University of Arkansas, FayettevilleScholarWorks@UARKBiological and Agricultural EngineeringUndergraduate Honors Theses Biological and Agricultural Engineering

5-2016

Municipal Composting and Organic WasteDiversion: The Case of Fayetteville, ArkansasMichael E. Hoppe

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Recommended CitationHoppe, Michael E., "Municipal Composting and Organic Waste Diversion: The Case of Fayetteville, Arkansas" (2016). Biological andAgricultural Engineering Undergraduate Honors Theses. 39.http://scholarworks.uark.edu/baeguht/39

Introduction

Itisestimatedthatnearly40%ofthefoodproducedintheUSiswasted

somewherebetweenharvestandconsumption.Theamountofresourcesthathave

beenusedinproducingthiswastedfoodisvaluedatapproximately$165billion

yearly.Thiswastedfoodissenttolandfillswhereisdecomposesreleasingmethane

andotherdecompositionbyproducts.Methaneisagreenhousegas28timesas

potentascarbondioxideandisthemajorbyproductof35milliontonsoffood

decomposinginlandfills(Gunders,2012).Infactthisdecomposingfoodis

responsiblefor23%ofUSmethaneemissionsyearly(USEPA,2013).Thishas

seriousenvironmentalimplicationintermsglobalclimatechange.

TheEnvironmentalProtectionAgency(EPA)hassetguidelinestopromote

foodrecoveryandestablishedahierarchyforfooddisposal,whichisasfollows:1)

sourcereduction,2)feedhungrypeople,3)feedanimals,4)industrialuses,5)

composting,6)landfill/incineration(USEPA,2013).Thishierarchywasdesignedto

helppromotethereductionofthecolossalmassesoffoodwasteproducedintheUS

onayearlybasis.Implementationoftheabove-describedhierarchyforfood

disposalimpliesconsiderableinfrastructureinordertomakeaseriousimpacton

foodwastereduction.

Asacountrywerecycleatrateof35%whenspeakingintermsofall

recyclablematerialsandthatratehasbeenrelativelystaticrecentlywhencompared

togrowthinthe1990s(Plattetal.,2014).Themostsuccessfullyrecovered

materialsasapercentofwhatisproducedarepapers,metals,yardtrimmings,glass,

2

andbiosolids.Allofthesehaverecoveryratesexceeding25%andsome,suchas

papersandyardtrimmings,exceed60%(USEPA,2013).However,when

consideringtheamountoffoodwastewerecoverasapercentofwhatisproduced,

itisonly5%(Gunder,2012).Thisisthelowestrecyclingrateformaterialsthatthe

EPAconsidersrecoverable.Examiningasurveyofcompostingfacilitiesacrossthe

country,itisseenthatonlyasmallamount,approximately7%,ofalloperating

compostingfacilitiescompostfoodscraps(Plattetal.,2014).So,thismakesone

wonderastowhycompostingisnotawidelyadoptedpractice.Accessibilityand

easeofcompostingmayprovetobemoreofanimpedimentthaninitially

anticipated.

Acrossthecountryroughly350municipalfood-compostingfacilitiesare

operating,andmostofthesearenearlargecitiesthatpromotesustainable

developmentandgreeninfrastructure(Plattetal.,2014).Theshiningexampleof

sustainablewastemanagementistheCityofSanFranciscoandtheirzerowasteby

2020initiative.Thecitycurrentlymandatesresidentstoseparaterecyclables,

compostablematerials,andlandfilltrashwiththehopesofeventuallycomposting

orrecyclingnearlyallwasteby2020(SFEnvironment,2016).Theycurrentlycollect

approximately600tonsofcompostablewasteperday,contributingtothediversion

of75%ofallwastefromlandfills.AcompanybythenameofRecologypartnered

withthecityofSanFranciscotocollectandprocessalloftheirwaste.Byrecycling

andcompostingasopposedtolandfilling,themethaneandothergreenhousegases

producedintheprocessingofthewastecanbedecreased.Thisisexhibitedinthe

figuresbelow.

3

Source:UnitedStateEnvironmentalProtectionAgency(2015)

Figure1&2.GreenhouseGasEmissionsfromLandfillsandComposting

Whenignoringthesequestrationpropertiesofcomposting,itproduces0.11

MTCO2E/shorttoncomparedto0.46MTCO2E/shorttoninalandfillthatuses

GreenhouseGasEmissionsfromLandfills

GreenhouseGasEmissionsfromComposting

4

methanerecapturingmethods(Allenetal.,2015).Thereductioninmethaneis

becauserecyclingandcompostingdonotcreatetheanaerobicconditionspreferred

bymethaneproducingbacteria(Miyamoto,1997).Otherlargecities,suchasSeattle,

havesincefollowedsuitandalsosetforthazerowastegoalfortheircity.Policycan

beaninfluentialtoolinpromotingcompostingthroughoutcommunitiesandcities

andisarguablywhatisneededtotrulyachievechangeinthewaypeopleview

waste.

Over20stateshavelegislationoutlawingthedisposalofyardwastein

landfills,whileonlyafewstateshaveanylawsregardingthedisposaloffoodand

othercompostablewaste(Plattetal.,2014).Policy,althoughinfluential,walksafine

linebetweenwhatacommunityshoulddo,andwhatpeoplewanttodoasmembers

ofthecommunity.Thisisareasonwhymorethanjustpolicychangeisneededto

ensurethesuccessofamunicipalcompostingprogram.Itrequiresaculminationof

planning,logistics,policy,facilities,maintenance,education,andengineeringto

achieveasystemformunicipalcompostingtobeeffective.Nottomention

constructionoffacilitiesforcompostingfoodwastecanberelativelyhighdueto

regulationsonsafetyandoperation(Plattetal.,2014).

Therearealotofchallengesthatopeningandrunningafoodcomposting

facilitypose.Anytimefoodisbeinghandledinaprocess,therewillbethe

opportunityforthegrowthofpathogens;thisiscombattedincompostingbythe

heatingandmixingofcompostingbiomass.Bacteriaaerobicallydecomposethe

organicmatterinturnreleasingheatandcausingtemperaturesincompostpilesto

risetoapproximately55°Cwhichissufficienttokillpathogensalthoughnotspores,

5

ifcompostingisdoneproperly(Trautmannetal.,1997).Contaminationmustbe

avoidedatallcosts.Thesellofcontaminatedcomposttoagriculturaloperations

couldhaveseriousimplicationsintermsofthespreadingdiseasetocrops,animals,

andhumans.Thepresenceofresidualherbicidessuchasaminopyralid,clopyralid,

picloram,andaminocyclopyrachlorincompostarealsoaseriousconcernof

municipalfacilitiesbecauseoftheseriousrepercussionsitcanhaveoncrops.These

typesofcontaminationcouldcausemanymillionsofdollarsworthofdamageina

givenfacility(Plattetal.,2014).

Phosphorous(P)andnitrogen(N)instormwaterrunoffisanotherserious

concernforfacilitiesthatcompostfood.Becauseofthat,anyfacilitythatcomposts

foodscrapsisrequiredtohaveastormwatermanagementsystemthatremoves

contaminantsbeforeallowingrunofftoexittheirproperty.Buildingthesestorm

watermanagementssystemsinadditiontoothersitepreparationscancost

hundredsofthousandsofdollarsperacretoplanandcarryout,andthisdoesnot

includeaspectslikeoperatingcostsandprocessingcostsforthefacility(Plattetal.,

2014).Anotherdifficultchallengeofoperatingoneofthesefacilitiesistheneedto

controltheodorofdecomposingorganicmatter,aprocessthathasthepotentialto

produceawiderangeofodorousgasesgiventherightconditions.Odorseemsto

havethemostimpactwiththepublicandcangivetheentirefacilityandprograma

badreputationifnothandledproperly.

Alackofsocialchangeismostlikelythebiggestinhibitorofmunicipal

composting,butthatisadifficultmetrictoquantify.Sustainabilityhasgainedalot

ofpopularityinrecentyears,asweseemanylargecompanies,cities,and

6

universitiestakeonchallengessuchasreducingenergyuseanddivertingwaste

fromlandfills.However,evenwithlargecontributorstosocietymakingthese

changeswiththehopesofinfluencingmore,westillonlysee5%ofourfoodwaste

beingrecovered.Togivesomeperspectiveonhowinefficientitistolandfilluneaten

foodsupply:40%offoodthatiswastedisresponsiblefor25%ofallfreshwater

usedinthecountry,4%ofthetotaloilconsumption,and$750millionindisposal

fees.Moreover95%ofourfoodwasterepresents35milliontonsofwasteputinto

landfillsperyear(Gunder,2012).Thesearestaggeringnumberswhenyouconsider

thepriceofdroughts,oil,methaneemissions,andthefactthatmanypeoplestillgo

hungryeverydayintheUS.

FayettevilleArkansasCurrentSituation

Fayetteville,Arkansasisasmallcitywhencomparedtoothersinthecountry

butitisoneofthelargestinArkansaswithapopulationof80,621and54square

milesoflandarea(USCensus,2014).InDecember2013,thecitygovernmentput

forthandpassedResolutionNo.260-13,whichsetagoalforthecitytoreach80%

wastediversionby2025(CityofFayetteville,2016).Aspartoftheresolution,the

cityhiredaconsultingfirm,KesslerConsultingInc.(KCI)toassessthecurrent

system,conductawastecompositionstudy,andhelpthecitydevelopawaste

diversionmasterplan.BelowisagraphmadebyKCIthatshowsthewaste

generatedoverthelasttenyearsinFayetteville,andofthat,whatisrecycled,

composted,andlandfilled:

7

Source:KesslerConsultingInc.(Mitchell2015)

Figure3.FayettevilleWasteStream

Asof2014,Fayettevillehasadiversionrateof20%,muchlowerthantheir

goalof80%.Asofnowonly9%oftotalwastegeneratedisrecycledand11%is

composted(Mitchell,2015).Thecitycurrentlydoescurbsiderecyclingusing18

gallongreenbinsthatareseparatedatthecurbbycityemployeesinto

compartmentalizedtrucks.Residentsandbusinessesareallowedtoplacepapers,

cardboards,aluminumandsteelcans,plasticbottles,glassbottles,andafewother

recyclablesintheirbinsandthecitypicksthemuponceaweek.Untilrecentlythe

cityofFayettevilleonlycompostedyardwaste,asdomostmunicipalitiesaroundthe

country.Roughlyhalfofthestatesinthecountryhavelegislationoutlawingthe

disposalofyardwasteinlandfills,Arkansasbeingoneofthem(Plattetal.,2014).

Startingin2016,thecityofFayetteville,withthehelpofKCI,begantwopilot

projects.InJanuaryof2016theystartedafoodwaste-compostingpilottoworkasa

8

partofthealreadyexistingyardwastecompostingfacility,andinFebruaryof2016

theybeganasinglestreamrecyclingpilotprogram.KCIchosethesetwopilot

programsbasedonareasthatcouldmakethelargestimpactondiversionrates.

Excludingwhatisalreadybeingcompostedandrecycled,thecitieswastestreamis

comprisedof19%compostablematerial,and26%recyclables(Mitchell,2015).

Thecompostingpilotprojectcollectsfromaselectnumberofrestaurants

andlocalbusiness,andthenfoodwastecollectedismixedintheyardwasteatthe

alreadyexistingyardcompostingfacility.Thefacilityhadtoundergoasmallamount

ofretrofittinginordertoallowittoacceptfoodscraps.Thisisinordertomakesure

thefacilitystayswithintheArkansasDepartmentofEnvironmentalQualities

(ADEQ)standardsofoperation,whicharefarstricteronfoodcompostingfacilities

thanyardwastefacilities.KCImadethedecisionthatitwouldbebestforthecityto

usemodifiedstaticaeratedpile(MSAP)compostingsystemintheirpilotasopposed

tothetraditionalturnedwindrowsthecityusedwhenthewastestreamwassolely

yardwaste(KCI,2015).Belowisaschematicofastaticaeratedpile:

9

Source:FAONRAES-114(1999)

Figure4.AeratedStaticPileCompostingSchematic

Aeratedcompostinghasafewbenefitsoveraturnedwindrowsystem,the

majoronebeingthatittakesonlyonetotwomonthsforafinishedcompost,whilea

turnedwindrowcantake6monthsorlonger.Otherbenefitsincludethereduction

ofodors,adecreaseinrequiredmechanicaloperation,andabilitytomaintain

aerobiccondition,whicharenecessaryforbiomoleculebreakdown(Mitchell,2015).

ThepilotprogramisunderwayuntilJuly2016,andatthatpointKCIwillanalyzethe

datatheyhavecollectedanddetermineifthissystemcouldbeafeasiblepartof

Fayetteville’swastediversionmasterplan.PreliminarysuggestionsfromKCI

suggestthattheyareinconsultationwithADEQtoexamineifthefacilitycould

permanentlyacceptfoodwasteandstartcollectionofcommercialcompostaround

thecity,withthehopesofaddingresidentialfoodwastecollectionwithinfiveyears

(KCI,2016).

10

Inadditiontothecompostingpilot,theCityisalsorunningasinglestream-

recyclingpilotfromFebruarytoMayof2016thatcollectsfromasmallnumberof

neighborhoodsandapartmentsfromaroundFayetteville.Thecityalreadydoes

curbsiderecycling,howevercollectioniscurrentlyconductedbyhavingcity

employeessortrecyclablescurbsideandplacethemintheirrespectivebinsonthe

collectiontruck.KCIbelievesthatbymovingtoasinglestreamsystem,efficiencies

incollectionwillgreatlyincreaseandthat,ifimplementedcitywide,wouldalso

increasecommunityparticipation.Thisstyleofcollectionwouldideallyhelphandle

someoftheinefficienciesinthedropofftherecyclablesattheMaterialsCollection

Facilityaswell(Mitchell,2015).ThroughthispilotprogramthecityofFayetteville

hopestogainusefulinformationonthefeasibilityofadoptingaprogramlikethis

citywide.

Since2003,Fayettevillehasusedapay-as-you-throwcollectionprogramin

whichresidentscanchoosebetweena32,64,or95-gallonwastecartthatthecity

picksuponceaweek.Residentsarechargedamonthlyfeeof$9.37,$14.30,$20.31

respectively,forcollection,withaonetimechargeof$20ifaresidentwouldliketo

moveuptoabiggercart.However,thereisnochargefordownsizing.(Cityof

Fayetteville,2016)Thisprogramistohelpprovideanincentiveforresidentsto

recyclemoreandsendlesstothelandfills,whilealsospendinglessintheprocess.

Programslikethisaregrowingacrossthecountryasmoremunicipalitiesstrive

towardsreducingwasteacrosstheircities.

ThecityofFayettevilleistheonlyentityallowedtocollectwasteand

recyclableswithinitslimits.TheCitydoeshavecontractswithprivatecompaniesto

11

aidinsomeofthewastecollectionandhaulingthatrequiremoreattentionor

equipment.CompaniessuchasAlliedWaste,WasteManagement,andDeffenbaugh

Industrieshavethesecontractswiththecitytohandlehazardouswastes,

constructionwasteinlarge(over20cubicyards)roll–offdumpsters,and

recyclablesnotwithintheareaservicedbytheresidentialrecyclingprogram,such

astheUniversity(Mitchell,2015).

TheUniversityofArkansasrepresentsalargeportionofFayetteville’s

populationwhenschoolisinsession.Becausethecitydoesnotservicethe

Universitywithrespecttowasteandrecyclingcollection,theyarenotincludedas

partofFayetteville’swastediversionmasterplan.Infact,theUniversityhassetits

owngoalofhaving90%diversionby2021withthehelpoftheOfficefor

Sustainability(Mitchell,2015).KCIinconjunctionwiththeCityandtheUniversity

didawastecharacterizationstudyfortheUniversityatthesametimetheywere

conductingonefortherestofthecity.TheUniversityreimbursedthecityforthe

consultingwork,andplanstousetheinformationintheirZeroWasteActionPlan

(Olson,2014).BelowisafigureproducedbyKCIshowingthewastestreamsofthe

Universityduring2014:

12

Source:KesslerConsultingInc.(Mitchell2015)

Figure5.UniversityofArkansasWasteComposition

Fayettevillehasmanystepstotaketoreachtheirgoalof80%diversionby

2025.Itwillrequireeveryoneinthecitycompostingandrecyclingeverypieceof

wastethatcanbecompostedorrecycled(KCI,2016).Achangeinthewaypeople

viewwasteisnecessaryforaprogramlikethistobesuccessful,andtheCityrealizes

thatoneofthefirststepsinachievingthisisthroughcommunityoutreachand

education.Theydevelopedamarketingandeducationprogramcalled“Recycle

Something.”Thiscampaignsponsorsnumerousevents,cleanups,andtours

throughoutthecity.Itprovidesoutreacheducationthroughschoolandcommunity

presentationsinthehopesofcultivatinganewwayofthinkingaboutwastearound

thecity.

DiscussionofPotentialSolutions

Problemsasimmenseaswastemanagementwillneverhaveasingle

solution.Ittakesacalculatedcombinationofsolutions,andthatiswhytheCityof

13

FayettevillehashiredateamofengineersfromKCItohelpdeveloprealistic

solutionsforwastediversion.Thetwopilotprojectsdiscussedpreviouslyare

examplesofpotentialsolutionsthatwillhelpFayettevillemovetowardtheir

diversionrategoals.Theengineerschosethesepilotprojectsbecausetheysawthat

theseareascouldhavethelargestimpactonoveralldiversion.

Therecanbeaninfiniteamountofinputswhendesigningawastediversion

masterplanforacity,butitisthejoboftheengineertodeterminewhataspectsof

thedesignaremostimportant,andwhathasthebiggestimpactontheoutcome.

Parameterssuchaspopulationandwastecompositionarecrucialbecausethey

directlyimpacttheamountofeachtypeofwasteproduced,andthereforeimpact

howmuchwastemustbemanaged.Theseparametersalsogivetheabilitytopredict

futuresituationsandallowtheengineertomakedecisionsbasedonthose

calculatedpredictions.

Whenfocusingontheproblemofhandlingallcompostablematerialsin

Fayetteville,acertainsetofparameterscanbedefinedasmostimportant.Thesecan

includebutmaynotbelimitedtopopulation,totalamountofmaterialproducedper

year(tons),compositionintermsofnitrogenandcarbon,capitalcostoffacilityand

equipment,operatingcost,landareaavailableandtimetogetfinishedcompost.

Basedontheinfluxofcompostablematerialinagivenyear,afacilitycanbesizedto

handlethiswasteandreturnafinishedmarketableproductthatcanbesoldto

residentsforgardensandtolocalfarms.

14

Basedondatafrom2014,thecitycollected63,415tonsofwastethroughout

theyear,ofwhich19%,12,049tons,ofcompostablematerialwassenttoalandfill

(Mitchell,2015).ConsideringthattheUSlandfilled37milliontonsoffoodin2014,

responsiblefor23%ofapproximately29millionstonsofmethaneproducedyearly

(USEPA,2014).Basedonthesenumbers,Fayettevillereleasedapproximately2200

tonsofmethaneintotheatmospherein2014asaresultofwastedfood

decomposinginlandfills.Belowisasamplecalculationshowingapproximationof

Fayetteville’smethaneproductionasaresultoffoodwaste:

𝐹𝑎𝑦𝑒𝑡𝑡𝑒𝑣𝑖𝑙𝑙𝑒 𝐹𝑜𝑜𝑑 𝑊𝑎𝑠𝑡𝑒𝑈𝑆 𝐹𝑜𝑜𝑑 𝑊𝑎𝑠𝑡𝑒

× (𝑝𝑒𝑟𝑐𝑒𝑛𝑡 𝑜𝑓 𝑡𝑜𝑡𝑎𝑙 𝑚𝑒𝑡ℎ𝑎𝑛𝑒 𝑓𝑟𝑜𝑚 𝑓𝑜𝑜𝑑 𝑤𝑎𝑠𝑡𝑒)×(𝑡𝑜𝑡𝑎𝑙 𝑈𝑆 𝑚𝑒𝑡ℎ𝑎𝑛𝑒)

12,049 𝑡𝑜𝑛𝑠 𝑓𝑜𝑜𝑑 𝑤𝑎𝑠𝑡𝑒37,000,000 𝑡𝑜𝑛𝑠 𝑓𝑜𝑜𝑑 𝑤𝑎𝑠𝑡𝑒

× 0.23×29,000,000 𝑡𝑜𝑛𝑠 𝑚𝑒𝑡ℎ𝑎𝑛𝑒 = 2172 𝑡𝑜𝑛𝑠 𝑚𝑒𝑡ℎ𝑎𝑛𝑒

Thisistheequivalentofreleasing55,000tonsofcarbondioxideintothe

atmosphere,assumingaCO2equivalenceof25usedbytheUSEPA,andthatdoes

notincludetransportorprocessing,thisisonlythefoodsittinginthelandfill

anaerobicallydecomposing.Thismaybesmallwhencomparedtotheimpactother

cities,suchasNewYorkhaveontheenvironment,butforArkansas,Fayettevilleis

thethirdlargestcity,compostingthiswastecouldmakeaseriousdifference.

Fayetteville’senvironmentalimpactwasanalyzedfurtherusingtheEPA’s

wastereductionmodel(WARM),whichallowstheusertocomparetheimpactofa

city’scurrentwastemanagementsystemtoanalternativesystem.Themodeltakes

intoaccountthecompletecompositionofthecitieswastestream,andcalculatesthe

15

environmentalimpactintheformofMTCO2Ebasedonhowthewasteishandled.

Thetotalimpactiscalculatedseparatelyforeachcategoryofwastetoseewhat

categoryhasthemostimpact,andwherethelargestimprovementscanbemadein

regardtoreducinggreenhousegas(GHG)emissions.Foreachcategory,themodel

takesthefollowinginputsandassumptionsintoconsideration:

MethodofDisposal:SourceReduction,Recycled,landfilled,combusted,compostedLocation:StateandRegion

LandfillGasRecovery:Themodelassumesthenationalaverageforrecoveryrate,andassumesgasiscapturedforenergyuseDecayRate:Assumesnationalaveragefordecayrateofwasteinlandfills

TransportDistance:Distancetolandfill,combustion,recycling,andcompostingfacilities

Fayetteville:CurrentSituation

Material Tons

Recycled Tons

Landfilled Tons

Combusted Tons

Composted Total

MTCO2E

Aluminum Cans 59.0 504.4 - NA (518)

Steel Cans 112.0 756.7 - NA (174)

Glass 1,365.0 2,370.8 - NA (286)

HDPE 129.6 605.3 - NA (91)

PET 807.1 194.4 - NA (905) Corrugated Containers 2,134.0 2,320.4 - NA (5,619)

Newspaper 722.0 958.4 - NA (2,683)

Office Paper 962.0 1,664.6 - NA (215)

Dimensional Lumber - 807.1 - NA (794) Medium-density Fiberboard 144.0 176.6 - NA (508)

Yard Trimmings NA 605.3 - 7,011.0 (977) Mixed Paper (general) 139.0 4,590.3 - NA 1,326

Mixed Metals - 1,109.8 - NA 43

Food Waste NA 8,827.5 - - 6,293

Mixed Organics NA 5,145.2 - - 1,475

Mixed MSW NA 19,208.3 - NA 8,428

Total 4,796

16

Fayetteville:CompleteOrganicWasteDiversion

Material

Tons Source

Reduced Tons

Recycled Tons

Landfilled Tons

Combusted Tons

Composted Total

MTCO2E

Aluminum Cans - 59.0 504.4 - NA (518)

Steel Cans - 112.0 756.7 - NA (174)

Glass - 1,365.0 2,370.8 - NA (286)

HDPE - 129.6 605.3 - NA (91)

PET - 807.1 194.4 - NA (905) Corrugated Containers - 2,134.0 2,320.4 - NA (5,619)

Newspaper - 722.0 958.4 - NA (2,683)

Office Paper - 962.0 1,664.6 - NA (215)

Dimensional Lumber - - 807.1 - NA (794) Medium-density Fiberboard - 144.0 176.6 - NA (508)

Yard Trimmings NA NA - - 7,616.3 (936) Mixed Paper (general) - 139.0 4,590.3 - NA 1,326

Mixed Metals - - 1,109.8 - NA 43

Food Waste - NA - - 8,827.5 (1,347)

Mixed Organics NA NA - - 5,145.2 (711)

Mixed MSW NA NA 19,208.3 - NA 8,428

Total (4,989)Table1&2.ResultsfromEPA’sWARM

Figure6.ImpactsofFayetteville’sWasteStream

(8,000)

(6,000)

(4,000)

(2,000)

0

2,000

4,000

6,000

8,000

10,000

Alum

inum

Cans

SteelCans

Glass

HDPE

PET

CorrugatedContainers

Newspaper

OfnicePaper

DimensionalLum

ber

Medium-density

YardTrimmings

MixedPaper(general)

MixedMetals

FoodWaste

MixedOrganics

MixedMSW

TotalMTCO2E

GHGEmssisionsfromFayettevilleArkansasWaste

CurrentSituation WithOrganicWasteDiversion

17

TheresultsfromtheWARMmodelreflecttheundeniableimpactfoodand

otherorganicwastehasonthereleaseofGHGwhenitislandfilled.Ifthecityof

Fayettevillewereabletomoveawayfromlandfillingorganicwaste,andtowards

completeorganicwastediversion,theirtotalimpactfromwastemanagementwould

gofromanetpositiveimpactof4,796MTCO2Eperyeartoanetnegativeimpactof

4,989MTCO2Eperyear.TheresultsoftheanalysisreflectFigure1&2inwhich

compostingandlandfillingarecomparedbasedonsubsequentGHGemission.This

helpstosolidifythatbycompostingorganicwastecomparedtolandfillingit,the

resultsareavastreductioninenvironmentalimpactwithregardtoGHGemissions.

ThesizeofFayettevillemakeshandlingitscompostablewastemuchmore

simplethanitwouldbeforacitythesizeofSanFrancisco.Fayettevillereceived

approximately12,000tonsperyearincompostablewaste,whileSanFrancisco

receivedaround219,000tonsperyear.Whatthismeansis,unlikeSanFrancisco,

Fayettevillecouldpotentiallyhaveasinglefacilitywithasinglestyleofcomposting

thatcouldeasilyhandleallofthewasteproducedyearly.Asidefrompassivestatic

composting,nearlyanystyleofcompostinghastheabilitytohandlethisamountof

organicwasteinayear(Plattetal.,2014).Theyrangeincapacityandtimeto

finishedproduct.

Turnedwindrowsarethesimplestsystemandhaveacapacityrangingfrom

3,000to150,000tonsperyear,butthatislargelydependentonlandavailability

(Plattetal.,2014).Windrowscoveralotofground,soalargelandareaisneededto

carryoutthecomposting.Anotherdownfallofthewindrowisevenwithconsistent

turning,ittakesupto6monthstogetafinishedcompostproduct.TheCityalready

18

hasawindrowfacilitythathandlesyardwaste,butitalreadyoperatesatcapacity.

Withtimeandlandconstraintsconsidered,thiswouldnotbethebestsystemfor

Fayettevilletoconsiderforcompostingadditionalwaste.

Activelyaeratedstaticpilesarethestepupfromaturnedwindrowinterms

ofprocesscontrol.Theyactivelypushorpullairthroughthepileandintheprocess

helpcontroltemperature,moisturecontent,andodor.Bycontrollingthese

parameters,thebreakdownofthecomposttakesonly4-6weeks,whichis

significantlyshorterthanturnedwindrowsandpassivestaticsystemsanditallows

foramoreconsistentproduct.Manycompaniesofferproprietaryversionsofthese

systems,butthesecanbecostlydependingonthesystem.Thecurrentsystembeing

implementedintheFayettevillefood-compostingpilotisanexampleofa

proprietarysystem.ItiscalledHarvestQuestModifiedStaticAerobicPileprocess

andaspartoftheprocessthecompanyprovidesaproprietarymixofinoculantthat

aidsinstartingthecompostingprocess(Ecoverse,2016).Systemsliketheseare

popularchoicesofcitiesofallsizesbecausetheyhavetheabilitytoserviceawide

rangeofcapacities.Theycanalsohaverelativelylowcapitalcostsaswell,

dependingonthesystemchosen.ThisismostlikelythebestoptionforFayetteville

basedonscalability,capitalcost,andtimetofinishedcompost.Belowisatableput

togetherforStateofCompostingintheUSestimatingcostsofdifferentcomposting

facilityequipmentandtheyvarygreatlybecauseofvariationsinsize:

19

Source:StateofCompostingintheUS(Plattetal.2014)

Figure7.CompostingEquipmentCosts

AFayettevillefacilitywouldbeonthelowendofthecostspectrumforallofthis

equipmentbasedonthesizethefacilityneededtohandleallofthecompostable

wastecollectedinFayetteville.

ThethirdandfinalrelevanttechnologytodiscussasasolutioninFayetteville

isanaerobicdigestion.Anaerobicdigestion(AD)involvesthebreakdownoforganic

materialsbymethaneproducingbacteriainanenvironmentthatlacksoxygen.

Anaerobicdigestionproducesbiogasasaresultofthebiologicalbreakdownofthe

organicmatter.Itisroughlya60-40mixofmethaneandcarbondioxide

respectively.Biogascanbeusedasanenergysourceasis,orberefinedintoa

cleanerburninggastobeusedinnaturalgassystems.Theotherbyproductofthe

digestionprocessisstablesolidsthatcanbemixedinwithcompost,whichcreates

greatpotentialforhybridsystems.Theyaregenerallysolidvesselsorhaveaflexible

toptoallowforexpansionduringdigestion.Themajordownsidetothesesystemsis

thesteepcapitalcosttopurchaseadigester,whichisusuallyinthemulti-million

dollarrange.Thecostalonemakesthisnotafeasibleoptionforatownassmallas

20

Fayetteville.However,theUniversitycouldconsiderdesigningasmallonefor

handlingfoodwasteon-site.Itwouldserveasagreateducationalopportunityfor

bothfacultyandstudents.

Conclusion

Itisclearthataseriousfoodwastecollectionprogramneedstotakeplacein

orderforFayettevilletoreachitsgoalof80%wastediversionby2025.Theyareon

therighttrackwiththetwopilotprojects,andthemasterplanintheworks.Itis

goingtotakeconsiderablymorecommunityeducationandwillingnessforthatgoal

tobecomeareality.KCIbelievesthatthestaticaeratedsysteminthecomposting

pilotprojectwillbethebestfitforhandlingFayetteville’swaste.Theresultsofthe

pilotwiththeMSAPsystemwillcomeinattheendofJulyandwillhelpthecity

decidewhethertoimplementthatproprietarysystemorpotentiallyseekout

anothersimilarsystem.

Regardlessofwhatdecisiontheymake,itwillideallybeastepmadetoward

acitywidefoodwastecollectioninfrastructurethathandlesallcompostablewaste

producedbythecity.Ifthecitycandothis,theywillreducetheircarbonfootprint

fromwastemanagementbyapproximately200%,andthatisonlyconsideringif

theycompostallorganicsthatcanbecomposted.Thecitycanfurtherincreasethis

reductionthroughotherrecyclingandrecoveryprogramsinpursuitoftheir80%

diversiongoal.

21

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