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Mohareb E Heller M Novak P Goldstein B Fonoll X and Raskin L (2017) Considerations for reducing food system energy demand while scaling up urban agriculture Environmental Research Letters 12 (12) 125004 ISSN 1748shy9326 doi httpsdoiorg1010881748shy9326aa889b Available at httpcentaurreadingacuk74000

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LETTER

Considerations for reducing food system energy demandwhile scaling up urban agriculture

Eugene Mohareb17 Martin Heller2 Paige Novak3 Benjamin Goldstein45 Xavier Fonoll6 andLutgarde Raskin6

1 School of the Built Environment University of Reading Reading United Kingdom2 Center for Sustainable Systems University of Michigan MI United States of America3 Department of Civil Environmental and Geo-Engineering University of Minnesota MN United States of America4 Division of Quantitative Sustainability Assessment Technical University of Denmark Denmark5 School for Environment and Sustainability University of Michigan MI United States of America6 Civil and Environmental Engineering University of Michigan MI United States of America7 Author to whom any correspondence should be addressed

OPEN ACCESS

RECEIVED

15 September 2016

REVISED

21 August 2017

ACCEPTED FOR PUBLICATION

25 August 2017

PUBLISHED

5 December 2017

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E-mail emoharebreadingacuk

Keywords urban agriculture energy food systems resource efficiency industrial ecology local food foodndashenergyndashwater nexus

AbstractThere is an increasing global interest in scaling up urban agriculture (UA) in its various forms fromprivate gardens to sophisticated commercial operations Much of this interest is in the spirit ofenvironmental protection with reduced waste and transportation energy highlighted as some of theproposed benefits of UA however explicit consideration of energy and resource requirements needsto be made in order to realize these anticipated environmental benefits A literature review isundertaken here to provide new insight into the energy implications of scaling up UA in cities inhigh-income countries considering UA classification directindirect energy pressures andinteractions with other components of the foodndashenergyndashwater nexus This is followed by anexploration of ways in which these cities can plan for the exploitation of waste flows forresource-efficient UA

Given that it is estimated that the food system contributes nearly 15 of total US energy demandoptimization of resource use in food production distribution consumption and waste systems mayhave a significant energy impact There are limited data available that quantify resource demandimplications directly associated with UA systems highlighting that the literature is not yet sufficientlyrobust to make universal claims on benefits This letter explores energy demand from conventionalresource inputs various production systems waterenergy trade-offs alternative irrigation packagingmaterials and transportationsupply chains to shed light on UA-focused research needs

By analyzing data and cases from the existing literature we propose that gains in energy efficiencycould be realized through the co-location of UA operations with waste streams (eg heat CO2greywater wastewater compost) potentially increasing yields and offsetting life cycle energydemands relative to conventional approaches This begs a number of energy-focused UA researchquestions that explore the opportunities for integrating the variety of UA structures and technologiesso that they are better able to exploit these urban waste flows and achieve whole-system reductions inenergy demand Any planning approach to implement these must as always assess how context willinfluence the viability and value added from the promotion of UA

Introduction

Urban agriculture (UA) has been undergoing a globalresurgence in recent decades with cities in bothadvanced and emerging economies implementing

programs to encourage its use (Mok et al 2013Orsini et al 2013 Hamilton et al 2013 Vitiello andBrinkley 2013) This renewed interest has led to theexploration of the extent to which UA could beexpanded including a number of investigations that

copy 2017 IOP Publishing Ltd

Environ Res Lett 12 (2017) 125004

estimate the potential for UA to meet local fooddemand for example Grewal and Grewal (2012)McClintock et al (2013) and Goldstein et al (2017)suggest provision of total food demand (former) andvegetable demand (latter two) of 42minus177 5and 32 respectively Expanding UA is expected toimprove local sustainability includingbenefits to social(addressing food deserts building community cohe-sion or higher intake of fresh produce) and economic(cash crop production reduced food costs) facets ofcities The environmental aspects associated with thenet direct and indirect energy implications of UA willbe the primary sustainability focus area of this research

Part of the rationale for reconsidering UA has beenits potential environmental benefits including reduc-tions in energy demand throughout the food supplychain As a result UA has been included in green-house gas (GHG) mitigation strategies for cities (Arupand C40 Cities 2014) and broader urban sustainabilityagendas through multi-city agreements and partner-ships suchas theUKrsquosSustainableFoodCitiesNetworkand the Milan Urban Food Policy Pact the latter ofwhich includes 100 large cities around the world (Milan2015 Andrews et al 2017) However when consider-ing the complex interplay between food productionenergy requirements and water availability (ie thefoodndashenergyndashwater nexus) the ability of UA to reduceenergy demand is unclear

This review article examines energy use in thefood system explores the opportunities that exist forhigh-income cities to increase the energyresourceefficiency of this overall system through UA andproposes changes that could be made in the plan-ning of cities to enable greater reductions in energydemand with a focus on the United States The scopeextends beyond the frequently-assessed topic of trans-portation into topics such as embodied energy ofproduction inputs (ie water nutrients heating CO2)reduction in packaging storage and processing needsThis review aims to provide a point of reference forenergy considerations that should be made if UA isgoing to provide a greater share of the global foodsupply

Classifying urban agriculture

Estimating the current scale of UA is difficult and variesbased on how it is defined for example Thebo et al(2014) estimate that there were 67 megahectares (Mha106 ha) of UA8 globally in 2000 (5 of global arableland in that year Food and Agriculture Organiza-tion 2010 table A4) with roughly 13 of the UA areabeing irrigated Their quantification includes spatial

8 Thebo et al (2014) define urban agriculture as the spatial coinci-dence of agricultural areas with urban extents with populations over50 000

data where agricultural areas and urban boundarieswith populations greater than 50 000 overlap most ofwhich would be classified as peri-urban9 agricultureand would not capture small-scale operations such asresidential gardens vacant lots or building-integratedproduction (eg balcony gardens rooftop gardens)Inclusion of peri-urban agriculture would produce asubstantially higher estimate of UA than the area thatis currently used in these more commonly-perceivedforms of UA Looking at the scale of some of thesetypes of UA Taylor and Lovell (2012) examine thetotal area of UA in the city of Chicago using 2010 aerialphotographs They find that approximately 004of Chicagorsquos land area of 606 km2 was being usedfor urban agriculture of this nearly half (45) wasin residential gardens while most of the remainderwas in vacant lots (27) and community food gardens(21) To provide a sense of scale of the opportunityto expand urban agriculture a 2000 study of vacantland in US cities finds that those in the Midwest had anaverage of 12 vacant land and a national average of15 (Pagano and Bowman 2000)10

As alluded to above UA manifests itself in a num-ber of different structures and locations within thebuilt environment Attempts have been made in theliterature to classify UA Mok et al (2013) identifythree distinct scales of agriculture in urban systemsThese are (in order of decreasing size) small com-mercial farms and community-supported agriculturecommunity gardens and backyard gardens All of theseUA scales differ in their structure inputs and pro-ductivity as a result their net impact on life cycleenergy demand and other resource inputs also variesGoldstein et al (2016b) further classify UA to con-sider structure and inputs in a taxonomic schemebased on the conditioning required for the growingenvironment (temperature light and CO2 control)and integration within the surrounding urban system(building integrated or ground based) They claim thatboth features are important to UA energy regimeswith space conditioning (particularly the need for heat-ing in cold climates) being an essential considerationalong with the potential for building integrated farmsto utilize dissipative heat and CO2 to offset productioninputs

A broad classification of UA is provided in table1 which is roughly ordered by scale and sophisti-cation of production It should be highlighted thatwhile the preservation of peri-urban agriculture canbe captured in assessments of UA the focus ofthis review is on approaches to scaling up UA that

9 Peri-urban agriculture refers to agricultural production that occursat the urbanndashrural interface10 Data include vacant land with and without abandoned buildingsChicago did not provide data for this study to allow a direct com-parison hence the average area for Midwest cities is provided hereas well it is not being suggested here that all vacant land be allocatedto or are suitable for UA

2


Table 1 Type of urban agriculture associated with structurelocation of production potential beneficial energy impacts relative to intensiverural agriculture and requirements for upscaling

Type of urban

agricultureAuthorsrsquo definition Potential direct energy

benefitsConsiderations for successful

upscalingSources

Residentialgardens

Open air or protected11 food

production occurring within

the boundaries of a residential

property primarily for

personal consumption

∙ Non-mechanized

inputs

∙Reduced cold

chainretail

requirement (onsite

end-consumption)

∙ Knowledge dissemination

for production preservation

∙ Regulations for application

of fertilizers pesticides

∙ Appropriate crop selection

(Kulak et al 2013

Altieri et al 1999)

Allotment andcommunitygardens12

Open air or protected food

production occurring upon

community or municipally-

owned land primarily for


∙ Non-mechanized

inputs

∙ Reduced cold

chainretail

requirement

∙ Municipal allocation of

green space

∙ Expedited application

approval to facilitate utility

connection

∙ Mulch from municipal

greenspace maintenance

(Leach 1975)

Rooftopbalconyagriculture


production occurring on

structures built for other

primary functions for either

personal consumption or

commercial availability

∙ Thermal transfer

from rooftop

∙ Improved yield

∙ Improved building

insulation

∙ Onsite waste

diversion

∙ Building code consideration

(structural utilities)

(Sanye-Mengual et al

2015 Saiz et al 2006

Specht et al 2013

Grard et al 2015

Orsini et al 2014)

Industryresidence-integratedgreenhouse

Controlled-environment food

production with supplemental

heating integrated into


primary functions that involve

purpose-built infrastructure

for yield improvement

towards commercial

availability

∙ Waste heatCO2utilization

∙ Improved yield

∙ Inventory of urban resource

streams

∙ Zoning by-laws to enable

co-location of agriculture with

resources

(Zhang et al 2013)

Vertical farms Controlled-environment food


heating in multi-story

structures developed with the

primary function of crop

production for commercial

availability Generally located

within urban boundaries

∙ Onsite waste

diversion (eg

waste-to-feed for

livestock operations)

∙ Potential for on-site

nutrient cycling

∙ Improved yield

∙ Building code changes


∙ Innovations in lighting

agriculture system integration

in built environment

∙ Low-carbon grid due to

expected substantial energy

requirements

(Despommier 2013

Hamm 2015)

Peri-urbanagriculture

Open air protected or

supplemental heat

environment food production

at the urban-rural interface

Generally for commercial

availability but may include

subsistence agriculture in

developing-world contexts

∙ Preservation of

high-yielding prime

agricultural land

∙ Legal protection of

peripheral farmlands from

incompatible urban

development

(Francis et al 2012

Krannich 2006)

are integrated into the built environment ratherthan on maintaining existing agricultural land in theurban periphery Hence large scale conventional peri-urban agriculture is beyond the scope of inquiryhere

11 Protected food production refers to enclosed environments(eg with polyethylene or glass) that are not climate-controlledcontrolled-environment food production includes both protectedenvironments and those with supplemental heat12 Urban or peri-urban agricultural space designated and protectedby municipalities or community groups for non-commercial pur-poses

Energy consumption in the food system andurban agriculture

The modern food system encompasses a broad collec-tion of energy end-users Starting from the agriculturalphase through transportation of food to retailers andhouseholds and culminating in waste handling thecurrent predominantly linear structure of the foodsystem is highly dependent on energy inputs for itsoperations of production processing distributionconsumption and disposal of food products (Pimentelet al 2008) Examining the US case the USDA ERS

3


Agriculture13

Processing17

Packaging5

Transportation3Wholesale Retail

15

Food Services18

Households29

Total = 14760 PJ

Figure 1 Energy consumption in the US food system in 2002 (adapted from Pelletier et al 2011 from Canning et al 2010)

Table 2 Energy and water demand per unit yielded for various tomato production systems (modified from Goldstein et al 2016a)

Production system Irrigation water (m Mgminus3) Direct and indirect energy demand (MJ Mgminus1)

Ground-based non-conditioned (two cases) 50 74 6500 2600Ground-based conditioned 65 33 000Building-integrated non-conditioned 68 3300Building-integrated conditioned 9 56 000Conventional (conditioned) 2 10 000

(2010) estimates that nearly 144 of total nationalenergy consumption in2002was food-relatedAbreak-down of this consumption is provided in figure 1

The majority of energy use in the food systemoccurs beyond the farm gate the United NationsFood and Agriculture Organization (FAO) estimatesthat over 75 of energy use in the food system ofhigh-income nations occurs after cultivation (Foodand Agriculture Organization 2013) This is consistentwith the 2002 US analysis in figure 1 which sug-gests that the post-agricultural energy use share is over87 However the potential for UA to impact energydemand beyond production is substantial (eg packag-ing processing transportation waste management) asdiscussed below In addition figure 1 excludes wastew-ater and food waste treatment therefore a completeconsideration of energy use associated with the expan-sion of UA will require an examination of not onlyfood productionbut also energy inputs across the entirefood system including waste handling and treatmentChanges in energy use relative to the status quo mustalso investigate the foodndashenergyndashwater nexus to vali-date theenvironmental case for scalingupUAandavoidany unintended shift of impacts from one resourcesystem (ie energy) to another (ie water)

Energy benefits of urban agricultureProponents suggest a number of energy-related ben-efits are realized through the reintroduction of foodproduction within cities (Howe and Wheeler 1999Garnett 1997 Smit and Nasr 1992 Kulak et al2013) Studies most commonly highlight savings intransportation energy reduced storage requirements

at the wholesaleresale level and energy inputs of foodwasteloss along the supply chain but also includeadditional biomass provision from silviculture (ieto offset energy imports Smit and Nasr 1992) eas-ier exploitation of resource use (Zhang et al 2013)and lower resource-intensity of production (Kulaket al 2013) Meanwhile peri-urban agriculturecan preserve higher-yielding prime agricultural land(Krannich 2006 Francis et al 2012) which has thepotential toprovide less resource-intensiveproductionLooking at more sophisticated integrated operations(vertical farms integrated greenhouses) exploitedwaste streams (CO2 heat macronutrients) could off-set energy requirements that are required for providingthese inputs in conventional operations (Despommier2013 Zhang et al 2013) Additionally if the distributednature of UA can be supported by a similarly dis-tributed energy infrastructure system foodagriculturewaste can be digested locally to generate biogas for heator electricity production further decreasing the energyfootprintofUAEnergy-relatedbenefitsassociatedwiththe various structureslocations of UA have also beendescribed in table 1 (excluding transportation)

Interactions with other components of theurban foodndashenergyndashwater nexus

Urban agriculture has the potential to affect energy-related components of the foodndashenergyndashwater systemwithin urban boundaries and beyond Suggestionsof positive and negative impacts both within andbeyond the urban boundary are presented in table 2

4


It is important to note that energy demand for ser-vices required in UA can differ from those providedthrough open-field agriculture An exploration of lit-erature that can provide greater insight on how thesedifferent UA approaches can influence energy needsfollows

Energy demand for UA water systemsEnergy demand in irrigation systems are a noteworthycomponent of scaled-up UA that must be consid-ered in order to avoid inadvertently increasing demandrelative to conventional open-field systems Irrigationsystems in an open-field agricultural setting are rela-tively low-energy when compared with potable urbanwater systems that could be used in UA in one studyopen-field irrigationenergydemand is estimatedat 063MJ mminus3 water (Esengun et al 2007 used in the absenceof a similar US case study) However in a UA systempotable water may be used for irrigation and generallyrequires substantially more energy for treatment withthe Electric Power Research Institute (2002) suggestingan estimate of 13 MJ mminus3 and 17 MJ mminus3 for pub-lic utilities using surface and groundwater respectively(including distribution) for a hypothetical 10 milliongallon per day treatment plant Meanwhile Racov-iceanu et al (2007) estimate energy demand at 23minus25MJ mminus3 treated water used in the City of Torontorsquoswater treatment The Racoviceanu et al (2007) studyconsiders a surface water source and includes chem-ical fabricationtransportation treatment and onsitepumping though most of total energy intensity(sim70) is attributable to untreated and treated waterpumping Data onMassachusettsrsquo 2007 energy demandfor water treatment and distribution suggests an aver-age value of 14 MJ mminus3 (US Environmental ProtectionAgency 2008) whereas Californiarsquos 2005 report onthe energy-water relationship provides estimates of 14MJ mminus3 and 97 MJ mminus3 for Northern and SouthernCalifornia respectively (range attributable to differ-ences in energy required for conveyance from sourceto treatment facilities Klein et al 2005) This latterCalifornia report also suggests that when desalinationoptions are employed in water treatment an additional93minus157 MJ mminus3 and 37minus93 MJ mminus3 are requiredfor seawater and brackish groundwater respectivelyIt is worth noting that depth of groundwater sourcepumping requirements for surfacegroundwater andon-farm treatment will influence the energy demandand could bring this figure closer in line with that fromwater utilities

The types of secondary energy used can also varyfor different types of irrigation influencing both costoverall energy efficiency and GHG emissions Forexample Ontario Canadarsquos field crop irrigation is typ-ically powered by diesel systems while greenhouseirrigation is generally powered by electricity (Carol2010) Diesel has an emissions intensity of 74 kgCO2e GJminus1 while electricity grid GHG intensity in

Ontario was 14 kg CO2e GJminus1 in 2014 (IPCC 2006chapter 3) For comparison US electricity emissionsintensities ranged from 1 to 266 kg CO2e GJminus1 in 2012(US EPA 2015)

Waterenergy trade-offs for UA production methodsWater use can be mitigated through the use of morewater-efficient growing systems (such as hydroponicsystems) though these can result in increased energydemand in pumping and lighting and associated GHGemissions For example hydroponic13 systems havebeen shown to have lower water demand than soil-based production in addition to avoiding the needfor a solid growing medium and the associated energyinputs of its provision (Albaho et al 2008) HoweverBarbosa et al (2015) have modeled energy and waterdemand for hydroponic and conventional productionsystems for lettuce while water demand was reduced by92 (250 to 20 l kgminus1 yminus1) energy demand increasedby 8100 (1100 to 90 000 kJ kgminus1 yminus1) due primar-ily to heating and cooling loads (74 000 kJ kgminus1 yminus1)artificial lighting (15 000 kJ kgminus1 yminus1) and circulatingpumps (640 kJ kgminus1 yminus1)

Focusingonenergy Shiina et al (2011) studyhydro-ponic urban lsquoplant factoriesrsquo (temperature controlledartificial lighting and humidity controlled) in Japanand show that the energy intensity of the productionresulted in estimated greenhouse emissions of 64 kgCO2e kgminus1 lettuce despite the operationrsquos high yieldsContinuing to use GHG emissions as a proxy for energydemand this compares with estimates of 02 and 09kg CO2e kgminus1 for lettuce from Michigan hoop housesand California open-field lettuce production (Plaweckiet al 2014) and ranges between 024minus262 kg CO2ekgminus1 for lettuce from European open field and hot-house production (Hospido et al 2009) MeanwhileGoldstein et al (2016a) compared cumulative energydemand of rooftop hydroponic greenhouse tomatoesand lsquoconventionalrsquo production and find the former tobe roughly ten times as energy intensivewith importantimplications for carbon footprint However switchingenergy source from the Massachusetts electricity gridto hydroelectric or solar PV makes rooftop hydroponicgreenhouse production less carbon intensive than con-ventional production

These demonstrate that are potential for trade-offswhenaddressingenvironmental footprints throughUAif focusing on a single performance metric (ie wateralone) Though as hydroponic growing systems canbe used in controlled protected and open-field grow-ing systems and with a wide selection of hydroponictechnology options available variation can be expectedin the yields and energy demand of hydroponic oper-ations this introduces uncertainty in applying these

13 Hydroponic systems are those that involve the culture of plantsin the absence of soil in a nutrient-supplemented water medium(lsquoHydroponicsrsquo in Anonymous 2017)

5


figures to specific contexts but underscores the needfor careful consideration in designing for energy andwater demand reduction

Alternative irrigation sourcesUrban agricultural systems provide an applicationfor rainwater collection as well as blackgreywater14all of which could reduce wastewater volumes andstormwater runoff and potentially improve surfacewater quality and decrease net energy use as a result (iedue to theavoidanceofUAirrigationwithpotablewaterand downstream wastewater treatment) As exampleswastewater treatment in California and Massachusettsis estimated to require on average 17 and 24 MJ mminus3respectively (US Environmental Protection Agency2008 Klein et al 2005) This has the potential to bereduced if conveyance and treatment requirementsare avoided through application of wastewater in UAFurther if stormwater can be diverted from treat-ment plants to UA in jurisdictions using combinedsewer systems energy demand as well as pollutantsto receiving bodies could be reduced In an extremecase substantial diversion of rainwater for UA fromlakes and rivers that ordinarily receive it could con-tribute to localregional ecosystem decline or surfacewater quality issues (Goldstein et al 2016a) Finallydepending on how UA is managed runoff from openfield urban farms could result in increased nutrientloads being passed down to receiving bodies or down-stream wastewater treatment plants (Pataki et al 2011)Upscaling UA could result in this being an additionalsource of non-point pollution for consideration by citymanagersplanners

Packaging materialsThe use of packaging materials can also potentially beavoided in UA operations in instances of productionfor personal consumption or within shorter distribu-tion chains such as when food is sold directly by theproducer (Garnett 1999) For example the climateimpacts of the embodied energyof polyethylene tereph-thalate clamshells and polystyrene trays that are oftenused in tomato packaging (again using carbon as aproxy for energy use) were estimated to be 25 and100 greater respectively per unit mass of tomatowhen compared to loose packaging (US Environmen-tal Protection Agency 2010) Still the authors notedthatmodifiedatmospherepackagingusingplasticshavebeen shown to increase shelf life by two or three timeswhich may reduce waste and consequently GHGsassociated with tomato production and disposal Thiswaste reduction could then offset the embodied energyneeded for the packaging material that provides thisadded shelf life

14 Blackwater refers to wastewater conveying faeces and urine whilegreywater includes other wastewater streams from human use thatdo not (ie dishwater shower water)

The use of packaging does not need to be anall or nothing proposition employing some packag-ing for various meal components can result in a netenergy savings (relative to lsquotypicalrsquo packaging con-figurations) when accounting for avoided waste andmarginal energy requirements semi-prepared mealsexamined by Hanssen et al (2017) were slightly moreenergy efficient when compared with those preparedfrom scratch It is generally important to recog-nize the embodied energy of the food products andpackaging materials being considered higher embod-ied energy food products (cheese beef bread) moreeasily justifying the additional energy inputs asso-ciated with packaging than unprocessed fruits andvegetables (Williams and Wikstrom 2011) Similarlythe application of plastic films and containers maybe more easily justified when compared with moreenergy-intensive materials such as steel aluminum orglass

Transportation and supply chain considerationsWhile UA and other forms of localization are oftenintuitively thought to reduce life cycle energy demandthe reality is more complicated (Webb et al 2013)Supply chains crossing a variety of artificial jurisdic-tional boundaries may in fact be more direct thanthose created by constraining agriculture within aregionstate depending on the product consump-tion point and regional characteristics (Nicholsonet al 2015) Broad-scale localization of agriculturehas the potential to increase transportation energyas well as associated GHG emissions relative to theconventional supply chain if definitions of local andimplications for modified supply networks includ-ing transport modes are not carefully consideredIndeed a commonly cited reason to pursue UA is toreduce energy-related impacts associated with trans-portation Estimates of transportationrsquos contributionto the food systemrsquos energy demand and GHG emis-sions have been estimated at approximately 10 orless (Weber and Matthews 2008 USDA ERS 2010Garnett 2011)

Numerous studies from the literature (Coley et al2009 Edwards-Jones et al 2008 Pirog et al 2001) havechallenged the common assumption that lsquolocalizingrsquofood production results in reduced transport energyuse and GHG emissions and effects on distributionnetworks need to be evaluated on a case basis to justifysuch a claim For instance transport-related impactsfor cheese shipped 20 000 km from New Zealand toconsumers inEnglandbyboatweredominatedby road-freight and consumer automobile use highlightingthe limitations of singular focus on transport distance(Basset-Mens et al 2007) The GHG implications ofexternal energy inputs to support year-round urbanfood production and their ability to overwhelm gainsachieved through reduced distribution distances mustbe considered in the context of upscaling of urban foodproduction

6


Urban heat island mitigationThe predominance of dark (low-albedo) surfaces incities results in the absorptionof solar radiation andele-vated temperatures in and around urban areas raisingthe demand for cooling energy (the urban heat islandeffect Oke 1973) Urban agriculture could play a rolein attenuating this phenomenon by increasing surfacealbedo and the cooling effect of plant evapotranspi-ration (Ackerman et al 2014) Vegetation situated onbuildings has been shown to reduce individual build-ing cooling demands in Toronto Canada MadridSpainandLaRochelle France (Bass andBaskaran2001Saiz et al 2006 Jaffal et al 2012) Ackermann and col-leagues estimated that scaling up UA in New York Citycould reduce the local urban heat island by 22minus44(sim1 C) mitigating energy demands for cooling (Ack-erman 2012) The importance of this ancillary benefitof UA could become more important with the increas-ing frequency and severity of heat waves under likelyclimate change scenarios (Jansson 2013)

Impact of type of production system

Assuming UA may involve the use of protective struc-tures or controlled environments it is relevant toconsider the energy demand associated with such struc-tures Generally speaking open-field and protectedagriculture (eg hoop houses with no supplementalheating)havebeen found to require lower energy inputsthan heated systems (eg heated greenhouses) Studiesfocusing on open-field conventional tomato produc-tion in the US and the Mediterraneanhad energy inputsfor production of 140ndash280 MJ Mgminus1 (Brodt et al 2013Tamburini et al 2015) An average of three Moroc-can protected tomato operations had energy inputsof diesel and electricity for fertigation and pesticideapplication of 460 MJ Mgminus1 (Payen et al 2015) Withhothouse operations energy input can increase furtherwith a selection of studies focusing on tomato cultiva-tion showing energy inputs ranging from 425 28 50076 000 MJ Mgminus1 for case studies in Northern ItalyFrance and Iran respectively (Heidari and Omid 2011Boulard et al 2011 Almeida et al 2014) In the Frenchcase heated operations required six times more energyper unit of weight than the protected system (Boulard etal 2011) Goldstein et al (2016a) found similar patternsof variation for tomatoes depending on productionmethod with resource requirements presented intable 2 (modified here to present consistent units)

Nevertheless studies that directly comparecontrolled-environment growing with open-field agri-culture for certain crop typespresent amixedpicture Inone study Martınez-Blanco et al (2011) found that lifecycle cumulative energy inputs per Mg of protectivestructure greenhouse tomatoes produced in Catalo-nia was 13 greater when compared with open-fieldproduction (considering operations using mineral fer-tilizer inputs only) The additional energy demand

in the greenhouse operations is dominated by thegreenhouse structure in spite of some savings realizedthrough reduced cultivation-stage fertigation infras-tructure nursery plants and irrigation needs Howeverin an Indonsian case study Kuswardhani et al (2013)found that energy demand per unit mass was higherfor open-field tomato when compared to protectivestructure greenhouses but lower for lettuce this isattributed to higher fertilizer and pesticideherbicideneeds for open-field tomatoes (predominantly thelatter) whereas open-field lettuce had lower energyrequirements in spite of this higher demand (andhigher labor inputs) due to the substantial electricityrequirements for the drip irrigation system used in thegreenhouse lettuce Their study did not include theembodied energy of the greenhouse structure

Studies for tomato production in Antalya Turkeysuggest that energy requirements per kg yielded forprotective structure greenhouse tomato productionwere approximately 30 lower than that in open fields(Esengun et al 2007 Hatirli et al 2006) The greateryield coupled with lower labor machinery and irri-gation energy provide a net energy saving relative toopen fields in spite of greater fertilizer electricity andpesticide inputs for these greenhouses This study alsoexcludes embodied energy of greenhouse infrastruc-ture When taken together these studies suggest thatinputs required for UA will be operation crop andclimate dependent emphasizing the need for consider-ation of these elements when making comparisons andconsidering UA expansion

With respect to soilless production systems Albahoet al (2008) state that aeroponic15 systems require anuninterrupted electrical supply but it is unclear as towhether this energy demand is offset by lower inputsand higher yields relative to conventional controlled-environment or hydroponic systems A summary of theenergy implications of production methods is providedin table 3 along with estimates of energy implicationsfrom efforts to scale up UA in table 4

Drivers of variabilityJudging the pressures production systems haveon resource demands requires reflection on anumber of contextual factors For example localclimategeography may reduce the need for energy-intensive inputs (iemild climate plentiful surfacerainwater) As well existing infrastructure (green and grey)may or may not provide access to necessary inputs(nutrients water energy labor and growing media)This reflection may also include questions such aswhether there is an abundance of low-grade heat thatis accessible for exploitation and is the supplier (iea local utility) amenable to supporting its exploita-tion or perhaps if there is an existing agreement to

15 Aeroponic systems are those that involve the culture of plants inthe absence of soil or hydroponic media (Anonymous 2011)

7


Table 3 Energy implications of different production methods

Production method Energy benefits Energy costs

Open airmdashlarge scale Reliant on natural systems for photosynthesis

growing environment and to some extent water

supply

Centralized and seasonal production

systems that tend to require complex

distribution networks that necessitate

transportation and cold storageOpen airmdashsmall scale (eg balconyallotment residential garden)

Reliant on natural systems for photosynthesis avoids

conventional distribution network

Input practices dependent on skill of

UA practitioner (potential for

excessive use) system design (eg

moisture retention of planter boxes

compared with field)Controlled environmentmdashprotectedagriculture

Higher yields can be located close to consumption

with an extended growing season low material inputs

relative to other

Relatively high embodied energy

inputs of capital per production unit

when compared with open fieldControlledenvironmentmdashconventionalgreenhouses


with an extended growing season

As above but with energy inputs for

lighting irrigation systems or other

control systems in addition to

growing mediumControlled environmentmdashadvancedsoilless systems



As above but with added operating

energy from soilless systems (eg

pumping dosing equipment)

Table 4 Estimated energy impacts within and beyond urban boundaries from scaling up urban agriculture on the broaderfoodndashenergyndashwater system

Within urban boundaries Beyond urban boundaries

Upward Pressure∙ Heating (for some controlled environment agriculture)∙ Waterwastewater treatment (conventional network usage)∙ Labor (paid or unpaid)∙ Transportation (in cases of inefficient local supply chain)

Upward Pressure

∙ Construction materials (eg steel framing LDPE sheeting

polycarbonate glazing)a b c

Downward Pressure∙ Transportation (eg backyard gardens)∙ Waste disposal (assuming less loss along supply chain)∙ Waterwastewater (decentralized usage)∙ Building energy demand (eg evapotranspiration green roofs)

Downward Pressure

∙ Irrigation water (through controlled-environment agriculture)

∙ Inorganic inputs (wastewater reuse)

∙ Machinerycapital (human inputs)

∙ Packaging materials

∙ Cold-chain requirements

a Goldstein et al (2016a)b Martınez-Blanco et al (2011)c Kulak et al (2013)

supply nutrients from wastewater to peri-urban agri-culture or further afield Additionally an abundanceof uncontaminated vacant land or a low populationdensity may make open-field or protected systems themost plausible approach Further considerations withrespect to publically-owned land might be whetherthese local green spaces are compatible with UA inte-gration when safety waste collection accessibility andpublic demand are taken into account Finally Pelletieret al (2011) suggest that scale of production systemsmay also play a role in energy efficiency though scalein itself is not an indicator of energy efficient produc-tion smaller operations have been observed to havelower energy intensities in the examples of tomatoesand swine It is clear that further research is needed toparse out the roles that scale climate existing infras-tructure waste resource availability can have on theoverall energy picture of UA operations Moreoveran assessment of the local context is necessary beforepromoting any particular UA approach along with theaccompanying resource demands these systems requirein a given context

Exploiting urban resources for localagriculture

Numerous opportunities exist to scale up UA in anenergy-efficient manner both within present urbansystems and carefully-planned future developmentsIf however an industrial ecology lens were appliedfor future planning a paradigm shift in food systemsintegration could be achieved with respect to the urbanfoodndashenergyndashwater system includingopportunities forutilizing food waste wastewater and waste heatCO2recovery In industrial ecology efforts are made tomimic natural ecosystems through more efficient use ofresources through the exploitation of waste streams byother production systems (Clift and Druckman 2016)

The urban form can be re-imagined to facilitatethe incorporation of UA in a truly integrated way Theconcept of co-locating agriculture would imply morethan preserving peri-urban agriculture and householdgardens it would focus on identifying spaces withinbuilt-up areas that are amenable to agriculture and thatare also within close proximity to agricultural inputs

8


(waste heat compost wastewater and flue CO2 fromcompatible sources) One example of such an eco-industrial system in a rural setting is described by Zhanget al (2013) where yields can be improved from CO2fertilization through the integration of manure man-agement and greenhouse operations Biogas generatedfrom the manure disposal system is used in place of nat-ural gas to heat the greenhouses and fertilize with CO2while reducing emissions of GHGs and air pollutantsMetson et al (2012) demonstrate that the co-locationof agriculture near urban areas can enable improvedresource efficiency In their Arizona study they foundthat the increasing dairy demand from a growing citywas accompanied by an expansion of dairies and alfalfafarms (for feed) in its hinterlands the alfalfa farms uti-lized cow manure from the dairies as well as biosolidsfrom urban wastewater as a source of phosphorousincreasing the local nutrient cycling in the city-region Ifplanners are able to identify or (ideally) inventory pro-jectedcurrent UA-related resource streams the overallembodied or direct energy demand associated withthese UA systems can be reduced more deliberatelyand presumably more effectively

A summary of key resource streams that are valu-able in agriculture is provided in table 5 along withtheir conventional energy inputs as stated in a varietyof literature sources The extent to which these energydemands will be offset will differ depending on theagriculture operation

With the increasing frequency of extreme weatherevents and uncertainty of future water availabilityagriculture production in the US has the poten-tial to be negatively affected by climate change (USGlobal Change Research Program 2014) Urban agri-culture could increase resilience against these (as ithistorically has done during resource shocks throughthe centuries per Barthel and Isendahl 2013) whilereducing environmental impacts within the currentinfrastructural construct these benefits could be evengreater if an industrial ecology approach is takenIndeed controlled-environment production systemscan potentially protect crops from the climate vari-ability and extremes that would otherwise disturbopen-field production systems These more secureand higher yielding (Martınez-Blanco et al 2011)operations would bring greater certainty in yields aswell as improved resilience relative to the uncer-tainty of the broader food supply chain In additioncontrolled-environment agriculture systems can beplanned for integration into new and existing build-ings and industries to make better use of inputs thatare predominantly from urban waste streams (eg fluegas waste heat wastewater biosolids) The followingsections provide a discussion of strategies to deploycontrolled-environment agriculture within the currentinfrastructural context and within an interconnectedUA ecosystem that is designed for resource recoveryfrom waste streams

Energy production from food wasteFood waste has the potential to be converted to auseful energy resource in the form of biogas withmany cities already collecting source-separated organ-ics for processing in local anaerobic digesters (UckunKiran et al 2014 Sanscartier et al 2012 Moharebet al 2011 Bernstad and la Cour Jansen 2011) Fol-lowing the potential for circular resource use suggestedby Metson et al (2012) the proximity of increasedurban food waste from both production as well asfurther down the food supply chain could provide agreater feedstock for co-located urban anaerobic diges-tion (AD) systems In addition digestate producedfrom these facilities could find local end-uses in UAoperations facilitating a circular material flow Gov-ernments are currently promoting UA to reduce thecarbon footprint of cities (Arup and C40 Cities 2014)Keeping this objective in mind it is important to con-sider how food waste (a major component of GHGemissions from landfills US EPA 2017) can be betterutilized within a more cyclical UA system

Using foodwaste for energy generation throughADprovides an opportunity for distributed energy gener-ation while decreasing the impact of food waste ondownstream systems (landfills wastewater treatmentplants) Levis and Barlaz (2011) assessed the environ-mental performance of food waste disposal in ninecommon waste management systems and found thatAD performed best with respect to GHG emissionsNOx SO2 and net energy demand Further consid-ering the proximity to potential end users the useof biogas from AD facilities for both heat and elec-tricity production could become more economicallyattractive in an urban context especially with local UAconsumers of waste CO2 (from biogas production) andAD digestate It is estimated that the US cities produce130 Mt of food waste annually16 Using estimates of 184kWh of electricity and 810 MJ heat Mgminus1 of wet waste(from Moslashller et al 2009) this quantity of food wastehas the potential to provide electricity for 72 millionNissan Leaf all-electric vehicles17 and the equivalentheatingdemand forover15millionMichiganhomes18 respectively

Cities are currently operating AD facilities that areproviding energy to the broader community Barcelonais treating 192 000 t yrminus1 of its organic fraction ofmunicipal solid waste (OFMSW) through AD having apositive energy balance of around 22 MJ producedMJconsumed at the facility from pre-treatments anddigester pumpingstirring (Romero-Guiza et al 2014)

16 Uses an estimate of 500 kg of food discarded per capita in 2010from retail and consumers (USDA ERS 2013) and a US urbanpopulation of 261 427 500 (US Census Bureau 2015)17 Assuming 11 500 miles per year (Heller and Keoleian 2015) Leafmileage of 29 kWh100 miles (wwwfueleconomygov)18 The average Michigan home consumes 123 million BTU 55for heating (wwweiagovconsumptionresidentialreports2009state_briefspdfmipdf)

9


Table 5 Key agricultural resource streams potential urban sources and energy requirement for resource stream use in conventional urbanagricultural systems

Urban resource stream Potential alternative urbansources

Energy requirementminusconventional sources

Source of energy requirementdata

Treated water ∙ Decentralized wastewater

treatment

∙ Rain barrels

∙ Grey water

133minus140 MJ mminus3 (surface

water)

sim173 MJ mminus3 (groundwater)

Electric Power Research

Institute (2002)

Heat and carbondioxidea

∙ Electricity generation

∙ Residential furnaces boilers

hot water heaters

∙ Industrialcommercial waste

heat

∙ Anaerobic digesters

∙ Heat transferred from

conditions buildings

∙ Sewage networks

sim2500 kWh mminus2-year (mild

climate eg HDD18 = 2800

Abbotsford BCe greenhouse

heated with natural gas)

Calculated from British

Columbia case study (Zhang

et al 2013)

Nitrogen 138 MJ kgminus1 (345

NH4NO3)

145 MJ kgminus1 (NH4SO4)

151 MJ kgminus1 (275

NH4NO3)

3258 MJ kgminus1 (CH4N2O)c

EU averageminus3528 MJ kgminus1

(urea) bestminus184 MJ kgminus1

5746 MJ kgminus1 (US)

Feedstockminus2552minus2765 MJ

kgminus1 (UK) indirect and direct

energymdash84minus196 MJ kgminus1

(UK)

Audsley et al (1997) Danish

and UK data

Smith et al (2001)

West and Marland (2002)

Mortimer et al

(2003)mdashNH4NO3

appendix C

Phosphorus ∙ Digestate from anaerobic

digestion

∙ Human biosolids

∙ Animal manure

∙ Compost (ie using wastes from

gardens green roofs and UA)

∙ Industrial waste streams

382 MJ kgminus1

972minus1872 MJ kgminus1 (EU)


bestminus182 MJ kgminus1 (P2O5)

702 MJ kgminus1 (P2O5) (US)

1580 MJ kgminus1 (P2O5) (EU)

Hansen (2006)b

Audsley et al (1997)

Smith et al (2001)


Elsayed et al (2003)

Potassium 054 MJ kgminus1

500 MJ kgminus1d


bestminus058 MJ kgminus1 (K2O)

684 MJ kgminus1 (K2O) (US)

929 MJ kgminus1 (K2O) (EU)

Hansen (2006)b


Smith et al (2001)



Calcium 173 MJ kgminus1 (CaCO3) (US)

209 MJ kgminus1 (CaO) (EU)



Structural materials ∙ Municipal solid waste for

construction materials (eg

hoop houses)

011 MJ kgminus1 steel (for hoop

house or greenhouse

structures)

Althaus (2003) - EcoInvent 3

Life Cycle Inventories of

Metals 2009

a to be diverted to boost yields of greenhouse operationsb excludes lsquoinherentrsquo (embodied) energy of CH4 305 MJ kgminus1 Nc including mining energy demand as reported in Boslashckman et al 1990d sum of natural gas electricity and coke used in manufacture of chromium steele five-year average (2012ndash16) from wwwdegreedaysnet

Additionally anaerobic co-digestion with sewagesludge could enhance biogas production and deals withthe seasonality that food waste from UA can present(Fonoll et al 2015 Shrestha et al 2017) Policy inter-ventions will likely be necessary to encourage broaderinvestment in AD (Binkley et al 2013) For example inthe north of Italy 26 000ndash28 000 of OFMSW are treatedeach year in AD plant while the facility has obtaineda positive cash flow of e25 million yrminus1 an incentive

for the usegeneration of renewable energy was neededto enable this to occur (Riva et al 2014)

Beyond energy production AD offers additionalbenefits Situating anaerobic digesters near UA oper-ations could facilitate the reuse of digestate (such asin Garfı et al 2011) saving on fertilizer requirementsand reducing transportation costs for waste diversionThe coupling of AD with pyrolysis has the potential toproduce biochar which could be used to improve soil

10


fertility (Monlau et al 2016) Excess heat from AD orpyrolysis can also be applied to the digester to or todistrict heating systems and can be used to heat housesor aquaculture operations

The barriers associated with the reintroduction oflivestock into relatively dense areas are formidablethese include local regulations public health concernsand logistic difficulties of feed provision (Food andAgriculture Organization 2001 Butler 2011) If sur-mounted these operations as well as primary andsecondary food processing industries (eg breweriesethanol production harvest-related waste from agri-cultural operations) can provide substantial feedstocksfor AD

Finally in cases where AD is impractical UAprovides a local end user for composted residuesHence onsite compost facilities could be a compo-nent of future UA operations This would reduceGHG emissions from waste that would have beendisposed of in a landfill and avoids the need fortransportation of waste to a location offsite Accord-ing to the US EPA WARM model19 composting foodwaste and avoiding its addition to landfill results ina net reduction of 096 Mg CO2e per Mg of foodwaste

Wastewater reuse in urban agricultureBoth solid and liquid streams of wastewater are anunderutilized resource with their current perceptionas a municipal liability requiring resource-intensivetreatment and disposal It has been estimated thatapproximately 2 of the total US electricity use isfor municipal wastewater treatment (Electric PowerResearch Institute 2002) The aeration step of treat-ment which promotes biodegradation of pollutantsaccounts for approximately 50 of this energy use(Curtis 2010 Mamais et al 2015) This approach alsoresults in the release of GHG emissions to the atmo-sphere in 2000 US wastewater treatment resulted insim333 Mt CO2e from energy use and sludge degrada-tion (Center for Sustainable Systems 2014) A systemthat diverts wastewater from treatment reduces thelevel of treatment or eliminates the need for aeration(through diversion from receiving water bodies to UA)could help reduce these emissions

Wastewater reuse could be a practical source ofwater and nutrients in UA Previous studies havenoted heavy metal and pathogen contamination ofwastewater-irrigated produce (Amoah et al 2007Khan et al 2008) underscoring the need to ensureregulatory requirements for irrigation water qual-ity are met (World Health Organization 2006) Ifcitiesneighborhoods were to reorient their wastew-ater treatment goals from a focus on disposal toone of reuse the treatment reduction could result

19 Using national average landfill characteristics and default wastehauling distances of 20 miles (www3epagovwarm)

in substantial energy savingsmdashdirectly at the pointof treatment as well as upstream from crop pro-duction For example crops grown using waterand nutrients recovered from wastewater could off-set the embodied energy demand of crops thatare grown elsewhere using more energy-intensiveirrigation water and inorganic fertilizers Anaero-bic membrane bioreactors are one technology thathas been proposed to accomplish these goals (Smithet al 2012 2014) recovering energy generating aneffluent rich in nutrients and low in suspended solidsand organics and eliminating energy requirementsrelated to aerobic treatment (Smith et al 2014) Regard-less of the technology used further research is necessaryto evaluate the removal potential of trace contaminantsand viral pathogens prior to reuse for UA (Smithet al 2012 McCurry et al 2014) By taking an indus-trial ecology approach residential waste streams andindustrial waste streams that are relatively benign andwith a low pathogen load (eg brewery waste) couldbe used in subsurface irrigation of UA crops avoidingconventional treatment and reclaiming nutrients forfood production

Waste heat or CO2 use for urban agricultureFinally a further industrial ecological approach wouldsee conventional infrastructure systems integrated withagriculture to increase productivity Many sourcesof waste heat and CO2 exist within the urbanboundary from residences to industrial operations toelectrical utilities Where natural gas is employed inthese applications greenhouse operations can utilizethe relatively clean exhausted low-grade energy asa heat source as well as CO2 for crop fertilization(Kimball 1983 Mortensen 1987) If greenhouses andhouseholds could be integrated there is a potentialefficiency gain in the combined system over its dis-crete components including through the provision ofCO2 for crop fertilization and utilization of waste heatA number of studies have suggested that building-integrated agriculture has the potential to improveoverall energy performance of the system (Spechtet al 2013) Decentralized residential heating systems insingle-family homes make utilization challenging butspecialized building-integrated systems like the exam-ple developed by Seawater Greenhouses could be amodel for smaller-scale units that utilize waste heatand CO2 on site (Delor 2011) Nevertheless the modelpresented by Ceron-Palma et al (2012) of a rooftopgreenhouse in Barcelona highlights the challenges ofbuilding-integratedUAasgreenhouseheating require-ments were not temporally aligned with the times ofexcessheatwithin thebuilding instead this typeof pro-duction system may be better suited to colder climateswhere exhaust CO2 and heat from boilersfurnaces aremore available during winter months This highlightsthe need for additional research on how to overcomethese types of management issues to support greaterresource efficiency

11


Planningandhumancapital considerations forurbanagricultureHistorically UA was a natural part of urban develop-ment and eventually an essential component of theplans of early urban planning practitioners (Vitielloand Brinkley 2013) However UA was not a primaryobjective for planning developed-world public spacesin industrialized food system of 20th century citiesCalls to reconsider the value of UA have been madefor decades (eg in the pattern language proposedby Alexander et al 1977) and planning for UA as aresult has returned The success of UA re-adoptionin urban design is demonstrated by the Carrot CityInitiative (Gorgolewski et al 2017) which facilitates dis-cussions on urban design for food production Theseand other resources can help to increase the sophis-tication of food planning in a more cyclical urbanecosystem

Planners can open up or create space to enablethe upscaling of UA in either building-integrated sys-tems or newexisting green space For example parkscould be redeveloped from being merely aesthetically-pleasing recreational landscapes to be more functionalwith edible productivity through the incorporation offruit trees and community gardens Inventories of suit-able public and private vacant land could be identifiedfor UA use through geomatic methods (McClintocket al 2013) Municipal support for training in theharvest and processing of crops could increase thepublicrsquos awareness of the resources embodied withinthe food they consume and minimize and potentiallyminimize crop waste Processing infrastructure suchas fruit presses or preserving facilities could be situ-ated within the parkrsquos borders By-laws could be put inplace to incentivize rooftop UA as has been done withgreen roofs in some cities (eg Toronto and ChicagoLoder 2014)

As mentioned previously UA expansion couldlead to local increases in polluted run-off This mayrequire the implementation of by-laws restrictingfertilizer or pesticide application storm water reme-diationmitigation measures and out-reach to informcitizens of health and environmental implications ofagriculture As well inventories of UA and surveysof practices coupled with geographic information sys-tems could help planners identify potential hotspots forrunoff odors or other impacts

Human labor is an abundant urban resource that isanticipated to become more available in cities as trendsof urbanization and automation progress Smaller-scale agricultural systems have the potential to utilizethis labor as they tend to be more labor intensivethan conventional mechanized open-field agricultureAs well the integration of UA in buildings and theapplication of advanced production approaches (iesoilless operations) require specialized training duringdesign construction and operation creating high-skilled employment opportunities The impacts onfood prices by shifting to small-scale UA systems is

unclear the 2012 US agricultural census suggests thathired and contract farm labor contributed to only102 of total farm production expenses though itis suggested that this would vary substantially by cropraised and potentially less mechanizedautomated sys-tems (US Department of Agriculture 2014 USDA ERS2014) The recreational utility realized by those pur-suing UA as a leisure activity could reduce the netincrease in costs (ie people providing free labor in pur-suit of UA as a hobby) further multiple non-monetarybenefits (civic engagement social cohesion food secu-rity) have been recognized enabling a scenario wherebroad public benefits of UA can be realized coupledwith an understanding of its effects on health and theenvironment (Chen 2012 Horst et al 2017)

Avoiding unintended consequences in scaling upurban agricultureA number of issues may inhibit efforts to scale upUA including land scarcity (Martellozzo et al 2014)UArsquos uncertain contribution to food security (Ward2015) environmental impacts of decentralized pro-duction (Nicholson et al 2015 Coley et al 2009) andmanagement of new sources of food waste (Levis andBarlaz 2011 Forkes 2007 Smil 2004) Avoiding unin-tended consequences and continued inefficiency in thefood system through urban production requires a plan-ning approach that coordinates input streams reducespotential for waste and enables co-location to mitigategrowth in transportation demand Foley et al (2011)suggest that efforts to meet the food needs of the risingglobal (urban) population face substantial challenges toenvironmental protection Further resource demandsof all urban food consumption far exceeds the resourcesthat can be provided within city boundaries and mov-ing towards this goal could create new local resourcestresses for example Ramaswami et al (2017) demon-strate this situation for New Delhirsquos water demandwhere water used for food production represented 72of urban-related withdrawals (in turn only 14 ofthese water withdrawals was provided within the cityrsquosboundary)

We argue that an industrial ecological approachto UA has the potential to slow land use change(through the intensification of production) increasecrops yields (by increasing management intensity)increase resource efficiency (through co-location ofinputs from waste streams) and encourage low-carbondiets (through increasedaccess to freshproduceWake-field et al 2007 Schafft et al 2009) However proximityalone are not a guarantee for success of eco-industrialUAGibbs andDeutz (2007) reviewanumberof unsuc-cessful industrial ecological case studies and interviewparticipants in these and find that results often do notmatch objectives However with an incremental plan-ning approach improved networking to develop trustand cooperation and targeted policy interventions bymunicipalities could improve the success of industrialecological approaches

12


Implications of UA on production inputs foodwaste and transportation (of both labor and food prod-ucts) are dependent on UA approaches taken As anillustration this will be influenced by the productionpractices of UA practitioners efficiency of distributionsystems public and active transportation options foraccessing UA sites producer and retail practices forfood disposal and local attitudes towards food wasteAll of these require further study within each localcontext

Conclusions

This review has examined UA through a novel lensconsidering the energy implications of promoting theexpansion of food production in various forms withincities in advanced economies Scaling up UA has impli-cations for thebroader energy systemwith thepotentialto affect direct and upstream energy demand andenable the utilization of resources to a greater degreeThis review underscores the need to pursue furthercase study research to understand the implicationsof human and physical geographies on net energydemands and other environmental impacts of UA inits many iterations Different combinations of croptype climate production methodscale availability oflsquowastersquo resources co-locationapproaches and intensityofproductionallneed tobeexplored toobtainabroaderunderstanding of the life cycle energy implications ofscaling up urban agriculture

We have proposed and provide supporting infor-mation for a resource-efficient path to pursuing theexpansion of UAmdashthrough the exploitation of cropand other food wastes reuse of municipal wastewaterand biosolids for crop fertilization and irrigation andemploying the plentiful sources of waste heat and CO2Integrating agriculture with urban planning is not anew concept but deep consideration of energy use inthe broader food system and the availability of rele-vant resources within cities (often as underexploitedwaste streams) can help realize substantial efficiencyimprovements in future urbanized food system

Acknowledgments

This research was initiated through work completedduring the National Science Foundation (NSF grantnumber 1541838) funded workshop held October5minus6 at the University of Michigan entitled lsquolsquoScalingrsquoUp Urban Agriculture to Mitigate Food-Energy-Water-Impactsrsquo XF and LR acknowledge supportfrom the NSF Sustainability Research Networks grant1444745 and REFRESCH (Global Challenges forthe Third Century program Office of the ProvostUniversity of Michigan) The authors thank GlenDaigger Tim Dixon Nancy Love Josh Newell andMartin Sexton for comments on various iterations ofthis manuscript

ORCID iDs

Eugene Mohareb httpsorcidorg0000-0003-0344-2253Martin Heller httpsorcidorg0000-0001-9204-6222PaigeNovak httpsorcidorg0000-0001-9054-0278Benjamin Goldstein httpsorcidorg0000-0003-0055-1323Xavier Fonoll httpsorcidorg0000-0003-3304-2437Lutgarde Raskin httpsorcidorg0000-0002-9625-4034

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Grewal S S and Grewal P S 2012 Can cities become self-reliant infood Cities 29 1ndash11

Hamilton A J Burry K Mok H-F Barker S F Grove J R andWilliamson V G 2013 Give peas a chance Urban agriculturein developing countries A review Agron Sustain Dev 3445ndash73

Hamm M W 2015 Feeding citiesmdashwith indoor vertical farms FoodClim Res Netw (httpfcrnorgukfcrn-blogsmichaelwhammfeeding-cities-indoor-vertical-farms)(Accessed 6 September 2017)

Hansen T L 2006 Life cycle modelling of environmental impacts ofapplication of processed organic municipal solid waste onagricultural land (Easewaste) Waste Manage Res 24153ndash66

Hanssen O J Vold M Schakenda V Tufte P A Moslashller H Olsen NV and Skaret J 2017 Environmental profile packagingintensity and food waste generation for three types of dinnermeals J Clean Prod 142 395ndash402

14


Hatirli S A Ozkan B and Fert C 2006 Energy inputs and crop yieldrelationship in greenhouse tomato production Renew Energy31 427ndash38

Heidari M D and Omid M 2011 Energy use patterns andeconometric models of major greenhouse vegetableproductions in Iran Energy 36 220ndash5

Heller M C and Keoleian G A 2015 Greenhouse gas emissionestimates of US dietary choices and food loss J Ind Ecol 19291ndash401

Horst M McClintock N and Hoey L 2017 The intersection ofplanning urban agriculture and food justice a review of theliterature J Am Plan Assoc 83 277ndash95

Hospido A Mila I Canals L McLaren S Truninger MEdwards-Jones G and Clift R 2009 The role of seasonality inlettuce consumption a case study of environmental and socialaspects Int J Life Cycle Assess 14 381ndash91

Howe J and Wheeler P 1999 Urban food growing the experience oftwo UK cities Sustain Dev 7 13ndash24

IPCC 2006 2006 IPCC Guidelines for National Greenhouse GasInventories (wwwipcc-nggipigesorjppublic2006gl)

Jaffal I Ouldboukhitine S-E and Belarbi R 2012 A comprehensivestudy of the impact of green roofs on building energyperformance Renew Energy 43 157ndash64

Jansson Aring 2013 Reaching for a sustainable resilient urban futureusing the lens of ecosystem services Ecol Econ 86 285ndash91

Khan S Cao Q Zheng Y M Huang Y Z and Zhu Y G 2008 Healthrisks of heavy metals in contaminated soils and food cropsirrigated with wastewater in Beijing China Environ Pollut152 686ndash92

Kimball B A 1983 Carbon dioxide and agricultural yield anassemblage and analysis of 430 prior observations Agron J 75779ndash88

Klein G Krebs M Hall V OrsquoBrien T and Blevins B B 2005Californiarsquos waterndashenergy relationship California EnergyCommission Report CEC-700-2005-011-SF (wwwenergycagov2005publicationsCEC-700-2005-011CEC-700-2005-011-SFPDF)

Krannich J M 2006 A modern disaster agricultural land urbangrowth and the need for a federally organized comprehensiveland use planning model Cornell J Law Public Policy 16 56ndash99

Kulak M Graves A and Chatterton J 2013 Reducing greenhouse gasemissions with urban agriculture a life cycle assessmentperspective Landsc Urban Plan 111 68ndash78

Kuswardhani N Soni P and Shivakoti G P 2013 Comparativeenergy input-output and financial analyses of greenhouse andopen field vegetables production in West Java IndonesiaEnergy 53 83ndash92

Leach G 1975 Energy and food production Food Policy 1 62ndash73Levis J W and Barlaz M a 2011 What is the most environmentally

beneficial way to treat commercial food waste Environ SciTechnol 45 7438ndash44

Loder A 2014 Therersquos a meadow outside my workplace aphenomenological exploration of aesthetics and green roofs inChicago and Toronto Landsc Urban Plan 126 94ndash106

Mamais D Noutsopoulos C Dimopoulou A Stasinakis A andLekkas T D 2015 Wastewater treatment process impact onenergy savings and greenhouse gas emissions Water SciTechnol 71 303ndash8

Martellozzo F Landry J-S Plouffe D Seufert V Rowhani P andRamankutty N 2014 Urban agriculture a global analysis of thespace constraint to meet urban vegetable demand EnvironRes Lett 9 064025

Martınez-Blanco J Munoz P Anton A and Rieradevall J 2011Assessment of tomato Mediterranean production inopen-field and standard multi-tunnel greenhouse withcompost or mineral fertilizers from an agricultural andenvironmental standpoint J Clean Prod 19 985ndash97

McClintock N Cooper J and Khandeshi S 2013 Assessing thepotential contribution of vacant land to urban vegetableproduction and consumption in Oakland California LandscUrban Plan 111 46ndash58

McCurry D Bear S Bae J Sedlak D McCarty P and Mitch W 2014Superior removal of disinfection byproduct precursors and

pharmaceuticals from wastewater in a staged anaerobicfluidized membrane bioreactor compared to activated sludgeEnviron Sci Technol Lett 1 459ndash64

Metson G Aggarwal R and Childers D L 2012 Efficiency throughproximity changes in phosphorus cycling at theurban-agricultural interface of a rapidly urbanizing desertregion J Ind Ecol 16 914ndash27

Milan C 2015 Milan Urban Food Policy Pact (wwwfoodpolicymilanoorgenurban-food-policy-pact-2)

Mohareb E A MacLean H L and Kennedy C A 2011 Greenhousegas emissions from waste managementmdashassessment ofquantification methods J Air Waste Manage Assoc 61480ndash93

Mok H-F F Williamson V G Grove J R Burry K Barker S F andHamilton A J 2013 Strawberry fields forever Urbanagriculture in developed countries a review Agron SustainDev 34 21ndash43

Moslashller J Boldrin A and Christensen T H 2009 Anaerobic digestionand digestate use accounting of greenhouse gases and globalwarming contribution Waste Manage Res 27 813ndash24

Monlau F Francavilla M Sambusiti C Antoniou N Solhy ALibutti A Zabaniotou A Barakat A and Monteleone M 2016Toward a functional integration of anaerobic digestion andpyrolysis for a sustainable resource management Comparisonbetween solid-digestate and its derived pyrochar as soilamendment Appl Energy 169 652ndash62

Mortensen L M 1987 Review CO2 enrichment in greenhousesCrop responses Sci Hortic 33 1ndash25

Mortimer N D Cormack P Elsayed M A and Horne R E 2003Evaluation of the comparative energy global warming andsocio-economic costs and benefits of biodiesel (httpsciencesearchdefragovukDefaultaspxMenu=MenuampModule=MoreampLocation=NoneampCompleted=0ampProjectID=10701)

Nicholson C F He X Gomez M I Gao H O and Hill E 2015Environmental and economic impacts of localizing foodsystems the case of dairy supply chains in the NortheasternUnited States Environ Sci Technol 49 12005ndash14

Oke T R 1973 City size and the urban heat island Atmos Environ 7769ndash79

Orsini F Gasperi D Marchetti L Piovene C Draghetti SRamazzotti S Bazzocchi G and Gianquinto G 2014 Exploringthe production capacity of rooftop gardens (RTGs) in urbanagriculture the potential impact on food and nutritionsecurity biodiversity and other ecosystem services in the cityof Bologna Food Secur 6 781ndash92

Orsini F Kahane R Nono-Womdim R and Gianquinto G 2013Urban agriculture in the developing world a review AgronSustain Dev 33 695ndash720

Pagano M A and Bowman A O 2000 Vacant land in cities an urbanresource Brookings Institute Report (wwwbrookingseduwp-contentuploads201606paganofinalpdf)

Pataki D E et al 2011 Coupling biogeochemical cycles in urbanenvironments ecosystem services green solutions andmisconceptions Front Ecol Environ 9 27ndash36

Payen S Basset-Mens C and Perret S 2015 LCA of local andimported tomato an energy and water trade-off J Clean Prod87 139ndash48

Pelletier N Audsley E Brodt S Garnett T Henriksson P Kendall AKramer K J Murphy D Nemecek T and Troell M 2011Energy intensity of agriculture and food systems Annu RevEnviron Resour 36 223ndash46

Pimentel D Williamson S Alexander C E Gonzalez-Pagan OKontak C and Mulkey S E 2008 Reducing energy inputs in theUS food system Hum Ecol 36 459ndash71

Pirog R Van Pelt T Enshayan K and Cook E 2001 Food fuel andfreeways an Iowa perspective on how far food travels fuelusage and greenhouse gas emissions Report(httplibdriastateeducgiviewcontentcgiarticle=1002ampcontext=leopold_pubspapers)

Plawecki R Pirog R Montri A and Hamm M W 2014 Comparativecarbon footprint assessment of winter lettuce production intwo climatic zones for Midwestern market Renew Agric FoodSyst 29 310ndash8

15


Racoviceanu A I Karney B W Kennedy C A and Colombo A F2007 Life-cycle energy use and greenhouse gas emissionsinventory for water treatment systems J Infrastruct Syst 13261ndash70

Ramaswami A Boyer D Nagpure A S Fang A Bogra S Bakshi BCohen E and Rao-Ghorpade A 2017 An urban systemsframework to assess the trans-boundary foodndashenergyndashwaternexus implementation in Delhi India Environ Res Lett 12025008

Riva C Schievano A DrsquoImporzano G and Adani F 2014Production costs and operative margins in electric energygeneration from biogas Full-scale case studies in Italy WasteManage 34 1429ndash35

Romero-Guiza M S Peces M Astals S Benavent J Valls J andMata-Alvarez J 2014 Implementation of a prototypaloptical sorter as core of the new pre-treatmentconfiguration of a mechanical-biological treatment planttreating OFMSW through anaerobic digestion Appl Energy135 63ndash70

Saiz S Kennedy C Bass B and Pressnail K 2006 Comparative lifecycle assessment of standard and green roofs Environ SciTechnol 40 4312ndash6

Sanscartier D Maclean H L and Saville B 2012 Electricityproduction from anaerobic digestion of householdorganic waste in Ontario techno-economic and GHGemission analyses Environ Sci Technol 461233ndash42

Sanye-Mengual E Oliver-Sola J Montero J I and Rieradevall J 2015An environmental and economic life cycle assessment ofrooftop greenhouse (RTG) implementation in BarcelonaSpain Assessing new forms of urban agriculture from thegreenhouse structure to the final product level Int J Life CycleAssess 20 350ndash66

Schafft K A Jensen E B and Clare Hinrichs C 2009 Food desertsand overweight schoolchildren evidence from PennsylvaniaRural Sociol 74 153ndash77

Shiina T Hosokawa D Roy P Orikasa T Nakamura N andThammawong M 2011 Life cycle inventory analysis of leafyvegetables grown in two types of plant factories Acta Hortic919 115ndash22

Shrestha S Fonoll X Khanal S K and Raskin L 2017 Biologicalstrategies for enhanced hydrolysis of lignocellulosic biomassduring anaerobic digestion current status and futureperspectives Bioresour Technol 245 1245ndash57

Smil V 2004 Improving efficiency and reducing waste in our foodsystem Environ Sci 1 17ndash26

Smit J and Nasr J 1992 Urban agriculture for sustainable citiesusing wastes and idle land and water bodies as resourcesEnviron Urban 4 141ndash52

Smith A Brown K Ogilvie S Rushton K and Bates J 2001 Wastemanagement options and climate change final report to theEuropean Commission

Smith A Stadler L Cao L Love N Raskin L and Skerlos S 2014Navigating wastewater energy recovery strategies a life cyclecomparison of anaerobic membrane bioreactor andconventional treatment systems with anaerobic digestionEnviron Sci Technol 48 5972ndash81

Smith A Stadler L Love N Skerlos S and Raskin L 2012Perspectives on anaerobic membrane bioreactor treatment ofdomestic wastewater a critical review Bioresour Technol 122149ndash59

Specht K Siebert R Hartmann I Freisinger U B Sawicka MWerner A Thomaier S Henckel D Walk H and Dierich A2014 Urban agriculture of the future an overview ofsustainability aspects of food production in and on buildingsAgric Human Values 31 33ndash51

Tamburini E Pedrini P Marchetti M Fano E and Castaldelli G2015 Life cycle based evaluation of environmental andeconomic impacts of agricultural productions in themediterranean area Sustainability 7 2915ndash35

Taylor J R and Lovell S T 2012 Mapping public and private spacesof urban agriculture in Chicago through the analysis ofhigh-resolution aerial images in Google Earth Landsc UrbanPlan 108 57ndash70

Thebo A L Drechsel P and Lambin E F 2014 Global assessment ofurban and peri-urban agriculture irrigated and rainfedcroplands Environ Res Lett 9 114002

US Global Change Research Program 2014 Climate ChangeImpacts in the United States The Third National ClimateAssessment (nca2014globalchangegov5CnThis)

Uckun Kiran E Trzcinski A P Ng W J and Liu Y 2014Bioconversion of food waste to energy a review Fuel 134389ndash99

US Census Bureau 2015 2010 Census Urban and RuralClassification and Urban Area Criteria (wwwcensusgovgeoreferenceuaurban-rural-2010html)

US Department of Agriculture 2014 US census of agricultureNational Level Data vol 1 (wwwagcensususdagovPublications2012Full_ReportVolume_1_Chapter_1_US)

US Environmental Protection Agency 2008 Ensuring a sustainablefuture an energy management guidebook for wastewater andwater utilities Report (httpsnepisepagovExeZyPURLcgiDockey=P1003Y1GTXT)

US Environmental Protection Agency 2010 Evaluating theenvironmental impacts of packaging fresh tomatoes usinglife-cycle thinking and assessment a sustainable materialsmanagement demonstration project Report (wwwepagovwastesconservetoolsstewardshipdocstomato-packaging-assessmentpdf)

US EPA 2015 eGRID tablesmdash2012 (wwwepagovenergyegrid)US EPA 2017 Inventory of US greenhouse gas emissions and sinks

1990ndash2015 Report (Washington DC) (wwwepagovsitesproductionfiles2017-02documents2017_complete_reportpdf)

USDA ERS 2010 Energy use in the US food system Report(wwwersusdagovmedia136418err94_1_pdf)

USDA ERS 2014 Farm labor (wwwersusdagovtopicsfarm-economyfarm-labor)

USDA ERS 2013 Food Availability Data Syst (wwwersusdagovdata-productsfood-availability-(per-capita)-data-systemaspx)

Vitiello D and Brinkley C 2013 The hidden history of food systemplanning J Plan Hist 13 91ndash112

Wakefield S Yeudall F Taron C Reynolds J and Skinner A 2007Growing urban health community gardening in South-EastToronto Health Promot Int 22 92ndash101

Ward J D 2015 Can urban agriculture usefully improve foodresilience Insights from a linear programming approach JEnviron Stud Sci 5 699ndash711

Webb J Williams A G Hope E Evans D and Moorhouse E 2013Do foods imported into the UK have a greater environmentalimpact than the same foods produced within the UK Int JLife Cycle Assess 18 1325ndash43

Weber C L and Matthews H S 2008 Food-miles and the relativeclimate impacts of food choices in the United States EnvironSci Technol 42 3508ndash13

West T O and Marland G 2002 A synthesis of carbon sequestrationcarbon emissions and net carbon flux in agriculturecomparing tillage practices in the United States Agric EcosystEnviron 91 217ndash32

Williams H and Wikstrom F 2011 Environmental impact ofpackaging and food losses in a life cycle perspective acomparative analysis of five food items J Clean Prod 19 43ndash8

World Health Organization 2006 Guidelines for the safe use ofwastewater excreta and greywater Report vol 1 (GenevaWHO) (httpwhqlibdocwhointpublications20069241546832_engpdf)

Zhang S Bi X T and Clift R 2013 A life cycle assessment ofintegrated dairy farm-greenhouse systems in British ColumbiaBioresour Technol 150 496ndash505

16

CentAUR

Central Archive at the University of Reading

Readingrsquos research outputs online







LETTER




OPEN ACCESS

RECEIVED

15 September 2016

REVISED

21 August 2017


25 August 2017

PUBLISHED

5 December 2017







Introduction















2



Type of urban



upscalingSources

Residentialgardens






∙ Non-mechanized

inputs

∙Reduced cold

chainretail

requirement (onsite

end-consumption)






(Kulak et al 2013

Altieri et al 1999)







∙ Non-mechanized

inputs

∙ Reduced cold

chainretail

requirement


green space



connection



(Leach 1975)









from rooftop

∙ Improved yield


insulation

∙ Onsite waste

diversion





Specht et al 2013

Grard et al 2015

Orsini et al 2014)









towards commercial

availability


∙ Improved yield


streams



resources

(Zhang et al 2013)









∙ Onsite waste

diversion (eg

waste-to-feed for



nutrient cycling

∙ Improved yield








requirements

(Despommier 2013

Hamm 2015)



supplemental heat







∙ Preservation of

high-yielding prime

agricultural land



incompatible urban

development

(Francis et al 2012

Krannich 2006)





3


Agriculture13

Processing17

Packaging5


15

Food Services18

Households29

Total = 14760 PJ











4










5









6











7






supply














relative to other


















Upward Pressure




Downward Pressure











8









9







treatment

∙ Rain barrels

∙ Grey water


water)



Institute (2002)




hot water heaters


heat




∙ Sewage networks







et al 2013)


NH4NO3)



NH4NO3)








(UK)


and UK data

Smith et al (2001)


Mortimer et al

(2003)mdashNH4NO3

appendix C


digestion

∙ Human biosolids

∙ Animal manure




382 MJ kgminus1






Hansen (2006)b


Smith et al (2001)




500 MJ kgminus1d





Hansen (2006)b


Smith et al (2001)









hoop houses)


house or greenhouse

structures)



Metals 2009





10










11









12



Conclusions



Acknowledgments


ORCID iDs


References
















13















































14













































15









































16







LETTER




OPEN ACCESS

RECEIVED

15 September 2016

REVISED

21 August 2017


25 August 2017

PUBLISHED

5 December 2017







Introduction















2



Type of urban



upscalingSources

Residentialgardens






∙ Non-mechanized

inputs

∙Reduced cold

chainretail

requirement (onsite

end-consumption)






(Kulak et al 2013

Altieri et al 1999)







∙ Non-mechanized

inputs

∙ Reduced cold

chainretail

requirement


green space



connection



(Leach 1975)









from rooftop

∙ Improved yield


insulation

∙ Onsite waste

diversion





Specht et al 2013

Grard et al 2015

Orsini et al 2014)









towards commercial

availability


∙ Improved yield


streams



resources

(Zhang et al 2013)









∙ Onsite waste

diversion (eg

waste-to-feed for



nutrient cycling

∙ Improved yield








requirements

(Despommier 2013

Hamm 2015)



supplemental heat







∙ Preservation of

high-yielding prime

agricultural land



incompatible urban

development

(Francis et al 2012

Krannich 2006)





3


Agriculture13

Processing17

Packaging5


15

Food Services18

Households29

Total = 14760 PJ











4










5









6











7






supply














relative to other


















Upward Pressure




Downward Pressure











8









9







treatment

∙ Rain barrels

∙ Grey water


water)



Institute (2002)




hot water heaters


heat




∙ Sewage networks







et al 2013)


NH4NO3)



NH4NO3)








(UK)


and UK data

Smith et al (2001)


Mortimer et al

(2003)mdashNH4NO3

appendix C


digestion

∙ Human biosolids

∙ Animal manure




382 MJ kgminus1






Hansen (2006)b


Smith et al (2001)




500 MJ kgminus1d





Hansen (2006)b


Smith et al (2001)









hoop houses)


house or greenhouse

structures)



Metals 2009





10










11









12



Conclusions



Acknowledgments


ORCID iDs


References
















13















































14













































15









































16


LETTER




OPEN ACCESS

RECEIVED

15 September 2016

REVISED

21 August 2017


25 August 2017

PUBLISHED

5 December 2017







Introduction















2



Type of urban



upscalingSources

Residentialgardens






∙ Non-mechanized

inputs

∙Reduced cold

chainretail

requirement (onsite

end-consumption)






(Kulak et al 2013

Altieri et al 1999)







∙ Non-mechanized

inputs

∙ Reduced cold

chainretail

requirement


green space



connection



(Leach 1975)









from rooftop

∙ Improved yield


insulation

∙ Onsite waste

diversion





Specht et al 2013

Grard et al 2015

Orsini et al 2014)









towards commercial

availability


∙ Improved yield


streams



resources

(Zhang et al 2013)









∙ Onsite waste

diversion (eg

waste-to-feed for



nutrient cycling

∙ Improved yield








requirements

(Despommier 2013

Hamm 2015)



supplemental heat







∙ Preservation of

high-yielding prime

agricultural land



incompatible urban

development

(Francis et al 2012

Krannich 2006)





3


Agriculture13

Processing17

Packaging5


15

Food Services18

Households29

Total = 14760 PJ











4










5









6











7






supply














relative to other


















Upward Pressure




Downward Pressure











8









9







treatment

∙ Rain barrels

∙ Grey water


water)



Institute (2002)




hot water heaters


heat




∙ Sewage networks







et al 2013)


NH4NO3)



NH4NO3)








(UK)


and UK data

Smith et al (2001)


Mortimer et al

(2003)mdashNH4NO3

appendix C


digestion

∙ Human biosolids

∙ Animal manure




382 MJ kgminus1






Hansen (2006)b


Smith et al (2001)




500 MJ kgminus1d





Hansen (2006)b


Smith et al (2001)









hoop houses)


house or greenhouse

structures)



Metals 2009





10










11









12



Conclusions



Acknowledgments


ORCID iDs


References
















13















































14













































15









































16












2



Type of urban



upscalingSources

Residentialgardens






∙ Non-mechanized

inputs

∙Reduced cold

chainretail

requirement (onsite

end-consumption)






(Kulak et al 2013

Altieri et al 1999)







∙ Non-mechanized

inputs

∙ Reduced cold

chainretail

requirement


green space



connection



(Leach 1975)









from rooftop

∙ Improved yield


insulation

∙ Onsite waste

diversion





Specht et al 2013

Grard et al 2015

Orsini et al 2014)









towards commercial

availability


∙ Improved yield


streams



resources

(Zhang et al 2013)









∙ Onsite waste

diversion (eg

waste-to-feed for



nutrient cycling

∙ Improved yield








requirements

(Despommier 2013

Hamm 2015)



supplemental heat







∙ Preservation of

high-yielding prime

agricultural land



incompatible urban

development

(Francis et al 2012

Krannich 2006)





3


Agriculture13

Processing17

Packaging5


15

Food Services18

Households29

Total = 14760 PJ











4










5









6











7






supply














relative to other


















Upward Pressure




Downward Pressure











8









9







treatment

∙ Rain barrels

∙ Grey water


water)



Institute (2002)




hot water heaters


heat




∙ Sewage networks







et al 2013)


NH4NO3)



NH4NO3)








(UK)


and UK data

Smith et al (2001)


Mortimer et al

(2003)mdashNH4NO3

appendix C


digestion

∙ Human biosolids

∙ Animal manure




382 MJ kgminus1






Hansen (2006)b


Smith et al (2001)




500 MJ kgminus1d





Hansen (2006)b


Smith et al (2001)









hoop houses)


house or greenhouse

structures)



Metals 2009





10










11









12



Conclusions



Acknowledgments


ORCID iDs


References
















13















































14













































15









































16



Type of urban



upscalingSources

Residentialgardens






∙ Non-mechanized

inputs

∙Reduced cold

chainretail

requirement (onsite

end-consumption)






(Kulak et al 2013

Altieri et al 1999)







∙ Non-mechanized

inputs

∙ Reduced cold

chainretail

requirement


green space



connection



(Leach 1975)









from rooftop

∙ Improved yield


insulation

∙ Onsite waste

diversion





Specht et al 2013

Grard et al 2015

Orsini et al 2014)









towards commercial

availability


∙ Improved yield


streams



resources

(Zhang et al 2013)









∙ Onsite waste

diversion (eg

waste-to-feed for



nutrient cycling

∙ Improved yield








requirements

(Despommier 2013

Hamm 2015)



supplemental heat







∙ Preservation of

high-yielding prime

agricultural land



incompatible urban

development

(Francis et al 2012

Krannich 2006)





3


Agriculture13

Processing17

Packaging5


15

Food Services18

Households29

Total = 14760 PJ











4










5









6











7






supply














relative to other


















Upward Pressure




Downward Pressure











8









9







treatment

∙ Rain barrels

∙ Grey water


water)



Institute (2002)




hot water heaters


heat




∙ Sewage networks







et al 2013)


NH4NO3)



NH4NO3)








(UK)


and UK data

Smith et al (2001)


Mortimer et al

(2003)mdashNH4NO3

appendix C


digestion

∙ Human biosolids

∙ Animal manure




382 MJ kgminus1






Hansen (2006)b


Smith et al (2001)




500 MJ kgminus1d





Hansen (2006)b


Smith et al (2001)









hoop houses)


house or greenhouse

structures)



Metals 2009





10










11









12



Conclusions



Acknowledgments


ORCID iDs


References
















13















































14













































15









































16


Agriculture13

Processing17

Packaging5


15

Food Services18

Households29

Total = 14760 PJ











4










5









6











7






supply














relative to other


















Upward Pressure




Downward Pressure











8









9







treatment

∙ Rain barrels

∙ Grey water


water)



Institute (2002)




hot water heaters


heat




∙ Sewage networks







et al 2013)


NH4NO3)



NH4NO3)








(UK)


and UK data

Smith et al (2001)


Mortimer et al

(2003)mdashNH4NO3

appendix C


digestion

∙ Human biosolids

∙ Animal manure




382 MJ kgminus1






Hansen (2006)b


Smith et al (2001)




500 MJ kgminus1d





Hansen (2006)b


Smith et al (2001)









hoop houses)


house or greenhouse

structures)



Metals 2009





10










11









12



Conclusions



Acknowledgments


ORCID iDs


References
















13















































14













































15









































16










5









6











7






supply














relative to other


















Upward Pressure




Downward Pressure











8









9







treatment

∙ Rain barrels

∙ Grey water


water)



Institute (2002)




hot water heaters


heat




∙ Sewage networks







et al 2013)


NH4NO3)



NH4NO3)








(UK)


and UK data

Smith et al (2001)


Mortimer et al

(2003)mdashNH4NO3

appendix C


digestion

∙ Human biosolids

∙ Animal manure




382 MJ kgminus1






Hansen (2006)b


Smith et al (2001)




500 MJ kgminus1d





Hansen (2006)b


Smith et al (2001)









hoop houses)


house or greenhouse

structures)



Metals 2009





10










11









12



Conclusions



Acknowledgments


ORCID iDs


References
















13















































14













































15









































16









6











7






supply














relative to other


















Upward Pressure




Downward Pressure











8









9







treatment

∙ Rain barrels

∙ Grey water


water)



Institute (2002)




hot water heaters


heat




∙ Sewage networks







et al 2013)


NH4NO3)



NH4NO3)








(UK)


and UK data

Smith et al (2001)


Mortimer et al

(2003)mdashNH4NO3

appendix C


digestion

∙ Human biosolids

∙ Animal manure




382 MJ kgminus1






Hansen (2006)b


Smith et al (2001)




500 MJ kgminus1d





Hansen (2006)b


Smith et al (2001)









hoop houses)


house or greenhouse

structures)



Metals 2009





10










11









12



Conclusions



Acknowledgments


ORCID iDs


References
















13















































14













































15









































16











7






supply














relative to other


















Upward Pressure




Downward Pressure











8









9







treatment

∙ Rain barrels

∙ Grey water


water)



Institute (2002)




hot water heaters


heat




∙ Sewage networks







et al 2013)


NH4NO3)



NH4NO3)








(UK)


and UK data

Smith et al (2001)


Mortimer et al

(2003)mdashNH4NO3

appendix C


digestion

∙ Human biosolids

∙ Animal manure




382 MJ kgminus1






Hansen (2006)b


Smith et al (2001)




500 MJ kgminus1d





Hansen (2006)b


Smith et al (2001)









hoop houses)


house or greenhouse

structures)



Metals 2009





10










11









12



Conclusions



Acknowledgments


ORCID iDs


References
















13















































14













































15









































16






supply














relative to other


















Upward Pressure




Downward Pressure











8









9







treatment

∙ Rain barrels

∙ Grey water


water)



Institute (2002)




hot water heaters


heat




∙ Sewage networks







et al 2013)


NH4NO3)



NH4NO3)








(UK)


and UK data

Smith et al (2001)


Mortimer et al

(2003)mdashNH4NO3

appendix C


digestion

∙ Human biosolids

∙ Animal manure




382 MJ kgminus1






Hansen (2006)b


Smith et al (2001)




500 MJ kgminus1d





Hansen (2006)b


Smith et al (2001)









hoop houses)


house or greenhouse

structures)



Metals 2009





10










11









12



Conclusions



Acknowledgments


ORCID iDs


References
















13















































14













































15









































16









9







treatment

∙ Rain barrels

∙ Grey water


water)



Institute (2002)




hot water heaters


heat




∙ Sewage networks







et al 2013)


NH4NO3)



NH4NO3)








(UK)


and UK data

Smith et al (2001)


Mortimer et al

(2003)mdashNH4NO3

appendix C


digestion

∙ Human biosolids

∙ Animal manure




382 MJ kgminus1






Hansen (2006)b


Smith et al (2001)




500 MJ kgminus1d





Hansen (2006)b


Smith et al (2001)









hoop houses)


house or greenhouse

structures)



Metals 2009





10










11









12



Conclusions



Acknowledgments


ORCID iDs


References
















13















































14













































15









































16







treatment

∙ Rain barrels

∙ Grey water


water)



Institute (2002)




hot water heaters


heat




∙ Sewage networks







et al 2013)


NH4NO3)



NH4NO3)








(UK)


and UK data

Smith et al (2001)


Mortimer et al

(2003)mdashNH4NO3

appendix C


digestion

∙ Human biosolids

∙ Animal manure




382 MJ kgminus1






Hansen (2006)b


Smith et al (2001)




500 MJ kgminus1d





Hansen (2006)b


Smith et al (2001)









hoop houses)


house or greenhouse

structures)



Metals 2009





10










11









12



Conclusions



Acknowledgments


ORCID iDs


References
















13















































14













































15









































16










11









12



Conclusions



Acknowledgments


ORCID iDs


References
















13















































14













































15









































16









12



Conclusions



Acknowledgments


ORCID iDs


References
















13















































14













































15









































16



Conclusions



Acknowledgments


ORCID iDs


References
















13















































14













































15









































16















































14













































15









































16













































15









































16









































16

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Considerations for reducing food system energy demand while …centaur.reading.ac.uk/74000/1/2017 Mohareb... · 2018. 12. 18. · To cite this article: Eugene Mohareb et al 2017 Environ