October 2023
Part 2
From Field to Bin:
The Environmental Impacts
of U.S. Food Waste
Management Pathways
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Disclaimer
This document has been reviewed in accordance with U.S. Environmental Protection Agency (EPA)
policy and approved for publication.
Authors
U.S. EPA
Shannon Kenny
Jenny Stephenson
Alexandra Stern (ORISE)
Juliana Beecher (ORISE)
Eastern Research Group, Inc. (ERG)
Ben Morelli
Andrew Henderson
Emelyn Chiang
Andrew Beck
Sarah Cashman
Emily Wexler
Kyle McGaughy
Abby Martell
Reviewers
EPA would like to thank the following people for their independent peer review of the report:
Sally Brown, Ph.D., University of Washington
Nora Goldstein, B.A., BioCycle
Xiaobo Xue Romeiko, Ph.D., University at Albany, State University of New York
Acknowledgements
EPA would like to thank the following people for their contributions to the report: Claudia Fabiano,
Catherine Birney and Kameron King (ORISE).
This research was supported in part by an appointment to the U.S. EPA Research Participation Program
administered by the Oak Ridge Institute for Science and Education (ORISE) through an interagency
agreement between the U.S. Department of Energy (DOE) and the U.S. EPA. ORISE is managed by Oak
Ridge Associated Universities under DOE contract number DE-SC0014664.
This report was prepared with support from ERG, under U.S. EPA Contract No. EP-C-16-015 and U.S.
EPA Contract No. 68HERC21D0003. The external peer review of the report was coordinated by Versar,
Inc. under U.S. EPA Contract No. EP-C-17-023.
Disclaimer and Acknowledgements
i
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List of Abbreviations
AD anaerobic digestion
ARB antibiotic-resistant bacteria
ASP aerated static pile
BOD biochemical oxygen demand
CHP combined heat and power
CCheq CO2 equivalent
COD chemical oxygen demand
DOC degradable organic carbon
DOCf degradable organic carbon fraction
EPA U.S. Environmental Protection Agency
FOG fats, oils, and grease
GHG greenhouse gas
GWP global warming potential
HTC hydrothermal carbonization
km kilometer
LCA life cycle assessment
LFG landfill gas
MSW municipal solid waste
MTC02eq metric tons of CO2 equivalent
Neq N equivalents
OFMSW organic fraction of municipal solid waste
PFAS polyfluoroalkyl substances
RDF refuse derived fuel
S02eq SO2 equivalents
SOC soil organic carbon
SOM soil organic matter
t metric ton (1,000 kilograms)
TSS total suspended solids
USD U.S. dollars
VOC volatile organic compound
WARM Waste Reduction Model (EPA)
WRRF water resource recovery facility
WWT wastewater treatment
List of Abbreviations
ii
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List of Chemical Symbols
c
carbon
ch4
methane
co2
carbon dioxide
Hg
mercury
K
potassium
N
nitrogen
N2O
nitrous oxide
NHs
ammonia
NO2
nitrogen dioxide
NOs-
nitrate
NOx
nitrogen oxides
P
phosphorus
PM
particulate matter
PM2.5
particulate matter (2.5 micrometers in diameter and smaller)
SO2
sulfur dioxide
SOx
sulfur oxides
List of Chemical Symbols
Hi
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Table of Contents
List of Abbreviations ii
List of Chemical Symbols iii
Executive Summary ix
Methodology ix
Conclusions x
Chapter 1 Introduction 1-1
1.1 Purpose 1-1
1.2 Scope 1-1
1.3 Definitions 1-2
1.4 Background 1-4
1.5 Approach and Research Methods 1-6
1.6 Report Overview 1-8
Chapter 2 Wasted Food Pathways 2-1
2.1 Source Reduction 2-3
2.2 Donation 2-4
2.3 Upcycling 2-6
2.4 Anaerobic Digestion 2-8
2.5 Animal Feed 2-15
2.6 Composting 2-18
2.7 Controlled Combustion 2-23
2.8 Land Application 2-27
2.9 Landfill 2-29
2.10 Sewer/Wastewater Treatment 2-32
2.11 Unharvested/Plowed In 2-36
2.12 Emerging Pathways 2-37
2.13 Key Issues Across Pathways 2-37
Chapter 3 Life Cycle Assessment 3-1
3.1 Environmental Indicators 3-1
3.2 Methodology 3-4
3.3 Qualitative Summary of Pathway Environmental Impacts and Benefits 3-9
Table of Contents iv
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3.4 Quantitative Comparison of Pathways Across Studies 3-11
3.5 Quantitative Comparison of Pathways Within Studies 3-34
3.6 Soil Health 3-39
3.7 Limitations of LCA Review 3-41
3.8 Summary of LCA Review Findings 3-42
3.9 LCA Conclusions 3-51
Chapter 4 Circularity Assessment 4-1
4.1 Circularity Themes 4-2
4.2 Methodology 4-5
4.3 Waste Prevention 4-5
4.4 Value 4-6
4.5 Purity 4-10
4.6 Regeneration 4-14
4.7 Alternative Methods for Circularity Assessments 4-22
4.8 Limitations of Circularity Assessment 4-24
4.9 Circularity Assessment Conclusions 4-25
Chapter 5 Discussion and Conclusions 5-1
5.1 Comparing Methodologies and Results 5-1
5.2 Effects of Wasted Food on Pathway Performance 5-7
5.3 Synthesizing Results into New Ranking of Wasted Food Pathways 5-8
Chapter 6 Implications and Research Gaps 6-1
6.1 Comparing Conclusions to Other Hierarchies 6-1
6.2 Using the Hierarchy 6-4
6.3 Implications 6-4
6.4 Research Gaps 6-5
Chapter 7 References 7-1
List of Appendices
Appendix A Literature Search Methods
Appendix B Energy, Fertilizer, and Carbon Sequestration Offsets
Appendix C Description of Approach to Compare Impact Metrics
Appendix D Extracted Data Values
Appendix E Other Emerging Pathways
Appendix F Endnotes
Table of Contents
v
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List of Tables and Figures
List of Tables
Table 1-1. Definitions of wasted food pathways 1-3
Table 1-2. Quantitative thresholds used to make statement about the magnitude of driver
contributions 1-7
Table 2-1. Donation: environmental drivers 2-5
Table 2-2. Upcycling: environmental drivers 2-7
Table 2-3. Anaerobic digestion technologies 2-10
Table 2-4. Anaerobic digestion: environmental drivers 2-14
Table 2-5. Animal feed technologies 2-16
Table 2-6. Animal feed: environmental drivers 2-17
Table 2-7. Composting technologies 2-19
Table 2-8. Composting: environmental drivers 2-22
Table 2-9. Controlled combustion technologies 2-24
Table 2-10. Controlled combustion: environmental drivers 2-26
Table 2-11. Land application: environmental drivers 2-28
Table 2-12. Landfill: environmental drivers 2-31
Table 2-13. Sewer / wastewater treatment: environmental drivers 2-35
Table 2-14. Unharvested / plowed in: environmental drivers 2-36
Table 2-15. High-level summary of allowable contamination, required homogeneity, and
collection requirements for wasted food pathways 2-42
Table 3-1. Environmental indicators 3-2
Table 3-2. Summary of environmental impacts and benefits, by pathway 3-9
Table 3-3. Inter-study analysis (Section 3.3) scope criteria 3-12
Table 3-4. GWP impacts, with and without carbon sequestration, per metric ton wasted
food 3-18
Table 3-5. Median, range (25th-75th percentile), and scenario count for six
environmental impacts per metric ton of wasted food, by pathway 3-31
Table 3-6. Relative environmental impacts by wasted food pathway (median impact/
metric ton wasted food) 3-33
Table 3-7. Summary of wasted food pathway impacts and benefits, by environmental
indicator 3-43
Table 4-1. Key circularity themes 4-2
Table 4-2. Destinations for nutrient outputs from wasted food pathways 4-7
List of Tables and Figures vi
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Table 4-3. Waste streams commonly managed with wasted food 4-11
Table 4-4. Mean nitrogen composition of wasted food-derived soil amendments 4-16
Table 4-5. Carbon content of wasted food and wasted food-derived digestate 4-17
Table 4-6. Mapping of wasted food pathways to the circular strategies of the "R"
framework 4-23
List of Figures
Figure ES-1. The Wasted Food Scale: EPA's new ranking of wasted food pathways
based on life cycle assessment and circularity assessment x
Figure 1-1. Percentage of wasted food managed by each pathway, by sector in which
the wasted food is generated 1-4
Figure 1-2. EPA's previous ranking of wasted food pathways 1-5
Figure 2-1. Generic system diagram 2-2
Figure 2-2. Diagram of donation 2-4
Figure 2-3. Diagram of upcycling 2-6
Figure 2-4. Diagram distinguishing anaerobic digestion and sewer/WWT pathways 2-8
Figure 2-5. Diagram of anaerobic digestion and co-digestion of wasted food 2-9
Figure 2-6. Diagram of wasted food conversion to animal feed 2-15
Figure 2-7. Diagram of wasted food composting, including a prominent co-waste such as
municipal green waste 2-18
Figure 2-8. Diagram of controlled combustion of wasted food (as part of MSW) with
energy recovery 2-23
Figure 2-9. Diagram of direct land application of wasted food 2-27
Figure 2-10. Diagram of wasted food landfilling with energy recovery 2-29
Figure 2-11. Diagram of wasted food processing via sewer/wastewater treatment 2-32
Figure 3-1. Distribution of wasted food pathways assessed in reviewed studies 3-4
Figure 3-2. Distribution of environmental indicators assessed in reviewed studies 3-5
Figure 3-3. Comparison of global warming potential of wasted food pathways across
LCA studies 3-15
Figure 3-4. Comparison of energy demand of wasted food pathways across LCA studies 3-19
Figure 3-5. Comparison of terrestrial acidification potential of wasted food pathways
across LCA studies 3-22
Figure 3-6. Comparison of eutrophication impact of wasted food pathways across LCA
studies 3-25
Figure 3-7. Comparison of water consumption of wasted food pathways across LCA
studies 3-26
Figure 3-8. Comparison of land occupation of wasted food pathways across LCA studies 3-28
Figure 3-9. Comparison of environmental impact of wasted food pathways within studies 3-37
Figure 3-9 Comparison of environmental impact of wasted food pathways within studies
(continued) 3-38
Figure 3-10. Global warming potential: ranking of wasted food pathways 3-52
List of Tables and Figures vii
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Figure 3-11. All LCA indicators: ranking of wasted food pathways 3-52
Figure 4-1. Comparing a linear economy and a circular economy 4-1
Figure 4-2. Waste prevention: alignment of wasted food pathways 4-5
Figure 4-3. Value: alignment of wasted food pathways 4-9
Figure 4-4. Purity: alignment of wasted food pathways 4-13
Figure 4-5. Regeneration: alignment of wasted food pathways 4-21
Figure 4-6. Summary of circularity theme rankings, by pathway 4-26
Figure 4-7. Ranking of wasted food pathways based on circularity 4-27
Figure 5-1. Comparing LCA and circularity assessment methodologies 5-3
Figure 5-2. Summary of LCA (left) and circularity (right) assessment rankings of wasted
food pathways 5-4
Figure 5-3. The Wasted Food Scale: EPA's new ranking of wasted food pathways based
upon LCA and circularity assessment 5-8
List of Tables and Figures viii
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Executive Summary
Over one-third of the food produced in the United States is never eaten, wasting the resources used to
produce it and creating a myriad of environmental impacts. Wasted food is the single most common
material landfilled and incinerated in the United States, comprising 24% and 22% of landfilled and
combusted municipal solid waste (MSW), respectively, presenting opportunities for increased prevention
and recycling.
The purpose of this report is to investigate the environmental impacts and contributions to a circular
economy of eleven common pathways to manage wasted food - from source reduction to composting to
landfill. The report presents a new ranking of the wasted food pathways, from most to least
environmentally preferable. EPA's new ranking—called the Wasted Food Scale—replaces the Agency's
Food Recovery Hierarchy developed in the 1990s. The Wasted Food Scale reflects the latest science as
well as technological advances and changes in operational practices in the wasted food pathways since
the Food Recovery Hierarchy was developed. Wasted food is generated all along the food supply chain,
and thus the audience for this report includes a broad range of stakeholders from farms to food
businesses to households to waste managers, as well as policymakers seeking advice on how to reduce
the environmental impacts of wasted food.
Methodology
The report investigates eleven common wasted food pathways: source reduction, donation, upcycling
(i.e., repurposing wasted food into new food for human consumption), animal feed, anaerobic digestion,
composting, controlled combustion (i.e., incineration), land application (i.e., applying raw wasted food to
soil), landfilling, sewer/wastewater treatment (i.e., sending wasted food "down the drain"), and
unharvested/plowed in (i.e., leaving crops in the field). Wasted food is defined in the report as food meant
for human consumption but not ultimately consumed by humans. Food crops grown for other purposes,
such as biofuels or animal feed, are outside the scope of the report. Wherever possible, the report
focuses specifically on wasted food as the feedstock for the pathway, taking into account the specific
properties of food (e.g., moisture level, energy value, and decay rate) and how they affect a pathway's
impacts and benefits. Thus, the findings are specific to wasted food and not applicable to other
components of MSW. The report does not consider social or economic factors.
The report employs two methodologies to assess the pathways: Life Cycle Assessment (LCA) and
Circularity Assessment. First, the report considers environmental impacts of the wasted food pathways
through a quantitative and qualitative review of the LCA literature. LCA is widely recognized for its ability
to identify issues and assess tradeoffs across the value chain and across environmental impacts.
Approximately 250 studies were reviewed in depth, covering global warming potential, soil carbon
sequestration, energy demand, acidification, particulate matter formation, human toxicity, ecotoxicity,
eutrophication, water consumption, land occupation, and soil health. Second, the report presents a
qualitative assessment of each pathway's contribution to a circular economy, focusing on the
environmental aspects of circularity. The goal of a circular economy is to decouple economic growth from
resource extraction by capturing greater value from existing products and materials. This contrasts with
the traditional linear "take-make-use-dispose" economy where waste is seen as something to "send
away" or dispose. In the assessment, pathways are evaluated against four circularity themes consistent
with the definition of circularity presented in the Save Our Seas Act 2.0: preventing waste and having
outputs maintain their highest potential value, stay free of contaminants to enable reuse, and help to
regenerate ecosystems through improved soil health and climate resilience.
The two approaches utilized in this report - LCA and circularity assessment - are complementary and
together inform the conclusions of this report and the Wasted Food Scale. There is precedent in the
literature for combining these methodologies as it can reveal trade-offs between circularity and
Executive Summary
ix
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environmental impacts and among environmental impacts, helping decision-makers avoid shifting
problems from one area to another. The LCA review enabled quantitative comparison of some
environmental indicators, while the circularity assessment provided insight into other areas of
environmental concern not covered by the LCAs (e.g., soil health and resource conservation). Pathway
rankings from each methodology are provided in the main body of the report. Key differences between
the results of the two assessments arise from how each methodology values the recovery of energy
versus the recovery of nutrients, considers emissions and releases during the waste management
process, and assesses soil health and ecosystem benefits. Results of the two assessments were merged
through a combination of quantitative analysis and qualitative professional judgment by a panel of
experts.
Conclusions
EPA presents the new Wasted Food Scale (see Figure ES-1), ranking wasted food pathways from most
to least environmentally preferable, based on LCA and circularity assessment. Pathways are grouped into
tiers where EPA determined them to have equivalent performance. The Scale emphasizes the
importance of prevention and of diverting food waste from the sewer/wastewater treatment, landfill, and
controlled combustion (i.e., incineration) pathways. The Wasted Food Scale replaces EPA's Food
Recovery Hierarchy.
Anaerobic Digestion
with disposal of digestate/biosolids
Donate
Upcycle
Feed
Animals
Compost
Anaerobic
Digestion
with beneficial use of
digestate/biosolids
Leave
Unharvested
lOdo.
o
(/)
H
"0
73
m
Prevent Wasted Food
Produce, buy, and serve
only what is needed
0 AVOID
Send Down the Drain,
Landfill, or Incinerate
with or without energy recovery
FIGURE ES-1. THE WASTED FOOD SCALE:
EPA'S NEW RANKING OF WASTED FOOD PATHWAYS
BASED ON LIFE CYCLE ASSESSMENT AND CIRCULARITY ASSESSMENT
Executive Summary
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In addition to the ranking provided, EPA draws the following conclusions:
Source reduction, donation and upcycling are the most environmentally preferable pathways
because they can displace additional food production. Source reduction demonstrates global
warming potential benefits an order of magnitude greater than all other pathways by reducing the amount
of additional food that must be produced. Source reduction can be achieved at any stage of the supply
chain, and source reduction options should be exhausted before other pathways are considered.
Donation and upcycling can also displace additional food production, and thus exhibit benefits closest to
those of source reduction. However, researchers estimate that up to 40 percent of donated food may be
wasted (Alexander and Smaje 2008), reducing benefits of donation relative to source reduction. In
addition, unlike source reduction, donation and upcycling require additional energy use (e.g., for
transportation, cold storage, or processing), reducing net environmental benefits since increased fossil
fuel energy use results in increased particulate matter, acidification, eutrophication, water consumption,
and human and eco-toxicity.
The benefits of pathways beyond source reduction, donation, and upcycling are small relative to
the environmental impacts of food production; thus, they can do little to offset the environmental
impacts of food production. For example, anaerobic digestion can produce more energy per unit of
wasted food than the other energy-producing pathways considered in this report (i.e., controlled
combustion and landfill), but anaerobic digestion can recover only around 20 percent of the energy that
was required to produce each unit of food. Also, unlike some other renewable energy sources (e.g., solar
or wind), combustion of biogas at anaerobic digesters generates criteria air pollutant emissions similar to
natural gas combustion.
Sewer/wastewater treatment (i.e., sending wasted food "down the drain") and landfilling stand out
for their sizeable methane emissions. Wasted food decays rapidly in anaerobic conditions. Sewer
transport allows for uncontrolled methane releases, and wasted food at landfills begins to decompose
prior to capping and placement of landfill gas capture systems. These emissions far exceed the benefits
of energy recovery technologies (i.e., anaerobic digestion at wastewater resource recovery facilities or
gas capture systems at landfills) or the carbon sequestration potential of landfills. Wastewater resource
recovery facilities with anaerobic digestion have lower global warming potential than those without, but
the difference is not big enough to affect the final ranking of the sewer/WWT pathway.
All wasted food pathways other than landfill and sewer/wastewater treatment demonstrate
beneficial or near neutral global warming potential. While all pathways (except source reduction) use
energy and release carbon dioxide, and some pathways release other greenhouse gases (methane and
nitrous oxide in composting and methane in anaerobic digestion), this is generally offset by the benefits of
avoided production of energy, food, animal feed and/or fertilizer, avoided fertilizer use, and/or carbon
sequestration.
Recycling wasted food into soil amendments offers opportunities to make long-term
improvements in soil structure and health and help regenerate ecosystems by recovering nitrogen
and carbon and returning them to the soil. The nutrient-rich outputs of composting, anaerobic
digestion, and sewer/wastewater treatment (i.e., compost, digestate or biosolids) can help build soil
organic matter, which decreases bulk density, increases porosity, water retention, and infiltration,
promotes nutrient cycling and retention, and stabilizes soil aggregates, reducing the risk of erosion.
These improvements are regenerative and can help to improve the resilience of agricultural systems in
the face of climate change. Synthetic fertilizers lack the organic matter content of these amendments and
cannot provide similar benefits, other than indirectly through promoting crop growth. In addition, the
nitrogen in wasted food can be used to provide nutrients to crops over the short or long-term in lieu of
synthetic fertilizers. These organic amendments require less energy to produce than synthetic fertilizers
and when applied result in less nitrogen loss through volatilization, leaching, or runoff than synthetic
fertilizers, reducing acidification, eutrophication, particulate matter emissions, and global warming
potential. However, nutrient-rich outputs from anaerobic digestion and sewer/wastewater treatment may
be disposed rather than beneficially used.
As the U.S. becomes less dependent on fossil fuels for energy, the environmental value of
producing energy from wasted food will decrease. The LCA results are driven largely by global
warming potential and energy demand, due to widely available data and, in the case of energy demand,
the effect of energy use on many of the other selected indicators. Energy use by pathways contributes to
Executive Summary
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more than half of the indicators assessed in the LCA chapter of this report, including energy demand,
acidification, eutrophication, particulate matter, and human and eco-toxicity performance. Thus, the
energy mix assumed (when calculating effect of energy use and/or avoided energy production) has a
substantial effect on the outcome of LCA studies. As the U.S. increases the use of lower-impact energy
sources in its portfolio, the environmental "cost" of energy use and the environmental "benefit" of avoided
energy production will both decrease. This would likely, for instance, lower the environmental
performance of controlled combustion and anaerobic digestion but improve the environmental
performance of composting. For example, if energy produced by anaerobic digestion was displacing wind
power, rather than fossil fuel-derived power, the pathway would be net positive (increase GHG
emissions), rather than net negative (reduce GHG emissions), for global warming potential (Slorach et al.
2019a).
Executive Summary
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CHAPTER 1
INTRODUCTION
Over one-third of the food produced in the United States is never eaten, wasting the resources used to
produce it and creating a myriad of environmental impacts. EPA estimates that the U.S. wastes 73 to 152
million metric tons (161 to 335 billion pounds) of food per year, or 223 to 468 kg (492 to 1,032 pounds) of
food per person per year, equal to approximately 35% of the U.S. food supply (U.S. EPA 2021c).
Recognizing the critical importance of reducing wasted food, in September 2015, the United States
announced the 2030 Food Loss and Waste Reduction Goal to halve per person wasted food at the retail
and consumer level and reduce on-farm losses by the year 2030 (U.S. EPA 2020d). This domestic goal is
aligned with the Sustainable Development Goal Target 12.3 of the 2030 Agenda for Sustainable
Development (UN General Assembly 2015). In addition, in 2020, the U.S. EPA set a National Recycling
Goal to increase the national recycling rate to 50% by 2030 (U.S. EPA 2022c). Currently, wasted food is
the single most common material landfilled and incinerated in the United States, comprising 24% and
22% of landfilled and combusted municipal solid waste (MSW) (U.S. EPA 2020a), respectively,
presenting opportunities for increased reuse and recycling.
This report is the second in a pair of EPA reports on the environmental impacts of wasted food. The first
report — From Farm to Kitchen: The Environmental Impacts of U.S. Food Waste (U.S. EPA 2021 c) —
described wasted food in the United States and the environmental footprint associated with producing,
processing, and distributing food that is ultimately wasted, including land use, water consumption,
pesticide and fertilizer use, and climate change. This second report investigates the environmental
impacts associated with the management of wasted food.
1.1 Purpose
The purpose of this report is to inform public- and private-sector policy- and decision-making about which
U.S. wasted food pathways to encourage, incentivize, or invest in based on environmental impact and
contributions toward a circular economy. The report considers eleven common pathways: source
reduction, donation, upcycling, animal feed, anaerobic digestion, composting, controlled combustion (i.e.,
incineration), land application, landfills, sewer/wastewater treatment, and unharvested/plowed in.
The report presents a new ranking of the wasted food pathways, from most to least environmentally
preferable. EPA's new ranking-called the Wasted Food Scale-replaces the agency's Food Recovery
Hierarchy developed in the 1990s.
1.2 Scope
The scope of this report is to document and compare the available literature on the environmental
impacts and benefits of wasted food pathways, beginning the moment food is wasted. The report also
considers each pathway's potential contribution to a circular economy, focusing on the environmental
aspects of circularity. The report does not address social and economic factors related to the pathways.
Where possible, the report evaluates the specific properties of wasted food and how they affect a
pathway's environmental performance.
Chapter 1. Introduction
1-1
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1.3 Definitions
In this report, the term "wasted food" is defined as food grown for human consumption that is not used for
its intended purpose and is managed in a variety of ways, such as donation to feed people, creation of
animal feed, composting, anaerobic digestion, or disposal in landfills or controlled combustion facilities
(U.S. EPA 2023a). Wasted food can be generated at any stage of the supply chain, from farm to
consumer. Examples include unharvested crops; by-products from food and beverage processing
facilities; unsold food from retail stores; or plate waste, uneaten prepared food, or kitchen trimmings from
restaurants, cafeterias, and households. Wasted food includes parts of food deemed edible and those
deemed inedible, such as shells, bones, pits, or peels. Food crops grown for other purposes, such as
biofuels or animal feed, is excluded from the definition.
The term "wasted food pathways" refers to all eleven pathways discussed in the report, including source
reduction, donation, upcycling, animal feed, anaerobic digestion, composting, controlled combustion, land
application, landfills, sewer/wastewater treatment, and unharvested/plowed in.
This report uses the definitions of each wasted food pathway provided in Table 1-1. These pathway
definitions are largely consistent with both the U.S. EPA 2019 Wasted Food Report (U.S. EPA 2023a)
and the Food Loss and Waste Protocol (Hanson et al. 2016), a collaborative effort among several
organizations1 that establishes guidelines for the accounting, reporting, uncertainty and tracking of wasted
food overtime. Key differences are that this report adds the source reduction and donation pathways and
excludes the bio-based materials/biochemical processing pathway since many of these technologies are
not yet at commercial scale. The upcycling pathway discussed in this report is a subset of the bio-based
materials/biochemical processing pathway in the Food Loss and Waste Protocol. Upcycling, as defined in
this report, produces food for human consumption, whereas bio-based materials/biochemical processing
may also produce non-consumable products such as cleaning products or chemicals. The terms
"controlled combustion" and "incineration" are used interchangeably in the report, as are the terms "down
the drain" and "sewer/wastewater treatment."
Additional pathways to manage wasted food exist but were excluded from the analysis in this report
because they are relatively novel and still being developed or data were unavailable. There is an
emerging group of processes that includes pyrolysis, torrefaction, gasification, and hydrothermal
liquefaction. Appendix E provides brief descriptions and summarizes available life cycle assessment data
on these processes. Appendix E also includes data on rendering, which is excluded from the main
analysis due to limited data availability. Rendering is the well-established process of cooking and
separating animal waste products and used cooking oil into purified fats and ground protein to produce
biofuels, animal feed ingredients, fertilizer, and commercial and industrial products (NARA 2019).
Chapter 1. Introduction
1-2
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TABLE 1-1. DEFINITIONS OF WASTED FOOD PATHWAYS
-0-
Source
Reduction
Reducing the generation of wasted food.
EE
Donation
Redistributing wasted food for human consumption.
Upcycling
Remaking wasted food into new food products for human consumption.
s
Anaerobic
Digestion
Breaking down wasted food via microorganisms in the absence of oxygen to
generate biogas and nutrient-rich matter (i.e., digestate or biosolids). May
occur at a stand-alone digester, an on-farm digester, or a digester at a water
resource recovery facility (WRRF)2. This pathway can include co-digestion,
which is the simultaneous anaerobic digestion of wasted food and other
organic material in one digester. In this pathway, wasted food is transported
to digester by vehicle or pipe. (Digestion of wasted food traveling to a
digester by sewer is classified as the sewer/wastewater treatment pathway.)
Animal Feed
Diverting wasted food originally intended for human consumption or
byproducts of food manufacturing (e.g., corn husks or fry oils) to animals,
either directly or after processing.
Composting
Breaking down wasted food via microorganisms in an oxygen-rich
environment to produce organic material (i.e., compost) that can be used as
a soil amendment.
Controlled
Combustion
Combustion (i.e., incineration) of wasted food in a controlled manner. This
report examines only controlled combustion that recovers energy.
Land
Application
Spreading, spraying, injecting, or incorporating wasted food from food
manufacturing onto or below the surface of the land to enhance soil health.
Landfill
Sending wasted food to an area of land or an excavated site that is
specifically designed and built to receive wastes. This report examines only
landfills that capture landfill gas to recover energy.
liB
Sewer/
Wastewater
Treatment
(WWT)
Sending wasted food down the drain and through the sewer (with or without
prior treatment) to WRRFs with or without anaerobic digestion. (Co-digestion
of wasted food delivered by truck or pipe directly to anaerobic digesters at
WRRFs is covered by the anaerobic digestion pathway.)
Un harvested/
Plowed In
Leaving crops that were ready for harvest in the field or tilling them into the
soil.
Chapter 1. Introduction
1-3
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1.4 Background
This section provides background on the prevalence of each of the wasted food pathways and existing
wasted food hierarchies, including the original 1990s EPA Food Recovery Hierarchy (U.S. EPA 2021 g).
Prevalence of Wasted Food Pathways in the United States
Figure 1-1 presents the prevalence of each wasted food pathway in the U.S. in 2019 (U.S. EPA 2023a).
The figure excludes the quantity of wasted food that is avoided through source reduction, the quantity
upcycled into new food products, and the quantity of on-farm wasted food that is unharvested and plowed
back into the soil.
Currently 60% of wasted food generated by retail, food service, and households is sent to landfill.
Controlled combustion (i.e., incineration) is the next most common pathway. In contrast, the predominant
wasted food pathway in the food manufacturing sector is anaerobic digestion, which receives 43% of the
sector's wasted food. Animal feed (34%) and land application (13%) are also common pathways for the
food and beverage manufacturing industry, with only two percent of the sector's wasted food destined for
landfills.
Donation
Anaerobic Digestion
Animal Feed
Composting
Controlled Combustion
Land Application
Landfill
Sewer / WWT
Other
0% 10% 20% 30% 40% 50% 60% 70%
¦ Food Manufacturing ¦ Retail and Foodservice ¦ Household
FIGURE 1-1. PERCENTAGE OF WASTED FOOD MANAGED BY EACH PATHWAY, BY SECTOR IN
WHICH THE WASTED FOOD IS GENERATED
Each sector sums to 100%.
Data Source: U.S. EPA (2023a)
Chapter 1. Introduction
1-4
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Wasted Food Hierarchies
Wasted food frameworks provide high-level guidance on social, economic, and environmental
preferences for managing wasted food. They have been developed in academic settings (e.g., Lombardi
and Costantino 2021) and by non-profit organizations and governments—for example, the United
Kingdom's Food and Drink Waste Hierarchy (DEFRA 2021) and the U.S. EPA Food Recovery Hierarchy
(Figure 1-2) (U.S. EPA 2021 g). The available frameworks differ in the number and priority order of wasted
food pathways, based upon the aim, perspective, and methodology of the researchers and/or
stakeholders (Moshtaghian et al. 2021).
The EPA Food Recovery Hierarchy is widely cited in the United States; however, it was established in the
1990s so might not reflect technological advances and changes in operational practices from recent
decades. Also, it does not consider all the wasted food pathways discussed in this report. This report
synthesizes the latest science on the life cycle environmental impacts and potential contributions to a
circular economy of eleven common pathways for managing wasted food in the U.S. and presents a new
ranking of pathways (called the Wasted Food Scale) on this basis The original EPA Food Recovery
Hierarchy is not, nor should the results of this report (the Wasted Food Scale) be interpreted as, a set of
strict criteria. Rather, the report aims to evaluate the many complex factors that influence the
environmental performance of the wasted food pathways and identify environmental tradeoffs,
recognizing that conclusions may vary based on location, climate, available infrastructure, or other
factors.
FIGURE 1-2. EPA'S PREVIOUS RANKING OF WASTED FOOD PATHWAYS
Source: U.S. EPA (202tg)
Chapter 1. Introduction
1-5
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1.5 Approach and Research Methods
This report synthesizes information from existing literature on wasted food. The systematic literature
review focused on three classes of studies:
Those employing a systems perspective or life cycle assessment (LCA) approach for quantifying
the collection-to-grave environmental impacts of wasted food pathways.
Those employing a circularity perspective for comparing the wasted food pathways.
Select studies addressing key data gaps not addressed by the identified studies.
The literature review protocol used to develop the findings in this report is provided in Appendix A.
Subsequent sections briefly introduce the concepts of LCA and circularity assessment and describe the
terminology used to communicate the magnitude of quantitative results in this report.
Life Cycle Assessment Approach
LCA is widely recognized for its ability to identify issues and assess tradeoffs across the value chain and
across environmental impacts (ISO 2006b). In LCA, information on the inputs and outputs of a defined
system or process are assessed to quantify the associated environmental impacts. The breadth of
coverage in LCA is intended to minimize the potential to shift environmental burdens between processes,
life cycle stages, or impact categories (ISO 2006a).
The management of wasted food requires collection, transport to a processing or treatment facility,
processing or treatment, distribution of beneficial products, and disposition of final waste outputs. Each of
these steps entails assumptions about system parameters, such as distances traveled, composition of
waste and efficiencies of processing.
The basis of comparison in an LCA—the functional unit—can vary widely across studies in a way that
sometimes hinders comparisons between them. For LCAs of wasted food pathways, though, the mass of
wasted food is typically chosen as the functional unit, and many authors additionally specify the quality
(e.g., moisture content and carbon:nitrogen ratio) and management duration (often one year), further
facilitating cross-study comparisons. Other modeling choices such as the system boundary, impact
allocation, and avoided product crediting can also affect the comparability of studies.
Global warming and eutrophication potential are the most studied environmental impacts in LCA of
wasted food pathways. Other impacts such as those related to soil health characteristics are
underdeveloped. In this literature review, we searched for quantitative information related to global
warming potential, energy demand, acidification, particulate matter formation, human toxicity, ecotoxicity,
eutrophication, water consumption, land occupation, and soil carbon sequestration / soil health.
Circularity Assessment Approach
This report also employs a circularity perspective to evaluate the wasted food pathways. Generally, the
goal of a circular economy is to decouple economic growth from resource extraction by capturing greater
value from existing products and materials. This contrasts with the traditional linear "take-make-use-
dispose" economy where waste is seen as something to "send away" or dispose of. The concept draws
from schools of thought such as industrial ecology and regenerative design (Geissdoerfer et al. 2017),
and many organizations and countries have adopted circularity principles over the last decade, including
the United Nations, the World Economic Forum, China, and the European Union (Bocken et al. 2016;
Geissdoerfer et al. 2017; Mancini and Raggi 2021).
In 2020, the U.S. enacted the Save Our Seas Act 2.0, directing EPA to develop circular economy
strategies for post-consumer materials management. While many definitions for a circular economy can
be found in the literature (Geissdoerfer et al. 2017; Kirchherr et al. 2017), in this report we rely primarily
on the definition from the Save Our Seas Act 2.0 - where a circular economy is one that "uses a systems-
focused approach and involves industrial processes and economic activities that:
1. are restorative or regenerative by design;
Chapter 1. Introduction
1-6
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2. enable resources used in such processes and activities to maintain their highest values for as
long as possible; and
3. aim for the elimination of waste through the superior design of materials, products, and systems
(including business models)" (U.S. Congress 2020).
Terminology
Table 1-2 summarizes the terminology used to make quantitative statements about processes or model
parameters driving environmental performance in the report. In this table, the net and gross impacts refer
to those modeled in a particular study for a particular pathway.
TABLE 1-2. QUANTITATIVE THRESHOLDS USED TO MAKE STATEMENT ABOUT THE MAGNITUDE
OF DRIVER CONTRIBUTIONS
Term
Threshold(s)
Impact/Gross
Impact
Refers to cumulative environmental impact excluding consideration of avoided
product benefits or other environmental credits (e.g., carbon sequestration).
Benefit
Refers to a net negative environmental impact including consideration of avoided
product benefits or other environmental credits.
Significant
Used only when cited authors make a claim of statistical significance in analyzing
environmental performance. Other terms and comparisons presented in this report
should not be interpreted as statistically significant.
Considerable
Contributing greater than 10% of net or gross impact.
The largest contributor to net or gross impact, even if less than 10%.
Sensitive
A result is sensitive to a particular parameter or practice when its presence or
absence leads to a 10% or greater change in impact.
A result is sensitive to a particular parameter when a change in that parameter's
value leads to a disproportionate change in the analysis result (such as when a
10% change in biogas yield leads to a 15% decrease in GWP).
Negligible
Contributing less than 2% of net or gross impact.
Minor
Contributing between 2% and <10% of net or gross impact.
Moderate
Contributing between 10% and 30% of net or gross impact.
Major
Contributing greater than 30% of net or gross impact.
Quality Assurance
In accordance with the project's Quality Assurance Project Plan (QAPP) entitled Quality Assurance
Project Plan for Environmental Impacts of Food Waste approved by EPA on November 2, 2022, this
report synthesizes literature on the environmental impacts and benefits of U.S. food waste pathways,
compares the environmental impacts and benefits of each pathway to one another under varying
conditions and using a suite of life cycle-based and circularity indicators, and identifies key knowledge
gaps where original scientific research may greatly improve our understanding of the issue and lead to
effective solutions. The literature search method employed complies with the QAPP and is described in
Appendix A. Appendix A also documents example queries and keyword searches used. The collected
data sources include peer-reviewed literature, government and NGO reports, national survey and
measurement information, and model simulations. The report authors evaluated the collected information
for completeness, accuracy, and reasonableness. In addition, the publication date, geographic coverage
Chapter 1. Introduction
1-7
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and funding source were assessed when reviewing data quality. All compiled literature information was
also reviewed by a report author who did not conduct the original data search. The literature review,
according to the QAPP, did not require specific criteria in terms of age of data, data source, geographic
coverage to determine whether the source was included or excluded. All data source attributes were
recorded in a transparent fashion and fully referenced. Extracted data values from literature are fully
documented in Appendix D. Specific attributes of each study such as the system boundary and
inclusion/exclusion of environmental credits were, however, documented to assess the comparability of
study results. The scope criteria for these inter-study comparisons are described in Section 3.4.
1.6 Report Overview
The report is organized in the following way:
Chapter 2 describes each wasted food pathway and identifies the key aspects of each pathway
that contribute to environmental impacts or benefits.
Chapter 3 compares the wasted food pathways through a review of Life Cycle Assessments.
Chapter 4 compares the wasted food pathways through a circularity assessment.
Chapter 5 discusses the report's findings and presents a new hierarchy of the wasted food
pathways.
Chapter 6 presents implications and priority research gaps.
Chapter 1. Introduction
1-8
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CHAPTER 2
WASTED FOOD PATHWAYS
This chapter describes each wasted food pathway and discusses key aspects of each pathway that
contribute to its environmental impacts and/or benefits, including its potential contributions to a circular
economy.
Each pathway section provides details on system "types," referring to the specific pathway technology
used, and process steps. For example, composting might use windrow or aerated static pile systems;
controlled combustion might involve grate furnaces, spreader stoker furnaces, or another technology.
While it is beyond the scope of this analysis to comprehensively discuss how different combinations of
these practices affect the environmental performance of wasted food pathways, the discussion in this
section looks to introduce these variables and to provide context for pursuing more detailed inquires
related to local wasted food management decisions and policy questions.
Given the breadth of environmental impact categories considered, the following discussion aims to strike
a balance between synthesis (looking for patterns across impact categories) and detail (recognizing that
individual impact categories may not fit broader patterns). The final section (Section 2.13) summarizes
topics that apply to multiple wasted food pathways, such as waste collection, transportation, and pathway
requirements regarding homogeneity and contamination of wasted food.
Many of the pathways described in this chapter do not exist exclusively to process wasted food. This
report focuses on the environmental performance of each pathway with respect to wasted food (e.g., the
focus is on the behavior of wasted food in a landfill, rather than on the performance of the landfill in
aggregate). At the same time, this report recognizes that the addition of wasted food may change the
behavior of the overall system (e.g., co-digestion of wasted food may improve the biogas yield of an
anaerobic digester).
System Diagram Introduction
Each wasted food pathway covered in this chapter includes a diagram of typical LCA system boundaries
for that process. Figure 2-1 provides an example of a generic system diagram. These diagrams illustrate
key processes that may be included in specific LCA studies. Not all listed processes in each system
diagram are necessary or relevant for inclusion in every LCA study.
Each diagram includes the following elements:
Wasted food and other possible waste inputs.
Key processes including wasted food collection, pre-treatment, operation of the main pathway
process (e.g., landfill or compost facility) and product processing and valorization. In some cases,
icons from Table 1-1, where wasted food pathways are defined, are used to identify the main
pathway process.
Additional inputs required, such as energy, fuel or chemicals.
Process outputs, which constitute the main beneficial products and co-products that result from
operation of a wasted food pathway for resource recovery. Process outputs include compost,
animal feed, digestate, biogas and landfill gas.
o Avoided products. Process outputs are often modeled within the LCA literature as avoiding
alternative products that would be utilized in the wider economy if wasted food resource
recovery was not pursued. An example of this would be avoiding the production and use of
chemical fertilizers in favor of an organic amendments such as compost, digestate or
biosolids. Wthin an LCA study, avoided products generate environmental benefits which are
also discussed as environmental credits.
Chapter 2. Wasted Food Pathways
2-1
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o Arrows are utilized to show the connection between processes and products and may include
transportation impacts when within the scope of individual studies. Orange arrows are used
to callout select input and output flows relevant to each pathway.
o Disposed waste. The trash can icon is used to show that contaminant flows present in wasted
food are sent to traditional waste disposal facilities such as landfills or controlled combustion.
It can also denote portion of wasted food ultimately being landfilled (e.g., up to 40 percent of
donations may be wasted rather than consumed).
o Outputs (e.g., effluent) and emissions. Sequestered carbon is also noted here.
"O
c
c7T
System Boundary
Key
May include transport
0
Waste
disposal
FIGURE 2-1. GENERIC SYSTEM DIAGRAM
Chapter 2. Wasted Food Pathways 2-2
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2.1 Source Reduction
Source reduction is fundamentally distinct from all the other wasted food pathways, as wasted food is not
generated. Source reduction decreases the generation of wasted food by preventing food from becoming
waste at any point in the food supply chain. Source reduction strategies can be sector-specific, such as
improved harvesting techniques, or applicable across all food sectors. Factors that result in the
generation of wasted food may be interlinked across the food supply chain. For example, produce might
go unharvested on a farm because it does not meet consumer standards for retail sale. Ensuring food
supply more closely meets demand requires coordination across the food supply chain. For instance,
farmers plant only what will be harvested and find secondary markets for surplus or "unmarketable"
produce, while food retailers manage inventory to avoid overstocking items that will not sell.
Improvements to packaging and storage can extend the edible life of food across the supply chain, from
cold storage to drying facilities, and packaging that extends shelf life to consumers optimally storing
produce. Enhancing the distribution of food products to decrease transit time, improving handling
techniques, optimizing product use, and monitoring for quality and safety are just a few of the many
actions that can reduce the generation of wasted food across the supply chain (ReFED 2023). Increasing
education and supporting behavioral change, especially at the consumer level, are also important steps
toward source reduction (Oregon DEQ 2017).
Minimizing waste offers the potential to reduce the amount of food production required to feed a
population (Sherwood 2020), thus reducing the environmental impacts associated with production,
including energy, water, and nutrient inputs, land use, and GHG emissions. Avoided impacts of food
production depend on the type of avoided food product and the management practices used to produce it.
Drawing on several resources, EPA estimates a wide spectrum of food production global warming
potential (GWP) impacts, ranging from 0.5 to 33 kg CCheq per kg of food produced and delivered to
consumers (U.S. EPA 2021c).
Chapter 2. Wasted Food Pathways 2-3
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2.2 Donation
The donation pathway rescues or redistributes wasted food for human consumption. Donated food is
"food that is donated to people via food banks or pantries, food distribution services, etc." (ReFED 2021).
Figure 2-2 diagrams the donation pathway. Wasted food intended for donation needs to be collected at
the source and transported to the point of distribution. For food donation, there is an extra logistical
challenge: food safety protocols must be maintained, and there are a variety of stakeholders in the
distribution system who must collaborate to ensure food safety. Collected food may require culling or
repackaging. The distribution phase of the donation pathway includes product storage and transportation
to individuals and wholesale or retail establishments.
System Boundary
Wasted
Food
Collection
• m
, o>
Sorting and
¦
Distribution
¦1
Human
Food
Storage
S
S
Consumption
HHH Production
Key
May include transport
0
Waste
disposal
FIGURE 2-2. DIAGRAM OF DONATION
Collection and Distribution
Food donation is not environmentally 'free': there are impacts associated with collection and distribution
of food. Gleaning is a specific form of food donation where unharvested or leftover crops are collected
directly from the farm field, often by volunteers or organizations in support of food pantries (D. Lee et al.
2017). Food to be rescued is often in dispersed locations (e.g., at retail stores) and therefore can require
a significant amount of effort to collect and distribute. When the use of personal vehicles is considered,
transportation may be an important contributor to overall environmental impacts, as trips may be
numerous or inefficient (Oregon DEQ 2019; Damiani et al. 2021). Despite this, transportation impacts are
often an order of magnitude smaller, if not more, than the avoided burden of producing food in the first
place (Schneider 2013). In addition, in some cases the impacts of transportation could reasonably be
excluded from the donation pathway (e.g., if a person drops off donated food at a collection site located in
a grocery store during a trip to buy groceries). Efficient storage and prevention of spoilage are important,
too, for this pathway. WRAP (2015) reports that increased use of appropriate packaging and increased
refrigeration result in a net GWP benefit, since less food is wasted.
Waste within the Donation Pathway
In addition, the donation pathway is not waste free, and a share of wasted food collected for donation will
ultimately be disposed of. Donated food may be wasted in several ways - food banks may not accept a
donation if it isn't a type of food they currently need or can use, food banks may accept a donation but be
unable to provide it to a customer before it spoils, or customers may take home donated food but not
consume it.
Estimates of this secondary waste vary, from 4% to 40%. A study by the Oregon Department of
Environmental Quality (Oregon DEQ 2019) assumes loss rates of about 7% at sorting and 7% again at
distribution, and model consumer waste (i.e., waste by donation recipients) at 7%, 14%, or 20%, while
ReFED reports that only 4.2% of donated food is not consumed (Corona et al. 2020). Some LCA studies
Chapter 2. Wasted Food Pathways
2-4
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assume all recovered food is consumed (e.g., Damiani et al. 2021), others acknowledge uncertainty on
this question and perform sensitivity analyses, and others use survey or other data to estimate loss rates.
Other studies roll all losses during the donation pathway into a single loss rate, such as 22% (Sundin et
al. 2022) or up to 40% (Alexander and Smaje 2008).
Avoided Food Production
The use of donated food by consumers results in an environmental benefit associated with avoiding
additional food production. Recovery and donation of low environmental impact foods (e.g., potatoes) has
a lower net environmental benefit than recovery and donation of high environmental impact foods (e.g.,
beef).3
In some cases, food donation does not cause less food to be produced - for example, when donated food
does not end up being eaten for various reasons, or when recipients of donated food could not have
otherwise purchased food. While it can be challenging to assess whether food donation actually affects
overall food production, donation can be credited with source reduction benefits, since donation is a
redistribution of food that would otherwise not be consumed (Heller 2019).
TABLE 2-1. DONATION: ENVIRONMENTAL DRIVERS
Sources of Environmental
Impact
Transportation emissions and associated impacts, which can vary
widely depending on the wasted food source and the type of
vehicle used.
Energy demand of cold storage.
Secondary wasted food.
Source of Environmental
Benefit
Avoided food production.
Option to Reduce Impact
Restrict collection and distribution efforts to food that is likely to be
consumed and prioritize collection and distribution of high
environmental impact foods.
Increase food refrigeration and preservation capacity of facilities
collecting food to reduce food loss prior to consumer.
Chapter 2. Wasted Food Pathways 2-5
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2.3 Upcycling
The upcycling pathway remakes wasted food into new food products for human consumption. Waste
streams suitable for upcycling are limited to commercially viable, pre-consumer streams. For example,
spent cereals from the beer brewing process may be used to create bread or crackers, and unsellable
produce and food processing byproducts (e.g., pits or peels) may be used to make beverages and
beverage mixes. Food banks may also upcycle wasted food (e.g., upcycling surplus milk donations into
cheese).
The use of upcycling as a means of reducing wasted food is a newer concept (Eriksson and Spangberg
2017), and there are limited data on the prevalence of this pathway. This review found only two studies
that comprehensively evaluated this pathway (Eriksson and Spangberg 2017; Eriksson et al. 2021);
therefore, a robust evaluation of its environmental impacts and benefits is not yet possible.
Figure 2-3 diagrams the upcycling wasted food management pathway.
System Boundary
Wasted
Food
8 <|
C/> ^
Collection
Processing
Distribution
Human
[PE Food
Consumption
HHH* Production
Key
Output I Process
May include transport
0
Waste
disposal
FIGURE 2-3. DIAGRAM OF UPCYCLING
Processing and Distribution
This pathway is unique among the wasted food pathways in that the recovered wasted food is processed,
distributed, and consumed as if it were "regular" food. As such, the environmental impacts of processing
and distributing this food are identical to those of the foods discussed in the Part 1 report (U.S. EPA
2021c)—with the production impacts removed. Impacts associated with upcycling vary widely depending
on the specific product being considered and can be consequential. In the analysis of Eriksson et al.
(2021), drying of broccoli leaves added about 0.12 kg C02eq per kg of harvested broccoli. When broccoli
powder was assumed to displace wheat flour, the avoided benefit of wheat production was not enough to
offset the GWP impact associated with drying the broccoli leaves, leading to a net impact. On the other
hand, this was not the case when upcycled broccoli displaced broccoli powder or slices, leading to a net
GWP benefit.
Avoided Food Production
The capture, processing, and human consumption of wasted food that would otherwise have been
disposed of is the defining aspect of the upcycling pathway. Several potential sources of reduced impact
or environmental benefit can be associated with the capture of wasted food for human consumption. First,
production impacts can be assumed to be zero, because as a former waste product, wasted food enters
the management pathway with no environmental burden. In reality, production impacts are not zero, but
these impacts are associated with (or allocated to) the non-wasted portion of the product. For example, in
the case of broccoli floret production, the impacts are associated with the production of the florets; they
Chapter 2. Wasted Food Pathways
2-6
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are not associated with the waste material (stems and leaves), which can be turned into a new product
such as broccoli leaf flour through upcycling.
In addition, by capturing otherwise wasted food, the upcycling pathway captures an environmental benefit
by avoiding additional food production. Researchers have applied this benefit in studying the conversion
of nonmarketable fruits and vegetables to chutney (Eriksson and Spangberg 2017)4 and the collection of
broccoli leaves for conversion to broccoli powder (Eriksson et al. 2021).5
However, the line between upcycling and traditional food production can be difficult to define and justify. If
wasted food gains value because it is upcycled, and producers come to rely on that input, then perhaps it
ceases to be wasted food, and it would be improper to ignore the environmental impacts associated with
its production orto consider avoided food production.6
Avoided Waste Management
Upcycling of wasted food that would otherwise have been disposed of can also result in environmental
benefits from avoided waste management. However, these credits should not be included in an
assessment of net impact/benefit when comparing impacts directly to those of alternative wasted food
pathways because this would lead to double counting. This analysis excludes these credits from our
comparative assessments. In addition, the upcycling pathway is not waste free, and a share of wasted
food collected for upcycling may ultimately be disposed of or managed through another pathway.
Estimates of waste from this pathway were not available in the literature.
TABLE 2-2. UPCYCLING: ENVIRONMENTAL DRIVERS
Source of Environmental
Benefit
Avoided food production and wasted food management.
Option to Reduce Impact
Displace conventional production of high-impact foods.
Chapter 2. Wasted Food Pathways 2-7
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2.4 Anaerobic Digestion
Anaerobic digestion (AD) is a process whereby organic materials are microbially degraded in an
anaerobic environment (one lacking oxygen), converting the feedstock into biogas and nutrient-rich
digestate (or biosolids). Wasted food can be digested alone or co-digested with other organic materials.
Digestion may occur at a stand-alone digester, an on-farm digester, or a water resource recovery facility
(WRRF) (U.S. EPA 2023b). When wasted food is co-digested with wastewater solids/sewage sludge at a
WRRF the end product is considered biosolids (rather than digestate) as it is subject to federal and state
regulations for biosolids management and use.7 AD of wasted food that is collected via the sanitary sewer
is not a part of this pathway; it is covered within the sewer/wastewater treatment pathway (see Figure
2-4). AD at WRRFs is included in this pathway only when additional wasted food (beyond that collected
by sewer) is source-separated (i.e., separated by the generator) and collected separately from other
waste streams and then delivered separately (i.e., not by sewer) to the AD unit.8
Vehicle
Collection
Wasted food
Sewer
AD Pathway
Stand-alone AD*
AD at WRRF
Sewer/
WWT Pathway
AD at WRRF
FIGURE 2-4. DIAGRAM DISTINGUISHING ANAEROBIC DIGESTION AND SEWER/WWT PATHWAYS
*Stand-alone facilities may exist only for food waste, or may co-treat other feedstocks (e.g., a digester for manure that
receives food waste).
Figure 2-5 diagrams the AD pathway. For this pathway, wasted food is usually collected by vehicle and is
subject to one or more pre-treatment steps that include removal of residual contamination, grinding,
mixing, and/or moisture adjustment to produce a clean and consistent feedstock for digestion. The
digestion process produces biogas (a mixture of gases including methane and carbon dioxide) and
digestate (or biosolids, if located at a WRRF).
The biogas can be used to produce one of several energy products, such as heat, electricity, or biofuel.9
These products can be used to offset other energy sources (e.g., heat from natural gas, electricity from
the grid, diesel). The digestate or biosolids may be post-treated and applied to land as fertilizer or
disposed of in a landfill or by controlled combustion.
In a voluntary survey of AD facilities processing wasted food in the U.S. (U.S. EPA 2023b), responding
AD facilities (stand-alone, WRRFs, and on-farm, n = 106) could choose multiple options from a list of solid
digestate or biosolids uses: dewatered and land applied; composted into a reusable/salable product,
landfilled, processed into animal bedding, dried into a reusable/salable product (e.g. fertilizer), land
applied as is with no dewatering or drying, incinerated, or other. According to the survey data, most AD
facilities (63%) use land application, with or without post-treatment (including composting), as one
management practice for digestate or biosolids. The majority of reviewed LCA studies assume that
digestate is land applied.
Chapter 2. Wasted Food Pathways
2-8
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p §ystem_ Boundary
Other
Organics
Vehicle
Collection
Key
Pre-treatment
(e.g., grinding,
mixing, sorting)
Packaging
and residues
Anaerobic Digestion
(wet or dry)
Output I Process
May include transport
FIGURE 2-5. DIAGRAM OF ANAEROBIC DIGESTION AND CO-DIGESTION OF WASTED FOOD
Anaerobic Digestion Technologies
As noted, there are three types of AD facilities that process wasted food: stand-alone digesters, and co-
digestion systems either at WRRFs or on farms (U.S. EPA 2023b). The terms "digestion" and "AD" are
used throughout this report to refer to all digester types and feedstock mixtures unless otherwise
specified. AD systems at WRRFs that do not receive additional wasted food delivered by vehicle are
addressed in the sewer/WWT pathway (Section 2.10).
Stand-alone digesters are often industry-dedicated, located at a food or beverage
manufacturing/processing facility and wholly dedicated to processing that facility's waste. In contrast,
multi-source stand-alone digesters (sometimes called "merchant" digesters) accept wasted food and other
feedstocks from sources across their region. On-farm digesters are primarily dedicated to digesting
manure and agricultural byproducts such as spent grain or crop residuals. Similarly, AD systems at
WRRFs are primarily dedicated to digesting wastewater solids. Co-digestion of wasted food with manure
or wastewater solids can increase biogas production, generate tipping fee revenue for farms or WRRFs,
and provide another option for wasted food management.
Across all digester types, among the AD facilities processing wasted food that responded to the EPA
survey, approximately 71% of digesters operate at mesophilic temperatures (U.S. EPA 2023b). Options
exist for AD technologies across all types of facilities (e.g., continuously stirred tank reactor, upflow
anaerobic sludge blanket), but the relative environmental performance of those different technologies is
beyond the scope of this report.
Chapter 2. Wasted Food Pathways
2-9
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TABLE 2-3. ANAEROBIC DIGESTION TECHNOLOGIES
Stand-alone
Primarily built to process wasted food. Includes multi-source wasted food
digesters and industry-dedicated digesters.
£
O
'-5
re
On-farm
Primarily used for manure management. These digesters can co-digest
wasted food.
o
_i
WRRF
Primarily used to digest wastewater solids. Wasted food can be
transported to the AD unit by truck and co-digested with the wastewater
solids (which may include wasted food transported down the drain
through the sewer to the WRRF).
0)
Q.
Wet
Digesters processing feedstocks with <15% solids.
>
H
Dry
Digesters processing feedstocks with >15% solids.
£
3
•*->
5
Mesophilic
Digester operation at 30-40°C.
0)
Q.
E
0)
H
Thermophilic
Digester operation at 50-60°C.
tfl
Digestate
From stand alone or on-farm digesters. Residue from digestion process
which can be separated and treated through drying, de-watering, or
composting which can be used in animal bedding, land application, other
products, or landfilled or incinerated.
D
Q.
•*->
D
o
Biosolids
Solid discharge of sewer/WWT treated through various technologies,
including AD. An output of AD systems at WRRFs which can be
incinerated, landfilled, or land applied with or without post-treatment.
Energy
Electricity, heat, and biofuels which can be used for heating and
powering the facility or sold as electricity or fuel.
Prevalence
The EPA survey of U.S. AD facilities processing wasted food indicates that stand-alone digesters
processed over 90% (by weight) of digested wasted food in 2019. This is largely due to stand-alone
digesters processing large amounts of beverage processing waste (e.g., from breweries), which is heavier
per unit of volume than other types of wasted food such as residential food scraps. If beverage
processing waste is excluded, then AD at WRRFs processed the majority of digested wasted food in
2019—about 80% according to EPA survey responses.
There are approximately 70 stand-alone digesters in the U.S. (U.S. EPA 2023b), and there are roughly
16,000 WRRFs in the U.S., of which about 1,270 have AD (American Biogas Council 2018). Of those AD
facilities at WRRFs, around 10% are estimated to co-digest wasted food (U.S. EPA 2023b). EPA's
AgSTAR program identifies 317 farms in the U.S. with anaerobic digesters, approximately 25% of which
are estimated to co-digest wasted food (U.S. EPA 2023b). The American Biogas Council tracks biogas
production in the U.S. and identifies over 2,200 biogas projects, including 250 on-farm digesters, 1269
WRRFs with AD, and 66 stand-alone digesters (all other biogas projects are at landfills). Discrepancies in
the numbers and types of AD facilities are likely due to differences in tracking and/or data year.
Processing wasted food can add value to an AD system at a farm or WRRF by synergistically increasing
biogas production.
Chapter 2. Wasted Food Pathways
2-10
-------
Anaerobic Digester Operation
Studies assessing the environmental impact of wasted food management via AD point to operation of the
digestion reactor itself as one of the primary sources of impact (Woon et al. 2016; Edwards et al. 2017;
Khoshnevisan et al. 2018; Pace et al. 2018). Studies consistently identify energy demand and fugitive
emissions from digester operations as impacts; depending on their scope, some studies also include
chemical use or infrastructure materials. Of the studies clearly reporting electricity demand for digester
operation, three-quarters report values within the range of 10-58 kWh per metric ton of waste processed.
Additional heat energy may be required to achieve optimal operating temperatures, but few studies
document a specific quantity, sometimes simply noting that residual heat from biogas combustion is
used.10 Among studies that do report heat demand, the values are in most cases at least double the AD
electricity demand. Within the reviewed studies, estimates of fugitive methane losses typically vary
between 1% and 5% of produced biogas, with some studies assuming negligible losses. However, recent
estimates of methane emissions from centralized WRRFs are 1.9 times higher than previous estimates
(Moore et al. 2023), suggesting that existing studies may systematically underestimate methane from
WRRFs. These recent comprehensive studies (Moore et al. 2023; Song et al. 2023) do not address the
contribution of wasted food to WRRF emissions, so further study is needed.
Studies report the potential of wasted food co-digestion to synergistically enhance biogas production at
WRRFs, with the potential to increase net energy production (Xu et al. 2015; Edwards et al. 2018).11 A
case study of a Massachusetts WRRF demonstrated positive environmental outcomes when excess AD
capacity is utilized for wasted food co-digestion (Morelli et al. 2020).12 Usack et al. (2018) report that co-
digestion of wasted food with animal manure leads to a reduction in total life cycle emissions of AD when
compared to digestion of manure only.
Biogas Production
Biogas produced by AD has numerous uses and destinations in the United States. These include
producing heat, electricity, and mechanical power for the AD facility, producing electricity for the grid,
compression to vehicle fuels to be sold or used by the facility, and producing renewable natural gas. In
the EPA survey of AD facilities processing wasted food, 95% of stand-alone, 67% of on-farm, and 86% of
WRRF digesters reported using some or all the produced biogas onsite. When given a list of biogas uses
with the option to choose multiple uses, the most commonly selected biogas use was combined heat and
power (CHP) (56% of responding facilities), followed by fuel for boilers to heat digesters (38%) or to heat
other parts of the facility (38%) (U.S. EPA 2023). EPA (2023b) reports that 32% of stand-alone digesters,
50% of farms, and 67% of WRRFs use some of or all the biogas produced for CHP.
Avoided energy benefits associated with the use of AD biogas to displace electricity, heat, and biofuels
were consistently found to reduce environmental burdens and, in many instances, led to net
environmental benefits. Across a subset of reviewed LCA studies for which electricity recovery numbers
were reported, gross electricity production per metric ton of wasted food processed is between 100 and
420 kWh (see Appendix Table B-1). While a considerable quantity of heat can be recovered in addition to
the electricity produced, many studies exclude an environmental credit for recovered heat as it is used to
operate the digester and no uses are available for excess heat in the studied scenario. Avoided energy
benefits are realized on the basis of net energy production (i.e., production minus the energy demand
required to operate the digester and associated processes).
Environmental benefits of avoided energy production depend on several factors, including the quantity of
energy produced per unit of wasted food, the specific fuel mix that is being displaced, and whether
avoided burden credits are or can be reasonably applied for the full quantity of energy recovered.13
Several authors observed major reductions in GWP impact as a result of biogas production and utilization
(Xu et al. 2015; Woon et al. 2016; Khoshnevisan et al. 2018). Individual studies also reported other major
reductions in environmental impact, including reductions in acidification potential (Edwards et al. 2017)
and ecotoxicity and human toxicity (Gonzalez et al. 2020). These findings are supported by the analysis
of Chiu and Lo (2018), who looked at key parameters for wasted food treatment uncertainty assessment
and concluded that biogas production rate, biogas methane content, methane lower heating value,
energy recovery efficiency, and energy demand for biogas upgrading all have a statistically significant
effect on environmental performance.14
Chapter 2. Wasted Food Pathways
2-11
-------
Murphy and Power (2006) found that, in instances where a market for CHP heat is available, use of
biogas for that purpose is economically preferable to use as transportation fuel. If a market for CHP is not
present, then upgrading biogas to transportation fuel is a better option. Other analyses have shown that
upgrading biogas to renewable natural gas (RNG) for use as a transportation fuel leads to higher
environmental impacts, compared with the same AD system paired with CHP (Gonzalez et al. 2020) .
This finding is due to the energy demand of the additional processing steps required for the RNG
upgrade. Utilization of surplus heat (beyond that required for process operation) can offset other forms of
heat production such as from kerosene (Murphy and Power 2006), fuel oil (Gonzalez et al. 2020), natural
gas or propane. Novel uses of surplus thermal energy are also possible such as use in greenhouses (Lin
et al. 2018), allowing for extension of growing season.
Digestate Post-treatment and Use or Disposal
In the U.S., the liquid fraction of digestate (i.e., liquid separated through dewatering) is commonly applied
to agricultural lands as fertilizer (Alexander 2012; U.S. EPA 2023b). This is particularly true for on-farm
AD facilities which mainly co-digest wasted food with animal manure. Other uses of the liquid fraction
include recirculating digestate through the digester or sending the digestate to wastewater treatment. In
the case of AD at WRRFs, the dewatering liquid is recirculated through the wastewater treatment process
and eventually released as effluent. The solid fraction of digestate or biosolids can be unprocessed,
composted, de-watered, or dried and common uses vary by facility type. In some cases, digestate is not
separated into liquid and solid fractions and is land applied as a slurry. In the EPA survey of AD facilities
processing wasted food, most often on-farm digesters report creating animal bedding, WRRFs with AD
report de-watering and land applying, and stand-alone digestors report composting to create a salable
product (Alexander 2012; U.S. EPA 2023b). Of the three AD facility types, WRRFs with AD are most likely
to landfill solid digestate or biosolids - 33% report landfilling some or all biosolids (U.S. EPA 2023b).
When digestate is applied as fertilizer for crop production or used as animal bedding, a renewable
resource is recovered and used. However, depending on contamination and other limiting factors such as
access to agricultural land and the seasonality of land application, digestate might be treated as a waste
and disposed of (e.g., at landfill or by controlled combustion).
Wthout post-treatment, digestate or biosolids can be disposed of in a landfill, burned in a controlled
combustion facility,15 or applied to agricultural lands in accordance with state and federal regulations. The
means by which compost, digestate, or biosolids is transported from generation to application is
important. As shown in Brown and Beecher (2019), transport of Class B biosolids in trucks may have
lower transport emissions than retail compost transport in personal vehicles. However, these transport
emissions are likely minor relative to other stages of wasted food generation, handling, and processing.
Composting is the most common post-treatment process for digestate considered within the reviewed
literature. Benefits of the composting process include waste stabilization, vector control, and volume
reduction. Most studies evaluating post-treatment composting consider subsequent land application of
generated compost. A study looking at both composting with land application and controlled combustion
of digestate found that AD with composting led to better average environmental performance in terms of
GWP and particulate matter formation, whereas AD plus controlled combustion led to reduced human
toxicity impact as a result of fewer heavy metals being released to the environment (Mayer et al. 2020).
Mayer et al. report that the GWP of AD with composting is driven by GHG emissions during post-
treatment steps (composting and land application) but is partially offset when the digestate is used as a
substitute for synthetic fertilizer.
Land application of (uncomposted) digestate or biosolids produces environmental benefits and impacts in
the form of energy use for transportation and application and emissions from application. Depending on
post-treatment methods, digestate and biosolids maybe have a high moisture content relative to other
materials (e.g., compost; Grigatti et al. 2020) and therefore a higher weight, making them more energy-
intensive to transport. The method and timing of digestate land application affect the magnitude of
emissions to air and water, as do weather conditions following application (Tiwary et al. 2015). Most
nutrient emissions occur during digestate storage and land application (Usack et al. 2018).16 The
literature presents concerns regarding long-term soil contamination from digestate or biosolids land
application, particularly in cases where wasted food is co-digested with wastewater solids or other
potentially contaminated waste streams. Chemical contaminants include heavy metals, pharmaceuticals
and emerging contaminants, such as per- and polyfluoroalkyl substances (PFAS). Note that some metals,
such as zinc and copper, are micronutrients. Cycling of these metals can be beneficial, provided they do
Chapter 2. Wasted Food Pathways
2-12
-------
not accumulate above toxicity thresholds. Physical and chemical contamination of digestate and biosolids
can limit their potential for beneficial use. See the discussion on soil health in Section 4.5 for more
information.
The potential benefits of digestate land application include avoided fertilizer or peat production, carbon
sequestration, and positive contributions to soil health (see Section 4.6). Findings related to the
environmental benefits of avoided fertilizer production vary widely across the reviewed studies. Several
authors found negligible or minor environmental benefits (Righi et al. 2013; Khoshnevisan et al. 2018).
Gonzalez et al. (2020) identified avoided production of nitrogen fertilizer as the primary source of
environmental benefit in acidification, eutrophication, and GWP impact categories. LCA studies typically
assume a nitrogen substitution ratio with synthetic fertilizer of between 20% and 50% of nitrogen content.
Phosphorus and potassium content is usually assumed to have a similar plant availability to the
phosphorus and potassium in mined or synthetic fertilizer products, and therefore a substitution ratio of
1:1 is common.
As an alternative to or in addition to fertilizer replacement, a small number of LCA studies look at using
digestate or compost to substitute the use of peat growing media. These studies found that the GWP
benefits of avoiding peat use were similar to Morris et al. (2017) or greater than avoided fertilizer benefits
(Levis and Barlaz 2011).
Substituting digestate or compost for synthetic fertilizers and/or peat growing media is
assessed inconsistently within the LCA literature. Because of the differences in nutrient (N, P, K)
plant availability and organic carbon stability and content, digestate and compost may be assigned
different substitution ratios when displacing synthetic fertilizer and/or peat growing media.
N substitution:
Similar substitution ratios are assumed for compost and digestate: 20-50% of synthetic N fertilizer.
Digestate typically has higher readily available N content (N that can be immediately used by plants),
suggesting it may more often fall in the higher end of that range. Compost has lower readily available
N content, providing a slower release of N over time, and more often falling in the lower end of that
range.
P and K substitution:
For compost and digestate, the same ratio is assumed: 1:1.
(Levis and Barlaz 2011; Yoshida et al. 2012; Stehouwer et al. 2022; Morris et al. 2017)
A portion of the carbon in land-applied digestate is often sequestered beyond 100 years, reducing net
GHG emissions according to many GHG accounting frameworks. A review of LCAs of wasted food
management identified a range of assumptions that between 10 and 27 kg of CCheq is sequestered per
metric ton of wasted food digested and land applied (Bernstad Saraiva Schott et al. 2016). For more
information regarding the range of carbon sequestration benefits identified see Appendix B-1-1. Adding
carbon to soils has benefits beyond sequestration, including improving soil structure, increasing water
holding capacity and benefitting soil microbes. But there are no standardized metrics in reviewed LCAs
for soil health beyond carbon sequestration; as such, these benefits are not included in the comparisons
in Sections 3.4 and 3.5. See Section 3.6 for more information on soil health.
Chapter 2. Wasted Food Pathways 2-13
-------
TABLE 2-4. ANAEROBIC DIGESTION: ENVIRONMENTAL DRIVERS
Sources of Environmental
Impact
Energy demand of digester operation.
Emission of methane associated with biogas leakage during digestion
or processing.
Emission of CAPs from biogas combustion.
Additional energy and chemical demand for biogas cleaning and
upgrading.
Energy use for post-treatment of digestate or biosolids.
Sources of Environmental
Benefit
Reduced production and use of fossil energy due to biogas energy
recovery.
Displacement of conventional fertilizer and peat production if land
application of digestate.
Long-term carbon sequestration and contributions to soil health if land
application of digestate (Section 4.6).
Options to Reduce Impact
Optimize biogas production.
Monitor and minimize fugitive emissions of biogas.
Use enhanced emission controls on electrical orCHP engines
Avoid landfilling digestate; when digestate is land applied, follow best
management practices regarding digestate application rate, timing,
and method to minimize potential damage from agricultural emissions
or soil contamination (UNH Extension 2017).
Other Considerations
Digestion technology: Energy demand and methane yield vary
depending on digestortype, number of stages, and temperature
conditions.17
Net energy production is dependent on energy conversion efficiency
and energy demand of AD and post-treatment processes.
Chapter 2. Wasted Food Pathways 2-14
-------
2.5 Animal Feed
The animal feed pathway diverts wasted food that was originally intended for human consumption or is a
byproduct of human food production (e.g., fry oil, corn husks) to animals, either directly after harvesting or
after processing. This pathway does not include animals grazing unharvested fields, which is included
under the unharvested/plowed in pathway. Use as animal feed is more common for the U.S. food
manufacturing sector than for the retail, food service, and household sector (U.S. EPA 2023a). The
nutritive and economic value of animal feed derived from wasted food ranges by feedstock and
processing techniques. Wasted food is nutrient rich. When compared with traditional maize used for
animal feed, wasted food can have double the crude protein content. Incorporation of wasted food in
animal feed can also reduce feed costs and tipping fees for the waste producer (Dou et al. 2018).
Figure 2-6 diagrams the animal feed wasted food management pathway. Wasted food pre-treatment and
processing steps include de-packaging, sorting, grinding, and drying; sterilization may be accomplished
through heating wasted food or through preservation in a silo, which does not require energy inputs.
Finished feed must be free from contamination to ensure animal health (Redlingshofer et al. 2020). Using
wasted food for animal feed can displace the need for primary agricultural production of animal feed from
sources such as soy meal, barley, and corn (Tufvesson et al. 2013; Albizzati et al. 2021b).
System Boundary
Wasted
food
^ I 1 1
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Q. CD
O *<
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CD
3
CO
CQ
Pre-treatment
(e.g., grinding,
mixing, sorting)
Feed
Processing
Packaging and residues
Key
J Waste
disposal
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FIGURE 2-6. DIAGRAM OF WASTED FOOD CONVERSION TO ANIMAL FEED
Animal Feed Production Processes
The pathway results in a broad range of potential products from less processed to very highly processed.
Wet animal feed is a minimally processed high-moisture feed product, sometimes requiring heat
treatment. Dry feed requires further processing to dewater, dry, and pelletize wasted food (Dou et al.
2018).
The environmental impacts of animal feed production depend on the type of wasted food and the type of
animal feed being produced. For the same wasted food feedstock, wet animal feed typically undergoes
less processing and has reduced energy demand relative to dry animal feed. The high moisture content
of wasted food requires increased energy for dry feed dehydration (Salemdeeb et al. 2017). Therefore,
dry feed should ideally be produced from wasted food with lower moisture content. Nine of the 14
reviewed animal feed LCA study scenarios pertain to the production of dry animal feed. There were two
studies that modeled production of both wet and dry feed from municipal wasted food (Salemdeeb et al.
2017; Albizzati et al. 2021a).
Most of the reviewed studies modeled the direct production of animal feed; animal feed can also be
indirectly produced by bioconversion (i.e., feeding wasted food to insects, which are then further
processed to produce animal feed). Bioconversion presents opportunities and challenges relative to direct
feed production, as the intermediate organisms may be able to accept wasted food with a wider range of
moisture, contaminants, and pathogens, but require energy and other inputs.
Chapter 2. Wasted Food Pathways
2-15
-------
TABLE 2-5. ANIMAL FEED TECHNOLOGIES
Dry Feed
Dry matter content of about 78% (Salemdeeb et al. 2017).
tfl
0)
Wet Feed
Dry matter content of about 30% (Salemdeeb et al. 2017; Albizzati et al.
2021b).
Q.
>
H
Protein
Concentrated
A dried animal feed with high protein content, similar to soybean meal (46-
50% dry matter protein content) (Corona et al. 2018).
Other
Examples include bakery meal and black soldier fly larvae meal (black
soldier flies are fed with wasted food).
Avoided Conventional Feed Production
Environmental credits associated with avoiding conventional animal feed production are a source of
considerable environmental benefit for this wasted food pathway and often lead to favorable
environmental performance when compared to other pathways.1819 A published literature review (Dou et
al. 2018) concluded that wasted food is rich in major nutrients for feeding livestock and, when treated
properly, is a safe and sustainable alternative to growing dedicated feed crops. Potential benefits include
pollution avoidance and reduced use of land and other resources to grow feed crops, according to the
review.
Hygiene Considerations
Because raw wasted food intended for animal consumption may contain active disease organisms,
several methods of wasted food sterilization have been developed to prevent disease transmission (Dou
et al. 2018). Heat treatment of wasted food in animal feed is widely enforced globally (Dou et al. 2018).
Regulations have been developed in the U.S. to assure safety of animal feed. The majority of these
regulations pertain only to wasted food that contains animal products. The FDA's Ruminant Feed Ban
Rule (U.S. FDA 2022) prohibits feeding cows, sheep, goats, and other ruminants any feed containing
mammalian protein. For pigs, under USDA's Swine Health Protection Act (SHPA) (USDA 2020), raw
wasted food intended for swine consumption must be sterilized via heat treatment (100°C for at least 30
minutes) if it contains or has had contact with meat, poultry, or fish. One study in Spain found that heat
treatment at 65°C for 20 minutes adequately reduces E. coli, Salmonella, and S. aureus to levels that are
considered safe for animal consumption (Garcia et al. 2005). Another study in China reported that
hydrothermal treatment at 110°C for 60 minutes eliminates S. aureus, total conforms, and total aerobic
bacteria (Jin et al. 2012). State governments may choose to enforce more stringent laws for sterilization
procedures and go beyond the minimum standards set by U.S. regulation. Additional regulations vary by
U.S. state, with 15 states placing more strict guidelines on animal feed than are dictated by federal
regulation. Most of this regulation specifically addresses feeding swine. Nine states have a prohibition on
feeding animal or vegetable waste to swine (Leib et al. 2016).
Chapter 2. Wasted Food Pathways 2-16
-------
TABLE 2-6. ANIMAL FEED: ENVIRONMENTAL DRIVERS
Sources of
Environmental
Impact
Energy demand (e.g., wasted food dehydration for dry feed).
Transportation (wet feed has higher transportation impacts due to its higher
mass).
Source of
Environmental
Benefit
Avoided feed production impacts.
Options to Reduce
Impact
Select animal feeds with lower energy demand, such as locally produced wet
feed.
Select pre-treatment methods with the lowest energy and chemical demand.
Other
Considerations
Feed type dictates production method and associated impact.
To justify the avoided feed benefit, the wasted food-based feed must be a suitable
substitute for the type of animal feed being displaced.
Chapter 2. Wasted Food Pathways 2-17
-------
2.6 Composting
The composting pathway breaks down wasted food, and co-treated wastes, via microorganisms in an
oxygen-rich (aerobic) environment to produce a stable, organic material that can be land applied.
Successful composting requires a balance of nitrogen-rich and carbon-rich ingredients, adequate but not
excessive moisture content, and oxygen flow to achieve desired pile temperatures and aerobic conditions
(U.S. EPA 2021 h). Compost systems are deployed at a wide variety of scales from small home compost
piles to large, highly managed industrial facilities.
Figure 2-7 diagrams the composting management pathway. Wasted food is generally one of multiple
feedstocks in a composting operation due to its high nitrogen content. Most composting facilities that
accept wasted food require that wasted food be source-separated and separately collected. Some also
require pre-treatment (sorting and screening) to remove potential contaminants, along with grinding and
blending of feedstocks.20 The composting process requires some form of turning or aeration to maintain
optimal aerobic conditions to reduce the release of airborne and waterborne pollutants (Zhao et al. 2022;
Peng et al. 2023). Post-treatment of mature compost may include screening, sorting, grinding, chipping,
blending, and/or bagging. The output of the composting process is a nutrient-rich, carbon-rich substrate
that can be used as a soil amendment and/or mulch, depending on the carbon-to-nitrogen ratio and the
desired end use.
System Boundary
Wasted
food
Collection
Pre-treatment
(e.g., screening,
sorting)
Compost
(Windrow,
Aerated static, etc.)
Post-treatment
(e.g., screening,
sorting, grinding)
Packaging
and residues
J2.
-
Compost
Fertilizer
o
i
r&r-
\ \g/. •.
• • • * •
Peat
Land Application
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FIGURE 2-7. DIAGRAM OF WASTED FOOD COMPOSTING,
INCLUDING A PROMINENT CO-WASTE SUCH AS MUNICIPAL GREEN WASTE
Composting Technologies
There are three common methods of composting in the United States: windrow, aerated static pile, and
bioreactor. Many reviewed LCA studies use the term in-vessel to describe bioreactor composting
systems.
Chapter 2. Wasted Food Pathways
2-18
-------
TABLE 2-7. COMPOSTING TECHNOLOGIES
Turned Windrow
Processing of compost in long piles using mechanical turning for
aeration.
Types
Aerated Static Pile (ASP)
Processing of compost in large piles using active and passive
aeration. Passive aeration systems are not likely to be used at large
scales due to the time and land area requirements (Piatt et al.
2014).
Bioreactor
Processing of compost in an enclosed vessel, often under
controlled conditions. Bioreactor systems come in multiple
configurations including tunnel, agitated-channel, and rotary drum
(Piatt et al. 2014). They may be heated to speed decomposition.
Outputs
Compost
Nutrient- and carbon-rich soil amendment which can be applied in
agriculture, transportation projects, green infrastructure, and other
land applications.
Prevalence and Value
There are between roughly 3,000-5,000 composting facilities in the United States, based upon estimates
from the EPA Excess Food Opportunities Map (3,887) and BioCycle (4,713) (Goldstein 2017; U.S. EPA
2023d). According to the Excess Food Opportunities Map, at least 16% of U.S. composting facilities
accept wasted food (U.S. EPA 2023d). This map includes mostly municipal, commercial, and industrial
composting facilities; community composters, institutions and farms with on-site composting operations
also accept food scraps.
Of these 3,000-5,000 composting systems, more than 50% are windrow (Piatt et al. 2014). The U.S.
Composting Council and Environmental Research and Education Foundation (EREF) recently surveyed
composting facilities. Of 293 early respondents, over 50% use windrows, ~28% use ASP, ~22% use
static piles, and less than 10% use in-vessel (EREF 2023).
The economic value of compost is highly affected by the compost quality, end use, and market (Rynk et
al. 2022). On average, compost sells for about $10 U.S. dollars (USD) per cubic yard (Goldstein 2020). A
survey of nearly 100 U.S. composts made in part from wasted food demonstrated mean content of 1.5%
total nitrogen, 0.37% phosphorus and 0.90% potassium, with mean carbon:nitrogen (C:N) ratio of 15.8
(Stehouwer et al. 2022). In a study of approximately 150 compost manufacturers in the U.S., the U.S.
Composting Council estimated the economic value of nutrients recycled through composting to be about
$96.6 million USD for nitrogen, phosphorus, and potassium and $20.5 million USD for carbon (U.S.
Composting Council 2021). Contamination, either physical or chemical, may also affect compost value.
The effort to remove these contaminants can increase the difficulty of processing the wasted food, and
not removing them can negatively impact compost quality. Contamination levels in finished compost may
also be regulated. California, for example, limits physical contamination to less than 0.5% by weight for
physical contaminants larger than 4 millimeters (State of California 2016a). Metal contamination is also
regulated with species such as copper and zinc being limited (State of California 2016b).
Chapter 2. Wasted Food Pathways 2-19
-------
Aeration Energy
Composting requires the use of energy for aeration and equipment operation. Among methods commonly
used for wasted food composting, windrow composting tends to have the lowest energy demand. In
windrow compost systems, diesel fuel tends to be the dominant energy source and the amount of energy
consumption depends on turning frequency and the type of equipment used. Actively aerated compost
methods, such as an ASP or bioreactor, have modest but relatively higher energy demand that tends to
come in the form of electricity consumption (Levis and Barlaz 2011). Bioreactor composting systems,
especially those operated at above-ambient
temperatures, can have considerably greater energy
requirements (Lin et al. 2018). Ultimately, energy
demands depend on many factors, such as the scale of
the operation, the composting method, the equipment
used, and feedstock characteristics. Renewable energy
may be used by composters and heat recovery may
save energy as well.
Looking Forward: Composting
Process Emissions
To limit GHGs, California has set target
reductions for short-lived climate pollutants
(SLCP), like methane and VOC's, that can
be generated from organic waste
degradation, including composting.3 SLCP
will have to be lowered by 75% by 2025.
SLCP can vary greatly between sites, with
reported values in California compost
facilities ranging from 1-10 lb VOC/wet ton
waste (not entirely food waste).b Biofilters
can help reduce those emissions by
90%+.c
Process Emissions
Process GHG emissions are associated with bacterial
activity in the compost pile (CARB 2017). Large
amounts of carbon, nitrogen, phosphorus, and other
lower-concentration chemical compounds are cycled
through composting processes. In compost piles, most
feedstock carbon is either retained in the final product or
released to the atmosphere as carbon dioxide. A small
fraction of carbon is released as methane.21 22 Similarly,
feedstock nitrogen is either retained in the finished
compost or liberated as ammonia, nitrous oxide, nitrate,
or other nitrogen-containing compounds. Emissions
released during composting can be a major or minor
source of environmental impact depending on impact
category and the facilities' operating practices or the modeling assumptions used in LCA studies.23 For
instance, VOC production can be reduced by maintaining composting conditions that are aerobic, with
high C:N ratios and moderate moisture (Delgado-Rodriguez et al. 2011). Optimizing emission reductions
across all potential pollutants is challenging, and further research is needed to evaluate tradeoffs.24 Pile
structure, chemical composition, moisture content, and other factors can affect composting speed, quality,
and environmental performance (Lin et al. 2018).
a(California 2023)
b(CARB 2015)
c(Brown et al. 2020) article
Compost Land Application
Application of compost to soil can result in numerous benefits to agricultural systems and residential or
commercial landscapes. Benefits of compost use include carbon sequestration25 and avoided production
and use of chemical fertilizer or peat.26 Impacts associated with compost land application typically include
transportation, energy use during spreading/incorporation, and emissions to air and water. Organic forms
of nitrogen present in compost typically take longer to become plant-available than the nutrients present
in synthetic fertilizers. To reflect this fact, LCA studies typically assume a nitrogen substitution ratio with
synthetic fertilizer of between 20% and 50%. Phosphorus and potassium content in wasted food compost
has similar plant availability to the phosphorus and potassium in mined or synthetic fertilizer products, and
therefore a substitution ratio of 1:1 is common. Nitrogen substitution ratios reflect short-term plant
availability and may therefore underestimate avoided fertilizer benefit over longer time scales. Rates of
mineralization and the timing of nutrient plant availability depend on the matrix in which nutrients are
delivered, the method of application, and other site-specific factors. While LCA is therefore not an
appropriate tool to model nutrient and soil dynamics, the aggregate LCA results of this review can
nevertheless help to identify trends.
While compost typically has less readily available nitrogen than digestate or biosolids, its total N content
varies based on feedstock and composting conditions. Literature reviewed shows compost can contain
similar (WRAP 2016; Grigatti et al. 2020) or greater (Stehouwer et al. 2022) amounts of total nitrogen
compared to digestate, though often contains less total N than biosolids (Brown et al. 2011). Compost
Chapter 2. Wasted Food Pathways
2-20
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releases this nitrogen slowly over time, supporting long-term soil fertility. See Section 4.6 for a more
detailed discussion of benefits.
While most LCA studies include environmental credits for avoided fertilizer production, the magnitude of
this benefit varies. Morris et al. (2017) identifies a moderate to major reduction in gross GWP impact as a
result of avoided fertilizer production and include an additional benefit for displacing peat soil amendment.
Only a small number of studies look at using digestate or compost to substitute the use of peat growing
media. Compost is assumed to displace peat use 1:1 on a volume basis (Levis and Barlaz 2011). These
studies found that the GWP benefits of avoiding peat use were similar to (Morris et al. 2017) or greater
than avoided fertilizer benefits (Levis and Barlaz 2011). A study of mixed wasted food and green waste
composting found major reductions in gross impact for GWP, particulate matter formation, and
carcinogenic effects, with minor reductions in most other impact categories attributable to avoided
fertilizer production (Keng et al. 2020). However, a study that examined composting the organic fraction
of MSW(OFMSW) found minor to negligible environmental benefit associated with avoided fertilizer
production for most impact categories, including GWP (Righi et al. 2013). The median GWP benefit from
avoided fertilizer production, across the eight studies for which a disaggregated fertilizer credit could be
identified, is -28 kg CCheq per metric ton of composted wasted food.
While all the reviewed LCA studies assume that an avoided fertilizer production credit is applied for
compost produced from wasted food, in real world circumstances, these benefits will only be realized
when the use of compost reduces fertilizer production and use. A survey of commercial composters in the
U.S. by the U.S. Composting Council reports the following uses of the total compost produced:
landscaping (40%), followed by agriculture, topsoil blenders, parks and roads, and general public (10%
each), retail (9%), commercial horticulture (5%), golf courses and nurseries (2% each), and mine
reclamation (1%); plus 1% as landfill cover (U.S. Composting Council 2021). In total the survey finds that
100% of compost is land applied to soil (Gilbert 2023), with 1% of that applied as landfill cover which may
be considered disposal. However, it is unlikely that compost displaces synthetic fertilizer in all these
applications. In some cases, it may be used only as a mulch or clean fill. This survey does not include on-
farm composting where compost is used by the farm and thus likely underestimates agricultural use of
compost.
The benefits of compost as a soil amendment include the potential for increased carbon sequestration,
reduced erosion, increased water retention, and increased soil microbial activity. Beyond use in
agriculture and landscaping, compost's water retention and filtration properties are beneficial in
stormwater management and green infrastructure. Compost use has proven benefits for urban soils and
in remediation. For example, composting can reduce the bioavailability of heavy metals by forming stable
chemical bonds and trapping metals in soil aggregates (Goss et al. 2013; Urra et al. 2019; O'Connor et al.
2021; Thakali and MacRae 2021). All these benefits are largely due to compost being rich in carbon and
highly effective at building soil organic matter, which is crucial for soil health and function. Compost can
also suppress some plant diseases and pests and increase crop yields.
Approximately half of reviewed studies on composting and compost use include a carbon sequestration
benefit for the GWP impact category. If the soil is in agricultural use, additional benefits can include
reduced fertilizer and herbicide use, reduced water consumption, and increased crop yield (CARB 2017).
While the benefits of compost noted here are well accepted, the LCAs reviewed contained no
standardized metric for soil health improvement other than carbon sequestration. As such, these benefits
are not included in the comparison of LCA studies in Sections 3.4 and 3.5. However, organic matter
content is a widely accepted and well-studied metric for overall soil health and is considered elsewhere in
this report, including in Section 3.6 and in Chapter 4.
Net Energy Demand
Unlike some other wasted food pathways considered in this review, composting does not typically directly
capture energy embedded in wasted food and put it to beneficial use. Composting operations have a net
positive energy demand and are negatively influenced when using energy sources with high
environmental impacts (Yoshida et al. 2012). A summary of emerging science by Lin et al. (2018) shows
the potential to capture low-grade heat energy from compost piles for greenhouse and water heating
applications. The authors concluded that if viable systems are developed for capturing a share of
composting's waste heat, the energy balance and environmental performance of compost systems could
be improved.
Chapter 2. Wasted Food Pathways
2-21
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TABLE 2-8. COMPOSTING: ENVIRONMENTAL DRIVERS
Sources of Environmental
Impact
Energy demand of aeration.27
Air emissions during composting. The primary pollutants of
concern include ammonia, nitrous oxide (N2O), methane, and
other volatile organic compounds (VOCs).28 Emissions can vary
widely depending on composting method, management, and
environmental conditions.29
Sources of Environmental
Benefit
Long-term carbon sequestration and contributions to soil health
from land application of compost (Section 4.6).
Displacement of peat and conventional fertilizer production due
to land application of compost.30
Options to Reduce Impact
Manage or select systems for energy efficiency.
• Windrow systems have low energy demand.
• Optimize aeration in actively aerated systems.
Install bio-filters, which oxidize methane to carbon dioxide and
reduce odors. Use of Gore covers also controls odors and
reduces emissions of ammonia and volatile organics (Levis and
Barlaz 2011).
Follow best management practices regarding compost
application rate, timing, and method to minimize potential
damage from agricultural emissions.31
Other Considerations
Successful composting requires maintaining aerobic conditions,
appropriate moisture content, and a favorable carbon to nitrogen
ratio (C:N ratio) (Risse and Faucette 2017).32
Composting's lack of energy recovery limits environmental
benefit relative to pathways with energy recovery.
Chapter 2. Wasted Food Pathways 2-22
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2.7 Controlled Combustion
This pathway encompasses combustion of wasted food in a controlled manner (i.e., incineration) to
reduce solid waste volumes and recover energy. This report examines only controlled combustion with
energy recovery. By the early 1990s, the majority of controlled combustion facilities in the U.S. had
installed emissions control devices and were recovering energy (U.S. EPA 2023c). Emission control
devices equip modern MSW incinerators to remove particulates, acid gas, and often dioxin and mercury
(National Research Council 2000).
Figure 2-8 diagrams the controlled combustion management pathway and the potential for co-firing with
other wastes. Wasted food is typically combusted in a mixture with other solid wastes due to its high
moisture content (Trabold and Babbitt 2018). Waste feedstocks that include wasted food, with a high
moisture content and low heating value, may require supplemental fuel or pre-drying for complete
combustion. Even if a system does not have an explicit pre-drying step, the energy demand of drying
would be reflected in lower net energy production.
Controlled combustion byproducts (i.e., fly and bottom ash) may require post-treatment (e.g., drying and
heavy metal removal) before beneficial use or disposal. Both kinds of ash are typically landfilled in the
United States (U.S. EPA 2023c).
System Boundary
Wasted
food
Q- D!1
¦5 (D
"
c/>
o"
3
O
o
3
cr
Key
Output
Process
May include transport
O
Waste
disposal
FIGURE 2-8. DIAGRAM OF CONTROLLED COMBUSTION OF WASTED FOOD
(AS PART OF MSW) WITH ENERGY RECOVERY
Controlled Combustion Technologies
There are several furnace types used for controlled combustion. Waterfall furnaces that burn commingled
waste account for the majority of U.S. municipal waste-to-energy design capacity, 71% (Giraud et al.
2021). A further 19% of U.S. design capacity is fueled using refuse derived fuel (RDF) and combusted in
a spreader stoker furnace. Mass burn rotary waterfall and mass burn refractory wall furnaces are the next
most common furnace types in the United States, accounting for about 8% of municipal waste-to-energy
design capacity (Giraud et al. 2021).
Chapter 2. Wasted Food Pathways
2-23
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TABLE 2-9. CONTROLLED COMBUSTION TECHNOLOGIES
Waterfall
Furnace
Combustion of commingled waste (mass burn) on a slanted grate.
M
tfl
0)
Q.
>,
Spreader
Stoker
Combustion of RDF on a traveling grate.
Other
Includes many other furnace types, grate (or alternate) designs, and
operating conditions in the three broad categories of mass burn, RDF, and
modular.
tfl
•*->
3
Fly Ash
Residues from air pollution control which contain hazardous substances
can be landfilled, used as mine backfill, or treated and used in
construction.
Q.
•*->
D
o
Bottom Ash
Can be landfilled or used as structural fill, road base, and asphalt.
Energy
Electricity, heat, and biofuels which can be used for heating and powering
the facility or sold as electricity or fuel.
Prevalence and Value
Controlled combustion of MSW, including wasted food, without energy recovery is not common practice in
the U.S. (U.S. EPA 2022b; U.S. EPA 2023c). In the U.S. there are 75 facilities which burn MSW and
recover energy (U.S. EPA 2023c). On average they produce 550 kWh and generate $20 to $30 USD per
short ton of MSW. Production of energy from wasted food is lower than some other materials in MSW due
in part to its high moisture content. Across a subset of reviewed studies for which electricity recovery
numbers were reported, gross electricity production per metric ton of wasted food combusted is between
138 and 564 kWh.
Combustion residuals from the incineration of wasted food or MSW containing wasted food include
bottom ash and fly ash (and metals that are recovered earlier in the process). Total ash generated ranges
from 15% to 25% by weight and from 5% to 15% by volume of the MSW processed (U.S. EPA 2023c).
Bottom ash accounts for 80-90% of total residuals by weight. Bottom ash is typically landfilled in the U.S.
but can be used as an aggregate in construction materials (Funari et al. 2017; Cho et al. 2020; U.S. EPA
2023c); however, wasted food's contribution to bottom ash is negligible (Slorach et al. 2019a). Fly ash is
hazardous due to high levels of heavy metals and dioxins. In the U.S., fly ash is landfilled in facilities
designed to prevent leaching into groundwater (U.S. EPA 2023c).
Wasted Food as Feedstock
Efficient incinerator operation depends on the availability of a consistent, suitable waste stream. Two of
the most basic suitability criteria include an adequate heating value (energy content) and reasonable
moisture content (Trabold and Babbitt 2018). Higher energy content, ideally above 20 MJ/kg total solids,
and lower moisture content favor improved incinerator performance (Clavreul et al. 2012). An analysis of
fresh fruits and vegetables, which have a high water content, found that of bananas, tomatoes, apples,
oranges, and peppers, only controlled combustion of bananas (lowest moisture) led to a net reduction in
GWP emissions (Eriksson and Spangberg 2017), demonstrating wasted food's water content make it a
poor feedstock for controlled combustion. Research indicates that removal of wasted food from MSW
streams before incineration can reduce energy use, increase calorific value, and improve efficiency of
controlled combustion per unit of weight (Song et al. 2013; He et al. 2014; Rajagopal et al. 2014; Erses
Yay 2015; Lee et al. 2020).
Due to the difficulties that excess moisture poses for wasted food combustion, a pre-drying step is often
employed. Benavente et al. (2017) find that rotary drying of olive mill waste prior to controlled combustion
is a primary contributor to environmental impact in all categories studied, particularly GWP. Another study
finds that pre-drying the OFMSW prior to controlled combustion deteriorates environmental performance
and is not preferable (Mayer et al. 2020).
Chapter 2. Wasted Food Pathways
2-24
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Process Emissions
Incinerators generate large volumes of flue gas process emissions that have the potential to contribute
considerably to the environmental impact of wasted food. The human health impacts of direct emissions
from incinerator stacks have been of concern for many years. Many emissions are related to other MSW
components with which wasted food has been commingled; however, wasted food itself is a source of
dioxins at parts-per-billion levels in flue gases, with variation in dioxin levels attributable to wasted food
type (Katami et al. 2004).34 Reviewed LCA studies vary in terms of the hazardous air pollutants that are
included in their inventory data. Albizzati et al. (2021 b), for example, assesses toxicity related impact
categories and includes dioxin, hydrogen fluoride, nickel and polycyclic aromatic hydrocarbons in their air
emissions inventory. Mayer et al. (2020) also assesses toxicity impact categories and includes
pentachlorophenol, nickel, mercury, lead, dioxins, cyanide, cobalt, chromium, arsenic and antimony in
their air emissions inventory. In the latter study, the functional unit is based on the organic fraction of
MSW.
Prior to the 1970s, flue gases were often discharged directly. Technological emission controls have been
used and improved since that time, beginning with electrostatic precipitation (a technology for removing
particulates) and now including flue gas condensation, dioxin/mercury filters, and selective catalytic
reduction (Damgaard et al. 2010). These emission controls have often had a positive effect on incinerator
emissions. For example, dioxin emissions from combustion of MSW (all MSW, not only wasted food) in
the U.S. decreased approximately 90% from 1980 to 2000 (Makarichi et al. 2018).
Several literature reviews have looked for evidence of environmental or human health effects of controlled
combustion emissions (National Research Council 2000; World Health Organization 2007; de Titto and
Savino 2019). The following conclusions appear widespread: (1) incinerator technology has improved
considerably in recent decades, (2) there are known connections between incinerator emissions
(particulates, mercury, and dioxin) and potential environmental and human health impacts, (3) limited and
generally inadequate studies have identified clear risks to human and environmental health, (4) evidence
is unable to definitively support an estimate of the presence or magnitude of risk, and (5) further research
should be pursued to expand epidemiological and risk assessment studies using new techniques such as
biomarker studies. The development of more definitive conclusions regarding the environmental and
human health impacts of waste incinerator operations has been obstructed by difficulties in assessing
impacts related to long-term pollutant exposure at low concentrations, poor understanding and variability
in the nature and timing of incinerator emissions, widely present confounding factors in the environment
(other air emissions, smoking, dietary variation, etc.) and the need for multi-site studies, to name a few.
As such, there are ongoing concerns about controlled combustion's impact on communities and the
environment (Hooks et al. 2020). Given that 79% of all MSW incinerators in the U.S. are located within
low-income communities or communities of color (Baptista and Perovich 2019), emissions from controlled
combustion should be considered from technical and environmental justice perspectives.
Energy Recovery
Controlled combustion's primary source of environmental benefit is associated with the recovery of
electricity and heat. Recovered energy displaces grid electricity with a biogenic energy source. Avoided
energy benefits are calculated based on net energy production (i.e., production minus energy demand
required to operate the incinerator and associated processes). Across a subset of reviewed LCA studies
for which electricity recovery numbers were reported, gross electricity production per metric ton of wasted
food processed is between 138 and 564 kWh (see Appendix Table B-1).
One study analyzed controlled combustion of wasted food both with and without avoided energy benefits.
The study found that controlled combustion of mixed waste stream (80% wasted food) resulted in gross
environmental impacts when avoided energy benefits were not considered. In the study, packaging
materials were not separated from wasted food prior to controlled combustion. When recovered heat and
electricity were considered, the analysis showed a greater than 130% reduction in environmental impact
(i.e., a net benefit) in 9 out of 10 impact categories (Mondello et al. 2017). GWP was the only impact
category to not produce a net benefit, due in part to combustion of packaging materials. GWP realized a
40% reduction in gross impact when avoided energy benefits were included (Mondello et al. 2017).
Another study analyzed controlled combustion of mixed municipal organic wastes (wasted food, yard trim,
and biosolids) and demonstrated a moderate to major reduction in all considered impact categories when
Chapter 2. Wasted Food Pathways
2-25
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energy recovery was included, with GWP and acidification seeing the greatest reduction in impact (Lee et
al. 2020).
TABLE 2-10. CONTROLLED COMBUSTION: ENVIRONMENTAL DRIVERS
Sources of Environmental
Impact
Energy demand of drying and controlled combustion.
Generation of flue gas containing air pollutants such as particulate
matter and dioxins, which are a function of feedstock and emission
controls.
Landfilling of ash results in long-term emissions.
Sources of Environmental
Benefit
Reduced production and use of fossil energy due to energy
recovery.
Recovery of fly ash or bottom ash for beneficial use (an avoided
product benefit) (Albizzati et al. 2021b).
Options to Reduce Impact
Select or design waste streams with suitable moisture and energy
content (e.g., bakery waste).
Ensure air pollution controls meet standards to limit emissions.
Chapter 2. Wasted Food Pathways 2-26
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2.8 Land Application
Land application of wasted food, as discussed in this report, refers to the direct application of wasted food
to agricultural land without composting, digestion, or treatment via other wasted food pathways discussed
in this report. This practice predominantly involves transporting the byproducts of industrial food
manufacturing activities, such as sugar beet residues or acid whey from yogurt and cheese production,
back to agricultural land for direct integration into soil. It does not include application of wasted food
generated further downstream by retail, food service or households.
Figure 2-9 diagrams the land application management pathway. A review of the literature found limited
information pertaining to the modeling of environmental impacts and benefits of this wasted food pathway,
and scope distinctions between originally edible (e.g., sugar beet pulp) versus inedible (e.g., olive pits)
wasted food are not commonly drawn or discussed.
System Boundary
Wasted i
food 1
-i C~
§
(/>
"O
o
a.
Key
Output
Process
m H
3 3
tn ^
m r~
i. 3
W Q.
<2. >
o g
§.
o
13
May include transport
FIGURE 2-9. DIAGRAM OF DIRECT LAND APPLICATION OF WASTED FOOD
Application of raw wasted food to soil can result in numerous benefits to agricultural systems. Benefits
include carbon sequestration and avoided production of chemical fertilizer (Klinglmair and Thomsen
2020). Additional soil health benefits may be provided by land application of wasted food and are
discussed in Sections 4.4 and 4.6. But these benefits are not commonly assessed in the literature and are
not included in comparisons in Sections 3.4 and 3.5. Benefits related to reduced water demand from the
application of high moisture content food wastes are also not commonly considered in literature and are
not included in any comparisons. Impacts associated with wasted food that is applied to the land typically
include transportation, energy use during spreading/incorporation, and emissions to air and water.
An LCA study comparing AD and land application pathways for olive mill wastes found that transportation
of waste materials to the field was a major contributor to energy demand and a minor contributor to GWP
for land application (Batuecas et al. 2019).35 The study did not consider any environmental
impacts/benefits associated with land application of produced digestate or wasted food. Alternatively, the
ReFED model applies the same assumptions for composting and land application, except infrastructure
requirements, including assessment of fugitive emissions of methane and nitrous oxide during
decomposition and a carbon sequestration benefit (Corona et al. 2020).
The benefits of land application of wasted food will depend on the wasted food feedstock. In the LCA
literature, there were a limited number of wasted food types assessed. A study looking at land application
of oily wasted food found that multi-year applications led to 9% to 19% increases in soil carbon and that
corn yields were maintained for fall applications where sufficient nitrogen was available (Rashid and
Voroney 2004).36 Subsequent research by the same authors examined experimental data and found
justification for an avoided fertilizer benefit due to land application of oily wasted food (Rashid et al.
2010).37 Land application of fats, oils, and grease (FOG) wastes has also been shown to improve
Chapter 2. Wasted Food Pathways
2-27
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microbial activity, thereby increasing aggregate stability and mitigating many forms of soil erosion (Plante
and Voroney 1998). The results of a laboratory study evaluating decomposition of potato waste in soil
found rapid decomposition leading to fertility benefits (Smith 1986).
TABLE 2-11. LAND APPLICATION: ENVIRONMENTAL DRIVERS
Sources of Environmental
Benefit
Long-term carbon sequestration, increased fertility, and contributions to
soil health resulting from land application of raw wasted food (Section
4.6).38
Displacement of conventional fertilizer production due to land
application of raw wasted food.
Options to Reduce Impact
Follow best management practices regarding wasted food application
rate, timing, and method to minimize potential damage from agricultural
emissions.39,40
Minimize transportation distance.
Chapter 2. Wasted Food Pathways 2-28
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2.9 Landfill
The landfill pathway sends wasted food to an area of land or an excavated site specifically designed and
built to receive and contain household and other nonhazardous waste. Wasted food most often enters a
landfill commingled with other MSW. This report examines only landfills that capture landfill gas (LFG)
and recover energy.
According to EPA's Landfill Methane Outreach Program database, which tracks key data on MSW
landfills, LFG collection systems, and energy recovery projects, there were at least 1,279 active landfills
accepting waste in the United States in 2021. These numbers do not comprehensively include small
facilities that do not meet reporting thresholds. Of the active facilities, 734 have landfill gas collection
systems and accepted nearly 90% of landfilled waste in 2020. Nearly 65% of all collected LFG was
utilized for energy recovery, which accounts for over 65% of landfilled waste in the U.S. being sent to a
facility with an active energy recovery project (U.S. EPA 2022a).
Capturing biogas from waste decomposition creates a renewable energy resource. However, wasted food
decay rates vary by composition but are generally faster than other MSW constituents, such as wood or
textiles (U.S. EPA 2020b). As such, gas from wasted food decomposition might not be captured and can
contribute significantly to fugitive methane emissions (Ishangulyyev et al. 2019). Fugitive emissions from
wasted food decomposition occur based on wasted food decomposition rate and the timing of installation
of gas capture technology and capping.
Figure 2-10 diagrams the landfill management pathway. Following collection, MSW is deposited in the
landfill and covered regularly with cover material then capped permanently once the design capacity of a
landfill section is reached. After a brief period of aerobic activity, the interior environment of the landfill
becomes anaerobic, and organic materials will partially degrade to LFG, a mixture of methane, carbon
dioxide, and other gases.41 The volume and timing of LFG production can vary widely, depending on the
type(s) of waste disposed of, the local climate, and management practices. As methane is produced, it
diffuses out of the landfill, both before and after the cover layer is in place. Once the cover layer is
installed, some fraction of methane is oxidized to carbon dioxide in the cover layer. The loss of methane
is undesirable environmentally, as methane is a potent GHG with a GWP approximately 28 times that of
carbon dioxide over a 100-year period (IPCC 2013). Therefore, many landfills capture a portion of LFG
and either flare it, reducing fugitive methane emissions, or use it to recover energy, reducing methane
emissions and producing a beneficial product. When the landfill is capped, a portion of the LFG is
collected. Methane that is not captured as LFG either is oxidized in the cover layer or escapes (U. Lee et
al. 2017). Collection and treatment of landfill leachate (liquid effluent from landfills) is necessary.
System Boundary
Collection
Landfill and
m
Landfill Gas
¦
Capping
m
(LFG) Capture
S
Energy
LFG Utilization
Venting
Energy
Recovery
H
C
Q)
"O
T3
o
cB
m
Q.
d
r~
O
cn
O
3
(/>
3
w
-------
Prevalence and Value
In the U.S. in 2022, 51% of all landfills that could potentially recover biogas, based on landfill type and
age), were doing so. Of these facilities, 68% recovered gas for electricity generation, 15% produced
renewable natural gas, and 17% used gas directly, meaning biogas was used onsite or piped to nearby
businesses for fueling boilers or other uses (U.S. EPA 2021 d).
Average estimates suggest that one million tons of MSW can produce either 0.78 MW of electricity or 216
MMBtu of heat per day (Environmental and Energy Study Institute 2013). The value of electricity and heat
will vary by market rates but range between 0.025 and 0.07 USD/kWh and 4 and 8 USD per MMBtu
(Environmental and Energy Study Institute 2013). As noted above, much of the energy derives from
organic wastes other than wasted food.
Fugitive Emissions
Studies consistently find that fugitive landfill methane emissions account for the majority of GWP impact
for the landfill pathway (Yoshida et al. 2012; Edwards et al. 2018). The quantity of fugitive emissions
depends on waste type, landfill type, climate, and the type, installation timing, and efficiency of LFG
capture and recovery systems. The rate of material degradation in a typical landfill model is defined by a
decay factor, which is based on material type and assumed landfill climate factors such as temperature
and precipitation.42 Wasted food, grass clippings, and leaves degrade quickly relative to other organics
such as paper, wood and mixed MSW (U.S. EPA 2020b). Faster rates of waste degradation can lead to
fugitive methane emissions that occur prior to a landfill being covered for gas recovery, increasing GWP
impact (Ishangulyyev et al. 2019). Because of these relative decay rates, the proportional contribution of
wasted food to fugitive emissions is higher than to captured gas, relative to many other organic wastes.
Material decay rates affect the timing but not the magnitude of LFG production. The magnitude of
methane and carbon dioxide produced in a landfill is determined by the carbon content of landfilled
material and the share of landfilled carbon that decomposes overtime. Degradable carbon content is
typically defined as the quantity of degradable organic carbon (DOC) in the material. An additional factor,
DOCf, is used to specify the fraction of DOC that will decompose under landfill conditions. DOCf values
vary across waste types and likely within the broad category of wasted food (U. Lee et al. 2017).43
Wasted food degradability and DOCf are variables that can have a moderate to major effect on net GWP
impact results. Both are subject to large uncertainties (U. Lee et al. 2017).
The portion of uncollected LFG methane that is not oxidized to carbon dioxide in landfill cover will be lost
as fugitive emissions. Methane oxidation rates vary depending on the stage of LFG capping, ranging from
a 10% oxidation rate for landfills without gas collection or final cover, to 20% for landfills with gas
collection before final cover, and up to 35% for landfills after final cover installation. Yoshida et al. (2012)
found that a 5% increase in LFG methane oxidation, as it filters through the landfill cover, can lead to a
25% decrease in total GHG emissions. A sensitivity analysis conducted by Lee et al. (2017) showed an
18% reduction in GHG emissions when the default oxidation factor of 10% was updated to 36%, which
was the mean value identified in a review of methane oxidation factors.44 The details of LFG modeling
have evolved considerably in recent decades, especially for highly degradable wastes such as wasted
food, with evidence that past modeling approaches may underestimate landfill methane production and
fugitive emissions (Wang et al. 2013; Duren et al. 2019).45
Recent work has shown discrepancies between self-reported landfill methane emissions and remotely
sensed emissions (Duren et al. 2019), with some landfills severely underestimating emissions. Further
work is needed to determine if these underestimated values are based on an incomplete understanding of
landfill processes, or whether parameter estimates have been inaccurate, whether there is systematic
underreporting bias, or if some other issue is at play.
Landfill Gas Collection
In modern landfills, the majority of LFG is collected and combusted to recover energy or flared. U.S.
EPA's WARM model estimates that the average LFG collection efficiency at U.S. landfills is 64.8% and
can be closer to 80% at sites that follow stricter California regulations (U.S. EPA 2020). Most analyses
assume that recovered energy displaces traditional sources of energy, producing an environmental
benefit. One analysis looking at four impact categories (GWP, eutrophication, acidification, and
ecotoxicity) concluded that acidification realized the greatest benefit when LFG was collected and used to
Chapter 2. Wasted Food Pathways
2-30
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produce heat and electricity. Gross acidification impact was reduced by approximately 25% due to
avoided energy credits (Lee et al. 2020). Minor to moderate reductions in impact were realized for the
other three impact categories, with eutrophication seeing the smallest relative reduction in impact.
Carbon Sequestration
Non-degradable carbon in wasted food and the fraction of DOC that does not decompose are
sequestered in the landfill, reducing the net GWP of wasted food landfilling. Wasted food has a lower
carbon storage potential relative to other degradable waste types due to its lack of lignin content
(Ishangulyyev et al. 2019). U.S. EPA's WARM model estimates that approximately 16% of the initial
carbon content in wasted food will be stored in the landfill, which is considerably lower than the carbon
storage potentials for other organic materials commonly landfilled (e.g., grass: 53%; branches: 77%;
leaves: 85%) (U.S. EPA 2020).46 The LCA models reviewed for this report applied a variety of modeling
assumptions regarding carbon sequestration. The differences largely depend on assumptions about
material degradability and environmental conditions in the receiving landfill.47 A separate review of LCA
studies examining GHG emissions during wasted food management found nine LCA studies (of 19) that
considered carbon sequestration. These studies assumed that between 67 and 168 kg C02eq are
sequestered per ton of wasted food landfilled (Bernstad Saraiva Schott et al. 2016).
Landfill Leachate
If no liner is in place, or if a liner fails, then escaped leachate can lead to groundwater contamination.
Leachate due specifically to wasted food might be of concern due to nutrient content (contributing to
eutrophication), but it is difficult to attribute future landfill leachate composition to specific inputs to the
landfill. Most studies assume that landfill leachate is collected and either treated onsite or conveyed to a
local WRRF. The quantity of leachate produced is a function of incoming waste moisture, rainfall,
evapotranspiration, and permeability of the landfill, which will change overtime (Edwards et al. 2017). For
impact categories where wastewater treatment efficiently removes the contributing pollutants, the share of
wastewater that goes untreated can dominate the impact (Edwards et al. 2017).48
TABLE 2-12. LANDFILL: ENVIRONMENTAL DRIVERS
Sources of
Environmental Impact
Fugitive methane emissions.
Pollution of ground water or surface water from untreated landfill
leachate.
Source of Environmental
Benefit
Reduced production and use of fossil energy due to LFG energy
recovery.
Options to Reduce
Impact
Maximize gas capture efficiency to reduce gas leakage.49
Use optimized cover materials to increase methane oxidation, which may
reduce fugitive emissions (Lee et al. 2017).
When possible, maximize energy capture from LFG; otherwise maximize
LFG flaring. The loss of produced energy credits associated with LFG
flaring results in higher GWP impacts for the landfill pathway.
Other Considerations
(U.S. EPA 2020a)
LFG leakage from a landfill depends on gas capture efficiency,
environmental conditions, and waste characteristics.
The decomposable carbon content in wasted food impacts the magnitude
of methane and carbon dioxide produced in landfills.
Methane oxidation rates vary depending on the stage of LFG capping.
Chapter 2. Wasted Food Pathways
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2.10 Sewer/Wastewater Treatment
The sewer/WWT pathway (also commonly referred to as "down the drain") represents wasted food that is
sent down sink drains with or without prior treatment such as grinding in a garbage disposer. Wasted food
sent down the drain moves through the sewer and is treated at a WRRF along with other sewage.
Some WRRFs have anaerobic digesters to process wastewater solids/sewage sludge, while others do
not. Both WWT with and without AD are included in this pathway. All wasted food travelling down the
drain and through the sewer to the WRRF is in the sewer/wastewater treatment pathway, whereas
wasted food delivered directly to AD (typically by vehicle) at the WRRF is in the AD pathway.
Figure 2-11 diagrams the WWT management pathway and includes optional AD treatment of the resulting
wastewater solids. Other possible wastewater solids treatments include aerobic digestion, alkaline
stabilization, thermal drying, composting, pasteurization, and emerging technologies.
When entering this management pathway, wasted food is pre-processed by grinding at the residence or
commercial institution and introduced to the sewer system for transport to the WRRF. Once at the WRRF,
wasted food is subjected to the same treatment processes as wastewater. Wasted food will typically
partition with other wastewater solids (i.e., through settling) and be separated from the resulting liquid
effluent in primary, secondary, or tertiary clarification steps. Depending on quality, the resulting
wastewater solids can be beneficially applied to land or disposed of in landfills or controlled combustion
facilities. Wastewater solids that have been treated to meet federal and state standards for beneficial use
are called biosolids.
System Boundary
Wasted
food
Grinding
Land Application
Sewer
Collection
Wastewater
Treatment -
Wastewater
Solids
"I Anaerobic
A
Compost
or Other Treatment
Key
May include transport
0
Waste
disposal
FIGURE 2-11. DIAGRAM OF WASTED FOOD PROCESSING VIA SEWER/WASTEWATER
TREATMENT
The benefits and impacts of this pathway depend on the technology and performance of the WRRF and
biosolids management. According to the most recent Clean Watersheds Needs Survey, around 29% and
41% of the U.S. population sent wastewater to secondary and advanced treatment systems, respectively,
in 2012 (U.S. EPA 2016). While advanced treatment systems (tertiary or greater) are more likely to be
capable of enhanced nutrient removal, secondary treatment systems can be designed or retrofitted to
remove nutrients (prevalent in wasted food) from wastewater effluent. Generally, though, more WRRF
treatment steps lead to higher energy requirements, potentially negating energy recovery from wasted
food.
Chapter 2. Wasted Food Pathways
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Recent estimates of methane emissions from centralized WRRFs are 1.9 times higher than previous
estimates (Moore et al. 2023), suggesting that existing studies may systematically underestimate ChU
from WRRFs. However, these comprehensive studies (Moore et al. 2023; Song et al. 2023) do not
address the contribution of wasted food to sewer and WRRF emissions, so further study is needed. The
findings of Song et al. (2023) that leaks, incomplete flaring, and other management issues are the main
source of ChU at WRRFs with AD suggests that operation and management may be more important than
process selection in minimizing GHG, and likely other, impacts.
Prevalence and Value
About 80% of U.S. households are serviced by one of the country's 16,000 operational WRRFs (ASCE
2021). The remaining 20% of households dispose of wastewater in onsite treatment systems (e.g., septic
systems) that typically lack the capacity to process wasted food. On average, 150-250 dry metric tons of
biosolids are produced per million gallons of wastewater treated (Beecher et al. 2022). This varies
depending on wastewater and biosolids treatment technologies. Biosolids represent an economic cost to
the wastewater treatment industry, with the wet ton paid for management in 2018 reported as $49 USD
composting, $58 USD landfilling, $62 USD land application, and $95 USD controlled combustion
(Beecher et al. 2022).
Sewer Collection
Wasted food collection via the sanitary sewer system can lead to anaerobic conditions that favor methane
formation for the portion of wasted food that degrades during transportation to the WRRF. Solids type
(e.g. wasted food) and loading, temperature, hydraulic residence time, and other factors contribute to
methanogenesis in sewers, but establishing relationships between sewer parameters and
methanogenesis is complex (Song et al. 2023). Of the studies addressing this, a 2012 study assumed
that 15% of wastewater biodegradable chemical oxygen demand (COD) is degraded during transport,
10% anaerobically and 5% aerobically, with the carbon share released as methane and carbon dioxide
(Parry and WERF 2012).50 Employing this assumption, the analysis found that methane emissions during
sewer transport are the largest source of GWP in the WWT pathway, with gross emissions exceeding the
benefit associated with AD energy recovery. More recently, a comparative LCA of multiple wasted food
pathways assumed that 6% of wasted food volatile solids are degraded during sewer transport (Edwards
et al. 2018).51 Other studies have neglected any methane formation potential in sewers altogether. The
true magnitude of sewer methane emissions is a function of wasted food degradability and conditions and
residence time in the sewer system (Parry and WERF 2012).
Expanding wasted food management via the sewer/WWT pathway incurs the risk of introducing additional
FOG waste to sewers, which contributes to bottlenecks and blockages, increasing sewer overflow events
and maintenance needs (Wallace et al. 2017). However, studies of long-term impacts for non-FOG
wastes have shown that marginal additional sewer deposits from wasted food—when high-specific-gravity
wasted food (e.g., bones and egg shells) and/or FOG-rich wasted food are excluded—are small and have
a minor impact on sewer operations (Mattsson et al. 2015).
Wasted food in sewer systems may also lead to pipe corrosion in municipalities with small or aging pipes
(due to wasted food's high biological oxygen demand (BOD) interacting with sulfates to transform to
hydrogen sulfide and sulfuric acid), the need for additional energy in systems which require pumping
stations, and/or increased organic pollutants in sewer effluent direct discharges in combined or low-flow
systems (U.S. EPA 2021b).
Secondary Treatment
Once at the wastewater treatment facility, wasted food undergoes the same processing steps as the
remaining bulk wastewater. The effect that wasted food has on primary and secondary treatment
processes is different for every WRRF and must be considered on a case-by-case basis. Parry and
WERF (2012) report that 20% to 45% of BOD and 45% to 70% of total suspended solids (TSS) are
typically removed during primary clarification. The analysis of Edwards et al. (2018) assumes that 34% of
wasted food settles out in the primary clarifiers, 26% is metabolized to carbon dioxide in secondary
treatment, while 33% settles out with the waste-activated sludge in secondary clarification. Increased
BOD loading to secondary treatment increases aeration electricity demand in secondary treatment (Parry
and WERF 2012).
Chapter 2. Wasted Food Pathways
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Biogas Production
As discussed in Section 2.4, wasted food holds potential for energy recovery. While only about one out of
ten U.S. WRRFs is equipped with anaerobic digesters,52 more than half of all biosolids generated in the
U.S. are treated by AD, since AD is nearly ubiquitous at the nation's largest WRRFs (Beecher et al.
2022). These facilities have the potential to recover wasted food energy, avoiding fossil energy production
and crediting the sewer/WWT pathway with associated environmental benefits. However, biogas
production at WRRFs that can be attributed to wasted food sent down the drain does not outweigh
fugitive methane emissions, resulting in a net environmental impact even if energy is recovered via AD.
Elevated ChU emissions from WRRFs equipped with AD are mainly caused by biogas leakage from
anaerobic digesters and incomplete flaring of excess ChU (Song et al. 2023).
Recent estimates of methane emissions from centralized WRRFs are 1.9 times higher than previous
estimates (Moore et al. 2023), suggesting that existing studies may systematically underestimate ChU
from WRRFs. However, these comprehensive studies (Moore et al. 2023; Song et al. 2023) do not
specifically address the contribution of wasted food to sewer and WRRF emissions.
Biosolids
Biosolids are wastewater solids/sewage sludge that have been treated to reduce pathogens and
contaminants and stabilize organic compounds. Often biosolids are dewatered or thickened in addition to
undergoing stabilization via AD, aerobic digestion (such as in aerated lagoons), thermal or air drying,
composting, or another treatment method. Biosolids must meet federal, state, and local regulatory
standards for pathogens and contaminants in order to be beneficially reused. The federal biosolids rule is
contained in Title 40 of the Code of Federal Regulations (CFR) Part 503 and defines two types of
biosolids with respect to pathogen reduction. Class B biosolids contain some pathogens and have
restrictions on their use to limit public exposure, such as buffer requirements and crop harvesting
restrictions. Class A biosolids have virtually no pathogens and fewer restrictions on their use. Most Class
A biosolids classify as "Exceptional Quality" (EQ) and are safe for use anywhere, including home gardens
and public parks due undetectable levels of pathogens and pollutants. Composted biosolids frequently
qualify as EQ. For biosolids to be land applied, heavy metals must not exceed the ceiling concentrations
set out in federal and state regulations.
About 53% of biosolids in the U.S. are land applied as fertilizers or soil amendments for agriculture,
landscaping, and land reclamation (Beecher et al. 2022). Long-term studies of application of biosolids
show clear benefits to soil carbon (Ippolito et al. 2010; Brown et al. 2011; Ippolito et al. 2021; Sullivan et
al. 2021). Potential environmental impacts from biosolids land application include transportation and
application emissions, including nutrient runoff. When land applied, biosolids provide essential nutrients
and organic matter to crops and soils and offer a cheap fertilizer option for farmers. Application rates for
biosolids are often determined by a crop's nitrogen needs (agronomic loading rate). Wasted food can
increase nitrogen levels in biosolids which may require nutrient removal during treatment or a decreased
application rate. In the reviewed LCAs of sewer/WWT, carbon sequestration from biosolids land
application was not assessed. But biosolids application does contribute to soil health and carbon
sequestration as discussed in Chapter 4.
If biosolids do not meet quality standards that allow for land application, or appropriate land for application
is not available, biosolids may be disposed of by landfill or controlled combustion. Wasted food treated as
a component of biosolids is exposed to contamination resulting from other wastewater components, such
as PFAS, as described in Section 4.5.
It is important to note wasted food sent down the drain makes up a tiny fraction of biosolids that result
from wastewater treatment process.
Wastewater Effluent
Depending on the layout and performance of the specific WRRF, some fraction of all nutrients,
BOD/COD, and pollutants in wasted food will be released to surface water with wastewater effluent. For
example, in the analysis of Edwards et al. (2018), approximately 1.5% of the original COD load is
assumed to be released with treatment plant effluent; significant fractions of N may be released in effluent
or to the atmosphere (Morelli et al. 2019). Wasted food has a high nutrient content and can increase the
influent nutrient load to be treated at WRRFs, many of which face increasingly stringent nutrient limits due
Chapter 2. Wasted Food Pathways
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to concerns about eutrophication of local waterbodies (Scheehle and Doom 2002; Carey and Migliaccio
2009). On the other hand, if applied at appropriate rates, wastewater effluent can be a source of nutrients
if used as irrigation water (Sullivan et al. 2021; Vivaldi et al. 2022). If additional wasted food is processed
via the sewer/WWT pathway, WRRFs can either increase treatment demands (increasing energy
required) to remove additional nutrients or effluent nutrient levels will increase.
TABLE 2-13. SEWER/WASTEWATER TREATMENT: ENVIRONMENTAL DRIVERS
Sources of
Environmental
Impact
Methane emissions from sewer transport and WWT processes.
Energy demand of aeration during secondary treatment, which is dependent on the
level of biochemical and chemical oxygen demand (BOD and COD, respectively).
Increased energy demand for nutrient removal at facilities with nutrient permits
(wasted food adds to the nutrient load in wastewater).
Source of
Environmental
Benefit
Reduced production and use of fossil energy due to biogas energy recovery if AD is
present.
Displacement of conventional fertilizer production if land application of biosolids.
Long-term carbon sequestration and contributions to soil health if land application of
biosolids (Section 4.6).
Options to
Reduce Impact
Reduce BOD/COD load to secondary treatment (e.g., via enhanced primary
clarification) to reduce plant energy demand.
Utilize the WWT pathway in areas that practice AD with biogas utilization.
Additional wasted food inputs for certain biological nutrient-removal processes may
improve nitrogen removal, reduce net operational costs, and lower aeration energy
demand (Kim et al. 2019).
Avoid landfilling biosolids. Manage biosolids for safe, beneficial reuse by treating to
high quality through less energy-intensive methods, such as composting.
Other
Considerations
Additional wasted food in sewers may lead to solids deposition and clogging and
affect sewer performance.53
Nutrient limits for wastewater effluent vary between WRRFs and will determine the
need for and additional impact of nutrient removal.
Sewer conveyance avoids several logistical and operational challenges associated
with wasted food collection that would otherwise be necessary for the AD pathway
(e.g., separate collection and transport infrastructure).54
Chapter 2. Wasted Food Pathways 2-35
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2.11 Unharvested/Plowed In
The unharvested/plowed in pathway signifies leaving crops ready for harvest in the field or tilling them
into the soil. Most unharvested food is reincorporated into soil, although sometimes livestock graze fields
before tilling (Gillman et al. 2019). For grazing, unharvested crops must be paired with specific animals to
meet nutritional requirements (Winans et al. 2020). Unharvested crops that are reincorporated into the
soil help to build soil organic matter, improving soil health and supporting future crop growth. Further
discussion of the soil health benefits provided by the unharvested/plowed in pathway is in Chapter 4.
The quantity of edible food left unharvested is poorly understood. Both FAO and ReFED provide high-
level estimates indicating that 20% of fruits and vegetables are left unharvested on agricultural fields.
Recent measurements of food loss for 20 crops across 123 fields in California found a loss rate above
30%, which equates to over 11,000 kg of produce per hectare. The authors note that "decisions to leave
produce in fields result from a complex mix of consumer preferences, buyer specifications, marketplace
economics, labor costs, weather and other factors" (Baker et al. 2019).
Only one LCA study that quantified the environmental impacts and benefits of unharvested field crops
was identified, reporting a GWP of 0.31 kg CChe / kg tomatoes plowed in (Gillman et al. 2019). Given the
lack of available studies, this section provides perspectives based on themes in the literature.
Avoiding Supply-Chain Impacts
Once food is harvested, additional transportation and resources are required to package it, distribute it,
and deliver it to humans (Kummu et al. 2012; Bernstad et al. 2017). Therefore, it is environmentally
preferable to prevent food that will not be eaten from entering the supply chain in order to avoid these
impacts. The unharvested/plowed in pathway provides an alternative to allowing wasted food to enter the
supply chain, while still using the organic material for beneficial use.
Energy Consumption
Reincorporating unharvested plant material back into the soil requires energy consumption for equipment
operation. The EU (European Union) FUSIONS project performed a basic LCA of wasted tomatoes,
comparing plowing-in of unharvested crops with landfilling a packaged, unsold product. This analysis
showed that the marginal energy required for tractor use was an order of magnitude smaller than the
energy required for transport, packaging, and retail (Scherhaufer et al. 2015).
Soil Reincorporation
Incorporating crops back into the field provides necessary nutrients for subsequent crops (Alexander et
al. 2017). If farmers use this input of nutrients to justify reducing subsequent fertilizer applications, then
an avoided fertilizer benefit can be attributed to unharvested crop recycling. Leaving crops on the field
can also help build soil carbon, especially when combined with less intensive tillage practices (Al-Kaisi
and Yin 2005; Omonode et al. 2007). See Section 4.6 for further discussion of qualitative relationships to
soil health.
TABLE 2-14. UNHARVESTED I PLOWED IN: ENVIRONMENTAL DRIVERS
Source of Environmental
Impact
Energy demands of tillage.
Sources of
Avoided fertilizer production: only warranted if the producer reduces
fertilizer application due to this practice.
Environmental Benefit
Long-term carbon sequestration and contributions to soil health resulting
from recycling of unharvested crops (Section 4.6).
Option to Reduce Impact
Follow recommended tillage practices to minimize erosion and improve
soil health (Claassen et al. 2018).
Chapter 2. Wasted Food Pathways
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2.12 Emerging Pathways
While the report focuses on the eleven pathways described above, there are a number of alternative
wasted food pathways that are either appropriate only for a very specific wasted food type, or are
"emerging", indicating that they rely on processes that might be still at the bench or pilot scale, or that
have not yet been widely adopted. These pathways include, for example, hydrothermal carbonization,
rendering, and the group of thermochemical processes that includes pyrolysis, torrefaction, and
gasification. Because of their dynamic status or lack of available data, these pathways are excluded from
the quantitative analysis and some examples are briefly discussed in Appendix E.
2.13 Key Issues Across Pathways
This section describes some of the cross-cutting issues relevant to the environmental impacts and
benefits of multiple pathways: technology and operations, collection and transportation, infrastructure,
and feedstock characteristics and requirements.
Technology and Operations
While it is beyond the scope of this analysis to comprehensively discuss how different combinations of
technologies and operational practices affect the environmental performance of wasted food pathways,
the discussion highlights the potential importance of these factors.
Technology
The technological basis and operational and management practices at specific facilities can affect
environmental impacts within a particular pathway. Given the range of environmental performance seen
in studies, the technologies selected, and the operation of management pathway may be just as
important to environmental impact as the selection of the wasted food pathway itself. Within a given
pathway, there are technology choices that may strongly influence environmental performance. For
example, for composting, energy demand and emissions to air will vary depending on the type of
composting system (e.g., aerated static pile or windrow). Wthin particular technology categories, capture
or recovery efficiency may vary. Energy and heat recovery efficiency are critically important in determining
avoided energy benefits for AD and controlled combustion pathways. Short- and long-term gas capture
efficiency drives the degree to which landfills can lower their GWP impacts.
Operations
Wthin a given technological approach, the operation of a specific facility will dictate environmental
performance. The environmental performance of wasted food pathways is highly variable. Among the
assessed studies, there are significant ranges in impacts per mass of wasted food managed. Examples of
operational factors that can impact performance include:
For AD, is biogas flared or combusted in a boiler, electrical engine, or CHP engine?
For compost, how is the pile constructed (C:N ratio) and are aerobic conditions maintained?
For AD and sewer/WWT, how are digestate and biosolids treated, and what is the energy
demand of that process?
For any pathway with application to land (compost, AD, land application, sewer/WWT,
unharvested), is the wasted food-derived material being applied in keeping with appropriate
agronomic practices and reducing fertilizer or peat consumption?
For controlled combustion, what are the emission controls, and are they operated and maintained
adequately?
For donation, what fraction of incoming food is ultimately wasted?
Collection and Transportation
All pathways except source reduction must collect and transport wasted food for processing.
Chapter 2. Wasted Food Pathways
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Sewer Collection
Wastewater treatment is the one wasted food pathway that utilizes sewer, rather than vehicles, for
transportation. Potential benefits of the sewer/WWT pathway are avoiding inefficient trucking of heavy
wasted food or capturing waste heat from sewers. However, research indicates that fugitive methane
from anaerobic decomposition in sewers may negate the energy advantage of pumping wasted food
through sewer lines to WRRFs rather than trucking (Parry and WERF 2012; Zan et al. 2020).
Vehicle Collection
Most other wasted food pathways require collection by vehicle. The magnitude of environmental impact
associated with waste collection and transportation varies widely across the reviewed studies, indicating
that potential transportation impact is influenced by factors beyond wasted food pathway selection, such
as the location of collection. While findings vary, the majority of the studies reviewed include
transportation/collection within the scope of their analysis. Several authors (Parry and WERF 2012;
Ahamed et al. 2016; Edwards et al. 2017; Khoshnevisan et al. 2018; Bartocci et al. 2020) conclude that
waste collection is a negligible or minor contributor to a number of impact categories, including GWP,
acidification, eutrophication, energy demand, and ecosystem quality. EPA's WARM Model showed that
transportation accounted for 7% of the net GWP impact for composting, 4% of the net GWP impact for
combustion, and 3% of the net GWP impact for landfilling (U.S. EPA 2020c).
An analysis of wasted food management in Italy analyzed the environmental contributions of wasted food
collection across several management pathways and impact categories. The analysis found that in 10 of
12 impact categories the waste collection phase contributed less than 10% of impact for all pathways.
Land occupation (i.e., the amount of land required for a system or a process) was strongly influenced by
wasted food collection, but impact contributions were still less than 20%. Average transportation
distances in this study were approximately 30 kilometers (km). The study's authors promote efficient,
localized collection and pre-processing systems as a means to limit environmental impact (Mondello et al.
2017).
Other authors (Righi et al. 2013; Al-Rumaihi et al. 2020; Lee et al. 2020) conclude that waste collection
and transportation are a major contributor to environmental impact for several impact categories,
including GWP and acidification. For example, Lee et al. (2020) showed moderate to major contributions
to gross impact from collection and transportation for GWP, acidification, eutrophication, and ecotoxicity
across four pathways (AD, landfill, composting, and controlled combustion). Collecting wasted food and
transporting it to the transfer station contributed more to gross impact than did subsequent transportation
to the management facility. Their analysis considered a worst-case scenario for collection impact in which
collection vehicles are operating at maximum capacity five days per week. Transportation distances after
collection ranged from 45 to 93 km. The magnitude of impact associated with collection and
transportation was similar across pathways.
Khoshnevisan et al. (2018) performed a sensitivity analysis on transportation distance and showed that
when hauling distance was increased from 25 to 150 km, net GWP benefit decreased by approximately
3% and the net benefit for ecosystem quality decreased by more than 10%.
The relative contribution of transportation to gross environmental impact is dependent on the total
magnitude of that impact. For example, the relative contribution of wasted food collection and
transportation will likely be larger for a well-managed compost system with limited process emissions and
energy consumption than for a poorly managed compost system with higher associated impacts. This
would be true even in instances where the absolute magnitude of transportation impacts was consistent
across both hypothetical scenarios. The analysis of Ahamed et al. (2016) provides an example of this
phenomenon, where similar transportation burdens for controlled combustion and AD pathways yield
divergent contributions to gross impact due to the greater impact of controlled combustion process
operation. This example highlights one of the challenges of accurately gauging the contribution of
transportation and other ubiquitous processes in the context of LCA. While transportation may or may not
contribute a large relative share of gross impact per unit mass of wasted food managed, the cumulative
contribution of transportation to wasted food management impact is likely to be substantial and persistent.
Chapter 2. Wasted Food Pathways
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Infrastructure
Infrastructure constitutes the non-consumable physical structures and equipment required to operate a
management pathway, such as tanks, piping, mechanical equipment, and accessory buildings.
Depending on the study, infrastructure impacts may also include burdens associated with construction
(e.g., fuel consumption). Infrastructure environmental impacts accrue in upstream supply-chains and are
allocated to the study's functional unit by amortizing over the expected lifespan of the equipment and the
total quantity of material processed (Frischknecht et al. 2007). Typically, but not always, infrastructure
contributions to overall impacts are small relative to the other issues discussed above.
Contributions of infrastructure to environmental impact can vary considerably across impact categories
and between pathways. The analysis of Lee et al. (2020) found that infrastructure made a negligible
contribution to gross impact for GWP and acidification across AD, landfill, compost, and controlled
combustion pathways. Mayer et al. (2020) reported that the "provision of ancillary or capital goods only
affect the GWP very little." Salemdeeb et al. (2017) showed that infrastructure for animal feed production
contributes negligibly to fossil fuel depletion for both wet and dry animal feed production. In the latter
study, infrastructure contributions to eutrophication were minor and moderate for landfill and controlled
combustion pathways, respectively. Ecotoxicity was more strongly influenced by infrastructure, with non-
negligible contributions to gross impact for all pathways, including moderate and major contributions for
landfill and controlled combustion pathways, respectively.
Feedstock Composition, Contamination and Pre-Treatment
The composition, contamination, or need for pre-treatment of wasted food can all affect the selection and
performance of pathways. Characteristics of the wasted food stream inform which pathways are possible.
For example, a pathway may require food to be safe for human consumption, mostly free of contaminants
such as packaging, or consistent in volume and composition. Those pathways that require low levels of
contamination may also necessitate source separation and separate collection.
Table 2-15 provides high-level examples of the qualitative requirements for the different wasted food
pathways with respect to the level of homogeneity expected in the waste material and the level of non-
food contamination allowed. The table also provides information on the collection requirements for each
pathway.
Composition of Wasted Food
The composition of wasted food can affect selection of management pathways as well as performance of
those pathways.
Edibility: The donation and upcycling pathways are only applicable for the portion of wasted food
safe to consume.
Homogeneity: Certain pathways may require or perform better with homogenous wasted food.
For example, the AD process can benefit from a consistent waste stream that provides a stable
diet to the biological community.
Moisture content: Environmental performance of controlled combustion and dry animal feed
pathways is particularly sensitive to the moisture content of wasted food feedstock. High moisture
content leads to increased impacts for these pathways.
Energy content: The controlled combustion and AD pathways will have improved environmental
performance for wasted food feedstocks with a high energy content. Other pathways are less
influenced by the energy content of wasted food.
Oil content: A comparison of AD and controlled combustion pathways examined the effect of
wasted food oil content on pathway preference. Oil content in this study did not refer to FOG;
instead, the focus was on wasted food with oil contents between 2.5% and 10%. The authors
indicated that oil content is not expected to have a dramatic effect on controlled combustion or
AD pathway performance. For AD, the authors noted that without special reactor designs, oil is
difficult to digest due to low solubility and biodegradability and floe shielding, which limits oil's
availability for biochemical reactions (Ahamed et al. 2016).
Chapter 2. Wasted Food Pathways
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Nutrient, protein, and carbon content: For several pathways, the quantity of avoided product and
carbon sequestration benefits depend on these aspects of wasted food composition. For
example, wasted food with a higher protein content could reasonably be assumed to displace a
larger quantity of animal feed, leading to greater avoided product benefits.
A comprehensive discussion of how wasted food composition affects pathway environmental
performance is beyond the scope of this analysis.
Contamination of Wasted Food
The presence of contamination (including presence of pathogens and physical and chemical
contaminants) in wasted food can influence selection of applicable wasted food pathways and the quality
of derived end products. For example, upcycling and donation both require wasted food that is still fit for
human consumption, requiring a certain level of hygiene in the management pathway. When this level of
food quality is not met, wasted food in the upcycling and donation pathways will be diverted to another
pathway, such as landfilling. In general, issues with food quality or contamination often mean that portions
of wasted food or wasted food intended for specific pathways are diverted to a pathway with less stringent
quality requirements (Vandermeersch et al. 2014; Eriksson and Spangberg 2017). These
interconnections are shown in the management pathway flow diagrams in preceding sections, where pre-
treatment often produces a residual stream that is sent to disposal.
Contaminants may be pathogens or physical or chemical contaminants. Examples of physical
contaminants include noncompostable plastics or metal or glass; per- and polyfluoroalkyl substances
(PFAS) is an example of a chemical contaminant that can be found in wasted food streams.
The presence of contamination in a wasted food stream is often linked to whether the source of food is
pre- or post-consumer waste. Post-consumer wasted food is typically thought of as having a higher level
of contamination and may therefore not be suitable for all pathways, especially in the absence of source
separation and other, potentially extensive, pre-treatment steps. While generally true, grocery store waste
is an example of pre-consumer wasted food with potentially high levels of contamination (e.g.,
packaging).
Limiting contamination in wasted food is essential for the operation of certain pathways. The animal feed,
AD and land application pathways have historically sourced the majority of processed waste from the pre-
consumer manufacturing sector (Figure 1-1), which is likely related to consistency and low contamination
levels in pre-consumer waste. The composting pathway as well benefits from low levels of contamination
to increase product value. Microplastics are prevalent in wasted food-derived composts and digestates,
though amounts, sizes, and types of plastic particles vary (Porterfield et al. 2023). Effective and efficient
pre-treatment processes, discussed below, will be required to allow large volumes of post-consumer
wasted food to be utilized by pathways with strict contamination tolerances (Table 2-15). For the animal
feed pathway, contamination can include the presence of animal products in the wasted food stream as
state and federal regulations prohibit feeding animal waste to animals or require pre-treatment in some
contexts (Leib et al. 2016).Several of the pathways—such as controlled combustion and landfill—are
better able to handle physical contamination in waste streams than other pathways. Physical
contamination of wasted food streams can limit the range of applicable management pathways. Chemical
contaminants in wasted food and co-treated wastes also drive some environmental impacts (human and
ecotoxicity) and affect the use of resulting materials as fertilizers and soil amendments in agricultural
systems. See Table 2-15 for more information.
Pre-Treatment of Wasted Food
Pre-treatment of wasted food is often employed to produce a consistent feedstock, free of physical
contaminants that could hinder management pathway operation. However, by using additional energy,
pre-treatment may increase the environmental impacts of the pathway. Most studies that include pre-
treatment focus on three basic steps: sorting, grinding, and mixing. Several studies include additional
thermal pre-treatment steps such as pasteurization and sterilization or de-packaging processes.
Additional separation equipment such as crushers, screens and magnets may be required ahead of the
de-packager, increasing overall pre-treatment energy use.
Source separation (i.e., separation by the generator) and separate collection of the food waste stream is
one of the most fundamental pre-treatment sorting steps and can have a considerable effect on the
Chapter 2. Wasted Food Pathways
2-40
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quantity and quality of wasted food available. Pathways requiring high-quality feedstock with low levels of
contamination (see Table 2-15) are likely to require this, particularly for commercial and residential
wasted food.
Additional pre-treatment sorting may be required for pathways with low or very low tolerance for physical
contamination, such as composting and animal feed. For this sorting step, Edwards et al. (2018) found
that rejection of additional non-organic materials ranged from 5% to 45%, with an average rejection rate
of 21%. Khoshnevisan et al. (2018) examined several methods for combined sorting, mixing, and size
reduction, such as biopulping, screw press, and disc screening prior to AD. The authors concluded that
pre-treatment steps make a minor contribution to GWP impact. An LCA of co-digested dairy products
found that pre-treatment had a negligible effect on a broad range of environmental impacts, including
GWP, eutrophication, acidification, and human toxicity (Kopsahelis et al. 2019). A review of advanced AD
pre-treatment options found that pre-treatment processes that are mechanical or chemical in nature are
environmentally preferable to thermal pre-treatment processes due to the higher energy demand of the
latter (Tiwary et al. 2015). Use of residual waste heat is proposed to reduce the environmental impact of
thermal pre-treatment processes.
De-packaging as a pre-treatment step for AD and composting pathways was studied in an analysis of
Italian supermarket wasted food. Electricity demand of the de-packaging step was a major contributor to
gross environmental impact for all pathways and impact categories considered, exceeding impacts
associated with collection and transportation for all pathways and also exceeding impacts from treatment
process operation for AD (Mondello et al. 2017).
Elginoz et al. (2020) considered the environmental benefits of using wasted food to produce a volatile
fatty acid stream, which could then be used as the carbon source for AD (thus displacing the need for
methanol production for the digester). The study found that one of the main drivers of impacts for their
system was the energy required to thermally pre-treat the wasted food. This finding points to the
importance of temperature and moisture: it is energetically expensive to heat wasted food through energy
inputs, rather than through beneficial, exothermic biological reactions.
Chapter 2. Wasted Food Pathways 2-41
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TABLE 2-15. HIGH-LEVEL SUMMARY OF ALLOWABLE CONTAMINATION, REQUIRED HOMOGENEITY, AND COLLECTION
REQUIREMENTS FOR WASTED FOOD PATHWAYS
Pathway
Collection
Collection Notes
Contamination
Tolerance
Contamination Notes
Homogeneity
Required
Donation
Separate
Often packaged
Very low
No contamination or co-wastes; must meet food
safety standards
Low
Upcycling
Separate
Generally
collected from
production or
processing
Very low
No contamination or co-wastes; marketable as
food once processed
High3
AD
Separate or
mixed with
other organics
Output quality
benefits from
source separation
Medium55
Pre-processing can remove some physical
contaminants (e.g., wrappers)
Medium
Animal Feed
Separate
Very low56
Wasted food and any co-wastes must meet (or be
processed to meet) animal safety requirements;
must remove packaging that is unsafe to
consume
Medium57
Composting
Separate or
mixed with
other organics
Output quality
benefits from
source separation
Low58
Pre-processing can remove some physical
contaminants; quality requirements may depend
on ultimate use (e.g., consumer gardens,
agricultural fields, general land application)
None
Controlled
Combustion
Mixed
High
Any waste permissible
None
Land
Application
Separate
Often collected
from industrial,
pre-consumer
waste streams.
Medium
Pre-processing can remove some physical
contaminants
None
Landfill
Mixed
High
Any waste permissible
None
Chapter 2. Wasted Food Pathways
2-42
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Pathway
Collection
Collection Notes
Contamination
Tolerance
Contamination Notes
Homogeneity
Required
Sewer/WWT
Mixed with
other organics
(at sink and in
sewer)
Some wasted
food (e.g., FOG)
discouraged for
sewer
maintenance
Medium
Co-wastes (e.g., sewage) are acceptable and are
generally also organic; processes are typically in
place for removing foreign materials (e.g., bar
screens)
None
Unharvested
/Plowed In
Not applicable
Not applicable
Not applicable
No potential for contamination exists
None
a High homogeneity implies that for a given product from the pathway (e.g., an energy bar made of spent brewer's grains or a chemical precursor), the input
wasted food must be homogeneous. However, across products, the homogeneity is low (i.e., a variety of feedstocks can be used to make different products).
Chapter 2. Wasted Food Pathways 2-43
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CHAPTER 3
LIFE CYCLE ASSESSMENT
The eleven common wasted food pathways discussed in this report encompass a wide range of
technological approaches and generate a spectrum of beneficial products, as described in Chapter 2.
While all management pathways fulfill the essential service of managing wasted food, they vary in terms
of environmental benefits and impacts. This section reviews relevant LCA literature to compare the
environmental performance of wasted food pathways across a range of environmental indicators,
focusing particularly on LCA study scenarios where wasted food is the feedstock whenever possible. This
analysis focuses exclusively on environmental performance and does not address social and economic
factors related to the pathways.
The first section (Section 3.1) describes the environmental indicators included in the LCA literature
search, and Section 3.2 provides detail on the LCA review methodology. Section 3.3 provides a
qualitative summary of pathways' environmental impacts and benefits. In Section 3.4, we look across
studies (inter-study) to understand the range of environmental impact estimates for each wasted food
pathway in the literature, while in Section 3.5, we look within studies (intra-study) to compare wasted food
pathways. Section 3.6 discusses soil health, the only selected environmental indicator not included in the
analysis within the previous two sections. Section 3.7 discusses the limitations of LCA and this LCA
review. In Section 3.8 and 0 we synthesize the LCA results and the discussion of environmental drivers in
Chapter 2 into a ranking of the eleven wasted food pathways.
3.1 Environmental Indicators
The LCA literature review focused on the eleven environmental indicators described in Table 3-1. These
indicators were chosen due to their relevance to the wasted food pathways. Indicators were not chosen
based on availability of inventory data or impact factors; inventory data for GWP (e.g., CO2 emissions) are
commonly reported and impact factors have international consensus; inventory for water use is less
commonly reported, and impact factors are robust; inventory for soil health can be difficult to capture
(e.g., total N vs. bioavailable N are not always distinguished), and impact factors are nascent. Impacts
and benefits related to these indicators may result from wasted food management processes and/or from
energy use during wasted food management processes, as well as from avoided energy or product (i.e.,
food, animal feed, fertilizer or peat) use due to outputs made from resources recovered from wasted food
during the management pathway.
Chapter 3. Life Cycle Assessment 3-1
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TABLE 3-1. ENVIRONMENTAL INDICATORS
Global Warming
Potential (GWP)
Soil Carbon
Sequestration
GWP impacts are reported in carbon dioxide equivalents (CCheq), which
represent the heat-trapping capacity of the GHGs relative to carbon
dioxide (CO2) over a certain time horizon, typically 100 years (IPCC 2013).
Biogenic carbon dioxide (e.g., from carbon incorporated by crops during
growth stage) that is released back to the environment within the
assessed time horizon is often treated as carbon neutral in LCA studies
(ISO 2018). Biogenic carbon that is stored beyond the time horizon is
typically treated as a credit (negative value) (ISO 2018). GWP impacts of
wasted food pathways are primarily related to combustion processes that
release fossil CO2, anaerobic decomposition of organic matter that
releases methane (CH4), and agricultural emissions of nitrous oxide (N2O).
Soil carbon sequestration is the processes by which carbon originating
from the atmosphere is stored in the soil in a stable form. This benefit is
generally quantified as part of the GWP indicator.
Energy Demand
Energy demand is a cumulative inventory category, which may include
non-renewable energy extracted and renewable energy used. It typically
includes processing and transportation energy and energy content of non-
waste feedstocks. In this report, energy demand includes both the energy
requirements of a wasted food management pathway and credits for any
energy recovered through that pathway. Energy demand contributes to
GWP indicator (above) but provides an additional perspective by including
only energy and excluding GHG emissions from anaerobic decay of food,
for example.
Acidification
Acidification quantifies the acidifying effect of substances on the terrestrial
environment. Sulfur oxides (SOx), nitrogen oxides (NOx), and other
pollutants such as ammonia (NH3) may lead to acidification (Bare et al.
2003). Acidification emissions are typically from decomposition (NH3) or
combustion (SO2, NO2) processes.
Particulate
Matter (PM)
Formation
PM formation is driven by primary pollutants (e.g., PM2 5) and secondary
pollutants such as sulfur oxides (SOx), nitrogen oxides (NOx) and
ammonia (NH3) that react in the atmosphere to form PM (Huijbregts et al.
2017). Primary PM emissions are associated with combustion processes,
as are secondary emissions of SOx and NOx; decomposition processes
release NH3.
Human Toxicity
Human toxicity describes effects of substances on humans. The modeled
distribution of substances in environmental media (air, water, soil,
vegetation) is coupled with exposure and effect data. Human health
impacts are modeled based on carcinogenic and non-carcinogenic effects.
Exposure via inhalation and ingestion are typically considered; dose-
response effects are largely extrapolated from acute models (Fantke et al.
2018). Human toxicity emissions, in the wasted food context, are typically
associated with contaminants released during combustion processes.
Ecotoxicity
Ecotoxicity describes effects of substances on ecological receptors. The
modeled distribution of substances in environmental media (air, water,
soil, vegetation) is coupled with exposure and effect data. Ecological
impacts in the aquatic environment are typically expressed in terms of the
potential fraction of species affected (i.e., disappearing). These impacts
are typically based on species sensitivity distributions across multiple
phyla, accounting for bioavailability of compounds in the aquatic
Chapter 3. Life Cycle Assessment
3-2
-------
environment (Owsianiak et al. 2022). Ecotoxicity emissions, in the wasted
food context, are typically associated with contaminants released during
combustion processes.
Eutrophication
Eutrophication is the process in which freshwater, marine, and terrestrial
systems receive surplus limiting nutrients, resulting in excessive growth of
plants and algae and therefore alterations in species composition or
productivity (Henderson 2015). Eutrophication impact is modeled by
translating nutrient emissions into phosphorus or nitrogen equivalents
(e.g., Neq), which relates nutrients to potential primary productivity, and
from which species impacts can be calculated (Payen et al. 2019).
Eutrophication emissions may result from energy demand and combustion
(NOx), decomposition processes (NH3), and fertilizer application or
wastewater treatment (nitrogen and phosphorus compounds).
Water
Consumption
Water consumption typically refers to freshwater that is withdrawn (from
surface or groundwater; see Pfister et al. (2017)) and evapotranspirated,
incorporated into products or wastes, transferred to different watersheds,
or discharged into the sea after use (Bayart et al. 2010). Water withdrawal
(e.g., for cooling in power plants) is different from water consumption, as
withdrawn water can be returned to the same watershed it was originally
extracted from. Many studies use the phrase "water use" to refer to
consumption, but this report uses the more precise term "water
consumption."
^3
Land
Occupation
Total land occupation (e.g., in square meters during a year) is the amount
of land required for a system or a process. Many studies go further and
report the effects of that use on biodiversity. Given the variety of modeling
approaches to connect land occupation to biodiversity, comparison of
biodiversity impacts is challenging and is excluded from this analysis.
Soil Health
Soil health is a broad, evolving concept that captures the ability of soils to
support agricultural activities while continuing to provide other ecosystem
services (Kibblewhite et al. 2008). USDA defines it as "the continued
capacity of soil to function as a vital living ecosystem that sustains plants,
animals, and humans" (USDA 2021). Healthy soils provide habitat, cycle
water and nutrients, support primary production, and sequester carbon
(Lehmann et al. 2020).
There is not yet consensus about a definitive set of indicators to measure
soil health (Rinot et al. 2019) in LCA. Therefore, no quantitative metrics for
soil health were available for this report, and improved soil health is not
included in the quantitative LCA rankings—a limitation of this evaluation.
Instead, this report qualitatively considers the effect that wasted food
pathways have on the following metrics of soil health, as discussed by
Lehmann et al. (2020):
• Provide recycled organic fertilizers and soil amendments.
• Avoid harmful contaminants, pathogens, and pests.
• Enhance water storage.
• Promote good water quality.
• Promote soil biodiversity.
• Sequester carbon (included within GWP indicator in this analysis).
Chapter 3. Life Cycle Assessment
3-3
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3.2 Methodology
Description of Literature
The literature review that serves as the basis for this analysis, returned approximately 3,200 peer-
reviewed journal articles and government and non-governmental organization reports. We reviewed
approximately 250 in depth and extracted LCA-based data from 74. Of those, 47 provided useable data;
data from 23 studies was used in both the inter- and intra-study analyses (in Sections 3.4 and 3.5,
respectively); 10 were used only in the inter-study, and 14 were used only in the intra-study.
This review was able to qualitatively assess all major wasted food pathways; however, data were not
available for each pathway across all the environmental impact categories of interest. Of the considered
wasted food pathways, AD, compost, landfill, and controlled combustion are the best represented in the
reviewed literature (see Figure 3-1). Global warming, eutrophication, ecotoxicity, and acidification are the
impact categories most assessed across the reviewed studies (see Figure 3-2). Although ecotoxicity was
frequently reported, this impact was reported variously as terrestrial, aquatic, marine, and general, using
a variety of impact metrics. This variability prevented standardization of impact results. The same
variability was true for other categories, such as human toxicity. Carbon sequestration and soil health
were noted in some studies that dealt with application of wasted food to land or landfill, but inconsistently
(11 studies included sequestration, whereas 25 did not). Those studies that included soil health had
infrequent and variable qualitative analysis.
Anaerobic Digestion
Composting
Landfill
Controlled Combustion
Animal Feed
Donation
Sewer/WWT H
Source Reduction ¦ <
Land Application | 2
Upcycling I 2
Unharvested / Plowed In | 1
0
70
20 40
Number of Studies
60
80
FIGURE 3-1. DISTRIBUTION OF WASTED FOOD PATHWAYS ASSESSED IN REVIEWED STUDIES
Chapter 3. Life Cycle Assessment
3-4
-------
Eutrophication
86
Global Warming
86
Ecotoxicity
69
Acidification |55
Human ToxicityI 47
Particulate Matter27
Soil Carbon Sequestration24
Energy Demand24
Water Consumption21
Land Occupation 16
0
20
40 60 80
Number of Studies
100
FIGURE 3-2. DISTRIBUTION OF ENVIRONMENTAL INDICATORS ASSESSED IN REVIEWED STUDIES
Each count indicates a single study that addresses the indicator or pathway indicated; single studies may be counted multiple
times, as a study could evaluate multiple pathways, scenarios, and/or impacts. Soil health is not included in Figure 3-2, as no
studies had quantitative data that could be used in inter-study (Section 3.4) or intra-study (Section 3.5) analysis.
Within the framework of LCA, system boundaries refer to the definition of a set of processes that are part
of the system under consideration and the set of modeling choices that are applied to that system. The
diagrams in the previous chapter identify the set of processes that are relevant for each pathway.
However, different studies may choose different system boundaries; therefore, studies differ concerning
relevant aspects of each management pathway. For example, some studies include waste transportation
or modeling of physical infrastructure, while other studies consider these features to be outside the scope
of their analysis. Further, the presence of a process or avoided product in a pathway system diagram
does not imply that any particular process is necessary to adequately treat wasted food or accurately
estimate pathway environmental impact.
Each study also makes specific modeling decisions regarding the performance of the wasted food
pathway for which environmental impacts are being estimated. While the system boundaries of a study
will specify that wasted food is landfilled, modeling assumptions will specify the details of landfill
operation: assumed LFG production, the quantity of energy recovered, methane leakage, and other
parameters.
It is beyond the scope of results in this chapter to distinguish between the types and management of
technologies within a pathway; however, below we provide details on LCA studies reviewed for
transparency and comparison to real-world distribution of types.
"Type," as introduced in Chapter 2, refers to the specific pathway technology used. For example,
composting might use windrow or ASP systems; controlled combustion might involve grate furnaces,
Chapter 3. Life Cycle Assessment 3-5
System Boundaries
Variation within Pathways
-------
spreader stoker furnaces, or other technology. "Scenario" refers to a set of operational and modeling
assumptions used to describe a specific, modeled implementation of a pathway type in a study.
AD: Across the LCA studies reviewed in greater detail, at least 55 include one or more AD
scenarios. The majority of reviewed scenarios (33) model mesophilic digesters, seven model
thermophilic conditions and 22 do not specify the digester temperature regime. Twenty-five
scenarios clearly pertain to co-digestion practices. Among the remaining scenarios, it is often
difficult to determine if wasted food is the sole feedstock. Within the co-digestion scenarios,
wastewater solids are the most common co-digestion feedstock, followed by manure, yard trim
and agro-industrial waste(s).
Composting: Within the reviewed studies, at least 37 composting scenarios were identified.
Thirteen of those scenarios model windrow composting, eight model an in-vessel composting
system, six model aerated static piles, and the remainder model hybrid systems, home systems
or do not specify a composting method. Twenty composting scenarios accounted for carbon
sequestration in soil, typically assuming that 10-15% of applied carbon is sequestered. Thirty-one
scenarios accounted for compost emissions, with two of those not accounting for methane.
Controlled Combustion: Of the 25 reviewed LCA studies with a controlled combustion scenario,
15 scenarios model mass burn combustion facilities, three scenarios model a combustion
process that involves some form of pre-drying and ten scenarios do not specify the details of the
modeled combustion process. Moisture content for wasted food for controlled combustion is
typically between 67-80%, with the majority of studies assuming or sampling wasted food at 70-
75% moisture content. Energy content of wasted food going to controlled combustion was
typically between 2.5 and 8 MJ/kg LHV. Scenarios that generated electricity with waste heat used
heat efficiencies between 15 and 23%. Scenarios that examined wasted food streams with
physical impurities (packaging, yard trim, other parts of OFMSW) typically assumed that the
stream was at least 80% wasted food (Clavreul et al. 2012; Lee et al. 2020).
Landfill: Within the reviewed LCA studies at least 34 landfill scenarios were identified. Twenty-
eight scenarios accounted for gas capture, with varying assumptions about gas capture
efficiency. Typical gas capture efficiencies increased over the lifetime of the landfill, starting at 0-
50% and ending at 85-95%. Scenarios that used a single gas capture efficiency typically
assumed 60-65%.
"Operations" (i.e., an operational practice in use—for example, using a specific set of emission controls or
using/not using bulk waste or refused-derived fuels in controlled combustion) are not considered within
this analysis, other than in the scope criteria for inter-study analysis (Section 3.4) where studies/facilities
that do not include certain key avoided product benefits are excluded.
Modeling Assumptions about Recovered Resources
Avoided Energy
Those management pathways that can recover energy as electricity or heat often receive a significant
credit for that recovery. The benefit of energy production depends on the grid mix displaced - that is,
recovered energy must offset energy production that has a greater environmental impact for a pathway to
receive credit. Depending on modeling assumptions, pathways such as AD and controlled combustion
may be net negative in terms of GWP. However, this does not mean that they are net negative relative to
the original production of food. Secondly, the benefit received is dependent upon the energy source
displaced, and thus is specific to location and time. For example, Slorach et al. (2019a) conducted an
analysis of wasted food pathways that recover energy (AD, controlled combustion and landfilling). They
found that the avoided energy credits assigned to each pathway had a direct influence on most impact
categories including energy demand, GWP, toxicity, eutrophication, and water consumption. That
analysis also considered the effect of substituting other energy sources, rather than the current grid mix
(in the UK), finding that if the displaced energy is wind or solar, then AD and controlled combustion switch
from being net sinks to net sources (i.e., net negative to net positive) of GWP. The study noted that
benefits of wasted food pathways are "highly dependent on system credits" (Slorach et al. 2019a).
While a considerable quantity of heat can be recovered in addition to the electricity produced, many
studies exclude an environmental credit or include only a partial credit as heat is used to operate
treatment processes and no uses are typically available for excess heat. Avoided energy benefits are
Chapter 3. Life Cycle Assessment
3-6
-------
realized based on net energy production, which constitutes total energy production less energy demand
required to operate wasted food treatment systems and associated processes. Due to the mix of input
data, modeled data, and assumptions in the reviewed LCAs, absolute energy production varies from
study to study. High-level trends from the reviewed studies are summarized below.
Anaerobic Digestion: Most reviewed LCA study scenarios (59 of 64) of AD assess a benefit for avoided
electricity production. Twenty-six scenarios include a credit for avoided heat production. Eight scenarios
model the production of biofuel from biogas. Across a subset of reviewed studies for which electricity
recovery numbers were reported, gross electricity production per metric ton of wasted food processed is
between 100 and 420 kWh (Parry and WERF 2012; Yoshida et al. 2012).
Landfill: Across 34 reviewed landfill study scenarios, 25 specify that they include avoided electricity
production benefits. The quantity of electricity generated from landfill gas per metric ton of wasted food
landfilled varies between 34 and 224 kWh (Parry and WERF 2012; Huang et al. 2022).
Controlled Combustion: Across 25 reviewed controlled combustion scenarios, 22 specify that they include
avoided electricity production and 14 include avoided heat production. The quantity of electricity
generated from combusting one metric ton of wasted food varies between 138 and 564 kWh (Mondello et
al. 2017; Hoehn et al. 2021).
Avoided Products
The quantity of avoided product (i.e., food, animal feed, fertilizer or peat) assumed to generate
environmental credits for a given pathway can vary depending on a variety of characteristics. For
example, the protein content of specific wasted food feedstocks determines the quantity of feed avoided
by the animal feed pathway.
How avoided products are used, and whether modeling accurately reflects their use, is critical to
understanding the environmental performance of each pathway. While soil amendments can offset
fertilizer, if compost, digestate, or biosolids are disposed of or used as a landscaping mulch, then claiming
an avoided fertilizer benefit may not be appropriate (if the landscape plants would not have otherwise
received fertilizer). The context of avoided product use is a factor in determining the magnitude and
validity of avoided product credits.
Wthin the reviewed LCA literature, the majority of studies assume that AD digestate or biosolids are land
applied. Among the seventy reviewed study scenarios that model AD, six assume that digestate is
incinerated and one assumes that it is landfilled. Nine scenarios did not include digestate management,
declaring it out-of-scope. All reviewed studies assume that compost is land applied and all but one study
applies an avoided fertilizer production benefit to the assessment of net environmental impacts. Avoiding
the use of peat soil amendments is assessed infrequently within the literature.
Directly land-applied wasted food, unharvested/plowed in crops, digestate, biosolids, and compost are
different with respect to nutrient content, organic matter content, nutrient release, and other factors.
However, the reviewed LCA studies reflect a simplified approach to assigning benefits related to
application of these outputs to soil. For instance, throughout the literature, similar ratios are often used for
both compost and digestate offsetting synthetic fertilizer production and use and typically fall in the range
of 20-50% for nitrogen and 95-100% for potassium and phosphorus (Yoshida et al. 2012). The range for
N fertilizer reflects how substitution ratios are intended to reflect plant availability of nutrients in compost
or digestate (Levis and Barlaz 2011). Wth higher readily available nitrogen content, digestate is more
commonly viewed as a fertilizer, especially in liquid or slurry form, and therefore may be better suited as a
substitute for synthetic N fertilizer, which is immediately available to plants. While the total nitrogen
content in compost is typically higher than that of digestate, its readily available nitrogen is lower
(Stehouwer et al. 2022). Compost will provide less nitrogen in the first year but more nitrogen over a
longer time frame than digestate. Soil amendments produced by other pathways (e.g., biosolids,
unharvested/plowed-in crops) can also offset fertilizer use, but these pathways are assessed infrequently
in the literature. For all wasted food-derived soil amendments, assumptions about quantity, bioavailability,
and loss of nutrients determine the quantity of synthetic fertilizer that is avoided, and credits from fertilizer
production and use are calculated inconsistently. Different fertilizer substitution ratios may be applied
across or within studies. Given the high-level analysis of LCAs, one should not expect LCA to accurately
Chapter 3. Life Cycle Assessment
3-7
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capture the specificities of any particular wasted food processing operation, especially with respect to soil
health and nutrients.
As an alternative to or in addition to fertilizer replacement, a small number of studies look at using
digestate or compost to substitute the use of peat growing media. Compost is assumed to displace peat
use 1:1 on a volume basis (Levis and Barlaz 2011). Studies assumed that the GWP benefits of avoiding
peat use were similar to (Morris et al. 2017) or greater than avoided fertilizer benefits (Levis and Barlaz
2011).
Additionally, wasted food content varies in each material, depending on co-feedstocks. Studies report a
range of effects on soils and crops and a variety of environmental impacts. A consistent framework is not
applied when assessing the benefit/impact of wasted food-derived nutrients as compared to synthetic
fertilizers in LCA research. The reviewed studies vary widely in their approaches when it comes to
estimating carbon sequestration and emissions to air and water resulting from land application of
compost, digestate, biosolids, or wasted food. These factors make the relative benefits and impacts of
land application of these materials difficult to quantify according to any standardized, comparable metrics.
Therefore, qualitative analysis of the agronomic and environmental benefits and impacts of land-applied
wasted food-derived materials is provided in Section 3.6 and Chapter 4. The research gaps section
highlights the need for further studies to better understand the behavior of raw wasted food,
unharvested/plowed in crops, digestate, biosolids, and compost when land applied.
Modeling Assumptions about Soil
A meta-analysis of N2O emission from land application of amendments suggests a generic value 40%
lower than IPCC's emission factor, and highlights the importance the C:N ratio of the amendment, the soil
characteristics (texture, drainage, organic C and N), and precipitation (Charles et al. 2017). N2O and other
emissions from land-applied material (digestate, compost, biosolids) is an important component of the
relevant pathways' GWP and other impacts. Section 3.6 addresses soil amendments and soil health, and
we note that there is rich literature describing these systems (e.g., Charles et al. 2017),
Carbon storage potential is influenced by site history, soil type, management practice and land use.
Carbon sequestration rates are also impacted by existing levels of soil organic carbon (SOC), with
targeted application on previously disturbed or degraded soil resulting in higher levels of net carbon
storage (Peltre et al. 2012; Brown and Beecher2019). The type and composition of organic matter
applied to agricultural fields also has a demonstrable impact on SOC storage, and existing SOC affects
rates of change (higher initial SOC results in slower SOC gains) (Poulton et al. 2018). Finally, we note
that SOC accumulation can be augmented, decreased, or even reversed if management practices are
changed(e.g. no-till practices are adopted; soil is left bare/unplanted) (Poulton et al. 2018). Studies
assume long-term, if not permanent, changes to soil management practices. The impacts of specific soil
management practices, soil types, and land uses on carbon storage potential and GHG emissions is
beyond the scope of this report.
Chapter 3. Life Cycle Assessment 3-8
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3.3 Qualitative Summary of Pathway Environmental
Impacts and Benefits
Table 3-2 summarizes the key drivers of environmental impact and benefit (including credits for avoided
energy and products) from each wasted food pathway.
In reviewed LCAs, not all impacts and benefits are covered in each study (Figure 3-1 and Figure 3-2). As
noted in the previous section, most LCAs reviewed quantified benefits for avoided electricity production
where appropriate; some also included avoided heat or fuel production. LCAs also credited pathways for
avoided production of food, animal feed, fertilizer, or peat and the sequestration of carbon; however,
these credits were not consistently applied.
TABLE 3-2. SUMMARY OF ENVIRONMENTAL IMPACTS AND BENEFITS, BY PATHWAY
Pathway
Environmental Impacts
Environmental Benefits
Energy use is a source of environmental impact for all pathways, except source reduction, and is
not listed separately by pathway.
-0-
Source Reduction
-
Avoided Food Production
Donation
GWP: Distribution and storage
Avoided Food Production
/
L^
~1
Upcycling
Water consumption: Food
processing
Avoided Food Production
Anaerobic
Digestion
GWP: CH4 from biogas leakage
Eutrophication: WRRF effluent
release (from recirculating
dewatering liquid)**; land
application of digestate or
biosolids
PM formation, Acidification:
Biogas combustion
Avoided Energy Production
Avoided Fertilizer Production/Use*
Avoided Peat Harvest*
Carbon Sequestration*
Soil Health*
Animal Feed
GWP and Eutrophication: Feed
processing
Avoided Feed Production
Composting
GWP: CH4 and N2O emissions
Acidification, Eutrophication,
PM formation: NH3 emissions
Eutrophication: land application
of compost
Avoided Fertilizer Production/Use
Avoided Peat Harvest
Carbon Sequestration
Soil Health
¦
Controlled
Combustion
Toxicity: flue gas (Hg, dioxin)
PM formation: Flue gas
Avoided Energy Production
Chapter 3. Life Cycle Assessment
3-9
-------
Pathway
Environmental Impacts
Environmental Benefits
Land Application
Eutrophication: land application
of wasted food
Avoided Fertilizer Production/Use
Carbon Sequestration
Soil Health
Landfill
GWP: CH4 from anaerobic
decay of food
Toxicity and Eutrophication:
Untreated landfill leachate
PM formation, Acidification:
Landfill gas combustion
Avoided Energy Production
Carbon Sequestration
||j
Sewer/WWT
GWP: CH4 from anaerobic
decay of food in sewer and
from WWT processes
Eutrophication: WRRF effluent
release; land application of
biosolids
Avoided Energy Production**
Avoided Fertilizer Production/Use*
Avoided Peat Harvest*
Carbon Sequestration*
Soil Health*
Unharvested/
Plowed in
Avoided Fertilizer Production/Use
Carbon Sequestration
Soil Health
b
7
7
3
7
m
*Appropriate only if digestate or biosolids beneficially used
**lf AD at WRRF
Emissions from application of wasted food-derived soil amendments not included above because presumed to be
lower than those related to synthetic fertilizers.
"minimal environmental impacts expected compared to magnitude of pathway environment benefits.
Chapter 3. Life Cycle Assessment 3-10
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3.4 Quantitative Comparison of Pathways Across
Studies
The following two sections (3.4 and 3.5) present results and discussion related to the environmental
indicators described in Table 3-1. Section 3.4 compares wasted food pathways across studies (inter-
study) and Section 3.5 compares environmental performance of wasted food pathways within individual
studies (intra-study). The two approaches complement one another. The benefit of the inter-study
analysis is that it facilitates a wide range of comparisons and provides a high-level comparison of all
pathways regardless of study considerations. The benefit of the intra-study analysis is that comparisons
are made using consistent scope and modeling.
This section compares wasted food pathways across studies (inter-study) for six impact categories -
GWP, energy demand, acidification, eutrophication, water consumption, and land occupation - based on
their median environmental impact relative to that of other pathways.
While the methods for assessing certain impacts are well established (GHG emissions), others are
nascent (soil health). The latter is a limitation of LCA, discussed further throughout the text. The six
environmental indicators presented quantitatively (both in graphics and in tables) in this section were
chosen from the 11 described in Section 3.1 based upon two factors. First, they are commonly assessed
in LCA studies, and second, when assessed, they are reported in consistent impact units, allowing for
comparison (possibly after conversion). The remaining impact categories that are not quantitatively
analyzed in this section did not meet these criteria, preventing meaningful comparison of results across
studies. For example, particulate matter formation was not consistently reported across the reviewed
studies, and human and ecotoxicity were reported in a variety of metrics. However, particulate matter and
toxicity (human and eco) are examined in the intra-study rankings. Only soil health could not be examined
quantitatively in either section. It is not yet possible to quantitatively address soil health in LCA but given
the importance of soil health for food production and the fact that much wasted food can make its way
back to the soil, we have included this as an environmental indicator, nonetheless. Further discussion of
soil health can be found in Section 3.6.
Methodology for Inter-Study Analysis
Scope Criteria
A limited set of scope criteria, defined in Table 3-3, were applied to enhance comparability of impact data
used in Section 3.4. Thirty-four of the LCA studies evaluated met the scope criteria and were included in
the quantitative analysis in this section. Of those thirty-four, twenty-three were also used in the intra-study
analysis, described below. As a rule, data from studies that met scope criteria were included. The only
exceptions to this inclusion were cases in which impact results exceeded the range of realistic values,
based on professional judgment, and for which a sufficient justification/explanation was not identified in
the original reference.
Chapter 3. Life Cycle Assessment
3-11
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TABLE 3-3. INTER-STUDY ANALYSIS (SECTION 3.4) SCOPE CRITERIA
All
Studies must not include an environmental credit for avoided disposal (e.g.,
AD is not credited for avoiding landfill).
Studies must calculate impacts beginning at the point wasted food arrives
at pathway through final disposal or beneficial use. (Studies may also
include impacts of transportation to pathway.)
AD
Studies must include environmental credits for avoided energy and fertilizer
production.
Animal Feed
Studies must include environmental credits for avoided animal feed
production.
Compost
Studies must include environmental credits for avoided fertilizer production.
Controlled Combustion
Studies must include environmental credits for avoided energy production.
Landfill
Studies must include environmental credits for avoided energy production.
Other Pathways
No additional scope criteria applied due to presence of limited study data.
Studies may model electricity or heat (or both) in order to meet the criteria for including avoided energy.
Carbon sequestration was not applied as a scope criterion, but further analysis of results with and without carbon
sequestration credits is presented in Table 3-4.
For commonly assessed management pathways, only study results that modeled systems with certain
operational practices and included certain avoided products were chosen for comparison in this section,
per the criteria shown in Table 3-3. For example, data on controlled combustion were not used if they
came from studies that did not include credit for avoided energy production (because it was either not
modeled or not implemented). Also, data on AD where digestate or biosolids were disposed were not
included. Study data were excluded for all pathways if their calculation of net impact included an
environmental credit for avoided disposal, since this would lead to double counting in a direct comparison
of impacts of alternate pathways. In general, the majority of the identified studies met these criteria for
avoided products - identifying avoided products is common practice in LCA.
As only a few studies included estimates of carbon sequestration associated with each management
pathway, this characteristic was not applied as a scope criterion, as it would have further limited the
number of studies providing data. An analysis comparing results of studies with and without carbon
sequestration is included in the analysis in Table 3-4.
Impact data were screened for outlier data and the studies providing these data were given additional
review to ensure that modeling choices align with criteria in and are representative of the wasted food
pathways as described in Chapter 2. Beyond the criteria described here, results have not been
standardized in terms of scope or other boundary assumptions (e.g., one study may include
transportation and another not). Because they involve studies with different scopes and different impact
methods, these results provide a broad perspective on the performance of wasted food pathways.
Data Presentation
In the following sections, Figure 3-3 to Figure 3-8 present detailed impact results for the wasted food
pathways across a variety of impact categories. These figures show all median values on a single axis.
Median impact results are presented per metric ton of wasted food processed in the noted units for each
impact category. Often, medians for source reduction and donation are significantly different than the
other pathways. Therefore, the figures also have insets to show distributions of the data (as box plots) for
the other pathways. The bottom and top of each box represent the first and third quartiles (covering 50%
Chapter 3. Life Cycle Assessment
3-12
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of the data); median values are shown with a dark line between the quartiles, and the whiskers represent
1.5 times the interquartile range (25th-75th percentile). The discussion of the data underlying the boxplots
refers to individual study results. While individual study results are not shown in the boxplots, the data
underlying these figures can be found in Appendix D.
In the graphics in this section, the number of data points is indicated with the name of the wasted food
management pathway. Some studies report multiple results for scenarios, resulting in multiple data points
per study. Sometimes these scenarios yield identical results; in these cases, only one data point has
been used for that management pathway in that study. Therefore, the number of data points is always
greater than or equal to the number of studies for that pathway.
Graphics and tables present results with a standardized functional unit of 1 metric ton of wasted food (wet
basis). The moisture content of considered wasted food is not standardized across studies. The graphics
and tables include studies with variations in the type of wasted food considered (e.g., food processing
waste versus plate waste). Where a functional unit included a co-waste (e.g., wasted food and yard trim),
the study scenario was only included if wasted food was the dominant (>50%) waste material being
processed and if the co-waste was also organic. The approach to comparing disparate impact units is
described in detail in Appendix C.
These data allow for high-level comparisons among pathways, as designed. However, the data were not
intended to allow for rigorous statistical analysis - there are not enough data points to arrive at
meaningful confidence intervals. Therefore, in the results that follow, median values and ranges are the
main descriptors used.
For resource recovery or avoided products, modeling assumptions can influence a variety of
environmental impacts (e.g., if a wasted food pathway recovers energy that leads to avoided electricity
production, that avoided electricity will reduce GWP, energy demand, and acidification impacts). Given
the influence of resource recovery and avoided products on impacts beyond GWP, observations in the
Global Warming Potential section often apply to the other sections but are not repeated in those sections.
For example, a high-efficiency biogas capture from AD will lead to a reduced impact for energy demand
(directly) and for acidification and eutrophication (indirectly, as energy from the AD may offset NOx
emissions from grid energy sources).
Table 3-4 and Table 3-5 present summary environmental impact results for the wasted food pathways.
Chapter 3. Life Cycle Assessment 3-13
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Global Warming Potential
Multiple factors impact the GWP of wasted food pathways, including:
Anaerobic decay of wasted food (fugitive ChU from sewer/WWT and landfill).
Avoided food and animal feed production (CO2, CH4, N2O savings from source reduction,
donation, upcycling and animal feed).
Avoided energy production (CO2 savings from AD, controlled combustion, and landfill).
Wasted food management process emissions (CH4 leakage in AD and ChU and N2O from
composting).
Energy use (CO2 from all pathways except source reduction).
Carbon sequestration (composting, landfill, land application and unharvested/plowed in, plus AD
and sewer/WWT if soil amendments are beneficially used).
Nitrous oxide emissions from land application of wasted food or wasted food-derived soil
amendments (composting, land application and unharvested/plowed in, plus AD and sewer/WWT
if soil amendments are beneficially used).
Avoided synthetic fertilizer production and use (CO2 and N2O from composting, land application
and unharvested/plowed in, plus AD and sewer/WWT if soil amendments are beneficially used in
ways that reduce application of synthetic fertilizer).
Avoided peat harvest.
Emissions associated with landfill or controlled combustion of waste outputs (in AD and
sewer/WWT pathways if soil amendments are disposed of rather than beneficially used. Note this
was not modelled in reviewed studies of AD since land application of digestate/biosolids was
assumed.
Not all these drivers are included in all LCA studies from which data were extracted. See Table 3-3 for
scope criteria for inclusion within this analysis.
Figure 3-3 shows GWP impact values for the wasted food pathways. Pathways may achieve net negative
values through avoided production of a resource, whether it is food, animal feed, energy, or fertilizer,
possibly coupled with the sequestration of carbon in soil. Release of carbon dioxide from wasted food
itself is treated as net neutral due to the biogenic (non-fossil) origin of the carbon.
In Figure 3-3 (and all boxplots in subsequent sections) the bottom and top of the boxes represent the first
and third quartiles (25th - 75th percentile, covering 50% of the data), the line within the shaded box
represents the median value, and the whiskers represent 1.5 times the interquartile range (25th-75th
percentile). All data points meet basic scope criteria for each pathway (see Table 3-3), such as
application of GHG credits for avoided products and energy, as defined in Table 3-3. Carbon
sequestration is not consistently included for some pathways. Numbers in parentheses next to pathway
names indicate the number of study scenarios included.
Chapter 3. Life Cycle Assessment 3-14
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Global Warming Potential (kg C02eq/metric ton FLW)
FIGURE 3-3. COMPARISON OF GLOBAL WARMING POTENTIAL
OF WASTED FOOD PATHWAYS ACROSS LCA STUDIES
AD data assumes land application of digestate or biosolids. Sewer/WWT studies varied in assumptions about biosolids'
destination. Carbon sequestration not consistently assumed for some pathways. See Table 3-4 for details. Donation excluded
from boxplot because the range extends an order of magnitude below the next lowest value in the boxplot.
See Appendix Table D-1 for data and sources.
The GWP analysis shows that source reduction had order-of-magnitude greater GHG benefits than any
other pathway. Sewer/WWT and landfills tend to have the highest GWP values. Among other pathways,
donation, upcycling, animal feed and AD have the largest potential for beneficial performance. But the
interquartile ranges suggest the potential for similar impacts among the AD and animal feed pathways
and the compost, controlled combustion, and land application pathways.
Among the pathways in the inset boxplot, values for GWP can be split into two groups describing broad
pathway performance.
Negative (beneficial) medians and medians close to zero:
o Source reduction has order-of-magnitude greater GWP than other pathways.
o Donation and upcycling avoid production of food, avoiding substantial GHG emissions, but
also use energy for transportation and, in the case of upcycling, food processing, offsetting
some GHG savings.
o Animal feed values are almost entirely negative, as the energy needed to collect, clean, and
process wasted food tends to be less than that needed to produce and process feed crops.
o For AD, negative values are achieved in systems with high biogas capture and displacement
of carbon-intensive energy. All included AD studies assume land application of digestate or
Chapter 3. Life Cycle Assessment
3-15
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biosolids, thus assigning GHG credits for avoided fertilizer manufacture and use, and not
assigning GHG emissions related to landfill or controlled combustion of digestate or biosolids.
o Composting values vary as a function of different operational characteristics and assumptions
about fugitive emissions, the degree to which studies assume fertilizer and peat are offset,
and whether carbon sequestration credits were applied. Table 3-4 shows inclusion of carbon
sequestration can shift values from positive to negative.
o Controlled combustion varies widely, with energy recovery efficiency as a key parameter.
o Land application values, all from ReFED (2023), are all positive, reflecting assumptions about
fugitive methane and nitrous oxide (N2O) emissions.
o Unharvested/plowed in has a single positive value, with limited documentation (ReFED
2023).
Positive values, with median value above zero:
o For sewer/WWT, WRRFs do not capture methane produced in sewers and have process
emissions of nitrous oxide; these releases offset credits from (potentially) recovered
resources, such as energy (if AD present) and nutrients (in biosolids). Table 3-4 shows that
carbon sequestration from land-applied biosolids is assumed in two studies; these two have a
lower median than the five data points without sequestration but remain positive.
o Landfills capture a portion of the methane produced, which reduces their net GWP impact,
but capture rates are not adequate to offset overall impacts.
For most pathways, there is a range of values, sometimes spanning positive and negative, that reflects
modeling choices or system operation.
For example, for animal feed, the lowest value (-420 kg CCheq) is for a wasted food process that
represents bioconversion of wasted food into animal feed using black soldier fly larvae. The process
receives a large credit for avoided soy and fishmeal production, as well as a credit for compost utilization
(Mondello et al. 2017). The next lowest values (-385 and -329 kg CCheq) are associated with a
specialized protein concentrated animal feed (Albizzati et al. 2021 b). The largest credit for this system is
associated with avoided land use change attributed to avoided feed production. (Land use change
impacts are a key consideration associated with agricultural products, though they are often excluded
from the system boundaries of LCA studies.)
For AD, the lowest values assume avoided electricity and heat production of Danish coal-based power,
so the GWP benefit of this biogas-produced energy is higher than it would be with a lower-carbon power
mix (Khoshnevisan et al. 2018). In contrast, the highest AD value reflects an assumption of relatively high
emissions from land application of digestate (Albizzati et al. 2021 b). Other positive AD values are
generally due to scope or operational assumptions. For example, an AD impact of 27 kg CCheq is
calculated from a study that includes composting of digestate (Al-Rumaihi et al. 2020) and values of 8 to
26 kg CCheq from Pace et al. (2018) are calculated with assumptions of relatively low electrical
generation efficiency.
For controlled combustion, values above the median are associated with wasted food that has a very low
heating value and a system with relatively low energy recovery efficiency; for example, 235 kg CCheq
(Ahamed et al. 2016).
The sewer/WWT and landfill pathways have positive median values. These two pathways include
appreciable methane production, with either uncontrolled or limited capture. Consistent with the scope
criteria in Table 3-3, data points pertaining to landfills without gas capture or energy recovery have been
excluded from this analysis, given that over 90% of U.S. landfilled waste was disposed of in a facility with
an active LFG collection system in 2021, and 65% of LFG is sent for energy recovery (U.S. EPA 2022a).
For landfills, the highest data point is from a study that includes gas capture but assumes low capture
rates, demonstrating the impact of landfill operation: with an assumption of 35% gas capture in the first
five years of operation and 52% over landfill life, the GWP of landfilling is 2,400 kg CCheq/metric ton
wasted food (Albizzati et al. 2021b). Other LCA study values for landfilling are <1,000 kg C02eq/metric
ton wasted food, which is lower than an estimate from the EPA LandGEM model59. LandGEM estimates
Chapter 3. Life Cycle Assessment
3-16
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54 kg methane emitted per metric ton wasted food for landfills with gas collection. Applying GWPs from
the Intergovernmental Panel on Climate Change's Fifth Assessment Report (Myhre et al. 2013), this
emission corresponds to 1,500 kg CCheq/metric ton wasted food for a 100 year time horizon and 4,500 kg
CCheq over a 20-year time horizon. (Note that these LandGEM estimates do not account for carbon
dioxide emissions from landfilling or for energy offset by captured methane, unlike LCA studies
considered in this report.)
Carbon Sequestration
Increasing storage of SOC is an important approach to GHG mitigation, as the amount of carbon stored in
soils exceeds that in the atmosphere and in living biomass (Ciais et al. 2013). In the context of this report,
carbon sequestration refers to the storage of wasted food carbon in the subsurface (e.g., over a period of
100 years). Wasted food carbon reaches the subsurface through the application of wasted food,
digestate, biosolids, and compost to land or the burying of wasted food in a landfill. Addition of carbon-
rich amendments and resulting increased SOC can improve soil health by increasing water infiltration
rates and retention, reducing bulk density, and reducing risk of losses from erosion by improving soil
aggregate stability (Brown et al. 2020). Any increase in SOC results in outsized improvements in soil
functioning and quality (Poulton et al. 2018). Many studies quantified carbon sequestration within the
GWP indicator, but including sequestration was not consistent across all studies. Those studies that do
include carbon sequestration have included a benefit (negative GWP) for this sequestration. Across those
pathways that deal with carbon sequestration, the presence or absence of sequestration is the one
categorical variable that was used (i.e., it was not used as a scope criteria).
Table 3-4 shows the median and ranges of GWP values, with and without carbon sequestration, for
wasted food pathways where sequestration is possible. There is significant overlap in these values,
indicating that the inclusion or exclusion of sequestration has a moderate effect on overall GWP
estimates that is in line with other aspects of management and operational performance.
Across pathways with data for both conditions, impacts with sequestration are lower than results without
carbon sequestration (see also Appendix B-1-1). For AD and compost, the shift is on the order of tens of
kg C02eq / metric ton wasted food. For sewer/WWT, the shift is on the order of hundreds of kg C02eq /
metric ton wasted food. The median offset for composting is larger than for AD. Given the higher median
impact of the composting pathway, sequestration is potentially more consequential to the net GWP of this
pathway relative to AD: the inclusion of carbon sequestration could switch the net impact of composting
from positive (net source) to negative (net sink).
Wthin a given study, including carbon sequestration should lead to a net reduction in GWP. In the
aggregate, it appears that models that include carbon sequestration show net reductions in GWP relative
to those without. However, this is not the case for the landfill pathway, indicating the limited dataset size
(only four data points without sequestration) and the complexity of modeling landfills in particular. The
scale of the effect can range from minor to major in relation to net impact (for AD and compost, on the
order of tens of kg C02eq / metric ton wasted food). The shifts in median impact represented in Table 3-4
constitute major shifts (>30% change) in net impact (relative to values including sequestration) for the
composting and sewer/WWT pathways and a moderate shift for AD. Minor effects on impact (<10%) are
also possible depending on specific assumptions. However, the inclusion or exclusion of carbon
sequestration is unlikely to affect the relative ranking of pathways when applied consistently across
pathways.
More information on carbon sequestration can be found in Section 4.6.
Chapter 3. Life Cycle Assessment
3-17
-------
TABLE 3-4. GWP IMPACTS, WITH AND WITHOUT CARBON SEQUESTRATION,
PER METRIC TON WASTED FOOD
With Sequestration
Without Sequestration
Pathways
Median
Range
(25 to 75 pctile)
Data
points
Median
Range
(25 to 75 pctile)
Data
points
AD
-120
-160 to -41
12
-97
-260 to -30
36
Composting
26
-66 to 55
20
100
67 to 150
6
Land App.
-
n.a.
0
23
22 to 25
5
Landfill
510
190 to 700
11
460
280 to 1000
4
Sewer / WWT
190
140 to 230
2
490
470 to 490
5
Unharvest
-
n.a.
0
47
n.a.
1
AD data assumes land application of digestate or biosolids. Not all sewer/WWT scenarios assume land application of
biosolids.
Chapter 3. Life Cycle Assessment 3-18
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Energy Demand
The energy demand indicator reflects net energy use associated with a wasted food pathway, and should
account for:
Energy use by the pathway, including processing of the wasted food.
Avoided energy use due to energy generation from wasted food by the pathway; and
Avoided energy use through avoided production of food, feed or synthetic fertilizer.
In some respects, energy demand parallels GWP: where systems require or produce energy, both energy
demand and GWP reflect this (the latter being a function of energy grid). However, the two have an
important difference: fugitive losses of methane and nitrous oxide do not factor into energy demand, so
pathways with higher losses of these gases may perform more favorably with respect to energy demand.
Therefore, energy demand provides an additional perspective on each wasted food pathway's
performance. Figure 3-4 displays the energy demand (also referred to as energy use) reported for the
wasted food pathways across the reviewed studies.
Energy Demand (MJ/metric ton FLW)
Source
Reduction (2)
-30,000
-25,000
4,000
2,000
-2,000
-6,000
-8,000
-10,000
-12,000
Anaerobic Composting Controlled
Digestion Combustion/
Incineration
Landfill
Upcycle
Donation (2)
-20,000
Controlled Combustion/
Incineration (5)
XF
Landfill (3)
Anaerobic Digestion (14)
Upcycle (1)
Composting (6)
15,000
-10,000
-5,000
5,000
FIGURE 3-4. COMPARISON OF ENERGY DEMAND
OF WASTED FOOD PATHWAYS ACROSS LCA STUDIES
AD data assumes land application of digestate or biosolids. See Appendix Table D-1 for data and sources.
Chapter 3. Life Cycle Assessment
3-19
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Data on energy demand were limited. Overall, the energy demand analysis shows that source reduction,
donation and upcycling have the greatest potential for beneficial performance due to energy use savings
from avoided food production. No data for animal feed
was available from reviewed studies that met scope
criteria, but this pathway similarly saves energy
through avoided feed production.
Beyond these pathways, the data show AD has the
greatest potential for beneficial performance due to its
energy generation and potential to displace the
manufacture and use of synthetic fertilizer. Controlled
combustion also demonstrates negative (beneficial)
median for energy demand, although data range from
negative to positive. Composting and landfilling are the
poorest-performing pathways for which data were
available, in terms of medians, but controlled
combustion's range does extend above that of either
pathway, possibly due to high moisture and poor
energy value qualities of food as feedstock for
controlled combustion. Composting (and other
pathways, such as animal feed, for which data were
not available) do not typically attempt to capture
energy; although landfills do recover some energy,
their conversion and capture rates are not as efficient
as AD or controlled combustion at harvesting energy
from wasted food.
The range of values shown for AD, controlled combustion, and landfill in Figure 3-4 is driven by some of
the modeling variations discussed in the previous section for GWP. While all energy demand estimates
are negative for the AD pathway, the spread of energy demand results is attributable to variability in
assumptions related to energy recovery and energy demand of the AD unit and associated processes
(e.g., wasted food pre-processing and biogas upgrading). Studies assuming both avoided electricity and
heat production have the lowest net energy demand. These data underscore the importance of operation
and management of wasted food pathways that recover resources; these can lead to large variations in
environmental performance.
Energy Consumption in Composting
The composting pathway can have a wide
range of energy consumption depending on
the composting method as well as size and
complexity of operation. Energy
consumption can vary between about 200-
600 MJ/metricton FW for windrow systems
compared to 150-550 for aerated static
piles.3 Energy intensities vary with the
amount of contaminants in the wasted food
feedstock as well. See Section 2.13 for
more information on how wasted food
contaminants affect the composting
pathway.
a (Komilis and Ham 2004; Pergola et al.
2018; Morelli et al. 2019)
Chapter 3. Life Cycle Assessment 3-20
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Composting has net positive energy demand, as the energy needed to aerate compost is not offset by
avoided energy for fertilizer production (and carbon sequestration benefits are not relevant for energy
demand). Several combustion studies show net negative energy demand, but the positive data point for
combustion is due to a large estimate of electricity consumption for controlled combustion and a relatively
small estimate of energy recovery, which also resulted in high GWP values (Ahamed et al. 2016).
Key Energy Recovery Distinctions between
Controlled Combustion and Anaerobic Digestion of Wasted Food
While some energy recovery cases and characteristics of AD, controlled combustion, and landfilling
of wasted food are similar, the processes are quite different. Below are some additional features of
these technologies:
Incineration generally produces more gaseous pollutants, when compared to the other pathways, and
can even volatilize metals (Psomopoulos 2009). Incineration of wasted food streams is flexible
though, with the process being able to accept physical contaminants, particularly combustible items
such as paper plates and plastic packaging. Both heat and electricity can be generated, though
electricity is more commonly produced in waste-to-energy facilities. Wasted food incineration can also
be combined with OFMSW treatment, which generally improves energy recovery as wasted food has
higher-than-average moisture content for OFMSW (Pham et al. 2015). Energy production from
incineration is mostly affected by LHV of the feed (typically 2.5-8 MJ/kg) and recovery efficiency
(typically 15-23% heat produced is recovered as electricity).
Anaerobic digestion is a wet biological process. Unlike incineration, its performance is not negatively
affected by the high moisture content of foods but can be affected by contaminants found in wasted
food (both physical and chemical). While heat is not a main product of AD systems, it can produce
biogas to be used for heat or electricity generation, in a similar way to landfills that have gas capture
systems. The loading rates for AD can vary, but 1-10 kg solids/m3 is typical for wet AD (Pham et al.
2015). Dry AD can have higher loading rates, up to a maximum of 30% solids, but has higher
operational complexity (Wang et al. 2023). Energy production in AD is affected by the solid loading
rate, biogas yield, and methane concentration in the biogas. If a combined heat and power (CHP)
system is being used onsite, then the overall efficiency of that system will influence energy recovery
as well. Reviewed studies examined CHP systems with a range of overall efficiencies from 70-90%.
Landfills that capture biogas can use the same CHP technology as AD.
Chapter 3. Life Cycle Assessment 3-21
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Acidification
A variety of processes can contribute to acidification in the wasted food pathways, though typical drivers
are emissions of NOx and SOx from combustion or the emission of Nhb from biological processes. While
avoided production of feed and fertilizer can lead to acidification credits, the application of compost or
digestate to land may offset those credits if the study includes air emissions from the applied material.
However, emissions from wasted food-derived amendments tend to be lower than those from synthetic
fertilizers if appropriate agronomic practices are followed. Section 4.6 provides further discussion. Figure
3-5 shows terrestrial acidification impact.
Acidification (kg SO eq/metric ton FLW)
14
12
10
Anaerobic Animal Feed Composting Controlled
Digestion Combustion/
Incineration
Landfill
Upcycle
NF
Controlled
Combustion/
Anaerobic Digestion (18) Incineration (11)
-60
Donation (1)
-50
Source
Reduction (1)
-40
Upcycle (2)
Animal Feed (1)
-30
-20
-10
Landfill (5)
Composting (8)
10
FIGURE 3-5. COMPARISON OF TERRESTRIAL ACIDIFICATION POTENTIAL
OF WASTED FOOD PATHWAYS ACROSS LCA STUDIES
AD data assumes land application of digestate or biosolids. See Appendix Table D-1 for data and sources.
For acidification, source reduction and donation out-perform the other pathways by an order of magnitude
due to avoided energy use during food production. Among the pathways in the inset boxplot animal feed
and upcycling have the most favorable performance. Landfill, compost, AD and combustion perform
worse—but the latter two have the potential for beneficial performance. Pathways with energy recovery
(especially AD and controlled combustion) can result in offsets of other energy production, resulting in
acidification credits through avoided criteria air pollutant emissions. There are three broad groups in the
collected data:
Negative (beneficial) medians:
o Animal feed modeling that takes credit for avoiding the production of energy-intensive (and
thus NOx- and SOx-intensive) production of feed crops.
o Upcycling, which receives credit for avoided production of food crops.
A mix of positive and negative values, with median value close to zero:
Chapter 3. Life Cycle Assessment
3-22
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o AD and controlled combustion recover energy; the net impact of each pathway depends on
the avoided grid mix and how it compares to direct air emissions associated with biogas and
wasted food combustion, respectively.
Positive values, with median above zero:
o Although composting can lead to avoided fertilizer production, ammonia may off-gas during
operation.
o Landfill values reflect the balance between avoided energy and electricity and diesel
emissions required for processing wasted food.
As with the other impact categories, inspection of data points indicates that modeling assumptions tend to
drive high and low values. For example, avoided production of urea and soy meal in animal feed accounts
for estimated impact of-1.28 kg SCheq (Mondello et al. 2017). Likewise, the lowest AD data point (-0.6 kg
SCheq) is based on favorable assumptions about avoided heat, electricity, and fertilizer offsets (Mondello
et al. 2017). At the other end of the spectrum, the high composting values, 1.2 kg SCbeq (Morelli et al.
2019) and 1.4 kg SCheq (Oldfield etal. 2016), are based on assumption of high emissions of ammonia
during the composting process.
Chapter 3. Life Cycle Assessment 3-23
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Eutrophication
In the wasted food management context, eutrophication is generally due to direct release of nutrients to
water bodies and indirect release via energy use. Eutrophication impacts are measured in nitrogen
equivalents, Neq. The main contributing factors (both positive and negative) are:
Energy use and avoided energy use;
WRRF effluent discharge;
Untreated landfill leachate;
Avoided production and application of synthetic fertilizer; and
Land application of wasted food soil amendments (e.g., wasted food, compost, digestate,
biosolids).
Combustion-based energy production may release NOx to air, which can lead to eutrophication if the NOx
is directly deposited or make its way to an aquatic system. Production of fertilizer is energy intensive and
thus also matters for this impact category. When wasted food or effluent from processing (e.g., of animal
feed) is sent to sewers, there is an increased nutrient load to WRRFs. Although some WRRFs remove
significant fractions of nutrients, at least in the United States, some of the additional nutrient burden is
released to waterways, which contributes to eutrophication.
Finally, depending on management practices and related modeling assumptions, soil amendments may
provide more steady release of nutrients than synthetic fertilizer. This latter source of benefit/impact is not
well or consistently captured in environmental impact modeling. Indeed, a significant portion of the
eutrophication impacts of those pathways (AD, composting, and land application) in which wasted food is
applied to land is driven by modeling of the fate of wasted food on soil. The off-site movement of nutrients
(potentially causing eutrophication), the change in soil organic carbon, the change in soil water retention,
and other effects will depend on local soil types, climatic conditions, and method and rate of application.
For example, municipal biosolids have requirements for setbacks from waterways to reduce
eutrophication impacts. At the level of this analysis, and as discussed in Section 4.6, there is certainly
potential for benefits from land application of wasted food and wasted food-derived soil amendments;
however, modeling of these processes is inconsistent in the literature.
Figure 3-6 shows eutrophication impacts for the wasted food pathways.
Chapter 3. Life Cycle Assessment 3-24
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Eutrophication (kg Neq/metricton FLW)
FIGURE 3-6. COMPARISON OF EUTROPHICATION IMPACT
OF WASTED FOOD PATHWAYS ACROSS LCA STUDIES
AD data assumes land application of digestate or biosolids. Donation excluded from boxplot because the range extends an order
of magnitude below the next lowest value in the boxplot. See Appendix Table D-1 for data and sources.
With inconsistent modeling of the fate of wasted food on soil, and various assumptions about landfill
leachate, the collected LCA eutrophication data suggests there is relatively little differentiation among
pathways, except for source reduction and donation.
While the AD median is close to zero, the highest value for AD eutrophication (3.06 kg Neq) is from
Morelli et al. (2019), which represents co-digestion of wasted food at a WRRF without nutrient removal.
Although wasted food is introduced directly into the digesters, a share of wasted food nutrients is
released with treatment plant effluent via dewatering return flows. The study also includes estimates of
nutrient emissions from land following digestate land application. The next highest AD study value (0.7 kg
Neq) is caused by ammonia emissions after agricultural land application of digestate (Slorach et al.
2019a). However, Slorach et al. (2019a) noted the large uncertainty in this process; in their uncertainty
analysis, the 10th percentile emission is -0.03 kg Neq and the 90th is 0.69 kg Neq. Thus, the authors
report an average that is outside of the 90th percentile of their uncertainty analysis.
The high (7.29 and 7.31 kg Neq) and low (0.016 and 0.02) landfill values are from two related studies that
represent marine and freshwater eutrophication, respectively. Landfill eutrophication impacts are in both
cases driven by assumptions related to leachate releases (Slorach et al. 2019a; Slorach et al. 2019b).
Chapter 3. Life Cycle Assessment
3-25
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Water Consumption
Water consumption is not well-documented in most of the reviewed studies. In general, water
consumption by wasted food pathways is limited compared to that needed for production of food and feed
crops. Thus, water consumption would be driven by avoiding the production of food or feed in pathways
that do so.
While a significant amount of water is withdrawn for energy production, a large fraction of this water is
returned to the basin from which it comes, and so should not be counted as water consumption (Pfister et
al. 2017; Boulay et al. 2018). However, some of the studies that include avoided electricity production
appear to have conflated consumption and withdrawal, as noted below. Process cooling water may be
thermally polluted, with different impacts from those associated with consumption (Raptis et al. 2017).
Thus, water consumption is expected to be low for wasted food pathways; even conveyance to WWT via
sewer would have relatively low water consumption allocated to wasted food.
Figure 3-7 shows water consumption for selected wasted food pathways.
Water Consumption (m3 water/metric ton FLW)
150
100
50
-50
-100
-150
-200
Anaerobic
Digestion
Composting
Controlled
Combustion/
Incineration
Landfill
Upcycle
Donation (2)
Controlled Combustion/
Incineration (4)
Anaerobic
Digestion (10)
Source Reduction (2)
Landfill (4)
"W
Upcycle (2)
Composting (1)
-250
-200
-150
-100
-50
50
100
150
FIGURE 3-7. COMPARISON OF WATER CONSUMPTION
OF WASTED FOOD PATHWAYS ACROSS LCA STUDIES
AD data assumes land application of digestate or biosolids. See Appendix Table D-1 for data and sources.
Values for water consumption are limited. Given the lack of standardization in accounting for water
(discussed above), the water consumption analysis shows the need for further study; there is no clear
distinction among pathways. EPA's From Farm to Kitchen: The Environmental Impacts of U.S. Food
Waste report (U.S. EPA 2021c) highlights the importance of water use within agricultural systems. The
benefit of reduced water consumption from avoided feed production within the animal feed pathway is
poorly captured within the reviewed LCA literature. Relative to the water that could have been used to
irrigate food, the water needed for wasted food processing is relatively restricted. As expected, source
reduction, donation and upcycling demonstrate water savings due to avoided food production; however,
upcycling can also require water for food processing, diminishing savings.
Chapter 3. Life Cycle Assessment
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The lowest water consumption values for AD (-250 and -275 m3, both outside 1.5 xthe inter-quartile
range) are primarily driven by water consumption associated with avoided electricity production (Slorach
et al. 2019a). The authors of that study note that the AD process itself consumes minimal water. All other
data points have an absolute value < 1 m3 water consumed. The positive estimates of AD water
consumption (~0.05 to 0.3 m3) are related to digestate dilution, which is estimated to be about five times
as large as is needed by the AD process itself (Tian et al. 2021). The positive value for composting is due
to electricity use and is based on a single study (Slorach et al. 2019a), and the negative values for
controlled combustion and landfill are also associated with benefits due to avoided electricity. These
differences highlight the general inconsistencies encountered in water consumption inventories.
Data forsewer/WWT was not available from reviewed LCAs, but WRRF effluent is sometimes used to
irrigate crops, thus saving water consumption from irrigation.
Chapter 3. Life Cycle Assessment 3-27
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Land Occupation
In general, relative to food production, the management of wasted food has limited land requirements. As
noted below, there are likely to be some minor differences between the wasted food pathways, though
there are insufficient data to discern meaningful differences.
Figure 3-8 shows the land occupation results for selected, wasted food pathways.
Land Occupation (m2.yr/metric ton FLW)
E
Anaerobic
Digestion
Composting
Controlled
Combustion/
Incineration
Landfill
Source
Reduction (2)
1
-4,500 -4,000
Controlled Combustion/
Incineration (5)
-3,500 -3,000
-2,500
-2,000
Anaerobic Digestion (12) Landfill (4)
-1,500 -1,000 -500 0 500
Composting (3)
FIGURE 3-8. COMPARISON OF LAND OCCUPATION
OF WASTED FOOD PATHWAYS ACROSS LCA STUDIES
AD data assumes land application of digestate or biosolids. See Appendix D-1 for data and sources.
Overall, the land occupation data are too sparse to reveal any trends in impact. The variation among land
occupation values reflects the importance of scope considerations, as discussed previously: e.g.,
inclusion or exclusion of infrastructure; destination of ash produced from combustion (sent to landfill or
used to displace construction aggregate). Nonetheless, some of the values for land occupation suggest
trends, even though the range of values is restricted. The larger positive values are associated with AD,
composting, and landfill. Most composting operations modeled in the literature are windrow or static piles;
like landfilling, this can require appreciable land. Large-scale, in-vessel composting systems would
require less land. In contrast, controlled combustion takes place in engineered systems with relatively low
retention times and thus relatively small land area requirements. It is unclear why AD shows values as
high as composting and landfill, speaking to the variability in modeling assumptions across studies.
Land occupation for wasted food management is not typically a limiting factor or an impact of concern in
the United States. These land occupation estimates are two orders of magnitude smaller than land
requirements of food production. However, while land itself is generally not a limiting factor, we note that
siting of wasted food management systems can be challenging, due to real and perceived concerns about
local impacts on communities.
Chapter 3. Life Cycle Assessment
3-28
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Summary of Inter-Study Findings
The numeric values for the medians and ranges displayed in each preceding boxplot figure are provided
in Table 3-5 and Appendix D. The relative median life cycle impacts by pathway from the analysis across
LCA studies is summarized in Table 3-6.
This section provided high-level comparison of many pathways across LCA studies for six environmental
indicators. For many environmental indicators (besides GWP) data were available for only half the
pathways. Key findings include:
Source reduction, donation and upcycling tend to yield environmental benefits rather than impacts
across all impact categories, while other pathways indicate a mix of environmental benefits and
damages depending on the impact category.
The environmental benefits of source reduction and donation exceed those of any other wasted
food pathway by at least an order of magnitude - except for GWP, where only source reduction
exceeds other pathways by an order of magnitude. Some results show donation as having a
lower impact than source reduction. This reflects different modeling assumptions across studies
and does not indicate that donation is preferable to source reduction.
Among the remaining wasted food pathways, the following observations can be made:
Upcycling also demonstrates very good environmental performance, with negative medians
across all impacts.
Data on unharvested pathway is very limited. While the pathway avoids the impacts associated
with processing, packaging and distribution, the sole data point available showed a small positive
GWP value.
Land application shows positive results across impact categories, but the lack of available studies
for land application means this finding is interim and should be revisited as more data are
available.
By impact, findings indicate:
GWP is the most consistently evaluated impact category. For GWP, source reduction, donation
and upcycling demonstrate strongest performance, followed by the animal feed and AD pathways
which have consistently negative (beneficial) values. The median values for composting, land
application, unharvested/plowed in and controlled combustion are all close to zero (< 53 kg
CCheq/metric ton wasted food), suggesting that these pathways' recovery of resources or energy
from wasted food generally offsets GWP impacts of the pathway itself. The boxplot in Figure 3-3
demonstrates overlap in impact results for the AD, animal feed, compost, controlled combustion
and land application pathways suggesting that modeling assumptions and management practice
have a substantive effect on the GWP impact associated with each pathway. Conversely, landfill
and sewer/WWT GWP impacts are almost entirely above zero, with median values that suggest
they are the poorest-performing wasted food pathways in this impact category.
Not all studies reviewed quantified carbon sequestration within the GWP indicator; where it was
included, it had a moderate effect on overall GWP estimates. This effect could be most
consequential for the composting pathway, as the inclusion of carbon sequestration could switch
the net impact of composting from positive (net source) to negative (net sink) - and for
sewer/WWT, where studies including carbon sequestration from land application of biosolids
showed 50% lower GWPs than those without - further examination of all factors is needed to see
what may be driving this difference in results.
For energy demand, beyond source reduction, donation and upcycling, AD has only negative
values and a significantly negative median value, reflecting that pathway's recovery of energy.
Controlled combustion also shows a consistent, though smaller, recovery of energy. Other
pathways have positive impacts, indicating a net demand for energy.
For acidification and eutrophication, most pathways have a net positive impact, although a single
data point suggests animal feed may have a negative acidification impact. For the other
pathways, modeling assumptions about a) the NOx and SOx intensity of avoided energy sources,
Chapter 3. Life Cycle Assessment
3-29
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b) the quantity of fugitive ammonia emissions, and c) nutrient losses from land-applied material
drive variability across pathways.
Water consumption and land occupation are infrequently reported and inconsistently modeled,
with no clear trends in the collected data.
For all impact categories, the impacts related to wasted food management are small relative to
the impacts associated with food production. Thus, even wasted food pathways with beneficial
performance do little to offset the original impact of producing food.
Chapter 3. Life Cycle Assessment
3-30
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TABLE 3-5. MEDIAN, RANGE (25TH-75TH PERCENTILE), AND SCENARIO COUNT FOR SIX ENVIRONMENTAL IMPACTS
PER METRIC TON OF WASTED FOOD, BY PATHWAY
Impact Category
Statistic
Source
reduction
Donation
Upcycling
Q
<
Animal feed
Composting
Controlled
Combustion
Land
Application
Landfill
Sewer / WWT
Unharvested /
Plowed In
Median
-35
-57
-0.78
0.055
-1.3
0.76
0.087
-
0.24
-
-
Acidification
Range (25 to
75 pctile)
-
-
-
-0.092 to
0.23
-
0.48 to 1.3
-0.086 to
0.39
-
0.17 to 6.6
-
-
Count
1
1
2
18
1
8
11
-
5
-
-
Median
-24000
-17000
-8200
-7000
-
470
-940
-
120
-
-
Energy Demand
Range (25 to
75 pctile)
-
-
-
-9400 to
-2000
-
270 to 1000
-1500 to
1300
-
-200 to 140
-
-
Count
2
2
1
14
-
6
5
-
3
-
-
Median
-21
-2.3
-0.3
0.087
0.15
0.32
0.029
-
0.022
-
-
Eutrophication
Range (25 to
75 pctile)
-
-28 to -1
-3.2 to 0.68
n.d. to 0.27
-0.038 to
2.2
0.00031 to
0.97
0.00075 to
0.16
-
0.013 to 3.8
-
-
Count
1
4
4
24
7
14
18
-
9
-
-
Median
-3300
-570
-450
-110
-210
53
14
23
510
470
47
GWP
Range (25 to
75 pctile)
-3900
to-1700
-2000
to -360
-600 to 68
-230 to -30
-330
to-100
-54 to 79
-27 to 600
17 to 27
190 to 720
210 to 490
-
Count
4
5
3
48
11
26
20
5
15
7
1
Land
Occupation
Median
-4400
-
-
0.6
-
0.27
-0.04
-
2.3
-
-
Range (25 to
75 pctile)
-
-
-
-0.005 to
2.1
-
-0.67 to 4.1
-0.71 to
0.0025
-
0.27 to 3.8
-
-
Chapter 3. Life Cycle Assessment
3-31
-------
Impact Category
Statistic
Source
reduction
Donation
Upcycling
Q
<
Animal feed
Composting
Controlled
Combustion
Land
Application
Landfill
Sewer / WWT
Unharvested /
Plowed In
Count
2
-
-
12
-
3
5
-
4
-
-
Water
Consumption
Median
-210
-230
-1.6
-0.4
-
97
-67
-
-18
-
-
Range (25 to
75 pctile)
-
-
-
-63 to 0.12
-
-
-150
to -0.36
-
-38 to -0.5
-
-
Count
2
2
2
10
-
1
4
-
4
-
-
A dash is used for ranges where the study count is less than 2, or medians or counts with study count less than 1.
Some results below show donation as having a lower impact than source reduction; this reflects different modeling assumptions across studies and does not indicate that
donation is preferable to source reduction.
Compost, AD, and sewer/WWT data assume land application of compost, digestate, orbiosolids.
Chapter 3. Life Cycle Assessment
3-32
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TABLE 3-6. RELATIVE ENVIRONMENTAL IMPACTS BY WASTED FOOD PATHWAY
(MEDIAN IMPACT/METRIC TON WASTED FOOD)
Impact
Category
Median
Impact/
metric
ton FLW
r-\
ill
Donation
/
r———
X
f v.
/
Upcycling
J
s
Re
LJ
L
e
on
1
&
(&)
Controlled
Combustion/
Incineration
ourc
ducti
AD
\nima
Feed
Compost
Landfill
GWP
kg C02eq
3,300
-570
-110
-210
53
14
510
-450
Energy
Demand
MJ
-24,000
-17,000
-7,000
n.d.
470
-940
120
-8,200
Acidification
kg S02eq
-35
-57
5.50E-02
-1.3
0.76
0.087
0.24
-0.78
Eutrophication
kg Neq
-21
-2.3
0.087
0.15
0.32
0.029
0.022
-0.3
Water
Consumption
m3 water
-210
-230
-0.4
n.d.
97
-67
-18
-1.6
Land
Occupation
m2.yr
-4,400
n.d.
0.6
n.d.
0.27
-0.04
2.3
n.d.
Color scale based on trend in median literature data, not statistical differences. Green = lower impact; yellow to orange = moderate impact; red =
higher impact
n.d. = no data
Only pathways which have data for multiple impacts are shown; see Appendix D for more detailed data.
AD data assumes land application of digestate or biosolids.
Chapter 3. Life Cycle Assessment 3-33
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3.5 Quantitative Comparison of Pathways Within
Studies
This section presents the results of pairwise comparisons between five of the most studied wasted food
pathways - AD, animal feed, composting, controlled combustion, and landfill - within individual studies for
six impact categories - GWP, acidification, eutrophication, particulate matter formation, human toxicity,
and ecotoxicity. The intra-study analysis is meant to complement the analysis in the preceding section,
which details environmental comparisons between management pathways across different studies. The
benefit of intra-study comparisons, as presented here, is that individual studies align the scope of their
comparisons across pathways, such that differences in scope (e.g., whether or not transportation is
included or harmonization of energy mix) should not account for reported differences in environmental
performance. In addition, within study analysis allows for the comparison of two subsets of the animal
feed pathway: wet and dry animal feed. See Chapter 2 for further discussion of the differences between
these two sub-pathways.
Methodology for Intra-Study Analysis
The intra-study analysis is drawn from the same pool of papers for which data are presented in Section
3.4. However, the scope criteria outlined in the preceding section were not applied as the studies are
relied upon to harmonize their own scope. In all, thirty-seven studies, which presented data for multiple
pathways, were included in the intra-study analysis. As noted above, twenty-two of these were also used
in the inter-study analysis.
To generate pathway rankings most studies compared midpoint data for each impact. For several studies,
ranked results were utilized directly. If a study reported that two pathways had statistically similar
environmental performance, these pathways were documented as having the same rank. Beyond this,
the magnitude of difference in environmental performance between pathways is not reflected in the intra-
study results. Most studies do not report results of a statistical analysis that allow determination of
significance. To learn more about the magnitude of reported impact differences between pathways,
please refer to Appendix Table D-2.
General impact categories such as eutrophication or human toxicity include several individual indicators
under a single broad heading. For example, eutrophication includes marine and freshwater
eutrophication. Given this, individual studies (such as an analysis that presents both marine and
freshwater eutrophication results) can contribute more than one instance of a unique pairwise
comparison. Since particulate matter and human and ecotoxicity were not discussed in the previous
section, they are discussed briefly below in relation to the wasted food pathways.
Particulate Matter Formation
Particulate matter formation associated with wasted food pathways is driven primarily by energy use and
avoided energy use. In addition, composting emits Nhb, a precursor of PM, as does the application of
organic soil amendments from AD, composting, and sewer/WWT. See Section 4.6 for additional details
on nitrogen losses from soil amendments.
Human Toxicity and Ecotoxicity
Human toxicity and ecotoxicity associated with wasted food pathways are strongly linked to energy
consumption and avoided energy production, land application of soil amendments, and in some cases
process emissions (e.g., controlled combustion).
Intra-Study Results
Figure 3-9 presents a matrix of figures that each compare the environmental performance of two wasted
food pathways, summarizing comparisons from individual studies. The figure depicts the percentage of
results in which the underlying studies, documented in Appendix Table D-2, show that either pathway A
or pathway B has better or similar environmental performance across six impact categories. The count of
study scenarios used to calculate these percentages are documented as bar segment labels. Within the
figures, one color is associated with each pathway and the greater area of a pathway's color in the bar
Chapter 3. Life Cycle Assessment
3-34
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chart indicates that the associated pathway has better performance than the listed alternative. White bar
segments indicate that a percentage of reviewed studies show that the two listed pathways had
statistically similar environmental performance.
Readers interested in the degree to which one pathway is better or worse are referred to the appendices
for specific data, and to the inter-study results for general trends. These trends can give a sense of the
typical (but often variable) differences between pathways. For example, Figure 3-3 shows that the range
of typical GWP values for AD has limited overlap with those for combustion.
Among the six pathways reported in this section, wet and dry animal feed are the two wasted food
pathways that demonstrate the best environmental performance relative to all alternative pathways
across most impact categories. When comparing wet and dry animal feed directly, wet feed is found to
have better environmental performance in all impact categories, due primarily to lower processing energy
demand. Animal feed's good environmental performance is linked to avoided agricultural production of
grains or legumes used in the avoided feed products. Albizzati et al. (2021 b) is the only study to directly
compare wet animal feed to landfill and controlled combustion, finding that wet animal feed has higher
acidification impacts due largely to land application of digestate associated with rejected meat and fish
waste. Dry feed shows some mixed performance compared to other pathways in the toxicity impact
categories. Wasted food collection and transport, pre-treatment and processing all contribute to wasted
food toxicity impacts (Mondello et al. 2017; Albizzati et al. 2021a), presumably associated with energy
consumption. Avoided feed production provides a benefit associated with toxicity impacts.
Anaerobic digestion and controlled combustion are both well studied wasted food pathways within the
LCA literature (see Appendix Table D-2). Wet and dry animal feed typically have lower environmental
impact than these two pathways, despite the exceptions noted in the preceding paragraph which are
based on limited data. The AD and controlled combustion pathways have consistently better
environmental performance than the landfill and compost pathways in all impact categories, due primarily
to the environmental credits associated with energy recovery (i.e., avoided energy use). The compost
pathway does not recover energy and the landfill pathway is less efficient recovering energy from wasted
food and produces a larger quantity of fugitive methane emissions. The AD pathway has better or similar
environmental performance compared to the controlled combustion pathway in GWP and the two toxicity
impact categories. Controlled combustion is often shown to have lower particulate matter and acidification
potential impacts than AD. Impacts in both of these categories are driven by ammonia emissions (Slorach
et al. 2020) released during digestate treatment and land application.
The compost wasted food pathway does not perform well in the intra-study comparisons relative to the
animal feed, AD and controlled combustion pathways. Minor exceptions to this statement include
instances of similar environmental performance when comparing the eutrophication impacts of compost
and AD, the human toxicity impacts of compost and dry feed, and the GWP impact of compost and
controlled combustion. Composting generally performs well compared to the landfill pathway in the
toxicity, eutrophication and GWP impact categories. Composting has relatively low impacts due to its low
process energy requirements but does not recover any of the energy content present in wasted food,
leading to lower environmental benefits when compared to many alternative pathways.
The landfill pathway is consistently shown to have the highest GWP impact when compared to alternative
pathways, due largely to the release of fugitive methane emissions. The landfill pathway consistently has
higher environmental impacts than dry feed, AD and controlled combustion across all impact categories.
Landfill's poor comparative performance relative to these pathways is primarily due to the environmental
credits that these pathways receive for avoided feed and energy production. The landfill pathway has
higher impacts than the wet feed pathway in particulate matter formation, ecotoxicity, and GWP and
similar impacts in human toxicity and eutrophication potential. (Albizzati et al. 2021 b) is the only study to
look at comparative impacts of the wet feed and landfill pathways in the acidification potential impact
category. In this study, wet feed is found to have higher impacts than landfilling due to land application
emissions associated with AD of meat and fish waste that is not suitable for the wet feed pathway (i.e.,
reject stream). Composting generally performs well compared to the landfill pathway in the toxicity,
eutrophication and GWP impact categories, but has higher particulate matter and acidification potential
due largely to ammonia emissions (Slorach et al. 2020).
Chapter 3. Life Cycle Assessment
3-35
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Summary of Intra-Study Findings
This section provided results of pairwise comparisons for five of the most common wasted food pathways
within LCA studies for six environmental indicators. Key findings include:
Among the five pathways evaluated, there is no alternative wasted food pathway that consistently
has higher climate impacts than does landfill disposal.
Most studies find that using wasted food as animal feed leads to better environmental outcomes
compared to alternative pathways. Wet feed is shown to consistently have better performance
than dry feed, due to lower processing requirements, but conclusions are preliminary as only a
small number of studies have considered these wasted food pathways.
AD demonstrates good comparative environmental performance in the GWP and ecotoxicity
impact categories. AD's strong environmental performance is usually associated with
environmental credits from avoided energy production, which depend on the displaced energy
mix. AD's weakest impact category is particulate matter formation, which is linked to biogas
combustion and ammonia emissions.
Composting demonstrates poor comparative environmental performance in acidification and
particulate matter formation relative to all alternative pathways. These impacts are strongly
associated with ammonia emissions during composting and land application. Composting's best
environmental performance is in the GWP category, due to its low energy demand and
environmental credits associated with avoided fertilizer production and carbon sequestration.
Composts best environmental performance is relative to the landfill pathway.
Controlled combustion exhibits strong environmental performance relative to the landfill and
compost pathways across all six impact categories. Positive environmental performance
associated with controlled combustion is strongly linked to avoided energy credits, which depend
on the displaced energy mix. The controlled combustion pathway demonstrates mixed
environmental performance when compared to AD and animal feed.
Landfilling demonstrates poor comparative environmental performance in the GWP,
eutrophication, ecotoxicity, and human toxicity categories. Landfilling's best environmental
performance is in the particulate matter formation and acidification categories where it shows
mixed results compared to alternative pathways. Instances of good environmental performance
for the landfill pathway are typically linked to avoided energy benefits.
Chapter 3. Life Cycle Assessment
3-36
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Landfill compared to Wet Feed
PMFP
Htox
Etox
EP
AP
GWP
2
2 Landfill
Wet Feed 2
2
3
2
20% 40% 60% 80% 100%
¦ Landfill Better ~ Similar 0 Wet Feed Better
Landfill compared to Dry Feed
PMFP
Htox
Etox
EP
AP
GWP
1 Landfill
Dry Feed 2
4
0% 20% 40% 60% 80% 100%
¦ Landfill Better ~ Similar ~ Dry Feed Better
Compost compared to Wet Feed
PMFP
Htox
Etox
EP
AP
GWP
1*— Compost Wet Feed 10
3
9
0% 20% 40% 60% 80% 100%
¦ Compost Better ~ Similar ¦ Wet Feed Better
Compost compared to Dry Feed
0% 20% 40% 60% 80% 100%
¦ Compost Better ~ Similar 0 Dry Feed Better
Compost compared to Landfill
0% 20% 40% 60% 80% 100%
¦ Compost Better ~ Similar ¦ Landfill Better
Landfill compared to Controlled
Combustion
PMFP
Htox
Etox
EP
AP
GWP
0% 20% 40% 60% 80% 100%
I Landfill Better ~ Similar ~ Combustion Better
AD compared to Compost
PMFP
Htox
Etox
EP
AP
GWP
4 2
¦
3
14
4
13 AD | Compost 11
9
3
m
0% 20% 40% 60% 80% 100%
0 AD Better ~ Similar ¦ Compost Better
Compost compared to Controlled
Combustion
PMFP
Htox
Etox
EP
AP
GWP
4
_
~
6
14
5
11
8
9 Compost
[
Combustion 13
0% 20% 40% 60% 80% 100%
¦ Compost Better ~ Similar ~ Combustion Better
FIGURE 3-9. COMPARISON OF ENVIRONMENTAL IMPACT
OF WASTED FOOD PATHWAYS WITHIN STUDIES
AD data assumes land application of digestate or biosolids. See Appendix Table D-2 for data and sources.
Chapter 3. Life Cycle Assessment
3-37
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AD compared to Wet Feed
Wet Feed 6
0% 20% 40% 60% 80% 100%
¦ AD Better ~ Similar a Wet Feed Better
AD compared to Dry Feed
PMFP
Htox
Etox
EP
A P
GWP
3
3 AD
Dry Feed 3
11
0% 20% 40% 60% 80% 100%
¦ AD Better ~ Similar ¦ Dry Feed Better
Controlled Combustion compared to
Wet Feed
PMFP
Htox 2
Etox
EP 3
AP 2
GWP
0% 20% 40% 60% 80% 100%
~ Combustion Better ~Similar «Wet Feed Better
Combustion
Wet Feed 3
AD compared to Landfill
PMFP
Htox
Etox
EP
AP
GWP
¦
2
8 AD L
_andfill3
20
19
16
n
4
9
30 1
% 20% 40% 60% 80% 100%
¦ AD Better ~ Similar ¦ Landfill Better
AD compared to Controlled
Combustion
20% 40% 60% 80% 100%
¦ AD Better ~ Similar ~Combustion Better
Wet Feed compared to Dry Feed
PMFP
Htox
Etox
EP
AP
GWP
3 Wet Feed Dry Feed 2
0% 20% 40% 60% 80% 100%
¦ Wet Feed Better ~ Similar BDry Feed Better
Controlled Combustion compared to
Dry Feed
PMFP
Htox 2
Etox 3
EP
ap 1 Combustion
GWP
Dry Feed 1
2
0% 20% 40% 60% 80% 100%
~ Combustion Better ~ Similar ¦ Dry Feed Better
FIGURE 3-9 COMPARISON OF ENVIRONMENTAL IMPACT
OF WASTED FOOD PATHWAYS WITHIN STUDIES (CONTINUED)
AD data assumes land application of digestate or biosolids. See Appendix Table D-2 for data and sources.
Chapter 3. Life Cycle Assessment
3-38
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3.6 Soil Health
Soil health is the only environmental indicator included in our literature search where data available in
LCAs did not allow for quantitative inter- or intra-study analyses. Soil health is important on global and
local scales for ecosystem services, water conservation, biodiversity protection, and regulation of carbon
and nutrient cycles. But soil health is complex, difficult to measure, and dependent on factors such as
climate, soil texture and management.
There is not yet consensus about a definitive set of
indicators to measure soil health (Rinot et al. 2019)
in LCA, but development of soil health indicators is
ongoing (Bessou et al. 2020). Therefore, no
quantitative metrics for soil health were available for
this report, and improved soil health is not included
in the quantitative LCA analysis - a limitation of this
evaluation. Instead, the LCA review in this chapter
qualitatively considers the effect that wasted food
pathways have on soil health. The five pathways
that apply outputs to the soil (or have the potential to
do so) - unharvested/plowed in, land application,
AD, composting, and sewer/WWT - can benefit soil
health in many ways, including providing organic
matter and organic fertilizer, enhancing water
storage, and promoting water quality and soil
biodiversity. These pathways (as well as landfills)
can also result in carbon sequestration in the soil.
Within reviewed LCAs, environmental credits were
possible (but not given consistently) for carbon
sequestration and avoided fertilizer production and
use. Carbon sequestration is discussed within the
GWP impact category of the LCA review. A detailed
analysis of sequestration credits can be found in
Table 3-4. The numerous other benefits of adding carbon to soils are not captured by carbon
sequestration credits. Some of these benefits are detailed below and in Section 4.6.
LCA can provide credit for avoided fertilizer production and use to these pathways, though application of
credits is inconsistent. For example, LCA studies may or may not include credits for the pathways above
and may apply different credit values for different pathways. Few of the LCAs reviewed on composting
and AD included credits for avoided use of peat as a growing media (Levis and Barlaz 2011; Morris et al.
2017), for which compost and appropriately processed digestate can be effective substitutes. Avoided
fertilizer production and use does not account for additional soil health benefits of organic amendment
use, which are discussed more in Section 4.6.
Nitrogen and phosphorus present in wasted food are important both as resources that can potentially
avoid the production and use of synthetic fertilizers and for their connection to several environmental
impact categories. Efficient recovery of these essential nutrients can decrease further nutrient
mobilization (e.g., reduce chemical nitrogen fixation or phosphorus mining) while also decreasing
contributions to eutrophication and acidification. The plant-availability of nutrients (i.e. inorganic fraction)
and rate of nutrient leakage differ between synthetic fertilizers and organic amendments (hence LCAs
using substitution ratios based on the amount of plant available N, for example, not total N in an organic
soil amendment).
For organic amendments, treatment process, type of soil, crop grown, and climatic conditions can all
impact nitrogen mineralization rates (the rate at which organic N becomes available for crop uptake)
(Brown et al. 2020). However, studies have found that crop response (i.e. crop yield, N uptake, and soil
nitrate N) to organic amendments was similar or improved compared to equal application (in kg N/ha) of
synthetic fertilizer at rates equivalent to standard agronomic recommendations (Koenig et al. 2011;
Cogger et al. 2013). Additionally, slower nutrient mineralization rates positively impact crop response
Organic Amendments and N2O
Using wasted food as a substitute for
fertilizer can lower impacts in LCA studies
by accounting for displaced fertilizer
production. However applied wasted food
still has some impacts, notably the release
of N2O. Additionally, the application of
organic waste, whether untreated wasted
food or processed digestate, compost, or
biosolids can cause a turnover in native soil
organic matter, releasing gases like N2O
(Thangarajan et al., 2013). N2O
volatilization is a concern due to its high
GWP at 265 CCheq (IPCC 2023). However,
N2O emissions from synthetic fertilizers are
typically much greater than from wasted
food-derived organic amendments.
Inorganic N content, C/N ratio, soil texture,
soil drainage, SOM, and precipitation all
affect N2O emissions (Parnaudeau et al.
2009; Charles et al., 2017).
Chapter 3. Life Cycle Assessment
3-39
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across multiple growing seasons, unlike synthetic fertilizers (Cogger et al. 2013). Application of slower-
release fertilizers, such as organic amendments, can increase nitrogen uptake efficiency in soil with
previous N-surplus from synthetic fertilizer use. Increased nitrogen uptake efficiency can result in
reduction of N-surplus and lower soil-based N2O emissions (Morais et al. 2021).
The type, composition, and concentration of nutrients and other organic matter in soil amendments
influences the amendment's ability to meet local nitrogen and phosphorus demands (Moinard et al. 2021).
For instance, compost may not be sufficient to meet a crop's N requirements, or biosolids may contain too
much P to be applied in an area with other P inputs, such as animal manure. When nutrient flows are
considered within a greater agro-food-waste system, the positive impacts of organic amendments
outlined above will depend on the existing nutrient levels in the local pool (van der Wiel et al. 2021). For
example, areas with a high density of animal agriculture tend to have high levels of N and P from
manures; without exporting some of those nutrients to maintain a balance, the area will have a nutrient
surplus and higher N and P emissions. The fertilizing benefits of wasted food-derived soil amendments
will only be realized if the amendments are land-applied at appropriate rates and in an area that lacks
adequate nutrients for current crop growth and land use.
Soil Organic Matter
Soil organic matter (SOM) is perhaps the most important aspect of soil health (Urra et al. 2019) and a key
factor in soil carbon sequestration. SOM content (also known as soil organic carbon content) is a widely
used and accepted metric for soil health (Kopittke et al. 2022; Liptzin et al. 2022), as it is indicative of
fertility, bulk density, water holding capacity, and cation exchange capacity (which helps to cycle
nutrients).
Compost, digestate, biosolids, raw wasted food, and unharvested/plowed-in crops are all sources of
organic matter. Increasing soil organic matter promotes nutrient cycling and retention, makes nutrients
available for plant uptake and decreases nutrient runoff, and helps to maintain balance in the nitrogen
and phosphorus cycles. Carbon can be sequestered in soils when the rate of organic carbon added is
greater than the rate of carbon lost through mineralization. Any increase in SOM results in significant
improvements to soil quality and function (Poulton et al. 2018).
SOM consists of living organisms in soil, plus root exudates and residues from plants at various stages of
decomposition. As soil microbes breakdown organic matter, the nutrients (e.g., nitrogen, phosphorus)
within it are mineralized and become available for plant uptake. Some organic carbon is released as CO2;
some is stored in the soil. Enzymes from microbes and earthworms help build soil aggregates which
enhance water infiltration and retention and reduce the risk of soil erosion. The rate at which these
processes occur depends on the type of organic matter applied, rate of application (Peltre et al. 2012),
soil pH, carbon-to-nitrogen ratio (C:N), soil temperature and moisture, the diversity of microbes, and the
physical structure of the soil. Soil science is still understanding how soil organic matter results in stable
stores of carbon, such as those required for sequestration. The theory of "humification" of organic matter
- the formation due to chemical interactions of large, dark, carbon-rich, soil particles that are slow to
decay - is becoming less of a focus (Lehmann and Kleber2015). Rather than the chemical properties of
soils driving carbon stabilization and sequestration, microbial activity and the physical properties of soils
may be more influential (Lehmann and Kleber2015; Witzgall et al. 2021).
Recent research shows that soil structure - the bulk density, porosity, particle size, aggregate size and
stability - determines the accessibility of organic matter to microbes. Simply put, where organic matter is
easily accessible, microbes will consume it no matter its chemical stability (i.e., labile or recalcitrant). But
when organic matter is trapped inside a soil aggregate or otherwise inaccessible to microbes, that organic
matter (i.e., carbon) is protected from decomposition and remains in the soil. Decreasing bulk density and
increasing porosity and aggregate stability also improves microbial habitat which stimulates microbial
activity and diversity and soil function overall (Urra et al. 2019).
Practices to increase SOC are often limited by insufficient local resources (e.g., compost or biosolids),
pre-existing levels of SOC high enough to limit the rate of additional SOC sequestration through
amendment application, economic accessibility for farmers, and the impact that adoption of those
practices might have on crop yield.
Chapter 3. Life Cycle Assessment
3-40
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Soil health is important for reasons beyond environmental impacts and benefits. Humans rely on soils to
grow food, fiber, and energy crops. Healthy soils produce more nutritious food for humans and animals,
and degraded soils have been linked to malnutrition and food insecurity (FAO 2022). Increasing the
fertility of soils by ensuring adequate amounts and availability of macronutrients - nitrogen, phosphorus,
potassium, calcium, magnesium, sulfur - and micronutrients - boron, copper, zinc, iron, etc. - increases
both the productivity of plants and their nutritive value.
3.7 Limitations of LCA Review
This section discusses limitations to LCA and this LCA review beyond the lack of quantitative data for soil
health. Summary results and high-level conclusions, including the hierarchies of wasted food pathways
presented below, are subject to caveats and limitations. While details presented throughout this report
aim to identify potential differences in environmental impact that will result from different wasted food
pathways, it is beyond the scope of this analysis to systematically present results for specific categories of
wasted food or specific sub-technologies or management practices within a given pathway. The range of
available technologies, management considerations and the demonstrated overlap or trade-offs in
environmental impact that occurs across many pathways indicates that management matters and defies
the desire to obtain a strict and simple ranking.
Furthermore, when considering post-consumer wasted food, often the waste stream is a mixture of many
food types. When wasted food is mixed with other MSW or is co-processed with other organic waste
streams the actual performance of management pathways will reflect not wasted food alone but the bulk
waste stream with which it is processed. Many of the studies referenced throughout this document
endeavor to model wasted food-specific impacts, however the specific assumptions employed and the
degree to which this goal is achieved varies considerably within the literature. Some studies included in
the LCA analysis do include another organic co-waste (e.g., yard trim for composting). These studies
were only included when wasted food was the primary feedstock. These results, however, reflect the
impact of the bulk waste stream. Wasted food composition based on local diets, inclusion of packaging,
or the composition of source material can also influence potential treatment pathways, their efficiency,
and the LCA results (Mondello et al. 2017).
For many combinations of management pathway and environmental impact category, the number of
studies or scenarios modeling these impacts is limited. Given the range of reasonable assumptions,
pathway technologies and management practices observed, when only a small number of
studies/scenarios were identified it is probable that documented environmental performance may not well
represent the average environmental performance of that pathway in real-world conditions.
Despite the preceding limitation, the LCA studies reviewed are broadly intended to reflect "current"
pathway performance. While this knowledge is relevant, it may not be sufficient to answer the question of
how communities and individuals should seek to manage wasted food in the future. As an example of this
topic and exception to this general statement, several studies have looked at the impact that a future,
cleaner electricity fuel mix would have on pathway performance. Furthermore, this report has not
extensively highlighted opportunities to improve pathway environmental performance. Such opportunities
certainly exist for all of the examined wasted food pathways. Examples of opportunities for improved
performance are provided below:
Utilize renewable energy. Applies to all wasted food pathways;
Use enhanced emission controls on electrical or CHP engines. Applies to multiple pathways
including AD, controlled combustion, and landfill;
Utilize compost biofilters, which oxidize methane to carbon dioxide and reduce odors. Use of
Gore covers also controls odors and reduces emissions of ammonia and volatile organics (Levis
and Barlaz 2011);
Expand the use of heat recovery. Applies to multiple pathways including AD, controlled
combustion, landfill and composting.
The scope criteria (Table 3-3) used for the inter-study analysis attempt to harmonize environmental
performance of the management pathways according to a simple definition of "good" practice from an
LCA perspective. This largely means that the management pathway is required to include readily
Chapter 3. Life Cycle Assessment
3-41
-------
achievable environmental credits. The included scope criteria do not ensure "good" environmental
performance, and may depart from current, average pathway performance.
The detailed discussion of environmental drivers in Chapter 2 combined with local knowledge regarding
the operation and performance of management pathways in a specific region or community should help
individuals interpret the hierarchies of wasted food pathways, presented below, in an appropriate manner.
Additional information on identified research gaps is presented in Chapter 6.
3.8 Summary of LCA Review Findings
This section summarizes the environmental impacts and benefits of wasted food pathways, drawing on
the literature search findings described in this chapter and the previous chapter.
LCA Findings, by Indicator
Table 3-7 summarizes the contribution of wasted food pathways to each environmental indicator.
For global warming potential, all pathways are beneficial or near neutral, except for landfill and
sewer/WWT. Many indicators, including GWP, are impacted by energy use. All pathways except source
reduction use energy, and three pathways - AD, controlled combustion, and landfill - also generate
energy from wasted food, offsetting some or all of their energy use. Energy use and avoided energy use
affect the following indicators: GWP, energy demand, acidification, eutrophication, PM, human toxicity
and ecotoxicity, and water consumption, thus assumptions about energy mix are important to findings.
Additional sources of impact beyond energy use include the following: fugitive methane, nitrous oxide,
and ammonia emissions. Some pathways produce environmental benefits through avoided production of
food, feed, and/or synthetic fertilizer and/or avoided use of synthetic fertilizer.
Chapter 3. Life Cycle Assessment
3-42
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TABLE 3-7. SUMMARY OF WASTED FOOD PATHWAY IMPACTS AND BENEFITS, BY ENVIRONMENTAL INDICATOR
GWP
Water
(including
Human
Consumption
carbon
Energy
Particulate
Toxicity and
and Land
sequestration)
Demand
Acidification
Eutrophication
Matter
Ecotoxicity
Occupation
Soil Health
Summary
Most pathways
All pathways
Energy use and
Nutrient losses
Energy use and
Dependent on
Benefits driven
Benefits driven
beneficial or
(except source
avoided energy
directly into
avoided energy
technology, co-
by avoiding
by land
near neutral,
reduction) use
use largely
waterbodies
use largely
feedstocks,
food/feed
application of
except Landfill
energy; AD,
drive
from
drive PM
management
production;
wasted food
and Sewer/
controlled
acidification;
Sewer/WWT
formation;
practices
other impacts
and soil
WWT which
combustion,
Composting
and Landfill or
Composting
relatively small
amendments
emit substantial
and landfill
emits NH3; Soil
soil
emits NH3
made from
CH4
produce energy
amendments
from AD >
Sewer/WWT >
Composting
emit NH3
amendments
from AD,
Composting,
Land
Application;
Indirect losses
through energy
use (all
pathways)
wasted food
Energy Use*
CO2 emissions
Energy
S0X and N0X
N0X emissions
PM and
Hazardous air
Power plants
by Pathway
demand:
emissions
precursors
pollutants
typically use but
0)
£
d)
(all pathways except
Composting >
(SOx, NOx, NH3)
including
do not consume
DQ
source reduction)
Landfill >
mercury and
water
O
Controlled
dioxins
O
Combustion >
Q.
E
AD
5
£
a>
Pathway
Fugitive ChU
NH3 from
Release of
Nbhfrom
Incinerator
E
£
Process
emissions from
Composting
nutrients by
Composting
emissions
O
i—
Sewer/WWT
Sewer/WRRF
(dependent on
>
£
111
and Landfill >
effluent; NH3 in
technology and
O
Composting
Landfill
emissions
a>
o
and AD;
untreated
controls) and
k—
3
N2O from
leachate
disposal of ash;
u
CO
Composting
and
Landfill
untreated
Chapter 3. Life Cycle Assessment
3-43
-------
GWP
(including
carbon
sequestration)
Energy
Demand
Acidification
Eutrophication
Particulate
Matter
Human
Toxicity and
Ecotoxicity
Water
Consumption
and Land
Occupation
Soil Health
Sewer/WWT;
Carbon
sequestration
from landfill
leachate;
Sewer/WWT
effluent
Soil Amendments**
Carbon
sequestration:
Composting,
AD and
Sewer/WWT
Release of
nutrients from
application of
organic
amendments
from AD,
Composting,
Land
Application
Dependent on
contamination
of feedstocks,
treatment
methods,
application
rates
Soil health
benefits:
Compost, AD,
Sewer/WWT,
Land
application,
Unharvested/
plowed in
Avoided Synthetic
Fertilizer Manufacturing
and Use**
CO2 savings for
Compost, AD
and
Sewer/WWT
Organic
amendments
from Compost,
AD, and
Sewer/WWT
release less
N2O than
synthetic
fertilizers
Energy savings
for Compost,
AD and
Sewer/WWT
SOx, NOx, and
NH3 savings for
Compost, AD
and
Sewer/WWT
Organic
amendments
from Compost,
AD,
Sewer/WWT
release less
NH3 emissions
and leach and
runoff less
nitrates than
synthetic
fertilizers
Organic
amendments
from Compost,
AD,
Sewer/WWT
release less
NH3 emissions
than synthetic
fertilizers
Chapter 3. Life Cycle Assessment
3-44
-------
GWP
(including
carbon
sequestration)
Energy
Demand
Acidification
Eutrophication
Particulate
Matter
Human
Toxicity and
Ecotoxicity
Water
Consumption
and Land
Occupation
Soil Health
Avoided Food or Feed
Production
CO2, CH4, and
N2O savings for
Source
reduction >
Donation/
Upcycling >
Animal feed
Energy savings
for Source
reduction >
Donation/
Upcycling >
Animal feed
SOx, NOx, and
NH3 savings for
Source
reduction >
Donation/
Upcycling >
Animal feed
Savings for
Source
reduction >
Donation/
Upcycling >
Animal feed
Avoided
Energy Use
CO2 savings for
AD > Controlled
Combustion >
Landfill
AD, Controlled
Combustion
and Landfill
produce net
energy
SOx and NOx
savings for AD
> Controlled
Combustion >
Landfill
Including on-site use of energy derived from wasted food by the pathway
"""Benefits apply only if digestate or biosolids from AD or Sewer/WWT are beneficially used. If they are disposed of, impacts from landfill or controlled combustion
apply.
Chapter 3. Life Cycle Assessment
3-45
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LCA Findings, by Pathway
The following sub-sections synthesize environmental impacts associated with each wasted food pathway.
Note that most pathways covered in this report pertain to wasted food management. The source
reduction, donation, and upcycling pathways, though, are functionally different: source reduction avoids
the creation of wasted food in the first place, while donation and upcycling capture wasted food and
recover it for human consumption. All other wasted food pathways (except animal feed, which indirectly
feeds humans by feeding livestock) capture wasted food and take it out of the food supply chain, possibly
recovering energy or other beneficial products.
Source Reduction
Source reduction is environmentally preferable to all other pathways and can be implemented at all
stages of the supply chain. Avoiding the creation of wasted food saves more resources than can be
captured from processing that wasted food via one of the other pathways. There is broad consensus in
the literature—and in the findings of this LCA literature review—around this point:
The environmental benefits of source reduction exceed those of any wasted food pathway other than
donation and upcycling by at least one order of magnitude.
WRAP also estimates environmental benefits for source reduction and donation that are an order of
magnitude greater than the considered pathways (WRAP 2015).60
A United Nations report says that "preventing wasted food and ... reducing excess food production is a
far more effective strategy for minimizing environmental impact than optimizing end-of-life management"
(Heller 2019).61
Beretta et al. (2017) looked at sources of GWP impact across the food value chain and concluded that
the potential benefits of management of wasted food are small (5%-10%) relative to the burdens of initial
food production and that preventing wasted food (i.e., through source reduction, donation and upcycling
pathways) should be prioritized.
Source reduction, if implemented appropriately, does not reduce the amount of food available for human
consumption, but rather reduces waste in the supply chain. However, we note that source reduction is a
necessary but incomplete approach for reducing the environmental impacts of wasted food. Even with an
optimal production and distribution system, some wasted food will be generated (e.g., inedible food parts
such as shells or bones) so other pathways must be used to efficiently manage wasted food.
Donation and Upcycling
The management of wasted food via donation, and to a lesser extent upcycling, demonstrate
environmental benefits similar to source reduction. However, both donation and upcycling have
inefficiencies, generate waste, and require resources to collect and redistribute (donation) or process
(upcycling) the recovered wasted food. Therefore, it is environmentally preferable to avoid wasted food in
the first place (via source reduction).
Median impact values show that the magnitude of environmental benefits associated with donation are
similar to those of source reduction and exceed the benefits of any other pathway (except upcycling) by at
least one order of magnitude.
Damiani et al. (2021) modeled wasted food distribution and found that donation had better environmental
performance across 18 impact categories, relative to a mix of controlled combustion, AD, and
composting.
An analysis of fresh fruit and vegetable supermarket waste in Sweden found that donation and upcycling
had much lower GWP and energy demand than controlled combustion and AD pathways (Eriksson and
Spangberg 2017).
The validity of similar conclusions for the upcycling pathway will depend on the energy, resources, and
emissions needed to reprocess wasted food for human consumption. Our literature reviewed found only
two studies that investigated examples of upcycling; they include reprocessing fruit and vegetable waste
Chapter 3. Life Cycle Assessment
3-46
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into chutney (Eriksson and Spangberg 2017) and converting low grade broccoli crowns and stems into a
bread additive or soup base (Eriksson et al. 2021). These studies show that impacts of processing are
more likely to affect the net impact of upcycling when they differ substantially from the avoided production
process.
Like source reduction, the donation and upcycling pathways receive an environmental credit for avoiding
the production of additional food. However, as illustrated by Eriksson and Spangberg (2017), not all the
rescued food collected for donation or upcycling helps to avoid food production. There will be some
measure of waste present in each system. Eriksson and Spangberg's analysis assumes that 40% of
donated food either replaces nothing or is otherwise wasted. Still, the magnitude of benefits associated
with avoided food production are such that this loss of food is not enough to diminish the benefit of
donation relative to other pathways.
The donation and upcycling pathways also require management, energy, and other resources to recover
(donation), refine (upcycling), and distribute the diverted wasted food. While there are environmental
impacts associated with collecting, redistributing, or refining food, these impacts tend to be smaller than
those from the production of food in the first place. The magnitude of benefits associated with avoided
food production is such that this loss of food is not enough to diminish the benefit of source reduction,
donation and upcycling relative to other pathways.
Animal Feed
Although the use of wasted food as animal feed is less well-studied than some other management
pathways, the reviewed studies demonstrate favorable environmental performance relative to the wasted
food pathways beyond source reduction and donation. Broadly, repurposing wasted food for animals can
offset production of animal feed, which can be resource intensive.
Inter-study (Section 3.4) results show the potential of the animal feed pathway to yield environmental
benefits in the GWP and acidification impact categories. Eutrophication impacts of animal feed range
widely in the reviewed studies with net impacts that overlap those of all other reviewed pathways. While
no quantitative data were identified for the land occupation category and limited data for water
consumption, the contributions of avoided grain production to animal feed's net environmental
performance make environmental benefits likely in these categories.
Intra-study (Section 3.5) results show that using wasted food as animal feed generally leads to better
environmental outcomes compared to the landfill, AD and compost pathways. However, the landfill
pathway has overlapping environmental performance with wet feed in human toxicity and eutrophication
and better performance in acidification. Wet feed is shown to consistently have better performance than
dry feed, due to fewer processing requirements. Wet and dry feed show trade-offs in environmental
impact when compared to controlled combustion. Wet and dry feed both have lower particulate matter
and GWP impact than controlled combustion in all reviewed study scenarios. The controlled combustion
pathway shows potential for overlapping environmental performance with wet and dry feed in human
toxicity, wet feed in eutrophication, and dry feed in acidification. Albizzati et al. (2021 b) is the only study to
directly compare wet animal feed to landfill and controlled combustion, finding that wet animal feed has
higher impacts due largely to land application of digestate associated with meat and fish waste not
suitable for incorporation in the feed product.
Given the small number of studies on which these findings are based, more research into different
technologies for animal feed production and systems of use (e.g., varying transportation distances) is
needed to improve confidence in our understanding of the benefits of using wasted food as animal feed.
The importance of avoided feed-grain production to environmental performance also warrants further
research to examine the range of potential production systems and determine the appropriate type and
quantity of avoided product for different wasted food types.
Anaerobic Digestion
AD is well-represented in the reviewed LCA studies. Median impact results are quite robust for AD,
relative to environmental results for other management pathways, given the high number of reviewed
studies that include AD as a wasted food management option.
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Inter-study results in Section 3.4 demonstrate that among the wasted food pathways, beyond the source
reduction, donation and upcycling pathways, AD has the potential to produce some of the largest
environmental benefits in the GWP and energy demand impact categories due to its production of energy
from wasted food. For acidification, the impact of AD falls in between results identified for other pathways
showing a similar range of impacts to the controlled combustion pathway, higher impact than animal feed
and lower impacts than the compost and landfill pathways. Eutrophication and land occupation impacts of
the AD pathway overlap considerably with identified results for other wasted food pathways.
According to intra-study results in Section 3.5, AD has consistently better environmental performance
than the compost and landfill pathways. Wet and dry animal feed generally produce lower environmental
impacts (or greater benefits) than the AD pathway. AD demonstrates excellent comparative
environmental performance in the GWP and ecotoxicity impact categories when compared to compost
and landfill. The AD pathway has better or similar environmental performance compared to the controlled
combustion pathway in GWP and the two toxicity impact categories. Controlled combustion is often
shown to have lower particulate matter and acidification potential impacts than AD.
The AD pathway produces digestate or biosolids (if made through co-digestion at a WRRF), a nutrient-
rich soil amendment, that has the potential to positively influence soil health. This analysis has focused on
LCA studies that assume ultimate land application of digestate; however, not all digestate and biosolids
are land applied. Where these outputs are disposed of via controlled combustion or landfill, credits for
carbon sequestration and avoided fertilizer production and use are not warranted. LCA studies rarely
consider this scenario. When digestate is incinerated or landfilled, environmental impacts will vary,
nutrient losses from land application will be reduced, there will be no fertilizer offset, and additional
energy may be recovered.
Research described in Section 4.6 outlines the potential soil health benefits of digestate use, such as
nutrient recycling, improved soil structure, water retention, and water quality improvement. Land
application of digestate can also contaminate soil, with subsequent human health impacts, if wasted food
or co-treated wastes are contaminated. Research suggests that soil contamination may be more likely
when wasted food is co-digested with biosolids or manure. To improve the quality and consistency of
environmental impact results, more research on the potential impacts and benefits of digestate land
application needs to be performed and incorporated into LCA models.
AD's reported environmental performance also relies on avoided energy credits that will diminish over
time as U.S. energy mixes reduce reliance on fossil fuels. This trend is expected to negatively affect the
long-term relative performance of this pathway.
Composting
The GWP boxplot in Figure 3-3 demonstrates a large potential for overlap of composting's net impact with
that of the AD, animal feed, controlled combustion, and land application pathways in the GWP and
eutrophication impact categories. Inter-study results show that composting has a higher, net positive (i.e.,
impact) energy demand than AD, controlled combustion, and landfill. The same is true for acidification,
however the range of compost impact overlaps more considerably with the range of net impacts identified
for the landfill pathway.
Intra-study results in Section 3.5 indicate that in the majority of reviewed study scenarios compost has
higher environmental impacts than the animal feed, AD, and controlled combustion pathways.
Composting demonstrates poor comparative environmental performance in acidification and particulate
matter formation relative to all alternative pathways. These impacts are strongly associated with ammonia
emissions during composting and land application. The best environmental performance of compost is
observed in the GWP category, due to its low energy demand and environmental credits associated with
avoided fertilizer production and carbon sequestration. Compost's best environmental performance is
relative to the landfill pathway where a majority of study scenarios show that compost has better
performance in the toxicity, eutrophication and GWP categories.
Carbon sequestration benefits are an important factor in median estimates of net GWP for the
composting pathway and not all studies reviewed included this benefit (Table 3-4). Where carbon
sequestration was included, it had a moderate effect on overall GWP estimates. This effect could be most
consequential for the composting pathway, as the inclusion of carbon sequestration could switch the net
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impact of composting from positive (net source) to negative (net sink). Another review of wasted food
management LCAs found that researchers assumed composting had more potential to sequester wasted
food carbon than AD but less potential than landfilling (Bernstad Saraiva Schott et al. 2016).
Composting has the highest energy demand among the assessed wasted food pathways for which data
were available. Although many composting operations require relatively low energy inputs, this pathway
does not recover any of the energy present in wasted food, affecting its performance relative to other
pathways.
Figure 3-9 shows that across intra-study comparisons, composting has higher or equivalent
environmental impacts than controlled combustion in the majority of reviewed study scenarios across all
assessed impact categories. These conclusions are subject to several caveats. First, the major
disadvantage of the composting pathway is that it does not recover any of the energy present in wasted
food. The U.S. depends heavily on fossil fuels for energy; this benefits the net environmental performance
of the AD, controlled combustion, and landfill pathways, for which energy recovery is common.62 In the
future, as cleaner energy sources become more prevalent, the relative environmental performance of
composting will improve, as wasted food pathways that derive benefit from avoided energy production will
show fewer benefits. Second, the composting pathway produces a nutrient- and carbon-rich soil
amendment that has the potential to positively influence soil health. Research presented in Section 4.6
outlines the soil health benefits of compost use, such as nutrient recycling, improved soil structure, water
retention, and water quality improvement. The interactions of compost in the soil and accompanying
agronomic practices are complex and are not treated consistently in the reviewed LCA literature. To
improve the quality and consistency of environmental impact results, basic scientific research on the
potential impacts and benefits of compost land application needs to be translated to LCA models.
Controlled Combustion
Based on this literature review, the availability of effective emission control devices and the ability to
recover energy result in a higher ranking for controlled combustion (i.e., incineration) than for landfill.
Controlled combustion of MSW, including wasted food, without energy recovery is not common in the
United States (U.S. EPA 2022b; U.S. EPA 2023c).
Inter-study results in Section 3.4 show that controlled combustion has wide variation in GWP performance
and overlapping estimates of eutrophication with the AD, animal feed and compost pathways. For
acidification the impact of controlled combustion falls in between results identified for other pathways
showing a similar range of impacts to the AD pathway, higher impact than animal feed and lower impacts
than the compost and landfill pathways. Land occupation and water consumption impacts of the
controlled combustion pathway are low compared to other wasted food pathways.
Controlled combustion exhibits strong environmental performance relative to the landfill and compost
pathways across all six impact categories, where the majority of study scenarios show that controlled
combustion's net impact is lower than that of landfill or compost. In the GWP and particulate matter
impact categories, reviewed results indicate similar or overlapping environmental performance for
controlled combustion with the compost and landfill pathways, respectively. Good environmental
performance associated with controlled combustion is strongly linked to avoided energy credits, which
depend on the displaced energy mix. The controlled combustion pathway demonstrates trade-offs in
environmental performance and the potential for overlapping impacts when compared to AD and animal
feed. Note that this analysis did not quantitatively consider soil health benefits.
Clavreul et al. (2012) looked at wasted food moisture content and heating values, finding that wasted food
sources with lower moisture content and greater heating values favor controlled combustion, whereas
wasted food sources with higher moisture content and lower heating values favor AD for the GWP impact
category. Below 16 MJ/kg total solids, AD is preferred, while above 20.5 MJ/kg total solids, controlled
combustion is preferred. Between these values, the technology preference is determined by moisture
content. The range of variability in wasted food characteristics across studies likely plays a significant role
in the variability identified in environmental impact results for all wasted food pathways.
Controlled combustion's reported environmental performance also relies on avoided energy credits that
will diminish overtime as U.S. energy mixes reduce reliance on fossil fuels. This trend is expected to
negatively affect the long-term relative performance of this pathway.
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As noted in Section 2.7, though there have been changes in emission control technologies, siting of
controlled combustion facilities has disproportionately affected disadvantaged communities. Therefore,
controlled combustion—to a greater degree than other wasted food pathways—has associated concerns
about localized human health impacts.
Landfill
The findings of this literature review corroborate the general finding that landfilling of readily degradable
wasted food will generate considerable quantities of fugitive methane emissions. Given the difficulty in
efficient capture of that methane, these emissions typically drive GWP impact for that system. Results for
several other impact categories also provide a strong environmental basis for preferring other wasted
food pathways instead of landfill disposal of wasted food.
Looking across study scopes in Figure 3-3, wasted food landfilling consistently leads to high GWP
impacts relative to other management pathways, except sewer/WWT. Intra-study results corroborate the
high GWP impacts that result from wasted food landfilling, showing that in greater than 90% of reviewed
study scenarios, GWP comparisons between landfill and four other common wasted food pathways (AD,
animal feed, composting, and controlled combustion), landfilling demonstrated higher GWP impact.
In Section 3.5, landfilling demonstrates poor comparative environmental performance in the GWP,
eutrophication, ecotoxicity, and human toxicity categories. Landfilling's best environmental performance is
in the particulate matter formation and acidification categories where it shows mixed results compared to
alternative pathways. Instances of good environmental performance for the landfill pathway are typically
linked to avoided energy benefits, limited energy requirements and comparatively lower ammonia
emissions.
Landfilling of MSW, including wasted food, is a heterogeneous, dynamic process. Therefore, landfilling is
less well-suited to resource recovery than the other wasted food pathways. Wth respect to GWP, it is
difficult to efficiently capture methane generated in these systems, especially given wasted food's rapid
decomposition rate, which may be faster than the rate at which landfills are capped to recover methane.
Although landfilling may have relatively low energy requirements, it requires a significant land area, has
low relative energy recovery, consistently leaches pollutants to water via leachate, and therefore tends to
have poorer environmental performance than other wasted food pathways.
Land Application, Unharvested/Plowed in and SewerAAAA/T
The land application, unharvested/plowed in and sewer/WWT pathways are poorly studied relative to the
other pathways listed above. The land application and unharvested /plowed in pathways were found to
have a small GWP impact in the range of values observed for AD, composting and controlled combustion.
The sewer/WWT pathway was found to have a high GWP, comparable to that of the landfill pathway, in
part due to estimated methane production within the sewer system, which was estimated assuming 10%
of COD (Parry and WERF 2012) or 6% of volatile solids (Edwards et al. 2018) degrade anaerobically
during sewer transport. All of these pathways would benefit from further study.
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3.9 LCA Conclusions
This section synthesizes the results of the review of LCA literature in this report through two rankings of
the pathways. These rankings are based on the environmental performance of the pathways with wasted
food as a feedstock.
Figure 3-10 presents a ranking based solely on GWP. The GWP ranking is based largely on the
distribution of data shown in Figure 3-3, with additional considerations regarding the biophysical bases for
the pathways and the degree to which the pathways are represented in the literature.
Figure 3-11 presents a ranking based upon LCA results from all eleven impact categories considered-
including GWP (including soil carbon sequestration), energy demand, acidification, eutrophication,
particulate matter, human toxicity, ecotoxicity, land occupation, water consumption, and soil health.
As shown in Figure 3-10 and Figure 3-11, the LCA rankings for GWP and for all eleven impacts are very
similar. For GWP, animal feed and AD rank just above composting, controlled combustion, and land
application, whereas when the ranking criterion is extended to all LCA impact categories, these five
pathways are considered to comprise only one tier. For indicators beyond GWP, fewer data are available
and greater uncertainties exist, leading to less differentiation among pathways in the hierarchy. The
broader hierarchy also considered soil health qualitatively, since it is not captured in the quantitative LCA
analysis. As the intra-study analysis shows, there are meaningful differences between some of the
pathways grouped as single tiers above; however, application specifics, such as operating conditions,
should be considered if refining beyond the tiers presented.
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More
preferred
Source Reduction
Donation, Upcycling
Unharvested I Plowed In*
Anaerobic Digestion, Animal Feed
Composting, Controlled Combustion,
Land Application*
Landfill, Sewer IWWT (with or without AD)
Less
preferred
FIGURE 3-10. GLOBAL WARMING POTENTIAL: RANKING OF WASTED
FOOD PATHWAYS
Indicates limited data available for a pathway
The ranking reflects each pathway's performance in global warming potential.
Chapter 3. Life Cycle Assessment
More
preferred
CO
o
ro
Q.
E
<
O
Source Reduction
Donation, Upcycling
Unharvested I Plowed In*
Anaerobic Digestion, Animal Feed,
Composting, Controlled Combustion,
Land Application*
Landfill, Sewer / WWT (with or without AD)
Less
preferred
FIGURE 3-11. ALL LCA INDICATORS: RANKING OF WASTED FOOD
PATHWAYS
"indicates limited data available for a pathway
The ranking reflects each pathway's performance in 11 impact areas: global warming
potential, carbon sequestration, energy demand, acidification, eutrophication, particulate
matter, human toxicity, ecotoxicity, land occupation, water consumption, and soil health.
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Key LCA Findings:
The environmental benefits of source reduction and donation exceed those of any other wasted
food pathway by at least one order of magnitude (except for GWP, where only source reduction
exceeds all other pathways by an order of magnitude).
Landfill and sewer/wastewater treatment (with or without AD) stand out for their substantial
fugitive methane emissions from the decay of wasted food in anaerobic conditions, and, for that
reason, rank at the bottom of the LCA-based hierarchy.
The unharvested/plowed in pathway is ranked high in both hierarchies. However, this pathway is
limited to on-farm wasted food and is only recommended when food is unmarketable or otherwise
likely to be wasted. In this context, the pathway provides an opportunity to avoid the
environmental impacts of downstream processing, packaging, and distribution, while also
returning nutrients to the soil. Limited data did not allow for in-depth analysis of this pathway.
Upcycling is also not well-studied; however, the substantial benefits of avoided food production
outweigh the resource use (energy, water) of processing wasted food, resulting in net benefits
(i.e., negative medians) for all impacts.
The differences among the remaining pathways are small compared to the differences between
them and the highest-ranked pathways (source reduction and donation) and the lowest-ranked
pathways (landfill and sewer/WWT). In particular, the performance of AD, animal feed,
composting, controlled combustion, and land application are quite similar.
The median GWP of all pathways except landfill and sewer/WWT were found to be negative (i.e.,
beneficial) or near zero.
For GWP, carbon sequestration credits were inconsistently applied in LCAs reviewed and when
applied, provide a moderate benefit to composting and anaerobic digestion, potentially moving
compost from net source of GWP to net sink of GWP. When applied to sewer/WWT the benefit is
larger, demonstrating the importance of beneficial use of biosolids to the GWP performance of
the pathway.
Per ton of wasted food, AD can produce more energy from wasted food than controlled
combustion, which produces more energy than landfill gas capture systems. The moisture of
wasted food reduces efficiency of energy recovery by controlled combustion and can require pre-
drying of feedstock before processing, increasing the energy use of the pathway. Methane can
off-gas from wasted food before installation of landfill gas capture systems, reducing potential for
energy recovery from wasted food and resulting in fugitive methane emissions.
Five pathways can contribute to soil health and carbon sequestration: AD, composting, land
application, sewer/WWT, and unharvested/plowed in. However, for two of these pathways (AD
and sewer/WWT), the nutrients recovered are sometimes landfilled or incinerated rather than
beneficially used. LCA assumptions vary, but AD is typically credited with carbon sequestration
and avoided fertilizer manufacturing and use in LCAs. This is legitimate only if digestate or
biosolids (if produced through co-digestion) are applied to land. Among the sewer/WWT studies
reviewed, two did include carbon sequestration offsets; five did not (Table 3-4). As shown in that
table, studies that do include carbon sequestration tend to show a modest decrease in GWP.
The environmental performance of individual pathways is highly variable and is affected by
operating parameters, such as technology type or temperature and pre- and post-treatment of
outputs. For example, composting is well-studied but inconsistently modeled by LCA, and
process emissions are variable due to composting method, facility management, and
environmental conditions.
GWP and energy demand impacts are reduced when pathways produce energy, due to avoided
fossil fuel use. In the future, as the energy mix changes to include fewer fossil fuels and thus to
become less carbon intensive, pathways which recover energy (AD, controlled combustion, and
landfill) will see reduced GWP benefits while other pathways that only use energy (e.g., animal
feed, composting) will see decreased GWP impacts.
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CHAPTER 4
CIRCULARITY ASSESSMENT
Circularity is a central component of EPA's vision for materials and wasted food management. In contrast
to a traditional linear (i.e., "take-make-use-dispose") economy, a circular economy is one where economic
growth can be decoupled from resource extraction by capturing greater value from existing products and
materials (Figure 4-1). Many organizations and governments have adopted circularity principles over the
last decade, including the United Nations, the World Economic Forum, China, and the European Union
(Bocken et al. 2016; Geissdoerfer et al. 2017). In the U.S., the Save Our Seas Act 2.0 directed EPA to
promote and support circular economy strategies for post-consumer materials management (U.S.
Congress 2020).
Linear VS. Circular Economy
FIGURE 4-1. COMPARING A LINEAR ECONOMY AND A CIRCULAR ECONOMY
The concept of circularity draws from several schools of thought, including industrial ecology, cradle-to-
cradle, regenerative design, and others (Geissdoerfer et al. 2017), and a review of the development of a
circular economy is provided elsewhere (Geissdoerfer et al. 2017; Murray et al. 2017; Geisendorf and
Pietrulla 2018). There are now over 100 definitions of circular economy (Elia et al. 2017; Geissdoerfer et
al. 2017; Kirchherr et al. 2017; Do et al. 2021; Tanveer et al. 2021; WEF 2023) and over 60 metrics
(Parchomenko et al. 2019; De Pascale et al. 2021) to evaluate circularity in the scientific literature. The
definition of a circular economy has evolved over the last twenty years, from simply meaning closed loop
manufacturing (where wastes become inputs) to including concepts of restoration and regeneration of
ecosystems (Geissdoerfer et al. 2017; Geisendorf and Pietrulla 2018; Tanveer et al. 2021).
The Ellen MacArthur Foundation has developed some of the most comprehensive and cited resources for
outlining, implementing, and assessing circularity, including the ReSOLVE framework which focuses on
optimizing systems to reduce waste, maintaining value of products and materials, keeping materials
within the system by which they were created, designing out negative externalities, and preserving and
regenerating natural systems (Ellen MacArthur Foundation 2013). In the Ellen MacArthur Foundation
model, a circular economy seeks to address natural capital challenges (e.g., soil degradation, biodiversity
loss, and freshwater quality and depletion), resource challenges (e.g., nutrient losses), and system
challenges (e.g., emissions and limited carbon carrying capacity).
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In the Save Our Seas Act 2.0 (U.S. Congress 2020), which guides this analysis, a circular economy is
defined, in line with descriptions supplied by the Ellen Macarthur Foundation, as one that "uses a
systems-focused approach and involves industrial processes and economic activities that:
are restorative or regenerative by design;
enable resources used in such processes and activities to maintain their highest values for as
long as possible; and
aim for the elimination of waste through the superior design of materials, products, and systems
(including business models)".
These principles can apply to both technical (i.e., engineered or industrial) systems, such as electronics
manufacturing, and biological systems, such as the food system (Ellen MacArthur Foundation 2013). In
the case of the food system, analyses must account for food's essential role in human life—i.e., that its
primary purpose is to be consumed—and its perishability. While technical products and their components
(e.g., electronics, appliances) in a circular economy should remain in the economy for as long as possible
through repair, reuse, re-manufacture, and recycling, biological products (including food) should instead
be designed to re-enter the environment safely to restore the ecosystem from which they were withdrawn
(Do etal. 2021).
This analysis does not address the entirety of a circular food system. Instead, it focuses on the potential
contributions of the wasted food pathways, as defined earlier in this report (Table 1-1), to the circularity of
the food system. The generation and management of wasted food have been identified as key stages of
the food system where circular economy principles can be implemented (Jurgilevich et al. 2016). The
report will exclude other parts of the food system, such as the management and effects of human waste
from consuming food (e.g., outputs from respiration or excretion).
4.1 Circularity Themes
The key circularity themes used to evaluate the wasted food pathways in this report were derived from
the Save Our Seas Act 2.0 and informed by the Ellen MacArthur Foundation ReSOLVE framework and
the scientific literature regarding circularity of biological systems (Ellen MacArthur Foundation 2013; Ellen
Macarthur Foundation 2019; U.S. Congress 2020; Do et al. 2021; Tanveer et al. 2021). In this chapter,
the selected themes—waste prevention, value, purity, and regeneration— are utilized to determine a
ranking of the wasted food pathways, by degree of circularity.
Definitions of the key circularity themes are presented in Table 4-1 and further expanded in the following
sections. While the themes are presented here as four distinct concepts, it should be noted that they often
overlap and relate. While waste prevention is preferred, some amount of wasted food is inevitable. In a
circular economy, when waste cannot be prevented, waste outputs should maintain their highest potential
value, stay free of contaminants, and help to regenerate ecosystems.
TABLE 4-1. KEY CIRCULARITY THEMES
Circularity Theme
Definition
Waste Prevention
Waste is minimized through improvements in system efficiencies.
Value
Outputs maintain their highest potential value.
Purity
Outputs stay free of contaminants to enable reuse.
Regeneration
Outputs help to regenerate ecosystems.
Waste Prevention
Preventing waste is paramount to circularity and, within the food system, it can occur in a variety of ways,
such as source reduction, donation, or upcycling. All three of these pathways offer the potential to reduce
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the amount of food production required to feed a population, thus reducing the negative externalities
associated with food production (Sherwood 2020), including greenhouse gas emissions and climate
change, consumption and degradation of freshwater resources, loss of biodiversity and ecosystem
services, and degradation of soil health and air quality. According to EPA (U.S. EPA 2021c), the
production, processing, and distribution of food that is ultimately wasted in the U.S. each year embodies:
140 million acres of agricultural land - an area the size of California and New York combined.
5.9 trillion gallons of blue water - equal to annual water use of 50 million American homes.
778 million pounds of pesticides.
14 billion pounds of fertilizer - enough to grow all the plant-based foods produced each year in
the United States for domestic consumption.
664 billion kWh energy - enough to power more than 50 million U.S. homes for a year.
170 million MTCChe GHG emissions (excluding landfill emissions) - equal to the annual CO2
emissions of 42 coal-fired power plants.
Value
In a circular economy, outputs should maintain their highest potential value. The highest value of food is
as sustenance for humans (directly or indirectly through feeding of livestock). Once food is not consumed,
the highest value is dependent on the context for decision making and could be evaluated in numerous
ways including economically, culturally, nutritionally, or physically.
Valuable materials such as the nutrients most relevant to agriculture - nitrogen, phosphorus, and
potassium —can be recovered from wasted food and used as fertilizers. Synthetic nitrogen fertilizers
currently consume one percent of global energy demand (Sherwood 2020), and anthropogenic
interference with the nitrogen cycle has already exceeded estimated planetary boundaries (Steffen et al.
2015; Cobo et al. 2018). For instance, in some areas of the globe, over-application of N fertilizer made
possible by the N fertilizer synthesis process has led to an imbalance in the N available to plants and the
N those plants need and can take up, resulting in runoff of excess N. Also, phosphorus is a limited
resource (i.e., it cannot be synthesized like nitrogen fertilizers), and viable reserves are expected to be
depleted and limit food production within 100 years (Cobo et al. 2018; Alewell et al. 2020; Sherwood
2020). Biomass from wasted food can be used as an alternative feedstock to produce nitrogen and
phosphorus fertilizers, reducing fossil fuel use and supplementing the global supply of phosphorus.
In a circular economy, material recovery is generally valued over energy recovery (Potting et al. 2017; Do
et al. 2021) due to the embodied value in materials and the global transition towards more renewable
energy sources. As the energy mix becomes less emissions-intensive, the value of providing alternative
energy from wasted food will decrease; however, the fossil-fuel inputs required as feedstock for
manufacturing synthetic nitrogen fertilizer, the limited global phosphorus supply, and reliance on soils for
food production, means there will continue to be high value in recovering nutrients from wasted food. In
this analysis, nutrient retention is considered more valuable than energy recovery from wasted food,
especially over the long term. Carbon is another component of wasted food that can be recovered and
applied to soil to build organic matter and store carbon in soils, and this use for the carbon in wasted food
is valued more highly in this analysis than carbon's use to create renewable energy. Nutrient cycling in
soils is reliant on carbon as an energy source for microbes and a factor in soil structure, linking carbon
recovery with nutrient recovery in wasted food pathways that can contribute to soil health. This was
discussed in Section 3.6 on soil health and is further discussed with the regeneration theme in this
chapter.
Circularity also credits "cascading uses" (i.e., the sequential and consecutive use of resources). For
example, one could remove valuable components from wasted food and upcycle them into new food for
human consumption, then process the remaining mass of wasted food through composting to recover
nutrients like nitrogen and phosphorus.
Purity
The purity (or "pure circle") theme of circularity stresses the prevention of physical and/or chemical
contamination so that materials can be reused more easily. Physical contamination includes things like
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plastic, metal or glass. Examples of chemical contaminants include pharmaceuticals or persistent organic
pollutants like per- and polyfluoroalkyl substances (PFAS). This concept is highly related to value, as
contamination may prevent the beneficial use of recovered materials or limit the range of possible uses.
For the purposes of this analysis, potential contaminants, such as pesticides or PFAS, introduced into
food before it becomes surplus or waste (e.g., during the production stage) are considered out of scope.
However, potential contaminants may also be introduced to wasted food streams accidentally or
intentionally as they are collected and managed. For example, non-compostable packaging may be
accidentally placed into a wasted food stream, or wasted food may intentionally be co-digested with
wastewater solids - and either of those scenarios may introduce a contaminant like PFAS or plastics to
the wasted food stream (U.S. EPA 2021 e; U.S. EPA 2021 f). In addition to making reuse more difficult,
physical and chemical contaminants in the food waste stream can reduce life cycle environmental
performance of a wasted food pathway by requiring additional energy use for pre-treatment, reducing the
amount of food waste recycled, generating technical problems during recycling, and contaminating soils
where recycled outputs are applied (Le Pera et al. 2023). Some wasted food pathways can screen out,
destroy, inactivate, or immobilize contaminants, reducing potential risks from contamination. Likewise,
improving sorting out of physical contaminants can improve the life cycle environmental performance of a
wasted food pathway (Angouria-Tsorochidou et al. 2023).
Regeneration
The theme of regeneration is critical to circularity; however, recent reviews found inconsistencies in the
definition and use of the term (Morseletto 2020; Schreefel et al. 2020). This analysis will rely on the
definition of regeneration from Elevitch et al. (2018), which is consistent with many of the common
themes identified by the reviews. Regeneration is an "approach that has the capacity for self-renewal and
resiliency, contributes to soil health, increases water percolation and retention, enhances and conserves
biodiversity, and sequesters carbon." This analysis will focus on the potential contributions of the wasted
food pathways to regeneration; broader agricultural practices are considered out of scope.
Regeneration may occur through the wasted food pathways by the addition of slow-release nutrients or
carbon to the soil. Carbon can help to build soil organic matter (SOM), increase water holding capacity,
and enhance nutrient cycling. Most agricultural soils have lost significant portions - 30-75% - of soil
organic carbon (Lai et al. 2007), which leads to increased risk of erosion and compaction and less
resistance to drought. Soil amendments derived from wasted food can supply valuable organic carbon to
soils and help restore the health and functionality of agricultural lands.
Wasted food pathways which promote regeneration can improve the resilience of agricultural systems in
the face of climate change through improved soil health. Soil moisture conservation, reclamation of
degraded soils, and soil carbon management are effective practices for climate change mitigation and
adaptation (IPCC 2023).
Other Circularity Themes
The four circularity themes applied in this chapter were chosen based upon their connection to the
definitions of circularity from the Save Our Seas Act 2.0 and the Ellen Macarthur Foundation and their
applicability to biological systems. Other circularity criteria presented in the literature (Do et al. 2021) that
are not easily applicable to the food system or to wasted food management were not applied. For
example, the concept of longevity (i.e., keeping a product in use for as long as possible) does not apply to
a perishable and consumable product like food.
In addition, some definitions of circularity call out the need to design out negative externalities from
systems. Potting (2017) offers the "rule of thumb" that more circularity equals more environmental benefit,
since a primary goal of circularity is to reduce the consumption of natural resources and materials and
minimize waste; however, circularity does not guarantee positive environmental results. For example,
recovering materials can require additional water, energy or transportation (Del Borghi et al. 2020). LCA
can help to identify and weigh some of these unintended or indirect consequences. The results of this
circularity assessment will be used in conjunction with the LCA results in the previous chapter, which may
capture additional externalities, to inform the conclusions of this report.
Chapter 4. Circularity Assessment
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4.2 Methodology
Although there are quantitative methods for evaluating circularity, these are nascent for biological cycles
and food (Elia et al. 2017; Moraga et al. 2019). A systematic search of the literature provided no
comparisons of wasted food management pathways using quantitative circularity metrics. Therefore, this
report qualitatively evaluates the relationships between the pathways and key themes in circularity
discussed above. The assessment relies on the literature search described in detail in Appendix A.
Alternative qualitative methods and accompanying results are discussed in Section 4.7.
The following sections aim to identify the connections between the four key themes of circularity and the
wasted food pathways. The analysis focuses on the environmental aspects of circularity and does not
consider social and economic factors. Where possible, the analysis considers the specific effect of
wasted food in each pathway (e.g., incinerating wasted food rather than incinerating MSWor another
MSW component such as plastics) rather than the aggregate circularity of the pathway. In Section 4.9 the
findings are synthesized to develop a novel circularity hierarchy based on each pathway's agreement with
the circularity themes.
Only source reduction, donation, and upcycling minimize the generation of wasted food that will not be
directly eaten by humans. The other pathways offer alternative uses for wasted food. Source reduction,
by definition, prevents the generation of wasted food and more closely aligns supply and demand.
Donation and upcycling aim to ensure food is still consumed by humans, although some amount of
wasted food is inevitable in these pathways (e.g., food spoiling at food banks or in recipients' homes).
Since source reduction, donation and upcycling minimize the need for waste management strategies,
only the remaining pathways will be examined in connection to the other circularity themes.
If crops would ultimately be wasted (i.e., not sold and consumed), then the unharvested/plowed in
pathway offers an opportunity to prevent downstream environmental impacts from processing, packaging
and distributing food. However, unlike the three pathways noted above, it cannot reduce food production
or its more substantial environmental impacts. Therefore, unharvested/plowed in is grouped with the
remaining pathways and is less circular than donation or upcycling of crops which feed people.
Figure 4-2 provides a ranking of pathways based on their alignment with the waste prevention theme of
circularity.
I Source Reduction
Donation
4.3 Waste Prevention
Upcycling
CD
>
CD
CD
>
CD
Anaerobic Digestion
Animal Feed
Composting
Incineration
Land Application
Landfill
Sewer/WWT
Unharvested/Plowed In
most circular
O 1 least circular
FIGURE 4-2. WASTE PREVENTION: ALIGNMENT OF WASTED FOOD PATHWAYS
Within lower tier the pathways are presented in alphabetical order.
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4.4 Value
Nourishing Humans
Food grown for human consumption is most valuable when it can be used to provide human sustenance.
Transforming wasted food into animal feed indirectly maintains food's original function (e.g., energy,
nutrients) by providing animal feed to livestock production, which produces food for human consumption.
The circularity of the animal feed pathway is endorsed by researchers supporting the World Economic
Forum, who included the "use of only biomass unsuited for direct human consumption for animal feed" as
one of their three core principles for a circular food system (WEF 2023).
Recovering Nutrients
When food can no longer be used to nourish humans or animals, circularity generally values the recovery
of material over energy recovery. In this analysis, pathways that recover organic matter and critical
nutrients, using them as fertilizer or soil amendments, are considered more circular than those that
produce only energy.
Five pathways recover organic matter and valuable nutrients from wasted food that can be applied to land
as fertilizers or soil amendments - AD, composting, land application, sewer/WWT, and
unharvested/plowed in. Wasted food can be a source of various critical macro- and micro nutrients
required for plant growth, but it is especially rich in nitrogen. These pathways also recover carbon, which
is critical for nutrient cycling and retention as well as other soil functions. Carbon recovery from wasted
food is discussed further in Section 4.6.
Table 4-2 provides a summary of the nutrient-rich outputs produced by these five pathways, along with
the potential destinations of each output, for reference.
To provide value (and thus qualify as circular), the nutrients recovered in these pathways must be
beneficially used, rather than disposed of. Note that disposal by landfill and controlled combustion are
potential destinations for recovered nutrients from two of the five pathways (AD and sewer/WWT).
Three pathways provide direct nutrient recovery. The unharvested/plowed in pathway leaves unharvested
crops in the field, and the land application pathway applies waste from the food processing sector to
agricultural land. Compost (i.e., the end product of the composting pathway) is also predominantly land
applied. According to a survey of U.S. composters, 99% compost is used in ways that utilize recovered
nutrients (e.g., landscaping, agriculture), with remaining 1% applied as landfill cover (U.S. Composting
Council 2021).
The other two pathways that recover nutrients -AD and sewer/WWT—may use or dispose of nutrient
outputs. As a reminder, the nutrient-rich outputs from stand-alone AD facilities and AD systems on farms
that digest or co-digest wasted food are called digestate, whereas the nutrient-rich outputs from AD
facilities that co-digest wasted food at water resource recovery facilities (WRRFs) are called biosolids.
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TABLE 4-2. DESTINATIONS FOR NUTRIENT OUTPUTS FROM WASTED FOOD PATHWAYS
Pathway
Nutrient Output
Alternative Destinations, Beyond
Direct Application to Soil*
Anaerobic Digestion
(stand-alone and on-
farm digesters)
Digestate
Animal Bedding
Composting
Controlled Combustion
Landfill
Sewer/WWT
Anaerobic Digestion
(co-digestion at WRRFs)
Biosolids
Composting
Controlled Combustion
Landfill
Sewer/WWT** (re-circulated and/or
discharged in effluent)
Composting
Compost
(including compost made from
digestate or biosolids)
~
Land Application
Raw Wasted food from food
processing industry
-
Sewer/WWT
(with or without AD)
Biosolids
Composting
Controlled Combustion
Landfill
Sewer/WWT** (re-circulated and/or
discharged in effluent)
Unharvested/Plowed In
Crops
-
Pathways noted in green are beneficial uses of nutrients.
*Digestate or biosolids may receive treatment other than and/or in addition to composting before direct application to
soil.
**Sewer/WWT can be beneficial use if discharge used as irrigation water.
The sewer/WWT pathway also produces biosolids from organic waste (including wasted food) sent down
the drain and through the sewer to a WRRF. Wastewater solids from the sewer/WWT pathway may
undergo a variety of treatments, including AD, aerobic digestion, lime stabilization, composting, and
thermal drying, among others. For the sewer/WWT pathway, a portion of nutrients from wasted food sent
down the drain is separated from wastewater solids into the liquid effluent at a WRRF, which is treated
prior to reuse or discharge.
Digestate includes solid and liquid fractions which are often, but not always, separated after digestion (i.e.
through dewatering), with the majority of nitrogen contained in the liquid fraction (Havukainen and Dace
2023). In 2021, the EPA performed a voluntary survey of AD facilities in the U.S. that process wasted
food and included questions about the use of solid and liquid digestate fractions from their facilities (U.S.
EPA 2023). Respondents shared that the solid fraction may be beneficially used or disposed of, with
disposal more likely at WRRFs than at stand-alone or on-farm digesters. The liquid fraction is typically
applied to agricultural land at on-farm digesters (100% of facilities reported this as one of their practices),
whereas it may be applied to land or discharged to a WRRF by stand-alone digesters (33% and 57%,
respectively of stand-alone facilities reported each practice as one method for handling their digestate)
(U.S. EPA 2023). WRRFs most often recirculate the liquid fraction of digestate (i.e., dewatering liquid)
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back through the wastewater treatment process. After discharge to and/or treatment by a WRRF,
nutrients, now in biosolids or effluent, may be beneficially used or disposed of, as discussed below.
Researchers have noted that digestate utilization is currently a "bottleneck" for development of biogas
industry (Lu and Xu 2021).
Biosolids are wastewater solids/sewage sludge - the solid fraction of the final product of wastewater
treatment (effluent is the liquid) - that have been treated (with or without AD) to meet federal standards
for contaminants and pathogens, allowing for their beneficial use. Biosolids treated to higher quality (i.e.,
Class A or EQ) have fewer restrictions on their use. In EPA's AD survey, 16% of reporting AD facilities at
WRRFs indicated that they produce Class A biosolids, and 84% reported producing Class B biosolids
(U.S. EPA 2023). To the extent that biosolids are not used as fertilizers or soil amendments, the circularity
of this pathway is limited. In 2018, 45% of biosolids generated in the U.S. (including those that are
produced at facilities that do not co-digest wasted food with wastewater solids) were sent to landfill63 or
controlled combustion rather than being beneficially used (Beecheret al. 2022). Nationwide, treatment of
biosolids to Class A quality (rather than Class B) is increasing, which may improve the circularity of this
pathway in the future (Beecher et al. 2022).
Wasted food, compost, digestate and biosolids may all be applied to agricultural land to provide nutrients
to the soil and improve soil health. These materials also have many uses outside of agriculture as well,
such as land restoration or reclamation (e.g., at abandoned mine sites) and green infrastructure. For
agricultural land, nutrient application should be aligned with a crop's nutrients needs, most often nitrogen.
The nutrient content in wasted food can be a challenge for management pathways. For example, wasted
food contains more nitrogen than wastewater solids and increases the nutrient load in biosolids and
effluent from wastewater treatment processes when added through sewers or co-digested at a WRRF.
One limitation to the increased use of sewer/WWT and AD at WRRFs to process wasted food is the ability
of wastewater treatment technologies to manage additional nutrient loads, especially in regions with
concerns of nutrient loading to marine and freshwater ecosystems. Emerging technologies that "strip"
nutrients during the wastewater treatment or AD process can help to control the amount of nitrogen and
phosphorus in the final materials and produce concentrated fertilizers. Stripped, concentrated nutrients
are then sold and land applied - perhaps mixed with other plant macro- or micro-nutrients - as
substitutes for synthetically-derived nutrients.
In the sewer/WWT pathway, two factors reduce the total nutrient recovery/content of biosolids (relative to
original feedstocks, including wasted food. First, nitrogen and phosphorus are removed during secondary
wastewater treatment to limit nutrients in the effluent and thus potential runoff to surface waters (Morris et
al. 2014). Second, some nutrients remain dissolved in effluent (another potential method of nutrient
recovery) and do not become a part of the biosolids. The effluent is discharged or used as irrigation water
in agriculture or landscaping and can be source of nutrients. One study in Italy showed that significant
portions of N and P required by grapes and olives could be supplied by irrigating with reclaimed water
from 11 different WRRFs (Vivaldi et al. 2022). In addition to nitrogen and phosphorus, effluent from
WRRFs contains potassium and other salts that plants need to grow (Sullivan et al. 2021). While nutrient
recovery is not the primary goal of WRRF effluent reuse, the nutrient concentrations are considered when
also applying fertilizers or organic soil amendments to avoid exceeding crop needs, thus potentially
reducing synthetic fertilizer use.
Recovering Other Materials
The solid fraction of digestate can be processed into animal bedding (in lieu of land application), which,
after use, will be managed with manure and urine (and may ultimately be processed through AD or
composting).
Controlled combustion results in a material output (ash) that can be beneficially used in certain
circumstances; however, this is currently infrequent in the United States. Ash is often contaminated with
heavy metals, dioxins, and other pollutants. There are two types of ash - bottom ash and fly ash - and
both are generally landfilled (Cho et al. 2020). Bottom ash accounts for the majority of incinerator ash and
can be used as an aggregate in construction materials (Funari et al. 2017; U.S. EPA 2023c). Metals may
be recovered from ash, but these are typically not derived from wasted food feedstock.
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Other pathways for wasted food are emerging to create chemicals, bioplastics and other materials, and
these pathways would also be considered circular.
Recovering Energy
Three pathways recover energy from wasted food - AD, controlled combustion, and landfill - with varying
efficiency. Generally speaking, AD produces the most energy per ton of wasted food of the three
pathways. Wasted food's methane potential, biodegradability, and high-water content make it an ideal
substrate for AD (Momayez et al. 2019). When added to AD systems at WRRFs or on-farm AD systems
and co-digested with wastewater solids or manure, respectively, wasted food has been shown to
synergistically increase biogas production (Kim et al. 2017; Baek et al. 2020). AD can recover energy and
nutrients, demonstrating the cascading uses (i.e., the sequential and consecutive use of resources)
principle promoted by circularity. However, energy recovery may be the primary intention of the facility
(Beghin-Tanneau et al. 2019) (e.g., due to economics), and thus the nutrient content of wasted food (in
digestate) may be underutilized. Most AD research has focused on optimizing energy production, leaving
digestate use as a secondary concern (Cesaro 2021). To meet objectives of a circular economy there
must also be valorization (i.e., beneficial use) of the digestate (Cesaro 2021).
Energy is also recovered by controlled combustion and landfill pathways. However, the energy recovery
efficiency tends to be lower than with AD. The moisture content of wasted food makes it less ideal for
energy recovery from controlled combustion than from AD (Klinglmair and Thomsen 2020; Lu and Xu
2021). Landfills are typically considered to be the end points of linear systems; they bury waste and fail to
beneficially reuse nutrients. In this assessment, we consider only landfills that recover energy from waste
decomposition; however, as mentioned earlier in report, wasted food may decompose prior to the
placement of landfill gas capture systems, resulting in more fugitive methane emissions than captured
energy.
Figure 4-3 provides a ranking of wasted food pathways based on their alignment with the value theme of
circularity.
O Animal Feed
Within each tier the pathways are presented in alphabetical order. Sewer/WWT with incineration or landfill of biosolids that also
does not include AD would rank below the bottom tier here, as it does not recover energy. Landfills and controlled combustion
without energy recovery are not included as they are out of scope for this report. Since source reduction, donation and upcycling
minimize the need for waste management strategies, they are not ranked with regard to the other circularity themes (value, purity
and regeneration).
Chapter 4. Circularity Assessment 4-9
Anaerobic Digestion, with beneficial use of digestate/biosolids
Composting
Land Application
Sewer/WWT, with beneficial use of biosolids
Unharvested/Plowed In
Anaerobic Digestion, with incineration or landfill of digestate/biosolids
Incineration
Landfill
Sewer/WWT, with incineration or landfill of biosolids
FIGURE 4-3. VALUE: ALIGNMENT OF WASTED FOOD PATHWAYS
-------
4.5 Purity
Pure Circle
Pathways which manage only wasted food (i.e., no co-mingled wastes) can most effectively maintain a
"pure circle" limiting physical and chemical contamination. The unharvested/plowed in pathway avoids
contamination by leaving wasted food in its original location for tilling or grazing. The animal feed pathway
applies strict health and safety requirements to ensure wasted food is safe for animals to eat. In addition,
wasted food is often sterilized to ensure its safety for livestock. The land application pathway preserves
purity by managing only wasted food from the food processing sector. This waste stream tends to be
consistent and homogenous with little contamination since the wasted food is typically captured prior to
packaging or distribution.
Stand-alone AD facilities can also maintain a pure circle. Some stand-alone AD facilities (often called
industry-designated digesters) are designed and sited to manage wasted food streams from food
processing facilities and do not accept other wastes, while other facilities (called multi-source digesters)
accept wasted food and other wastes from a variety of sources. Digestate made only from wasted food
has fewer pathogens and heavy metals than digestate from manure, for example (O'Connor et al. 2021).
Wasted food digestates typically do not require sanitation before land application, due to low
contamination levels (Dutta et al. 2021). If digesters accept additional non-wasted food streams, they can
face challenges of contamination described below.
Potential for Contamination
Beyond the pathways discussed above, the degree of purity maintained is more complex to judge. Purity
is highly connected to value, as more beneficial uses of material outputs are possible with lower
contamination. Thus, we will examine the sources of and potential remedies for physical and chemical
contamination within the four remaining pathways that recover materials - AD (except industry-dedicated
digesters), composting, controlled combustion, and sewer/WWT. Landfills will not be considered in this
section since they do not recover material for reuse.
Contaminants may be introduced into wasted food streams when mixed with other waste streams during
collection and/or management. Wasted food streams from sources other than the food processing
industry are more likely to contain contaminants.
When wasted food is collected, it can be source-separated (i.e., separated by the generator) and
separately collected, or it can be collected as part of a mixed waste stream like MSW. Wasted food may
also be mechanically separated from MSW after collection. Generally, source-separated wasted food has
less chemical and physical contamination than mechanically separated waste, which has less
contamination than mixed wastes such as MSW (Thakali and MacRae 2021; Le Pera et al. 2022a) and
can produce a higher quality product (Angouria-Tsorochidou et al. 2023). However, source-separated
streams can still contain contaminants. Items like non-compostable packaging or utensils may be placed
into the wasted food stream accidentally and may introduce contaminants such as PFAS or plastics (U.S.
EPA 2021e; U.S. EPA 2021 f). In addition, food waste, even when source-separated from other waste
streams, may still be packaged and need to be de-packaged before processing.
The composting and AD pathways typically accept only source-separated (i.e., by the generator) and
separately collected wasted food streams, in order to avoid contamination with and from other MSW.
These pathways also commonly pre-treat wasted food streams through screening, sorting or mechanical
de-packaging to remove physical contaminants like (non-compostable) packaging.
In contrast, the other two pathways - sewer/WWT and controlled combustion - accept wasted food only
as part of a mixed waste stream. The sewer/WWT pathway receives and processes wastewater
(including food sent down the sink drain) and controlled combustion receives and processes MSW
(including wasted food thrown out with the trash).
In the composting, AD (except industry-dedicated digesters), sewer/WWT, and controlled combustion
pathways, wasted food is intentionally mixed with other waste streams for processing, which can
introduce chemical contaminants. For example, composting requires a mix of nitrogen-rich (e.g., wasted
food) and carbon-rich (e.g., wood waste or yard trim) feedstocks, and, except in certain specialized
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systems, compost cannot be made from wasted food alone. To evaluate the risks from contamination,
one must consider the types of waste with which the wasted food is mixed, the contaminants commonly
found in those wastes, each pathway's ability to mitigate those contaminants (including possibility of post-
treatment), and the specific application of the recovered material. See Table 4-3 for a list of wastes
typically managed with wasted food and the common contaminants associated with them.
TABLE 4-3. WASTE STREAMS COMMONLY MANAGED WITH WASTED FOOD
Waste
Potential Contaminants
Pathway that may accept it
Wood waste and yard trim
(aka green waste)
Persistent herbicides
Composting
Animal manure
(including feces, urine, and
animal bedding)
Pathogens
Persistent herbicides Pharmaceuticals
AD (on-farm and stand-
alone)
Composting
Wastewater solids
(aka sewage sludge)
Heavy metals
Microplastics
Pathogens
Persistent organic pollutants (including
PFAS)
Pharmaceuticals
AD (at WRRF)
Composting
Sewer/WWT
Digestate
(Depends on source of digestate; may
include contaminants associated with
wastewater solids or manure)
Composting
Biosolids
(Same as wastewater solids above,
though biosolids will have by definition
received some treatment and be labeled
by Class depending on level of pathogen
treatment)
Composting
MSW
Heavy metals
Pathogens
Persistent organic pollutants (including
PFAS)
Pharmaceuticals
Plastic
Controlled Combustion
Table includes both physical and chemical contaminants. Table does not include landfill pathway since materials are
not recovered.
Data Sources: (Goss etal. 2013; Urra et al. 2019; Thakali and MacRae 2021; U.S. EPA2021e; U.S. EPA2021f)
In general, wasted food streams are less contaminated than wastewater solids or manure (Lu and Xu
2021; O'Connor et al. 2021; O'Connor et al. 2022b); thus, keeping wasted food separate from these
wastes enhances purity. Wasted food is most often composted with yard trim and wood chips, given their
complementary composition (wasted food is nitrogen-rich, while yard trim and wood chips are carbon-
rich) (Dutta et al. 2021); whereas manure and wastewater solids are nitrogen-rich like wasted food. In the
AD pathway, feedstocks are dependent on the type of digester. On-farm digesters process manure, while
digesters at WRRFs process wastewater solids. Stand-alone AD facilities may process only wasted food
or accept other feedstocks.
Each of the waste streams used as feedstocks in the wasted food management pathways brings its own
chemical contaminant risks. Chemical contaminants in feedstocks for soil amendments include PFAS and
other persistent organic pollutants, heavy metals, persistent herbicides, pathogens, and pharmaceuticals
(Goss et al. 2013; Urra et al. 2019; Thakali and MacRae 2021).
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PFAS and heavy metals may be present in wastewater solids and biosolids because WRRFs receive
wastes that contain traces of products used in daily life from homes, businesses, and industries. WRRFs
may also receive higher concentrations of PFAS from industrial wastewaters. A literature review by EPA
demonstrated that PFAS contamination was generally higher in biosolids and compost made from
biosolids than in compost made from wasted food and green waste (U.S. EPA 2021 e). When applied to
land, PFAS has the potential to be taken up by plants and crops and/or leach into groundwater; however,
a full risk assessment of PFAS-contaminated biosolids or compost applied to land is not yet available.
There is no evidence in the literature that any wasted food management pathway destroys PFAS (U.S.
EPA 2021 e).
Compost and digestate that contain persistent herbicides (e.g., clopyralid, aminocyclopyrachlor, and
picloram) can curb growth of certain plants, such as those in the nitrogen-fixing legume family and
nightshade family. Documented cases of persistent herbicides in compost have identified green waste,
manure or hay as the source (U.S. EPA 2021 e).
Pathogens and pharmaceuticals may be found in manure and in wastewater solids and biosolids. By
regulation, biosolids have been treated to meet federal standards for pathogen levels. Class A biosolids
have undergone a Process to Further Reduce Pathogens (PFRP), whereas Class B biosolids generally
contain low levels of pathogens. Pharmaceuticals found in manure and wastewater solids include
antibiotics and associated antibiotic-resistant genes (ARGs) and bacteria (ARBs) which can persist into
crops treated with contaminated soil amendments (Urra et al. 2019).
Composting is recognized for its ability to destroy many pathogens, suppress plant disease and weed
seeds, and decompose many chemical contaminants such as pesticides, pharmaceuticals, and persistent
organic pollutants through high temperatures, biological activity, and the maturation process (O'Connor et
al. 2021; Thakali and MacRae 2021; Le Pera et al. 2022a; Stehouwer et al. 2022). For example,
composting promotes degradation and/or mineralization of organic pollutants by providing nutrients and
energy to microbial populations (Urra et al. 2019). Composting also decreases concentration of many
pesticides, with the exception of persistent herbicides. Composting can degrade antibiotic residues, and
research suggests it may also decrease the bioavailability of remaining residues. Composting may
decrease presence of ARB and ARGs (Urra et al. 2019), but additional research is needed. Composting
can also reduce the bioavailability of heavy metals by forming chemically stable metallo-humic complexes
and aggregates (Goss et al. 2013; Urra et al. 2019; O'Connor et al. 2021; Thakali and MacRae 2021).
Thermophilic (but not mesophilic) AD is able to achieve a similar degree of decontamination as
composting for many contaminants (Urra et al. 2019; O'Connor et al. 2021; Thakali and MacRae 2021);
however, the majority of AD in the United States is run at mesophilic conditions (U.S. EPA 2023) which
can reduce contamination to a lesser degree than thermophilic AD (Urra et al. 2019). According to EPA's
recent survey, 17% reporting anaerobic digesters operate at thermophilic conditions (U.S. EPA 2023b).
Post-treatment of digestate can also help to remove contaminants (e.g., pasteurization can kill pathogens
(Thakali and MacRae 2021)).
The decontamination abilities of composting extend to the composting of digestate and biosolids (Le Pera
et al. 2022b; Le Pera et al. 2022a). For example, Class A Exceptional Quality (EQ) biosolids (with less
contamination than Class A biosolids) are typically created through composting. Class A EQ biosolids do
not have restrictions on their use, due to their high level of treatment and the virtual absence of
pathogens and pollutants.
In addition to AD and composting, other treatment methods exist for wastewater solids and affect the
quality and purity of the final product. Aerobic digestion (digestion in an oxygen-rich environment),
alkaline stabilization (adding lime), and drying (by air-drying, rotary drum, or thermal drying) are a few
methods by which wastewater solids may be stabilized to reach Class B or Class A standards. For
biosolids to be beneficially used (i.e., as fertilizer or soil amendment), they must not only be Class A or B,
but also must not exceed regulatory concentration limits for heavy metals.
Controlled combustion can also destroy many organic contaminants, but not heavy metals (e.g., from
MSW), which remain in the waste output (ash) and make it unlikely to be reused. Risk assessments have
not yet been done on many of these contaminants in soil amendments for land application. Potential
pathways for human exposure to contaminants in soil amendments include uptake in crops and transport
in air (as bioaerosol or particulate matter) or into surface or groundwater (Goss et al. 2013).
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Figure 4-4 provides a ranking of wasted food pathways based on their alignment with the purity theme of
circularity.
O
Anaerobic Digestion (stand-alone, industry-dedicated)
Animal Feed
Land Application
Unharvested/Plowed In
O
Anaerobic Digestion, with composting
Composting
Sewer/WWT, with composting
Anaerobic Digestion (on-farm and at WRRF), without composting
Incineration
Landfill
Sewer/WWT, without composting
most circular
¦O ^
O ' least circular
FIGURE 4-4. PURITY: ALIGNMENT OF WASTED FOOD PATHWAYS
Within each tier the pathways are presented in alphabetical order.
Ranking considers typical waste collection practices (e.g., source separation, mechanical separation, or no separation of wasted
food streams) and co-waste streams for wasted food in each pathway as well as the decontamination abilities of each pathway.
Since source reduction, donation and upcycling minimize the need for waste management strategies, they are not ranked with
regard to the other circularity themes (value, purity and regeneration).
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4.6 Regeneration
The nutrient-rich materials from the wasted food pathways—compost, biosolids, digestate,
unharvested/plowed in crops, and land application—range in composition and structure. While all the
materials discussed here provide benefits to soil (O'Connor et al. 2021), some promote regeneration of
ecosystems to a greater degree than others. This discussion builds upon that in Section 4.4, where we
discussed nutrient (NPK) recovery and the beneficial use (or disposal) of recovered nutrients. It also
connects to the discussion of soil health in Chapter 3.6, where the definition of soil health included
enhancing water storage, promoting good water quality, maintaining or enhancing soil biodiversity and
sequestering carbon, in addition to providing recycled organic fertilizers and soil amendments and
avoiding harmful contaminants, pathogens, and pests (Lehmann et al., (2020).
In addition to providing nutrients for immediate use by plants, these nutrient-rich materials can, to varying
degrees, contribute to ecosystem regeneration by providing slow-release nutrients and organic matter,
improving soil health, increasing water percolation and retention, enhancing and conserving biodiversity,
and sequestering carbon.
All the materials derived from wasted food build soil organic matter, which is an important factor in soil
fertility (promoting nutrient cycling), soil structure (aggregate stability, bulk density, porosity) and carbon
sequestration (Morris et al. 2014). While the benefits of land applying any material will depend on soil
type, crop type, timing within the growing season, and climatic conditions (Urra et al. 2019), considering
these variances is beyond the scope of this analysis. In addition, soil amendments may be applied to the
surface of soils or incorporated into soils (e.g., through tilling or injection) and differentiating effects of
these methods is outside the scope of this assessment as well.
Sequestration of carbon results when the rate of carbon addition is higher than the rate of carbon
mineralization. Organic amendments add soil carbon directly through application, as well as indirectly
through increased plant productivity which increases biomass. Increasing soil carbon is important for
climate adaptation (e.g., water holding capacity) and mitigation (prevention of carbon dioxide emissions).
Soil organic carbon is also an essential source of fuel for soil microbes to mineralize nutrients necessary
for crop growth. Applying carbon-rich amendments can fulfill two goals that are sometimes in tension with
each other: building soil carbon stocks for long-term health and sequestration, and increasing microbial
activity and carbon mineralization to enhance crop yield (Liptzin et al. 2022). It is important to note that
the potential to sequester additional carbon by applying soil amendments is limited by the current health
of the soil. Disturbed or degraded soils offer more sequestration potential than healthy soils. For example,
greater soil carbon sequestration may be possible on croplands and abandoned mine sites than on
unfilled rangelands (Gravuer et al. 2019). Similarly, greater soil carbon sequestration is possible on
disturbed urban lands like new housing developments and highway right-of-ways than on well-tended
yards and landscapes (Brown and Beecher 2019).
While there are differences among the particular wasted food-derived amendments discussed here, all of
these amendments demonstrate clear benefits compared to synthetic fertilizers (Brown et al. 2011; Moller
2015; Urra et al. 2019; Ippolito et al. 2021). These amendments also avoid the energy-intensive process
and greenhouse gas emissions of producing mineral and synthetic fertilizers (Kraj and Smol 2023).
Compost
The regenerative benefits of compost are well recognized in the literature. Given the amount of research
on its regenerative benefits, compost provides a point of comparison for other amendments throughout
this analysis.
Amending soil with compost increases soil organic matter, soil microbial biomass, fertility, porosity,
aeration, water holding capacity, and earthworm populations, and decreases soil bulk density and risk of
erosion. Mature compost is stable (i.e., not undergoing rapid degradation) and significantly contributes to
carbon sequestration and long-term carbon storage. For example, a recent study demonstrated that
compost amendments to rangelands improved aboveground production by more than 40 percent and
belowground carbon content by 50 percent (Kutos et al. 2023).Compost increases organic carbon in soils
by directly adding organic matter and also by promoting plant productivity, which adds more organic
matter to soils. Compost's positive impact on soil carbon has been proven through studies in a range of
agricultural systems and ecosystems and over different time periods (Ippolito et al. 2010; Brown et al.
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2011; Ryals et al. 2014; Kutos et al. 2023). A study on one-time compost application to valley and coastal
grasslands showed soil organic carbon had increased at the end of the first growing season and after
three years (Ryals et al. 2014). Another study showed an increase in soil organic carbon persisted 14
years after a one-time application of biosolids compost to a semi-arid grassland, with higher rates of
compost application resulting in higher levels of carbon (Ippolito et al. 2010). In urban soils, compost
application has also resulted in carbon storage (Brown et al. 2011). The organic matter in compost is
stable and less prone to volatilization or mineralization than uncomposted organic matter, which makes
compost highly effective at increasing soil organic carbon (Gilbert et al. 2020).
Compost also provides slow release of nutrients to promote long-term soil health and renewal
(Thyagarajan et al. 2014; WRAP 2016; Urra et al. 2019; Grigatti et al. 2020; Lu and Xu 2021; Le Pera et
al. 2022a; Stehouwer et al. 2022). Compost's water holding ability can increase an ecosystem's climate
resilience, storing water to protect against drought and absorbing water to mitigate flood damage.
On a mass basis, nitrogen is the most prevalent of the macro and micro-nutrients provided by wasted
food-derived soil amendments. Compost contains nitrogen primarily in its organic form, which must be
mineralized into inorganic nitrogen (i.e., nitrate NO3- or ammonium NH4+) before most plants can use it.
Roughly 10% of nitrogen will be available to plants upon application of compost, with up to an additional
10% typically mineralizing in the first year (Ozores-Hampton et al. 2022; Stehouwer et al. 2022).
Mature compost is biologically stable, making it suitable for use on lands with high human contact, such
as gardens and public green spaces. The relative stability of other amendments depends on post-
treatment methods (which may include composting). In addition, compost can be applied at a high rate
because of its high C:N ratio - more carbon can therefore be added to the soil before the crop's nitrogen
needs are met.
Compost made from food waste (in part) demonstrates mean 15.1 C:N ratio (Stehouwer et al. 2022).
Digestate: Anaerobic Digestion (on-farm and stand-alone)
On-farm and stand-alone digesters produce digestate which is commonly applied to land (AD at WRRFs
produce biosolids, discussed in subsequent section). Studies specifically comparing digestate and
compost illustrate the differences in the composition and regenerative effects of the two types of soil
amendments (WRAP 2016; Nicholson et al. 2017; Case and Jensen 2019; Yan et al. 2023). Since
feedstock can affect the composition and effects of amendments, all studies referenced in this section
specifically examined digestate and compost made in part from wasted food, unless otherwise noted.
Available research suggests that digestate may be less effective than compost in several key areas of
regeneration, such as nutrient retention (i.e., keeping nutrients for use by plants and soil microbes),
carbon sequestration, and long-term soil health.
Digestate contains primarily inorganic nitrogen (compost is primarily organic N), which is readily available
and can be used by plants immediately (Stehouwer et al. 2022). Notably, digestate made in part from
wasted food typically has higher ammonium (i.e., inorganic nitrogen) content than digestate made from
other common feedstocks like crop residues and animal manure (Dutta et al. 2021; O'Connor et al.
2022a).
Two field studies illustrate the key differences in composition of compost and digestate made from wasted
food, demonstrating that compost had higher total nitrogen levels, but lower readily available nitrogen
levels, than digestate (WRAP 2016). See Table 4-4 for details.
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TABLE 4-4. MEAN NITROGEN COMPOSITION OF WASTED FOOD-DERIVED SOIL AMENDMENTS
Data Source
WRAP 2016
Nicholson et al. 2017
Digestate
Compost
Digestate
Compost
Feedstock
Wasted food
and manure
Wasted food
and green
waste
Wasted
food
Wasted food
and green
waste
Total Nitrogen
(kg/ton wasted food)
4.67
11.8
7.4
10
Readily available Nitrogen*
(kg/ton wasted food)
3.78
0.81
6.3
0.85
Readily available Nitrogen* (% of total N)
81%
7%
86%
8.0%
*Readily Available Nitrogen data from WRAP includes NhU and NO3. RAN data from Nicholson et al. includes only
NH4; however, Nicholson measured NO3 and found it to be minimal (<0.1) in all cases.
Note: Both studies were led by the same researcher.
A study by Tambone (2010) reinforced these general findings about the composition of compost and
digestate, finding samples of digestate made primarily from wasted food (80% organic fraction of MSW
and 20% pig slurry) contained 26% to 48% inorganic nitrogen (as a fraction of total nitrogen), while
samples of compost made from the organic fraction of MSW and green waste contained only 10%
inorganic nitrogen.
These differences in nitrogen content give distinct strengths and weaknesses to each amendment. While
both compost and digestate can increase soil nutrients, crop yields, and crop quality over a short time
period (WRAP 2016), digestate's greater readily available nitrogen content makes it well-suited to be a
substitute for synthetic fertilizers (Tambone et al. 2010; Morris et al. 2014). In addition, the nitrogen-
phosphorus-potassium (NPK) ratio of digestate made from wasted food can be similar to synthetic
fertilizers (Dutta et al. 2021). In contrast, compost provides long-term reserves of organic nitrogen,
improving nutrient retention and soil health over multiple growing seasons (Stehouwer et al. 2022), but, at
typical application rates, does not fulfill crops' complete short-term nitrogen needs and is often used in
conjunction with fertilizers (Le Pera et al. 2022b).
Yet, digestate's high proportion of inorganic nitrogen also increases the potential for nitrogen losses to the
environment (Cooke et al. 2001; Le Pera et al. 2022a; Yan et al. 2023). Nitrogen losses can take three
forms - ammonia emissions, nitrous oxide emissions (a GHG with 298x more global warming potential
than carbon dioxide over 100-yr period), and nitrate leaching and runoff - all of which are harmful to the
environment. These nitrogen losses contribute to acid deposition, formation of particulate matter, climate
change, and eutrophication of surface and ground water. Losses can occur during storage and transport
or after application of digestate (Le Pera et al. 2022a).
Evidence indicates nitrogen losses are greater from digestate than from compost. Researchers suggest
60% to 70% total nitrogen may be lost in direct land application of digestate made from wasted food given
its higher ammonium content (Dutta et al. 2021). Also, nitrogen loss from digestate is more dependent
upon intrinsic characteristics of the digestate such as inorganic N content than on any external conditions
like soil type (Rigby and Smith 2013).
Two studies measured nitrogen losses to the environment from digestate and compost application. A field
study comparing nitrogen losses from digestate and compost under similar conditions at multiple sites
demonstrated lower nitrogen losses as ammonia emissions from compost (3.3% mean emissions factor,
as % total nitrogen applied) than digestate (38% or 42% mean emissions factor, depending on application
method). Cumulative nitrate leaching was also significantly lower for compost than digestate in the study
(Nicholson et al. 2017). A laboratory study examined leachate from application of digestate and compost
finding that compost leached less nitrogen than digestate over 50 days (Yan et al. 2023). Researchers
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note that leaching and volatilization of nitrogen during or after application "remains a challenge
for...widespread use" of digestate (Yan et al. 2023).
The same two studies were inconclusive on the differences in nitrous oxide emissions from compost and
digestate, indicating nitrous oxide emissions are low (less than 1%) for both amendments and, in the case
of compost, not significantly different than background values (Nicholson et al. 2017). Since nitrous oxide
forms from ammonium or nitrate, greater amounts of inorganic nitrogen can mean greater potential for
emissions. In general, nitrous oxide emissions are heavily dependent on climatic conditions, such as
temperature, and application rate and timing within the growing season, and emissions can be predicted
and controlled based on those factors (Crolla et al. 2013; Lazcano et al. 2016). For example, applying
digestate in the fall when soils are cooler and wetter will limit nitrous oxide emissions compared to
applying in spring when soils are warmer and better aerated (Crolla et al. 2013).
Digestate typically has lower carbon content (as percentage of dry matter) and a lower C:N ratio than
compost, likely limiting its potential (relative to compost) to sequester carbon and improve soil structure
and health (O'Connor et al. 2021). Differences in amounts of carbon sequestered through application of
compost or digestate may be small and, unless applied to similar sites, would also be dependent on other
factors including soil type, climatic conditions, and level of soil degradation. More research is needed in
this area.
Anaerobic digestion utilizes 20% to 95% of carbon in feedstocks to make energy (Moller 2015), thus
diminishing its carbon stock; more research is needed to determine losses under different operating
parameters. The composting process also results in carbon losses, primarily as biogenic carbon dioxide.
One lab study of municipal wasted food sent to a "wet" mesophilic anaerobic digester shows how the
carbon in resulting digestate is less than in the wasted food feedstock due to conversion to biogas (Table
4-5).
TABLE 4-5. CARBON CONTENT OF WASTED FOOD AND WASTED FOOD-DERIVED DIGESTATE
Municipal wasted food
Wasted food digestate
Carbon (as % dry matter)
46.18 ±0.1
26.98 ± 0.4
Nitrogen (as % dry matter)
3.02 ±0.11
3.26 ±0.13
C:N ratio
15.29
8.28
Data source: Paul et al. (2018)
Research suggests that compost can increase soil organic matter more quickly than digestate through its
higher carbon content (WRAP 2016). There is evidence that digestate can decrease bulk density and
increase water retention capacity and aggregate stability of soil (compared to untreated soil); however,
these effects have only been demonstrated over short time frames (Moller 2015; O'Connor et al. 2021).
Overall, evidence suggests digestate has greater potential as a fertilizer substitute but lesser potential to
provide long-term benefits to soil health relative to compost (O'Connor et al. 2021).
Application rates may also inform the soil health benefits of amendments. Often digestate is applied at a
rate determined by nitrogen needs of a crop (Morris et al. 2014), which may not provide as much carbon
as a compost application per unit of land, since nitrogen in digestate is more readily available and
therefore its application rate is more restricted.
Biosolids: Anaerobic Digestion (at WRRFs) and Sewer/WWT
Biosolids are created from wastewater solids at WRRFs. For the sewer/WWT pathway, wasted food is
disposed of down a sink drain, co-mingling with sewage and other wastewater, and travelling through the
sewer and WRRF operations (i.e., wastewater treatment stages). For the AD at WRRFs pathway, wasted
food is brought directly to the anaerobic digester at a WRRF (typically by truck) to be digested along with
wastewater solids. In this case, the wasted food that is co-digested with the wastewater solids does not
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go through the wastewater treatment stages. In both pathways, wasted food is never the dominant
feedstock. It is always a small fraction of the total feedstock, and thus does not drive the characteristics or
effects of the biosolids. Wasted food can represent a greater proportion of feedstock in AD at WRRFs
than in sewer/WWT.
Biosolids contain primarily organic nitrogen with mineralization rates (conversion from organic nitrogen to
a more bioavailable form) dependent on treatment process, type of soil, crop grown, and climatic
conditions. Application rates can also impact crop response compared to synthetic N. Slower
mineralization rates extend crop response to biosolids N across multiple growing seasons (Brown et al.
2020). Biosolids from both pathways have been proven to increase soil organic matter, aeration, water
infiltration and holding capacity, microbial activity, and reduce erosion, compared to a control (i.e., no
treatment), but also to cause nitrogen and phosphorus runoff and leaching and nitrous oxide emissions
(Thangarajan et al. 2013; Morris et al. 2014; Oladeji et al. 2020; Ippolito et al. 2021).
In general, the nitrogen composition of biosolids (and nitrogen losses from application of biosolids) falls
between that of digestate and compost. A laboratory study comparing biosolids, compost, and digestate
from varying feedstocks found biosolids (treated through AD, composting, drying/pelletization, and
dewatering) generally had lower percentage of nitrogen in inorganic form and lower nitrogen releases
than digestate (Case and Jensen 2019). Another study confirmed biosolids have less nitrogen in the form
of ammonium than digestate made from wasted food (Dutta et al. 2021).
The regenerative potential of biosolids may vary considerably based upon treatment method (including
post-treatment). Treatment method has been demonstrated to significantly affect the nitrogen availability
in biosolids, with aerobically digested biosolids > thermally dried biosolids > lime-treated biosolids >
mesophilic anaerobically digested biosolids > composted biosolids for readily-available nitrogen as a
percentage of total nitrogen (Oladeji et al. 2020). Greater nitrogen availability can lead to greater runoff,
leaching, and air emissions, at certain application rates. As with digestate, the rate of biosolids application
is usually determined by a crop's nitrogen needs.
The carbon content of biosolids may also be affected by treatment type. Carbon is lost during AD
(converted to biogas) and aerobic processes at WRRFs, reducing the total solids and the total carbon in
the final biosolids (Moller 2015; Morris et al. 2014).
Composting Digestate and Biosolids
The regenerative benefits of composting can also be realized by composting digestate and biosolids from
the AD and sewer/WWT pathways. There is broad agreement in the literature that composting these
outputs can stabilize organic matter, decrease volume (making storage and application less expensive),
increase soil health benefits of application, and conserve nitrogen and phosphorus, thus reducing nutrient
pollution to air and water (Urra et al. 2019; Grigatti et al. 2020; Lu and Xu 2021; Le Pera et al. 2022a).
Due to the stabilization and dilution of nitrogen in the composting process, composts can be applied at a
higher rate than other amendments without exceeding a crop's nitrogen requirements or increasing the
risk of nitrogen pollution.
An LCA comparing composting of wasted food to AD of wasted food followed by composting of the
wasted food-derived digestate at a plant in Italy showed benefits across most categories, including GHG
emissions, for AD followed by composting. The study also confirmed similarity (including nutrient content)
of the two compost products (Le Pera et al. 2022a).
A two-year greenhouse study comparing the composition and effect of biosolids and composted biosolids
(both from sewer/WWT pathway) applied to clay and sandy loam soils showed composting decreased
cumulative nitrate leaching without significant effect on plant growth. The composted biosolids had lower
ammonium content (as percentage of total nitrogen content) and higher carbon-to-nitrogen ratio
(increasing from 7.5 to 8.9) than uncomposted biosolids. Both amendments were applied at nitrogen-
based application rates to ensure adequate nitrogen. Importantly, the researchers suggest that, even in
high-rate applications, composted biosolids should not cause "leaching concern" (Oladeji et al. 2020).
While an exhaustive study and comparison of biosolids treatment methods is beyond the scope of this
analysis, many examples exist in the literature of composting providing benefits relative to other treatment
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methods, with regard to energy use (e.g., from thermal drying and ammonia stripping (Case and Jensen
2019; Lu and Xu 2021)) and nitrogen losses (Askri et al. 2016; Case and Jensen 2019).
In EPA's survey of AD facilities processing wasted food, 55% stand-alone digesters, 25% on-farm
digesters, and 14% co-digestion systems at WRRFs reported composting as one of the practices used for
managing solid digestate or biosolids when asked how they manage their solid digestate (20 stand-alone
facilities, 12 farms, and 58 WRRFs responded; multiple answers allowed) (U.S. EPA 2023).
Unharvested/Plowed-ln Crops
There is limited research on the regenerative potential of the unharvested/plowed in pathway. However,
two other avenues of research can provide valuable insights. First, since parts of unharvested/plowed-in
crops are food (i.e., the parts typically sold to consumers), research comparing wasted food feedstocks
for composting and AD with finished compost and digestate made from wasted food is relevant.
Researchers have found that composted feedstocks have longer-term positive effects on soil than
uncomposted feedstocks (Urra et al. 2019). Uncomposted food is less stable than compost, decomposing
more quickly and leaving only one-third of organic matter on soil after one year (Ozores-Hampton et al.
2022). Digestate made from wasted food has also been found to be more stable than raw wasted food
(Moller2015); however, raw wasted food would add more carbon to the soil than digestate, since
digestion transforms some of the carbon into energy (Moller2015). Raw wasted food and digestate made
from wasted food contain similar amounts of nitrogen but different carbon-to-nitrogen ratios.
Second, similar to the unharvested/plowed in pathway, the agricultural practice of maintaining crop
residues (i.e., the part of a plant that is not harvested) and planting cover crops64 leave plant material in
the field unharvested to be tilled or grazed to improve soil health and reduce inputs. Cover crops and crop
residues improve the physical, biological, and chemical properties of soil by providing carbon and
nutrients to the soil (Blanco-Canqui and Lai 2009; Turmel et al. 2015; Adetunji et al. 2020). These
benefits lead to carbon sequestration, moisture retention, reduction in erosion, weed control, and greater
soil fertility. However, compared to wheat and legume crop residues, biosolids have been shown to more
effectively build soil organic carbon (Wuest and Gollany 2013). It should be noted, because cover crops
are grown to improve soil health and not for human consumption, they are predominantly legumes and
grasses. These will provide different and potentially greater benefits to soil than food crops which are
unharvested/plowed in.
Depending on the unharvested crop type, its effects on soil health may be more similar to raw wasted
food or to cover crops. In general, unharvested crops should be expected to provide feed for livestock
and carbon and nutrients to soil (though in less stable form than compost, biosolids or digestate), thus
providing, at a minimum, short-term benefits to soil health and plant productivity.
Raw Wasted Food: Land Application
The land application pathway is also not well-studied. The types of wasted food from food processing
facilities that may be applied to land vary widely, and studies typically focus on one specific waste stream.
Regeneration benefits appearto be mixed, depending on the type of waste applied and other ecosystem
and agronomic characteristics. There is potential for increased soil carbon, microbial activity, and
aggregate stability (Plante and Voroney 1998; Rashid and Voroney 2004) as well as nitrogen pollution
(Batuecas et al. 2019), and wasted food application may or may not meet needs for crop growth without
additional fertilizer or organic amendments (Rashid and Voroney 2004; San Miguel et al. 2012).
Other Pathways
The animal feed pathway contributes to manure production, and so indirectly provides nutrients and other
benefits to soil. As noted, manure may be co-digested with wasted food in the on-farm AD and stand-
alone AD pathways, but the majority of manure is managed separately from wasted food. The relative soil
health benefits of manure compared to compost, digestate, and biosolids made in part from wasted food
are beyond the scope of this report.
The remaining two wasted food management pathways -controlled combustion and landfill -are not
regenerative and thus are not discussed in this section. While landfills do sequester carbon, they also
emit significant amounts of methane and do not return nutrients or organic carbon to soils.
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Regeneration Summary
In summary, the weight of evidence for compost's regenerative abilities is strong. Composting wasted
food and composting digestate or biosolids made in part from wasted food provide numerous, well-
documented regenerative benefits to soil. The regenerative abilities of biosolids and digestate may be
more limited and are heavily dependent on post-treatment for stabilization and nutrient retention.
Research suggests that digestate is best used as a short-term nutrient boost akin to a fertilizer, whereas
compost is expected to provide longer-term benefits. It is possible that digestate will, over a longer time
period, provide broader soil health benefits, but this has not been proven. Biosolids likely fall between the
compost and digestate on the spectrum of regeneration. While there is more research and evidence of
the regenerative benefits of biosolids than that of digestate, it is also clear that composted biosolids
provide greater regenerative benefits than uncomposted biosolids, keeping compost as the "gold
standard" for regenerative soil amendments.
In addition, compost, digestate, biosolids, land-applied wasted food, and unharvested/plowed-in crops all
add organic matter to soils, which promotes nutrient cycling and enhances soil structure. The physical
structure of soils - porosity, aggregate stability, bulk density, etc. - is important for water retention and
percolation and for carbon sequestration. Compost contains more organic matter in a less volatile form
(partly due to its higher dry matter content), making it better suited to build soil organic matter more
quickly.
Because synthetic fertilizers contain nutrients in inorganic forms that are readily available to plants, they
provide short-term benefits for crop growth. In comparison, organic nitrogen and phosphorus require
mineralization by microbes in order to be available for plant uptake, therefore remaining in the soil for a
longer period of time. Synthetic nitrogen and phosphorus fertilizers are more prone to runoff which can
impact water quality. The effect of synthetic nitrogen fertilizer on soil organic matter (SOM) varies greatly
in the literature, with some studies showing nitrogen fertilizer increasing SOM through increased plant
productivity and other studies showing nitrogen fertilizer decreasing SOM by enhancing mineralization
(Mahal et al. 2019).
While composting improves the regenerative potential of digestate and biosolids, all three amendments
are more regenerative than synthetic fertilizer. For example, a 22-year comparison of uncomposted
biosolids versus synthetic fertilizers in semi-arid dryland wheat fallow rotations showed biosolids improved
soil health, through indicators such as soil carbon and microbial biomass, while fertilizer had little effect
(Ippolito et al. 2021). These amendments also retain more nutrients, allowing less nitrogen to volatilize,
leach or runoff into the environment (Sogn et al. 2018; Oladeji et al. 2020). In addition, unlike the most
commonly used synthetic fertilizers, soil amendments made from wasted food and/or other plant material,
manure, or biosolids can provide additional nutrients beyond nitrogen, phosphorus and potassium, which
plants need to thrive (Morris et al. 2014).
Figure 4-5 provides a ranking of wasted food pathways based on their alignment with the regeneration
theme of circularity (or by the extent to which they are regenerative).
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c
o
-4->
to
a)
0
o
Anaerobic Digestion, with composting of digestate/biosolids
Composting
Sewer/WWT, with composting of biosolids
0
Anaerobic Digestion, with land application of digestate/biosolids
Sewer/WWT, with land application of biosolids
Unharvested/Plowed In
Anaerobic Digestion, with incineration or landfill of digestate/biosolids
Animal Feed
Incineration
Land Application
Landfill
Sewer/WWT, with incineration or landfill of biosolids
most circular
e—^
least circular
FIGURE 4-5. REGENERATION: ALIGNMENT OF WASTED FOOD PATHWAYS
Within each tier the pathways are presented in alphabetical order.
.Regeneration is defined here as an "approach that has the capacity for self-renewal and resiliency, contributes to soil health,
increases water percolation and retention, enhances and conserves biodiversity, and sequesters carbon" (Elevitch et al. 2018).
Since source reduction, donation and upcycling minimize the need for waste management strategies, they are not ranked with
regard to the other circularity themes (value, purity and regeneration).
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4.7 Alternative Methods for Circularity Assessments
While no studies that quantitatively evaluated the wasted food pathways for circularity were available in
the literature, two studies qualitatively examined and ranked wasted food pathways in a circular economy
framework. Wang et al. (2021) declared six pathways either "linear" or "circular" based upon a definition of
circular economy from Jurgilevitch (2016) which focused on reducing wasted food, utilizing byproducts,
and nutrient recycling (Jurgilevich et al. 2016; Wang et al. 2021). Landfill and controlled combustion were
categorized as linear, given their waste of nutrients; and source reduction, donation, AD, animal feed, and
composting were categorized as circular. No rankings were provided within the two categories.
Tanveer et al. (2021) mapped eight of the wasted food pathways discussed in this report to the R
framework that serves as the basis for the United Nations Environmental Programme's Circularity
Framework (Potting et al. 2017; UNEP 2019). The R framework is an expansion of the traditional reduce-
reuse-recycle framework that incorporates circular economy strategies. In order of priority, the framework
suggests the following circular strategies: refuse, rethink, reduce, reuse, repair, refurbish, remanufacture,
repurpose, recycle, and recover. See Table 4-6 for findings.
Several pathways aligned with more than one R, making clear ranking difficult. In general, the authors
found the source reduction and donation pathways to be the most circular, followed by animal feed and
upcycling, then AD and composting, then controlled combustion, then landfill as least circular. Tanveer et
al. (2021) did not consider the land application, sewer/WWT or unharvested/plowed in pathways. For this
ranking, the analysis assumes beneficial use of nutrients from AD; without this, AD is ranked as energy
recovery (R9), a lower ranking.
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TABLE 4-6. MAPPING OF WASTED FOOD PATHWAYS
TO THE CIRCULAR STRATEGIES OF THE "R" FRAMEWORK
Circular "R" strategies, in order of priority, from left to right
R0: Refuse
R1: Rethink
R2: Reduce
R3: Reuse
R4: Repair
R5: Refurbish
R6: Remanufacture
R7: Repurpose
R8: Recycle
R9: Recover
Dispose
Source
Reduction
Donation
Animal
Feed
S
Upcycling
Anaerobic
Digestion*
Composting
Controlled
Combustion/
Incineration
Landfill
Data source: Tanveeretal. (2021)
*lf digestate is applied to land as fertilizer, AD is matched with R8: Recycle. If the purpose of AD is only energy
recovery, AD is matched with R9: Recover.
R strategies are listed in order of priority from R0 to R9, followed by disposal. Pathway names were converted to
those used in this report where definitions were similar. For example, "converted into human food" is noted as
upcycling here. The land application, sewer/WWT, and unharvested pathways were not considered in this analysis.
More specific case studies exist in the literature as well. For example, a qualitative assessment
comparing use of cereal bran waste for upcycling, biogas production, and animal feed production found
that upcycling outperformed the other waste management pathways in terms of system circularity (Grippo
et al. 2019). However, these specific findings cannot be translated into more general findings applicable
to this analysis.
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4.8 Limitations of Circularity Assessment
The circularity assessment both benefits from and is limited by its qualitative nature. A qualitative analysis
allows for investigation in areas without standardized data like soil health but limits the quantitative rigor
of the analysis. Data gaps in some areas important to circularity exist. While extensive information about
many of the pathways is available in the scientific literature, some of the environmental areas of greatest
importance to circularity—like soil health and nutrient retention/losses—have not received as much
attention as global warming potential or energy production of the pathways. In addition, the science of
carbon sequestration in soil is an active and quickly evolving field. Additional work on both the climate
mitigation (via carbon sequestration) and climate adaptation (via improved soil health) potential of wasted
food pathways will strengthen circularity analyses in the future.
Another evolving area of research is on "nutrient circularity" (Harder et al. 2021). Studies assess flows of
nutrients (e.g. nitrogen and phosphorus) in a given region's food system, considering the imports,
exports, and local production and consumption of food and feed crops, live animals, and "organic
residuals" (wasted food, crop residuals, manures, human excreta/biosolids) (Harder et al. 2021; Moinard
et al. 2021; van der Wiel et al. 2021). Some of the materials considered in nutrient circularity analyses are
outside the scope of this report (e.g., manures). However, continued tracking and quantification of
nutrients throughout a system and region can add additional nuance to future circularity analyses of
wasted food management pathways.
Much recent work has been done on contamination of feedstocks, including wasted food, to the
pathways, but still little is known about the risk posed to human health and the environment from
application of contaminated soil amendments. This analysis relies on data on the relative levels of key
contaminants in various feedstocks to assess purity but could not consider the risks posed by those
contaminant levels due to lack of data.
Chapter 4. Circularity Assessment
4-24
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4.9 Circularity Assessment Conclusions
This chapter analyzed each wasted food pathway's potential contribution toward a more circular food
system, along four themes:
Waste Prevention: The most circular strategy is to design waste out of processes, minimizing the
need to manage waste.
Value: The intended purpose and highest value of food is as human sustenance, including its use
to feed livestock. Once food can no longer nourish humans, the next highest value is the recovery
and beneficial use of the nutrients most important to agriculture - nitrogen, phosphorus and
potassium - and carbon to build soil organic matter. Energy and other materials may also be
recovered from wasted food.
Purity: Keeping wasted food free of physical and chemical contaminants allows for greatest
beneficial use of recovered materials. Purity is best maintained by collecting and processing
wasted food streams separately from other wastes, since many waste steams (e.g., manure and
wastewater solids) are more contaminated than wasted food. Also, some pathways can mitigate
contamination by destroying or inactivating some contaminants. Food must also be removed from
all non-compostable packaging, which can introduce physical and chemical contaminants to the
waste stream.
Regeneration: The carbon- and slow-release nutrient-rich outputs of some pathways can help to
regenerate ecosystems when applied to land. Improved soil health can help mitigate climate
change (e.g., through carbon sequestration) and improve climate resilience of ecosystems (e.g.,
through soil moisture conservation).
The overlaps and interactions between these four themes can generate additional complexities in
comparing wasted food pathways. For example, adding organic carbon to soil fuels two processes that
compete for that carbon: building long-term soil carbon stocks and driving nutrient mineralization to
increase crop yield (Liptzin et al. 2022). This points to a tension between the value of these organic
amendments (in terms of readily available nutrients and plant productivity) and their regenerative effects
(in terms of carbon sequestration and nutrient retention).
Figure 4-6 provides a summary of findings from the qualitative assessment. The rankings for the AD and
sewer/WWT pathways are dependent upon the use of the digestate/biosolids, and so three scenarios for
each pathway (where nutrient outputs are composted, land applied, or disposed of) are displayed.
Chapter 4. Circularity Assessment
4-25
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most circular e—o—^ least circular
FIGURE 4-6. SUMMARY OF CIRCULARITY THEME RANKINGS, BY PATHWAY
'Stand-alone digesters that only accept wasted food are ranked higher for purity.
Chapter 4. Circularity Assessment
4-26
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Based upon the findings of the qualitative assessment, a ranking of wasted food pathways is presented
here, with focus on environmental aspects of circularity. The hierarchy relies on analysis of specific
properties of food and how they affect a pathway's potential for circularity.
Figure 4-7 provide rankings of 11 wasted food pathways, by agreement with circularity themes, from most
circular to least circular.
Feed People
Source Reduction
Donation
Upcycling
Animal Feed
Recover Energy
AD, with incineration or landfill
Sewer/WWT, with incineration or landfill
Incineration
Landfill
FIGURE 4-7. RANKING OF WASTED FOOD PATHWAYS BASED ON CIRCULARITY
Figure depicts ranking of wasted food pathways, by contribution toward a more circular economy.
Analysis considered four circularity themes: (1) preventing waste, (2) maintaining highest value, (3) maintaining purity, and (4)
helping to regenerate ecosystems. Limited data were available on land application and unharvested/plowed in pathways.
Chapter 4. Circularity Assessment
4-27
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Key findings of the circularity assessment include:
Source Reduction, Donation, and Upcycling top the hierarchy since they minimize the need for
waste management.
Animal Feed shares the top tier since it maintains the original intended purpose and highest
value for food-to nourish humans, albeit indirectly by providing feed to livestock. All four of these
pathways share the potential to reduce the amount of food and feed production required to feed
people, thus reducing the substantial environmental externalities associated with agriculture.
Composting is the most circular wasted food management option available for wasted food
generated anywhere along the supply chain from production to consumers. This includes
composting of digestate and biosolids (see next bullet). Composting stabilizes wasted food,
providing many regenerative benefits to ecosystems, such as the slow release of nutrients,
carbon sequestration, and improved soil health and structure through addition of organic matter.
The composting process can also degrade or immobilize many contaminants.
Unharvested/Plowed In ranks as equally circular to composting, though is only available to
farmers. If the crops were to be ultimately wasted, then leaving crops in the field for grazing or
tilling into the soil returns the nutrients and carbon to the soil and prevents the unnecessary
downstream impacts of food processing, packaging, and distribution.
The circularity of the Anaerobic Digestion and Sewer/WWT pathways is dependent upon the
destination for the nutrient-rich outputs (digestate and biosolids) produced by these pathways.
o If digestate or biosolids are composted, the pathways rank higher, equal to composting.
Compost made from digestate or biosolids shares the beneficial qualities of compost made
from wasted food, though more contamination may be introduced in the process.
o If digestate or biosolids are applied to land (without first being composted), the pathways
rank just below composting but above landfill and controlled combustion. Digestate provides
many benefits to soil; however, its ability to improve soil health over the long-term to the
degree that compost can has not been clearly demonstrated. It can, however, reduce
significant environmental externalities by replacing synthetic fertilizer.
o If digestate or biosolids are disposed of at a landfill or incinerator, the pathway ranks lower,
alongside landfill and controlled combustion. Since AD recovers energy, the AD pathway is
more circular than sewer/WWT without AD.
Land Application of raw wasted food from the food processing sector ranks alongside AD and
sewer/WWT with land application of digestate or biosolids. Land application uses specific streams
of food processing waste which may vary widely in composition and regenerative potential; yet
the streams are typically free of contaminants since they are collected and managed alone.
Additional research is needed on this pathway.
Controlled Combustion and Landfill are the least circular wasted food pathways. Both
pathways scored consistently in the bottom tier across all four circularity themes. Both can
recover energy from wasted food, though less efficiently than AD, and neither result in beneficial
use of nutrition nor nutrients from wasted food. Only sewer/WWT can rank beneath these
pathways, and only if there is no energy recovery (via anaerobic digestion) and no beneficial use
of nutrients (including no effluent used as irrigation).
The results of this analysis align generally with the mapping to the R strategies performed by Tanveer et
al. (2021) and presented in the previous section; however, this analysis adds the concept of regeneration
which is important to biological systems. This analysis also provides a detailed comparison of the
recovered materials, noting differences in the evidence of regenerative abilities of compost and digestate.
Chapter 4. Circularity Assessment
4-28
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CHAPTER 5
DISCUSSION AND CONCLUSIONS
In its National Recycling Strategy, EPA emphasized the need to reduce the life cycle impacts of materials
(including food) and decouple natural resource use from economic growth by implementing circular
economy strategies. In this report, two complementary analyses are presented to evaluate 11 common
wasted food pathways with respect to these goals. Both the review of life cycle assessments from the
literature (Chapter 3) and the circularity assessment (Chapter 4) were utilized to develop the new EPA
ranking of wasted food pathways (called the Wasted Food Scale) presented later in this chapter.
Section 5.1 presents a comparison of the LCA and circularity assessment methodologies and results, and
Section 5.2 highlights the effect of wasted food as a feedstock in the pathways. Section 5.3 synthesizes
the report's findings into a new wasted food pathways hierarchy based upon environmental impacts and
contributions towards a circular economy.
5.1 Comparing Methodologies and Results
This section compares the LCA and circularity assessment methodologies and results, demonstrating the
value of combining these complementary approaches.
Life Cycle Assessment
LCA is a well-established methodology that relies upon quantitative data to analyze the cradle-to-grave
environmental performance of a process or product. For this report, results from 47 LCAs of the wasted
food pathways were reviewed and 11 environmental indicators were considered. At least one LCA was
available for each pathway, although for several pathways only one environmental indicator (global
warming potential) was assessed.
LCA works particularly well for impacts like GHG emissions, where data are readily available, and results
are easily comparable through GWP calculations. A ranking of the pathways based solely on net GHG
emissions is presented in Section 3.9. Confidence can be higher for GWP results than for many other
indicators, as more practitioners have examined this impact category.
LCA's strengths include identifying trade-offs between environmental considerations for decision-makers
and including the environmental benefits of avoided products (i.e., substituting alternative products made
through the pathways for conventional products with the same function) (Lindgreen et al. 2021). In the
LCAs reviewed here, wasted food pathways received credits for avoiding the production of food, animal
feed, energy, and fertilizer through substitution with products made through the pathways, where
appropriate. Credits for energy generation by a pathway often included a broad range of environmental
benefits, such as reduced GHG emissions, acidification, eutrophication, particulate matter, and toxicity
from avoided fossil fuel combustion. Credits for fertilizer production can include reduced energy demand
from avoided synthetic nitrogen fertilizer manufacturing and reduced acidification and eutrophication from
avoided synthetic nitrogen fertilizer application.
LCA is less valuable in areas where quantitative data does not exist in a standardized format that is easily
comparable across pathways. Of the 11 environmental indicators highlighted in this report, only four
allowed for meaningful quantitative comparisons across LCA studies - global warming potential, energy
demand, acidification, and eutrophication. Data for water consumption and land occupation were
available for quantitative comparison across LCA studies but found to be inconsistently modeled. Data for
additional categories (human toxicity, ecotoxicity, and particulate matter formation) were suitable for intra-
study comparisons.
Chapter 5. Discussion and Conclusions
5-1
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For one environmental indicator - soil health - specifically relevant to wasted food pathways,
standardized quantitative data were not available in the reviewed LCA studies. A key product of many
wasted food pathways is a soil amendment to provide organic matter and nutrients to improve soil health
and plant productivity (i.e., fertilize) and to provide ecosystem services. There is much published research
on the soil health benefits of these amendments, but quantification is not yet standardized, therefore
meaningful quantitative comparison across pathways was not possible in the life cycle assessment.
However, soil carbon sequestration, which is related to soil health, was considered as part of GWP
calculations where sufficient studies were available for applicable pathways (i.e., those that produce a soil
amendment).
Circularity Assessment
Circularity prioritizes preventing waste and utilizing outputs for their highest value rather than managing
them as wastes. Outputs should be free of contaminants and, in a biological system such as the food
system, help to regenerate ecosystems. Wasted food is a valuable output for which many opportunities
exist to reuse and recycle the contents. Circularity assessments allow for comparison of competing uses
(Sevigne-ltoiz et al. 2021), considering the unique value of food, to retain the highest value possible. For
example, circularity values recovery and beneficial use of soil nutrients and aiding ecosystem
regeneration over energy recovery from wasted food.
Circularity assessment is a newer field than LCA. Currently no appropriate quantitative metrics exist for
assessing the circularity of biological systems. Thus, a qualitative approach was used in this report. The
qualitative nature of the circularity assessment in this report allowed for the use of scientific information
from primary studies and reviews, without requiring standardization of data. In this way, soil health and
ecosystem services benefits from application of soil amendments created from wasted food could be
included in the assessment. Insights could also be synthesized from the primary scientific literature about
pathways not well-covered by the reviewed LCAs, such as unharvested/plowed in and land application
(only one and two LCAs available, respectively), and incorporated.
The circularity assessment can account for the relative performance of pathways, even when external
conditions affect that performance. For example, studies show soil type and climatic conditions greatly
affect leaching and runoff of nitrogen from soil amendments. However, pathways' relative performance
stays constant (e.g., how much leaching might change, but which pathway leaches the most does not). In
addition, each LCA typically reflected one set of operating parameters for a pathway, whereas the
qualitative circularity assessment could differentiate among choices of operating parameters within a
single pathway. For example, the majority of reviewed LCAs assumed beneficial use of nutrient-rich
digestate created by AD; however, disposal (e.g., landfill or controlled combustion) of these outputs is
also common in the AD pathway.
In contrast to LCA, circularity assessments do not intend to call out every negative externality, and thus
the literature suggests decision-makers use them in concert with LCA to ensure environmental
performance (Rigamonti and Mancini 2021). While circular strategies save virgin resources, they may not
perform better environmentally across all categories, due to energy or water requirements (Lindgreen et
al. 2021; Gallo et al. 2023). Thus, existing research supports the need to combine these approaches to
inform decisions even when circularity is the primary goal.
It should be noted that neither methodology used in this report considered social and economic factors,
which were beyond the scope of this report. Additional tools, such as life cycle sustainability assessment
or life cycle costing, could be used in the future to integrate these criteria.
Figure 5-1 displays a comparison of the LCA and circularity methodologies.
Chapter 5. Discussion and Conclusions
5-2
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Life Cycle Assessment (LCA)
V Well-established
s Quantitative
s Measures overall environmental
performance
s Identifies trade-offs (i.e., burden
shifting)
s Can include avoided impacts
* Cannot compare studies in areas
without standardized quantitative
data, like soil health
x Typically does not consider whether
resources are limited or there are
competing uses for a resource
Circularity Assessment
S Newer discipline
s Qualitative (for biological systems,
such as the food system)
s Measures continued use of resources
(i.e., resource cycling) to reduce virgin
resource consumption
v Considers highest value for material
use among competing uses, factoring
in resource scarcity
s Can include scientific findings in areas
without standardized quantitative
data, like soil health
x Does not guarantee higher
environmental performance
FIGURE 5-1. COMPARING LCA AND CIRCULARITY ASSESSMENT METHODOLOGIES
Combining LCA and Circularity Methodologies
LCA arid circularity assessment methodologies have been used synergistically in a variety of ways in the
literature - from simply considering the results of the two independent analyses together, to using a more
formal approach like multi-criteria decision analysis to integrate results, to formally integrating quantitative
circularity indicators into LCA (Rigamonti and Mancini 2021; Gallo et al. 2023). LCA can be performed
first to limit options under consideration in the circularity analysis by environmental performance; or LCA
can be used to assess and compare strategies identified as circular by the circularity assessment. LCA
can also be used to identify improvements needed in the environmental performance of desired circularity
strategies (Pena et al. 2021).
Regardless of how they are combined or integrated, using both methodologies can reveal trade-offs
between resource circularity and environmental impacts and among environmental impacts, helping
decision-makers avoid shifting problems from one environmental area to another (e.g., decreasing global
warming potential but increasing acidification). Using both quantitative and qualitative methodologies can
also provide benefits, allowing for consideration of important environmental criteria where quantitative
data are not standardized.
In this report, the LCA review and circularity assessment were independently performed, then the results
were considered together to inform the creation of a hierarchy of wasted food pathways. The LCA review
enabled comparison of the environmental footprint of circular and linear pathways, and the circularity
assessment provided insight into environmental areas not covered by the LCAs, including resource
conservation and soil health.
Comparing Results
A summary of the rankings informed by the LCA and circularity assessments and presented in Chapter 3
and Chapter 4, respectively, is provided in Figure 5-2.
Chapter 5. Discussion and Conclusions
5-3
-------
More
preferred
c/)
-4—'
o
CC
Q.
E
<
O
Feed People
Source Reduction
Donation, Upcycling
Unharvested/ Plowed In*
Anaerobic Digestion, Animal Feed,
Composting, Controlled Combustion,
Land Application *
Landfill, Sewer IWWT (with or without AD)
Less
preferred
Source Reduction
Donation
Upcycling
Animal Feed
Regenerate Soil
Composting
AD or Sewer/WWT, with composting
Unharvested/Plowed In
AD or Sewer/WWT, with land application
Land Application
Recover Energy
AD, with incineration or landfill
Sewer/WWT, with incineration or landfill
Incineration
Landfill
FIGURE 5-2. SUMMARY OF LCA (LEFT) AND CIRCULARITY (RIGHT) ASSESSMENT RANKINGS
OF WASTED FOOD PATHWAYS
Pathways listed in tiers from most preferable to least preferable, from top to bottom, in each diagram.
In LCA diagram, pathways within tiers are listed in alphabetical order.
In circularity diagram, pathways within tiers are listed in preferential order.
*denotes limited data
Chapter 5. Discussion and Conclusions 5-4
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In both methodologies, source reduction, donation, and upcycling achieve the highest rankings. These
pathways nourish humans, avoid (or minimize) the waste of food, and have the potential to displace some
of the additional food production required to feed a growing population (and consequently avoid the
substantial environmental impacts of food production).
At the other end of the spectrum, both methodologies ranked landfills as one of the least preferable
options (i.e., in the bottom tier) for wasted food management. Fugitive methane emissions from rapid
anaerobic decay of wasted food at landfills, along with other negative environmental effects such as
untreated leachate leading to water pollution, demonstrate that landfills are one of the worst
environmental performers among the pathways. In addition, landfilling is a textbook example of a linear
(i.e., not circular) pathway, as no materials are recovered and recycled. While some energy is recovered
from landfills, much of the produced methane from wasted food escapes as fugitive emissions before it
can be captured and converted to energy.
For the other seven pathways, results did not align exactly between the circularity analysis and LCA. Key
differences between the results of the two methodologies for other pathways arise from (1) how they
value energy use and avoided energy use; (2) how they consider emissions and releases during the
waste management process; and (3) how they include soil health and ecosystem benefits in the analysis.
Energy Use and Avoided Energy Use
The overall LCA results are driven largely by GHG and energy demand, due to the availability of
standardized data for most pathways and clear differences in GHG performance among many of the
pathways. Thus, a GHG-only hierarchy is presented in the report as well for transparency (see Figure
3-10). The GHG impacts in the LCAs typically integrated data on (1) emissions during the pathway; (2)
avoided emissions due to the use of products (food, feed, energy, and/or soil amendments) created by
the pathway; and (3) carbon sequestration potential (including through application of soil amendments, if
produced by the pathway).
Beyond source reduction, donation, and upcycling, the GHG rankings were most dependent on two
factors: the use and production of energy (i.e., energy demand) and fugitive methane emissions from
rapid anaerobic decay of wasted food. While all wasted food pathways use energy to varying degrees,
three pathways generate energy from wasted food - AD, controlled combustion and landfill. The
sewer/WWT pathway may also produce energy if AD is included. Per unit of wasted food, AD produces
more net energy (i.e., subtracting the energy used on-site to run the pathway) than controlled combustion,
which produces more net energy than landfill.
Only fugitive methane emissions from the anaerobic decay of wasted food outweigh the global warming
potential impacts of energy use and avoided energy use in the wasted food pathways. Sewer/WWT and
landfill ranked most damaging of all pathways for global warming potential due to fugitive methane
emissions from sewer transport to WRRFs and fugitive methane emissions released before a landfill gas
collection system is installed, respectively. Where anaerobic decay was not a factor and energy was
produced from wasted food, beneficial GWP performance is often observed (e.g., AD and controlled
combustion). Data on landfills was robust, whereas data on sewer/WWT is still limited.
In the LCA analysis, more than half of the other environmental criteria (including all four criteria where
meaningful quantitative comparisons were possible) were impacted by the use of energy and the
production of net energy and its assumed displacement of traditional fossil fuel energy sources. In some
cases, energy use was the primary driver of emissions in wasted food pathways. Energy demand is a
direct measure of energy use and/or net energy generated by pathways, and energy use (or avoided
energy use) contributes to (or reduces) acidification, eutrophication, particulate matter, human and eco-
toxicity, and water consumption. This makes assumptions about displaced energy supply very influential
on final LCA results. Parsing out the effects not dependent upon energy will be important to
understanding the impacts of these pathways as the sources of energy change in the United States.
In contrast, the circularity assessment valued material recovery over energy recovery, and results were
less dependent on assumptions about the current energy mix. Circularity prioritizes pathways that recover
and beneficially use materials to regenerate ecosystems through carbon sequestration, soil health
improvements, and addition of slow-release nutrients. The circularity assessment did not, however,
Chapter 5. Discussion and Conclusions
5-5
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consider the associated environmental impacts and benefits of energy use and net production,
respectively.
Process Emissions and Waste Outputs
The LCA also identified key process emissions from the wasted food pathways beyond those related to
energy use. As noted earlier, sewer/WWT and landfill emit methane from the anaerobic decay of wasted
food. In addition, composting emits ammonia and volatile organic compounds (VOCs); controlled
combustion generates flue gas containing particulate matter and dioxins; landfill may release untreated
leachate causing toxicity; and sewer/WWT (and AD at WRRFs) results in the release of effluent which
may cause eutrophication. The circularity assessment did not comprehensively examine emissions during
the wasted food pathway, from energy use or other processes.
Several pathways can also result in waste outputs that must be sent to landfill or controlled combustion.
For example, ash from controlled combustion is typically landfilled and may contain hazardous
components, and digestate and biosolids from AD and sewer/WWT may be disposed of in a landfill.
Some of the reviewed LCAs consider the effect of waste from controlled combustion in terms of toxicity.
Stack emissions, impurities in the wasted food stream, and energy consumption or avoided energy
production have all been cited as drivers of toxicity impact (Mondello et al. 2017; Mayer et al. 2020;
Albizzati et al. 2021b). Studies of AD assumed land application of digestate or biosolids (i.e., no creation
of waste). In the circularity assessment, pathways were credited for beneficial use of outputs over their
disposal, but the environmental impacts of disposal were not explicitly considered. Pathways with waste
outputs (i.e., AD or sewer/WWT where digestate or biosolids are sent to landfill or controlled combustion;
or sending wasted food directly to landfill or controlled combustion) rank lower than other pathways in the
circularity assessment since resources do not maintain value.
Soil Health
Five wasted food pathways offer the potential to provide carbon and nutrients to soil and improve soil
structure and health - AD, composting, land application, sewer/WWT, and unharvested/plowed in. Unlike
the reviewed LCA studies, circularity assigned value to improvements in soil health and ecosystems from
the application of wasted food or soil amendments made from wasted food. The LCA review's
dependence on standardized quantitative data limited its abilities in this area, and none of the LCAs
reviewed considered soil health or ecosystem regeneration quantitatively.
In LCAs, AD and composting were sometimes credited with replacing manufacture and use of synthetic
fertilizers or peat and/or sequestering carbon by returning wasted food to the soil. When applied, these
credits have a moderate effect on GWP, with their application potentially raising composting to net
negative (beneficial) effect. The sewer/WWT pathway received these credits in two of seven of the
reviewed LCA scenarios.
The circularity assessment was able to incorporate more detailed findings from the scientific literature
about the potential benefits to soil health and ecosystems from these pathways. In addition, the circularity
assessment considered scenarios where nutrient-rich outputs are disposed of, where fertilizer and carbon
sequestration credits should not be applied in LCA.
All the types of soil amendments created from wasted food are better for soil health than synthetic
fertilizers, and all result in less nitrogen loss through leaching, runoff, and volatilization, than synthetic
fertilizers (Brown et al. 2011; Morris et al. 2014; Moller2015; Urra et al. 2019; Ippolito et al. 2021). This is
primarily due to the organic matter content in these amendments - something synthetic fertilizers lack.
Soil organic matter is a widely accepted indicator of soil health as it affects the biological, chemical, and
physical characteristics and ability of soils to provide ecosystem services and support the growth of food,
fiber, and fuel (Urra et al. 2019; Wtzgall et al. 2021; Kopittke et al. 2022; Liptzin et al. 2022). While
synthetic fertilizers can help to increase soil organic matter by promoting crop growth, studies have also
shown that synthetic fertilizers have negative effects on soil organic matter (Mahal et al. 2019).
Application of amendments derived from wasted food builds soil organic matter, which decreases bulk
density, increases porosity, water retention and infiltration, promotes nutrient cycling and retention, and
stabilizes soil aggregates, reducing the risk of erosion. LCAs demonstrate that the use of organic
amendments can reduce global warming potential, acidification, and eutrophication relative to synthetic
fertilizer use. Among the soil amendment types, the composition and degree of benefits vary, with
digestate best able to substitute for synthetic fertilizers and compost best able to build long-term soil
Chapter 5. Discussion and Conclusions
5-6
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health, regenerate ecosystems, and release nutrients slowly overtime. Leaching and runoff of nitrogen
appears to be greater from digestate than compost. Compost can also be less contaminated than
digestate or biosolids (depending on feedstock) due to composting's greater ability to degrade or
decrease the bioavailability of many contaminants (Thakali and MacRae 2021).
5.2 Effects of Wasted Food on Pathway Performance
The findings in this report relate specifically to the management of wasted food in the 11 pathways.
Where possible, the analysis considers the specific properties of food and how they affect a pathway's
impacts and benefits. In many pathways food is not the only feedstock and, in some pathways, like
sewer/WWT, wasted food is never a major feedstock. Wasted food is an ideal feedstock in some
pathways, reinforcing benefits offered by the pathway; while in other cases it might contribute directly to
(or increase) the environmental impacts of a pathway.
For example, energy may be recovered from wasted food through three pathways, at varying efficiencies.
Wasted food is well-suited for AD (due to its moisture content and energy value) and its use with other
feedstocks (e.g., manure or biosolids) provides synergies allowing for more energy generation overall. In
contrast, the moisture of wasted food makes it a poor feedstock for energy generation by controlled
combustion; it may require drying (which uses additional energy), and it produces less energy through
controlled combustion than some other components of MSW. At a landfill, much of the methane produced
by wasted food occurs prior to installation of landfill gas capture systems, leading to GHG emissions
rather than recovered energy.
Wasted food is unique among MSW components in that it is nitrogen-rich, making it valuable for plant
productivity, and carbon-rich, making it advantageous for soil health and providing an opportunity for soil
carbon sequestration when process outputs are used as a soil amendment. However, the nitrogen
content of wasted food can also lead to environmental impacts. For instance, adding wasted food to
sewer/WWT pathway increases energy use during secondary treatment (due to increased biological and
chemical oxygen demand from addition of nutrients) and can increase nutrients released in effluent. Also,
digestate from wasted food is higher in ammonium than other digestates, which can lead to greater
leaching and runoff of nitrogen when digestate is applied to land.
In many cases, more value can be generated by source-separating wasted food before management. For
example, the AD and composting pathways typically require source separation to remove physical
contaminants. Wasted food streams tend to contain fewer pathogens and chemical contaminants like
PFAS or heavy metals than other common feedstocks (e.g., manure or wastewater solids) for the wasted
food pathways. This reduces opportunities for toxicity in pathway outputs, expanding potential uses for
outputs such as soil amendments. In other cases, like controlled combustion, where wasted food is not an
ideal feedstock, wasted food will likely only be managed through this pathway inside a broader waste
stream like MSW. For that reason, decision-makers should consider the broader impacts of controlled
combustion when determining whether to choose it as a wasted food pathway. While wasted food
contains fewer contaminants than some other MSW feedstocks, the combustion of wasted food can lead
to dioxins in flue gas.
Chapter 5. Discussion and Conclusions 5-7
-------
5.3 Synthesizing Results into New Ranking of
Wasted Food Pathways
The two approaches presented in this report - LCA and circularity assessment - are complementary and
together inform the conclusions of this report and the Wasted Food Scale presented in Figure 5-3. EPA's
Wasted Food Scale ranks wasted food pathways from most to least environmentally preferable. The
Scale is based upon each pathway's environmental performance and contribution to a circular economy
and does not consider economic and social factors. Pathways were evaluated based upon the use of
food as a key feedstock wherever possible. The Wasted Food Scale replaces EPA's previous ranking of
wasted food pathways (the Food Recovery Hierarchy).
Feed
Animals
Compost
Anaerobic
Digestion
with beneficial use of
digestate/biosolids
Leave
Unharvested
Prevent Wasted Food
Produce, buy, and serve
only what is needed
Q AVOID
Send Down the Drain,
Landfill, or Incinerate
with or without energy recovery
Donate
Upcycle
Anaerobic Digestion
with disposal of digestate/biosolids
Apply to
the Land
FIGURE 5-3. THE WASTED FOOD SCALE: EPA'S NEW RANKING OF WASTED FOOD PATHWAYS
BASED UPON LCA AND CIRCULARITY ASSESSMENT
Chapter 5. Discussion and Conclusions
5-8
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This scale of the wasted food pathways is divided into tiers, from most preferable (#1 below) to least
preferable (#6 below), based upon the life cycle environmental impacts and contributions toward a
circular economy of each pathway. Pathways are grouped within a tier where this report found levels of
environmental impact and circularity to be similar.
1. Source Reduction: Source reduction demonstrates environmental benefits an order of magnitude
greater than all other pathways (except donation in some cases) by reducing the amount of
additional food that must be produced. The benefits of most other pathways are small relative to
the environmental impacts of food production; thus, they can do little to offset the environmental
impacts of food production. Source reduction can be achieved at any stage of the supply chain,
and source reduction options should be exhausted before other pathways are considered.
2. Donation and Upcycling: Among the pathways considered, donation and upcycling exhibit
benefits closest to those of source reduction. Like source reduction, donation and upcycling can
reduce the amount of additional food that must be produced and, because of this, demonstrate
beneficial performance across all impacts studied. However, unlike source reduction, these two
pathways require additional energy use (e.g., for transportation, cold storage, or processing),
reducing net environmental benefits (i.e., by increasing energy demand, and thus particulate
matter, acidification, eutrophication, water consumption, and human and eco-toxicity if fossil fuels
are used). In addition, researchers estimate that up to 40 percent of donated food may be wasted
(Alexander and Smaje 2008), further reducing benefits of donation relative to source reduction.
An estimate of food waste in upcycling pathway is not available in the literature.
3. Animal Feed and Unharvested/Plowed In: Using wasted food as animal feed can displace the
production of traditional animal feed (e.g., growing soy, corn or barley) which brings substantial
environmental savings. The impacts of recycling wasted food into animal feed are largely due to
energy use (e.g., heat treatment to meet safety standards). If crops would ultimately be wasted
(i.e., not consumed), the unharvested/plowed in pathway provides an opportunity to return
nutrients and carbon directly to the soil and avoid environmental impacts of processing,
packaging and distributing food.
4. Composting and Anaerobic Digestion with beneficial use of digestate/biosolids: Both composting
and AD produce soil amendments with potential to improve soil health, sequester carbon, and
displace some use of synthetic nitrogen fertilizers. Compost, digestate and biosolids (made
through co-digestion) require less energy to make than synthetic fertilizers and, upon application,
release less nitrogen to the environment through air emissions, runoff and leaching. While
compost is typically not applied at rates which would allow complete substitution of synthetic
fertilizers, it can reduce the amount of synthetic fertilizer needed and provide long-term slow
release of nitrogen.
While the level of evidence for long-term soil health benefits, including improved biodiversity,
water holding capacity, and protection against erosion, is strongest for compost, AD can create
both energy and soil amendments, demonstrating the "cascading uses" principle of circularity,
hence we have ranked them equally in the scale. (Note: Wasted food sent down the drain and
through the sewer to a WRRF that has AD is defined as the sewer/WWT pathway, not the AD
pathway, and is ranked separately.)
5. Land Application and Anaerobic Digestion with disposal of digestate/biosolids: When the nutrient-
rich output of AD (i.e., digestate or biosolids) is disposed (typically by landfill) rather than
beneficially used, the AD pathway ranks lower. All the LCAs of AD reviewed in this paper
assumed beneficial use of the digestate or biosolids, thus their findings reflect beneficial use
rather than disposal of the digestate or biosolids. When digestate and biosolids are disposed we
must subtract those benefits and add the environmental impacts of landfilling.
AD can create more net energy from wasted food than the other energy-producing pathways,
thus it is ranked higher than controlled combustion and landfill; however, unlike some other
renewable energy resources (e.g., solar or wind), combustion during AD generates criteria air
pollutant emissions similar to natural gas combustion.
Chapter 5. Discussion and Conclusions
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The benefits and impacts of land application of food processing waste streams (i.e., raw wasted
food) may vary widely based upon the composition of the wasted food and more research is
needed. In many cases, more benefits could be achieved by managing the waste stream through
other pathways such as AD with beneficial use of digestate.
6. Controlled Combustion, Landfill, and SewerAAAA/T: Sewer/WWT and landfill stand out for their
sizeable methane emissions. Wasted food decays rapidly in anaerobic conditions. Sewer
transport allows for uncontrolled methane releases and wasted food at landfills begins to
decompose prior to capping and placement of landfill gas capture systems. These emissions far
exceed the benefits of energy recovery technologies (i.e., AD at WRRFs or gas capture systems
at landfills) or the carbon sequestration potential of landfills. WRRFs with AD have lower global
warming potential than those without, but the difference is not big enough to affect the final
ranking of the sewer/WWT pathway. Sewer/WWT and landfill have other environmental impacts
as well, including eutrophication from effluent releases and water pollution from untreated
leachate, respectively. While sewer/WWT offers the possibility of nutrient recovery, biosolids are
currently disposed of roughly half the time. Given that wasted food sent down the drain results in
methane emissions from sewer transport and increased energy use during secondary treatment
at the WRRF, it is probably more environmentally beneficial to source-separate wasted food and
collect and transport it directly to anaerobic digesters rather than to send it down the drain to a
WRRF with AD.
While controlled combustion performs better than landfill and sewer/WWT across most categories
in the LCA review, it fails to contribute to circularity beyond modest energy production. The
moisture content of wasted food makes it a poor feedstock for energy generation by controlled
combustion; it may require drying (which uses additional energy), and it produces less energy
through controlled combustion than some other components of MSW. Research in multiple
studies indicates that removal of wasted food from MSW streams before incineration can reduce
energy use, increase calorific value, and improve efficiency of controlled combustion (Song et al.
2013; He et al. 2014; Rajagopal et al. 2014; Erses Yay 2015; Lee et al. 2020). Controlled
combustion also generates hazardous waste (fly ash) and can create localized air pollution
impacts.
Key Conclusions
While the performance gap between the most and least preferable pathways - source reduction,
donation, and upcycling compared to incineration, landfill, and sewerAA/WT - is considerable, the
differences in environmental performance among the middle-performing pathways are much smaller. For
example, in the LCA review the median performance of all six of the remaining pathways (AD, animal
feed, composting, controlled combustion, land application, and unharvested/plowed in) are beneficial or
near neutral for global warming potential. While all pathways use energy and release CO2, and some
pathways release other GHGs (CH4 and N2O in composting and CH4 in AD), this is generally offset by the
benefits of avoided production of energy, food, animal feed and/or fertilizer, avoided fertilizer use, and/or
carbon sequestration. However, these five pathways each exhibit one or more important tradeoffs across
environmental impact categories and/or between circularity and environmental performance. In the
circularity assessment, a similar pattern emerged, with many of the same pathways rising to rank highest
(source reduction, donation, upcycling and animal feed) for maintaining food's highest value and lowest
due to it recovering little value from wasted food (landfill and incineration), with smaller differences in the
pathways in between.
/As the U.S. becomes less dependent on fossil fuels for energy, the environmental value of producing
energy from wasted food will decrease. The LCA results are driven largely by global warming potential
and energy demand, due to widely available data and, in the case of energy demand, the effect of energy
use effect on many of the selected indicators. Energy use by pathways contributes to more than half of
the indicators assessed in the LCA chapter of this report, including energy demand, acidification,
eutrophication, particulate matter, and human and eco-toxicity performance. Thus, the energy mix
assumed (when calculating effect of energy use and/or avoided energy production) has a substantial
effect on the outcome of LCA studies. As the U.S. increases the use of lower-impact energy sources in its
portfolio, the environmental "cost" of energy use and the environmental "benefit" of avoiding energy
production will both decrease. This would likely, for instance, lower the environmental performance of
controlled combustion and AD but improve the environmental performance of composting. For example, if
Chapter 5. Discussion and Conclusions
5-10
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energy produced by AD was displacing wind power, rather than fossil fuel-derived power, the pathway
would be net positive (increase GHG emissions), rather than net negative (reduce GHG emissions), for
global warming potential (Slorach et al. 2019a).
The benefits of most pathways are small relative to the impacts of food production; thus, they can do little
to offset the original impact For example, anaerobic digestion, the most efficient energy recovery
pathway for wasted food, recovers only around 20 percent of the energy required to produce each unit of
food.
The environmental performance of individual pathways is highly variable and is affected by operating
parameters, such as technology type or temperature and pre- and post-treatment of outputs. For
example, composting is well-studied but inconsistently modeled by LCA, and process emissions are
variable due to composting method, facility management, and environmental conditions. Also, for many
pathways, pre- and post-treatment can add substantial impacts which may or may not be included in
modeling. For example, a study of de-packaging showed its energy use was greater than that of
collection and transportation for AD and composting pathways (Mondello et al. 2017). Additionally,
digestate and biosolids from AD and sewer/WWT pathways often require post-treatment, which can be
energy-intensive, before they can be beneficially used.
Recycling wasted food into soil amendments offers opportunities to make long-term improvements in soil
health and help regenerate ecosystems by recovering nitrogen and carbon and returning them to the soil.
When food cannot be used to nourish humans, the composting pathway, including composting of
digestate and biosolids, offers the greatest benefits in this area. The carbon in wasted food can be used
to make long-term improvements in soil structure and health or to generate energy. Application of soil
amendments derived from wasted food builds soil organic matter, which decreases bulk density,
increases porosity, water retention and infiltration, promotes nutrient cycling and retention, and stabilizes
soil aggregates, reducing the risk of erosion. These improvements are regenerative and can help to
improve the resilience of agricultural systems in the face of climate change. According to the IPCC, soil
moisture conservation, reclamation of degraded soils, and soil carbon management are effective
practices for climate change mitigation and adaptation (IPCC 2023). Synthetic fertilizers lack the organic
matter content of these amendments and cannot provide similar benefits, other than indirectly through
promoting crop growth. In addition, the nitrogen in wasted food can be used to provide nutrients to crops
over the short or long-term in lieu of synthetic fertilizers. The application of organic amendments made
from wasted food (compost, digestate, or biosolids) lose less nitrogen through volatilization, leaching, or
runoff than synthetic fertilizers, reducing acidification, eutrophication, particulate matter emissions, and
global warming potential.
The circularity and environmental performance of wasted food pathways are generally positively
correlated. While circularity does not guarantee environmental performance, for the wasted food
pathways, circularity and environmental performance are not in conflict, and progress can be made on
both fronts with similar pathways. When the LCA review considered all 11 environmental indicators
presented in this report (including soil health), the results are not wildly different than those of the
circularity assessment. The one exception is the sewer/WWT pathway. While this pathway can contribute
to a circular economy by recovering and beneficially using nutrients in biosolids, that potential must be
balanced by consideration of the magnitude of sewer methane emissions.
Emerging pathways including hydrothermal carbonization (HTC); pyrolysis, torrefaction and gasification;
and rendering were excluded from the main LCA and circularity analyses due to a lack of available
environmental data. The pathway technologies and key features of each are introduced in Appendix E. All
the considered emerging pathways have the potential to produce high value end products including
electricity, solid and liquid biofuels, chemical feedstock, and feed and fertilizer products. Each end
product has the potential to displace traditional sources of these materials and the net environmental
performance of these pathways depends strongly on how they perform relative to the avoided product
options. For example, HTC produces a coal-like solid fuel that has been shown to generate net
environmental benefits in the acidification and GWP impact categories when displacing coal (Berge et al.
2015). The authors note that if other energy mixes are being displaced, a consideration of environmental
priorities is necessary. As noted elsewhere in this report, such considerations are likely to be of
increasing importance as electricity grid mixes move towards reliance on cleaner fuels. Still, any pathway
with the potential to convert a low value waste stream into a high value product that can reduce reliance
on fossil resources holds environmental promise. Given the complexity of these processes, their range of
Chapter 5. Discussion and Conclusions
5-11
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potential operating conditions and pre- and post-treatment options, more research is needed to
understand the key factors driving environmental impact, product yield, and process economics such that
suitable use cases can be identified.
Chapter 5. Discussion and Conclusions 5-12
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CHAPTER 6
IMPLICATIONS AND RESEARCH GAPS
This chapter provides context for the conclusions presented in the previous chapter - comparing the new
Wasted Food Scale to other wasted food hierarchies, suggesting ways to use the new scale and
implications of the scale, and noting priority research needs to better inform decision-makers and
policymakers about the 11 wasted food pathways.
6.1 Comparing Conclusions to Other Hierarchies
The Wasted Food Scale presented in this report is based upon the latest science regarding the wasted
food pathways' life cycle environmental impacts and contributions toward a circular economy. A
comparison of the scale to the previous EPA ranking (i.e., the Food Recovery Hierarchy) and to two
international hierarchies is presented in Figure 6-1. These hierarchies may be based on different criteria
than this hierarchy.
Previous U.S. EPA Wasted Food Pathway Ranking
The new Wasted Food Scale agrees with the previous EPA ranking (i.e., the Food Recovery Hierarchy)
developed in the 1990s in several ways. The scale confirms the position of source reduction, donation,
and animal feed as the most desirable pathways. It also confirms the position of landfills in the bottom tier
of the hierarchy. Differences between the Wasted Food Scale and the previous EPA ranking include:
Pathways included: The Wasted Food Scale considers four additional common wasted food
pathways— land application, sewer/WWT, unharvested/plowed in, and upcycling—but removes
the broad pathway of "industrial uses" since there is wide variation in the environmental
performance of wasted food pathways that could fall under this umbrella. Anaerobic digestion,
now the most common industrial use, is considered on its own in the scale. Since the time of the
previous EPA ranking's development, many new pathways which could be considered "industrial
uses" have emerged. Information on some of these emerging pathways can be found in Appendix
E.
Value of end products: The Wasted Food Scale moves composting to the same tier as anaerobic
digestion due to the numerous well-researched benefits of applying compost, including providing
slow-release nutrients, improving soil health, sequestering carbon, and contributing to
regeneration of disturbed ecosystems. The scale also distinguishes within pathways based upon
the end use (land application or disposal) of the products created, such as digestate or biosolids.
International Wasted Food Hierarchies
The two international hierarchies most cited in the literature are from the United Kingdom (UK) and the
European Commission's (EC) Bioeconomy Knowledge Center (EC 2018; DEFRA 2021). Like the scale
presented in this report, both prioritize source reduction, donation, and animal feed above other
pathways. They also rank sewer/WWT and landfill in the bottom tier. However, they both rank controlled
combustion with energy recovery higher than sewer or landfill, rather than including it in the same tier as
the hierarchy in this report does.
The international hierarchies also both rank AD and composting in the same tier, like the scale presented
in this report but unlike the previous EPA ranking. The EC framed the two pathways as "nutrient recovery"
(which ranked higher than "energy recovery" in the hierarchy) so it appears the EC assumes that
digestate or biosolids would be beneficially used and not disposed of. This is another approach to the
distinguishing of AD with and without beneficial use of digestate/biosolids, akin to the presentation in this
report's hierarchy.
Chapter 6. Implications and Research Gaps
6-1
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Only the UK hierarchy includes land application, and it is ranked below AD and composting and above
controlled combustion, landfill, or sewer, consistent with the findings of this report. While this report
ranked upcycling, both the UK and EC included what we define in this report as upcycling (i.e., making
food products for humans from wasted food) as part of a broader category, making comparison with its
ranking in this report's hierarchy difficult. The EC ranks a "valorization" pathway, and the UK ranks a
"biomaterials" pathway, both of which include the creation of food and non-food products like chemicals.
Chapter 6. Implications and Research Gaps 6-2
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More Previous EPA
preferred Ranking (1990s)
Source
Reduction
1
Donation
EPA Wasted Food
Scale (2023)
Source
Reduction
United Kingdom European
(2014) Commission (2018)
Source
Reduction
Source
Reduction
mU Animal Feed
Donation
Upcycling
331 Animal Feed
%SJ Donation
k§® Donation
G91 Animal Feed
Animal Feed
Unharvested/
Plowed In
Upcycling
"process surplus food to
make biomaterials"
Upcycling
"revalorize into value-
added products by
processes that keep the
high value of the molecule
bonds of the material''
U AD
"industrial uses"
J AD
with beneficial use of
digestate
Ega Composting
111 AD
Composting
|J ad
with"nutrients recovery"
Composting
Composting
Mad
with digestate
landfill/incineration
Land Application
Land Application
Controlled
combustion
Controlled
combustion
with "energy recovery"
l|l AD
"energy recovery" with
digestate disposal
gS3l Landfill
Controlled
combustion
Less
preferred
Controlled
combustion
Landfill
Landfill
Landfill
Sewer/WWT
|S||
Sewer/WWT
IfM Sewer/WWT
FIGURE 6-1. COMPARISON OF WASTED FOOD PATHWAY HIERARCHIES
Pathways shown in the same box in a column were ranked equally.
Data sources: UK DEFRA (2021); European Commission Bioeconomy Knowledge Center (2018 EC 2018)
Chapter 6. Implications and Research Gaps
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6.2 Using the Hierarchy
The literature provides two key insights into the most effective use of waste hierarchies to achieve
environmental improvements.
Users of the Wasted Food Scale should be encouraged to begin by considering the top tier,
exhausting source reduction options before moving on to the next tier, rather than aiming to move
up a tier from their current location (Van Ewijk and Stegemann 2016).
The audience for the Wasted Food Scale should include decision-makers from outside as well as
within the waste management community. Once waste is discarded and collected (and under
control of waste managers), opportunities for source reduction, donation and upcycling have
passed, and opportunities for recycling may be limited (e.g., due to mixed collection).
In addition, a variety of factors beyond environmental performance may limit and/or influence decisions
about which pathways to choose for management of wasted food in a specific context, including:
Wasted food characteristics such as edibility, homogeneity, contamination, packaging, and
content of moisture, energy, oil, nutrients, protein, and carbon;
Stage of food supply chain at which food is wasted;
Availability of local infrastructure and end-markets for recycled materials made from wasted food
(e.g., soil amendments or energy);
Cost;
Local policies, such as bans on landfilling wasted food, requirements to recycle food, climate or
waste goals;
Local priorities, such as concern about hazardous air pollutants or eutrophication of local
waterbodies;
Localized environmental impacts and environmental justice considerations; and
Stakeholder preferences.
Given these considerations, along with the potential differences in performance due to operating
parameters, it is not possible to definitively rank the pathways across all potential conditions. The scale in
this report is meant only to inform the user of the environmental performance of the most common
pathways.
6.3 Implications
The evidence presented in this report suggests that, to achieve greater environmental performance
regarding wasted food, the focus should be on (1) increasing source reduction, donation and upcycling
and (2) diverting wasted food from landfills and wastewater resource recovery facilities (with or without
anaerobic digesters). Source reduction (and often donation) have environmental benefits an order of
magnitude greater than other pathways and can be implemented at many stages of the supply chain.
However, as discussed in EPA's Farm to Kitchen report, donation cannot be relied on as sole solution,
since not all wasted food is fit for donation and the amount of wasted food generated in the U.S. far
outweighs the needs of food-insecure Americans (U.S. EPA 2021c).
The alignment of current public policies with the hierarchy should be examined. Often policies focus more
upon landfill diversion and donation than source reduction (Van Ewijk and Stegemann 2016;
Redlingshofer et al. 2020), missing opportunities to encourage greater environmental savings. Non-food
policies, such as renewable energy goals and incentives, can also discourage source reduction of wasted
food (Redlingshofer et al. 2020), and these potential trade-offs should be studied. Also, the effect of
landfill diversion policies should be assessed to ensure wasted food is not shifting from landfill to
sewer/WWT, which this report found to have similar magnitude of global warming potential performance.
Chapter 6. Implications and Research Gaps
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6.4 Research Gaps
Although numerous studies have been published examining the environmental impacts and value of
wasted food pathways, data gaps persist. Filling these data gaps is essential to achieving the 2030 Food
Loss and Waste Reduction Goal and the National Recycling Goal with maximum environmental benefits.
We see two areas as top priorities for further laboratory and field research:
Methane generation from sewer conveyance and wastewater treatment of wasted food. Further
research is needed on the amount of methane generated from wasted food in the sewer/WWT
pathway under a variety of conditions (e.g., residence time, oxygenation, temperature). Current
research indicates that between 6% and 10% of volatile solids or COD, respectively, may be
released as methane during sewer transport (Parry and WERF 2012; Edwards et al. 2018). More
robust measurements of sewer methane emissions are needed and should be incorporated into
LCAs of this pathway to increase confidence in pathway impacts.
Environmental benefits and impacts of applying wasted food or wasted food-derived amendments
to soil. Five wasted food pathways have the potential to provide nutrients and other organic
matter to soil and improve soil health directly: the unharvested/plowed in pathway leaves crops in
the field; land application applies raw wasted food to soil; composting creates compost to be
applied to soil; and AD and sewer/WWT create digestate or biosolids which can be used as soil
amendments. These pathways can also have negative environmental impacts through nitrogen
losses or contaminants. Further research is needed to understand the environmental benefits and
impacts of these outputs, relative to one another and relative to synthetic fertilizer, in situations
where these outputs are used as partial or full replacement for fertilizer. Soil health benefits
requiring further study include increasing carbon sequestration, biodiversity, water percolation
and storage, porosity and nutrient retention. Environmental impacts requiring further study include
nitrogen losses to the environment (through ammonia or nitrous oxide emissions and nitrate
leaching and/or runoff), as well as risks to human health or the environment from contaminants
that may be present in soil amendments. Research should extend to uses beyond application to
agricultural soil, such as site reclamation or remediation and green infrastructure. Additional work
is then needed to incorporate these findings into the LCA framework.
Additional areas that warrant further research include:
Effect of technology type and specific management and operational practices on pathway
performance, especially for composting and AD pathways. Current limitations make it difficult to
compare pathways at a higher level of resolution that considers technology type or specific
management and operational practices. Emerging technologies such as nutrient recovery from
WRRF effluent and heat recovery from composting provide more options for facilities to reduce
their environmental impact. For pathways with wide variability in operational choices, better
understanding the environmental effects of choices at the facility level could improve
environmental performance by guiding sound management.
Environmental impacts of two understudied pathways - upcycling and land application. More
research is needed to understand the typical range of operating conditions, inputs and outputs,
and environmental impacts and benefits that characterize these two understudied pathways. For
land application, understanding the effects of different wasted food characteristics (e.g., nutrient,
carbon, or oil content) on soil health (e.g., biodiversity, bulk density, and carbon sequestration)
and the environment (e.g., potential for nitrogen losses) could help optimize for which wasted
food streams this pathway is selected. Upcycling is an emerging pathway that shows great
potential to avoid the impacts of additional food production. More research is needed on
environmental performance to increase confidence in current results.
Environmental impacts of emerging pathways. Emerging pathways such as HTC, pyrolysis,
torrefaction and gasification as well as the established pathway of rendering were excluded from
the main LCA and circularity analyses due to a lack of available environmental data. The pathway
technologies and key features of each are introduced in Appendix E. These processes are
complex and can be operated under a range of conditions (e.g., temperature and pressure) and
in combination with various pre- and post-treatment steps. Research is needed to help
commercialize these systems for use processing wasted food and more broadly. Additional
Chapter 6. Implications and Research Gaps
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environmental research could help to identify applications and operational contexts (e.g.,
feedstock mix, energy source, product mix) that yield broad environmental benefits or reductions
in impact.
Effect of future energy mix on pathway performance. Investments in wasted food pathways will
necessarily be considerable and determine wasted food management methods for decades to
come. By focusing primarily on current energy mix, LCAs and other environmental assessments
of wasted food pathways might make recommendations that are not supported in future
conditions. For example, citing other research, Slorach et al. (2020) noted that many of the
benefits of AD depend on environmental credits for replacing fertilizer and energy production,
which can be expected to change in coming years. Incorporating future energy mix scenarios in
more wasted food management LCAs will help increase confidence in the expected change in
pathway performance due to this important driver of impact. While directionality of results is easily
predicted (impacts of energy use decrease, while benefits of producing energy decrease), how
pathways compare to one another is not.
Effect of PFAS and microplastic contaminants. As discussed elsewhere in the report, PFAS and
microplastic contamination in wasted food streams prior to entering pathways can affect the
suitability of wasted food for management pathways. The potential for wasted food management
to contribute to broader environmental and human health impacts is of concern, too, if the
pathway can reintroduce contaminants to the environment. The risk associated with emerging
contaminants, such as microplastics and PFAS, in wasted food pathways has not been well-
studied and may be difficult to quantify. As techniques to measure these contaminants become
more effective and more available, they should be considered with respect to the environmental
performance of wasted food pathways. In addition, research is needed on the potential
introduction of microplastics to wasted food streams during pre-processing activities such as use
of depackaging equipment.
Local implications of wasted food management. This report has focused on high-level comparison
of wasted food pathways. We have considered impacts at a variety of spatial scales. For
example, GWP impacts occur globally, some acidifying compounds may be transported at
continental scales, and other compounds may only travel tens or hundreds of kilometers. Human
and ecotoxicity impacts, for example, tend to fall in the latter category. Toxicity was not
consistently reported in the literature, preventing comparisons across studies. Regardless, LCA
(and thus this study) is best suited to evaluate broad impacts; for questions about impacts to
specific communities, risk assessment is often used. Any wasted food pathway can have impacts
to the local community. While negative impacts are most often associated with landfilling and
controlled combustion of solid waste (e.g., Hooks et al. (2020)), emissions, odors, noise, etc. are
part of wasted food management. Existing or proposed wasted food management should also be
considered from an environmental justice perspective.
Benefits of replacing peat with compost, digestate or biosolids. Avoiding the use of peat soil
amendments is assessed infrequently within the literature but demonstrates potential to generate
considerable avoided product benefits for the compost and AD pathways. More LCA research is
needed to establish a consensus around the magnitude of benefit that results from replacing peat
as a growing media. At this time the extent to which digestate and compost are being used in this
application is unclear and modeling of both pathways would benefit from market research on this
use of soil amendments.
Alignment of current public policies with the hierarchy and trade-offs between environmental
goals and other policy priorities.
Chapter 6. Implications and Research Gaps
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CHAPTER 7
REFERENCES
Adetunji, A. T., B. Ncube, R. Mulidzi, and F. B. Lewu. 2020. Management impact and benefit of
cover crops on soil quality: A review. Soil and Tillage Research 204: 104717.
doi:https://doi.org/10.1016/j.still.2020.104717.
Ahamed, A., K. Yin, B. J. H. Ng, F. Ren, V. W.-C. Chang, and J.-Y. Wang. 2016. Life cycle
assessment of the present and proposed food waste management technologies from
environmental and economic impact perspectives. Journal of Cleaner Production 131:
607-614. doi: 10.1016/j.jclepro.2016.04.127.
Albizzati, P. F., D. Tonini, and T. F. Astrup. 2021a. A quantitative sustainability assessment of
food waste management in the European Union. Environmental Science & Technology
55. American Chemical Society: 16099-16109. doi:10.1021/acs.est.1c03940.
Albizzati, P. F., D. Tonini, and T. F. Astrup. 2021b. High-value products from food waste: An
environmental and socio-economic assessment. The Science of the Total Environment
755: 142466. doi: 10.1016/j.scitotenv.2020.142466.
Alewell, C., B. Ringeval, C. Ballabio, D. A. Robinson, P. Panagos, and P. Borrelli. 2020. Global
phosphorus shortage will be aggravated by soil erosion. Nature Communications 11:
4546. doi: 10.1038/s41467-020-18326-7.
Alexander, C., and C. Smaje. 2008. Surplus retail food redistribution: An analysis of a third
sector model. Resources, Conservation and Recycling 52: 1290-1298.
doi: 10.1016/j.resconrec.2008.07.009.
Alexander, P., C. Brown, A. Arneth, J. Finnigan, D. Moran, and M. D. A. Rounsevell. 2017.
Losses, inefficiencies and waste in the global food system. Agricultural Systems 153:
190-200. doi:10.1016/j.agsy.2017.01.014.
Alexander, R. 2012. Digestate utilization in the U.S. BioCycle: the Organics Recycling Authority.
Al-Kaisi, M. M., and X. Yin. 2005. Tillage and crop residue effects on soil carbon and carbon
dioxide emission in corn-soybean rotations. Journal of Environmental Quality 34: 437-
445. doi: 10.2134/jeq2005.0437.
Al-Rumaihi, A., G. McKay, H. R. Mackey, and T. Al-Ansari. 2020. Environmental impact
assessment of food waste management using two composting techniques. Sustainability
12 (4): 1595. doi: 10.3390/su12041595.
American Biogas Council. 2018. Biogas industry market snapshot.
Angouria-Tsorochidou, E., S. Walk, I. Korner, and M. Thomsen. 2023. Environmental and
economic assessment of household food waste source-separation efficiency in a
German case study. Cleaner Waste Systems 5: 100092.
doi: 10.1016/j.clwas.2023.100092.
Chapter 7. References
7-1
-------
ASCE. 2021. 2021 Infrastructure report card: Wastewater. ASCE's 2021 infrastructure report
card.
Askri, A., P. Laville, A. Tremier, and S. Houot. 2016. Influence of origin and post-treatment on
greenhouse gas emissions after anaerobic digestate application to soil. Waste and
Biomass Valorization 7: 293-306. doi:10.1007/s12649-015-9452-6.
Baek, G., D. Kim, J. Kim, H. Kim, and C. Lee. 2020. Treatment of cattle manure by anaerobic
co-digestion with food waste and pig manure: Methane yield and synergistic effect.
International Journal of Environmental Research and Public Health 17.
doi: 10.3390/ijerphl 7134737.
Baker, G. A., L. C. Gray, M. J. Harwood, T. J. Osland, and J. B. C. Tooley. 2019. On-farm food
loss in northern and central California: Results of field survey measurements.
Resources, Conservation and Recycling 149: 541-549.
doi: 10.1016/j.resconrec.2019.03.022.
Baptista, A. I., and A. Perovich. 2019. U.S. municipal solid waste incinerators: An industry in
decline. New York, NY: Tishman Environment and Design Center at The New School.
Bare, J. 2011. TRACI 2.0: The tool for the reduction and assessment of chemical and other
environmental impacts 2.0. Clean Technologies and Environmental Policy 13: 687-696.
doi: 10.1007/sl 0098-010-0338-9.
Bare, J. C., G. A. Norris, D. W. Pennington, and T. E. McKone. 2003. TRACI: The tool for the
reduction and assessment of chemical and other environmental impacts. Journal of
Industrial Ecology 6: 49-78. doi: 10.1162/108819802766269539.
Bartocci, P., M. Zampilli, F. Liberti, V. Pistolesi, S. Massoli, G. Bidini, and F. Fantozzi. 2020.
LCA analysis of food waste co-digestion. Science of the Total Environment 709: 136187.
Batuecas, E., T. Tommasi, F. Battista, V. Negro, G. Sonetti, P. Viotti, D. Fino, and G. Mancini.
2019. Life cycle assessment of waste disposal from olive oil production: Anaerobic
digestion and conventional disposal on soil. Journal of Environmental Management 237:
94-102. doi:10.1016/j.jenvman.2019.02.021.
Bayart, J.-B., C. Bulle, L. Deschenes, M. Margni, S. Pfister, F. Vince, and A. Koehler. 2010. A
framework for assessing off-stream freshwater use in LCA. The International Journal of
Life Cycle Assessment 15: 439-453. doi: 10.1007/s11367-010-0172-7.
Beecher, N., J. Beecher, J. Burke-Wells, M. Lono-Batura, N. Goldstein, G. Kester, and B.
Toffey. 2022. National Biosolids Data Project: Biosolids management in the U. S.
Beghin-Tanneau, R., F. Guerin, M. Guiresse, D. Kleiber, and J. D. Scheiner. 2019. Carbon
sequestration in soil amended with anaerobic digested matter. Soil & Tillage Research
192: 87-94. doi: 10.1016/j.still.2019.04.024.
Belcher, D., and B. Aldrich. 2006. Regulations governing land application of food waste in New
York State. Ithaca, N.Y.: Cornell University Manure Management.
http://northeast.manuremanagement.cornell.edu/Pages/General_Docs/Fact_Sheets/Lan
d_Application_Food_Waste_Regs_2006_factsheet.pdf. Accessed August 6 2021.
Chapter 7. References
7-2
-------
Benavente, V., A. Fullana, and N. D. Berge. 2017. Life cycle analysis of hydrothermal
carbonization of olive mill waste: Comparison with current management approaches.
Journal of Cleaner Production 142: 2637-2648. doi: 10.1016/j.jclepro.2016.11.013.
Beretta, C., M. Stucki, and S. Hellweg. 2017. Environmental impacts and hotspots of food
losses: Value chain analysis of Swiss food consumption. Environmental Science &
Technology 51: 11165-11173. doi:10.1021/acs.est.6b06179.
Berge, N. D., L. Li, J. R. V. Flora, and K. S. Ro. 2015. Assessing the environmental impact of
energy production from hydrochar generated via hydrothermal carbonization of food
wastes. Waste Management 43: 203-217. doi:10.1016/j.wasman.2015.04.029.
Bernstad, A. K., A. Canovas, and R. Valle. 2017. Consideration of food wastage along the
supply chain in lifecycle assessments: A mini-review based on the case of tomatoes.
Waste Management & Research: The Journal of the International Solid Wastes and
Public Cleansing Association, ISWA 35 (1): 29-39. doi: 10.1177/0734242X16666945.
Bernstad Saraiva Schott, A. K., and T. Andersson. 2015. Food waste minimization from a life-
cycle perspective. Journal of Environmental Management 147: 219-226.
doi: 10.1016/j.jenvman.2014.07.048.
Bernstad Saraiva Schott, A., H. Wenzel, and J. la Cour Jansen. 2016. Identification of decisive
factors for greenhouse gas emissions in comparative life cycle assessments of food
waste management - An analytical review. Journal of Cleaner Production 119:13-24.
doi: 10.1016/j.jclepro.2016.01.079.
Bessou, C., A. Tailleur, C. Godard, A. Gac, J. L. de la Cour, J. Boissy, P. Mischler, A. Caldeira-
Pires, et al. 2020. Accounting for soil organic carbon role in land use contribution to
climate change in agricultural LCA: which methods? Which impacts? The International
Journal of Life Cycle Assessment 25: 1217-1230. doi: 10.1007/s11367-019-01713-8.
Blanco-Canqui, H., and R. Lai. 2009. Crop residue removal impacts on soil productivity and
environmental quality. Critical Reviews in Plant Sciences 28: 139-163.
doi: 10.1080/07352680902776507.
Bocken, N. M. P., I. de Pauw, C. Bakker, and B. van der Grinten. 2016. Product design and
business model strategies for a circular economy. Journal of Industrial and Production
Engineering 33. Taylor & Francis: 308-320. doi:10.1080/21681015.2016.1172124.
Bolzonella, D., P. Pavan, P. Battistoni, and F. Cecchi. 2003. The under sink garbage grinder: A
friendly technology for the environment. Environmental Technology 24: 349-359.
doi: 10.1080/09593330309385567.
Boulay, A.-M., J. Bare, L. Benini, M. Berger, M. J. Lathuilliere, A. Manzardo, M. Margni, etal.
2018. The WULCA consensus characterization model for water scarcity footprints:
Assessing impacts of water consumption based on available water remaining (AWARE).
The International Journal of Life Cycle Assessment 23: 368-378. doi: 10.1007/s11367-
017-1333-8.
Brown, S., and N. Beecher. 2019. Carbon accounting for compost use in urban areas. Compost
Science and Utilization 27: 227-239. doi: 10.1080/1065657X.2019.1674224.
Chapter 7. References
7-3
-------
Brown, S., K. Kurtz, A. Bary, and C. Cogger. 2011. Quantifying benefits associated with land
application of organic residuals in Washington State. Environmental Science &
Technology 45: 7451-7458. doi:10.1021/es2010418.
Brown, S., A. Carpenter, and L. Souther. 2020. What are composting VOCs? And how are they
measured? BioCycle: the Organics Recycling Authority.
California, S. of. 2023. Short-Lived Climate Pollutants (SLCP): Organic waste methane
emissions reductions. CalRecycle Home Page, https://calrecycle.ca.gov/climate/slcp/.
Accessed August 15.
CalRecycle. 2019. SB 1383 Infrastructure and market analysis. DRRRR-2019-1652. California
Department of Resources Recycling and Recovery.
CARB. 2015. ARB Emissions Inventory Methodology for Composting Facilities. California Air
Resources Board.
CARB. 2017. Method for estimating greenhouse gas emission reductions from diversion of
organic waste from landfills to compost facilities. California Air Resources Board.
Carey, R. O., and K. W. Migliaccio. 2009. Contribution of wastewater treatment plant effluents to
nutrient dynamics in aquatic systems: A review. Environmental Management 44: 205-
217. doi: 10.1007/s00267-009-9309-5.
Case, S. D. C., and L. S. Jensen. 2019. Nitrogen and phosphorus release from organic wastes
and suitability as bio-based fertilizers in a circular economy. Environmental Technology
40: 701-715. doi: 10.1080/09593330.2017.1404136.
Cerda, A., A. Artola, X. Font, R. Barrena, T. Gea, and A. Sanchez. 2018. Composting of food
wastes: Status and challenges. Bioresource Technology 248: 57-67.
doi: 10.1016/j.biortech.2017.06.133.
Cesaro, A. 2021. The valorization of the anaerobic digestate from the organic fractions of
municipal solid waste: Challenges and perspectives. Journal of Environmental
Management 280: 111742. doi:https://doi.org/10.1016/j.jenvman.2020.111742.
Charles, A., P. Rochette, J. K. Whalen, D. A. Angers, M. H. Chantigny, and N. Bertrand. 2017.
Global nitrous oxide emission factors from agricultural soils after addition of organic
amendments: A meta-analysis. Agriculture, Ecosystems & Environment 236: 88-98.
doi:10.1016/j.agee.2016.11.021.
Chiu, S. L. H., and I. M. C. Lo. 2018. Identifying key process parameters for uncertainty
propagation in environmental life cycle assessment for sewage sludge and food waste
treatment. Journal of Cleaner Production 174: 966-976.
doi:10.1016/j.jclepro.2017.10.164.
Cho, B. H., B. H. Nam, J. An, and H. Youn. 2020. Municipal solid waste incineration (MSWI)
ashes as construction materials-A review. Materials (Switzerland) 13.
doi: 10.3390/ma13143143.
Chapter 7. References
7-4
-------
Ciais, P., C. Sabine, G. Bala, L. Bopp, V. Brovkin, J. Canadell, A. Chhabra, et al. 2013. Carbon
and other biogeochemical cycles. In Climate change 2013: The physical science basis.
Contribution of Working Group I to the fifth assessment report of the Intergovernmental
Panel on Climate Change, ed. T. F. Stocker, D. Qin, G.-K. Platner, M. Tignor, S. K.
Allen, J. Boschung, A. Nauels, et al., 465-570. Cambridge, U.K., and New York, NY:
Cambridge University Press.
Claassen, R., M. Bowman, J. McFadden, D. Smith, and S. Wallander. 2018. Tillage intensity
and conservation cropping in the United States. Economic Information Bulletin Number
197. U.S. Department of Agriculture.
Clavreul, J., D. Guyonnet, and T. H. Christensen. 2012. Quantifying uncertainty in LCA-
modelling of waste management systems. Waste Management 32: 2482-2495.
doi:10.1016/j.wasman.2012.07.008.
Cobo, S., A. Dominguez-Ramos, and A. Irabien. 2018. Trade-offs between nutrient circularity
and environmental impacts in the management of organic waste. Environmental Science
& Technology 52: 10923-10933. doi:10.1021/acs.est.8b01590.
Cogger, C. G., A. I. Bary, E. A. Myhre, and A.-M. Fortuna. 2013. Biosolids applications to tall
fescue have long-term influence on soil nitrogen, carbon, and phosphorus. Journal of
Environmental Quality 42: 516-522. doi: 10.2134/jeq2012.0269.
Cooke, C. M., L. Gove, F. A. Nicholson, H. F. Cook, and A. J. Beck. 2001. Effect of drying and
composting biosolids on the movement of nitrate and phosphate through repacked soil
columns under steady-state hydrological conditions. Chemosphere 44: 797-804.
doi:https://doi.org/10.1016/S0045-6535(00)00293-9.
Corona, A., M. Ambye-Jensen, G. C. Vega, M. Z. Hauschild, and M. Birkved. 2018. Techno-
environmental assessment of the green biorefinery concept: Combining process
simulation and life cycle assessment at an early design stage. Science of the Total
Environment 635: 100-111. doi: 10.1016/j.scitotenv.2018.03.357.
Corona, A., A. Ernstoff, C. Segato, and M. Zgola. 2020. Greenhouse gas emissions of food
waste: Methodology. ReFED. URL: https://refed.com/downloads/quantis-ghg-
methodology-vfinal-2020-11-03.pdf
Crolla, A., C. Kinsley, and E. Pattey. 2013. 13 - Land application of digestate. In The Biogas
Handbook, ed. A. Wellinger, J. Murphy, and D. Baxter, 302-325. Woodhead Publishing.
Damgaard, A., C. Riber, T. Fruergaard, T. Hulgaard, and T. H. Christensen. 2010. Life-cycle-
assessment of the historical development of air pollution control and energy recovery in
waste incineration. In Thermal treatments of solid wastes, special issue, Waste
Management 30: 1244-1250. doi:10.1016/j.wasman.2010.03.025.
Damiani, M., T. Pastorello, A. Carlesso, S. Tesser, and E. Semenzin. 2021. Quantifying
environmental implications of surplus food redistribution to reduce food waste. Journal of
Cleaner Production 289: 125813. doi: 10.1016/j.jclepro.2021.125813.
De Pascale, A., R. Arbolino, K. Szopik-Depczynska, M. Limosani, and G. loppolo. 2021. A
systematic review for measuring circular economy: The 61 indicators. Journal of Cleaner
Production 281: 124942. doi:10.1016/j.jclepro.2020.124942.
Chapter 7. References
7-5
-------
DEFRA. 2021. Statutory guidance: Food and drink waste hierarchy: Deal with surplus and
waste. London, U.K.: Department for Environmental Food & Rural Affairs (DEFRA).
Del Borghi, A., L. Moreschi, and M. Gallo. 2020. Circular economy approach to reduce water-
energy-food nexus. Current Opinion in Environmental Science & Health 13: 23-28.
doi:https://doi.org/10.1016/j.coesh.2019.10.002.
Delgado-Rodriguez, M., M. Ruiz-Montoya, I. Giraldez, R. Lopez, E. Madejon, and M. J. Diaz.
2011. Influence of control parameters in VOCs evolution during MSW trimming residues
composting. Journal of Agricultural and Food Chemistry 59: 13035-13042.
doi: 10.1021/jf2036017.
Do, Q., A. Ramudhin, C. Colicchia, A. Creazza, and D. Li. 2021. A systematic review of
research on food loss and waste prevention and management for the circular economy.
International Journal of Production Economics 239: 108209.
doi: 10.1016/j.ijpe.2021.108209.
Dou, Z., J. D. Toth, and M. L. Westendorf. 2018. Food waste for livestock feeding: Feasibility,
safety, and sustainability implications. Global Food Security 17: 154-161.
doi:10.1016/j.gfs.2017.12.003.
Duren, R. M., A. K. Thorpe, K. T. Foster, T. Rafiq, F. M. Hopkins, V. Yadav, B. D. Bue, etal.
2019. California's methane super-emitters. Nature 575: 180-184. doi: 10.1038/s41586-
019-1720-3.
Dutta, S., M. He, X. Xiong, and D. C. W. Tsang. 2021. Sustainable management and recycling
of food waste anaerobic digestate: A review. Bioresource Technology. 125915.
doi: https://doi. org/10.1016/j.biortech.2021.125915.
Ebner, J. H., R. A. Labatut, M. J. Rankin, J. L. Pronto, C. A. Gooch, A. A. Williamson, and T. A.
Trabold. 2015. Lifecycle greenhouse gas analysis of an anaerobic codigestion facility
processing dairy manure and industrial food waste. Environmental science & technology
49. United States: 11199-11208. doi:10.1021/acs.est.5b01331.
EC. 2018. Review of the 2012 European bioeconomy strategy. European Commission
Directorate-General for Research and Innovation.
EC, 2018. 2018. Directive 2018/851 of the European Parliament and of the Council of 30 May
2018 Amending Directive 2008/98/EC on Waste. Vol. 2018/851.
Edwards, J., M. Othman, E. Crossin, and S. Burn. 2017. Anaerobic co-digestion of municipal
food waste and sewage sludge: A comparative life cycle assessment in the context of a
waste service provision. Bioresource Technology 223: 237-249.
doi:10.1016/j.biortech.2016.10.044.
Edwards, J., M. Othman, E. Crossin, and S. Burn. 2018. Life cycle assessment to compare the
environmental impact of seven contemporary food waste management systems.
Bioresource Technology (England) 248: 156-173. doi:10.1016/j.biortech.2017.06.070.
Elevitch, C. R., D. N. Mazaroli, and D. Ragone. 2018. Agroforestry standards for regenerative
agriculture. Sustainability 10. doi: 10.3390/su10093337.
Chapter 7. References
7-6
-------
Elginoz, N., K. Khatami, I. Owusu-Agyeman, and Z. Cetecioglu. 2020. Life cycle assessment of
an innovative food waste management system. Frontiers in Sustainable Food Systems
4. doi:10.3389/fsufs.2020.00023.
Elia, V., M. G. Gnoni, and F. Tornese. 2017. Measuring circular economy strategies through
index methods: A critical analysis. Journal of Cleaner Production 142: 2741-2751.
doi:https://doi.org/10.1016/j.jclepro.2016.10.196.
Ellen MacArthur Foundation. 2013. Towards the circular economy.
Ellen Macarthur Foundation. 2019. Cities and circular economy for food.
Embrandiri, A., R. P. Singh, H. M. Ibrahim, and A. A. Ramli. 2012. Land application of biomass
residue generated from palm oil processing: Its potential benefits and threats. The
Environmentalist 32: 111-117. doi:10.1007/s10669-011-9367-0.
Environmental and Energy Study Institute. 2013. Fact sheet: Landfill methane.
EREF. 2023. Composting Facility Survey. Environmental Research and Education Foundation.
Eriksson, M. and J. Spangberg. 2017. Carbon footprint and energy use of food waste
management options for fresh fruit and vegetables from supermarkets. In Urban mining
and circular economy, special issue, Waste Management 60: 786-799.
doi:10.1016/j.wasman.2017.01.008.
Eriksson, M., L. Bartek, K. Lofkvist, C. Malefors, and M. E. Olsson. 2021. Environmental
assessment of upgrading horticultural side streams—The case of unharvested broccoli
leaves. Sustainability 13: 5327. doi:10.3390/su13105327.
Ermolaev, E., C. Sundberg, M. Pell, and H. Jonsson. 2014. Greenhouse gas emissions from
home composting in practice. Bioresource Technology (England) 151: 174-182.
doi: 10.1016/j.biortech.2013.10.049.
Erses Yay, A. S. 2015. Application of life cycle assessment (LCA) for municipal solid waste
management: a case study of Sakarya. Journal of Cleaner Production 94: 284-293.
doi:https://doi.org/10.1016/j.jclepro.2015.01.089.
Fantke, P., L. Aylward, J. Bare, W. A. Chiu, R. Dodson, R. Dwyer, A. Ernstoff, B. Howard, et al.
2018. Advancements in life cycle human exposure and toxicity characterization.
Environmental Health Perspectives 126: 125001. doi:10.1289/EHP3871.
FAO. 2022. Soils for nutrition: State of the art. Food and Agricultural Organization of the United
Nations.
Frischknecht, R., H. Althaus, C. Bauer, G. Doka, T. Heck, N. Jungbluth, D. Kellenberger, and T.
Nemecek. 2007. The environmental relevance of capital goods in life cycle assessments
of products and services. The International Journal of Life Cycle Assessment 12 (1): 1-
11. doi: 10.1065/LCA2007.02.309.
Funari, V., J. Makinen, J. Salminen, R. Braga, E. Dinelli, and H. Revitzer. 2017. Metal removal
from Municipal Solid Waste Incineration fly ash: A comparison between chemical
leaching and bioleaching. Waste Management 60. Special Thematic Issue: Urban
Mining and Circular Economy: 397-406. doi:10.1016/j.wasman.2016.07.025.
Chapter 7. References
7-7
-------
Gallo, F., A. Manzardo, D. Camana, A. Fedele, and A. Scipioni. 2023. Integration of a circular
economy metric with life cycle assessment: methodological proposal of compared agri-
food products. The International Journal of Life Cycle Assessment. doi: 10.1007/s11367-
022-02130-0.
Garcia, A. J., M. B. Esteban, M. C. Marquez, and P. Ramos. 2005. Biodegradable municipal
solid waste: Characterization and potential use as animal feedstuffs. Waste
Management 25 (8): 780-787. doi:10.1016/j.wasman.2005.01.006.
Geisendorf, S., and F. Pietrulla. 2018. The circular economy and circular economic concepts—a
literature analysis and redefinition. Thunderbird International Business Review 60: 771-
782. doi: 10.1002/tie.21924.
Geissdoerfer, M., P. Savaget, N. M. P. Bocken, and E. J. Hultink. 2017. The circular economy-
A new sustainability paradigm? Journal of Cleaner Production 143: 757-768.
doi:https://doi.org/10.1016/j.jclepro.2016.12.048.
Gilbert, J. 2023. Personal communication. Carbon Clarity.
Gilbert, J., M. Ricci-Jurgensen, and A. Ramola. 2020. Benefits of compost and anaerobic
digestate when applied to soil. International Solid Waste Association.
Gillman, A., D. C. Campbell, and E. S. Spang. 2019. Does on-farm food loss prevent waste?
Insights from California produce growers. Resources, Conservation and Recycling 150:
104408. doi: 10.1016/j.resconrec.2019.104408.
Giraud, R. J., P. H. Taylor, and C. Huang. 2021. Combustion operating conditions for municipal
waste-to-energy facilities in the U.S. Waste Management 132: 124-132.
doi:10.1016/j.wasman.2021.07.015.
Goedkoop, M., R. Heijungs, M. A. J. Huijbregts, A. D. Schryver, J. Struijs, and R. van Zelm.
2013. ReCiPe 2008: A life cycle impact assessment method which comprises
harmonised category indicators at the midpoint and the endpoint level; First edition
(version 1.08); Report 1: Characterisation. The Netherlands: Ministry of Housing, Spatial
Planning, and Environment (VROM).
Goldstein, N. 2017. The state of organics recycling. BioCycle: the Organics Recycling Authority.
Goldstein, N. 2020. Compost Markets in The U.S. BioCycle: the Organics Recycling Authority.
Gonzalez, R., J. G. Rosas, D. Blanco, R. Smith, E. J. Martinez, R. Pastor-Bueis, and X. Gomez.
2020. Anaerobic digestion of fourth range fruit and vegetable products: Comparison of
three different scenarios for its valorisation by life cycle assessment and life cycle
costing. Environmental Monitoring and Assessment 192: 551. doi: 10.1007/s 10661-020-
08521-w.
Goss, M. J., A. Tubeileh, and D. Goorahoo. 2013. A review of the use of organic amendments
and the risk to human health. Advances in Agronomy 120: 275-379. doi:10.1016/B978-
0-12-407686-0.00005-1.
Gravuer, K., S. Gennet, and H. L. Throop. 2019. Organic amendment additions to rangelands: A
meta-analysis of multiple ecosystem outcomes. Global Change Biology 25: 1152-1170.
doi:10.1111/gcb. 14535.
Chapter 7. References
7-8
-------
Grigatti, M., L. Barbanti, M. U. Hassan, and C. Ciavatta. 2020. Fertilizing potential and C02
emissions following the utilization of fresh and composted food-waste anaerobic
digestates. Science of The Total Environment 698: 134198.
doi:10.1016/j.scitotenv.2019.134198.
Grippo, V., S. Romano, and A. Vastola. 2019. Multi-criteria Evaluation of Bran Use to Promote
Circularity in the Cereal Production Chain. Natural Resources Research 28.
doi: 10.1007/sl 1053-019-09457-w.
Guinee, J., M. Gorree, R. Heijungs, G. Huppes, R. Kleijn, A. de Koning, L. van Oers, et al. 2002.
Handbook on life cycle assessment: Operational guide to the ISO standards (CML 2002
documentation). Dordrecht, The Netherlands: Kluwer Academic Publishers.
Gwyther, C. L., A. P. Williams, P. N. Golyshin, G. Edwards-Jones, and D. L. Jones. 2011. The
environmental and biosecurity characteristics of livestock carcass disposal. Waste
Management 31: 767-778. doi:10.1016/j.wasman.2010.12.005.
Hanson, C., B. Lipinski, K. Robertson, D. Dias, I. Gavilan, P. Greverath, S. Ritter, etal. 2016.
Food loss and waste accounting and reporting standard, version 1.0. Food Loss and
Waste Protocol.
Harder, R., M. Giampietro, and S. Smukler. 2021. Towards a circular nutrient economy. A novel
way to analyze the circularity of nutrient flows in food systems. Resources, Conservation
and Recycling 172: 105693. doi:10.1016/j.resconrec.2021.105693.
Havukainen, J., and E. Dace. 2023. Chapter 8 - Waste to energy and circular economy: the
case of anaerobic digestion. In Sustainable and Circular Management of Resources and
Waste Towards a Green Deal, ed. M. N. Vara Prasad and M. Smol, 105-115. Elsevier.
He, C., K. Wang, Y. Yang, and J.-Y. Wang. 2014. Utilization of sewage-sludge-derived
hydrochars toward efficient cocombustion with different-rank coals: Effects of subcritical
water conversion and blending scenarios. Energy & Fuels 28: 6140-6150.
doi: 10.1021/ef501386g.
Heller, M. 2019. Waste not, want not: Reducing food loss and waste in North America through
life cycle-based approaches. Washington, DC: United Nations Environment Programme.
Henderson, A. D. 2015. Eutrophication. In Life cycle impact assessment, ed. M. Z. Hauschild
and M. A. J. Huijbregts, 177-196. LCA Compendium—The Complete World of Life Cycle
Assessment. Netherlands: Springer Science & Business Media.
Hodge, K. L., J. W. Levis, J. F. DeCarolis, and M. A. Barlaz. 2016. Systematic evaluation of
industrial, commercial, and institutional food waste management strategies in the United
States. Environmental Science & Technology 50: 8444-8452.
doi: 10.1021/acs.est.6b00893.
Hoehn, D., M. Margallo, J. Laso, I. Ruiz-Salmon, A. Fernandez-Rios, C. Campos, I. Vazquez-
Rowe, R. Aldaco, et al. 2021. Water footprint assessment of food loss and waste
management strategies in Spanish regions. Sustainability 13: 7538.
doi: 10.3390/su13147538.
Chapter 7. References
7-9
-------
Hooks, S. K., M. Hrysko, C. Strickland, B. Dixon, I. M. Karaye, K. Kirsch, and J. Horney. 2020.
Can global policy impact local environmental justice? Using CASPER to assess
perceived health effects of an incinerator. Human Ecology 48 (1): 119-125.
doi: 10.1007/sl 0745-020-00133-9.
Huang, Y., C. Zhao, B. Gao, S. Ma, Q. Zhong, and L. Wang. 2022. Life cycle assessment and
society willingness to pay indexes of food waste-to-energy strategies. Journal of
Environmental Management 305: 114364. doi: 10.1016/j.jenvman.2021.114364.
Huijbregts, M. A. J., Z. J. N. Steinmann, P. M. F. Elshout, G. Stam, F. Verones, M. Vieira, M.
Zijp, A. Hollander, R. van Zelm. 2017. ReCiPe 2016: A harmonised life cycle impact
assessment method at midpoint and endpoint level. The International Journal of Life
Cycle Assessment 22: 138-147. doi:10.1007/s11367-016-1246-y.
IPCC. 2013. Climate change 2013: The physical science basis. Contribution of Working Group I
to the fifth assessment report of the Intergovernmental Panel on Climate Change.
Cambridge, U.K., and New York, NY: Cambridge University Press.
IPCC. 2023. Climate change 2023: Synthesis Report. A Report of the Intergovernmental Panel
on Climate Change. Contribution of Working Groups I, II and III to the Sixth Assessment
Report of the Intergovernmental Panel on Climate Change. Edited by H. Lee and J.
Romero. Geneva, Switzerland: Intergovernmental Panel on Climate Change.
Ippolito, J. A., K. A. Barbarick, M. W. Paschke, and R. B. Brobst. 2010. Infrequent composted
biosolids applications affect semi-arid grassland soils and vegetation. Journal of
Environmental Managements. Elsevier: 1123-1130.
Ippolito, J. A., T. F. Ducey, K. Diaz, and K. A. Barbarick. 2021. Long-term biosolids land
application influences soil health. Science of The Total Environment 791: 148344.
doi:https://doi.org/10.1016/j.scitotenv.2021.148344.
Ishangulyyev, R., S. Kim, and S. H. Lee. 2019. Understanding food loss and waste—Why are
we losing and wasting food? Foods (Switzerland) 8. doi:10.3390/foods8080297.
ISO. 2006a. ISO 14040:2006 Environmental management—Life cycle assessment—Principles
and framework. The International Organization for Standardization.
ISO. 2006b. ISO 14044:2006 Environmental management—Life cycle assessment—
Requirements and guidelines. The International Organization for Standardization.
ISO. 2018. ISO 14067:2018 Greenhouse gases—Carbon footprint of products—Requirements
and guidelines for quantification. The International Organization for Standardization.
Jackel, U., K. Thummes, and P. Kampfer. 2005. Thermophilic methane production and oxidation
in compost. FEMS Microbiology Ecology 52: 175-184.
doi: 10.1016/j.femsec.2004.11.003.
Jain, P., J. Wally, T. G. Townsend, M. Krause, and T. Tolaymat. 2021. Greenhouse gas
reporting data improves understanding of regional climate impact on landfill methane
production and collection. PLOS One 16 (2): e0246334.
doi: 10.1371/journal.pone.0246334.
Chapter 7. References
7-10
-------
Jin, Y., T. Chen, and H. Li. 2012. Hydrothermal treatment for inactivating some hygienic
microbial indicators from food waste-amended animal feed. Journal of the Air & Waste
Management Association 62 (7): 810-816. doi:10.1080/10962247.2012.676999.
Jolliet, O., M. Margni, R. Charles, S. Humbert, J. Payet, G. Rebitzer, and R. K. Rosenbaum.
2003. IMPACT 2002+: A new life cycle impact assessment methodology. International
Journal of Life Cycle Assessment 8: 324-330.
Jurgilevich, A., T. Birge, J. Kentala-Lehtonen, K. Korhonen-Kurki, J. Pietikainen, L. Saikku, and
H. Schosler. 2016. Transition towards circular economy in the food system.
Sustainability 8. doi: 10.3390/su8010069.
Kapo, K. E., M. Paschka, R. Vamshi, M. Sebasky, and K. McDonough. 2017. Estimation of U.S.
sewer residence time distributions for national-scale risk assessment of down-the-drain
chemicals. Science of the Total Environment 603-604: 445-452.
doi:10.1016/j.scitotenv.2017.06.075.
Katami, T., A. Yasuhara, and T. Shibamoto. 2004. Formation of dioxins from incineration of
foods found in domestic garbage. Environmental Science & Technology 38: 1062-1065.
doi: 10.1021/es030606y.
Kaur, G., L. Luo, G. Chen, and J. W. C. Wong. 2019. Integrated food waste and sewage
treatment—A better approach than conventional food waste-sludge co-digestion for
higher energy recovery via anaerobic digestion. Bioresource Technology 289: 121698.
doi: 10.1016/j. biortech.2019.121698.
Keng, Z. X., S. Chong, C. G. Ng, N. I. Ridzuan, S. Hanson, G.-T. Pan, P. L. Lau, et al. 2020.
Community-scale composting for food waste: A life-cycle assessment-supported case
study. Journal of Cleaner Production 261: 121220. doi: 10.1016/j.jclepro.2020.121220.
Khoshnevisan, B., P. Tsapekos, M. Alvarado-Morales, S. Rafiee, M. Tabatabaei, and I.
Angelidaki. 2018. Life cycle assessment of different strategies for energy and nutrient
recovery from source sorted organic fraction of household waste. Journal of Cleaner
Production 180: 360-374. doi: 10.1016/j.jclepro.2018.01.198.
Kibblewhite, M. G., K. Ritz, and M. J. Swift. 2008. Soil health in agricultural systems.
Philosophical Transactions of the Royal Society B: Biological Sciences 363: 685-701.
doi: 10.1098/rstb.2007.2178.
Kim, M., M. M. I. Chowdhury, G. Nakhla, and M. Keleman. 2017. Synergism of co-digestion of
food wastes with municipal wastewater treatment biosolids. Waste management 61.
United States: 473-483. doi:10.1016/j.wasman.2016.10.010.
Kim, M., G. Nakhla, and M. Keleman. 2019. Modeling the impact of food wastes on wastewater
treatment plants. Journal of Environmental Management 237: 344-358.
doi: 10.1016/j.jenvman.2019.02.065.
Kirchherr, J., D. Reike, and M. Hekkert. 2017. Conceptualizing the circular economy: An
analysis of 114 definitions. Resources, Conservation and Recycling 127: 221-232.
doi: 10.1016/j.resconrec.2017.09.005.
Klinglmair, M., and M. Thomsen. 2020. Using food waste in organic fertilizer: modelling biogenic
carbon sequestration with associated nutrient and micropollutant loads. Sustainability
12. Multidisciplinary Digital Publishing Institute: 7399. doi:10.3390/su12187399.
Chapter 7. References
7-11
-------
Koenig, R. T., C. G. Cogger, and A. I. Bary. 2011. Dryland winter wheat yield, grain protein, and
soil nitrogen responses to fertilizer and biosolids applications. Applied and
Environmental Soil Science 2011. Hindawi: e925462. doi: 10.1155/2011/925462.
Komilis, D. P., and R. K. Ham. 2004. Life-cycle inventory of municipal solid waste and yard
waste windrow composting in the United States. Journal of Environmental Engineering
130. American Society of Civil Engineers: 1390-1400. World. doi:10.1061/(ASCE)0733-
9372(2004)130:11(1390).
Kopittke, P. M., A. A. Berhe, Y. Carrillo, T. R. Cavagnaro, D. Chen, Q.-L. Chen, M. Roman
Dobarco, F. A. Dijkstra, et al. 2022. Ensuring planetary survival: the centrality of organic
carbon in balancing the multifunctional nature of soils. Critical Reviews in Environmental
Science and Technology 52: 4308^324. doi: 10.1080/10643389.2021.2024484.
Kopsahelis, A., C. Kourmentza, C. Zafiri, and M. Kornaros. 2019. Life cycle assessment (LCA)
of end-of-life dairy products (EoL-DPs) valorization via anaerobic co-digestion with agro-
industrial wastes for biogas production. Journal of Chemical Technology &
Biotechnology 94: 3687-3697. doi:https://doi.org/10.1002/jctb.6174.
Kraj, K., and M. Smol. 2023. Chapter 25 - How to achieve climate neutrality—the impact of
fertilizer usage on climate change. In Sustainable and Circular Management of
Resources and Waste Towards a Green Deal, ed. M. N. Vara Prasad and M. Smol,
349-356. Elsevier. doi:10.1016/B978-0-323-95278-1.00028-0.
Kumar, K., C. J. Rosen, S. C. Gupta, and M. McNearney. 2009. Land application of sugar beet
by-products: Effects on nitrogen mineralization and crop yields. Journal of Environmental
Quality 38: 319-328. doi: 10.2134/jeq2008.0005.
Kummu, M., H. de Moel, M. Porkka, S. Siebert, O. Varis, and P. J. Ward. 2012. Lost food,
wasted resources: Global food supply chain losses and their impacts on freshwater,
cropland, and fertiliser use. Science of the Total Environment 438: 477-489.
doi: 10.1016/j.scitotenv.2012.08.092.
Kutos, S., E. Strieker, A. Cooper, R. Ryals, J. Creque, M. Machmuller, M. Kroegar, and W. L.
Silver. 2023. Compost amendment to enhance carbon sequestration in rangelands.
Journal of Soil and Water Conservation 78. Soil and Water Conservation Society: 163-
177. doi: 10.2489/jswc.2023.00072.
Lai, R., R.F. Follett, B.A. Stewart, and J.M. Kimble. 2007. Soil carbon sequestration to mitigate
climate change and advance food security. Soil Science: 172: 943-956. doi:
10.1097/ss.0b013e31815cc498
Lazcano, C., A. Tsang, T. A. Doane, G. S. Pettygrove, W. R. Horwath, and M. Burger. 2016.
Soil nitrous oxide emissions in forage systems fertilized with liquid dairy manure and
inorganic fertilizers. Agriculture, Ecosystems & Environment 225: 160-172.
doi:https://doi.org/10.1016/j.agee.2016.04.009.
Le Pera, A., M. Sellaro, and E. Bencivenni. 2022a. Composting food waste or digestate?
Characteristics, statistical and life cycle assessment study based on an Italian
composting plant. Journal of Cleaner Production 350: 131552.
doi:https://doi.org/10.1016/j.jclepro.2022.131552.
Chapter 7. References
7-12
-------
Le Pera, A., M. Sellaro, E. Bencivenni, and F. D'Amico. 2022b. Environmental sustainability of
an integrate anaerobic digestion-composting treatment of food waste: Analysis of an
Italian plant in the circular bioeconomy strategy. Waste Management 139: 341-351.
doi:https://doi. org/10.1016/j.wasman.2021.12.042.
Le Pera, A., M. Sellaro, F. Sicilia, R. Ciccoli, B. Sceberras, C. Freda, E. Fanelli, and G.
Cornacchia. 2023. Environmental and economic impacts of improper materials in the
recycling of separated collected food waste through anaerobic digestion and
composting. Science of the Total Environment 880: 163240.
doi: 10.1016/j.scitotenv.2023.163240.
Lee, D., E. Sonmez, M. I. Gomez, and X. Fan. 2017. Combining two wrongs to make two rights:
Mitigating food insecurity and food waste through gleaning operations. Food Policy 68:
40-52. doi: 10.1016/j.foodpol.2016.12.004.
Lee, E., D. S. B. L. Oliveira, L. S. B. L. Oliveira, E. Jimenez, Y. Kim, M. Wang, S. J. Ergas, and
Q. Zhang. 2020. Comparative environmental and economic life cycle assessment of high
solids anaerobic co-digestion for biosolids and organic waste management. Water
Research (England) 171: 115443. doi: 10.1016/j.watres.2019.115443.
Lee, U., J. Han, and M. Wang. 2017. Evaluation of landfill gas emissions from municipal solid
waste landfills for the life-cycle analysis of waste-to-energy pathways. Journal of Cleaner
Production 166: 335-342. doi:10.1016/j.jclepro.2017.08.016.
Lehmann, J., and M. Kleber. 2015. The contentious nature of soil organic matter. Nature 528:
60-68. doi:10.1038/nature 16069.
Lehmann, J., D. A. Bossio, I. Kogel-Knabner, and M. C. Rillig. 2020. The concept and future
prospects of soil health. Nature Reviews Earth & Environment 1: 544-553.
doi: 10.1038/S43017-020-0080-8.
Leib, E. B., O. Balkus, C. Rice, M. Maley, R. Taneja, R. Cheng, N. Civita, and T. Alvoid. 2016.
Leftovers For Livestock: A legal guide for using food scraps as animal feed. The Harvard
Food Law and Policy Clinic and the Food Recovery Project, University of Arkansas
School of Law. https://chlpi.org/wp-content/uploads/2013/12/Leftovers-for-Livestock_A-
Legal-Guide_August-2016.pdf. Accessed August 29 2022.
Levis, J. W., and M. A. Barlaz. 2011. What is the most environmentally beneficial way to treat
commercial food waste? Environmental Science & Technology (United States) 45:
7438-7444. doi: 10.1021/es103556m.
Lin, L., F. Xu, X. Ge, and Y. Li. 2018. Improving the sustainability of organic waste management
practices in the food-energy-water nexus: A comparative review of anaerobic digestion
and composting. Renewable and Sustainable Energy Reviews 89: 151-167.
doi: 10.1016/j.rser.2018.03.025.
Lin, Z., J. K. Ooi, and K. S. Woon. 2022. An integrated life cycle multi-objective optimization
model for health-environment-economic nexus in food waste management sector.
Science of The Total Environment 816: 151541. doi:10.1016/j.scitotenv.2021.151541.
Lindgreen, E. R., G. Mondello, R. Salomone, F. Lanuzza, and G. Saija. 2021. Exploring the
effectiveness of grey literature indicators and life cycle assessment in assessing circular
economy at the micro level: a comparative analysis. International Journal of Life Cycle
Assessment 26: 2171-2191. doi:10.1007/s 11367-021-01972-4.
Chapter 7. References
7-13
-------
Liptzin, D., C. E. Norris, S. B. Cappellazzi, G. M. Bean, M. Cope, K. L. H. Greub, E. L. Rieke, P.
W. Tracy, et al. 2022. An evaluation of carbon indicators of soil health in long-term
agricultural experiments. Soil Biology and Biochemistry 172: 108708.
doi: https://doi.Org/10.1016/j.soilbio.2022.108708.
Lombardi, M., and M. Costantino. 2021. A hierarchical pyramid for food waste based on a social
innovation perspective. Sustainability 13: 4661. doi: 10.3390/su 13094661.
Lopez, V. M., F. B. De la Cruz, and M. A. Barlaz. 2016. Chemical composition and methane
potential of commercial food wastes. Waste Management 56: 477-490.
doi:10.1016/j.wasman.2016.07.024.
Lu, J., and S. Xu. 2021. Post-treatment of food waste digestate towards land application: A
review. Journal of Cleaner Production 303: 127033. doi: 10.1016/j.jclepro.2021.127033.
Mahal, N. K., W. R. Osterholz, F. E. Miguez, H. J. Poffenbarger, J. E. Sawyer, D. C. Oik, S. V.
Archontoulis, and M. J. Castellano. 2019. Nitrogen fertilizer suppresses mineralization of
soil organic matter in maize agroecosystems. Frontiers in Ecology and Evolution 7.
doi: 10.3389/fevo.2019.00059.
Makarichi, L., W. Jutidamrongphan, and K. Techato. 2018. The evolution of waste-to-energy
incineration: A review. Renewable and Sustainable Energy Reviews 91: 812-821.
doi: 10.1016/j.rser.2018.04.088.
Mancini, E., and A. Raggi. 2021. A review of circularity and sustainability in anaerobic digestion
processes. Journal of Environmental Management 291: 112695.
doi: 10.1016/j.jenvman.2021.112695.
Mattsson, J., A. Hedstrom, and M. Viklander. 2014. Long-term impacts on sewers following food
waste disposer installation in housing areas. Environmental Technology 35: 2643-2651.
doi: 10.1080/09593330.2014.915346.
Mattsson, J., A. Hedstrom, R. M. Ashley, and M. Viklander. 2015. Impacts and managerial
implications for sewer systems due to recent changes to inputs in domestic
wastewater—A review. Journal of Environmental Management 161: 188-197.
doi: 10.1016/j.jenvman.2015.06.043.
Mayer, F., R. Bhandari, and S. Gath. 2019. Critical review on life cycle assessment of
conventional and innovative waste-to-energy technologies. Science of the Total
Environment 672: 708-721. doi: 10.1016/j.scitotenv.2019.03.449.
Mayer, F., R. Bhandari, S. A. Gath, H. Himanshu, and N. Stobernack. 2020. Economic and
environmental life cycle assessment of organic waste treatment by means of incineration
and biogasification. Is source segregation of biowaste justified in Germany? Science of
the Total Environment 721: 137731. doi: 10.1016/j.scitotenv.2020.137731.
Moinard, V., F. Levavasseur, and S. Houot. 2021. Current and potential recycling of exogenous
organic matter as fertilizers and amendments in a French peri-urban territory.
Resources, Conservation and Recycling 169: 105523.
doi:https://doi.org/10.1016/j.resconrec.2021.105523.
Moller, K. 2015. Effects of anaerobic digestion on soil carbon and nitrogen turnover, N
emissions, and soil biological activity. A review. Agronomy for Sustainable Development
35: 1021-1041. doi: 10.1007/s13593-015-0284-3.
Chapter 7. References
7-14
-------
Momayez, F., K. Karimi, and M. J. Taherzadeh. 2019. Energy recovery from industrial crop
wastes by dry anaerobic digestion: A review. Industrial Crops and Products 129: 673-
687. doi:https://doi.org/10.1016/j.indcrop.2018.12.051.
Mondello, G., R. Salomone, G. loppolo, G. Saija, S. Sparacia, and M. C. Lucchetti. 2017.
Comparative LCA of alternative scenarios for waste treatment: The case of food waste
production by the mass-retail sector. Sustainability 9: 827. doi:10.3390/su9050827.
Moore, D. P., N. P. Li, L. P. Wendt, S. R. Castaneda, M. M. Falinski, J.-J. Zhu, C. Song, Z. J.
Ren, et al. 2023. Underestimation of Sector-Wide Methane Emissions from United
States Wastewater Treatment. Environmental Science & Technology 57: 4082-4090.
doi: 10.1021/acs.est.2c05373.
Moraga, G., S. Huysveld, F. Mathieux, G. A. Blengini, L. Alaerts, K. Van Acker, S. de Meester,
and J. Dewulf. 2019. Circular economy indicators: What do they measure? Resources,
Conservation and Recycling 146: 452-461.
doi:https://doi.org/10.1016/j.resconrec.2019.03.045.
Morais, T. G., R. F. M. Teixeira, C. Lauk, M. C. Theurl, W. Winiwarter, A. Mayer, L. Kaufmann,
H. Haberl, et al. 2021. Agroecological measures and circular economy strategies to
ensure sufficient nitrogen for sustainable farming. Global Environmental Change 69:
102313. doi:https://doi.org/10.1016/j.gloenvcha.2021.102313.
Morelli, B., S. Cashman, S. Arden, X. C. Ma, J. Turgeon, J. Garland, and D. Bless. 2019. Life
cycle assessment and cost analysis of municipal wastewater treatment expansion
options for food waste anaerobic co-digestion. EPA/600/R-19/094. Washington, DC:
U.S. Environmental Protection Agency, Office of Research and Development.
Morelli, B., S. Cashman, X. C. Ma, J. Turgeon, S. Arden, and J. Garland. 2020. Environmental
and cost benefits of co-digesting food waste at wastewater treatment facilities. Water
Science and Technology: A Journal of the International Association on Water Pollution
Research 82: 227-241. doi: 10.2166/wst.2020.104.
Morris, J. 2014. Evaluation of climate, energy, and soils impacts of selected food discards
management systems. Oregon Department of Environmental Quality.
Morris, J., S. Brown, M. Cotton, and H. Scott Matthews. 2017. Life-cycle assessment
harmonization and soil science ranking results on food-waste management methods.
Environmental Science & Technology 51: 5360-5367. doi:10.1021/acs.est.6b06115.
Morseletto, P. 2020. Restorative and regenerative: Exploring the concepts in the circular
economy. Journal of Industrial Ecology 24: 763-773.
doi:https://doi.org/10.1111/jiec. 12987.
Moshtaghian, H., K. Bolton, and K. Rousta. 2021. Challenges for upcycled foods: definition,
inclusion in the food waste management hierarchy and public acceptability. Foods 10:
2874. doi: 10.3390/foodsl0112874.
Mu, D., N. Horowitz, M. Casey, and K. Jones. 2017. Environmental and economic analysis of an
in-vessel food waste composting system at Kean University in the U.S. Waste
Management 59: 476-486. doi:10.1016/j.wasman.2016.10.026.
Chapter 7. References
7-15
-------
Murphy, J. D., and N. M. Power. 2006. A technical, economic and environmental comparison of
composting and anaerobic digestion of biodegradable municipal waste. Journal of
Environmental Science and Health 41: 865-879. doi: 10.1080/10934520600614488.
Murray, A., K. Skene, and K. Haynes. 2017. The circular economy: An interdisciplinary
exploration of the concept and application in a global context. Journal of Business Ethics
140: 369-380. doi: 10.1007/s10551-015-2693-2.
Myhre, G., D. Shindell, F.-M. Breon, W. Collins, J. Fuglestvedt, J. Huang, D. Koch, et al. 2013.
Anthropogenic and natural radiative forcing. In Climate change 2013: The physical
science basis. Contribution of Working Group I to the fifth assessment report of the
Intergovernmental Panel on Climate Change, ed. T. F. Stocker, D. Qin, G.-K. Plattner,
M. Tignor, S. K. Allen, J. Boschung, A. Nauels, et al., 659-740. Cambridge, U.K., and
New York, NY: Cambridge University Press.
NARA. 2019. The story of rendering. North American Renderers Association.
National Research Council. 2000. Waste incineration and public health. Washington, DC: The
National Academies Press.
Nayak, A., and B. Bhushan. 2019. An overview of the recent trends on the waste valorization
techniques for food wastes. Journal of Environmental Management 233: 352-370.
doi:10.1016/j.jenvman.2018.12.041.
Nicholson, F., A. Bhogal, L. Cardenas, D. Chadwick, T. Misselbrook, A. Rollett, M. Taylor, R.
Thorman, and J. Williams. 2017. Nitrogen losses to the environment following food-
based digestate and compost applications to agricultural land. Environmental Pollution
228: 504-516. doi:10.1016/j.envpol.2017.05.023.
Nick Hacheney and Sally Brown. 2017. Correctional Facility Adopts Multiple Food Scraps
Practices. BioCycle: the Organics Recycling Authority. October.
NRCS and Agricultural BMP Task Force. 2017. Manual of best management practices (BMPs)
for agriculture in New Hampshire. Concord, NH: New Hampshire Department of
Agriculture, Markets, and Food.
NYSDOH. 2019. Important things to know about landfill gas. New York State Department of
Health.
O'Connor, J., S. A. Hoang, L. Bradney, S. Dutta, X. Xiong, D. C. W. Tsang, K. Ramadass, A.
Vinu, et al. 2021. A review on the valorisation of food waste as a nutrient source and soil
amendment. Environmental Pollution 272: 115985. doi: 10.1016/j.envpol.2020.115985.
O'Connor, J., B. S. Mickan, J. Rinklebe, H. Song, K. H. M. Siddique, H. Wang, M. B. Kirkham,
and N. S. Bolan. 2022a. Environmental implications, potential value, and future of food-
waste anaerobic digestate management: A review. Journal of Environmental
Management 318: 115519. doi:https://doi.org/10.1016/j.jenvman.2022.115519.
O'Connor, J., B. S. Mickan, K. H. M. Siddique, J. Rinklebe, M. B. Kirkham, and N. S. Bolan.
2022b. Physical, chemical, and microbial contaminants in food waste management for
soil application: A review. Environmental Pollution 300: 118860.
doi: https://doi. org/10.1016/j.envpol.2022.118860.
Chapter 7. References
7-16
-------
Ogden, S., A. Robb, D. Roberts, G. Palmer, and O. Bell. 2022. Comparing the costs of
alternative waste treatment options. PSE500-022. WRAP.
Oladeji, O., G. Tian, P. Lindo, K. Kumar, A. Cox, L. Hundal, H. Zhang, and E. Podczerwinski.
2020. Nitrogen release and plant available nitrogen of composted and un-composted
biosolids. Water Environment Research 92: 631-640.
doi: https://doi.Org/10.1002/wer. 1260.
Oldfield, T. L., E. White, and N. M. Holden. 2016. An environmental analysis of options for
utilising wasted food and food residue. Journal of Environmental Management 183: 826-
835. doi: 10.1016/j.jenvman.2016.09.035.
Omonode, R. A., T. J. Vyn, D. R. Smith, P. Hegymegi, and A. Gal. 2007. Soil carbon dioxide
and methane fluxes from long-term tillage systems in continuous corn and corn-soybean
rotations. Soil and Tillage Research 95: 182-195. doi: 10.1016/j.still.2006.12.004.
Opatokun, S. A., A. Lopez-Sabiron, G. Ferreira, and V. Strezov. 2017. Life cycle analysis of
energy production from food waste through anaerobic digestion, pyrolysis and integrated
energy system. Sustainability 9. Multidisciplinary Digital Publishing Institute: 1804.
doi:10.3390/su9101804.
Oregon DEQ. 2017. Strategic plan for preventing the wasting of food. Oregon Department of
Environmental Quality (ORDEQ).
Oregon DEQ. 2019. Life cycle assessment of edible food rescue. Oregon Department of
Environmental Quality (ORDEQ).
Owsianiak, M., M. W. Ryberg, M. Renz, M. Hitzl, and M. Z. Hauschild. 2016. Environmental
performance of hydrothermal carbonization of four wet biomass waste streams at
industry-relevant scales. ACS Sustainable Chemistry & Engineering 4: 6783-6791.
doi: 10.1021/acssuschemeng.6b01732.
Owsianiak, M., M. Z. Hauschild, L. Posthuma, E. Saouter, M. G. Vijver, T. Backhaus, M.
Douziech, T. Schlekat, et al. 2022. Ecotoxicity characterization of chemicals: Global
recommendations and implementation in USEtox. Chemosphere: 136807.
doi: 10.1016/j.chemosphere.2022.136807.
Ozores-Hampton, M., J. Biala, G. Evanylo, B. Faucette, L. Cooperband, N. Roe, J. A. Creque,
and D. Sullivan. 2022. Chapter 16 - Compost use. In The Composting Handbook, ed. R.
Rynk, 777-846. Academic Press.
Pace, S. A., R. Yazdani, A. Kendall, C. W. Simmons, and J. S. VanderGheynst. 2018. Impact of
organic waste composition on life cycle energy production, global warming and water
use for treatment by anaerobic digestion followed by composting. Resources,
Conservation and Recycling 137: 126-135. doi:10.1016/j.resconrec.2018.05.030.
Pahla, G., F. Ntuli, and E. Muzenda. 2017. Torrefaction of landfill food waste for possible
application in biomass co-firing. Waste Management 71: 512-520.
doi:10.1016/j.wasman.2017.10.035.
Parchomenko, A., D. Nelen, J. Gillabel, and H. Rechberger. 2019. Measuring the circular
economy—A multiple correspondence analysis of 63 metrics. Journal of Cleaner
Production 210: 200-216. doi:10.1016/j.jclepro.2018.10.357.
Chapter 7. References
7-17
-------
Pardo, G., R. Moral, E. Aguilera, and A. del Prado. 2015. Gaseous emissions from management
of solid waste: A systematic review. Global Change Biology 21: 1313-1327.
doi:10.1111/gcb. 12806.
Paritosh, K., S. K. Kushwaha, M. Yadav, N. Pareek, A. Chawade, and V. Vivekanand. 2017.
Food waste to energy: An overview of sustainable approaches for food waste
management and nutrient recycling. BioMed Research International 2017: 2370927.
doi:10.1155/2017/2370927.
Parnaudeau, V., S. Genermont, C. Henault, A. Farrugia, P. Robert, and B. Nicolardot. 2009.
Measured and Simulated nitrogen fluxes after field application of food-processing and
municipal organic wastes. Journal of Environmental Quality 38: 268-280.
doi: 10.2134/jeq2007.0486.
Parry, D. L. 2014. Co-digestion of organic waste products with wastewater solids: Final report
with economic model. OWSO5R07. Alexandria, Virginia: Water Environment Research
Foundation.
Parry, D. L., and WERF. 2012. Sustainable food waste evaluation. OWSO5R07e. Alexandria,
Virginia: Water Environment Research Foundation.
Paul, S., A. Dutta, F. Defersha, and B. Dubey. 2018. Municipal Food Waste to Biomethane and
Biofertilizer: A Circular Economy Concept. Waste and Biomass Valorization 9: 601-611.
doi: 10.1007/S12649-017-0014-y.
Payen, S., B. Civit, H. Golden, B. Niblick, A. Uwizeye, L. Wnter, and A. D. Henderson. 2019.
Acidification and eutrophication. In Global guidance for life cycle impact assessment
indicators: Volume 2, ed. R. Frischknecht and O. Jolliet, 60-79. Paris, France: United
Nations Environment Program/Society for Environmental Toxicology and Chemistry Life
Cycle Initiative.
Peltre, C., B. T. Christensen, S. Dragon, C. Icard, T. Katterer, and S. Houot. 2012. RothC
simulation of carbon accumulation in soil after repeated application of widely different
organic amendments. Soil Biology and Biochemistry 52: 49-60.
doi:https://doi.org/10.1016/j.soilbio.2012.03.023.
Pena, C., B. Civit, A. Gallego-Schmid, A. Druckman, A. Caldeira-Pires, B. Weidema, E. Mieras,
et al. 2021. Using life cycle assessment to achieve a circular economy. The International
Journal of Life Cycle Assessment, doi: 10.1007/s11367-020-01856-z.
Peng, L., R. Tang, G. Wang, R. Ma, Y. Li, G. Li, and J. Yuan. 2023. Effect of aeration rate,
aeration pattern, and turning frequency on maturity and gaseous emissions during
kitchen waste composting. Environmental Technology & Innovation 29: 102997.
doi: 10.1016/j.eti.2022.102997.
Pergola, M., A. Persiani, A. M. Palese, V. Di Meo, V. Pastore, C. DAdamo, and G. Celano.
2018. Composting: The way for a sustainable agriculture. Applied Soil Ecology 123.
HUMUSICA 3 - Reviews, Applications, Tools: 744-750.
doi:10.1016/j.apsoil.2017.10.016.
Pfister, S., A.-M. Boulay, M. Berger, M. Hadjikakou, M. Motoshita, T. Hess, B. Ridoutt, et al.
2017. Understanding the LCA and ISO water footprint: A response to Hoekstra (2016) "A
critique on the water-scarcity weighted water footprint in LCA." Ecological Indicators 72:
352-359. doi:10.1016/j.ecolind.2016.07.051.
Chapter 7. References
7-18
-------
Pham, T. P. T., R. Kaushik, G. K. Parshetti, R. Mahmood, and R. Balasubramanian. 2015. Food
waste-to-energy conversion technologies: Current status and future directions. Waste
Management 38: 399-408. doi:10.1016/j.wasman.2014.12.004.
Plante, A. F., and R. P. Voroney. 1998. Decomposition of land applied oily food waste and
associated changes in soil aggregate stability. Journal of Environmental Quality 27: 395-
402. doi: 10.2134/jeq1998.00472425002700020021x.
Piatt, B., N. Goldstein, C. Coker, and S. Brown. 2014. State of composting in the US: What, why
where & how. Institute for Local Self-Reliance.
Poeschl, M., S. Ward, and P. Owende. 2012. Environmental impacts ofbiogas deployment -
Part II: life cycle assessment of multiple production and utilization pathways. Journal of
Cleaner Production 24: 184-201. doi: 10.1016/j.jclepro.2011.10.030.
Porterfield, K. K., S. A. Hobson, D. A. Neher, M. T. Niles, and E. D. Roy. 2023. Microplastics in
composts, digestates, and food wastes: A review. Journal of Environmental Quality 52:
225-240. doi: 10.1002/jeq2.20450.
Posch, M., J. Seppala, J.-P. Hettelingh, M. Johansson, M. Margni, and O. Jolliet. 2008. The role
of atmospheric dispersion models and ecosystem sensitivity in the determination of
characterisation factors for acidifying and eutrophying emissions in LCIA. International
Journal of Life Cycle Assessment 13: 477-486. doi: 10.1007/s11367-008-0025-9.
Potting, J., M. P. Hekkert, E. Worrell, and A. Hanemaaijer. 2017. Circular economy: Measuring
innovation in the product chain. PBL Netherlands Environmental Assessment Agency.
Poulton, P., J. Johnston, A. Macdonald, R. White, and D. Powlson. 2018. Major limitations to
achieving "4 per 1000" increases in soil organic carbon stock in temperate regions:
Evidence from long-term experiments at Rothamsted Research, United Kingdom. Global
Change Biology 24: 2563-2584. doi:https://doi.org/10.1111/gcb.14066.
Psomopoulos, C. S. 2009. Waste-to-energy: A review of the status and benefits in USA. Waste
Management 29. Pergamon: 1718-1724. doi: 10.1016/j.wasman.2008.11.020.
Quiros, R., G. Villalba, P. Munoz, J. Colon, X. Font, and X. Gabarrell. 2014. Environmental
assessment of two home composts with high and low gaseous emissions of the
composting process. Resources, Conservation and Recycling 90: 9-20.
doi: 10.1016/j.resconrec.2014.05.008.
Rajagopal, R., A. Ahamed, and J.-Y. Wang. 2014. Hydrolytic and acidogenic fermentation
potential of food waste with source segregated feces-without-urine as co-substrate.
Bioresource technology 167. England: 564-568. doi:10.1016/j.biortech.2014.06.024.
Raptis, C. E., J. M. Boucher, and S. Pfister. 2017. Assessing the environmental impacts of
freshwater thermal pollution from global power generation in LCA. Science of the Total
Environment 580: 1014-1026. doi:10.1016/j.scitotenv.2016.12.056.
Rashid, M. T., and R. P. Voroney. 2004. Land application of oily food waste and corn production
on amended soils. Agronomy Journal 96: 997-1004. doi: 10.2134/agronj2004.0997.
Rashid, M. T., R. P. Voroney, and M. Khalid. 2010. Application of food industry waste to
agricultural soils mitigates green house gas emissions. Bioresource Technology 101:
485—490. doi: 10.1016/j.biortech.2009.06.113.
Chapter 7. References
7-19
-------
Redfield, A. C. 1934. On the proportions of organic derivatives in sea water and their relation to
the composition of plankton. In James Johnstone memorial volume, ed. F. J. Cole, 176-
192. Liverpool, U.K.: University Press of Liverpool.
Redlingshofer, B., S. Barles, and H. Weisz. 2020. Are waste hierarchies effective in reducing
environmental impacts from food waste? A systematic review for OECD countries.
Resources, Conservation and Recycling 156: 104723.
doi: 10.1016/j.resconrec.2020.104723.
ReFED. 2021. Insights Engine Food Waste Monitor.
ReFED. 2022. Federal Animal Feed Policy, http://policyfinder.refed.com. Accessed August 25
2022.
ReFED. 2023. Insights engine solutions database: 2023. https://insights-
engine.refed.org/solution-database. Accessed June 1, 2023.
Rigamonti, L., and E. Mancini. 2021. Life cycle assessment and circularity indicators.
International Journal of Life Cycle Assessment 26: 1937-1942. doi:10.1007/s11367-021-
01966-2.
Rigby, H., and S. R. Smith. 2013. Nitrogen availability and indirect measurements of
greenhouse gas emissions from aerobic and anaerobic biowaste digestates applied to
agricultural soils. Waste Management 33: 2641-2652.
doi: 10.1016/j.wasman.2013.08.005.
Righi, S., L. Oliviero, M. Pedrini, A. Buscaroli, and C. Delia Casa. 2013. Life cycle assessment
of management systems for sewage sludge and food waste: Centralized and
decentralized approaches. Journal of Cleaner Production 44: 8-17.
doi:10.1016/j.jclepro.2012.12.004.
Rinot, O., G. J. Levy, Y. Steinberger, T. Svoray, and G. Eshel. 2019. Soil health assessment: A
critical review of current methodologies and a proposed new approach. Science of the
Total Environment 648: 1484-1491. doi:10.1016/j.scitotenv.2018.08.259.
Risse, M., and B. Faucette. 2017. Food waste composting: Institutional and industrial
applications. University of Georgia Extension. Bulletin 1189.
Ryals, R., M. Kaiser, M. S. Torn, A. A. Berhe, and W. L. Silver. 2014. Impacts of organic matter
amendments on carbon and nitrogen dynamics in grassland soils. Soil Biology and
Biochemistry 68. Elsevier: 52-61.
Rynk, R., L. Cooperband, C. Oshins, H. Wescott, J. Bonhotal, M. Schwarz, R. Sherman, and S.
Brown. 2022. Chapter 1 - Why compost? In The Composting Handbook, ed. R. Rynk, 1-
26. Academic Press. doi:10.1016/B978-0-323-85602-7.00001-7.
Salemdeeb, R., E. K. H. J. Zu Ermgassen, M. H. Kim, A. Balmford, and A. Al-Tabbaa. 2017.
Environmental and health impacts of using food waste as animal feed: A comparative
analysis of food waste management options. Journal of Cleaner Production 140: 871-
880. doi: 10.1016/j.jclepro.2016.05.049.
San Miguel, C., D. Gimenez, U. Krogmann, and S. W. Yoon. 2012. Impact of land application of
cranberry processing residuals, leaves and biosolids pellets on a sandy loam soil.
Applied Soil Ecology 53: 31-38. doi: 10.1016/j.apsoil.2011.11.001.
Chapter 7. References
7-20
-------
Scheehle, E. A., and M. R. J. Doom. 2002. Improvements to the U.S. wastewater methane and
nitrous oxide emissions estimates. U.S. Environmental Protection Agency, Office of Air
and Radiation.
Scherhaufer, S., S. Lebersorger, A. Pertl, G. Obersteiner, F. Schneider, L. Falasconi, F. D.
Menna, et al. 2015. Criteria for and baseline assessment of environmental and socio-
economic impacts of food waste: Final report. BOKU University of Natural Resources
and Life Sciences, Institute of Waste Management.
Schneider, F. 2013. The evolution of food donation with respect to waste prevention. In Urban
mining, special issue, Waste Management 33: 755-763.
doi:10.1016/j.wasman.2012.10.025.
Schreefel, L., R. P. O. Schulte, I. J. M. de Boer, A. P. Schrijver, and H. H. E. van Zanten. 2020.
Regenerative agriculture - the soil is the base. Global Food Security 26: 100404.
doi: 10.1016/j.gfs.2020.100404.
Seo, Y.-C., M. T. Alam, and W.-S. Yang. 2018. Gasification of municipal solid waste. In
Gasification for low-grade feedstock. 10.5772/intechopen.73685.
Seppala, J., M. Posch, M. Johansson, and J.-P. Hettelingh. 2006. Country-dependent
characterisation factors for acidification and terrestrial eutrophication based on
accumulated exceedance as an impact category indicator. International Journal of Life
Cycle Assessment 11: 403-416. doi:10.1065/lca2005.06.215.
Sevigne-ltoiz, E., O. Mwabonje, C. Panoutsou, and J. Woods. 2021. Life cycle assessment
(LCA): informing the development of a sustainable circular bioeconomy? Philosophical
Transactions of The Royal Society A-Mathematical Physical and Engineering Sciences
379. doi: 10.1098/rsta.2020.0352.
Sherwood, J. 2020. The significance of biomass in a circular economy. Bioresource Technology
300. England: 122755. doi:10.1016/j.biortech.2020.122755.
Shih, M.-F., C.-Y. Lin, and C.-H. Lay. 2021. Comparison of Potential Environmental Impacts and
Waste-to-Energy Efficiency for Kitchen Waste Treatment Scenarios in Central Taiwan.
Processes 9. Multidisciplinary Digital Publishing Institute: 696. doi:10.3390/pr9040696.
Shurson, G. C. 2020. "What a Waste"—Can We Improve Sustainability of Food Animal
Production Systems by Recycling Food Waste Streams into Animal Feed in an Era of
Health, Climate, and Economic Crises? Sustainability 12. Multidisciplinary Digital
Publishing Institute: 7071. doi:10.3390/su12177071.
Silver, W. L., S. E. Vergara, and A. Mayer. 2018. Carbon sequestration and greenhouse gas
mitigation potential of composting and soil amendments on California's rangelands.
CCC4A-CNRA-2018-002. California Natural Resources Agency.
Slorach, P. C., H. K. Jeswani, R. Cuellar-Franca, and A. Azapagic. 2019a. Environmental and
economic implications of recovering resources from food waste in a circular economy.
Science of the Total Environment 693: 133516. doi: 10.1016/j.scitotenv.2019.07.322.
Slorach, P. C., H. K. Jeswani, R. Cuellar-Franca, and A. Azapagic. 2019b. Environmental
sustainability of anaerobic digestion of household food waste. Journal of Environmental
Management 236: 798-814. doi:10.1016/j.jenvman.2019.02.001.
Chapter 7. References
7-21
-------
Slorach, P. C., H. K. Jeswani, R. Cuellar-Franca, and A. Azapagic. 2020. Assessing the
economic and environmental sustainability of household food waste management in the
UK: Current situation and future scenarios. Science of the Total Environment 710:
135580. doi: 10.1016/j.scitotenv.2019.135580.
Smith, J. H. 1986. Decomposition of potato processing wastes in soil. Journal of Environmental
Quality 15: 13-16. doi:10.2134/jeq1986.00472425001500010004x.
Sogn, T. A., I. Dragicevic, R. Linjordet, T. Krogstad, V. G. H. Eijsink, and S. Eich-Greatorex.
2018. Recycling of biogas digestates in plant production: NPK fertilizer value and risk of
leaching. International Journal of Recycling of Organic Waste in Agriculture 7: 49-58.
doi: 10.1007/S40093-017-0188-0.
Song, C., J.-J. Zhu, J. L. Willis, D. P. Moore, M. A. Zondlo, and Z. J. Ren. 2023. Methane
emissions from municipal wastewater collection and treatment systems. Environmental
Science & Technology 57: 2248-2261. doi:10.1021/acs.est.2c04388.
Song, Q., Z. Wang, and J. Li. 2013. Environmental performance of municipal solid waste
strategies based on LCA method: a case study of Macau. Journal of Cleaner Production
57: 92-100. doi:https://doi.org/10.1016/j.jclepro.2013.04.042.
State of California. 2016a. Compostable Materials Handling Operations and Facilities
Regulatory Requirements. California Code of Regulations. Vol. 14 CCR § 17868.3.1.
State of California. 2016b. Compostable Materials Handling Operations and Facilities
Regulatory Requirements. California Code of Regulations. Vol. 14 CCR § 17868.2.
State of Washington. 2019. Washington Administrative Code 173-350-220.
Steffen, W., K. Richardson, and J. Rockstrom. 2015. Planetary boundaries: Guiding human
development on a changing planet. Science 347: 1259855.
doi: 10.1126/science. 1259855.
Stehouwer, R., L. Cooperband, R. Rynk, J. Biala, J. Bonhotal, S. Antler, T. Lewandowski, and
H. Nichols. 2022. Chapter 15 - Compost characteristics and quality. In The Composting
Handbook, ed. R. Rynk, 737-775. Academic Press.
Sullivan, D. M., A. I. Bary, C. G. Cogger, I. J. Madsen, and L. J. Brewer. 2021. Biosolids in
Dryland Cropping Systems. PNW716. Pacific Northwest Extension: Oregon State
University, University of Idaho, Washington State University.
Sulis, F., F. Agostinho, C. M. V. B. Almeida, and B. F. Giannetti. 2021. Recognizing the wealth
of non-marketable food in distribution centres: The environmental benefits of donation.
Journal of Cleaner Production 318: 128482. doi: 10.1016/j .jclepro.2021.128482.
Sundin, N., C. Persson Osowski, I. Strid, and M. Eriksson. 2022. Surplus food donation:
Effectiveness, carbon footprint, and rebound effect. Resources, Conservation and
Recycling 181: 106271. doi:10.1016/j.resconrec.2022.106271.
Tambone, F., B. Scaglia, G. D'lmporzano, A. Schievano, V. Orzi, S. Salati, and F. Adani. 2010.
Assessing amendment and fertilizing properties of digestates from anaerobic digestion
through a comparative study with digested sludge and compost. Chemosphere 81: 577-
583. doi: 10.1016/j.chemosphere.2010.08.034.
Chapter 7. References
7-22
-------
Tanveer, U., S. Ishaq, and A. Gough. 2021. Circular economy in agri-food sector: food waste
management perspective. In Challenges and Opportunities of Circular Economy in Agri-
Food Sector, ed. D. R. S. D. A. P. Mor. Springer.
Thakali, A., and J. D. MacRae. 2021. A review of chemical and microbial contamination in food:
What are the threats to a circular food system? Environmental Research 194: 110635.
doi: 10.1016/j.envres.2020.110635.
Thakali, A., J. D. MacRae, C. Isenhour, and T. Blackmer. 2022. Composition and contamination
of source separated food waste from different sources and regulatory environments.
Journal of Environmental Management 314: 115043.
doi: 10.1016/j.jenvman.2022.115043.
Thangarajan, R., N. S. Bolan, G. Tian, R. Naidu, and A. Kunhikrishnan. 2013. Role of organic
amendment application on greenhouse gas emission from soil. Science of The Total
Environment 465. Soil as a Source & Sink for Greenhouse Gases: 72-96.
doi:10.1016/j.scitotenv.2013.01.031.
Thyagarajan, T., M. Puri, J. Vongsvivut, and C. J. Barrow. 2014. Evaluation of bread crumbs as
a potential carbon source for the growth of thraustochytrid species for oil and omega-3
production. NutrientsQ\ 2104-2114. doi:10.3390/nu6052104.
Tian, H., X. Wang, E. Y. Lim, J. T. E. Lee, A. W. L. Ee, J. Zhang, and Y. W. Tong. 2021. Life
cycle assessment of food waste to energy and resources: Centralized and decentralized
anaerobic digestion with different downstream biogas utilization. Renewable and
Sustainable Energy Reviews 150: 111489. doi:10.1016/j.rser.2021.111489.
de Titto, E., and A. Savino. 2019. Environmental and health risks related to waste incineration.
Waste Management & Research 37 (10): 1-11. doi: 10.1177/0734242X19859700 Article
information.
Tiwary, A., I. D. Wlliams, D. C. Pant, and V. V. N. Kishore. 2015. Emerging perspectives on
environmental burden minimisation initiatives from anaerobic digestion technologies for
community scale biomass valorisation. Renewable and Sustainable Energy Reviews 42:
883-901. doi:10.1016/j.rser.2014.10.052.
Tong, H., Y. Shen, J. Zhang, C.-H. Wang, T. S. Ge, and Y. W. Tong. 2018. A comparative life
cycle assessment on four waste-to-energy scenarios for food waste generated in
eateries. Applied Energy 225: 1143-1157. a9h. doi:10.1016/j.apenergy.2018.05.062.
Trabold, T., and C. W. Babbitt, eds. 2018. Sustainable food waste-to-energy systems. Elsevier.
Tufvesson, L. M., M. Lantz, and P. Borjesson. 2013. Environmental performance of biogas
produced from industrial residues including competition with animal feed—Life-cycle
calculations according to different methodologies and standards. Journal of Cleaner
Production 53: 214-223. doi:10.1016/j.jclepro.2013.04.005.
Turmel, M.-S., A. Speratti, F. Baudron, N. Verhulst, and B. Govaerts. 2015. Crop residue
management and soil health: A systems analysis. Agricultural Systems 134: 6-16.
doi:https://doi.org/10.1016/j.agsy.2014.05.009.
UN General Assembly. 2015. Transforming Our World: The 2030 Agenda for Sustainable
Development. Vol. A/Res/70/1.
Chapter 7. References
7-23
-------
UNEP. 2019. Circularity framework. United Nations Environment Program.
UNH Extension. 2017. Manual of best management practices for land application ofbiosolids.
University of New Hampshire Cooperative Extension.
Urra, J., I. Alkorta, and C. Carbisu. 2019. Potential benefits and risks for soil health derived from
the use of organic amendments in agriculture. Agronomy 9: 542.
doi: 10.3390/agronomy9090542.
U.S. Composting Council. 2021. USCC Compost Manufacturer's Environmental Impact
Analysis. Newsroom. July 12.
U.S. Congress. 2020. Save Our Seas 2.0 Act. Public Law 116-224.
U.S. EPA. 2016. Clean watersheds needs survey 2012: Report to Congress. EPA-830-R-15005.
United States Environmental Protection Agency.
U.S. EPA. 2020a. 2018 wasted food report. EPA 530-R-20-004. United States Environmental
Protection Agency., https://www.epa.gov/sites/production/files/2020-
11/documents/2018_wasted_food_report.pdf. Accessed July 1 2021.
U.S. EPA. 2020b. Documentation for greenhouse gas emission and energy factors used in the
waste reduction model (WARM): Management practices chapters. WARM Version 15.
Washington, DC, USA: United States Environmental Protection Agency, Office of
Resource Conservation and Recovery, https://www.epa.gov/warm/documentation-
chapters-greenhouse-gas-emission-energy-and-economic-factors-used-waste-reduction.
U.S. EPA. 2020c. Documentation for greenhouse gas emission and energy factors used in the
waste reduction model (WARM): Organic materials chapters. WARM Version 15.
Washington, DC, USA: United States Environmental Protection Agency, Office of
Resource Conservation and Recovery, https://www.epa.gov/warm/documentation-
chapters-greenhouse-gas-emission-energy-and-economic-factors-used-waste-reduction.
U.S. EPA. 2020d. Food loss and waste 2030 champions. United States Environmental
Protection Agency, https://www.epa.gov/sustainable-management-food/united-states-
food-loss-and-waste-2030-champions. Accessed 4/1/2022.
U.S. EPA. 2021a. Anaerobic digestion facilities processing food waste in the United States
(2017 & 2018). EPA/903/S-21/001. United States Environmental Protection Agency..
U.S. EPA. 2021b. Commercial pre-processing technologies. Emerging Issues in Food Waste
Management. United States Environmental Protection Agency.
U.S. EPA. 2021c. From farm to kitchen: The environmental impacts of U.S. food waste. EPA
600-R21 171. U.S. Environmental Protection Agency.
U.S. EPA. 2021 d. LFG Energy Project Development Handbook'. Washington, DC, USA: United
States Environmental Protection Agency.
U.S. EPA. 2021 e. Persistent chemical contaminants. Emerging Issues in Food Waste
Management. Washington, DC, USA: United States Environmental Protection Agency.
U.S. EPA. 2021f. Plastic contamination. Emerging Issues in Food Waste Management.
Washington, DC, USA: United States Environmental Protection Agency.
Chapter 7. References
7-24
-------
U.S. EPA. 2021 g. Sustainable management of food: Food recovery hierarchy. United States
Environmental Protection Agency, https://www.epa.gov/sustainable-management-
food/food-recovery-hierarchy
U.S. EPA. 2021 h. Types of Composting and Understanding the Process. United States
Environmental Protection Agency.https://www.epa.gov/sustainable-management-
food/types-composting-and-understanding-process. Accessed August 3, 2022.
U.S. EPA. 2022a. Landfill Methane Outreach Program Landfill and Project Database (version
March 2022). United States Environmental Protection Agency.
https://www.epa.gov/lmop/lmop-landfill-and-project-database.
U.S. EPA. 2022b. National overview: Facts and figures on materials, wastes and recycling.
United States Environmental Protection Agency, https://www.epa.gov/facts-and-figures-
about-materials-waste-and-recycling/national-overview-facts-and-figures-materials.
Accessed August 23, 2022.
U.S. EPA. 2022c. U.S. National Recycling Goal. United States Environmental Protection
Agency, https://www.epa.gov/recyclingstrategy/us-national-recycling-goal. Accessed
November 29, 2022.
U.S. EPA. 2023a. 2019 Wasted Food Report: Estimates of Generation and Management of
Wasted Food in the United States in 2019. United States Environmental Protection
Agency.
U.S. EPA. 2023b. Anaerobic digestion facilities processing food waste in the United States
(2019). EPA 530-R-23-003. United States Environmental Protection Agency.
U.S. EPA. 2022c. Energy recovery from the combustion of municipal solid waste (MSW). United
States Environmental Protection Agency, https://www.epa.gov/smm/energy-recovery-
combustion-municipal-solid-waste-msw. Accessed February 13, 2023.
U.S. EPA. 2023d. Excess Food Opportunities Map. United States Environmental Protection
Agency, https://www.epa.gov/sustainable-management-food/excess-food-opportunities-
map. Accessed February 3, 2023.
U.S. FDA. 2022. Bovine Spongiform Encephalopathy. United States Food and Drug
Administration, https://www.fda.gov/animal-veterinary/compliance-enforcement/bovine-
spongiform-encephalopathy. Accessed April 18, 2023.
Usack, J. G., L. Gerber Van Doren, R. Posmanik, R. A. Labatut, J. W. Tester, and L. T.
Angenent. 2018. An evaluation of anaerobic co-digestion implementation on New York
State dairy farms using an environmental and economic life-cycle framework. Applied
Energy 211: 28-40. doi:10.1016/j.apenergy.2017.11.032.
USDA. 2020. Swine: Other Programs. USDA Animal and Plant Health Inspection Service.
United States Department of Agriculture.
https://www.aphis.usda.gov/aphis/ourfocus/animalhealth/animal-disease-
information/swine-disease-information/other-programs. Accessed April 17, 2023.
USDA. 2021. Soil health. United States Department of Agriculture.
https://www.nrcs.usda.gov/wps/portal/nrcs/main/soils/health/. Accessed April 17, 2023.
Chapter 7. References
7-25
-------
Van Ewijk, S., and J. A. Stegemann. 2016. Limitations of the waste hierarchy for achieving
absolute reductions in material throughput. Journal of Cleaner Production 132: 122-128.
doi:https://doi. org/10.1016/j.jclepro.2014.11.051.
Vandermeersch, T., R. A. F. Alvarenga, P. Ragaert, and J. Dewulf. 2014. Environmental
sustainability assessment of food waste valorization options. Resources, Conservation
and Recycling 87: 57-64. doi:10.1016/j.resconrec.2014.03.008.
Vivaldi, G. A., D. Zaccaria, S. Camposeo, F. Pasanisi, F. P. Salcedo, and I. Portoghese. 2022.
Appraising water and nutrient recovery for perennial crops irrigated with reclaimed water
in Mediterranean areas through an index-based approach. Science of The Total
Environment 820: 152890. doi:https://doi.org/10.1016/j.scitotenv.2021.152890.
Wallace, T., D. Gibbons, M. O'Dwyer, and T. P. Curran. 2017. International evolution of fat, oil
and grease (FOG) waste management—A review. Journal of Environmental
Management 187: 424-435. doi:10.1016/j.jenvman.2016.11.003.
Wang, S., and Y. Zeng. 2018. Ammonia emission mitigation in food waste composting: A
review. Bioresource Technology (England) 248: 13-19.
doi: 10.1016/j.biortech.2017.07.050.
Wang, X., A. S. Nagpure, J. F. DeCarolis, and M. A. Barlaz. 2013. Using observed data to
improve estimated methane collection from select U.S. landfills. Environmental Science
& Technology 47: 3251-3257. doi:10.1021/es304565m.
Wang, X., Z. Bai, Y. Yao, B. Gao, D. Chadwick, Q. Chen, C. Hu, and L. Ma. 2018. Composting
with negative pressure aeration for the mitigation of ammonia emissions and global
warming potential. Journal of Cleaner Production 195: 448-457.
doi: 10.1016/j.jclepro.2018.05.146.
Wang, Y., Z. Yuan, and Y. Tang. 2021. Enhancing food security and environmental
sustainability: A critical review of food loss and waste management. Resources,
Environment and Sustainability 4: 100023. doi:10.1016/j.resenv.2021.100023.
Wang, Z., Y. Hu, S. Wang, G. Wu, and X. Zhan. 2023. A critical review on dry anaerobic
digestion of organic waste: Characteristics, operational conditions, and improvement
strategies. Renewable and Sustainable Energy Reviews 176: 113208.
doi: 10.1016/j. rser.2023.113208.
WEF. 2023. Circular Economy: Transformation Map. World Economic Forum.
van der Wei, B. Z., J. Weijma, C. E. van Middelaar, M. Kleinke, C. J. N. Buisman, and F.
Wichern. 2021. Restoring nutrient circularity in a nutrient-saturated area in Germany
requires systemic change. Nutrient Cycling in Agroecosystems 121: 209-226.
doi: 10.1007/s10705-021-10172-3.
Wilkinson, A. D., and D. L. Meeker. 2021. How agricultural rendering supports sustainability and
assists livestock's ability to contribute more than just food. Animal Frontiers 11: 24-34.
doi: 10.1093/af/vfab002.
Winans, K., E. Marvinney, A. Gillman, and E. Spang. 2020. An evaluation of on-farm food loss
accounting in life-cycle assessment (LCA) of four California specialty crops. Frontiers in
Sustainable Food Systems 4. doi: 10.3389/fsufs.2020.00010.
Chapter 7. References
7-26
-------
Witzgall, K., A. Vidal, D. I. Schubert, C. Hoschen, S. A. Schweizer, F. Buegger, V. Pouteau, C.
Chenu, et al. 2021. Particulate organic matter as a functional soil component for
persistent soil organic carbon. Nature Communications 12: 4115. doi: 10.1038/s41467-
021-24192-8.
Wolf, M.-A., R. Pant, K. Chomkhamsri, S. Sala, and D. Pennington. 2012. The International
Reference Life Cycle Data System (ILCD) handbook: Towards more sustainable
production and consumption for a resource-efficient Europe. EUR 24982 EN. Ispra, Italy:
Joint Research Centre, Institute for Environment and Sustainability.
Woon, K. S., I. M. C. Lo, S. L. H. Chiu, and D. Y. S. Yan. 2016. Environmental assessment of
food waste valorization in producing biogas for various types of energy use based on
LCA approach. Waste Management 50: 290-299. doi:10.1016/j.wasman.2016.02.022.
World Health Organization. 2007. Population health and waste management: scientific data and
policy options. Rome, Italy.
https://www.euro.who.int/ data/assets/pdf_file/0012/91101/E91021.pdf.
WRAP. 2015. Strategies to achieve economic and environmental gains by reducing food waste.
Banbury, England: Waste and Resources Action Programme.
WRAP. 2016. Field experiments for quality digestate and compost in agriculture. Waste and
Resources Action Programme.
Wuest, S. B., and H. T. Gollany. 2013. Soil Organic Carbon and Nitrogen After Application of
Nine Organic Amendments. Soil Science Society of America Journal 77: 237-245.
doi:https://doi.org/10.2136/sssaj2012.0184.
Xiong, X., I. K. M. Yu, D. C. W. Tsang, N. S. Bolan, Y. SikOk, A. D. Igalavithana, M. B.
Kirkham, K.-H. Kim, and K. Vikrant. 2019. Value-added chemicals from food supply
chain wastes: State-of-the-art review and future prospects. Chemical Engineering
Journal 375: 121983. doi:10.1016/j.cej.2019.121983.
Xu, C., W. Shi, J. Hong, F. Zhang, and W. Chen. 2015. Life cycle assessment of food waste-
based biogas generation. Renewable and Sustainable Energy Reviews 49: 169-177.
doi:10.1016/j.rser.2015.04.164.
Yan, M., H. Tian, S. Song, H. T. W. Tan, J. T. E. Lee, J. Zhang, P. Sharma, Y. W. Tiong, et al.
2023. Effects of digestate-encapsulated biochar on plant growth, soil microbiome and
nitrogen leaching. Journal of Environmental Management 334: 117481.
doi: https://doi. org/10.1016/j.jenvman.2023.117481.
Yang, F., G. X. Li, Q. Y. Yang, and W. H. Luo. 2013. Effect of bulking agents on maturity and
gaseous emissions during kitchen waste composting. Chemosphere 93: 1393-1399.
doi: 10.1016/j.chemosphere.2013.07.002.
Yoshida, H., J. J. Gable, and J. K. Park. 2012. Evaluation of organic waste diversion
alternatives for greenhouse gas reduction. Resources, Conservation and Recycling 60:
1-9. doi: 10.1016/j.resconrec.2011.11.011.
Zan, F., J. Dai, F. Jiang, G. A. Ekama, and G. Chen. 2020. Ground food waste discharge to
sewer enhances methane gas emission: A lab-scale investigation. Water Research
(England) 174: 115616. doi:10.1016/j.watres.2020.115616.
Chapter 7. References
7-27
-------
van Zelm, R., P.-O. Roy, M. Z. Hauschild, and M. A. J. Huijbregts. 2015. Acidification. In Life
cycle impact assessment, ed. M. Z. Hauschild and M. A. J. Huijbregts, 163-176. LCA
Compendium—The Complete World of Life Cycle Assessment. Netherlands: Springer
Science & Business Media.
Zhang, Z., W. Han, X. Chen, N. Yang, C. Lu, and Y. Wang. 2019. The life-cycle environmental
impact of recycling of restaurant food waste in lanzhou, China. Applied Sciences 9:
3608. doi:10.3390/app9173608.
Zhao, Y., Y. Lou, W. Qin, J. Cai, P. Zhang, and B. Hu. 2022. Interval aeration improves
degradation and humification by enhancing microbial interactions in the composting
process. Bioresource Technology 358: 127296. doi:10.1016/j.biortech.2022.127296.
Zhou, Y., Y. Hu, A. J. Y. Chen, Z. Cheng, Z. Bi, R. Zhang, and Z. Lou. 2022. Environmental
impacts and nutrient distribution routes for food waste separated disposal on large-scale
anaerobic digestion/ composting plants. Journal of Environmental Management 318:
115624. doi: 10.1016/j.jenvman.2022.115624.
Chapter 7. References
7-28
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APPENDIX F
ENDNOTES
1 World Resources Institute (WRI), Consumer Goods Forum (CGF), Food and Agriculture Organization of
the United Nations (FAO), United Nations Environment Programme (UNEP), Waste and Resources
Action Programme (WRAP), World Business Council for Sustainable Development (WBCSD).
2 The term 'water resource recovery facility', WRRF, is used in this report to refer to wastewater treatment
plants that co-digest wasted food. The term 'wastewater treatment plant' is used more generally to refer
to wastewater treatment facilities that might not recover resources or in cases where it is unclear. For
example, within the sewer/WWT pathway not all facilities receiving wasted food will have anaerobic
digestion, so the more general term is preferred. Other forms of energy or resource recovery can occur at
WRRFs, that may qualify them as WRRFs, but these practices are outside the scope of this document.
3 Damiani (2021) places the impact of beef production at more than 28 kg C02e/kg, on average, whereas
rice production results in one-tenth the GWP impacts of beef (2.7 kg C02e/kg).
4 Eriksson and Spangberg (2017)considered the conversion of nonmarketable fruits and vegetables into
chutney. They looked at five different fruits and vegetables (apples, bananas, oranges, peppers, and
tomatoes) and evaluated only GWP (kg C02e/kg wasted food) and energy demand (MJ/kg wasted food).
The analysis considered avoided production of fresh fruits and vegetables. Production intensities varied
from 0.4 kg C02e and 5 MJ for an apple to 1 kg C02e and 15 MJ for a pepper, and thus the net impact
was between -0.4 and -1 kg C02e and between -5 and -15 MJ for the upcycling of the apple and pepper.
Additionally, several processes were essentially cancelled by their opposites: processing and avoided
processing, glass jar production and avoided glass jar production, transportation to supermarket and
avoided transportation to supermarket.
5 Eriksson et al. (2021) investigated changing broccoli harvesting practices to collect leaves and broccoli
heads that fall outside the quality norms and are typically left behind. The leaves were considered for use
in bread (displacing wheat flour) and broccoli soup (displacing imported broccoli powder), while the heads
were considered for sliced broccoli. For all three scenarios, additional harvesting steps were negligible.
Transportation was similar to that required for regular broccoli. The displacement of other products was a
major contributor to overall impacts. In the case of bread, the displacement of wheat flour did not offset
drying, so the net impact was 0.075 kg C02e/kg broccoli. However, the soup and sliced broccoli
displaced products with higher impacts, leading to net negative impact (-0.45 to -0.35 kg C02eq/kg
broccoli).
6 For example, cows are often raised for milk and meat, but the leather produced from their hides is not
treated as impact-free. In the case of upcycling, broccoli is generally cultivated for its florets, and the
leaves are wasted food. As wasted food, broccoli leaf production is impact-free. However, if broccoli
leaves were to become a regular substitute for wheat flour, they might cease to be classified as upcycled,
and then they would no longer be considered impact-free. A study of broccoli leaves found that the leaves
had higher environmental production impacts than wheat flour (Eriksson et al. 2021).
7 Co-digestion of signficant quantities of wasted food with sludge from wastewater treatment operations
may materially affect the composition and associated benefits and impacts of biosolids processing and
use. The Biosolids Emissions Assessment Model (BEAM), was developed by the Canadian Council of
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Ministers of the Environment, to estimate GHG emissions associated with biosolids management.
Applicability of this model to biosolids generated from a co-digestion process is unknown.
8 About 1,265 of the roughly 16,000 WRRFs in the United States process biosolids with AD, and roughly
10% of those facilities co-digest source-separated wasted food with biosolids (ASCE 2021; U.S. EPA
2023b). Co-digestion of food waste along with wastewater solids has been shown to increase biogas
production, with fats, oils, and grease providing some of the greatest biogas benefits (Parry 2014).
9 A U.S. EPA report of case studies of WRRFs adding wasted food (FOG, residential, commercial, and
industrial) as co-digestate showed increases in biogas production ranging from 40% to 300% (U.S. EPA
2014b).
10 The ratio of produced energy to input energy (termed the energy ratio) is sometimes used to quantify
net energy production. Research cited by Khoshnevisan et al. (2018) reports that biogas plants typically
have an energy ratio of between 2 and 6. In their own analysis, energy ratios varied from 3.1 to 5.2.
11 A review of sustainable approaches to wasted food management summarizes nine studies that provide
evidence of improved methane yields, enhanced process stability, or increased volatile solids reduction
when wasted food is co-digested with green waste, biosolids, animal manure, and other organic materials
(Paritosh et al. 2017).
12 Many reviewed studies specify either single- or two-stage digestion processes, but do not go into detail
on why a specific reactor type was chosen. Ahamed et al. (2016) state clearly that "conventional single-
stage reactors are not suitable for food waste," and the study relies instead on a two-stage technology
that is expected to increase process stability and yield more methane. Ahamed's analysis looks at
digestion of pure wasted food, while many other studies co-digest wasted food with other organic
materials. Tiwary et al. (2015) go into greater detail, describing that methanogenic organisms struggle to
deal with the rapid drop in pH that accompanies hydrolysis when highly degradable materials such as
wasted food are introduced directly into single-stage reactors. Separation of these reactions within multi-
stage reactors can increase biological stability and process performance. Alternatively, co-digestion of
highly degradable materials with more stable organic materials can circumvent this issue but limits the
quantity of wasted food that can be processed in each facility.
13 Instances in which it may not be appropriate to assign an avoided burden credit for the full quantity of
energy produced include, for example, situations where there is no market for produced heat or where
biogas has historically been used to provide heat for AD (i.e., baseline is not natural gas combustion).
14 Al-Rumaihi et al. (2020) showed that GWP results are sensitive to changes in CHP output, with a 30%
increase in heat and electricity production leading to a greater than 100% decrease in impact potential
(i.e., a net benefit).
15 A few studies examine disposal of digestate by incineration (Chiu and Lo 2018; Tong et al. 2018) or in
a landfill (Righi et al. 2013).
16 One study states that 30% to 50% of total nitrogen can be lost as ammonia within six hours of
application, though incorporation into soil may reduce losses by 85%. Nitrate leaching is also of concern,
with losses of up to 15% of applied nitrogen from autumn applications (Nicholson et al. 2017).
17 Slorach et al. (2019a) report that there is not a significant difference in the production of biogas
between mesophilic and thermophilic reactors, but that thermophilic reactors can have twice the energy
consumption. Tiwary et al. (2015) come to a different conclusion, finding that thermophilic reactors do
have greater biogas production.
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18 A consequential analysis of animal feed, composting, and AD found that the lower eutrophication,
toxicity, and acidification impacts of wet and dry feed are largely due to avoiding conventional animal feed
production (Salemdeeb et al. 2017).
19 Albizzati et al. (2021 b)consider avoided reference products for their wet and protein-concentrated
animal feed pathways, which are maize grain and soybean-based, respectively. When compared to the
gross impact of animal feed production and alternative management pathways, the reference product
avoids considerable environmental burdens for several impact categories including human toxicity,
cancer, particulate matter formation, global warming, ionizing radiation, photochemical ozone formation,
eutrophication, and freshwater ecotoxicity.
20 Thakali et al. (2022) studied the effect of source and regulatory requirements on the type and amount
of contamination in food wastes intended for composting. Source separated food wastes generated from
locations that were required by regulation to separate food waste from packaging and other non-food
contaminants had lower levels of physical contamination than food wastes from locations that voluntarily
separated. Chemical contaminates across both regulated and unregulated sources include zinc, copper,
halogenated organics, and PFAS.
21 A review of methane emissions found that typically between 1% and 4% of carbon entering a compost
pile is released as methane (Ermolaev et al. 2014). A separate review of laboratory and field studies
found that 2.7% of carbon is released as methane (Pardo et al. 2015). A review by Cerda et al. (2018)
identified that between 0.03 and 71.4 kg methane are released perton wasted food during composting.
Accurate measurement of compost gaseous emissions can be difficult, given emission gradients at
different locations in the pile (Buyuksonmez 2012).
22 Levis and Barlaz (2011) performed a sensitivity analysis that looked at the fraction of carbon in
compost feedstock that was liberated during biodegradation. The analysis considered loss of between
40% and 83% of initial carbon, with strong linear increases in GWP across all considered composting
technologies as the fraction of carbon loss increased. Increasing carbon loss during composting
increases process methane emissions while decreasing long-term carbon storage.
23 An analysis of high and low emission scenarios for home composting systems (Quiros et al. 2014)
illustrates the variable impacts of compost process emissions. In the high emission scenario, process
emissions dominate all other operational impacts (energy, tools, and collection) for the acidification,
eutrophication, and GWP categories. Energy-related inventory categories and ozone depletion are not
influenced by compost process emissions. In the low emissions scenarios, process emissions still
dominate for GWP, but the magnitude of impact is reduced. The contribution of process emissions to
acidification and eutrophication is reduced dramatically in the low emission scenario and is similar in
magnitude to impacts associated with infrastructure and energy consumption.
24 The interplay of the various bacterial communities that compost organic waste is complex, and thus it
can be straightforward to optimize for a single emission but difficult to optimize across emissions. For
example, a review of strategies to minimize NH3 emissions identified several approaches: 1) adjusting
pH, 2) adjusting C:N ratios (e.g., through initial adjustment or co-composting a green waste that has a
high C:N ratio), 3) adding absorbents (e.g., zeolite or biochar), 4) struvite precipitation (with additional
adjustment of salinity), 5) adjusting nitrification, or 6) adjusting aeration rates and pressures (Wang et al.
2018; Wang and Zeng 2018).
25 The studies that explicitly state their assumptions related to carbon sequestration assume that between
10% and 15% of land-applied carbon is sequestered (Levis and Barlaz 2011; Yoshida et al. 2012).
Whether or not the carbon in compost is assumed to be sequestered has a strong impact on results,
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potentially shifting net GWP emissions from positive to negative (Levis and Barlaz 2011; Silver et al.
2018).
26 Wasted food is a good source of nitrogen and phosphorus in composting systems, can help establish
ideal C/N, ratios in compost systems and leads to finished compost products with benefits both as a soil
conditioner and as a replacement for chemical fertilizers.
27 Energy use has been found to be a major contributor of gross emissions of nitrogen oxides and sulfur
oxides in ASP and bioreactor compost systems (Levis and Barlaz 2011). The analysis shows
considerably less gross impact associated with windrow composting energy demand, which is dominated
by windrow turning.
28 Carbon dioxide, ammonia, methane, nitrous oxide, and VOCs constitute 99% of total emissions; further
detail is provided in Quiros et al. (2014).
29 Increasing aeration through pile turning and bulking agents decreased emissions of both methane and
nitrogen dioxide, according to a review of management approaches (Pardo et al. 2015) and laboratory-
scale experiments (Yang et al. 2013). Experiments by the California Natural Resources Agency also
confirm the importance of maintaining aeration to limit methanogenesis (Silver et al. 2018). A study of
GHG emissions from home-scale composting systems came to an alternate conclusion: that fewer mixing
events led to reduced methane emissions, while increased temperature led to increased emissions
(Ermolaev et al. 2014). Other authors, cited in the Ermolaev study, had a similar finding and attributed
their result partly to the release during turning events of methane trapped within the pile. Oxidation of
methane to carbon dioxide near the pile's surface, by methanogenic bacteria, could also explain part of
the finding that reduced mixing leads to less GHG emissions (Jackel et al. 2005).
30 An analysis of a community-scale composting system showed a moderate to major (10% to >30%)
reduction in gross impact for GWP, acidification, smog formation, and ozone depletion as a result of
avoided nitrogen fertilizer production. Carcinogenic toxicity impact most strongly benefited from the
avoided fertilizer production, with the avoided impact of fertilizer production leading to nearly net zero
impact (Keng et al. 2020). Results for a wasted food aerobic composting system showed moderate to
major reductions in gross GWP and minor to moderate reductions in gross energy demand due to
avoided fertilizer production (Morris et al. 2017). An analysis of wasted food composting that included
windrow, ASP, Gore and bioreactor compost systems identified moderate reductions in gross GWP for all
systems as a result of avoided fertilizer production (Levis and Barlaz 2011). Other authors have identified
only minor environmental benefits associated with avoided fertilizer production for GWP (Righi et al.
2013).
31 The rate of compost application should be calibrated to consider all other nutrient sources such as
legumes and chemical fertilizers, to avoid over-fertilization. Spreading equipment should be capable of
metering compost application to avoid over-applying. Compost should not be applied when soil is frozen,
and other best management practices related to organic amendment applications, such as manure,
should be followed (NRCS and Agricultural BMP Task Force 2017).
32 Food waste is a high-moisture waste product. It should be mixed with a dry, high-carbon material to
absorb moisture and provide structure to the compost pile necessary for aeration and odor control. The
ideal C:N ratio at the time of pile formation is 30:1 with a moisture content of 50% to 70% (Risse and
Faucette 2017).
33 See Trabold and Babbitt (2018) or Mayer et al.(2019)for more information.
34 Some food seasonings have high chlorine levels, which are related to dioxin production potential.
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35 This statement refers to net impacts, which include olive production and olive oil processing in this
analysis.
36 Oily food waste is high in carbon (C:N ratio of 90:1) and can immobilize nitrogen in the soil, affecting
crop yields if sufficient nitrogen is not available.
37 The high carbon content of oily food waste can immobilize nitrate in the soil, prevent leaching, and
make that nitrogen available for subsequent crops through re-mineralization, thus avoiding the need for
additional fertilization.
38 Of the reviewed studies that investigate land-applied wasted food, most indicate that direct application
can benefit soil health, provide nutrients, and boost crop yields, but only if carefully managed temporally
and co-applied with other organic wastes or inorganic fertilizers (Kumar et al. 2009; San Miguel et al.
2012).
39 wasted food "must be applied at or below agronomic rates, and nuisance conditions (such as odors and
flies) and negative impacts on surface and ground waters must be minimized" (Belcher and Aldrich 2006).
40 Batuecas et al. (2019) commented on the risk that groundwater and surface water pollution could result
from application of olive waste to agricultural fields, and a separate study on applying palm oil processing
residues raised similar concerns (Embrandiri et al. 2012).
41 "Landfill gas contains many different gases. Methane and carbon dioxide make up 90% to 98% of
landfill gas. The remaining 2% to 10% includes nitrogen, oxygen, ammonia, sulfides, hydrogen and
various other gases." (NYSDOH 2019).
42 U.S. EPA's Waste Reduction Model (WARM) suggests that under "moderate" moisture conditions, an
appropriate decay rate for food waste is 0.14 yr-1. For paper and wood products, under similar conditions,
decay rates vary between 0.02 and 0.12 yr-1, with higher values indicating more rapid decomposition.
Yard trimmings have an average decay rate under moderate moisture conditions of 0.2 yr-1.
43 For example, lipids were calculated to contribute 59% to 70% of methane potential for a variety of food
wastes in anaerobic environments, though there is a potential for lipids to inhibit methanogens (Lopez et
al. 2016). The authors note the need for further research to clarify the role of lipids in wasted food
decomposition.
44 Reasonable ranges for decay rate and oxidation factor selection may lead to wasted food emissions
varying from 0.23 to 0.71 MTC02e (metric tons of C02 equivalent) per ton of food waste (CARB 2017).
45 Some studies suggest that typical EPA decay rates are too low (Wang et al. 2013), which would lead to
underestimation of the portion of methane produced early in the landfill's life, before the installation of
robust LFG capture systems.
46 The carbon storage potentials of other commonly landfilled organic materials such as cardboard,
newspaper, grass, and dimensional lumber were estimated to be 55%, 84%, 53%, and 88%, respectively
(U.S. EPA 2020b).
47 One study that modeled the landfill as "a 'dry tomb' where microbial activity is suppressed" assumed
that 43% of landfilled carbon was sequestered (Yoshida et al. 2012). This value is considerably higher
than the 16% estimate provided by WARM and is unlikely to apply in moist regions. Additional research
has shown that landfill degradation is more limited in arid regions (Jain et al. 2021).
48 Landfill leachate is the predominant contributor to eutrophication potential in several studies (Edwards
et al. 2017; Lee et al. 2020; Slorach et al. 2020).
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49 Lee et al. (2017) found that when their LCA model was altered to increase LFG collection in the early
stages of cell development, GHG emissions could be reduced by 27% compared to a less aggressive gas
collection strategy.
50 The authors noted that use of these factors was uncertain but was based on the best available
information at the time.
51 Zan et al. (2020) suggested that just 6% of the total COD in wasted food is degraded over a 4-hour
sewer residence time. For comparison, direct GHG emissions from landfilling wasted food are
approximately 16-30+ times greater than these marginal additional sewer emissions from added wasted
food (Zan et al. 2020). In the U.S. context, this 6% figure may overestimate actual sewer emissions, given
that a GIS-based analysis simulating the residence time of 3,422 U.S. sewer systems found that the
median residence time of wastewater is approximately 3.3 hours (as opposed to Zan et al.'s 4-hour
basis), with larger municipalities having longer residence times (Kapo et al. 2017).
52 About 1,265 of the roughly 16,000 WRRFs in the United States process biosolids with AD (ASCE 2021;
U.S. EPA 2023b).
53 Concern that additional wasted food in sewers will drive solids deposition and clogging has not been
universally borne out (Bolzonella et al. 2003). Further study and decision support tools are needed to
navigate potential trade-offs between wasted food conveyance and sewer performance. For instance,
various studies of long-term impacts have shown that, when high-specific-gravity wasted food (e.g.,
bones and egg shells) and/or FOG-rich wasted food are excluded, marginal additional sewer deposits
from wasted food are small and have a minor impact on sewer performance (Mattsson et al. 2015).
Mattsson et al. (2014) used cameras to monitor the effects of food waste disposers on small-diameter
residential pipes across three Swedish municipalities. Despite disposer usage correlating with more
deposits, especially in pipe segments with sags or gentle slopes, these deposits were small and
appeared to have a minor impact on sewer performance (Mattsson et al. 2014).
54 Source separation requires separate collection and transportation infrastructure that is not currently
available in all communities, and sewage collection avoids hygiene and odor problems that can arise
during other forms of collection and transportation (Kauret al. 2019).
55 A survey of local municipal authorities and waste management operators revealed that organizations
providing organic feedstocks to AD operators can expect to meet contamination requirements of less than
5% on a total weight basis (Ogden et al. 2022).
56 The animal feed pathway can address contamination concerns through preprocessing.
Vermicomposting can recover the value of the food waste (in this case nutritional value) by transferring it
to a different carrier (like fly larvae), avoiding the issue of feeding animals food waste with physical
contaminants (Nick Hacheney and Sally Brown 2017).
57 Heterogenous wasted food feedstocks can be difficult to formulate for appropriate animal nutrition.
58 In a 2019 survey of composters in California, 48% reported that contaminated waste streams limit their
ability to accept wasted food (CalRecycle 2019). Regulations governing commercial composting facilities
in Washington State limit physical contamination in compost piles to less than 1% of wet weight with a
plastic content of not more than 0.25% (State of Washington 2019).
59 https://www.epa.gov/air-emissions-factors-and-quantification/emissions-estimation-tools
60 Their reported values range from -4300, -3090, -162 and +536 kg C02e when preventing (source
reduction), donating, digesting and landfilling 1 metric ton of wasted food, respectively. The source
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reduction pathway receives a credit for avoiding food production, as does food donation. The AD and
landfilling options do not receive this credit. Stated differently, the wasted food collected for donation
comes with a negative carbon footprint, so that additional transportation and other processing may
produce some GHG emissions but leaves the overall pathway with a large, net negative carbon footprint.
Food waste enters the AD and landfilling pathways with a neutral (zero) carbon footprint, given its status
as a waste product. These modeling options describe the convention, used in this report, to compare
wasted food pathways to source reduction, wherein source reduction/donation have a virtual net negative
impact while wasted food enters other pathways burden free (i.e. neutral environmental impact).
61 An analysis of AD, composting, controlled combustion, and landfilling of wasted food found that
management pathways have small GWP impacts (and potentials to reduce impact) compared to food
production (Slorach et al. 2020).
62 In 2021, over 65% of landfilled waste was sent to facilities with active energy recovery projects, and
nearly 50% of collected LFG was sent for energy recovery (U.S. EPA 2022a).
63 Including 4% used as alternative daily cover for landfills
64 Excluding scenarios where cover crops are harvested for bio-energy.
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