Managing The Energy Cost Of Food

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Managing The Energy Cost Of Food
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Whiffen, H.J.H.
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EES-99 May1993 ManagingTheEnergyCostofFood1 H.J.WhiffenandL.B.Bobroff2INTRODUCTIONFoodisimportant.Alllivingthingsneedenergy. Humans,likeotheranimals,gettheirenergyfromthe foodtheyeat.Energyisnecessarytomakethefood thatgivesusenergy.Fossilfuelenergyinputsare usedineverystepofdomesticcropproductionand foodpreparation,fromseedtosupper: toplant,irrigate,fertilizeandprotectthegrowing cropfrompests, toharvestandtransportrawfoodstoaprocessing facility, tostore(warehouse),clean,cook,mix,process, preserveandpackagethefood, totransporttheretailproducttothegrocerystore shelf, tokeepfoodsfreshwhenondisplayinabrightly litstore,perhapschilledorfrozen,awaiting purchase, toprepareandservethefoodforconsumptionat homeorinarestaurant, todisposeoforutilizefoodwasteinasafe, environmentallysoundmanner. Gettingfoodtothetable,i.e.,thefoodsystem, accountsforapproximately17%ofthe81,300trillion Btu ofenergyconsumedannuallyintheUnitedStates (Table1).Approximately18%ofthisenergyis consumedforon-farmfoodproduction;82%isspent onfoodprocessing,transportation,marketingand preparation. MuchoftheenergyusedintheU.S.foodsystem comesfromfossilfuelslikecoal,petroleumand naturalgas.Thesearenon-renewableenergy resourcesthatwereformedmillionsofyearsago throughlong-termgeologicprocesses.Thecurrent humanpopulationofEarthisconsumingfossilfuels 100,000timesfasterthantheycanbeproduced. Thecombustionofthesefossilfuelsproduces environmentalpollutantsandgreenhousegases. Greenhousegasesinfluencethetemperatureof Earth'satmosphere;increasedquantitiesof greenhousegasesmightincreasethesetemperatures andaffectthestabilityofourenvironment.(Formore information,seeEES-72,GlobalClimateChange Primer.)Someoftheenvironmentalpollutants producedbyburningfossilfuelsaresulfurdioxide, carbonmonoxideandnitrogendioxide.Inaddition 1.ThisdocumentisEES-99,FloridaCooperativeExtensionService,InstituteofFoodandAgriculturalSciences,UniversityofFlorida. Publicationdate:May1993. 2.H.J.Whiffen,AgriculturalEnergySpecialist,EnergyExtensionService,AgriculturalEngineeringDepartment;L.B.Bobroff,Associate Professor,HomeEconomicsDepartment,CooperativeExtensionService,InstituteofFoodandAgriculturalSciences,UniversityofFlorida, GainesvilleFl32611. TheFloridaEnergyExtensionServicereceivesfundingfromtheEnergyOffice,DepartmentofCommunityAffairs,andisoperatedbytheUniversity ofFlorida'sInstituteofFoodandAgriculturalSciencesthroughtheCooperativeExtensionService.Theinformationcontainedhereinistheproduct oftheFloridaEnergyExtensionServiceanddoesnotnecessarilyreflecttheviewoftheFloridaEnergyoffice. TheInstituteofFoodandAgriculturalSciencesisanequalopportunity/affirmativeactionemployerauthorizedtoprovideresearch,educational informationandotherservicesonlytoindividualsandinstitutionsthatfunctionwithoutregardtorace,color,sex,age,handicap,ornational origin.Forinformationonobtainingotherextensionpublications,contactyourcountyCooperativeExtensionServiceoffice. FloridaCooperativeExtensionService/InstituteofFoodandAgriculturalSciences/UniversityofFlorida/ChristineTaylorStephens,Dean

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ManagingTheEnergyCostofFood Page2totheotherenvironmentalconcernsrelatedtothe productionofthesepollutants,theycannegatively affectthehumanbody'sabilitytobreatheandutilize oxygen.Theatmosphericconcentrationsofthese pollutantsarealreadyabovesafehealthstandardsin someplacesintheUnitedStates. Table1. EnergyconsumedintheU.S.foodsystem. Activity Percent1 EnergyUsed (Btu)2 On-farm Production 3.0% 2,400trillon Processing 5.4% 4,400trillon Transportation 0.5% 410trillon Wholesale/retail 2.6% 2,100trillon Preparationat homeor restaurant 5% 4,000trillon Total 16.5% 13,500trillon 1.Source:Dowling,1991. 2.Basedon1991U.S.energyconsumptiondata fromtheEnergyInformationAdministration,1992.Thispublicationprovidesinformationonhowto shopforandpreparemealsthatarenutritionallywell balancedandenergyefficient.Awell-planneddiet cancontributetolongtermhealthandahealthier globalenvironment.ENERGYFROMTHEFOODWEEATPlantsstoretheenergytheyreceivefromsunshine inleaves,stem,branches,rootsandfruit,througha processcalled photosynthesis.Theenergyinplants andtheanimalsthatconsumetheseplants,isstored aschemicalenergy,mainlyascarbohydrates,fats,oils andproteins.Thisfoodenergyismeasuredin kilocalories.Fatsandoilshave,onaverage,9 kilocaloriespergram(16,400Btuperlb);starches andproteinshaveabout4kilocaloriespergram (7,270Btuperlb).Accordingtothe1989 RecommendedDietaryAllowances,anaverage25-50 yearoldfemaleshouldeat1,800-2,600kilocaloriesof fueladay.Anaveragemaleinthesameagecategory requires32%morekilocaloriesaday(Table2).A person'sactualenergyneedsdependuponhis/her dailyactivities,weightandage. Table2. Recommendedenergyintakeforpeopleof averageheight,weightandactivity. Population Age(years) EnergyNeeds (kilocalories) Children 1-3 900-1800 Children 4-6 1300-2300 Children 7-10 1650-3300 Females 11-14 1500-3000 Females 15-18 1500-3000 Females 19-24 1800-2600 Females 25-50 1800-2600 Females 51+ 1500-2300 Males 11-14 2000-3700 Males 15-18 2100-3900 Males 19-24 2100-3900 Males 25-50 2500-3300 Males 51+ 1900-2700 Source:FoodandNutritionBoard,1989.ENERGYUSEDTOPROCESSTHE FOODWEEATNearlytwo-thirdsofthefoodsweconsumehave beenprocessedinsomeway.Foodisprocessedto makeitedibleand/ortopreserveitforsafeuseinthe future.Morethan64%oftheenergyusedtoprocess foodscomesfromfossilfuels(Table3). Sometimesfoodprocessingincreasesthenutrient valueoffoods.Mostlegumescontainanumberof toxinsandsubstancesthatinhibitdigestiveenzymes. Destructionofthesetoxinsandinhibitorsbyfood processorsincreasesthenutritionalvalueofthe proteinsinlegumes. Ontheotherhand,foodprocessingoften decreasesthenutrientvalueoffoods.Cooked spinachpreparedfromafrozenpackagestoredforsix monthshas50%less vitaminC and67%less thiamin thancookedspinachpreparedfromfreshspinach leaves. Riboflavin lossesincooked,frozenpeasare twiceashighasthosecookedfresh.Duringcanning, tomatojuicecanloseupto17%ofthe niacin and

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ManagingTheEnergyCostofFood Page340%ofthe carotene foundoriginallyinthefresh tomatoes(Table4). Producingcornonthefarmorinagardenuses Table3. EnergyresourcesusedintheU.S.food industry. Energysources % Electricityfrom1fossilfuels Coal 6.3% NaturalGas 1.2% Petroleum 0.3% Total 7.8% Electricityfromotherenergyresources2 3.2% NaturalGas2 45% Petroleum2 11% Other(e.g.,coal,bagasse)2 33% 1.Basedon1992U.S.energyconsumptiondata fromtheEnergyInformationAdministration,1992. 2.Source:1990projectionsfromSingh,1986. Table4. Nutrientlossesfromtomatojuiceduring canning. Nutrients Percentagelost VitaminC 10-65% Thiamin 0-27% Riboflavin 0-14% Niacin 0-17% Carotene 25-40% Source:Bender,1978.onlyabout15%ofthetotalenergyusedtoproduce, process,marketandcooka16-ozcanofsweetcorn. Thesamequantityoffrozencornrequires26%more energyifstoredeitheratthestoreorinthehome freezerforsixmonths(Table5).Ittakesmore energytomakethecanthanthepackagepaperfor thefrozencorn,butfrozenfoodstakemoreprocess anddistributionenergythancannedgoods. Whenseasonallyavailable,freshfoodsare typicallytheenergyefficientandnutritionalchoice. Theyfrequentlyhavehighernutritionalvalues becausetheyarenotprecooked,andlessfossilfuel energyisinvestedinthemsincetheyarenot processedorpackaged. Table5. Energyinputsforcanningandfreezingsweet corn. Energyinputs 16-ozcanof corn(Btu) 16ouncesof frozencorn (Btu) Home preparation 1,800 1,800 Shopping 1,200 1,200 Distribution: wholesale& retail 1,400 2,900 Transport 630 720 Packaging 4,000 2,700 Processing 1,000 3,800 Production 1,800 1,800 Total 11,830 14,920 AdaptedfromPimentel,1984.ENERGYUSEDTOTRANSPORTTHEFOOD WEEATBuyinglocally-producedfoodsavesenergy.On theaverage,1.5Btuofenergyareusedtomoveone poundonemile.Usingthisaveragefigure,4,050Btu ofenergyareusedtomoveoneheadoflettuce,at onepoundperhead,the2,700milesfromLos Angeles,California,toMiami,Florida;980Btuof energyareusedtotransportthesameproducethe 650milesfromPensacolatoMiami,Florida.Thatis anenergysavingsof76%. Buyingfoodproducedlocallycanimprovethe nutrientvalueoftheproduceeattenintwoways.To facilitateshipping,somecommoditiessuchas tomatoesarepickedwhentheyarestillgreen. Tomatoespickedbeforetheyarematurehave30% lessvitaminCwheneatenthanthoseharvestedwhen theyareripe.Tomatoespurchasedfromalocal growercanbepickedwhentheyareripebecausethey don'tneedtobeshipped.

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ManagingTheEnergyCostofFood Page4Second,foodsgenerallyareattheirnutritional peakatthetimeofharvest.Producethatsitsatroom temperatureafterpickinglosesnutrients.Thesooner thelettuceandcucumbersgetfromtheproducer's fieldtotheconsumer'srefrigerator,thehigherthe Table6.DirectenergyinputsintotheU.S.food systembyconsumers. Activity Percentage Consumershopping 1.9% Foodpreparationandcooking 4.8% Garbageandsewagedisposal 0.3% Total 7.0% AdaptedfromGreen,1978. nutrientvalueretention.Transportationtakestime; locallygrownproduceisoftenfresher. Foodcommoditiesproducedneartowhereyou livearetypicallytheenergyefficientandnutritional choice;lessenergyisinvestedintransportationand nutrientretentionishigher.Therefore,suchfoods representanenergyefficientchoicewhenseasonably available.ENERGYUSEDTOPREPARETHEFOODS WEEAT ShoppingTheconsumerhaspersonalcontrolover approximatelysevenpercentofthetotalquantityof fossilfuelsusedintheU.S.foodsystem(Table6). That'sanaverageenergyexpenditureof23million Btuperpersonperyearinvestedingroceryshopping andcooking.Useofprivatecarsforgroceryshopping consumes12billiongallonsofgasolineandemits131 milliontonsofcarbondioxide,734,000tonsofsulfur dioxideand22.5milliontonsofcarbonmonoxide everyyear. Consumerscanreducetheenergyinvestmentin theU.S.foodsystembyreducingtheamountof unnecessarypackagingtheypurchaseinstoresor restaurantsandselectingproductspackagedin recycledmaterials.Forexample,moreenergyisused tomaketheplasticpouchfortwocrackersthanis usedtomakethecrackers.Approximately7,000Btu ofenergyarerequiredtomakeanaluminumsoda canfrom"raw"materials;approximately2,500Btuof energyarerequiredtomakethesamecanfrom recycledaluminum(Table7).(Formoreinformation, seeEES-77:WastePreventionSavesEnergy;and EES-73:EnviroshoppingEnergyConsiderations.) Table7. Energyusedtomakepackaging. Type From"raw" materials (Btu/pound) Fromrecycled materials (Btu/pound) Aluminum1 200,000 71,000 Glass2 7,700(15% cullet) 6,500(100% cullet) Plastic(HDPE)2 36,500 2,300 Packaging Paper2 24,000 22,000 1.WorldResourcesInstitute.1992.The1992 InformationPleaseEnviromentalAlmanac.Houghton MifflinCompany,NewYork,N.Y.10003 2.OfficeofTechnologyAssessment.1989.Facing America'sTrash:WhatNextforMunicipalSolidWaste. OTA-0-424.PreparingFoodVitaminC,thiaminandriboflavinarewatersolublevitamins:theyleachoutofproduceasitis washed.Thelongerthesoakandthehotterthe water,thefasterthenutrientlossandthegreaterthe energyinvestmentinpumpingandheatingwater. Washproducethoroughlybutquicklyincoldwaterto savenutrientsandenergy. Someofthenutrientsinfruitsandvegetablesare concentratedintheouterleavesorlayers.For example,theoutergreenleavesonaheadofcabbage have90mgofvitaminCper100gramsofcabbage whilethewhiteleavesinsidehave45mgofvitaminC per100grams.Thepeelonapearhastwiceasmuch vitaminCasthefruit'sfleshandisanexcellent sourceofdietaryfiberasaretheedibleouterlayers ofmanyhorticulturalproducts.Don'tthrowawaythe outerlayersofproduce.Reducingthequantityof wastegeneratedduringfoodpreparationcansave nutrientsandenergyanddecreasethehome'sweekly contributiontothelandfill.

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ManagingTheEnergyCostofFood Page5CookingCookingisthemostenergyintensivestepinfood preparation,andovercookingisthegreatestnutrient thief.Overcookingfoodcancausevitaminlossesof upto100%.Vegetablesaremostnutritiousandalso themostpalatableiftheyarecookedtothejust-crisp point. Ingeneral,gasstoveswithelectricignitionare moreenergyefficientand,therefore,lessexpensiveto operate,thanelectricstoves.Atypicalelectricstove puts20Btuofheatenergyintothefoodforevery100 Btuof primary energyconsumedatthepowerplant (20%efficient);gasstovesare33%efficient. Electricinductionrangesuseanalternating positiveandnegativechargetoheatmagneticpots andpans.Mostoftheheatenergyisabsorbedby thesepotsandpansinsteadoftherangeitself; inductionrangesaremoreenergyefficientthan regularelectricrangesbutnotasenergyefficientas microwaveovens. Microwavestransferenergydirectlytowaterand fatmoleculesinfoods.Thesemoleculesabsorbthe energyandproduceheat.Mostoftheheatenergy endsupinthefoodinsteadofthemicrowaveovenor thecookingdish.Whencookingsmallamountsof food,microwaveovenscanreducecookingenergyuse byone-half. Microwaveovenssavenutrients,too,becausethe shortercookingtimeislessdestructiveofnutrients. Cookingcabbageonaconventionalrangecanresult inthelossof75%ofthevitaminC;cookingrapidly inapressurecooker,50%;microwavecooking,only 10%.DisposalIntheUnitedStates5-10%oftheediblefood purchasedinagrocerystoreisthrownaway.This disposalwastestheenergyusedtogrow,process, packageandtransportthefoodandtheenergyused todisposeofthegarbage.Approximately1,500 trillionBtuofenergyarewastedinthismannerevery yearintheUnitedStates. Recyclingisanenergyefficientwastedisposal option.Compostyourorganicwastesandusethe composttosupplyyourlandscapeplantsandgarden vegetableswiththenutrientsandsoilorganicmatter theyneed.Participateinarecyclingprogramforyour aluminum,steel,glass,plasticandpaperpackaging materials.(Formoreinformation,seeCIR-958: BackyardCompostingofYardWaste ;AE-27: ConvertingYardandKitchenWasteintoCompost; EES-73: EnviroshoppingEnergyConsiderations.)EnergyEfficientFoodTips Think"environment"whenmakingpurchasing decisions. Choosefreshfoodsgrownlocallywhenever possible. Minimizethenumberoftimesyoudrivetothe storebymakingalistofwhatyouneedduring theweek. Matchtheburnerandthepansizetothequantity offoodtobecooked. Theflameonagasstoveshouldbeblue;ayellow flameindicatesthatthereisnotenoughairfor energyefficientcombustion. Considerpurchasingagasovenwithanelectric ignitionthenexttimeyougoshoppingforanew stove. Usetheself-cleaningfeatureonanovenright afterbakingorbroilingtousetheheatalready built-upintheoven. Avoidceramictopelectricresistanceranges;they aregenerallylessenergyefficientthanranges withtheresistanceelementsexposed. Pre-heatanovenforonly5-8minutes. Opentheovendoorwhilecookingasfewtimes aspossible.Theairtemperaturedrops25-50F everytimethedoorisopened. Defrostfoodsintherefrigeratorbeforeyoubegin topreparethem.Frozenfoodsneedmoreenergy tocookthancompletelythawedfoods.A defrostedroastrequires33%lesscookingtime thanonethatisstillfrozen. Useaslittleliquidaspossiblewhencookingto conservebothenergyandnutrients. Savethejuicesthatcookoutoffoodsanduse themtomakesoups.Foodjuicesfrequently

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ManagingTheEnergyCostofFood Page6containagreatdealofthenutrientsthatwere originallyinthefoodwhenitwasfresh. Cutfoodsintosmallpiecestodecreasecooking time. Maximizesurfaceareatoheatsource,minimize depthandcookforasshortatimeaspossibleto conservefoodnutrients.Thegreatestlossesof vitaminCandthiamintakeplacewhenfoodis kepthot. Whenshoppingforkitchenappliances,lookfor andcomparetheenergyefficientratingsonthe EnergyGuidestickers.Energyefficientappliances savemoney,onalongtermbasis,becausethe electricbillforoperatingtheapplianceisless.GLOSSARYBtu:Britishthermalunit;approximatelythe energyinoneburningwoodenmatch. Cullet:Recycledglass. Kilocalories:Aunitusedtomeasuretheenergy infood;1kcal.=4Btu;thereareapproximately 40kcal.inonetablespoonofsugar. Milligram:0.001grams;0.0000022lbs. Niacin:VitaminB3;watersoluble;partofa coenzymevitaltoobtainingenergyfromglucose; preventspellagra. Photosynthesis:Achemicalreactionoccurringin greenplantsthatmakescarbohydratesfrom carbondioxideandwater,usingthesun'senergy topowerthereaction. Primaryenergy :energyavailablefromconversion oftheoriginalfuel,suchaspetroleumornatural gas,ratherthanfromasecondaryform,suchas electricity. Riboflavin:VitaminB2;watersoluble;helps transferenergyfromonecompoundtoanother. Thiamin:VitaminB1;watersoluble;prevents beriberi;helpsreleaseenergyfromfood. VitaminC :Ascorbicacid;requiredforthe productionandmaintenanceofcollagen,a proteinsubstancethatformsthebaseforall connectivetissues.REFERENCESBender,A.E.1978. FoodProcessingandNutrition. AcademicPress.Orlando,FL32887. Cook,G.1989. CookingApplianceSelectionand Operation:ContemporaryViewsonFunctionand Efficiency.EES-56.UniversityofFlorida, Gainesville,FL32611. Dowling,J.1991. AgriculturalUsesofEnergyIn:The EnergySourcebook:AGuidetoTechnology, ResourcesandPolicy.EditedbyR.HowesandA. Fainberg.AmericanInstituteofPhysics335E. 45thStreet,NewYork,NY10017-3483. EnergyInformationAdministration.1992.Monthly EnergyReview.DOE/EIA-0035(92/09) September. FoodandNutritionBoard.1989.Recommended DietaryAllowances.NationalAcademyof Sciences,NationalResearchCouncil. Washington,DC20009. Green,M.B.1978. EatingOil:EnergyUseinFood Production.WestviewPress.Boulder,CO80301. Martin,E.A.andA.A.Coolidge.1978. Nutritionin Action,FourthEdition .Holt,Rinehartand Winston.NewYork,NY10018. OfficeofTechnologyAssesment.1989. Facing America'sTrash:WhatNextforMunicipalSolid Waste? OTA-0-424. Pierotti,A.,A.KeelerandA.Fritsch.1977. Energy andFood.CenterforScienceinthePublic Interest.1755SouthStreetNW,Washington,DC 20009. Pimentel,D.andC.W.Hall.1984. FoodandEnergy Resources.AcademicPress.Orlando,FL32887. Singh,R.P.1986. EnergyinFoodProcessing. ElsevierSciencePublishingCompany,Inc.New York,NY10017. U.S.EnvironmentalProtectionAgency.1992. The Consumer'sHandbookforReducingSolidWaste

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ManagingTheEnergyCostofFood Page7EPA530-K-92-003.401MStreetSW, Washington,DC20460. Whitney,E.N.1982. Nutrition,SecondEdition .West PublishingCompany.St.Paul,MN55165. WorldResourcesInstitute.1992. The1992 InformationPleaseEnviromentalAlmanac HoughtonMifflinCompany,NewYork,N.Y. 10003.