Agriculture contributes significantly to greenhouse gas emissions  like methane, nitrous oxide, and carbon dioxide through various activities, including livestock digestion (methane), fertilizer application (nitrous oxide), and land use changes (carbon dioxide), impacting climate change. Here's a more detailed breakdown:
1. Livestock and Manure Management:
  • Methane (CH4): Livestock, particularly ruminants like cows, release methane during their digestive process (enteric fermentation) and through manure management. Methane is a potent greenhouse gas, trapping significantly more heat than carbon dioxide over a shorter period.
    Nitrous Oxide (N2O): Manure management practices, including storage and application to fields, can also lead to nitrous oxide emissions. Nitrous oxide is another potent greenhouse gas, with a global warming potential 300 times greater than carbon dioxide.
2. Agricultural Soils and Land Use:
  • Carbon Dioxide (CO2): Agricultural activities, including tilling the soil, burning crop residues, and converting natural ecosystems like forests to farmland, release stored carbon dioxide into the atmosphere.
    Soil Carbon Sequestration: Healthy soils can store significant amounts of carbon, but agricultural practices can disrupt this process, leading to carbon release.
    Rice Cultivation: Anaerobic conditions in rice paddies can lead to methane emissions.
 3. Fertilizers and Pesticides:
  • Nitrous Oxide (N2O):
    The use of synthetic nitrogen fertilizers can lead to nitrous oxide emissions, both during the manufacturing process and after application to the soil.
  • Fossil Fuel Use: The production and application of fertilizers and pesticides, as well as the operation of farm machinery, rely on fossil fuels, contributing to carbon dioxide emissions.
 4. Other Agricultural Emissions:
  • Burning of Crop Residues: Burning crop residues to clear fields can release significant amounts of carbon dioxide, methane, and other pollutants into the atmosphere.
    Fossil Fuel Combustion: The use of fossil fuels for heating, powering farm machinery, and transporting agricultural products contributes to carbon dioxide emissions.
    Deforestation: Clearing forests for agricultural land use releases large amounts of stored carbon dioxide into the atmosphere.
    Food Waste: Food rotting in landfills produces methane, a significant greenhouse gas. 
  • An Explanation of Units......A million metric tons of CO2: What does that mean? A million metric tons equals about 2.2 billion pounds, or 1 trillion grams. For comparison, a small car is likely to weigh a little more than 1 metric ton. Thus, a million metric tons are roughly the same mass as 1 million small cars.

    The U.S. GHG Inventory uses metric units for consistency and comparability with other countries. For reference, a metric ton is slightly more (approximately 10%) than a U.S. "short" ton.   https://www.epa.gov/energy/greenhouse-gas-equivalencies-calculator

    Convert emissions or energy data into concrete terms you can understand — such as the annual CO2 emissions of cars, househ olds, and power plants.......The Greenhouse Gas Equivalencies calculator allows you to convert emissions or energy data to the equivalent amount of carbon dioxide (CO2) emissions from using that amount. The calculator helps you translate abstract measurements into concrete terms you can understand, such as the annual emissions from cars, households, or power plants. This calculator may be useful in communicating your greenhouse gas reduction strategy, reduction targets, or other initiatives aimed at reducing greenhouse gas emissions.   https://www.epa.gov/energy/greenhouse-gas-equivalencies-calculator

AGRICULTURE-  UNITED STATES- EPA- Sources of Agriculture Sector Emissions

Agricultural activities — crop and livestock production — contribute to emissions in a variety of ways:
  • Various management practices on agricultural soils can lead to increased availability of nitrogen in the soil and result in emissions of nitrous oxide (N2O). Specific activities that contribute to N2O emissions from agricultural lands include the application of synthetic and organic fertilizers, the growth of nitrogen-fixing crops, the drainage of organic soils, and irrigation practices. Management of agricultural soils accounts for just over half of the greenhouse gas emissions from the Agriculture sector. Management of croplands and grasslands can also lead to emissions or sequestration of carbon dioxide (CO2). These emissions and removals are included under the Land Use, Land-Use Change, and Forestry sector.
  • Livestock, especially ruminants such as cattle, produce methane (CH4) as part of their normal digestive processes. This process is called enteric fermentation, and it represents over a quarter of the greenhouse gas emissions from the Agriculture sector.
  • The way in which manure from livestock is managed also contributes to CH4 and N2O emissions. Different manure treatment and storage methods affect how much of these greenhouse gases are produced. Manure management accounts for about 14% of the total greenhouse gas emissions from the Agriculture sector in the United States.
  • Smaller sources of agricultural emissions include CO2 from liming and urea application, CH4 from rice cultivation, and burning crop residues, which produces CH4 and N2O.

More information about emissions from agriculture can be found in the agriculture chapter in the Inventory of U.S. Greenhouse Gas Emissions and Sinks.

Agriculture Sector Emissions Trends- In 2022, direct greenhouse gas emissions from the agriculture sector accounted for 9.4% of total U.S. greenhouse gas emissions.
Greenhouse gas emissions from agriculture have increased by 8% since 1990. Agricultural soil management activities, such as application of synthetic and organic fertilizers, deposition of livestock manure, and growing nitrogen fixing plants, were the largest contributors to U.S. N2O emissions in 2022, accounting for 75% of total N2O emissions. Emissions from other agricultural sources have generally remained flat or changed by a relatively small amount since 1990.
An Explanation of Units- A million metric tons of CO2: What does that mean? A million metric tons equals about 2.2 billion pounds, or 1 trillion grams. For comparison, a small car is likely to weigh a little more than 1 metric ton. Thus, a million metric tons are roughly the same mass as 1 million small cars. The U.S. GHG Inventory uses metric units for consistency and comparability with other countries. For reference, a metric ton is slightly more (approximately 10%) than a U.S. "short" ton. Check out many other links......https://www.epa.gov/ghgemissions/agriculture-sector-emissions#sources