Nitrous Oxide
| Author | Jessica Wentz and David Kanter |
| Pages | 916-939 |
Page 916 Legal Pathways to Deep Decarbonization in the United States
I. Introduction
Nitrous oxide is a key driver of both climate change and
stratospheric ozone depletion. Althou gh relea sed in much
smaller quantities than c arbon dioxide, nitrous oxide is a
particularly potent greenhouse ga s (GHG): it has a 100-
year global warming potential (GWP) of 298, meaning
that it is 298 times more powerful as a heat-trapping gas
than carbon dioxide over a 100-year period.1 Its ozone
depletion potential (ODP) is 0.02 (relative to chlorouo-
rocarbon-11, which has an ODP of 1), which is similar
to many of the substances that are currently being phased
out under the Montreal Protoc ol.2 Nitrous oxide is now
commonly recognized as the most abundantly emitted
ozone-depleting substance (weighted by ODP) and the
1. P. Forster et al., Changes in Atmospheric Constituents and in Radiative Forcing,
in C C 2007: T P S B—C
W G I F A R I-
P C C (Susan Solomon et al. eds.,
Cambridge Univ. Press 2007).
2. A.R. Ravishankara et al., Nitrous Oxide (N2O): e Dominant Ozone-Depleting
Substance Emitted in the 21st Century, 326 S 123 (2009). See also
U N E P (UNEP), D D
N O P O L (2013).
third most abundantly emitted GHG (in terms of carbon
dioxide equivalent) in the United States and abroad.3
Despite the prominent role of nitrous oxide as a driver
of global climate change a nd stratospheric ozone deple-
tion, regulatory programs aimed at addressing these two
problems have historically focused on reducing emissions
of other substances such as carbon dioxide and chlorou-
orocarbons. e primary source s of nitrous oxide emis-
sions—agricultural and livestock operations— are often
included in GHG reduction targets and other policy
goals, but are rarely subject to legally binding emission
controls. is is not surprising, given that agricultural
operations have been exempted or excluded from many
federal environmental statutes and regulations,4 and
there is a strong emphasis on using voluntary programs
to address the environmental impacts of agriculture and
3. P C ., I P C C,
C C 2013: T P S B—C
W G I F A R I-
P C C 677 (T.F. Stocker et al. eds.,
Cambridge Univ. Press 2013); Ravishankara et al., supra note 2. See also
UNEP supra note 2.
4. See M S, C R S, E
R A (2014).
Chapter 35
Nitrous Oxide
by Jessica Wentz and David Kanter
Summary
Nitrous oxide emissions are the third largest driver of climate change and the single greatest threat to the
stratospheric ozone layer. ey accounted for approximately 5% of total U.S. greenhouse gas emissions in 2015
(measured in CO2 equivalent). Key sources of nitrous oxide include agricultural soil and manure management,
stationary and mobile combustion, and industrial processes such as adipic and nitric acid production. ese
sources account for 95% of U.S. nitrous oxide emissions. EPA estimates that U.S. nitrous oxide emissions will
increase approximately 18.5% over 2015 levels by 2030, and these increases will come primarily from the agricul-
tural sector. e Deep Decarbonization Pathways Project reports conclude that nitrous oxide emissions should
be reduced by at least 70 million tons CO2 equivlanet in 2050 relative to a business-as-usual baseline to achieve
an overall net greenhouse gas emission reduction of 80% below 1990 levels by 2050. is chapter explains how
existing legal pathways or new legal mechanisms could be used to attain and even exceed this reduction target.
Page 917
livestock.5 (Agriculture is covered in greater detai l in
Chapter 30.)
is chapter outlines some of the existing reg ulatory
pathways that could be used to control nitrous oxide emis-
sions in the United States, and evaluates the environmental
and economic impacts associated with di erent regulatory
scenarios. One key nding is t hat the federal Clean Air Act
(CAA) contains provisions that could be used to control
emissions from each of the major nitrous oxide sources:
agricultural soil management, manure management, sta-
tionary combustion, mobile combustion, and industrial
processing. Other tools could also be used to regulate
nitrous oxide emissions if the federal government does not
exercise its authority under the CA A.
Another key nding is th at a greater emphasis on nitrous
oxide reduction would not only help to protect the climate
and stratospheric ozone l ayer—it wou ld also y ield substan-
tial environmental and economic co-benets in the coming
decades.6 For example, practices that control nitrous oxide
emissions from agriculture and ma nure management can
reduce other forms of nitrogen pollution, such as nitrate
leaching, and ammonia a nd nitrogen oxide emissions—
each with its own unique environmental and healt h impacts.
Accounting for the avoided damages from nitrous oxide
and other forms of nitrogen pollution as well as abatement
costs, we nd that a program a imed at reducing agricultur al
nitrous oxide emissions by approximately 35% (a target that
could be achieved through improvements in nitrogen use
ecie ncy)7 could resu lt in a net economic benet of approx-
imately $110 billion per year (when fully implemented).
Additional details on the mitigation potential, costs, and
co-benets of dierent control measures are provided below.
Section II describes the key sources of nitrous oxide
emissions in the United States, the extent to which these
sources are or are not regulated under U.S. law, and the
technical mitigation potential for each of these sources.
Section III goes into detail about the lega l pathways for
reducing emissions from each of these key sources, focu s-
5. See, e.g., U.S. Department of Agriculture (USDA), Natural Resources
Conservation Service, Environmental Quality Incentives Program, http://
www.nrcs.usda.gov/wps/portal/nrcs/main/national/programs/financial/
eqip/ (last visited Jan. 27, 2018); New York State Soil and Water Con-
servation Committee, Agricultural Environmental Management, http://
www.nys-soilandwater.org/aem/ (last visited Jan. 27, 2018); Michigan
Department of Agriculture and Rural Development, Michigan Agriculture
Environmental Assurance Program (MAEAP), http://www.michigan.gov/md
ard/0,4610,7-125-1599-12819--,00.html (last visited Jan. 27, 2018).
6. See UNEP, supra note 2, at 42.
7. e 34.7% reduction gure is based on UNEP projections of emissions
reductions that could be achieved through enhanced nitrogen eciency in
crop and animal production. See UNEP, supra note 2, at 24.
ing on how emissions could be controlled under: (1) the
CAA; (2) emissions trading systems; (3) state and local
approaches; and (4) incentives, technical support, and
private governance approaches. Section III also contains
specic recommendations on how to utilize each of these
pathways, which are summarized at the end of each sub-
section. Section IV concludes.
II. Background: U.S. Nitrous Oxide
Emissions and Abatement Options
Nitrous oxide emissions are generated from a variety of
sources and represent a modest but nonetheless meaning-
ful proportion of total U.S. GHG emissions. is section
will review the latest data on current and projected nitrous
oxide emissions, describe the key sources of those emis-
sions, and identify emissions abatement options for each
of those key sources. One main nding is that there are
ample opportunities to reduce nitrous oxide from dierent
sources and to obtain or even exceed the Deep Decarbon-
ization Pathways Project (DDPP) target.
According to the U.S. Environmental Protection Agen-
cy ’s ( EPA’s) Inventory of U.S. Greenhouse Gas Emissions and
Sinks: 1990-2015, nitrous oxide emissions accounted for
approximately 5% of total U.S. GHG emissions in 2015.8
Total nitrous oxide emissions were 343.2 million tons (MT)
carbon dioxide equivalent in that year, including land use,
land use change, and forestry (LULUCF).9 Nitrous ox ide
emissions from LULUCF were 8.4 MT carbon dioxide
equivalent. In 2012, EPA projected that these emissions
will increase by 18.5% over 2015 levels to 452.6 MT carbon
dioxide equivalent in 2030.10 at study, however, may have
overestimated emissions growth, as it predicted that 2015
emissions would be 382.1 MT carbon dioxide equivalent.11
ere are no ocial EPA projections of U.S. nitrous oxide
emissions by 2050, and it would not make sense to assume
the exact same emissions trajec tory for the years 2030-2050.
For this reason, the following discussion of projected emis-
8. EPA, I U.S. G G E S: 1990-
2015, at ES-5 to ES-8 tbl. ES-2 (2017) (EPA 430-P-17-001) [hereinafter
EPA GHG I)], available at https://www.epa.gov/ghgemissions/
inventory-us-greenhouse-gas-emissions-and-sinks-1990-2015. Note that the
5% estimate is based on gross GHG emissions, not including land use, land
use change, and forestry (LULUCF) (this is the most common approach
used by EPA to report emissions).
9. Id.
10. O A P, EPA, G A
N-CO2 G G E: 1990-2030—A
R (2012) [hereinafter EPA N-CO2 P], available
at https://www.epa.gov/sites/production/les/2016-05/documents/appen-
dices_global_nonco2_projections_dec2012.pdf.
11. Id.
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