link to page 2 link to page 2 link to page 2 
January 9, 2020
Greenhouse Gas Emissions and Sinks in U.S. Agriculture
Agriculture and land-use activities have played a central
similar impact on global temperature over a specific
role in the broader debate on energy and climate policy
duration (100 years in the Inventory). This common
options in the U.S. and abroad. Although most federal
measurement can help compare the magnitudes of various
legislative proposals to reduce net U.S. greenhouse gas
GHG sources and sinks.
(GHG) emissions would not require reductions in the
The Inventory presents GHG estimates for two types of
agriculture sector, some would incentivize voluntary
sector classifications. One classification follows
actions. For example, legislation considered by a previous
international standards. Every country preparing its national
Congress would have established a separate carbon offset
inventory considers the same GHG sources and sinks for
program, with tradeable credits, for domestic agriculture
the same standard sectors. These include an agriculture
and forestry practices that reduce or sequester (store)
sector and a land-use, land-use change and forestry
carbon. Some proposed carbon tax legislation would
(LULUCF) sector. The Inventory also reports estimates for
finance activities in the agriculture sector that support these
several EPA-defined economic sectors, including
objectives with a portion of the new tax revenue.
agriculture, transportation, electric power, industry,
Agriculture is both a source and a sink of GHGs (Figure 1).
commercial, and residential. Under this format, the
Sources generate GHG emissions that are released into the
agriculture sector includes emissions from fuel-combustion
atmosphere and contribute to global climate change. Sinks
by farm equipment (e.g., tractors) as well as the emission
remove carbon dioxide (CO2) from the atmosphere and
sources already accounted for in the international standard
sequester carbon through physical or biological processes.
sector for agriculture. This document focuses on the
Agricultural emissions include many GHGs of interest to
emissions from the agriculture sector, as defined by EPA,
policymakers: CO2, methane (CH4), and nitrous oxide
and the most recent data available (from 2017).
(N2O). Agricultural sinks remove CO2 through
Agricultural GHG Emissions
photosynthesis and store carbon in plants and soil. Despite
these sinks, U.S. agriculture is a net GHG source.
EPA reports that agriculture sector emissions totaled 582.1
MMTCO2-Eq. in 2017 (Table 1), equal to 9.0% of total
U.S. GHG Inventory
U.S. GHG emissions (Figure 2). This estimate is based on
Since the early 1990s, the U.S. Environmental Protection
certain assumptions and includes direct emissions from
Agency (EPA) has prepared an annual Inventory of U.S.
agricultural activities (see text below for major emissions
Greenhouse Gas Emissions and Sinks. Federal agencies,
sources in agriculture). It does not include:
including the U.S. Department of Agriculture (USDA),
Potentially offsetting agricultural sinks.
contribute data and analyses. The Inventory reports GHG
estimates by sector, source, and GHG type.
Forestry activities, which are accounted for in LULUCF.
The Inventory expresses GHG estimates in terms of CO
Emissions from generating the electricity that farms use.
2-
equivalents, aggregated to millions of metric tons
Emissions from activities in the food system more
(MMTCO2-Eq.). CO2-equivalents convert an amount of a
broadly, such as production of agricultural inputs and
GHG, such as N2O, to the amount of CO2 that could have a
post-harvest transportation and processing of foods.
https://crsreports.congress.gov
link to page 2 link to page 2 
Greenhouse Gas Emissions and Sinks in U.S. Agriculture
Figure 1. Greenhouse Gas Emissions and Sinks from Agricultural Activities
Source: CRS. Note: Enteric fermentation refers to digestive processes in ruminant animals, which result in GHG emissions.
stored and treated in systems that promote anaerobic
Figure 2. U.S. GHG Emissions, by Economic Sector
decomposition (e.g., lagoons, ponds, tanks, or pits).
Agricultural emissions were higher in 2017 compared with
1990 but were lower than in 2010 (Table 1).
Table 1. Agriculture and Related Source Emissions
Emissions by Gas (Activity)
1990
2000
2010
2017
Total, Agriculture Econ.
534.9
550.4
593.7
582.2
Sector
N2O (soil and manure mgmt.)
265.7
264.5
292.4
285.2
CH4 (enteric fermentation,
217.4
237.8
245.7
248.7
manure mgmt., rice cultivation)
CO2 (urea fertilization, liming)
7.1
7.5
8.6
8.2
CO2, CH4, and N2O (fuel use)
44.6
40.4
47.1
40.0
Total Ag. w/Electricity-
569.9
592.3
634.3
620.9
Related
CO2, N2O, SF6 (electricity-
35.1
41.9
40.6
38.7
related)
Tot. U.S. Emissions, All
6,371.0
7,232.0
6,938.6
6,456.7
Sectors
Source: CRS from EPA Inventory (emissions in MMTCO2-Eq.).
Agricultural GHG Sinks
On agricultural lands, carbon can enter the soil through
Source: CRS from EPA Inventory, 2017 data.
plant roots, litter, cover crops, harvest residues, and animal
Notes: Emissions, in MMTCO2-Eq., are presented in parentheses.
manure. This carbon can be stored, primarily as soil organic
matter (Figure 1). Other biological sinks derive from a
In 2017, three activity types accounted for 90% of U.S.
range of land-use and land-management activities, such as
agriculture (economic sector) emissions:
maintaining forested land, which primarily stores carbon in
above-ground biomass (e.g., trees). The Inventory accounts
1. Soil management (46%, 266.4 MMTCO2-Eq.). N2O
for U.S. GHG sinks in the LULUCF sector. LULUCF net
emissions from soils, associated with agricultural
sinks account for both emissions and sinks from land use
practices that disturb soils and increase oxidation,
and land-use change, thus reflecting net changes in stored
releasing emissions into the atmosphere. Associated
carbon. Federal agencies—including USDA and the
with fertilization, irrigation, drainage, cultivation and
Departments of Energy, Transportation, and Defense—
tillage, shifts in land use, and application and/or
contribute LULUCF data to the Inventory.
deposition of livestock manure and other organic
materials on cropland and other farmland soils.
EPA reports a LULUCF net sink of 714.1 MMTCO2-Eq.
2. Enteric fermentation (30%, 175.4 MMTCO
for 2017. The magnitude of this net sink is equivalent to
2-Eq.).
CH
about 11% of all U.S. GHG emissions. Most LULUCF
4 emissions from livestock occurring as part of
normal digestive process in ruminant animals during
sinks are associated with maintaining existing forested land
metabolism and digestion. Associated with feed
and converting land from other land uses to forested land.
nutrient content and efficiency of feed use by the
Agricultural lands account for a limited share of U.S.
animal.
carbon sequestration. In 2017, “cropland remaining
3. Manure management (14%, 80.4 MMTCO2-Eq.).
cropland” (10.3 MMTCO2-Eq.) accounted for about 1.4%
CH4 and N2O emissions associated with livestock and
of LULUCF net sinks, a decrease from about 5.0% in 1990.
poultry manure occurring from manure/waste that is
https://crsreports.congress.gov
Greenhouse Gas Emissions and Sinks in U.S. Agriculture
Practices That Counter GHG Emissions
into the atmosphere when manure is collected in uncovered
lagoons and can use the captured CH
Farming practices that sequester carbon or reduce GHG
4 for energy.
Anaerobic digesters installed to manage manure and
emissions could play a role in legislative proposals seeking
capture and use the CH
to reduce U.S. GHG emissions. One approach could
4 emissions are often part of non-
federal voluntary and compliance carbon offset programs.
involve establishing a carbon offset or carbon banking
program. Other options include regulations or tax
Scientific research continues to investigate agricultural
incentives. In general, converting industrial land to
practices to increase sinks and reduce emissions. Voluntary
agricultural use, or keeping land in agriculture, would
and state programs have applied and documented potential
sequester more carbon in the soil than would other types of
GHG emission reductions. Current research topics related
industrial, commercial, or residential land uses. For existing
to sinks include improving estimates of (1) carbon storage
agricultural land, practices to increase carbon sequestration
in soils and (2) the effects of different management
may include retiring or restoring land, converting it to
practices on carbon sequestration. Topics related to
forested land, using conservation tillage and other practices
reducing sources include improving livestock genetics and
that increase biomass retention in soils or reduce soil
feed efficiency and manure management technology.
disturbance, and installing vegetative windbreaks.
Practices in animal agriculture to reduce GHG emissions
Genevieve K. Croft, Analyst in Agricultural Policy
include improved feed efficiency and manure management.
IF11404
Some livestock feed can reduce CH4 emissions from enteric
fermentation and also increase productivity. Manure
management systems can reduce the CH4 that is released
Disclaimer
This document was prepared by the Congressional Research Service (CRS). CRS serves as nonpartisan shared staff to
congressional committees and Members of Congress. It operates solely at the behest of and under the direction of Congress.
Information in a CRS Report should not be relied upon for purposes other than public understanding of information that has
been provided by CRS to Members of Congress in connection with CRS’s institutional role. CRS Reports, as a work of the
United States Government, are not subject to copyright protection in the United States. Any CRS Report may be
reproduced and distributed in its entirety without permission from CRS. However, as a CRS Report may include
copyrighted images or material from a third party, you may need to obtain the permission of the copyright holder if you
wish to copy or otherwise use copyrighted material.
https://crsreports.congress.gov | IF11404 · VERSION 1 · NEW