efficiency 0.95 CARB Livestock Protocol, Nov, 2014

Flare destruction efficiency (combination of

open/closed flare0.995

Low-NOX flare, high desctructin efficient (SJVAPCD)

Fugitive Emission factor 0.055

Capture and destuction efficiency 0.945

Mitigated per cow per year (Mg CO2e/y/cow) 4.95 Mitigation per cow per year for COVERED LAGOON ‐to‐FLARE SCNARIO

Methane to flare (Mg CO2e/y/cow) 4.77

Gas produced (60% collection) ft^3/cow/day 29.5

Gas destroyed (60% collection) ft^3/cow/day 27.9Fugitive emission, cover and flare (60% manure) ft^3/cow/day 1.6

Biogas flows (assumes 60% methane) 49.2 http://www.arb.ca.gov/cc/inventory/doc/docs3/3a2ai_manuremanagement_anaerobiclagoon_livestockpopulation_dairycows_ch4_2013.htm

46.5 http://www.arb.ca.gov/cc/inventory/doc/docs3/3a2ai_manuremanagement_anaerobiclagoon_livestockpopulation_dairycows_n2o_2013.htm

2.7

Methane potential produced by Lagoon (100%

manure to lagoon)

Methane

Lagoon GHG Emissions Model. Base Case & Cover/Flare Project (60% adult cow manure destined to lagoon). Model is from livestock in CARB GHG Inventory.

COVERED LAGOON ‐to‐FLARE SCNARIO

97

Appendix3.8.DigesterScenarioModelandper‐cowoutputs.

Value Notes Value Notes Value Notes Value Notes Value Notes

Covered lagoon capture

efficiency0.95

Carb

Protocol0.95 0.98 0.95 0.98

Flare destruction efficiency

(combination of

open/closed flare

0.995Carb

Protocol ‐

Engine w/ aftertreatment 0.995 0.995 0.995 0.995

Capture and destuction

efficiency0.945 0.945 0.975 0.945 0.975

VS collected (kg/cow/yr) 1699

60%

manure to

device

169960% manure to

device1699

60% manure to

device1699

60% manure to

device1699

60% manure

to device

MCF (lagoon or digester) 0.748Carb

Protocol0.8

Assumes

managed w/

appropriate

retention times

and volume, and

marginally

better than

anaerobic

lagoon

0.9

Assumes managed

w/ appropriate

retention times

and volume,

possibly heated,

and marginally

better than

coveredlagoon

0.8 0.9

Methane produced in BCS

(m^3/cow/year)305.0 326.2 367.0 354.8

(includes from

covered eff.

pond

381.3

methane produced

(ft^3/day/cow)29.5 31.6 35.5 34.3 36.9

kW gas energy/cow 0.360 0.385 0.434 0.419 0.450

Recip Engine @ 30%

conversion eff (kW/cow) ‐ 0.116 0.130 0.126 0.135

MicroTurbine @ 23%

conversion eff (kW/cow) ‐ 0.089 0.100 0.096 0.104

Fuel Cell @ 50% (kW/cow) ‐ 0.193 0.217 0.210 0.225

VS to effluent pond

(kg/cow/yr)340 170 340 170

MCF (eff. pond) 0 0.35

Liquid/Slurry

system w/o

crust, 18 C

annual mean

temperature as

recommended

in protocol

0.35 0.35 0.35

Effluent pond methane

emission per cow

(m^3/cow/year)

28.5 14.3

Eff Gas Collected

(m^3/cow/year) ‐ ‐ ‐ ‐ ‐ ‐ 28.5

This gas added

to energy device14.3

Added to

energy

device

Effluent pond CH4

emissions ‐Mg CO2e/y/cow0.47 0.24 ‐

Effluent pond N2O

emissions ‐Mg CO2e/y/cow0.02 0.01

Effluent Emissions (Mg

CO2e /cow/y)0.49 0.25

Methane collected in BCS

(Mg CO2eq/cow/y) 5.05 5.40 6.07 5.87 6.31

N2O CO2eq 0.19 0.21 0.23 0.22 0.24

BCS Emission (Mg

CO2eq/cow/y) 0.29 0.31 0.16 0.33 0.16

BCS + EFFl Pond Emissions

(Mg CO2e/cow/y)0.29 0.80 0.40 0.33 0.16

Mitigation (Mg

CO2e/cow/y)4.95 4.44 4.84 4.91 5.08

DIGESTER SCENARIOS

Cover and Flare

Parameter

Covered Digester w/

UNCOVERED eff Pond

Above Ground Tank/ Plug

flow digester

w/UNCOVERED eff pond

Covered Digester w/

COVERED EFF. Pond

Above Ground Tank/

Plug flow w/

COVERED EFF. Pond

98

Appendix3.9.EffluentPondCoverCostadderfordigesterscenarios

Effluent Pond Cover Cost Estimate

Dairy

Size1

Cover& Flare Scenario

Lagoon surface

area 2

Cover&Flare

Cover Costs 3

Effluent Pond Cover

Costs 4

Effluent Pond Cover

Costs 4

Adult Cows

acres $ ($2.60/ft^2) $ $/cow

300 2.1 237,838 158,558 529750 3.4 385,070 256,714 342

1,500 6.0 679,536 453,024 3023,000 10.7 1,211,839 807,893 2695,000 14.5 1,646,069 1,097,379 21910,000 23.8 2,695,634 1,797,089 180

Modeled Assumptions1 Dairy size characterized by # of adult cows (80% lactating/20% dry animals)

2 This is the lagoon surface area from the the "Cover and flare" scenario analysis (which is based on the Provost & Pritchard Consulting Group Memo.3 $2.60 per square foot installed. Cover Costs from Environmental Fabrics, Inc. (EFI)

4

Cost Curves ‐ (Power Law Regression Fits Shown)

Assumes eff luent pond is 2/3 the size (surface area) as the cover&flare scenario lagoon. This assumes that digester capacity, plus eff luent pond is suff icient to meet facility storm run-off requirements.

y = 2548.1x0.7121

R² = 0.9954

0

200,000

400,000

600,000

800,000

1,000,000

1,200,000

1,400,000

1,600,000

1,800,000

2,000,000

0 2000 4000 6000 8000 10000 12000

Covered efflurent pond Cost estimate based on 2/3

99

Appendix3.10.FuelCellCapitalCostAdderandO&MAnalysis

Fuel Cell Installed Cost with Comparison to Recip. Engine Costs

SGIP Reported FC Costs 6

kW

Anaergia /

Tenddewic

z ($/kW)

O&M

($/kWh) d

FC maint.

Contract 7

inflation FC y = 31707x‐0.22

200 7,792 0.069 108,746

FC System Costs From Literature a

0.02 31707 500 6,393 0.057 223,048

(Tendewicz/Anaergia) y = 24473x‐0.216

‐0.22 800 5,776 0.051 322,425

2011 2015 Curve Fit 1000 5,504 0.049 384,066

Iterature Source kW $/kW kW SGIP ($/kW) 1400 5,118 0.045 500,000 Note c

Tendewicz1

330 5,784 6,261 6,993 200 9,884

Tendewicz1

1530 3,916 4,239 5,021 500 8,079 Maint. Contract as Fraction of installed cost

Tendewicz1

6140 3,584 3,879 3,719 800 7,286 0.070

Anaergia 2

1400 5,714 5,118 1000 6,937

USEPA Fact Sheet3

250 7,600 7,426 1400 6,442

Tulare 4

300 7,967 7,139

Tendewicz/Anaergia fit

Biogas Engine Costs FC SGIP Weighted Difference

A B C (B‐A) (C‐A)

y = 9392.6x‐0.174

kW $/kW $/kW $/kW

200 3,736 7,792 9,884 4,057 6,148 811,305 1,229,629

500 3,185 6,393 8,079 3,208 4,894 1,603,935 2,447,122

800 2,935 5,776 7,286 2,841 4,351 2,272,655 3,480,548

1000 2,823 5,504 6,937 2,681 4,113 2,680,804 4,113,429

1400 2,663 5,118 6,442 2,456 3,779 3,437,722 5,290,653Midpoint of Weighted

Average ($/kW) b

3,509

Notes:

a. This analysis estimates weighte average difference in capital costs between biogas fuel cell and recip. engine systems (in $/kW)

b. Will use $3500/kW as Fuel Cell Capital Adder (above Recip engine cost)

c. Maintenance Contract includes stack replacement at 5 yrs. NREL Document

d. O&M costs for digesters w/ fuel cells is ($/kWh) = 0.2166x‐0.216, where x= capacity in kW.

References:

1 Trendewicz, A. A. and R. J. Braun (2013). "Techno‐economic analysis of solid oxide fuel cell‐based combined heat and power systems for biogas utilization at wastewater treatment facilities." Journal of Power Sources 233: 380‐393.

2 (2015). RP1 FUEL CELL LLC et al v. USA. Reported Opinion, Judge Marian Blank Horn. 2013cv00552, United States Court of Federal Claims.

3 USEPA (2013). Renewable Energy Fact Sheet: Fuel Cells http://water.epa.gov/scitech/wastetech/upload/Fuel‐Cells.pdf.

4 FuelCells2000 (2011). Case Study: Fuel Cell System Turns Waste into Electricity at the Tulare Wastewater Treatment Plant., http://www.fuelcells.org/uploads/TulareCaseStudy.pdf.

5 Williams R.B. , (2015) Evaluation of Biogas utilization technologies. Unpublished Analys.

6 CPUC (2015). SGIP Weekly Projects report., https://www.selfgenca.com/documents/reports/statewide_projects.

7 Remick, R. and D. Wheeler (2010). Molten Carbonate and Phosphoric Acid Stationary Fuel Cells: Overview and Gap Analysis., NREL/TP‐560‐49072.

4,247

Curve fit engine

sheet / EPA

(Williams, 2015)5

Difference

Δ $/kW (Δ $/kW) x kW

Average

Difference

($/kW)3,048 4,657

Weighted

Average

($/kW)2,771

y = 0.2166x‐0.216

R² = 1

0.000

0.010

0.020

0.030

0.040

0.050

0.060

0.070

0.080

0 250 500 750 1000 1250 1500

O&M ($.kWh)

Capactiy (kW)

FC O&M $/kWh based on $500,000 service contract for 1400 kW system

100

Appendix3.11.RNGModelCapitalCostAdderandO&MAnalysis

Assumes 70% of methane is recovered. 30% in tail gas to flare

scfm

Biogas

Methane

(scfm)2

Methane

(scfd)

Btu/min

(LHV)gge/d gge/day gge/y gde/y Mmbut/day MMBtu/y

0.5275 1.2 50 30 43,200 27,000 344.1 0.3 12,960 240.8 83,515 73,481 30.24 11,038 14.4 71,094 1.06

1.055 1.5 100 60 86,400 54,000 688.1 0.3 25,920 481.7 167,029 146,963 60.48 22,075 9.0 117,862 0.82

2.11 2 200 120 172,800 108,000 1376.3 0.3 51,840 963.4 334,058 293,925 120.96 44,150 6.0 195,396 0.64

Interest

RateYears

No. Of

Cows4

scfm

Biogas

Total CNG

Capital

Annual

Capital

Payment5

CNG O&M

($/y)

O&M (CNG

+ Flare)$/gge $/gde $/MMBtu

0.08 10 1440 50 1,271,094 $189,430 $88,525 $91,369 $3.36 $3.82 $25.44 kW ($/kW)

2880 100 1,617,862 $241,109 $136,964 $141,678 $2.29 $2.60 $17.34 100 3,000

MJ/gal Btu (LHV)/gallon 5760 200 2,195,396 $327,179 $213,797 $221,613 $1.64 $1.87 $12.43 150 2,333

Diesel 135.5 128,429 gde Btu/gallon 190 2,237

Gasoline 120.3 113,000 gge Btu/gallon 220 2,045

450 1,444

800 1,088

1550 839

Notes and References;

1

2

3

4

5

6

7

8% APR, 10 year loan term

gge= gallons gasoline equivalent (113,000 Btu/gallon, LHV). gde = gallons diesel equivalent (128,429 Btu.gallon, LHV)

Assumes manure from 1 cow produces 30 cubic feet of methane per day. Slightly conservative for some of the digester scenarios.

Recip engine cost is subracted from digester capital cost and then CNG system is added in the scenario cost calculation. Costs are from 2gCenergy, equipment only, not installed.

Recip Engine

equipment costs‐

curve is developed 7

Based on BioCNG project sheets, conference presentations and Geosyntec report to Flagstaff Landfill. BioCNG uses a membrane seperation technology for CO2/CH4 separation and employees a single

pass through system to keep capital costs low. They report about 70% of incoming methane is upgraded to fuel with the remaining 30% remaining with the CO2 tail gas. This gas must be disposed of,

not vented , and can possibly be burned in an engine. This analysis assumes it is burned in a flare. Flagstaff Document: http://www.flagstaff.az.gov/DocumentCenter/View/43252.

Tailgas (methane slip) is flared in this scenario. Added flare capital and operating costs using data from "cover and flare" costs ‐ scaled to tail gas flow. Nox emissions are 0.025 lb/Mmbtu as in cover

and flare scenario

Assumes 60% methane in biogas

MW

CH4

Capital

Cost

(mil lion $) 1

$/GPY

annual

capacity

Flare

Cost 3

O$M CNG

only ($/gge) 1

OUTPUTMethane

slip

(fraction)1

Methane to

flare (sdfd)3

INPUT

y = 71532x0.3942

0

500,000

1,000,000

1,500,000

2,000,000

2,500,000

0 1,000 2,000 3,000 4,000 5,000 6,000 7,000

Fuel station, Cap Cost $ vs. Cows

y = 874.1x0.6391

R² = 1

$0

$50,000

$100,000

$150,000

$200,000

$250,000

0 1,000 2,000 3,000 4,000 5,000 6,000 7,000

Fuel station, O&M$ vs. Cows

y = 25056x‐0.466

R² = 0.9967

0

1,000

2,000

3,000

4,000

0 500 1,000 1,500 2,000

Biogas Engine Package Costs ‐ Equipment Only (2gCenergy) ($/kW vs KW)

101

Appendix4.1:Convertingfromflushtoscape:SupportinginformationThegoalofthismodelwastoestimatetheannualexpectedcoststobeincurredbydairiesinCAbyswitchingaportionofmanurefromflushtoscrapemanuremanagementsystems.Californiadairiesrangefromsmalltolargesizedoperationssovaluesof300–10,000head(milkinganddry)wereinvestigated.Thetypesofscrapingsystemsinvestigatedwere:vacuumtruck,front(rubber)mountedscrapers,andautomatedmechanicalscrapersystems.Thefirstassumptionwastoassumefreestallbarnlengthas500ft,withaboutonecow/ftofbarnwithfourlanesperbarn,resultinginabout125cowshousedineachlane.Therefore,fora1,500cowoperation,twelvelanes,orthreetypicalbarnswouldberequiredatatypicaldairy.Thiswasconsistentwithavisittoa1,500headdairy.Usingthisinformation,thenumberof500ftlanesrequiredforeachoperationwasdeterminedbyproportionalscalingbasedonthe1,500headcase.ThemanureproductionrateofthecowswasalsodeterminedfromASABEStandardD384.2forlactatingcows.VacuumTruckScenarioThevacuumtruckscenarioisbasedoncostquotessuppliedbyARBforasinglerepresentativevendorofferingthreevacuumtruckmodelswithvaryingcapacitiesandupfrontsalesprice.Themanureloadingcapacitiesrangefrom2,200to4,300gallonsbuteachhave60gallonfueltanksandaveragefueleconomyofabout2gph.Foreachofthesetucks,costswereestimatedbyestimatingthetotaldistancetraveledbythetrucksdownthescrapedlanesaswellastoanunloadlocation.Thedistancetravelleddownthelanesisdeterminedbasedonthelinearrelationshipdetailedearlierwith500ftlanesassumed.Adistancetravelledtomanureunloadlocationwasestimatedusingaradiallyincreasingdistancewithincreasingdairysizeasopposedtoalinearlyincreasingdistancesinceitislikelythatmultipledropofflocationsmayexistatlargerdairies,meaningthatlinearincreasesmayoverestimatetraveldistance.Thesecalculationsbeginat200ftfora300headdairyandincreaseaccordingtotheformula

∗

whererAandrBrefertotheradiiofthereferencecaseandcalculatedcase,respectivelyandCap(A)andCap(B)refertothedairyherdsizeofthereferencecaseandcalculatedcase,respectively.Duetotheirsizeandforthesafetyoftheanimals,vacuumtruckoperationrequiresthatthelanesbeemptyofanimalsduringscraping.Vacuumingtypicallyoccurswhenthecowsarebeingmilkedintheparlor,whichoccursatamaximumof3timesperday.Thevolumeofmanurepercleanoutiscalculatedanddividedbythetruckvolumetodeterminethenumberoftripstoadropofflocation.Valuesrangedfrom2to35tripsperdaydependingonthetruckcapacity.Employeelaborwasaccountedforonlyfortimespentphysicallyoperatingthemachine,whichiscalculatedfromthedistancetraveledby:

102

#

∗#

∗ 2 ∗ ∗

Thisrelationshipsimplytakesintoaccountthedistancetraveleddownthelanesandthenaddsatriptoandfromanunloadinglocationdeterminedpreviously.Thetrucksinvestigatedinthismodeltravelveryslowlydownthelanesbuthavetheabilitytotravelupto25mph.Anaverageconservativetruckspeedwasdeterminedusingthisinformationtoaverageabout6.7mph.Theemployeepayratewasassumedat$20/hour.Atotaloperationcost/daywasthendeterminedbyaddingtheemployeecoststoacalculatedfuelconsumptioncostusingthetotaldistancetraveledperday(thenumeratorofEq.2)andtheaverageCAdieselfuelcostof$3.812/gal(EIA,onJuly27,2015).Thetotalcostofthesystemisthereforethesumoftheoperationalandupfrontcostswithupfrontcostsdistributedover10and20yearloanpaybackperiodswith8%interestrates.Thegreenhousegasemissionsassociatedwithasystemofthistypearethencalculatedusinga10.448kgCO2eq/galofdieselfuel(CARB,2014).Itisimportanttonotethatthecostestimatesfromthismodeldonotassumeanychangestoexistingdairies.Truckscanbeveryheavywithfullyloadedweightsexceeding60,000lbforthelargesttruck.Itisexpectedthatdairies,especiallyolderones,consideringthisstrategymayrequireavarietyofmodificationstobarnssuchasthickerand/orreinforcedconcreteandtheremovalofanyobstaclethatmaybepresentinthelengthofthelanes.However,nodatawasfoundforthesetypesofmodificationcostsandarenotincludedinthemodel.Additionally,themodelassumesonevacuumtruckwillbepurchasedforanygivenfarmsize.Althoughbasedonthemodel’scalculations,thismaybepossible,itisanunlikelyscenariosincefarmsmayusemorethanoneatatimeandmaypurchaseonormorebackuptrucksdependingontheirneeds.Sincethesalepriceofthevacuumtrucksistheoveralldriverofthetotalsystemcostsinthisscenario,thesensitivityofthemodeltothisexpenseisremarkableespeciallyforsmalldairies,withtheoverallrelativecostsincreasingbyabout70%for300headdairiesthatdecidetopurchasetwoofthesmallesttrucks.ChainorCableAutomatedMechanicalScraperScenarioTheautomatedmechanicalscraperscenarioswerebasedonaquotefromarepresentativevendorandwerecorrelatedwithcostestimatesofa1,500headdairythatsuccessfullyimplementedanautomatedmechanicalsystem.Thequotedsystemsfromthevendorwereforapproximatelysimilarlysizeddairies(around1,500head)andincludedupfrontsalepricesforvariouspiecesofequipmentforacableandascrapersystem.Thecostestimatesfromthedairyincludedinformationontotalinstalledcostsincludingshipping,labor,andrequiredbarnmodificationandinfrastructureconstructioncosts.Themechanicalaspectsoftheautomatedsystemsquotedfromthevendorweresignificantlycheaperthanthereportedcostfromtheretrofitteddairy($46,000‐$56,000versusover$150,000).Someofthisvariationisduetodifferencesinvendorsbutalsomaybeduetodifferencesspecificityofthequoteforactualon‐farmconditions.Bothofthequoteswereforsingular,long(1,200–1,350ft)barnsthatmadeuseofoneortwoindependentmechanicalsystemswithinthebarn.The1,500headdairywasdifferentfromthose

103

inthatitrequiredthreeseparatesystemsforthree500ftbarns.Thediscrepancybetweenthequotedpricescanatleastbepartlydescribedbythisdifferenceandunderlinesthepossibilityforsignificantlydifferentpricelevelsdependingonindividualfarmdesignsandconditions.Theestimatedinstalledcostforcollectionpitconstructionandconcreteworkwereestimatedatabout$180,000fromthedairyandinthisspecificcase,andadditionalrubbermattingwasaddedtothebarnfloorforabout$58,000.Aninstallationadderof25%wasappliedbasedoncomponentsnotalreadyquotedwithinstallationcosts(mechanicalandmatting).Thedairyinstallationincludedanoverseasshippingchargeofabout$35,000whichwouldnotbeincurredfromUSvendors,whichmighthaveonly$2,500forexamplefreightcharges.Ultimately,forthepurposesofthemodel,atotalinstalledcostof$300,000includingmechanicalscrapersystemprice,miscellaneousequipmentandinfrastructurecosts,andinstallationlaborwasassumedrequiredfora1,500headdairy.The$300,000totalinstalledcostestimatewasthenscaledwithdairysizeusinganexponentialscalingfactorof0.675accordingtotheformula:

∗

whereCaandCbrelatetothetotalinstalledcostofthereferenceandcalculatedsystems,respectivelyandxisascalingfactor.Theexponentialscalingfactorisincludedinanattempttodescribethedecreasingnatureoftheeffectofeconomyofscale.Thescalingfactorxisnormallyfoundbycomparingthecostsoftwoormoredifferentsizedsystemsandusuallyvariesbetween0.5and0.85(Dysert,2005).

Themodelassumesa2hpmotorisusedtodrivethescrapersdownthelanesatarateof4m/min.Usingthisinformationandanassumedlanelengthof500ft,theenergyrequiredpertripcanbeeasilycalculatedandscaledbytheaveragepriceofelectricityinCAof$0.1484/kWh(EIA,2015)toyieldatotalcostofelectricityrequiredforthesystempertrip.Thecostpertripisthenscaledbythenumberofassumedlanesscrapedatagivenfarmsize(12fora1,500headdairy)andthenmultipliedby2forthefactthatthescrapermustgoupanddowneachlanepertrip.Basedonaconversationwiththe1,500headdairythatsuccessfullyimplementedthissystem,atotalof6scrapetripsperdayupanddownthelaneswasassumedasareasonablevalue.Inexplicitterms,theoperationalelectricitycostswerecalculatedusingtherelationship:

∗

∗

∗ # ∗ ∗

Totalsystemcostswerethencalculatedusingthetotalinstalledcostsdistributedover10and20yearloanperiodswithan8%interestrate.ThegreenhousegasemissionsduetoelectricaloperationwerecalculatedsimplyfromtheenergyusedfortheelectricalmotorandtheaverageemissionsofelectricalgenerationinCAof0.277kgCO2eq/kWh(CARB,2014).Thereareafewnotablelimitationsofthismodel.Firstly,thedifferenceinthemodelforthetwotypesofsystems(cableorchain)isonlyduetodifferentialinquotedsaleprice.Inreality,therearelikelyotherfactorsandcoststhatwillfurtherimpacttotalsystemcostssuchasdifferencesincomponentlifetimeandtheassociated

104

replacementcosts.Additionally,furtherresolutionontheconstructionrequirementsforexistingdairiesofdifferingsizeswouldgreatlyimprovetherobustnessofthemodelbyallowingabetterestimationofneedsandanunderstandingofhowthesecostsmaybeimpactedbyoperationtypeandsize.FrontMountedScraperScenarioThefrontmountedscraperscenariotakesintoaccountthemedianpriceofthreemodelsofrubber‐mountedscrapersfromaquotetoCARBfromarepresentativevendor.Thisscenarioincludesaspectsofboththevacuumtruckandautomatedscraperscenariosandassuch,manyofthecalculationsforthisscenarioareidenticaltothosediscussedearlier.Includedinthemodelisthecostofamedium‐sized23.5hpBobcatskid‐steerloaderestimatedat$18,000.Themaximumratedspeedforthisvehicleis6mphandanaverageassumedspeedof5mphwasusedinthemodel.Theassumedaveragefueleconomyoftheskid‐steerloaderis1.387gph.Aswiththevacuumtruckmodel,thefrontmountedscrapervehicleonlyhasaccesstothelanesamaximumof3timesperdaywhenthecowsareatthemilkingparlor.Itisalsosimilarlyassumedthatthecowsspend20hoursperdayinthefreestalllanesandthevolumeofmanureproducedistheevenlydistributedbetweencleanouts.Thefuelconsumptioniscalculatedidenticallytothevacuumtruckexceptthattripstoandfromadropofflocationarenolongerneeded,meaningthatthefuelconsumptionisbasedsolelyonthefueleconomy,averagespeed,andtotaltravelledlengthperday.Unlikethevacuumtruckscenario,theconstructionofconcretetrenchesandholdingtanksislikelyrequiredandwasmodeledusingtheconcreteconstructioncostsfromthe1,500headdairyexamplefortheautomatedscrapersystemsasthebasecase.Laborcostswereestimatedasa25%adderbasedontheconcreteworkcostsandscaledusingthe0.675scalingfactorinthesamewayasfortheautomatedsystems.Additionally,employeecostswerecalculatedinanidenticalwayasdescribedforthevacuumtrucksexceptthatthetotaldistanceandthustimeworkedareshorterinthesecasesbecausetheskidderisnotmodeledastravellingtoanunloadinglocation.Thetotalinstalledcostinthisscenariothereforeisthesumoftherubberscrapersaleprice,skid‐steerloadersaleprice,andconcreteconstructionandlaborcosts.Totalsystemcostswerecalculatedidenticallytotheotherscenariosandmodeledover10and20yearloanperiodswithan8%interestrate.Greenhousegasemissionswerecalculatedbasedonthedieselconsumptionandemissionratesasdiscussedforthevacuumscraperscenario.Thisestimatehassomelimitations.Forthesamereasonsdiscussedwiththeautomatedscrapingsystems,betterresolutionintotheconstructionandassociatedcostsandknowledgeintohowtheychangedependingondairysizewouldbehelpful.Improvementmaybegainedfromincludingothervendorquotes,althoughthepriceoftherubberscraperitselfplaysaverysmallroleintheoveralleconomicsoftheproject.Themodelcurrentlyassumesoneskid‐steerloaderispurchasedanddoesallofthescrapingregardlessoffarmsize.Abetterunderstandingofhowfarmersdecidehowmanyandwhattypeofskid‐steerloadertopurchasewouldgreatlybenefittheeconomicmodel.Unlikethevacuumtruckscenario,therubbermountedscraperscenarioismoredominatedbycapitalcostsbecauseoftherelativelylowpriceoftheskid‐steerloadersthemselves.

105

Appendix4.2:Scrapetoopensolardrying(6mo.)scenariocostdevelopmenttable

APPENDIX Mitigation Cost‐Curve Development Tables Scrape to Open Solar Drying (6 mo.)

Dairy Size1

Scraping Average Captial

Cost3

Scraping Average

O&M

Cost4

Scraping Average

Emissions5

Evap Pad Average

Area6

Evap Pad Average

Cost7

Evap Equipment

Average

Costs8

Evap Land Lease

Average

Cost9

Evap Bulking Materials

Average Cost

Evap O&M, Labor, Utilities,

Average

Costs10

Evap Average

Emissions11

Total Average Capital

Cost12

Total O&M Average

Cost13

Total Annualized Average Cost per

head14

Total Annualized Average Cost

per head15

Net Average Emissions

Reductions16

Average Emissions

Reduction Cost17

Average Emissions Reduction

Cost18

Adult Cows2 $ $/yr MgCO2e/y acres $ $ $/yr $/yr $/yr MgCO2e/yr $ $/yr$/head/yr - 10 yr

term$/head/yr - 20 yr

termMgCO2e/yr

$/MgCO2e - 10 yr term


300 $129,412 $825 0 0.4 $65,660 $214,348 $1,292 $0 $3,390 5 $409,421 $5,508 $222 $157 403 $165 $117

750 $168,947 $2,089 1 0.9 $138,005 $214,348 $2,716 $0 $9,375 15 $521,300 $14,180 $122 $90 1,007 $91 $67

1,500 $220,083 $4,195 2 1.9 $284,060 $214,348 $5,590 $0 $18,750 29 $718,491 $28,535 $90 $68 2,013 $67 $51

3,000 $301,727 $8,491 5 3.8 $577,535 $214,348 $11,364 $0 $37,501 59 $1,093,610 $57,356 $73 $56 4,027 $55 $42

5,000 $391,685 $14,303 8 6.3 $961,100 $214,348 $18,912 $0 $62,501 98 $1,567,133 $95,715 $66 $51 6,711 $49 $38

10,000 $575,705 $29,311 17 12.6 $1,920,695 $214,348 $37,794 $0 $125,002 196 $2,710,748 $192,107 $60 $47 13,422 $44 $35

Modeled Assumptions1Dairy size characterized by # of adult cows (80% lactating/20% dry animals)

258.2% of adult cow manure assumed destined for anaerobic lagoon per ARB 2012 Statewide GHG Inventory

A. 15% assumed flushed through milk barns, leaving 43.2% available for diversion by scraping

3Full scraping capital cost used for full or partial year operation

4O&M cost scaled proportionally from annual estimate for number of months operated

5Direct emissions for scraping scaled proportinally from annual estimate for number of months operated

6Evaporation pad average area calculation assumes the following

Raw manure total solids = 13%

Final dried manure total solids = 70%

Monthly net evaporation (pan evaporation ‐ precipitation) for design month = 4.95" (April ‐ Fresno)B

6 month operation design from April ‐ September

Pad area = Volume of water required to be evaporated (ac‐ft) / average monthly evaporation (ft) for design month

Assumes runoff collection pond and area required for composting opearations can utlize existing dairy storage pond, no new leachate detention pond7Evaporation pad cost assumes reinforced concrete installed cost at $3.50/ft

2.C

8Evaporation equipment cost assumes baseline cost for 135hp front end loader with 3 yard bucket, as estimated in CoComposter v2a model

Dadjusted to 2015 pricing with 2.5%/yr inflation rate

E

9Land lease/rent assumes $250/acre

F

10O&M labor, utilities and associated costs etimated using CoComposter v2a model with the following inputs, other assumptions default

Management system compost windrows turned with bucket loader (8' height x 16' width)

7 day turning frequency, 30 day compost period, 0 day curing, 0 day fresh materials, and 0 day final storage period assumed

$20/hr labor cost

$0.148/kwh electricity cost G

No compost screening cost11Average direct emissions from processing scaled from annual estimates of diesel and electricity usage with CoComposter V2a

D, scaled proportionally for number of months operated, with

Diesel emissions = 10.45 kg CO2‐equivalent/gallon H

Electricity emissions = 0.277 kg CO2‐equivalent/kWh H

12Sum of pad and equipment capital costs

13Sum of land lease, bulking, and O&M costs

148% interest rate, 10‐year term for capital loan, plus annual O&M, divided by number of adult cows


16For manure diverted to solar drying, MCF and N2O emission factors for Liquid/Slurry management

A are assigned for 50%, and Solid Storage

A for the remaining 50%, of months opearated

17Total 10‐year annualized cost per head, multiplied by dairy size, divided by average GHG emissions reduction per dairy size.


References:Ahttp://www.arb.ca.gov/cc/inventory/doc/docs3/3a2ai_manuremanagement_anaerobiclagoon_livestockpopulation_dairycows_ch4_2012.htm Cost Curves ‐ (Power Law Regression Fits Shown)

Bhttp://www.water.ca.gov/landwateruse/annualdata/agroclimatic/

http://www.water.ca.gov/floodmgmt/hafoo/hb/sss/precipitationChttps://www.boe.ca.gov/proptaxes/pdf/ah53415.pdf

Dhttp://compost.css.cornell.edu/CoCompost.html

Ehttp://data.bls.gov/cgi‐bin/cpicalc.pl

Fhttp://www.calasfmra.com/db_trends/2013Trends.pdf

Ghttp://www.eia.gov/electricity/monthly/epm_table_grapher.cfm?t=epmt_5_6_a

Hhttp://www.arb.ca.gov/regact/2014/capandtrade14/ctlivestockprotocol.pdf

y = 1535.2x‐0.369

R² = 0.9303

y = 924.62x‐0.339

R² = 0.9231$0

$50

$100

$150

$200

$250

0 5000 10000 15000

Total A

nnualized

Average

Cost

($/hd/yr)

Dairy Size (Adult cows)

Annualized System Cost

10‐year term

20‐year term y = 1140.5x‐0.368

R² = 0.9306

y = 686.9x‐0.339

R² = 0.9234$0

$20

$40

$60

$80

$100

$120

$140

$160

$180

0 5000 10000 15000Total A

nnual G

HG Mitigatio

n Co

st

($/M

gCO2e)


Annualized Mitigation Cost

10‐yr term

20‐year term

106

Appendix4.3:Scrapetoopensolardrying(8mo.)scenariocostdevelopmenttable

APPENDIX Mitigation Cost‐Curve Development Tables Scrape to Open Solar Drying (8 mo.)

Dairy Size1


Cost3

Scraping Average

O&M

Cost4

Scraping Average

Emissions5

Evap Pad Average

Area6

Evap Pad Average

Cost7

Evap Equipment

Average

Costs8

Evap Land Lease

Average

Cost9

Evap Bulking Materials

Average Cost

Evap O&M, Labor, Utilities,

Average

Costs10

Evap Average

Emissions11


Cost12

Total O&M Average

Cost13


head14


per head15


Reductions16

Average Emissions

Reduction Cost17


Cost18



termMgCO2e/yr



300 $129,412 $1,101 1 0.9 $142,100 $214,348 $2,796 $0 $5,000 8 $485,861 $8,897 $271 $195 534 $152 $109

750 $168,947 $2,787 2 2.2 $329,105 $214,348 $6,476 $0 $12,500 20 $712,400 $21,763 $171 $126 1,336 $96 $71

1,500 $220,083 $5,597 3 4.5 $685,370 $214,348 $13,486 $0 $25,000 39 $1,119,801 $44,083 $141 $105 2,671 $79 $59

3,000 $301,727 $11,327 6 9.0 $1,370,600 $214,348 $26,970 $0 $50,001 78 $1,886,675 $88,298 $123 $93 5,343 $69 $52

5,000 $391,685 $19,080 11 14.9 $2,270,135 $214,348 $44,670 $0 $83,335 131 $2,876,168 $147,084 $115 $88 8,904 $65 $49

10,000 $575,705 $39,101 23 29.9 $4,557,875 $214,348 $89,687 $0 $166,670 262 $5,347,928 $295,457 $109 $84 17,807 $61 $47







6Evaporation pad average area calculation assumes the following



Monthly net evaporation (pan evaporation ‐ precipitation) for design month = 2.05" (March ‐ Fresno)B

8 month operation design from March‐October

Pad area = Volume of water required to be evaporated (ac‐ft) / average monthly evaporation (ft) for design month

Assumes runoff collection pond and area required for composting opearations can utlize existing dairy storage pond, no new leachate detention pond7Evaporation pad cost assumes reinforced concrete installed cost at $3.50/ft

2 .C

8Evaporation equipment cost assumes baseline cost for 135hp front end loader with 3 yard bucket, as estimated in CoComposter v2a model

Dadjusted to 2015 pricing with 2.5%/yr inflation rate

E


F

10O&M labor, utilities and associated costs etimated using CoComposter v2a model with the following inputs, other assumptions default

Management system compost windrows turned with bucket loader (8' height x 16' width)


$20/hr labor cost



D, scaled proportionally for number of months operated, with













Bhttp://www.water.ca.gov/landwateruse/annualdata/agroclimatic/

http://www.water.ca.gov/floodmgmt/hafoo/hb/sss/precipitationChttps://www.boe.ca.gov/proptaxes/pdf/ah53415.pdf

Dhttp://compost.css.cornell.edu/CoCompost.html

Ehttp://data.bls.gov/cgi‐bin/cpicalc.pl

Fhttp://www.calasfmra.com/db_trends/2013Trends.pdf



y = 982.06x‐0.251

R² = 0.8993

y = 634.24x‐0.232

R² = 0.8929

$0

$50

$100

$150

$200

$250

$300

0 5000 10000 15000

Total A

nnualized

Average

Cost

($/hd/yr)



10‐year term

20‐year term

y = 551.35x‐0.251

R² = 0.8993

y = 356.07x‐0.232

R² = 0.8928

$0

$20

$40

$60

$80

$100

$120

$140

$160

0 5000 10000 15000Total A

nnual G

HG Mitigatio

n Co

st

($/M

gCO2e)



10‐yr term

20‐year term

107

Appendix4.4:Scrapetoclosedsolardryingscenariocostdevelopmenttable

APPENDIX Mitigation Cost‐Curve Development Tables Scrape to Closed Solar Drying (12 mo.)

Dairy Size1


Cost3

Scraping Average

O&M

Cost4

Scraping Average

Emissions5

Closed Solar Average

Area6


Cost7

Closed Solar Equipment

Average

Costs8

Closed Solar Land Lease

Average

Cost9

Closed Solar Bulking

Materials Average Cost

Closed Solar O&M, Labor,

Utilities, Average

Costs10


Emissions11


Cost12

Total O&M Average

Cost13


head14


per head15


Reductions16

Average Emissions

Reduction Cost17


Cost18



termMgCO2e/yr



300 $129,412 $1,651 1 0.3 $1,715,047 $0 $896 $0 $79,248 27 $1,844,459 $81,795 $1,189 $899 756 $472 $357

750 $168,947 $4,178 2 0.7 $3,224,457 $0 $2,240 $0 $93,120 67 $3,393,405 $99,539 $807 $594 1,889 $320 $236

1,500 $220,083 $8,391 5 1.5 $5,198,359 $0 $4,480 $0 $116,241 134 $5,418,443 $129,112 $624 $454 3,777 $248 $180

3,000 $301,727 $16,982 10 3.0 $8,380,616 $0 $8,961 $0 $162,482 269 $8,682,344 $188,425 $494 $358 7,555 $196 $142

5,000 $391,685 $28,605 16 5.0 $11,915,980 $0 $14,935 $0 $224,136 448 $12,307,664 $267,676 $420 $304 12,591 $167 $121

10,000 $575,705 $58,622 34 10.0 $19,210,533 $0 $29,870 $0 $378,272 896 $19,786,239 $466,763 $342 $248 25,181 $136 $99







6Closed solar area required scaled from vendor information and assuming



4 ft2 per ton per year average area requirement

7Closed solar drying cost extrapolated from budgetary information for 20,000 tpy system and applying 0.7 exponential scaling factor, includes $750,000 biofiltration units

8Costs included in previous column


B

10O&M labor, utilities and associated costs etimated from vendor information using the following assumptions

$0.148/kwh electricity cost C

$70,000/yr labor cost11Average direct emissions from processing scaled from annual estimates of diesel and electricity, scaled proportionally for number of months operated, with

Diesel emissions = 10.45 kg CO2‐equivalent/gallon D

Electricity emissions = 0.277 kg CO2‐equivalent/kWh D

12Sum of system and equipment capital costs










Bhttp://www.calasfmra.com/db_trends/2013Trends.pdf

Chttp://www.eia.gov/electricity/monthly/epm_table_grapher.cfm?t=epmt_5_6_a

Dhttp://www.arb.ca.gov/regact/2014/capandtrade14/ctlivestockprotocol.pdf

y = 8602.7x‐0.354

R² = 0.9952

y = 6845.1x‐0.365

R² = 0.9925$0

$200

$400

$600

$800

$1,000

$1,200

$1,400

0 5000 10000 15000

Total A

nnualized

Average

Cost

($/hd/yr)



10‐year term

20‐year termy = 3415.4x‐0.354

R² = 0.9952

y = 2717.6x‐0.365

R² = 0.9925$0

$50

$100

$150$200

$250

$300

$350

$400

$450$500

0 5000 10000 15000Total A

nnual G

HG Mitigation Co

st

($/M

gCO2e)



10‐yr term

20‐year term

108

Appendix4.5:Scrapetoforceddryingwithnaturalgasscenariocostdevelopmenttable

APPENDIX Mitigation Cost‐Curve Development Tables Scrape to Forced Evaporation (Natural Gas Fuel) (12 mo.)

Dairy Size1


Cost3

Scraping Average

O&M

Cost4

Scraping Average

Emissions5

Forced Evap Average

Area6

Forced Evap Average

Cost7

Forced Evap Land Lease

Average Cost8

Forced Evap O&M, Labor,

Utilities, Average

Costs9

Forced Evap Average

Emissions10

Total Average

Capital Cost11

Total O&M Average

Cost12


head13


per head14


Reductions15


Cost16


Cost17

Adult Cows2 $ $/yr MgCO2e/y acres $ $/yr $/yr MgCO2e/yr $ $/yr$/head/yr - 10 yr


termMgCO2e/yr



300 $129,412 $1,651 1 0.0 $288,329 $14 $133,824 547 $417,741 $135,489 $659 $593 447 $442 $398

750 $168,947 $4,178 2 0.0 $542,087 $35 $229,560 1,367 $711,034 $233,773 $453 $408 1,118 $304 $274

1,500 $220,083 $8,391 5 0.0 $873,934 $69 $389,121 2,734 $1,094,017 $397,581 $374 $339 2,237 $251 $228

3,000 $301,727 $16,982 10 0.0 $1,408,926 $139 $708,242 5,468 $1,710,653 $725,362 $327 $300 4,473 $219 $201

5,000 $391,685 $28,605 16 0.1 $2,003,282 $231 $1,133,736 9,114 $2,394,966 $1,162,572 $304 $281 7,455 $204 $189

10,000 $575,705 $58,622 34 0.2 $3,229,622 $462 $2,197,472 18,228 $3,805,327 $2,256,556 $282 $264 14,910 $189 $177







6Forced evaporation area required scaled from vendor information and assuming



No additional area for solids handling assumed7Forced evaporation cost extrapolated from budgetary information from two vendors for 900‐29,000 tpy systems and applying 0.7 exponential scaling factor


B

9O&M labor, utilities and associated costs etimated from the avearge of two vendors' information using the following assumptions

$5.52/MMBtu natural gas cost C

$0.148/kwh electricity cost D

$70,000/yr labor cost10Average direct emissions from processing scaled from annual estimates of diesel and electricity, scaled proportionally for number of months operated, with

Diesel emissions = 10.45 kg CO2‐equivalent/gallon E

Electricity emissions = 0.277 kg CO2‐equivalent/kWh E

11Sum of system and equipment capital costs




15For manure diverted to solar drying, MCF and N2O emission factors for and Solid Storage

A are applied for the months opearated




Bhttp://www.calasfmra.com/db_trends/2013Trends.pdf

Chttp://www.eia.gov/dnav/ng/ng_pri_sum_a_epg0_pin_dmcf_m.htm

Dhttp://www.eia.gov/electricity/monthly/epm_table_grapher.cfm?t=epmt_5_6_a

Ehttp://www.arb.ca.gov/regact/2014/capandtrade14/ctlivestockprotocol.pdf

y = 2305.3x‐0.238

R² = 0.9379

y = 1929.5x‐0.226

R² = 0.9247

$0

$100

$200

$300

$400

$500

$600

$700

0 5000 10000 15000

Total A

nnualized

Average

Cost

($/hd/yr)



10‐year term

20‐year term

y = 1545.4x‐0.238

R² = 0.9378

y = 1293.6x‐0.226

R² = 0.9246

$0

$50

$100$150

$200

$250$300

$350$400

$450

$500

0 5000 10000 15000Total A

nnual G

HG Mitigatio

n Co

st

($/M

gCO2e)



109

Appendix4.6:Scrapetocompostingwithbulkingagentscenariocostdevelopmenttable

APPENDIX Mitigation Cost‐Curve Development Tables Scrape to Compost with Bulking (12 mo.)

Dairy Size1


Cost3

Scraping Average

O&M

Cost4

Scraping Average

Emissions5

Compost Pad Average

Area6

Compost Pad Average

Cost7

Compost Equipment

Average

Costs8

Compost Land Lease

Average

Cost9

Compost Bulking

Materials Average Cost

10

Compost O&M, Labor, Utilities,

Average

Costs11

Compost Average

Emissions12


Cost13

Total O&M Average

Cost14


head15


per head16


Reductions17

Average Emissions

Reduction Cost18


Cost19



termMgCO2e/yr



300 $129,412 $1,651 1 0.9 $130,839 $287,949 $2,575 $120,815 $15,373 25 $548,200 $140,414 $740 $654 868 $256 $226

750 $168,947 $4,178 2 1.8 $266,998 $300,449 $5,254 $302,037 $38,373 61 $736,394 $349,842 $613 $566 2,169 $212 $196

1,500 $220,083 $8,391 5 3.2 $494,839 $320,949 $9,737 $604,072 $73,383 122 $1,035,871 $695,583 $567 $534 4,339 $196 $185

3,000 $301,727 $16,982 10 6.3 $959,849 $361,949 $18,887 $1,208,144 $153,128 245 $1,623,525 $1,397,141 $546 $521 8,678 $189 $180

5,000 $391,685 $28,605 16 10.3 $1,567,956 $484,483 $31,151 $2,013,553 $241,719 293 $2,444,124 $2,315,028 $536 $513 14,578 $184 $176

10,000 $575,705 $58,622 34 20.3 $3,087,429 $667,816 $61,454 $4,027,146 $361,553 586 $4,330,950 $4,508,776 $515 $495 29,155 $177 $170







6Compost pad average area calculation estimated using CoComposter V2a model

Bwith the following inputs, other assumptions default

Raw manure total solids = 13%, C:N ratio = 19, Density=62 lb/ft3, 0.5ft

3wastewater/cow additional

Wheat straw bulking agent total solids = 90%, C:N ratio = 80, Density = 8 lb/ft3

Mixed compost solids content = 75%, C:N ratio = 40, Density = 32 lb/ft3

90 day compost, 0 day curing, 0 day fresh materials storage, and 0 day final storage periods

Assumes runoff collection pond and area required for composting opearations can utlize existing dairy storage pond, no new leachate detention pond

Four compost management systems evaluated; 1) Bucket loader turned windrows, 2) Tractor pulled windrow turned, 3) Self‐propelled windrow turned, 4) Aerated static piles. Avearge of 4 values used.7Compost pad cost assumes reinforced concrete installed cost at $3.50/ft

2.C

8Compost equipment cost assumes baseline cost for 135hp front end loader with 3 yard bucket, as estimated in CoComposter v2a model

Badjusted to 2015 pricing with 2.5%/yr inflation rate

D


E

10Bulking cost $130/ton, wheat straw, erosion control grade, CA central valley

F

11O&M labor, utilities and associated costs etimated using CoComposter v2a model

Bwith the following inputs, other assumptions default

Four compost management systems evaluated; 1) Bucket loader turned windrows, 2) Tractor pulled windrow turned, 3) Self‐propelled windrow turned, 4) Aerated static piles. Avearge of 4 values used.

Windrows 8' height x 16' width x 100' length with spacing between rows per management scenario listed above


$20/hr labor cost



B, scaled proportionally for number of months operated, with







17For manure diverted to solar drying, MCF and N2O emission factors for and Solid Storage

A are applied for the months opearated



References: Cost Curves ‐ (Power Law Regression Fits Shown)Ahttp://www.arb.ca.gov/cc/inventory/doc/docs3/3a2ai_manuremanagement_anaerobiclagoon_livestockpopulation_dairycows_ch4_2012.htm

Bhttp://compost.css.cornell.edu/CoCompost.html

Chttps://www.boe.ca.gov/proptaxes/pdf/ah53415.pdf

Dhttp://data.bls.gov/cgi‐bin/cpicalc.pl

Ehttp://www.calasfmra.com/db_trends/2013Trends.pdf

Fhttp://www.ams.usda.gov/mnreports/lswfeedseed.pdf (accessed Aug 2015)



y = 1209.5x‐0.097

R² = 0.8871

y = 952.26x‐0.074

R² = 0.8925

$0

$100

$200

$300

$400

$500

$600

$700

$800

0 5000 10000 15000

Total A

nnualized

Average

Cost

($/hd/yr)



10‐year term

20‐year term

y = 425.02x‐0.099

R² = 0.8993

y = 334.62x‐0.076

R² = 0.9076

$0

$50

$100

$150

$200

$250

$300

0 5000 10000 15000Total A

nnual G

HG Mitigatio

n Co

st

($/M

gCO2e)



10‐yr term

20‐year term

110

Appendix5:SolidLiquidseparationscenariocostdevelopmenttable

APPENDIX Mitigation Cost‐Curve Development Tables Solid Liquid Separation

Dairy Size


Average Capital Costs

Solid Liquid Separation O&M, Labor, Utilities, Average Costs


Average Direct Emissions

Total Average

Capital Cost

Total O&M Average

Cost

Total Annualized

Average Cost per head

Total Annualized

Average Cost per head

Net Average Emissions Reductions

Average Emissions

Reduction Cost


Cost

Adult Cows $ $/yr MgCO2e/yr $ $/yr$/head - 10 yr

term$/head - 20

yr termMgCO2e/yr



300 $112,093 $14,394 7 $112,093 $14,394 $104 $86 210 $148 $123

700 $130,127 $19,263 12 $130,127 $19,263 $55 $46 494 $78 $66

1,500 $166,195 $29,002 19 $166,195 $29,002 $36 $31 1,064 $51 $43

3,000 $233,822 $47,261 31 $233,822 $47,261 $27 $24 2,136 $38 $33

5,000 $323,992 $71,607 43 $323,992 $71,607 $24 $21 3,568 $34 $29

10,000 $549,417 $132,472 69 $549,417 $132,472 $21 $19 7,154 $30 $26




3Total operating and annual costs were extrapolated from two reports (Shepherd, 2010)

Band (ICF, 2013)

C

Shepherd report ‐ capital and operating costs of 300 ‐ 800 head dairies with a screw press, extrapolated out to 10,000 head with 0.675 exponential scaling factor

ICF report ‐ capital and operating costs of 1,000 and 4,000 head dairies with a rotating screen, extrapolated to smaller dairies (down to 300 head) and large dairies (up to 10,000 head) with a 0.675 exponential scaling factor4Estimated operating and capital costs from the two reports were interpolated for any size dairy between 300 and 10,000 head using linear regression

5Average direct emissions are extrapolated from a base case of 25 hp motor run for 3.5 hours each day for a 300 head dairy as specified in Shepherd's report

Electricity emissions = 0.277 kg CO2‐equivalent/kWh D

Extrapolated by 0.675 exponential scaling factor to 10,000 head68% interest rate, 10‐year term for capital loan, plus annual O&M, divided by number of adult cows


815% of lagoon manure manure diverted to solid storage, MCF and N2O emission factors for and Solid Storage




Bhttp://db.nyfvi.org/documents/2167.pdf

Chttp://www.usda.gov/oce/climate_change/mitigation_technologies/GHG_Mitigation_Options.pdf

Dhttp://www.arb.ca.gov/regact/2014/capandtrade14/ctlivestockprotocol.pdf

y = 1122.7x‐0.449

R² = 0.9395

y = 845.74x‐0.432

R² = 0.9360

20

40

60

80

100

120

0 5000 10000 15000


($/hd/yr)



10‐year term

20‐year term

y = 1656.4x‐0.455

R² = 0.94

y = 1247.8x‐0.438

R² = 0.93660

20

40

60

80

100

120

140

160

0 5000 10000 15000Total Annual GHG Mitigation Cost

($/M

gCO2e)



10‐yr term

20‐year term

111

Appendix6.1:Aerationscenario(loweffectiveness)costdevelopmenttable

APPENDIX Mitigation Cost‐Curve Development Tables Aeration (Low Effectiveness)

Dairy Size1Aeration


Aeration Utilities

Average Costs 3

Aeration Maint. And Labor

Average Costs 4

Aeration Average

Emissions5


Total O&M

Average Cost6


head7

Total Annualized

Average Cost

per head8


Reductions9


Cost10


Cost11

Adult Cows2 $ $/yr $/yr MgCO2e/yr $ $/yr$/head/yr - 10 yr

term$/head/yr - 20

yr termMgCO2e/yr



300 $57,754 $30,123 $14,888 57 $57,754 $45,011 $179 $170 686 $78 $74

750 $144,386 $75,307 $36,071 142 $144,386 $111,378 $177 $168 1,716 $77 $73

1,500 $288,771 $150,614 $68,315 284 $288,771 $218,929 $175 $166 3,432 $76 $72

3,000 $577,543 $301,229 $121,320 568 $577,543 $422,549 $170 $160 6,863 $74 $70

5,000 $962,571 $502,048 $168,180 946 $962,571 $670,228 $163 $154 11,439 $71 $67

10,000 $1,925,143 $1,004,095 $166,257 1,892 $1,925,143 $1,170,353 $146 $137 22,877 $64 $60


258.2% of adult cow manure assumed destined for aerated lagoon

A.

3Assumes $0.148/kWh electrical cost

B

4Assumes 5% of capital annual maintenance cost and labor costs increasing linearly from $12,000/yr for a 300 head dairy to $70,000/yr for 10,000 head dairy

5Average direct emissions from processing scaled from annual estimates of diesel and electricity usage, with

Diesel emissions = 10.45 kg CO2‐equivalent/gallon C

Electricity emissions = 0.277 kg CO2‐equivalent/kWh C

6Sum of utilities, maintenance, and labor costs



9For aerated lagoon, MCF = 0.3 assuming low effectiveness (poorly managed aerobic system)

D and N2O direct emission factor = 0.01 gN2O/gN for aerated lagoons

E




Bhttp://www.eia.gov/electricity/monthly/epm_table_grapher.cfm?t=epmt_5_6_a

Chttp://www.arb.ca.gov/regact/2014/capandtrade14/ctlivestockprotocol.pdf

Dhttp://www.ipcc‐nggip.iges.or.jp/public/2006gl/pdf/5_Volume5/V5_6_Ch6_Wastewater.pdf

Ehttp://www.ipcc‐nggip.iges.or.jp/public/2006gl/pdf/4_Volume4/V4_10_Ch10_Livestock.pdf

y = 250.25x‐0.053

R² = 0.7823

y = 242.31x‐0.056

R² = 0.7811

$0$20$40$60$80$100$120$140$160$180$200

0 5000 10000 15000


($/hd/yr)



10‐year term

20‐year term

y = 109.39x‐0.053

R² = 0.7823

y = 105.92x‐0.056

R² = 0.7811

$0

$10

$20

$30

$40

$50

$60

$70

$80

$90


($/M

gCO2e)



10‐yr term

20‐year term

112

Appendix6.2:Aerationscenario(higheffectiveness)costdevelopmenttable

APPENDIX Mitigation Cost‐Curve Development Tables Aeration (High Effectiveness)

Dairy Size1Aeration


Aeration Utilities

Average Costs 3

Aeration Maint. And Labor

Average Costs 4

Aeration Average

Emissions5


Total O&M

Average Cost6


head7

Total Annualized

Average Cost

per head8


Reductions9


Cost10


Cost11

Adult Cows2 $ $/yr $/yr MgCO2e/yr $ $/yr$/head/yr - 10 yr

term$/head/yr - 20

yr termMgCO2e/yr



300 $57,754 $30,123 $14,888 57 $57,754 $45,011 $179 $170 1,273 $42 $40

750 $144,386 $75,307 $36,071 142 $144,386 $111,378 $177 $168 3,183 $42 $40

1,500 $288,771 $150,614 $68,315 284 $288,771 $218,929 $175 $166 6,367 $41 $39

3,000 $577,543 $301,229 $121,320 568 $577,543 $422,549 $170 $160 12,733 $40 $38

5,000 $962,571 $502,048 $168,180 946 $962,571 $670,228 $163 $154 21,222 $38 $36

10,000 $1,925,143 $1,004,095 $166,257 1,892 $1,925,143 $1,170,353 $146 $137 42,443 $34 $32


258.2% of adult cow manure assumed destined for aerated lagoon

A.

3Assumes $0.148/kWh electrical cost

B

4Assumes 5% of capital annual maintenance cost and labor costs increasing linearly from $12,000/yr for a 300 head dairy to $70,000/yr for 10,000 head dairy

5Average direct emissions from processing scaled from annual estimates of diesel and electricity usage, with

Diesel emissions = 10.45 kg CO2‐equivalent/gallon C

Electricity emissions = 0.277 kg CO2‐equivalent/kWh C

6Sum of utilities, maintenance, and labor costs



9For aerated lagoon, MCF = 0 assuming high effectiveness (well managed aerobic system)

D and N2O direct emission factor = 0.01 gN2O/gN for aerated lagoons

E




Bhttp://www.eia.gov/electricity/monthly/epm_table_grapher.cfm?t=epmt_5_6_a

Chttp://www.arb.ca.gov/regact/2014/capandtrade14/ctlivestockprotocol.pdf

Dhttp://www.ipcc‐nggip.iges.or.jp/public/2006gl/pdf/5_Volume5/V5_6_Ch6_Wastewater.pdf

Ehttp://www.ipcc‐nggip.iges.or.jp/public/2006gl/pdf/4_Volume4/V4_10_Ch10_Livestock.pdf

y = 250.25x‐0.053

R² = 0.7823

y = 242.31x‐0.056

R² = 0.7811

$0$20$40$60$80$100$120$140$160$180$200

0 5000 10000 15000


($/hd/yr)



10‐year term

20‐year term

y = 58.961x‐0.053

R² = 0.7823

y = 57.091x‐0.056

R² = 0.7811

$0$5$10$15$20$25$30$35$40$45$50


($/M

gCO2e)



10‐yr term

20‐year term

113

Abbreviations Acronym DefinitionAD AnaerobicdigestionBOD BiologicaloxygendemandBODBtu BritishthermalunitC:N CarbontonitrogenratioCA CaliforniaCAFOs ConfinedanimalfeedingoperationsCDFA CaliforniaDepartmentofFoodandAgricultureCH4 MethaneCNG CompressednaturalgasCO2 CarbondioxideCO2eq CarbondioxideequivalentDO DissolvedoxygenGHG GreenhousegasGDE GallonDieselEquivalentH2S Hydrogensulfidehp HorsepowerkWh kilowatt‐hourMbtu MegaBritishthermalunit

MCF MethanecorrectionfactorMg Metrictonne=1000kgmV MillivoltsMW MegaWattN2O NitrousoxideNH3 AmmoniaNH4+ AmmoniumNO NitricoxideNO3 NitrateNO3‐N NitrateexpressedasnitrogenNOx NitrogenoxidesO&M OperationsandMaintenanceORP Oxidation‐reduction‐potentialPF PlugflowRRSAF RussellRanchSustainableAgricultureFacilityRUE ResourceuseefficientSO4 SulfateSOx SulfuroxidesTg Teragram=MillionMg=millionmetrictonnes.TS TotalsolidsUC UniversityofCaliforniaVFAs VolatilefattyacidsVOCs VolatileorganiccompoundsVS Volatilesolids

114

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ASABE.(2005).ManureProductionandCharacteristics.ASAEStandardD384.2.March

2005.AmericanSocietyofBiologicalandAgriculturalEngineers.St.Joseph,Michigan.

Bennamoun,L.(2012).Solardryingofwastewatersludge:Areview.Renewableand

SustainableEnergyReviews16:1061–1073.BioCNG.(2015)."CNGFuelingCaseStudies."fromhttp://biocng.us/projects/cng‐fuel‐

projects/.Bjorneberg,D.L.andB.A.King(2014)."GroundwaterUseonSouthernIdahoDairies."

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