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Updated October 6, 2022
Greenhouse Gas Emissions and Sinks in U.S. Agriculture
Agriculture and land-use activities continue to play a
aggregated to millions of metric tons (MMTCO2e). CO2-
central role in the broader debate about energy and climate
equivalents convert an amount of a GHG, such as N2O, to
policy options in the United States and abroad. Such
the amount of CO2 that could have a similar impact on
activities offer opportunities to remove greenhouse gases
global temperature over a specific duration (100 years in
(GHGs) from the atmosphere, potentially reducing the
the Inventory). This common measurement can help
nation’s net emissions: the metric of emissions targets for
compare the magnitudes of various GHG sources and sinks.
the Paris Agreement (PA), the binding international climate
The Inventory presents GHG estimates for two types of
change treaty. Pursuant to the PA, the Biden Administration
sector classifications, one of which follows international
released a Nationally Determined Contribution (NDC) in
standards. Every country preparing its national inventory
2021 specifying a new U.S. target of reducing net GHG
considers the same GHG sources and sinks for the same
emissions by 50%-52% below 2005 levels by 2030.
standard sectors. These include an agriculture sector and a
Most federal legislative proposals to reduce U.S. GHG
land-use, land-use change and forestry (LULUCF) sector.
emissions would not require reductions in agriculture.
The Inventory reports estimates for several EPA-defined
However, the recently enacted Inflation Reduction Act
economic sectors, including agriculture, transportation,
(P.L. 117-169) provides the U.S. Department of Agriculture
electricity, industry, commercial, and residential. Under this
(USDA) with funding for voluntary conservation programs
format, the agriculture sector includes emissions from fuel-
to reduce, capture, avoid, or sequester GHG emissions.
combustion by farm equipment (e.g., tractors) and the
emission sources accounted for in the international standard
Agriculture is both a source and a sink of GHGs (Figure 1).
sector for agriculture.
Sources generate GHG emissions that are released into the
atmosphere and contribute to global climate change. Sinks
Agricultural GHG Emissions
remove carbon dioxide (CO2) from the atmosphere and
EPA reports that agriculture sector emissions totaled 635.1
store carbon through physical or biological processes.
MMTCO
Agricultural emissions include many GHGs of interest to
2e in 2020 (Table 1), equal to 11% of total U.S.
GHG emissions (Figure 2). This estimate is based on
policymakers: CO2, methane (CH4), and nitrous oxide
certain assumptions and includes direct emissions from
(N2O). Agricultural sinks remove CO2 through
agricultural activities (see text below for major emissions
photosynthesis and store carbon in plants and soil. Despite
sources in agriculture). It does not include
these sinks, U.S. agriculture is a net GHG source. This In
Focus discusses emissions from the agriculture sector, as
Potentially offsetting agricultural sinks.
defined by the Environmental Protection Agency (EPA)
Forestry activities, which are accounted for in LULUCF.
and the most recent data available (from 2020).
Emissions from generating the electricity that farms use.
U.S. GHG Inventory
Since the 1990s, EPA has prepared an annual Inventory of
Emissions from activities in the food system more
U.S. GHG Emissions and Sinks. USDA and other federal
broadly, such as production of agricultural inputs and
agencies contribute data and analyses. The Inventory
post-harvest transportation and processing of foods.
reports GHG estimates by sector, source, and GHG type.
The Inventory presents GHG estimates as CO2-equivalents,
Figure 1. Examples of Greenhouse Gas Emission Sources and Sinks from Agricultural Activities
Source: CRS. (Enteric fermentation refers to digestive processes in ruminant animals, which result in GHG emissions.)
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Greenhouse Gas Emissions and Sinks in U.S. Agriculture
Figure 2. U.S. GHG Emissions, by Economic Sector
Agricultural GHG Sinks
On agricultural lands, carbon can enter the soil through
plant roots, litter, cover crops, harvest residues, and animal
manure. This carbon can be stored, primarily as soil organic
matter (Figure 1). Other carbon sinks derive from a range
of land-use and land-management activities, such as
maintaining forested land, which primarily stores carbon in
above-ground biomass (e.g., trees). LULUCF is the only
Inventory sector to include GHG sinks. Net sinks in the
LULUCF sector account for both emissions and sinks from
land use and land-use change. Federal agencies—including
USDA and the Departments of Energy, Transportation, and
Defense—contribute LULUCF data to the Inventory.
EPA reports a LULUCF net sink of 758.9 MMTCO2e for
2020. This amount is equivalent to about 13% of all U.S.
GHG emissions. Most LULUCF sinks are associated with
maintaining existing forested land and converting land from
other land uses to forested land. Agricultural lands account
for a limited share of U.S. carbon sequestration. In 2020,
“cropland remaining cropland” (23.3 MMTCO2e)
accounted for about 3% of LULUCF net sinks.
Practices That Reduce GHG Emissions
Source: CRS from EPA Inventory, 2020 data.
Farming practices that sequester carbon or reduce GHG
Notes: Emissions are presented in parentheses in MMTCO
emissions could play a role in legislation seeking to reduce
2e.
U.S. GHG emissions. One approach could involve
In 2020, three activity types accounted for 90% of U.S.
establishing a carbon offset or carbon banking program (see
agriculture sector emissions:
CRS Report R46956, Agriculture and Forestry Offsets in
Carbon Markets: Background and Selected Issues). Other
1. Soil management (50%, 316.2 MMTCO2e). N2O
options include regulations or tax incentives. In general,
emissions from soils, associated with agricultural
converting industrial land to agricultural use or keeping
practices that increase nitrogen availability, disturb
land in agriculture would sequester more carbon than would
soils, and increase oxidation (e.g., fertilization,
other land-use types. For existing agricultural land,
irrigation, drainage, cultivation, tillage, shifts in land
practices to increase carbon sequestration may include
use, and deposition of livestock manure on soils).
retiring or restoring land, converting it to forested land, and
2. Enteric fermentation (28%, 175.2 MMTCO2e). CH4
using conservation tillage and other practices that increase
emissions from livestock occurring as part of normal
biomass in soils. Maintaining these actions is a challenge;
digestive process in ruminant animals during
stored carbon may be released if practices change.
metabolism and digestion. Associated with feed nutrient
content and efficiency of feed use by the animal.
Practices in animal agriculture to reduce GHG emissions
include improved feed efficiency and manure management.
3. Manure management (13%, 79.2 MMTCO2e). CH4
Some livestock feed can reduce CH4 emissions from enteric
and N2O emissions associated with livestock and poultry
fermentation and increase productivity. Manure
manure occurring from manure/waste that is stored and
management systems can reduce the CH4 that is released
treated in systems that promote anaerobic
into the atmosphere when manure is collected in uncovered
decomposition (e.g., lagoons, ponds, tanks, pits).
lagoons and can use the captured CH4 as an energy source.
U.S. agriculture sector emissions were higher in 2020
Anaerobic digesters installed to manage manure and
despite a reduction in total U.S. emissions largely attributed
capture and use CH4 are often part of nonfederal voluntary
to impacts of the COVID-19 pandemic on travel and
and compliance carbon offset programs.
economic activity (Table 1).
Scientific research continues to investigate agricultural
Table 1. U.S. Agriculture, Related Source Emissions
practices that may increase sinks and reduce emissions.
Emissions by Gas (Activity)
1990
2005
2020
Voluntary and state programs have applied and illustrated
Total, Agriculture Economic Sector 596.8 626.3 635.1
potential GHG emission reductions. Current research topics
N
related to sinks include improving estimates of (1) carbon
2O (soil and manure management)
330.1
330.3
336.1
CH4 (enteric fermentation, manure
214.7
235.5
250.9
storage in soils and (2) the effects of different management
management, rice cultivation)
practices on carbon sequestration. Topics related to
CO2 (urea fertilization, liming)
7.1
7.9
7.7
reducing sources include improving manure management
CO
technology and livestock genetics and feed efficiency.
2, CH4, and N2O (fuel use)
44.9
44.6
40.4
(Note: This In Focus was originally authored by Genevieve
Total Agriculture w/Electricity
631.9 664.6 669.5
K. Croft, former CRS Specialist in Agricultural Policy.)
CO2, N2O, SF6 (electricity-related)
35.2
38.3
34.4
Total Emissions, All Sectors
6,453.5 7,434.8 5,981.4
Megan Stubbs, Specialist in Agricultural Conservation and
Natural Resources Policy
Source: CRS from EPA Inventory (emissions in MMTCO2e.).
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Greenhouse Gas Emissions and Sinks in U.S. Agriculture
IF11404
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