What Is the Contribution of City-Scale Actions to the Overall Food

Sep 13, 2017 - Center for Science, Technology, and Environmental Policy, Hubert H. Humphrey School of Public Affairs, University of Minnesota, Minneap...
0 downloads 3 Views 1MB Size
Subscriber access provided by Oakland University Libraries

Article

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

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

Environmental Science & Technology is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 27

1 2 3 4 5 6 7 8 9 10 11

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

12 13

This paper develops a methodology for individual cities to analyze the in- and trans-boundary

14

water, greenhouse gas (GHG) and land impacts of city-scale food system actions. Applied to

15

Delhi, India, the analysis demonstrates that city-scale action can rival trans-boundary action,

16

though no single city-scale action can rival in all three environmental impacts. Particularly

17

improved food waste management within the city (7% system-wide GHG reduction) matches the

18

GHG impact of pre-consumer trans-boundary food waste reduction. The systems approach is

19

particularly useful in illustrating key tradeoffs/co-benefits. For instance, multiple diet shifts

20

achieving GHG reduction are accompanied by an increase in water and/or land impacts. Vertical

21

farming technology (VFT) with current application for fruits and vegetables can provide modest

22

system-wide water (4%) and land reductions (3%), though implementation within the city may

23

raise questions of constraints in water stressed cities—with such a shift in Delhi increasing

24

community-wide direct water use by 16%. Improving the nutrition status for the bottom 50% of

25

the population to the median diet, is accompanied by proportionally smaller increases of water,

26

GHG and land impacts (4%, 9%, and 8%)—increases that can be offset through simultaneous

27

city-scale actions, e.g. improved food waste management and VFT.

28 29 30

INTRODUCTION

31 32

The global food supply is heavily dependent on energy, water, and land resources. Seventy to

33

85% of global consumptive water loss is attributed to food production, with 19-29% of global

34

greenhouse gas (GHG) emissions emitted from food system activities spanning production 1 ACS Paragon Plus Environment

Environmental Science & Technology

Page 2 of 27

35

through consumption.1,2 Similarly, 12% of global ice-free land area is for agricultural cultivation,

36

with a further 28% for pasture.3 With such high resource use, the environmental impact of the

37

food system has received substantial attention at national and global scales.4 Attention to these

38

interactions from a city perspective, however, has received little attention,5 with the important

39

question being: the extent to which city-scale actions shape the larger food system’s

40

environmental impact, particularly in terms of GHG, water, and land.

41 42

Despite historic city involvement in food system planning,6–8 with the rise of industrialization

43

and refrigerated freight cities became seen as lesser players in shaping the food system9—with

44

the food system being associated predominately with agriculture, rather than expanded to include

45

not only production, but consumption, transport, retail and food waste management activities,

46

acknowledging the linkages between production and demand. Recent conceptualizations of the

47

food system that include cities as demand centers,10 embed the city within the larger food system

48

that extends well beyond the urban boundary.5

49 50

Facilitated through programs such as the Milan Food Pact,11 the UN FAO’s Food for the Cities12

51

and C40’s Food System Network,13 the concerns of urban food systems are many and diverse. At

52

the individual city level, municipalities have begun developing objectives and initiatives aimed

53

at addressing a multiplicity of urban food concerns, ranging from improving nutrition, health of

54

diet, food access/equity, environmental sustainability, management of food waste, and increasing

55

local production.14–16 With the city embedded in the larger trans-boundary food system (see

56

Figure 1), city-scale food system actions are likely to create changes in the environmental impact

57

both locally, and beyond the city boundary. City-scale food system actions are those initiatives

58

taken by actors within the city, and could include, changes in consumer behaviors, diets and

59

purchasing, urban production, and infrastructure changes of water, energy, and waste

60

management that interact with the food system. Cities, however, do not yet have analytical tools

61

to assess the extent to which city-scale food system actions affect GHG, water and land impacts

62

through the whole of the food system. Such analysis is essential to understand how the multitude

63

of urban food system objectives may coincide, or conflict, with concerns of environmental

64

sustainability and resource constraints facing the food system both within, and beyond, city

65

boundaries. 2 ACS Paragon Plus Environment

Page 3 of 27

Environmental Science & Technology

66 67

Conceptually, city-scale food system actions can be expected to have large impact on the global

68

food system. Urban areas are expected to hold two thirds of the 2050 projected population17 and

69

currently responsible for substantial environmental impact, with urban energy use accounting for

70

75% of the global GHG emissions18 and large water demand.19 Individual cities have also

71

reported the embodied energy of the food supply. Denver, for example, reports food related

72

emissions as 10% of its total community-wide infrastructure GHG emissions20 while Delhi

73

reports a comparably high 15%.21 Similarly, San Francisco reports that food accounts for 19% of

74

total GHG emission footprint of households.22

75

metabolism reports found that, across accounting methods, the food sector, on average, had the

76

third largest mass and carbon flow by sector, suggesting consistently high impact of urban food

77

use. Environmental resource-use footprinting in terms of water has also found the food sector to

78

make large contribution.24–26 The embodied land of city food supply specifically has not been

79

reported in the scientific literature in a manner disaggregated from ecological footprints, with the

80

exception of some grey literature analyses of smaller UK cities.27

A recent analysis23 of 100 cities’ urban

81 82

Thus city-scale action could be highly impactful in shaping the overall environmental impacts of

83

the food system on water, GHG and land. Recent advances in urban footprinting methodology

84

by Ramaswami et al. 2017 has provided a first framework to capture both in- (i.e. transport

85

within the city, in-boundary waste management, urban agriculture) and trans-boundary (i.e.

86

agricultural production beyond city boundary) impacts of community-wide urban food demand

87

on water and GHG.5 This paper builds upon that framework to incorporate land impacts to assess

88

the nexus between water, energy and land, and focuses on conducting a scenario analysis to

89

assess the impact of a range of city-scale actions on the overall environmental footprints of the

90

food system.

91 92

The key question that this study asks is: what is the contribution of city-scale actions (i.e.

93

actions taken within individual cities) to the overall food system’s environmental impacts

94

within, and outside, the city boundary? The environmental impacts of focus are water use,

95

energy use/GHG and land. The actions include those of multiple actors within the community of

3 ACS Paragon Plus Environment

Environmental Science & Technology

Page 4 of 27

96

consumers (households), producers, and community-wide infrastructure providers (i.e. waste

97

managers).

98 99

Applied to Delhi, India, this study examines the actions of various diet changes, greater equity of

100

household food consumption, increased urban agriculture, improved cooking fuel and food waste

101

management, each of which is compared with the reference trans-boundary intervention of

102

reducing food waste along the pre-consumer supply chain. Thus, actions occurring within the

103

city boundary are compared with pre-consumer actions typically occurring outside of the city

104

boundary at a first order level. It should be noted that the motivation for these city-scale actions

105

is not solely mitigation of environmental impact, and may include other societal priorities such

106

as improved food access, nutritional equity, and support of local food production.

107 108

The development of the linked water-energy/GHG-land footprinting along with scenario analysis

109

of city-scale actions is applied to Delhi, India to develop the methodology, though is

110

generalizable to any city where the requisite data are available. Benefits of the methodology

111

include: ability to compare the environmental impact both within, and beyond the city boundary

112

of city-scale action against supply chain and/or production level interventions; informing of

113

policy and action in data poor environments; determining largest city policy levers that can

114

provide water, GHG and land benefits; and identifying instances of complementary or

115

conflicting sustainability outcomes (i.e. equity versus multiple environmental impacts).

116 117

METHODS

118 119

Delhi (in the year 2011; population of 16.4 million) serves as a case study to develop and

120

implement the methodology due to a uniquely large amount of food-related data in the public

121

domain (See SI). Furthermore, the authors were successful in obtaining city food supply chain

122

data, not readily available in many cities, allowing for use of spatially explicit resource intensity

123

factors.5 This allows scenario assessment to determine the extent of impact that city-scale actions

124

have on the larger food system, without the impediment of limited data.

125

4 ACS Paragon Plus Environment

Page 5 of 27

Environmental Science & Technology

126

The trans-boundary framework of community-wide food supply to a city assessing linked water-

127

GHG/energy-land impacts is shown in Figure 1. This figure illustrates the different components

128

of the food system, as they intersect with the city (illustrated by the dotted square that includes

129

home, businesses and industries) allowing differentiation between in- versus trans-boundary

130

impacts.

131 132

Baseline

133 134

Total annual community-wide food use for homes, business, and industry is calculated with data

135

first reported by Ramaswami et al. 2017.5 This work further expands the food use analysis,

136

delineating use by households of different socio-economic-class (SEC), as determined by the

137

Indian Government by monthly per capita expenditure. The authors obtained important data on 5 ACS Paragon Plus Environment

Environmental Science & Technology

Page 6 of 27

138

all components of the food system of agricultural production (in- and outside of the city), freight

139

transport, use (household, commercial, industrial) and food waste management (see SI for

140

detailed methods). Taking such a community-wide footprinting approach20,28,29 allows

141

visualization of potentially beneficial synergies between sectors—greater potential than can be

142

realized by looking at each sector in isolation.

143 144

India-specific water consumptive loss (blue and green)30 and GHG31 resource intensity factors of

145

production literature studies were supplemented with second order impacts from spatially

146

explicit electricity-use and diesel-use for irrigation and on farm machinery.5 Thus, the water

147

embodied in electricity production (power plant cooling) and fuel is included in addition to water

148

use in crop irrigation. The GHG of production does not include emissions as a result of land use

149

change.

150 151

The land footprint of production was calculated in line with methods described by various past

152

studies32,33 as a function of community-wide agri-food demand and crop specific yields. India-

153

specific crop yields were obtained from FAOSTAT34 and Government of India reports.35,36

154

International agri-food imports are relatively small for India, and verified with Delhi’s food

155

supply chain data.37 Potential uncertainties include knowledge of multi-cropping and lack of

156

country specific animal land area requirements, further discussed in the SI. However, most land-

157

footprinting estimates in the literature face similar constraints.33

158 159

Methods for determining resource impact of freight transport, use (home use, commercial

160

preparation, industrial processing), and food waste management (solid and waste water) are

161

detailed in the SI.

162 163

Scenario analysis

164 165

The scenario analysis quantifies changes in the annual GHG, water and land footprints of Delhi’s

166

community-wide food demand from the baseline case, with several city-scale food system

167

actions, motivated by a variety of goals described below and summarized in Table 1. Detailed

168

methods for each scenario are included in the SI. 6 ACS Paragon Plus Environment

Page 7 of 27

Environmental Science & Technology

169 170

(a) City equity & health scenario action: Addressing hunger and food security is an explicit

171

objective of the Sustainable Development Goals.38 This is particularly relevant in India, a

172

country home to nearly 25% of the world’s undernourished population.39 In Delhi’s baseline case

173

specifically, the top 5% of the population consumes 2.5 times by mass the quantity of food

174

consumed by the lowest 5%. Similarly, the highest 5% consumes much greater quantities of

175

fruits and vegetables than the lowest 5%, resulting in greater dietary diversity (92 kg versus 46

176

kg per capita per year).5 This scenario therefore assesses the resulting impact of the lower 50%

177

of the population by SEC consuming the same diet as the median SEC population—a diet

178

deemed sufficient in terms of calories and protein.40

179 180

(b, c, d, e) City diet change scenario action: Much research exists to recommend “sustainable

181

diets”—i.e. a diet that meets the nutritional needs of the population while minimizing

182

environmental impact.41,42 This research, however, generally speaks only to the Western context,

183

assuming a high baseline meat and dairy consumption and availability of alternatives.43,44

184

Applicability of these recommendations is questionable in developing country settings, with a

185

research need to examine “sustainable diet” shifts in developing countries, conscious of local

186

food system conditions and limitations.44 A decrease in rice consumption is of potential interest

187

in the Indian context due to: a) in-country concern over high white rice consumption linked to

188

diabetes;45 b) rice’s large environmental impact;31 and c) available alternatives within the Delhi

189

context (wheat, sorghum, millet). Actions in the diet change scenarios therefore explore the

190

impact of a 100% shift from rice to wheat, sorghum, and millet, on a calorie-to-calories basis. A

191

shift from meat to pulses is also assessed to provide quantitative comparison with North

192

American and European analyses.

193 194

(f, g, h) Urban agriculture scenario action: Urban agriculture is promoted globally for a variety

195

of reasons ranging from various environmental benefits to mitigation of urban malnutrition and

196

livelihood generation.6,7 Benefits are claimed for both conventional (soil-based) farming methods

197

and vertical technology (VFT) (i.e. hydroponics, aero-ponics). VFT, in particular, is promoted

198

for high water savings and its independence from land/soil quality.46,47 VFT has received some

199

attention in India,48,49 where water scarcity and land degradation can present a challenge for 7 ACS Paragon Plus Environment

Environmental Science & Technology

Page 8 of 27

200

conventional production methods. While types of urban agriculture vary greatly (i.e. community

201

gardens v. residential plots v. rooftop etc.), In Delhi, urban agriculture currently takes the form of

202

large agricultural lands along the Yamuna River cutting through the middles of the city. Three

203

urban agriculture scenario actions therefore assess: 1) a doubling of current soil-based urban

204

practices (some fruits, vegetables, milk, grains); 2) conversion of current in-boundary agriculture

205

production to VFT (without any increase in production quantity); and 3) conversion of all viable

206

crops within the whole of Delhi’s food supply (in- and trans-boundary) to VFT, to be grown

207

within Delhi.

208 209

(i) City food preparation scenario action: Fumes of dirty cooking fuels, (i.e. firewood and cow

210

dung) have large impact on human health, causing respiratory issues, particularly for women and

211

children.50,51 In Delhi, 22% of household cooking energy is provided by dirty fuels, with use

212

concentrated in the lower SECs.52 Thus the Government of India provides household subsidies to

213

allow greater access of liquefied petroleum gas (LPG) as a cleaner alternative.53 This scenario

214

therefore determines the impact of a shift of all current dirty household cooking fuels to LPG.

215 216

(j, k) City food waste management scenario action: While India is estimated to have lesser

217

consumer level food waste than developed countries, organic kitchen scraps contribute over 50%

218

of total municipal solid waste generated and 80% of household waste.54,55 This results in

219

accumulation of food waste on the streets, in landfills and associated methane emissions. This

220

scenario action explores the impact change with alternative food waste management options of:

221

j) composting and k) anaerobic digestion (AD),56 producing organic fertilizer and in the case of

222

AD, electricity generation. Land change of this scenario was not assessed due to data limitation.

223 224

l) Trans-boundary reference scenario action: Pre-consumer food waste is a particular problem in

225

India due to poor food transport and storage infrastructure, such as lack of refrigeration.57–59 This

226

provides much scope for waste reduction along the supply prior to the city boundary, estimated

227

as high as 40-50% in developing countries.60 This scenario analyzes the impact if the percentage

228

of pre-consumer food waste is decreased to levels of international best practice. This scenario

229

provides a point of comparison of how a lever outside of the city boundary compares with that of

230

city-scale actions. 8 ACS Paragon Plus Environment

Page 9 of 27

Environmental Science & Technology

231 232

If the impact of city-scale actions ((a) through (k)) rival those of trans-boundary reduction of

233

agri-food waste (action l), it is of high significance, indicating the role a city can play in shaping

234

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)

237 238 239 240 241 242 243 244 245 246 9 ACS Paragon Plus Environment

Environmental Science & Technology

247

Page 10 of 27

RESULTS

248 249

Baseline

250 251

1. Baseline system-wide impacts

252

Figure 2 illustrates the whole system-wide GHG (16.9 mil t CO2e), water (17,592 mil m3), and

253

land (4.8 mil ha) impacts of Delhi’s baseline food system.

254

Different portions of the system are illustrated by the various colors, with the hatched bar portion

255

signifying trans-boundary impact and the solid bar portions indicating in-boundary impact. The

256

figure illustrates that for both water and land, total impact is dominated by the production stage

257

(>99% for both). GHG impact exhibits a more even distribution throughout the whole of the

258

supply chain, with only 50% attributed to the production stage, and substantial in-boundary

259

emissions from households mainly from cooking-related emissions (12%), commercial (5%)

260

food preparation (cooking fuel emissions), industrial processing (5%) and food waste emissions

261

from both solid waste landfill methane emissions (6%) and liquid waste (1%).

262 263 10 ACS Paragon Plus Environment

Page 11 of 27

Environmental Science & Technology

264

2. Distribution of agricultural production impacts by food types

265

Figure 3 delineates the production impacts into specific food categories. The vertical bars of the

266

figure (Figure 3a-e) show the percentage contribution of each food category to the total impact in

267

terms of mass, nutritional intake, GHG, water and land by each of the respective food categories.

268

The horizontal bars (Figure 3f) on the far right illustrate the percentage of each food group (and

269

associated impact) occurring in- versus trans-boundary. This helps to demonstrate which food

270

categories are exhibiting high impact as a result of high quantity of consumption in Delhi versus

271

high resource requirement of production. For instance, wheat (burnt orange) contributes 34% of

272

total calories, versus a proportionally lesser 11% of GHG impact. Milk (light blue) clearly

273

dominates in terms of GHG, with 36% of the total environmental impact of production, with

274

substantial contributions to the water (25%) and land (21%) production footprints as well. Meat

275

(light purple) makes very little contribute across all footprints due to low consumption.

276 277

11 ACS Paragon Plus Environment

Environmental Science & Technology

Page 12 of 27

278 279 280

3. Delineation of in-versus trans-boundary impact

281

Figure 3f illustrates the in- versus trans-boundary distribution of food production by mass to

282

meet Delhi’s food demand with the horizontal bars on the right of the figure. This provides

283

understanding into the distribution of localized versus trans-boundary impact. Currently 8% of

284

food by mass is produced within the city, with substantial in-boundary reliance on meat and milk

285

products, provisioning 45% and 15% of total Delhi demand and lesser contributions to rice,

286

vegetable and fruit. Thus, while there are some levels of urban production, the majority of

287

resource impact occurs beyond the city boundary. This baseline analysis is also important to 12 ACS Paragon Plus Environment

Page 13 of 27

Environmental Science & Technology

288

inform reasonable localization strategies—currently one of the most commonly promoted food

289

system interventions.6,7

290 291

4. Impact distribution by socio-economic class

292

Figure 4 illustrates the large differences that exist between SECs in terms of water, GHG and

293

land impact of food demand. Each of the pie slices represents 10% of the population, with the

294

wedge size proportionate to the contribution of that class to the whole of Delhi’s food resource

295

impact. Thus an “equitable” society in terms of resource use would have uniformly sized slices.

296

The lowest (5th) and highest classes (100th) are outlined to illustrate the large difference between

297

the lowest and highest classes. For instance, in the case of GHG, the wealthiest class is

298

responsible for 17% of the impact, while the lowest class only 6%.

299

300

Scenario analysis

301 302

1. System-wide impact

303

Figure 5 summarizes the change in full system-wide GHG, water, and land impacts with each of

304

the city-scale food system actions described in Table 1. The bottom axis indicates the percentage

305

change of the total food system’s (in- plus trans-boundary) land (green), water (blue) and GHG

306

(red) footprint with each of the food system interventions ((a) through (l) as described in Table

307

1). Second order impacts are indicated with hatching. 13 ACS Paragon Plus Environment

Environmental Science & Technology

Page 14 of 27

308 14 ACS Paragon Plus Environment

Page 15 of 27

Environmental Science & Technology

309

City equity & health: When the bottom 50% of the population consumes the diet of the median

310

class (Figure 5a), system-wide GHG, water and land impacts increase by 4%, 9%, and 8%,

311

respectively.

312 313

City diet change: A 100% shift of rice to wheat reduces total system-wide water and GHG

314

impacts of 3% each with a slight increase in land footprint (