Nitrous Oxide from Agricultural Sources: Potential Role in Greenhouse Gas Emission Reduction and Ozone Recovery

Nitrous Oxide from Agricultural Sources:

Potential Role in Greenhouse Gas Emission

Reduction and Ozone Recovery

name redacted

Specialist in Agricultural Conservation and Natural Resources Policy

December 7, 2011

Congressional Research Service

7-....

www.crs.gov

R40874

CRS Report for Congress

Prepared for Members and Committees of Congress

N2O: Potential Role in Greenhouse Gas Emission Reduction and Ozone Recovery

Summary

Gases other than carbon dioxide accounted for approximately 17% of total U.S. greenhouse gas

emissions in 2009, yet there has been minimal discussion of these other greenhouse gases in

climate and energy legislative initiatives. Reducing emissions from non-carbon dioxide

greenhouse gases, such as nitrous oxide (N2O), could deliver short-term climate change

mitigation results as part of a comprehensive policy approach to combat climate change.

Nitrous oxide is 310 times more potent than carbon dioxide in its ability to affect the climate; and

moreover, results of a recent scientific study indicate that nitrous oxide is currently the leading

ozone-depleting substance being emitted. Thus, legislation to restrict nitrous oxide emissions

could contribute to both climate change protection and ozone recovery.

The primary human source of nitrous oxide is agricultural soil management, which accounted for

more than two-thirds of the N2O emissions reported in 2009 (approximately 205 million metric

tons CO2 equivalent). One proposed strategy to lower N2O emissions is more efficient application

of synthetic fertilizers. However, further analysis is needed to determine the economic feasibility

of this approach as well as techniques to measure and monitor the adoption rate and impact of

N2O emission reduction practices for agricultural soil management.

As the 112th Congress considers legislation that would limit greenhouse gas emissions, among the

issues being discussed is how to address emissions of non-CO2 greenhouse gases. Whether such

emissions should be subject to direct regulation, what role EPA should play using its existing

Clean Air Act authority, and what role USDA should play in any N2O reduction scheme are

among the issues being discussed. How these issues are resolved will have important implications

for agriculture, which has taken a keen interest in climate change legislation.

Congressional Research Service

N2O: Potential Role in Greenhouse Gas Emission Reduction and Ozone Recovery

Contents

Introduction...................................................................................................................................... 1

Nitrous Oxide: A Primer .................................................................................................................. 2

Sources of N2O Emissions......................................................................................................... 3

The Nitrogen Cycle ................................................................................................................... 3

Opportunities and Challenges for Nitrous Oxide Emission Reduction ........................................... 6

Federal Support for Nitrous Oxide Emission Reduction ................................................................. 7

Policy Options for Nitrous Oxide Emission Reduction................................................................... 8

Figures

Figure 1. Sources and Pathways of Nitrogen (N) Resulting in N2O Emissions from

Agricultural Soil Management ..................................................................................................... 4

Figure 2. County-Level N2O Emissions from Major Cropped Soils in 2005 .................................. 5

Figure 3. The Nitrogen Cycle .......................................................................................................... 5

Tables

Table 1. U.S. Greenhouse Gas Emissions........................................................................................ 2

Table 2. Select N2O Mitigation Alternatives for Agricultural Soil Management............................. 7

Contacts

Author Contact Information............................................................................................................. 9

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N2O: Potential Role in Greenhouse Gas Emission Reduction and Ozone Recovery

Introduction

Policymakers are dedicating considerable attention to greenhouse gas emission reduction,

primarily discussing options for carbon dioxide (CO2) emission reduction.1 Less frequently

addressed in proposed legislation is emission reduction for non-CO2 greenhouse gases, such as

nitrous oxide (N2O). However, N2O reduction efforts have the potential to mitigate climate

change. Moreover, N2O emission sources may be regulated under the existing Clean Air Act as a

class I or class II ozone-depleting substance at the discretion of the Environmental Protection

Agency (EPA) Administrator. No new legislation needs to be passed to regulate N2O for climate

protection and ozone recovery.

The five non-CO2 greenhouse gases regularly monitored but not entirely regulated by EPA

(methane, nitrous oxide, hydroflourocarbons, perflourocarbons, and sulfur hexaflouride)

accounted for approximately 17% of U.S. greenhouse gas (GHG) emissions in 2009, as measured

by total tons of CO2 equivalent.2 Nitrous oxide—the third-most abundant greenhouse gas—was

responsible for roughly 4% of total U.S. GHG emissions in 2009 by weight. Although they

comprise a smaller portion of GHG emissions, non-CO2 greenhouse gases, including N2O, are

more potent than CO2. The gases identified above are 21 to 23,900 times more effective than an

equivalent weight of CO2 at trapping heat in the atmosphere, with N2O being 310 times more

potent by weight.3

In addition to being one cause of greenhouse gas emission growth, N2O is an ozone-depleting

substance (ODS).4 Indeed, scientific analysis suggests that N2O is now the leading ODS being

emitted, as emissions of other substances have been reduced significantly owing to regulations

enacted in the late 1980s, in the Montreal Protocol on Substances that Deplete the Ozone Layer.5

N2O emission reduction could thus play a compelling role in recovery of the ozone layer as well

as in greenhouse gas emission reduction.

The agriculture sector is the primary anthropogenic source of nitrous oxide.6 The bulk of U.S.

N2O emissions stem from fertilizing agricultural soils for crop production. Strategies or

1

For more information on CO2 emission reduction, see CRS Report RL33801, Carbon Capture and Sequestration

(CCS), by (name redacted), and CRS Report RL34621,

Capturing CO2 from Coal-Fired Power Plants: Challenges for a

Comprehensive Strategy, by (name redacted) and (name redacted). For more information on legislative proposals to address

climate change and regulation of greenhouse gases under the Clean Air Act, see CRS Report R40556, Market-Based

Greenhouse Gas Control: Selected Proposals in the 111th Congress, by (name redacted), (name redacted), and

(name redacted); and CRS Report R40585,

Climate Change: Potential Regulation of Stationary Greenhouse Gas

Sources Under the Clean Air Act, by (name redacted) and (name redacted).

2

U.S. Environmental Protection Agency, 2011 U.S. Greenhouse Gas Inventory Report, EPA 430-R-11-005, April

2011, http://www.epa.gov/climatechange/emissions/usinventoryreport.html.

3

The potency of a greenhouse gas is described by its global warming potential (GWP), an estimate of how much a

greenhouse gas affects climate change over a quantity of time relative to CO2, which has a GWP value of 1.

Intergovernmental Panel on Climate Change, Climate Change 2007: The Physical Science Basis (2007), p. 212. The

Intergovernmental Panel on Climate Change (IPCC) assigns nitrous oxide and methane a global warming potential of

310 and 21, respectively, over a 100-year time horizon.

4

An ozone-depleting substance is a compound that contributes to stratospheric ozone depletion by releasing chlorine or

bromine atoms into the atmosphere when broken down, leading to the destruction of ozone, a substance necessary to

prevent harmful UVB rays from reaching Earth.

5

The Montreal Protocol is an international treaty constructed to protect the stratospheric ozone layer by gradually

eliminating a number of ozone-depleting substances.

6

Also in the agriculture sector, animal digestive systems and manure management account for a large portion of U.S.

methane emissions.

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N2O: Potential Role in Greenhouse Gas Emission Reduction and Ozone Recovery

technologies designated for N2O emission reduction are limited.7 This is partly due to the

dispersed nature of N2O emission sources.

In the agriculture sector, the majority of N2O is released as a consequence of specific nitrogen

cycle processes (nitrification and denitrification) when large amounts of synthetic nitrogen

fertilizers are used for crop production. More efficient application of synthetic fertilizers (e.g.,

precision agriculture, nitrogen inhibitors, nitrogen sensors, controlled-release fertilizer products)

is one way to reduce excess amounts of nitrogen available for bacterial processing and eventual

release to the atmosphere as N2O. High costs and difficulty in measuring these products’ efficacy,

among other deterrents, have hampered widespread adoption of practices to reduce N2O

emissions.

This report focuses on the contributions of N2O to alteration in the Earth’s climate and ozone

depletion. Policy options for N2O emission reduction, sources of N2O, and federal support to

lower N2O emissions are discussed.

Nitrous Oxide: A Primer

Nitrous oxide (N2O), familiar to some as “laughing gas,” contributes to climate change and ozone

depletion. Once released, N2O lingers in the atmosphere for decades (its atmospheric lifetime is

approximately 114 years) and is 310 times more effective at trapping heat in the atmosphere over

a 100-year time frame than carbon dioxide (CO2).8 N2O emission quantity estimates remained

fairly constant from 2005 to 2007, hovering around 325 million metric tons carbon dioxide

equivalent (CO2e). N2O emission quantity estimates dropped in 2009 to below 300 million metric

tons CO2e. See Table 1.

Table 1. U.S. Greenhouse Gas Emissions

(million metric tons CO2e)

2005

2006

2007

2008

2009

Avg.

Contributiona

6,113.8

6,021.1

6,120.0

5,921.4

5,505.2

83%

Methane (CH4)

631.4

672.1

664.6

676.7

686.3

9%

Nitrous oxide (N2O)

322.9

326.4

325.1

310.8

295.6

4.4%

Hydroflourocarbons (HFCs)

120.2

123.5

129.5

129.4

125.7

1.8%

Perflouruocarbons (PFCs)

6.2

6.0

7.5

6.6

5.6

<1%

Sulfur hexaflouride (SF6)

19.0

17.9

16.7

16.1

14.8

<1%

7,213.5

7,167.0

7,263.4

7,061.0

6,633.2

Gas / Source

Carbon dioxide (CO2)

Total

Source: Environmental Protection Agency, 2011 U.S. Greenhouse Gas Inventory Report.

a. Average contribution to total U.S. greenhouse gas inventory based on data provided for 2005 to 2009.

7

Strategies and technologies for N2O emission reduction are limited in comparison to resources expended for methane

capture. Methane capture technologies, as well as financial and technical support, for point sources have been available

for decades. For more information on methane capture, see CRS Report R40813, Methane Capture: Options for

Greenhouse Gas Emission Reduction, by (name redacted) et al.

8

S. Solomon, D. Qin, and M. Manning et al., Climate Change 2007: The Physical Science Basis. Contribution of

Working Group I to the Fourth, IPCC, IPCC WG1 AR4 Report, New York, NY, 2007, http://ipcc-wg1.ucar.edu/wg1/

wg1-report.html.

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N2O: Potential Role in Greenhouse Gas Emission Reduction and Ozone Recovery

Sources of N2O Emissions

Nitrous oxide is emitted from anthropogenic (manmade) and natural sources. Oceans and natural

vegetation are the major natural sources of N2O. Agricultural soil management (e.g., fertilization,

application of manure to soils, drainage and cultivation of organic soils) is responsible for more

than two-thirds of anthropogenic U.S. N2O emissions.9 In 2009, N2O emissions from agricultural

soil management totaled more than 200 million metric tons of CO2e.10 Other anthropogenic

sources of N2O are combustion by mobile sources (cars, trucks, etc.), manure management, and

nitric acid production.11

Figure 1 depicts the origination and passage of nitrogen (N) that leads to N2O emissions from

agricultural soil management. The amount of N2O emitted from cropland soils largely depends on

the amount of nitrogen applied to a crop, weather, and soil conditions. Corn and soybean crops

emit the largest amounts of N2O, respectively, due to vast planting areas, plentiful synthetic

nitrogen fertilizer applications, and, in the case of soybeans, high nitrogen fixation rates (Figure

2).12

The Nitrogen Cycle

Comprehension of the nitrogen cycle (Figure 3) is beneficial when crafting policy to reduce N2O

emissions from anthropogenic sources. Nitrogen, an essential element required by organisms to

grow, is found throughout the atmosphere in various forms. The nitrogen cycle portrays the routes

in which nitrogen moves through the soil and atmosphere in both organic and inorganic form.

Certain processes within the nitrogen cycle convert the nitrogen into a form that can be taken up

by plants. Four of the major processes are:

•

nitrogen fixation—conversion of nitrogen gas (N2) to a plant-available form;

•

nitrogen mineralization—conversion of organic nitrogen to ammonia (NH3);

•

nitrification—conversion of ammonia (NH3) to nitrate (NO3-) via oxidation (that

is, by being combined with oxygen); and

•

denitrification—conversion of nitrates back to nitrogen gas.

Nitrous oxide is a byproduct of nitrification and denitrification. Both processes occur naturally.

Excess application of nitrogen fertilizer can lead to increased nitrification, which can cause nitrate

to leach into groundwater or surface runoff (in turn, this causes eutrophication, which can damage

aquatic environments).

9

Agricultural soil management includes practices that add to, or create an environment conducive to the release of,

mineral nitrogen (N).

10

U.S. Environmental Protection Agency, 2010 U.S. Greenhouse Gas Inventory Report, EPA 430-R-10-006, April

2010, http://www.epa.gov/climatechange/emissions/usinventoryreport.html.

11

Mobile (fuel) combustion leads to N2O being emitted as a byproduct. N2O is released as a byproduct during the

oxidation of ammonia for production of nitric acid, a primary component of synthetic fertilizers and some explosives.

N2O emissions are generally released in large amounts from dry manure handling systems (e.g., pasture, solid storage).

12

U.S. Department of Agriculture, U.S. Agriculture and Forestry Greenhouse Gas Inventory: 1990-2005 , Technical

Bulletin No. 1921, 2008, http://www.usda.gov/oce/global_change/AFGGInventory1990_2005.htm. Nitrogen fixation is

the conversion of nitrogen gas to ammonia.

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N2O: Potential Role in Greenhouse Gas Emission Reduction and Ozone Recovery

Figure 1. Sources and Pathways of Nitrogen (N) Resulting in N2O Emissions from

Agricultural Soil Management

Source: U.S. Environmental Protection Agency, 2009 U.S. Greenhouse Gas Inventory Report, EPA 430-R-09-004,

Chapter 6, April 2009. Adapted by CRS.

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N2O: Potential Role in Greenhouse Gas Emission Reduction and Ozone Recovery

Figure 2. County-Level N2O Emissions from Major Cropped Soils in 2005

Source: USDA, U.S. Agriculture and Forestry Greenhouse Gas Inventory: 1990-2005. Adapted by CRS.

Notes: 1 Gigagram (Gg) is equivalent to 1,000 metric tons. Major crops are defined as corn, soybean, wheat,

hay, sorghum, and cotton.

Figure 3. The Nitrogen Cycle

Source: EPA. Adapted by CRS.

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N2O: Potential Role in Greenhouse Gas Emission Reduction and Ozone Recovery

Opportunities and Challenges for Nitrous Oxide

Emission Reduction

N2O emission mitigation options are available for agricultural soil management and nitric acid

production. Nitric acid is a chemical compound used to make synthetic fertilizers. N2O abatement

options for nitric acid production include a high-temperature catalytic reduction method, a lowtemperature catalytic reduction method, and nonselective catalytic reduction.13 The estimated

reduction efficiencies (the percentage reduction achieved with adoption of a mitigation option)

are 90%, 95%, and 85%, respectively.

Agricultural soil management mitigation options recommended by researchers and technology

transfer specialists to discourage excess application of nitrogen fertilizers and soil disturbance

(Table 2) are not generally being practiced. Fertilizer and soil best-management practices aim to

provide the crop with the nutrient and soil conditions necessary for crop production, and prevent

nutrient and soil loss from the crop field (e.g., erosion, leaching).14 Some may consider less

money spent towards fertilizer use an economic incentive for agricultural producers.15 Others may

want to ensure that crop yields meet expected feed, fiber, and fuel mandates (e.g., for corn

ethanol), which may be difficult to attain with less fertilizer use.16 Monitoring reduced nitrogen

fertilization applications on a large scale for greenhouse gas emission reduction purposes may be

difficult; it is not clear how such a program could be managed at a national level.17 Enforcement

options could include voluntary verification, third-party verifiers, or government intervention.

Reporting N2O emissions from agricultural soil management was not included in the Final

Mandatory Reporting of Greenhouse Gases Rule issued by EPA on September 22, 2009.18 EPA’s

reasoning behind this decision was that no low-cost or simple direct N2O measurement methods

exist. Additionally, EPA released a proposed rule requiring new or modified facilities that could

trigger Prevention of Significant Deterioration (PSD) permitting requirements to apply for a

revision to their operating permits to incorporate the best available control technologies and

energy efficiency measures to minimize GHG emissions.19

13

U.S. Environmental Protection Agency, Global Mitigation of Non-CO2 Greenhouse Gases, EPA-430-06-005, 2006.

Catalytic reduction methods use a catalyst to reduce nitrous oxides in exhaust gas at varying temperatures.

14

C. S. Snyder, Fertilizer Nitrogen BMPs to Limit Losses That Contribute to Global Warming , International Plant

Nutrition Institute, Ref. # 08057, June 2008, http://www.ipni.net/ipniweb/portal.nsf/0/

6D54ABC2C92D9AFA8525749B0074FF59.

15

According to the Government Accountability Office, natural gas is the highest-priced factor when producing nitrogen

fertilizer. Thus, natural gas prices impact nitrogen fertilizer costs. U.S. General Accounting Office, Natural Gas:

Domestic Nitrogen Fertilizer Production Depends on Natural Gas Availability and Prices, GAO-03-1148, September

2003, http://www.gao.gov/new.items/d031148.pdf.

16

For example, the Renewable Fuel Standard (RFS) is a provision established by the Energy Policy Act of 2005

requiring gasoline to contain a minimum amount of fuel produced from renewable biomass (including corn). For more

information on the RFS, see CRS Report R40155, Renewable Fuel Standard (RFS): Overview and Issues, by (name

redacted) and (name redacted).

17

For more information on monitoring carbon in agriculture, see CRS Report RS22964, Measuring and Monitoring

Carbon in the Agricultural and Forestry Sectors, by (name redacted) and (name redacted).

18

For more information on the agricultural implications of the Mandatory Reporting of Greenhouse Gases Rule, see

CRS Report RL32948, Air Quality Issues and Animal Agriculture: A Primer, by (name redacted).

19

For more information on the proposed PSD rule, see CRS Report R40585, Climate Change: Potential Regulation of

Stationary Greenhouse Gas Sources Under the Clean Air Act, by (name redacted) and (name redacted); and EPA,

(continued...)

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N2O: Potential Role in Greenhouse Gas Emission Reduction and Ozone Recovery

Table 2. Select N2O Mitigation Alternatives for Agricultural Soil Management

Mitigation Alternative

Description

Split fertilization

Application of same amount of nitrogen fertilizer as in baseline but divided

into three smaller increments during crop uptake period to better match

nitrogen application with crop demand and reduce nitrogen availability for

leaching, nitrification, denitrification, and volatilization.

Simple fertilization reduction (10%,

20%, or 30%)

Reduction of nitrogen-based fertilizer from one-time baseline application of

10%, 20%, or 30%.

Nitrification inhibitor

Reduces conversion of ammonium to NO3-, which slows the immediate

availability of nitrate (nitrate is water soluble). The inhibition of nitrification

reduces nitrogen loss and increases overall plant uptake.

No-till

Conversion from conventional tillage to no-till, where soils are disturbed

less and more crop residue is retained.

Source: EPA, Global Mitigation of Non-CO2 Greenhouse Gases, http://www.epa.gov/climatechange/economics/

downloads/GM_SectionV_Agriculture.pdf.

Federal Support for Nitrous Oxide Emission

Reduction

USDA provides some financial and technical assistance for nutrient management through its

conservation programs.20 Moreover, USDA’s Agricultural Research Service (ARS) is studying the

relationship between agricultural management practices and nitrous oxide emissions.21

In addition to the agriculture sector, work is being done in the transportation sector to

reduce N2O emissions. Mobile combustion was responsible for roughly 8% of N2O

emissions reported in 2009.22 One N2O emission reduction effort, proposed by EPA and

the Department of Transportation, is a per-vehicle N2O emission standard of 0.010 grams

per mile effective in model year 2012 for all light-duty cars and trucks as part of a wider

effort to reduce greenhouse gas emissions and improve fuel economy in tandem.23 EPA

has allocated financial resources to quantify N2O emissions for the greenhouse gas

inventory (e.g., DAYCENT model).24

(...continued)

Proposed Rule: Prevention of Significant Deterioration and Title V Greenhouse Gas Tailoring Rule, 2009,

http://www.epa.gov/NSR/fs20090930action.html.

20

For more information on agricultural conservation programs, see CRS Report R40763, Agricultural Conservation: A

Guide to Programs, by (name redacted). For more information on technical assistance for nutrient management, see CRS

Report RL34069, Technical Assistance for Agriculture Conservation, by (name redacted).

21

For more information on the efforts underway at ARS, visit the Air Quality of Agricultural Systems Research Unit

website at http://www.ars.usda.gov/main/site_main.htm?modecode=36-25-15-15, or the Air Quality National Program

website at http://www.ars.usda.gov/research/programs/programs.htm?NP_CODE=203.

22

U.S. Environmental Protection Agency, 2011 U.S. Greenhouse Gas Inventory Report, EPA 430-R-11-005, April

2010, http://www.epa.gov/climatechange/emissions/usinventoryreport.html.

23

Environmental Protection Agency, Department of Transportation, “Light-Duty Vehicle Greenhouse Gas Emission

Standards and Corporate Average Fuel Economy Standards; Final Rule,” 75 Federal Register, May 7, 2010.

24

EPA uses the DAYCENT ecosystem model for the U.S. greenhouse gas inventory “to estimate direct N2O emissions

from mineral cropland soils that are managed for production of major crops—specifically corn, soybeans, wheat, alfalfa

(continued...)

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N2O: Potential Role in Greenhouse Gas Emission Reduction and Ozone Recovery

Policy Options for Nitrous Oxide Emission

Reduction

Congress has begun to investigate the reduction of non-CO2 greenhouse gas emissions, including

N2O emissions, as one strategy to mitigate climate change. Some contend that N2O emissions

reduction could serve as a short-term response in the larger, long-term scheme of mitigation and

adaptation efforts.25 It may be viewed as a short-term response because N2O emissions make up a

small amount of the GHG inventory compared to CO2 emissions. Any substantial approach to

mitigate climate change is likely at some point to have to address sources that emit CO2.

Congress could approach N2O emissions reduction as part of a comprehensive GHG emission

strategy offering economically attractive abatement alternatives to discourage actions leading to

climate change. For example, a cap or fee on N2O emissions could spur innovative methods for

agricultural producers to limit excess synthetic fertilizer application. Congress could also examine

the tools necessary to identify N2O emission abatement options, assess their cost, and determine

their economic impact for full incorporation into climate change legislation.

Besides greenhouse gas emission reduction, reducing N2O emissions could lead to ozone

recovery. Congress could explore the co-benefits that may arise from restricting N2O emissions

for climate change purposes. N2O is not regulated as an ODS under the Clean Air Act, Title VI,

Stratospheric Ozone Protection (as guided by the Montreal Protocol). As emissions of other ODSs

(e.g., chlorofluorocarbon-11, halon-1211) have declined due to regulation, N2O has emerged as

the dominant ODS emission.26 The first-ever published ozone depletion potential (ODP) value

assigned to N2O, 0.017, is less than the ODP value of 1.0 for the reference gas chlorofluorocarbon

11 (CFC-11). While some may not see a cause for alarm based on the ODP value alone, the

quantity of N2O emissions and its potency as a GHG can lead to serious harm (see Table 1).

The ODP value for N2O does not allow for its mandatory inclusion as a class I substance for

regulation under the Clean Air Act.27 However, N2O could be listed as a class II substance at the

direction of the EPA Administrator or regulated under Section 615 of the act.28 Class I substances

have an ODP of 0.2 or more and are more harmful to stratospheric ozone molecules than Class II

substances, which have an ODP of less than 0.2.

(...continued)

hay, other hay, sorghum, and cotton.”

25

Shilpa Rao and Keywan Riahi, “The Role of Non-CO2 Greenhouse Gases in Climate Change Mitigation: Long-Term

Scenarios for the 21st Century,” Energy Journal, vol. 27 (2006), pp. 1-26; Mario Molina, Durwood Zaelke, and K.

Madhava Sarma et al., “Reducing Abrupt Climate Change Risk Using the Montreal Protocol and Other Regulatory

Actions to Complement Cuts in CO2 Emissions,” Proceedings of the National Academy of Sciences of the United States

of America, October 12, 2009.

26

A. R. Ravishankara, John S. Daniel, and Robert W. Portmann, “Nitrous Oxide (N2O): The Dominant OzoneDepleting Substance Emitted in the 21st Century,” Science Express, August 27, 2009.

27

42 U.S.C. §7671a. The EPA Administrator may add to the list of class I substances any substances that the

Administrator determines as having an ozone depletion potential of 0.2 or greater.

28

42 U.S.C. §7671n. The EPA Administrator has the authority to promptly promulgate regulations respecting the

control of an ODS by submitting notice of the proposal and promulgation of such regulation to the Congress.

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N2O: Potential Role in Greenhouse Gas Emission Reduction and Ozone Recovery

With or without ODP substance listing, Congress may find it useful to incorporate the ozone

depletion impacts of N2O into its climate change policy proposals both to reduce greenhouse gas

emissions and to further ozone recovery achievements. Classifying N2O emission reduction as an

eligible offset type, including N2O as a covered entity within a cap-and-trade program, or

directing EPA to use existing authority under the Clean Air Act to regulate N2O are other

available options to reduce N2O emissions for ozone or climate protection. Any option chosen to

reduce N2O emissions will more than likely require an improvement of N2O estimation,

measurement, and reporting methods and possible financial incentives.

Congress could apply lessons learned from previous international agreements that are intended to

abolish harmful compounds. The outcomes of the Montreal Protocol, put into action in the late

1980s, may prove useful to Congress in understanding the long-term implications of certain

climate change policy options, specifically cap-and-trade. A number of gases were phased out

under the Protocol, which allowed for each country to establish a regulatory framework to

monitor and reduce ODSs. Certain ozone-depleting substances, such as N2O, were not included in

the Protocol partly because their threat was not perceived as urgent at the time. However, one

unintended consequence of the success of the Protocol reducing targeted ODSs is that N2O has

emerged as the leading ODS.

Author Contact Information

(name redacted)

Specialist in Agricultural Conservation and Natural

Resources Policy

#redacted#@crs.loc.gov, 7-....

Congressional Research Service

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