Agriculture and Greenhouse Gases

Congressional research reportDec 10, 2010

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December 10, 2010

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R41530

CRS Report for Congress

Prepared for Members and Committees of Congress

Agriculture and Greenhouse Gases

Summary

This report examines the implications for agriculture of the ongoing but inconclusive debate

about global climate change. In that debate, agriculture’s role is multifaceted. Agriculture is both

a source of several greenhouse gases (GHGs) and a “sink” for absorbing carbon dioxide, the most

common GHG, thereby partly offsetting emissions. Overall, agriculture is a comparatively modest

source of U.S. GHG emissions: it accounts for approximately 7% of U.S. emissions, while sectors

such as transportation and electricity generation account for much larger shares. Agriculture’s

GHG emissions are principally in the form of methane and nitrous oxides emissions.

Whatever the current or future Congresses may do regarding climate legislation, interest in

existing and prospective responses by government and others will continue. Administration

efforts to develop policies and strategies to address GHGs and climate change have been

underway for some time. Two actions by the Environmental Protection Agency (EPA) have drawn

the attention of the agriculture industry. One is regulating emissions of GHGs under the Clean Air

Act (CAA) and subsequent GHG emission standards for new motor vehicles which, in turn,

trigger certain CAA permitting requirements. A second, related action is a rule to require

reporting of GHG emissions by certain facilities. Regarding both, EPA took steps to focus on the

largest emitters and ensure that few agricultural sources would be subject to new GHG

requirements. Still, EPA’s overall initiatives have been widely criticized, and the 111th Congress

intervened through a funding bill to largely exclude agriculture from EPA’s regulatory

requirements. During the 111th Congress, the House passed a comprehensive climate change bill

(H.R. 2454), and a Senate committee reported a companion (S. 1733). Although no legislation

was enacted, both bills included provisions excluding agriculture from regulatory requirements

and promoting agricultural practices to reduce or offset emissions from regulated sources.

Traditionally, practices such as conservation tillage have been used for soil conservation and

water quality improvement, but their value for climate change abatement or mitigation is

receiving increased attention. A number of strategies, technologies, and practices exist to reduce

methane and nitrous oxides emissions at the farm level, but implementation faces financial and

monitoring challenges.

Programs administered by the U.S. Department of Agriculture (USDA) provide financial

incentives and technical assistance to encourage implementation of certain farming practices.

While the focus of most programs is not on GHG emission reduction, USDA is giving greater

attention to GHGs in administering its suite of existing programs.

Results of the 2010 congressional elections have altered political dynamics in Congress on many

issues, and leadership of both political parties have indicated that neither currently plans to pursue

comprehensive approaches to addressing climate change in the 112th Congress, although some

elements of previous proposals may move through the legislative process. How agriculture fits in

these discussions—both as a source of GHG emissions and contributions that the sector can make

to mitigating climate change—has drawn interest in the past and likely will do so again.

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Contents

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

Agricultural Emissions and Sequestration of Greenhouse Gases .................................................... 2

Carbon Dioxide ......................................................................................................................... 3

Methane and Nitrous Oxides ..................................................................................................... 4

Methane Emissions from Agriculture.................................................................................. 5

Nitrous Oxides Emissions from Agriculture ....................................................................... 6

Data Uncertainty and Varying Estimates ................................................................................... 7

EPA Activities .................................................................................................................................. 8

Regulating GHGs under the Clean Air Act and the Tailoring Rule ........................................... 8

Mandatory Reporting of Greenhouse Gases .............................................................................. 9

Congressional Interest.................................................................................................................... 10

Agricultural Conservation Practices and GHGs ............................................................................ 12

USDA Activities and Programs ..................................................................................................... 14

Conservation Programs ........................................................................................................... 15

Environmental Services Markets....................................................................................... 17

Other USDA Farm Programs ............................................................................................ 18

Conclusion ..................................................................................................................................... 19

Figures

Figure 1. Estimated Emissions of Methane and Nitrous Oxides: U.S. Total and

Agricultural Sector, 2008.............................................................................................................. 5

Tables

Table 1. Estimated GHG Emissions and Sequestration: U.S. Agriculture and U.S. Total,

All Sources (2008) ........................................................................................................................ 2

Table 2. Conservation Practices and GHGs ................................................................................... 14

Table 3. Estimated GHG Mitigation Impact of USDA Conservation Programs............................ 17

Table A-1. Estimated Emissions of Methane and Nitrous Oxides: U.S. Agriculture (2008) ......... 20

Table B-1. USDA Conservation Programs and Land Management Practices ............................... 21

Appendixes

Appendix A. Agricultural Sector Emissions of Methane and Nitrous Oxides ............................... 20

Appendix B. Conservation Practices and Programs Affecting GHGs ........................................... 21

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Contacts

Author Contact Information........................................................................................................... 23

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Introduction

This report examines the implications for agriculture of the ongoing but inconclusive debate

about global climate change.1 Whatever the current or future Congresses may do regarding

climate legislation, interest in existing and prospective governmental and private sector responses

will surely continue. Existing governmental climate change activities affecting or potentially

affecting agriculture include the Environmental Protection Agency’s (EPA) initiative under the

Clean Air Act to address emissions of greenhouse gases (GHGs); U.S. Department of Agriculture

(USDA) conservation programs that can encourage practices affecting agriculture’s emissions or

sequestration of GHGs; and provisions of law encouraging the use of biofuels.2 Private sector

concerns about climate change also could affect agriculture. For example, some companies

increase investment in drought-tolerant seed technology in response to water resource pressures

and potentially longer periods of extreme temperatures resulting from a changing climate.

In the climate change debate, agriculture’s role is multifaceted. Agriculture is both a source of

several GHGs and a “sink” for absorbing carbon dioxide, the most common GHG, thereby partly

offsetting emissions. Overall, agriculture is a comparatively modest source of U.S. GHG

emissions: it accounts for approximately 7% of U.S. emissions, while transportation accounts for

27% and electricity generation for 35%. Further, it should be recognized that the data on various

agriculture emissions are of varying precisions and that the implications of land use changes for

emissions are not well understood and are hard to measure. Similarly, agriculture is a dynamic

activity and emissions/sequestration can change and also can be manipulated to some degree.

During the 111th Congress, comprehensive climate change legislation passed the House and was

reported by a Senate committee, but no comprehensive bill was enacted. At the same time, the

Administration moved forward on several fronts to address climate change, including research,

EPA’s clean air initiative, and USDA’s promotion of conservation practices that can diminish

emissions. As these various initiatives progressed, the agriculture community weighed in at

several points. One outcome was that the comprehensive climate change bills largely excluded

agriculture from regulatory requirements, and another was that Congress through a funding bill

excluded agriculture from certain EPA regulatory requirements concerning reporting of emissions

(e.g., from manure management practices).

This report places in context federal agricultural policymaking with respect to the climate change

debate. It describes agricultural activities involving cropland and livestock production that

contribute to emissions and sequestration of GHGs; it reviews recent climate change initiatives,

agricultural stakeholder responses, and current status; and it summarizes the implications of

ongoing federal programs affecting agricultural emissions and sequestration.

This report does not address the underlying debate over global climate change and the role or humans in contributing

to it. For discussion on the science and policy of global climate change, see CRS Report RL34266, Climate Change:

Science Highlights, by (name redacted), and CRS Report RL34513, Climate Change: Current Issues and Policy Tools,

by (name redacted).

Discussion of biofuels is beyond the scope of this report. However, for further information, see CRS Report R41282,

Agriculture-Based Biofuels: Overview and Emerging Issues, by (name redacted), and CRS Report RL34738,Cellulosic

Biofuels: Analysis of Policy Issues for Congress, by (name redacted) et al..

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Agricultural Emissions and Sequestration of

Greenhouse Gases

Agricultural activities can be both a source and a “sink” for GHGs, releasing several GHGs

through plant and animal respiration and plant decomposition and removing carbon dioxide (CO2)

through photosynthesis, thus storing/sequestering it in vegetation and soils.3 Animal agriculture

contributes directly to emissions of GHGs through a variety of processes such as enteric

fermentation in domestic livestock (i.e., digestion) and manure management systems and

practices. Non-livestock source categories in agriculture likewise emit GHGs, including rice

cultivation, agricultural soil management, and field burning of agricultural residues. A range of

land management, agricultural conservation, and other farmland practices also can reduce or

abate emissions and/or sequester carbon to some extent. These include soil conservation, manure

and grazing management, and land retirement, conversions, and restoration.

As shown in Table 1, agriculture is estimated to have emitted 6.9% of total U.S. greenhouse gas

emissions in 2008, including CO2, methane (CH4), and nitrous oxides (N2O). Conversely,

agriculture is estimated to have been a sink for 5.4% of total GHG emissions that were

sequestered in the United States. Unlike other prominent economic sectors (e.g., electricity

generation and transportation), agriculture sector emissions are dominated by CH4 and N2O, not

CO2.4

Table 1. Estimated GHG Emissions and Sequestration: U.S. Agriculture and U.S.

Total, All Sources (2008)

Million Metric Tons of CO2 equivalent (MMTCO2e)

Source

Emissionsa

Sequestrationb

Net

Agriculture CO2

59.9

(51.0)

8.9

Agriculture CH4

194.0

—

194.0

Agriculture N2O

233.2

—

233.2

Agriculture Subtotal

480.5

(51.0)

429.5

U.S. Total, All Sources

6,956.8

(940.3)

6,016.4

6.9%

5.4%

% U.S. Total, Agriculture

—

Source: U.S. Environmental Protection Agency, Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2008,

April 15, 2010, EPA 430-R-10-006, Tables ES-7, 7-1, 2-12; calculations by CRS.

Includes CO2, CH4, and N2O emissions attributable to the agriculture sector, including land use/land use

changes and fossil fuel combustion from transportation and other on-farm activities. Excludes emissions

from forestry activities and emissions allocated to electricity generation for agricultural activities.

Forestry activities, although not a focus of this report, also can be both a source and a sink of GHGs, releasing GHGs

through plant decomposition and removing CO2 through photosynthesis, storing (sequestering) it in trees, vegetation,

and soils.

U.S. Environmental Protection Agency, Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2008, April 15,

2010, EPA 430-R-10-006, http://www.epa.gov/climatechange/emissions/usinventoryreport.html. Hereafter,

Greenhouse Gas Inventory.

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Measured agricultural sequestration categories include cropland remaining as cropland, grassland remaining

as grassland, land converted to cropland, and land converted to grassland. Excludes sequestration by

forestry activities.

Carbon Dioxide

Billions of tons of carbon in the form of CO2 are emitted to the atmosphere annually from

anthropogenic sources and natural processes. Some agricultural land management uses and

practices involve both emissions and removal of CO2 from the atmosphere, a combination that is

referred to as CO2 flux. Agriculture directly emits CO2 from fossil fuel combustion by

transportation and other on-farm activities; fossil fuel combustion by agricultural sources

accounted for an estimated 45.4 million metric tons of CO2 equivalent (MMTCO2e) in 2008, or

76% of the CO2 emissions shown in Table 1.

Agriculture soils also emit relatively small amounts of carbon through the application of liming

and urea fertilizer (7.6 MMTCO2e in 2008). The U.S. agricultural sector is a minor source of CO2

emissions—1% in 2008—while electricity generation accounts for 40%, and transportation

accounts for 30%. On the other hand, agricultural soils sequester nearly nine times more carbon

than they emit. Soil carbon sequestration is largely due to conversion of cropland, an increase in

adoption of conservation tillage practices that preserve soil carbon, and an increase in the amount

of organic fertilizer (manure and sewage sludge) that farmers apply to croplands in place of

synthetic fertilizers.5

EPA’s Greenhouse Gas Inventory reports on four categories of agricultural land use practices.

Three of these categories—cropland remaining as cropland, grassland remaining as grassland,

and land converted to grassland—demonstrated carbon sequestration in 2008, while the fourth—

land converted to cropland—contributed emissions of about 6 MMTCO2e, not sequestration.

Carbon sequestration on farm lands is currently estimated to contribute more than 5% of total

sequestration by all sources (which occurs principally through forested lands remaining forest

land) and to mitigate less than 1% of total annual GHG emissions in the United States (forested

lands mitigate about 11% of total annual GHG emissions in the United States).

There is ongoing debate about the permanence, or duration, of many carbon sequestration

practices. Permanence depends on the practice itself and such site-specific factors as location,

climate and land condition. For example, reforestation and similar forestry activities may be

capable of long term emission reduction (from 20 to 200 years). However, cropping practices

such as conservation tillage or other cropland changes (e.g., transitioning to improved pasture)

may or may not be long term, depending on how long a farmer maintains the practice, whether a

farmer receives and continues to receive financial or technical assistance as incentive for

maintaining the practice, whether the farmer is able to withstand lower yields in the near-term, or

whether high prices shift idle land back into production.6

Ibid., p. ES-12.

For further information, see CRS Report RS22964, Measuring and Monitoring Carbon in the Agricultural and

Forestry Sectors, by (name redacted) and (name redacted).

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Methane and Nitrous Oxides

The two principal GHGs emitted by agricultural sources are CH4 and N2O. An estimated one-half

of global CH4 comes from anthropogenic sources (i.e., from human activities), of which

agriculture is the largest source; livestock production is a major component within the sector.7

EPA estimates that nearly one-third of U.S. CH4 emissions come from livestock. Agricultural CH4

is produced by ruminant animals, but it also is emitted during microbial degradation of organic

matter under anaerobic conditions. Nitrous oxides are formed as a result of crop fertilization

practices, directly via the microbial processes of nitrification and denitrification, and indirectly

via volatilization and surface water runoff and leaching into ground water.

In 2008, total anthropogenic emissions of CH4 and N2O from all U.S. sectors were 885.8

MMTCO2e, while total agricultural sector GHG emissions of these two GHGs totaled 427.5

MMTCO2e, or 48% of total U.S. emissions of both GHGs.8 As shown in Figure 1, agricultural

emissions of CH4 are predominantly from enteric fermentation in domestic livestock, with lesser

contributions by livestock manure management, rice cultivation, and field burning of agricultural

residues. Over 90% of agricultural emissions of N2O are from agricultural soil management, with

small contributions by livestock manure management and field burning of agricultural residues.9

Ibid. Also see CRS Report R40813, Methane Capture: Options for Greenhouse Gas Emission Reduction, by (name

redacted) et al.

Different GHGs have varying potential to impact climate change by trapping heat in the atmosphere. In particular,

CH4 and N2O have greater potency, relative to CO2. Over a 100-year time horizon, CH4 emissions have 21 times more

potency than equivalent tonnage of CO2, and N2O emissions are 310 times more potent than CO2. To correct for these

differences, actual emissions of each GHG are converted to the equivalent amount of CO2 emissions, based on how

potent the substance is compared to CO2, giving rise to the term “CO2-equivalent.” This measure allows for a

comparison of the impacts of emissions of different gases. The figures throughout this report are expressed in carbon

equivalents. Greenhouse Gas Inventory, Table ES-1, page ES-3.

See Table A-1 in the Appendix of this report for more detail.

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Figure 1. Estimated Emissions of Methane and Nitrous Oxides: U.S.Total and

Agricultural Sector, 2008

Million Metric Tons of CO2 equivalent (MMTCO2e)

Source: Prepared by CRS from U.S. Environmental Protection Agency, Inventory of U.S. Greenhouse Gas Emissions

and Sinks: 1990-2008, April 15, 2010,EPA 430-R-10-006, Tables 6-1, 2-1.

Methane Emissions from Agriculture

Livestock sources were responsible for one-third of all U.S. CH4 emissions in 2008. More than

three-quarters of CH4 emissions from livestock resulted from normal digestive processes (i.e.,

enteric fermentation10) in ruminant animals such as cattle, sheep, and goats. Cattle account for the

majority of CH4 emissions from U.S. livestock (because of their large population, large animal

size, and particular digestive characteristics), and emissions changes over time tend to track

Enteric fermentation is the production and release of CH4 via eructation (burping) and flatulence as ruminant animals

digest their feed.

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changes in beef and dairy cattle populations. Feed quality and the amount of feed intake by

animals also affect CH4 emissions.11

The management of livestock manure also can produce CH4. Methane is produced from the

decomposition of liquid-based livestock manure that is stored or treated in lagoons, ponds, tanks,

or pits. Factors that affect the amount of CH4 produced include temperature, moisture, and storage

time, because they influence the growth of bacteria that are responsible for CH4 formation. An

animal’s feed also can be a factor: in general, the greater the energy content of the feed, the

greater the potential for methane emissions.

When manure is handled as a solid or deposited on pasture, range, or paddock lands, it produces

little or no CH4, and in fact, the majority of manure in the United States is handled as a solid.

However, the general trend in manure management, particularly for dairy and swine, is towards

use of liquid systems. According to EPA, states such as California, New Mexico, and Idaho have

seen increases in dairy populations as the industry becomes more concentrated, along with greater

use of liquid-based systems to manage and store manure. A consequence of the dairy industry’s

shift toward larger facilities translates into an increasing use of liquid manure management

systems, which have higher potential CH4 emissions than dry systems. Between 1990 and 2008,

methane emissions from manure management increased on average 2.5% annually. The majority

of this increase was from swine and dairy cow manure, where emissions increased 50% and 91%,

respectively.12

Rice cultivation and field burning of agricultural residues also contribute CH4 emissions, but they

are small contributors of U.S. emissions (1.5% of all CH4 emissions). Crop residue burning also

produces small amounts of both CH4 and N2O (see Figure 1 and Table A-1). Although field

burning is not a widely used practice of farmers for disposing of crop residues, it is used

throughout the United States for disposal of about 3% of the residue of wheat, rice, sugarcane,

corn, barley, soybeans, and peanuts. According to EPA, annual emissions from this source have

remained relatively constant since 1990.13

Nitrous Oxides Emissions from Agriculture

Nitrous oxides emissions are produced by biological processes that occur in soil and water and by

a variety of human activities involving agriculture, energy, industry, and waste management.

Agricultural soil management practices (e.g., fertilizer application and other cropping practices)

produce the majority of N2O emissions in the United States and accounted for nearly 68% of U.S.

N2O emissions in 2008.14 Year to year fluctuations in agricultural soil emissions of N2O reflect

variations in weather patterns, synthetic fertilizer use, and crop type.15

A number of agricultural activities increase mineral nitrogen availability in soils, thereby

increasing the amount available for the microbial processes that produce nitrous oxide. Direct

increases in soil mineral nitrogen occur as a result of practices such as fertilization, application of

Lower feed quality and/or higher feed intake leads to higher emissions. Ibid., p. 6-2.

Greenhouse Gas Inventory, p. 6-7.

Greenhouse Gas Inventory., p. 6-27.

For more information, see CRS Report R40874, Nitrous Oxide from Agricultural Sources: Potential Role in

Greenhouse Gas Emission Reduction and Ozone Recovery, by (name redacted).

Greenhouse Gas Inventory, pp. 6-16 – 6-19.

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manure on soils, and production of nitrogen-fixing crops and forages such as clover and alfalfa.

Direct N2O emissions from croplands tend to be high in the Corn Belt states where highly

fertilized corn and nitrogen-fixing soybean crops are grown. Direct emissions also tend to be high

from grasslands in the central and western states where a high proportion of land is used for cattle

grazing (e.g., emissions by grazing animals whose manure is not managed and from retention of

crop residues).

Indirect emissions, which occur when mineral nitrogen is transported from the soil either in

gaseous or aqueous forms and later is converted into N2O, comprise about 25% of emissions from

agricultural soil management activities. These types of emissions occur in many of the same U.S.

regions as direct emissions (e.g, central and western United States). There are two pathways

leading to indirect emissions. The first results from volatilization of nitrogen to the atmosphere

(e.g., from nitrogen fertilizer). Indirect emissions also occur through surface transport and runoff

from farmland into nearby streams and lakes.

Livestock manure management activities produce N2O emissions, as well as CH4. Direct N2O

emissions are released from dry manure handling systems, pasture, solid storage, and—similar to

agricultural soil management activities—indirect emissions result from volatilization of nitrogen

or runoff of nitrogen during manure treatment, storage, and transportation. Both direct and

indirect emissions of N2O have remained fairly steady since 1990, according to EPA.16

Data Uncertainty and Varying Estimates

Scientists have considerable confidence in characterizing U.S. GHG emissions, particularly for

major industrial sectors where statistics such as fossil fuel consumption are relatively accurate. At

the same time, EPA and others recognize that there are uncertainties associated with some of the

emission estimates data, especially for sectors that are smaller contributors of emissions, due to a

lack of data or an incomplete understanding of how emissions are generated or may be measured.

Uncertainty is apparent in much of the data on agriculture’s emissions that are presented in EPA’s

Greenhouse Gas Inventory. Emissions estimated in the Inventory may vary from year to year

based on new data and changes in assumptions and methodology. Regarding CH4 emissions from

enteric fermentation, which are the main agricultural source of those emissions, the Inventory

states that the lower- and upper-bound uncertainties are -11% and +18%. However, regarding

other emissions, such as N2O emissions from soil management, which is the main agricultural

source of those emissions, there is greater uncertainty. For example, direct emissions, which

account for the majority of N2O emissions from agricultural soil management, have lower- and

upper-bound uncertainties of -24% and +63%, while indirect emissions (i.e., from volatilization)

have greater uncertainties due to lack of data, as well as uncertainties regarding major crops and

application of manure and other organic fertilizer amendments: the uncertainty range in the report

is -48% and +142%.17

Notwithstanding specific uncertainties, whether agriculture’s emissions are 7% of the U.S. total,

as reported in EPA’s Inventory, or 3%, or 11%, is not especially critical to policy debates about

GHG emissions and climate change. What is evident in the data is that agriculture is a much

Ibid., pp. 6-6 – 6-7.

Ibid., pp. 6-5, 6-25. To account for data uncertainty and methodological changes in the Inventory, some analysts

report emissions averages (e.g., from 2004-2008) rather than single year estimates that are used in this report.

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smaller source of emissions than other economic sectors—especially electricity generation and

transportation. Thus, while policy debate about climate change continues to occur internationally,

nationally, and regionally, one question is where does agriculture fit in those discussions. Broadly

speaking, there are three distinct policy tracks that could define agriculture’s role. One option

would be to regulate agriculture and other sources of GHGs in order to mitigate or abate

emissions. A second would be to promote practices by agricultural sources that may diminish or

mitigate the sector’s emissions voluntarily. A third option would be to do nothing.

EPA Activities

Efforts have been underway in the Administration to develop policies and strategies to address

GHGs and climate change. The 111th Congress, too, considered legislation in this area:

comprehensive climate and energy legislation passed the House in July 2009 and was reported by

a Senate committee, but no comprehensive bill was enacted. Agriculture generally has been a

major part of these discussions, but so far the agriculture sector has been largely excluded from

regulatory and legislative proposals. Two sets of actions by the EPA concerning GHG emissions

have drawn stakeholders’ attention.

Regulating GHGs under the Clean Air Act and the Tailoring Rule

First, in July 2008, the Bush Administration published an Advance Notice of Proposed

Rulemaking (ANPR) in connection with its consideration of how it should comply with

Massachusetts v. EPA, in which the Supreme Court held that the Clean Air Act (CAA) authorizes

EPA to regulate emissions from new motor vehicles on the basis of their climate change impacts.

The Court held that the EPA Administrator must determine whether or not emissions of GHGs

from new motor vehicles cause or contribute to air pollution which may reasonably be anticipated

to endanger public health or welfare (i.e., an endangerment finding), or whether the science is too

uncertain to make a reasoned decision.18 Responding to this ruling with the ANPR, EPA discussed

a wide range of CAA authorities and programs that could potentially be used to address climate

change, including the permitting provisions in Title V of the act.19 The ANPR did not propose or

recommend the use of any particular CAA authority, or commit to specific next steps to address

GHGs from any category of emission sources.

Agricultural sources were not specifically referenced in any of this ANPR discussion;

nevertheless, agriculture stakeholders—especially many representing livestock operations—were

highly critical of potential economic impacts on their operations and the possibility that Title V

permits might be required. In the months following the ANPR, EPA officials said that the agency

had no plans to tax livestock or pursue other “doomsday scenarios” for new regulations.20 The

public comment period on the ANPR ended in November 2008; no further action on it occurred.

549 U.S. 497 (2007). For information, see CRS Report RS22665, The Supreme Court’s Climate Change Decision:

Massachusetts v. EPA, by (name redacted).

Title V requires major industrial sources of air pollutants to obtain permits which detail all of the federal emission

control requirements that apply to the facility.

EPA Administrator Lisa P. Jackson, “Address, 2009 USDA Agricultural Outlook Forum,” Feb. 26, 2009,

http://www.usda.gov/oce/forum/2009_Speeches/Speeches/Jackson.pdf.

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However, in December 2009, EPA Administrator Jackson signed two endangerment findings

about GHGs. First, the Administrator found that the current and projected concentrations of six

GHGs in the atmosphere (including CH4 and N2O) threaten the public health and welfare of

current and future generations. Second, the Administrator found that GHG emissions from motor

vehicles contribute to the atmospheric concentrations of the six key GHGs and hence to the threat

of climate change.21 The endangerment finding does not itself impose any CAA requirements on

industry or other entities or trigger regulation under the entire act. However, the endangerment

finding is a prerequisite to finalizing proposed greenhouse gas emission standards for light-duty

vehicles, which EPA proposed jointly with the Department of Transportation in September 2009.

When EPA’s proposed light-duty vehicle rule takes effect (expected to be January 2011), other

CAA requirements will be triggered. In particular, stationary sources that emit any of the six

GHGs covered by the endangerment finding will be subject to certain permitting requirements

under the Title V operating permit and New Source Review (NSR) provisions in the law.22

Related to the CAA requirements that are triggered by the endangerment finding and light-duty

vehicle rule, on May 13, 2010, EPA issued a rule specifying thresholds for GHG emissions that

define when Title V and NSR permits would be required. In the absence of the rule, called the

GHG Tailoring Rule, sources that emit as little as 100 tons per year of CO2 equivalent of GHGs

would be subject to CAA permits. In order to limit the number of facilities that would be required

to obtain permits, in the Tailoring Rule EPA established a threshold of 100,000 tons per year of

CO2 equivalent of GHG emissions. EPA estimates that the rule will cover 67% of the nation’s

largest stationary source GHG emitters, while shielding small businesses and agriculture

operations from new permitting requirements.23 EPA believes that livestock and production

agriculture operations will not be subject to CAA permitting as a result of the Tailoring Rule,

because of the high threshold in the rule and because the rule does not apply to so-called “fugitive

emissions” from sources of enteric fermentation and animal manure management systems.24

The Tailoring Rule does apply to GHG emissions from internal combustion diesel engine

generators, including those used on farms. However, because of the 100,000 tpy threshold in the

rule, EPA estimates that no farm stationary fuel combustion sources emit GHGs (i.e., CO2) at

levels that would be subject to the rule.

Mandatory Reporting of Greenhouse Gases

A second EPA action that drew agriculture’s attention was an April 2009 EPA proposal to require

reporting by certain facilities that emit GHGs and by suppliers of fossil fuels and industrial

GHGs. The proposal responded to a congressional directive in the FY2008 Consolidated

Appropriations Act (P.L. 110-161) for EPA to develop a comprehensive national system for

reporting emissions of CO2 and other GHGs produced by major U.S. sources. Included in the

categories of sources that would be subject to the proposed rule were manure management

systems that emit, in the aggregate, methane and nitrous oxide in amounts equivalent to 25,000

For additional information, see http://www.epa.gov/climatechange/endangerment.html.

For additional information, see CRS Report R40984, Legal Consequences of EPA’s Endangerment Finding for New

Motor Vehicle Greenhouse Gas Emissions, by (name redacted). New Source Review (NSR) is a CAA program designed

to minimize emissions from new sources and existing sources that are making major modifications.

See “Final GHG Tailoring Rule” at http://www.epa.gov/NSR/actions.html#may10.

Fugitive emissions are generally defined as emissions which are not released, or could not be reasonably collected

and released, through a stack or vent.

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metric tons of CO2 equivalent or more per year. Because of the proposed reporting threshold, EPA

initially estimated that fewer than 50 beef cattle, dairy cattle, and swine operations would be

subject to the rule; an unknown number of poultry operations also would be covered.25

A number of agriculture stakeholders criticized the proposal. Many noted that agriculture as a

whole is responsible for only a small percentage of total GHGs and questioned why manure

management systems in particular were included in the proposal, since they are responsible for

less than 1% of total U.S. GHGs (see Table A-1). Other categories of agricultural sources, such as

livestock enteric fermentation and soil management, emit larger amounts of CH4 and N2O, but

were not included in the proposal. EPA explained that the proposal did not include reporting by

the other agriculture categories such as field burning of agricultural residues because, for those

sources, there are no direct GHG emission measurement methods available except for expensive

and complex equipment. Using emissions estimates for such sources, instead of direct

measurement, would have a high degree of uncertainty and likely would burden a large number of

small emitters, EPA said. Some who commented on the proposal said that similar concerns—

about a lack of accurate measurement methods and the costly burden of compliance with only

very small benefits—apply equally to reporting by manure management systems.

The EPA Administrator signed the final reporting rule on September 22, 2009.26 As in the

proposal, the final rule applies to manure management facilities with the same reporting threshold

of 25,000 metric tpy of CO2 equivalent of GHGs, but not to other agricultural sources or

agricultural land uses. In response to comments about the burden of the rule, EPA removed

manure sampling requirements and instead will allow facilities to use default values for

estimating emissions. EPA also made certain recalculations of affected facilities and now

estimates that approximately 107 livestock facilities will be subject to the reporting rule. The final

rule identifies population threshold levels below which facilities are not required to report

emissions, such as fewer than 29,300 beef cattle and fewer than 3,200 dairy cattle. These

thresholds would exclude 99% of beef feedlots, dairy farms, and others operations with manure

management systems.27 Facilities subject to the rule would report annually beginning in January

2011. However, as discussed below, in passing EPA’s FY2010 appropriations legislation (P.L.

111-88), Congress included bill language barring EPA from using funds under that act to

implement mandatory GHG reporting by manure management facilities.

Congressional Interest

The 111th Congress showed interest in several aspects of issues concerning agriculture and GHGs,

acting mainly to exempt or relieve agriculture from potential regulation of sources’ GHG

emissions.

U.S. Environmental Protection Agency, “Mandatory Reporting of Greenhouse Gases; Proposed Rule,” 74 Federal

U.S. Environmental Protection Agency, “Mandatory Reporting of Greenhouse Gases,” 74 Federal Register 5626056519, October 30, 2009.

U.S. Environmental Protection Agency, Office of Atmospheric Programs, Climate Change Division, Technical

Support Document for Manure Management Systems: Proposed Rule for Mandatory Reporting of Greenhouse Gases,

February 4, 2009, p. 6.

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Agriculture and Greenhouse Gases

First, legislation was introduced in the 111th Congress in response to concerns raised by EPA’s

July 2008 ANPR that the agency might require CAA permits for GHG emissions from

agriculture, which some groups characterized as a “cow tax proposal.” The legislation, S. 527 and

H.R. 1426, would have amended the Clean Air Act to mandate that no Title V permit be issued for

controlling carbon dioxide, nitrogen oxide, water vapor, or methane emissions “resulting from

biological processes associated with livestock production.” In addition, in the FY2010

appropriations bill for EPA (P.L. 111-88), Congress included a provision similar to the prohibitory

language of S. 527 and H.R. 1426. As adopted, the measure prohibits EPA from using funds under

the act to promulgate or implement any rule requiring the issuance of CAA Title V permits for

GHG emissions associated with livestock production.

Second, also in final action on P.L. 111-88, Congress blocked EPA from using funds in the bill to

implement any rule that would require mandatory reporting of GHG emissions from manure

management operations. This bill language applies to manure management systems of all sizes,

not just to those that emit more than 25,000 metric tons of CO2 equivalent per year, as contained

in EPA’s mandatory reporting rule. As noted previously, EPA’s rule excludes reporting by 99% of

farms with manure management systems; P.L. 111-88 excluded the other 1% of operations.

Third, the 111th Congress debated comprehensive climate change bills and in that context

considered whether or how to include agriculture and other sources of GHGs in the legislation. In

July 2009, the House passed the American Clean Energy and Security Act of 2009 (H.R. 2454),

legislation that covers clean energy, energy efficiency, reducing global warming pollution,

transitioning to a clean energy economy, and agriculture and forestry related offsets. The complex

and controversial legislation reflected compromises on various issues, including a number of

negotiated changes sought by agriculture interests.28 A key feature of the House-passed bill was

an economy-wide cap-and-trade system designed to reduce GHG emissions from covered entities.

As passed, the legislation excluded any agricultural enterprise or any small business enterprise

that emits less than 25,000 tons of CO2 equivalent of GHG emissions per year. Animal agriculture

sources were excluded entirely from the definition of “covered entities” in H.R. 2454, because of

their de minimis impact on the climate; thus, they would not have been subject to the cap or other

mandatory provisions of the bill.29

A key feature of H.R. 2454, as passed by the House, was the creation of a carbon offset provision

for agriculture. The so-called “Peterson Amendment” was added to H.R. 2454 just prior to the

floor debate, following negotiations between the Chairmen of the House Energy and Commerce

Committee and the House Agriculture Committee. Among other provisions, the Peterson

Amendment allowed for certain agricultural and forestry activities to become eligible to

participate in a carbon offset program. Offsets (emission reductions from non-covered sources)

could be purchased by covered entities and used to meet their compliance obligations. Thus, the

agricultural and forestry sectors could earn income for any emission reductions that it undertakes,

provided that the reductions are measurable and verifiable. The legislation also would have

established the offset program under USDA (rather than EPA), a key difference sought by

agriculture stakeholders.30

“Climate Bill Slated for House Vote June 26; Waxman, Peterson Announce Deal on Offsets,” Daily Environment

Report, June 26, 2009, p. A-11.

For information, see CRS Report R40643, Greenhouse Gas Legislation: Summary and Analysis of H.R. 2454 as

Passed by the House of Representatives, coordinated by (name redacted) and (name redacted).

For additional information, see CRS Report R40994, Agriculture and Forestry Provisions in Climate Legislation in

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Agriculture and Greenhouse Gases

Comprehensive climate change legislation was reported from the Senate Environment and Public

Works Committee in February 2010 (S. 1733, the Clean Energy Jobs and American Power Act).

Regarding agriculture, this bill was similar to H.R. 2454 in that it used the same emissions

threshold (25,000 metric tons of CO2 equivalent per year) applicable to the cap-and-trade and

other mandatory provisions and would exclude animal agriculture from the definition of “covered

entities.” Like H.R. 2454, S. 1733 would have allowed for agriculture and forestry offsets as part

of a cap-and-trade scheme. Also in the Senate, the Clean Energy Partnerships Act of 2009 (S.

2729) was introduced by Senator Stabenow shortly after the Senate Environment and Public

Works Committee completed work on S. 1733. This bill (often referred to as the “Stabenow

Amendment”) would have expanded the agricultural and forestry carbon offset provisions in the

comprehensive climate bills (e.g., S. 1733) and also would have allowed for certain other

provisions benefitting U.S. farmers and landowners.

Agricultural Conservation Practices and GHGs

Some degree of GHG emissions reduction from agricultural activities can be achieved with

existing conservation and land management practices, which also conserve and improve the

quality of soil, water, air, energy, and plant and animal life.31 Thus, in addition to or in place of

regulating agricultural emissions, another policy option could be to promote various voluntary

on-farm practices—ranging from reduced tillage to prescribed grazing—that could mitigate

emissions. The effectiveness, complexity, cost, and break-even point of the conservation practice

varies based on the farm type, farm size, land management, and agricultural commodity, among

other factors. A list of selected conservation practices that can reduce agricultural GHG emissions

is displayed in Table 2.

Typically, conservation practices have been used for soil conservation and water quality

improvement, not climate change abatement or mitigation. However, recent investigations have

shown certain conservation practices can significantly reduce agriculturally based GHG

emissions. Ideal conservation practices that also could reduce GHG emissions are associated with

the primary agricultural sources of these emissions (described previously)—enteric fermentation,

manure management, and agricultural soil management—or more simply, croplands and

livestock. Conservation practices that fall under the domains of nutrient management, tillage

operations, field management, precision agriculture, manure management, and dietary

management will likely have the most influence on decreasing agricultural GHG emissions. A

combination of practices may be necessary in some cases to significantly reduce GHG emissions.

However, certain conservation practices may decrease a single GHG while simultaneously

increasing others.32

(...continued)

the 111th Congress, by (name redacted) and CRS Report RL34436,The Role of Offsets in a Greenhouse Gas Emissions

Cap-and-Trade Program: Potential Benefits and Concerns, by (name redacted).

Federally supported conservation practices for environmental improvement and agricultural productivity originated

with the Soil Conservation and Domestic Allotment Act (P.L. 74-46, 49 Stat. 163) in April 1935, establishing the Soil

Conservation Service (SCS) within the USDA. The USDA Natural Resources Conservation Service (NRCS, formally

SCS) currently maintains standards for more than 150 conservation practices. A conservation practice standard contains

information on why and where the practice is applied, and sets forth the minimum quality criteria that must be met

during the application of that practice in order for it to achieve its intended purpose(s).

For example, restoring a wetland would sequester CO2, but could also release CH4.

Congressional Research Service

Agriculture and Greenhouse Gases

Depending on the agricultural source of GHG emissions, different conservation practices would

likely need to be used to obtain desired reductions. For instance, GHG control strategies for

cropland differ from those used for livestock. Cropland GHG emissions generally are distributed

over a vast area of land. Land management practices, sometimes referred to as “non-structural

practices,” work well to reduce GHG emissions from cropland.33 On the other hand, livestock

GHG emissions may be widely dispersed (emissions originate from a herd of cattle grazing) or

may emanate from a point-source (emissions originate from the manure handling system). A

mixture of feed management, nonstructural practices, and structural practices may be used to

reduce livestock GHG emissions.

In addition to reducing GHG emissions directly, some conservation practices provide another

climate change benefit: carbon sequestration (storage), which takes carbon out of the atmosphere.

Wetland restoration is a prime example of a conservation practice that sequesters carbon by reestablishing a sustainable ecosystem that provides a relatively greater degree of permanence in

CO2 sequestration than some other practices.34

Strategies, technologies, and practices to reduce CH4 and N2O emissions at the farm level are not

mandated by federal policies. As discussed further below, current federal policies are voluntary

and offer incentives for reducing GHG emissions. Absent mandates or increased incentives,

financial and monitoring challenges have stalled large-scale adoption of certain practices and

technologies. For example, CH4 emitted from a dairy farm via enteric fermentation (i.e.,

digestion) and manure management can be reduced by feeding dairy cows a high-quality forage

and using an anaerobic digestion system to capture methane from the manure. However, the high

cost of anaerobic digestion systems is a significant barrier to their widespread use for methane

capture.35 Similarly, N2O emitted from corn fields due to nutrient and soil management efforts

(e.g., fertilization and tillage) can be reduced with efficient application of fertilizer and

conservation tillage, but costs of adopting appropriate technologies and practices can be

prohibitive. Overall, problems of quantifying, monitoring, and verifying emission reduction or

carbon storage may make it impracticable to include many agricultural activities in some GHG

reduction programs, such as trading, because they might not meet credible standards.36

Examples of non-structural practices include crop residue management, nutrient management, and precision

agriculture.

As noted previously, there is ongoing debate about the permanence, or duration, of many carbon sequestration

practices, depending on the practice itself and such site-specific factors as location, climate and land condition. For

information, see CRS Report RS22964, Measuring and Monitoring Carbon in the Agricultural and Forestry Sectors,

by (name redacted) and (name redacted).

For more information on challenges to widespread implementation of anaerobic digestion systems, including the

difficulty of quantifying their benefits, see CRS Report R40667, Anaerobic Digestion: Greenhouse Gas Emission

Reduction and Energy Generation, by (name redacted).

For information, see CRS Report RS22964, Measuring and Monitoring Carbon in the Agricultural and Forestry

Sectors, by (name redacted) and (name redacted).

Congressional Research Service

Agriculture and Greenhouse Gases

Table 2. Conservation Practices and GHGs

Practice

GHGs Affected