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What is the contribution of city-scale actions to the overall food system’s environmental impacts? Assessing water, GHG, and land impacts of future urban food scenarios Dana Boyer, and Anu (Anuradha) Ramaswami Environ. Sci. Technol., Just Accepted Manuscript • DOI: 10.1021/acs.est.7b03176 • Publication Date (Web): 13 Sep 2017 Downloaded from http://pubs.acs.org on September 17, 2017
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Environmental Science & Technology
What is the contribution of city-scale actions to the overall food system’s environmental impacts? Assessing water, GHG, and land impacts of future urban food scenarios Dana Boyer,1* Anu Ramaswami1 *Corresponding author,
[email protected] 1 Center for Science, Technology, and Environmental Policy, Hubert H. Humphrey School of Public Affairs, University of Minnesota, Minneapolis, Minnesota 55455, United States
ABSTRACT
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This paper develops a methodology for individual cities to analyze the in- and trans-boundary
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water, greenhouse gas (GHG) and land impacts of city-scale food system actions. Applied to
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Delhi, India, the analysis demonstrates that city-scale action can rival trans-boundary action,
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though no single city-scale action can rival in all three environmental impacts. Particularly
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improved food waste management within the city (7% system-wide GHG reduction) matches the
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GHG impact of pre-consumer trans-boundary food waste reduction. The systems approach is
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particularly useful in illustrating key tradeoffs/co-benefits. For instance, multiple diet shifts
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achieving GHG reduction are accompanied by an increase in water and/or land impacts. Vertical
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farming technology (VFT) with current application for fruits and vegetables can provide modest
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system-wide water (4%) and land reductions (3%), though implementation within the city may
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raise questions of constraints in water stressed cities—with such a shift in Delhi increasing
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community-wide direct water use by 16%. Improving the nutrition status for the bottom 50% of
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the population to the median diet, is accompanied by proportionally smaller increases of water,
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GHG and land impacts (4%, 9%, and 8%)—increases that can be offset through simultaneous
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city-scale actions, e.g. improved food waste management and VFT.
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INTRODUCTION
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The global food supply is heavily dependent on energy, water, and land resources. Seventy to
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85% of global consumptive water loss is attributed to food production, with 19-29% of global
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greenhouse gas (GHG) emissions emitted from food system activities spanning production 1 ACS Paragon Plus Environment
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through consumption.1,2 Similarly, 12% of global ice-free land area is for agricultural cultivation,
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with a further 28% for pasture.3 With such high resource use, the environmental impact of the
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food system has received substantial attention at national and global scales.4 Attention to these
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interactions from a city perspective, however, has received little attention,5 with the important
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question being: the extent to which city-scale actions shape the larger food system’s
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environmental impact, particularly in terms of GHG, water, and land.
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Despite historic city involvement in food system planning,6–8 with the rise of industrialization
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and refrigerated freight cities became seen as lesser players in shaping the food system9—with
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the food system being associated predominately with agriculture, rather than expanded to include
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not only production, but consumption, transport, retail and food waste management activities,
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acknowledging the linkages between production and demand. Recent conceptualizations of the
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food system that include cities as demand centers,10 embed the city within the larger food system
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that extends well beyond the urban boundary.5
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Facilitated through programs such as the Milan Food Pact,11 the UN FAO’s Food for the Cities12
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and C40’s Food System Network,13 the concerns of urban food systems are many and diverse. At
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the individual city level, municipalities have begun developing objectives and initiatives aimed
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at addressing a multiplicity of urban food concerns, ranging from improving nutrition, health of
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diet, food access/equity, environmental sustainability, management of food waste, and increasing
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local production.14–16 With the city embedded in the larger trans-boundary food system (see
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Figure 1), city-scale food system actions are likely to create changes in the environmental impact
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both locally, and beyond the city boundary. City-scale food system actions are those initiatives
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taken by actors within the city, and could include, changes in consumer behaviors, diets and
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purchasing, urban production, and infrastructure changes of water, energy, and waste
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management that interact with the food system. Cities, however, do not yet have analytical tools
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to assess the extent to which city-scale food system actions affect GHG, water and land impacts
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through the whole of the food system. Such analysis is essential to understand how the multitude
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of urban food system objectives may coincide, or conflict, with concerns of environmental
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sustainability and resource constraints facing the food system both within, and beyond, city
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boundaries. 2 ACS Paragon Plus Environment
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Conceptually, city-scale food system actions can be expected to have large impact on the global
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food system. Urban areas are expected to hold two thirds of the 2050 projected population17 and
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currently responsible for substantial environmental impact, with urban energy use accounting for
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75% of the global GHG emissions18 and large water demand.19 Individual cities have also
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reported the embodied energy of the food supply. Denver, for example, reports food related
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emissions as 10% of its total community-wide infrastructure GHG emissions20 while Delhi
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reports a comparably high 15%.21 Similarly, San Francisco reports that food accounts for 19% of
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total GHG emission footprint of households.22
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metabolism reports found that, across accounting methods, the food sector, on average, had the
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third largest mass and carbon flow by sector, suggesting consistently high impact of urban food
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use. Environmental resource-use footprinting in terms of water has also found the food sector to
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make large contribution.24–26 The embodied land of city food supply specifically has not been
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reported in the scientific literature in a manner disaggregated from ecological footprints, with the
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exception of some grey literature analyses of smaller UK cities.27
A recent analysis23 of 100 cities’ urban
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Thus city-scale action could be highly impactful in shaping the overall environmental impacts of
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the food system on water, GHG and land. Recent advances in urban footprinting methodology
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by Ramaswami et al. 2017 has provided a first framework to capture both in- (i.e. transport
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within the city, in-boundary waste management, urban agriculture) and trans-boundary (i.e.
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agricultural production beyond city boundary) impacts of community-wide urban food demand
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on water and GHG.5 This paper builds upon that framework to incorporate land impacts to assess
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the nexus between water, energy and land, and focuses on conducting a scenario analysis to
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assess the impact of a range of city-scale actions on the overall environmental footprints of the
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food system.
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The key question that this study asks is: what is the contribution of city-scale actions (i.e.
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actions taken within individual cities) to the overall food system’s environmental impacts
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within, and outside, the city boundary? The environmental impacts of focus are water use,
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energy use/GHG and land. The actions include those of multiple actors within the community of
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consumers (households), producers, and community-wide infrastructure providers (i.e. waste
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managers).
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Applied to Delhi, India, this study examines the actions of various diet changes, greater equity of
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household food consumption, increased urban agriculture, improved cooking fuel and food waste
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management, each of which is compared with the reference trans-boundary intervention of
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reducing food waste along the pre-consumer supply chain. Thus, actions occurring within the
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city boundary are compared with pre-consumer actions typically occurring outside of the city
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boundary at a first order level. It should be noted that the motivation for these city-scale actions
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is not solely mitigation of environmental impact, and may include other societal priorities such
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as improved food access, nutritional equity, and support of local food production.
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The development of the linked water-energy/GHG-land footprinting along with scenario analysis
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of city-scale actions is applied to Delhi, India to develop the methodology, though is
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generalizable to any city where the requisite data are available. Benefits of the methodology
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include: ability to compare the environmental impact both within, and beyond the city boundary
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of city-scale action against supply chain and/or production level interventions; informing of
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policy and action in data poor environments; determining largest city policy levers that can
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provide water, GHG and land benefits; and identifying instances of complementary or
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conflicting sustainability outcomes (i.e. equity versus multiple environmental impacts).
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METHODS
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Delhi (in the year 2011; population of 16.4 million) serves as a case study to develop and
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implement the methodology due to a uniquely large amount of food-related data in the public
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domain (See SI). Furthermore, the authors were successful in obtaining city food supply chain
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data, not readily available in many cities, allowing for use of spatially explicit resource intensity
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factors.5 This allows scenario assessment to determine the extent of impact that city-scale actions
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have on the larger food system, without the impediment of limited data.
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The trans-boundary framework of community-wide food supply to a city assessing linked water-
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GHG/energy-land impacts is shown in Figure 1. This figure illustrates the different components
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of the food system, as they intersect with the city (illustrated by the dotted square that includes
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home, businesses and industries) allowing differentiation between in- versus trans-boundary
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impacts.
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Baseline
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Total annual community-wide food use for homes, business, and industry is calculated with data
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first reported by Ramaswami et al. 2017.5 This work further expands the food use analysis,
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delineating use by households of different socio-economic-class (SEC), as determined by the
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Indian Government by monthly per capita expenditure. The authors obtained important data on 5 ACS Paragon Plus Environment
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all components of the food system of agricultural production (in- and outside of the city), freight
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transport, use (household, commercial, industrial) and food waste management (see SI for
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detailed methods). Taking such a community-wide footprinting approach20,28,29 allows
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visualization of potentially beneficial synergies between sectors—greater potential than can be
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realized by looking at each sector in isolation.
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India-specific water consumptive loss (blue and green)30 and GHG31 resource intensity factors of
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production literature studies were supplemented with second order impacts from spatially
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explicit electricity-use and diesel-use for irrigation and on farm machinery.5 Thus, the water
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embodied in electricity production (power plant cooling) and fuel is included in addition to water
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use in crop irrigation. The GHG of production does not include emissions as a result of land use
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change.
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The land footprint of production was calculated in line with methods described by various past
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studies32,33 as a function of community-wide agri-food demand and crop specific yields. India-
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specific crop yields were obtained from FAOSTAT34 and Government of India reports.35,36
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International agri-food imports are relatively small for India, and verified with Delhi’s food
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supply chain data.37 Potential uncertainties include knowledge of multi-cropping and lack of
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country specific animal land area requirements, further discussed in the SI. However, most land-
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footprinting estimates in the literature face similar constraints.33
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Methods for determining resource impact of freight transport, use (home use, commercial
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preparation, industrial processing), and food waste management (solid and waste water) are
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detailed in the SI.
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Scenario analysis
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The scenario analysis quantifies changes in the annual GHG, water and land footprints of Delhi’s
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community-wide food demand from the baseline case, with several city-scale food system
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actions, motivated by a variety of goals described below and summarized in Table 1. Detailed
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methods for each scenario are included in the SI. 6 ACS Paragon Plus Environment
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(a) City equity & health scenario action: Addressing hunger and food security is an explicit
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objective of the Sustainable Development Goals.38 This is particularly relevant in India, a
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country home to nearly 25% of the world’s undernourished population.39 In Delhi’s baseline case
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specifically, the top 5% of the population consumes 2.5 times by mass the quantity of food
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consumed by the lowest 5%. Similarly, the highest 5% consumes much greater quantities of
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fruits and vegetables than the lowest 5%, resulting in greater dietary diversity (92 kg versus 46
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kg per capita per year).5 This scenario therefore assesses the resulting impact of the lower 50%
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of the population by SEC consuming the same diet as the median SEC population—a diet
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deemed sufficient in terms of calories and protein.40
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(b, c, d, e) City diet change scenario action: Much research exists to recommend “sustainable
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diets”—i.e. a diet that meets the nutritional needs of the population while minimizing
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environmental impact.41,42 This research, however, generally speaks only to the Western context,
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assuming a high baseline meat and dairy consumption and availability of alternatives.43,44
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Applicability of these recommendations is questionable in developing country settings, with a
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research need to examine “sustainable diet” shifts in developing countries, conscious of local
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food system conditions and limitations.44 A decrease in rice consumption is of potential interest
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in the Indian context due to: a) in-country concern over high white rice consumption linked to
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diabetes;45 b) rice’s large environmental impact;31 and c) available alternatives within the Delhi
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context (wheat, sorghum, millet). Actions in the diet change scenarios therefore explore the
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impact of a 100% shift from rice to wheat, sorghum, and millet, on a calorie-to-calories basis. A
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shift from meat to pulses is also assessed to provide quantitative comparison with North
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American and European analyses.
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(f, g, h) Urban agriculture scenario action: Urban agriculture is promoted globally for a variety
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of reasons ranging from various environmental benefits to mitigation of urban malnutrition and
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livelihood generation.6,7 Benefits are claimed for both conventional (soil-based) farming methods
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and vertical technology (VFT) (i.e. hydroponics, aero-ponics). VFT, in particular, is promoted
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for high water savings and its independence from land/soil quality.46,47 VFT has received some
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attention in India,48,49 where water scarcity and land degradation can present a challenge for 7 ACS Paragon Plus Environment
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conventional production methods. While types of urban agriculture vary greatly (i.e. community
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gardens v. residential plots v. rooftop etc.), In Delhi, urban agriculture currently takes the form of
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large agricultural lands along the Yamuna River cutting through the middles of the city. Three
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urban agriculture scenario actions therefore assess: 1) a doubling of current soil-based urban
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practices (some fruits, vegetables, milk, grains); 2) conversion of current in-boundary agriculture
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production to VFT (without any increase in production quantity); and 3) conversion of all viable
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crops within the whole of Delhi’s food supply (in- and trans-boundary) to VFT, to be grown
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within Delhi.
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(i) City food preparation scenario action: Fumes of dirty cooking fuels, (i.e. firewood and cow
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dung) have large impact on human health, causing respiratory issues, particularly for women and
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children.50,51 In Delhi, 22% of household cooking energy is provided by dirty fuels, with use
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concentrated in the lower SECs.52 Thus the Government of India provides household subsidies to
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allow greater access of liquefied petroleum gas (LPG) as a cleaner alternative.53 This scenario
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therefore determines the impact of a shift of all current dirty household cooking fuels to LPG.
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(j, k) City food waste management scenario action: While India is estimated to have lesser
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consumer level food waste than developed countries, organic kitchen scraps contribute over 50%
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of total municipal solid waste generated and 80% of household waste.54,55 This results in
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accumulation of food waste on the streets, in landfills and associated methane emissions. This
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scenario action explores the impact change with alternative food waste management options of:
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j) composting and k) anaerobic digestion (AD),56 producing organic fertilizer and in the case of
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AD, electricity generation. Land change of this scenario was not assessed due to data limitation.
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l) Trans-boundary reference scenario action: Pre-consumer food waste is a particular problem in
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India due to poor food transport and storage infrastructure, such as lack of refrigeration.57–59 This
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provides much scope for waste reduction along the supply prior to the city boundary, estimated
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as high as 40-50% in developing countries.60 This scenario analyzes the impact if the percentage
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of pre-consumer food waste is decreased to levels of international best practice. This scenario
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provides a point of comparison of how a lever outside of the city boundary compares with that of
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If the impact of city-scale actions ((a) through (k)) rival those of trans-boundary reduction of
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agri-food waste (action l), it is of high significance, indicating the role a city can play in shaping
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the larger food system.
235 236 Table 1 | Summary of city-scale scenario actions to be analyzed for change of water, GHG and land impacts. Category Scenario a. Lower 50% of the population by socio-economic-class (SEC) City equity & health consuming same diet as median SEC population (deemed sufficient in (a) terms of calories and protein) b. 100% rice calories to wheat c. 100% rice calories to sorghum City diet change (b, c, d, e) d. 100% rice calories to millet e. 100% meat calories to pulses f. Doubling of current urban agriculture production Urban agriculture g. Shift of all viable in-boundary production to VFT (holding production (f, g, h) levels constant) h. Shift of all viable crops to VFT (to be grown in Delhi) City food preparation i. Conversion of all cooking fuels in Delhi to LPG (i) City food waste j. All household organics to composting management k. All household organics to anaerobic digestion (j, k) Trans-boundary reference scenario: Pre-consumer food l. Decrease of pre-consumer food waste to international best practice waste (l)
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RESULTS
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Baseline
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1. Baseline system-wide impacts
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Figure 2 illustrates the whole system-wide GHG (16.9 mil t CO2e), water (17,592 mil m3), and
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land (4.8 mil ha) impacts of Delhi’s baseline food system.
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Different portions of the system are illustrated by the various colors, with the hatched bar portion
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signifying trans-boundary impact and the solid bar portions indicating in-boundary impact. The
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figure illustrates that for both water and land, total impact is dominated by the production stage
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(>99% for both). GHG impact exhibits a more even distribution throughout the whole of the
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supply chain, with only 50% attributed to the production stage, and substantial in-boundary
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emissions from households mainly from cooking-related emissions (12%), commercial (5%)
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food preparation (cooking fuel emissions), industrial processing (5%) and food waste emissions
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from both solid waste landfill methane emissions (6%) and liquid waste (1%).
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2. Distribution of agricultural production impacts by food types
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Figure 3 delineates the production impacts into specific food categories. The vertical bars of the
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figure (Figure 3a-e) show the percentage contribution of each food category to the total impact in
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terms of mass, nutritional intake, GHG, water and land by each of the respective food categories.
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The horizontal bars (Figure 3f) on the far right illustrate the percentage of each food group (and
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associated impact) occurring in- versus trans-boundary. This helps to demonstrate which food
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categories are exhibiting high impact as a result of high quantity of consumption in Delhi versus
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high resource requirement of production. For instance, wheat (burnt orange) contributes 34% of
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total calories, versus a proportionally lesser 11% of GHG impact. Milk (light blue) clearly
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dominates in terms of GHG, with 36% of the total environmental impact of production, with
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substantial contributions to the water (25%) and land (21%) production footprints as well. Meat
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(light purple) makes very little contribute across all footprints due to low consumption.
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3. Delineation of in-versus trans-boundary impact
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Figure 3f illustrates the in- versus trans-boundary distribution of food production by mass to
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meet Delhi’s food demand with the horizontal bars on the right of the figure. This provides
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understanding into the distribution of localized versus trans-boundary impact. Currently 8% of
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food by mass is produced within the city, with substantial in-boundary reliance on meat and milk
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products, provisioning 45% and 15% of total Delhi demand and lesser contributions to rice,
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vegetable and fruit. Thus, while there are some levels of urban production, the majority of
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resource impact occurs beyond the city boundary. This baseline analysis is also important to 12 ACS Paragon Plus Environment
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inform reasonable localization strategies—currently one of the most commonly promoted food
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system interventions.6,7
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4. Impact distribution by socio-economic class
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Figure 4 illustrates the large differences that exist between SECs in terms of water, GHG and
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land impact of food demand. Each of the pie slices represents 10% of the population, with the
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wedge size proportionate to the contribution of that class to the whole of Delhi’s food resource
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impact. Thus an “equitable” society in terms of resource use would have uniformly sized slices.
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The lowest (5th) and highest classes (100th) are outlined to illustrate the large difference between
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the lowest and highest classes. For instance, in the case of GHG, the wealthiest class is
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responsible for 17% of the impact, while the lowest class only 6%.
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Scenario analysis
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1. System-wide impact
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Figure 5 summarizes the change in full system-wide GHG, water, and land impacts with each of
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the city-scale food system actions described in Table 1. The bottom axis indicates the percentage
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change of the total food system’s (in- plus trans-boundary) land (green), water (blue) and GHG
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(red) footprint with each of the food system interventions ((a) through (l) as described in Table
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1). Second order impacts are indicated with hatching. 13 ACS Paragon Plus Environment
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City equity & health: When the bottom 50% of the population consumes the diet of the median
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class (Figure 5a), system-wide GHG, water and land impacts increase by 4%, 9%, and 8%,
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respectively.
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City diet change: A 100% shift of rice to wheat reduces total system-wide water and GHG
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impacts of 3% each with a slight increase in land footprint (
