国会预算办公室-农业部门的温室气体排放（英）-2025.8_28页_5mb

Summary of Greenhouse Gas Emissions in the Agriculture Sector

Core Content

The agriculture sector is a significant contributor to greenhouse gas (GHG) emissions in the United States, responsible for about 10 percent of total GHG emissions, measured by their capacity to trap atmospheric heat. These emissions are primarily composed of nitrous oxide and methane, which are far more potent than carbon dioxide (CO₂) in terms of heat-trapping ability—270 times more potent for nitrous oxide and 28 times more potent for methane.

Main Components of Emissions

• Nitrous Oxide (N₂O): Mainly from crop fertilization and manure decomposition.
• Methane (CH₄): Primarily from livestock digestion (especially cattle) and manure storage.
• CO₂: From fuel combustion in agricultural machinery and facilities, accounting for about 8 percent of the sector's emissions.

Key Emissions Sources

• Crop Production: Accounts for about 50% of agricultural GHG emissions, with nitrous oxide being the main component due to fertilizer use.
• Livestock Operations: Accounts for the remaining 50% of agricultural emissions, with methane being the dominant gas.
• Cattle: The largest source of agricultural GHG emissions, contributing about 35% of total agricultural emissions in 2024.
• Fuel Combustion: A smaller but growing contributor, mainly from farm vehicles and equipment.

Trends in Emissions

• Agricultural GHG emissions have increased by about 7% since 1990, much less than the 50% increase in crop production and 75% increase in meat production.
• The increase in emissions is largely due to greater livestock numbers, especially dairy cattle, and increased manure storage practices.
• Emissions intensity (emissions per unit of production) has decreased by about 30% since 1990 due to technological advancements and improved productivity.

Geographic Distribution

• Agricultural emissions are widely dispersed across the U.S., though more concentrated in the Midwest.
• Methane emissions are most concentrated in areas with high livestock density, including the upper Midwest, California's Central Valley, and poultry and swine operations.
• Nitrous oxide emissions are concentrated in fertile agricultural regions such as the upper Midwest, Mississippi River basin, and Western U.S..

Projections

• The Congressional Budget Office (CBO) projects that agricultural GHG emissions will increase by about 0.25% annually over the coming decades.
• Future emissions will depend on demand for agricultural production and the adoption of emission-reducing technologies.
• The 2025 reconciliation act is not included in these projections, as it is not yet in effect.

Comparison with Other Sectors

• Agriculture is the fourth-largest GHG-emitting sector, after transportation, electric power, and the industrial sector.
• It accounts for almost half of all non-CO₂ emissions in the U.S., with nitrous oxide and methane being the primary contributors.
• Methane emissions from agriculture are about twice those of nitrous oxide.

Conclusion

The agriculture sector plays a crucial role in U.S. GHG emissions, particularly in non-CO₂ emissions. While emissions have grown modestly over the past few decades, they have not kept pace with the substantial increase in agricultural output. This is largely due to technological improvements, increased efficiency, and better management practices. Future emissions are expected to remain relatively stable or grow slightly, depending on production demand and technological development.