Abstract: The agriculture sector is a source of greenhouse gas (GHG) emissions, which many scientists agree are contributing to observed climate change. Agriculture is also a “sink” for sequestering carbon, which might offset GHG emissions by capturing and storing carbon in agricultural soils. The two key types of GHG emissions associated with agricultural activities are methane (CH4) and nitrous oxide (N2O). Agricultural sources of CH4 emissions mostly occur as part of the natural digestive process of animals and manure management at livestock operations; sources of N2O emissions are associated with soil management and fertilizer use on croplands. This report describes these emissions on a carbon-equivalent basis to illustrate agriculture’s contribution to total national GHG emissions and to contrast emissions against estimates of sequestered carbon.

Emissions from agricultural activities account for 6%-8% of all GHG emissions in the United States. Carbon captured and stored in U.S. agricultural soils partially offsets these emissions, sequestering about one-tenth of the emissions generated by the agriculture sector, but less than 1% of all U.S. emissions annually. Emissions and sinks discussed in this report are those associated with agricultural production only. Emissions associated with on-farm energy use or with food processing or distribution, and carbon uptake on forested lands or open areas that might be affiliated with the farming sector, are outside the scope of this report.

Most land management and farm conservation practices can help reduce GHG emissions and/or sequester carbon, including land retirement, conservation tillage, soil management, and manure and animal feed management, among other practices. Many of these practices are encouraged under most existing voluntary federal and state agricultural programs that provide cost-sharing and technical assistance to farmers, predominantly for other production or environmental purposes. However, uncertainties are associated with implementing these types of practices depending on site-specific conditions, the type of practice, how well it is implemented, the length of time a practice is undertaken, and available funding, among other factors. Despite these considerations, the potential to reduce emissions and sequester carbon on agricultural lands is reportedly much greater than current rates.

Congress is considering a range of climate change policy options, including GHG emission reduction programs that would either mandate or authorize a cap-and-trade program to reduce GHG emissions. In general, the current legislative proposals would not require emission reductions in the agriculture and forestry sectors. Many GHG proposals, however, would allow farmers and landowners to receive emissions allowances (or credits) and/or generate carbon offsets, which could be sold to facilities covered by a cap-and-trade program. In addition, the enacted 2008 farm bill includes provisions that could expand the scope of existing land-based conservation and other farm bill programs by providing incentives to encourage farmers and landowners to sequester carbon and reduce emissions associated with climate change, adopt energy efficiency measures, produce renewable energy feedstocks, and participate in markets for carbon storage.

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Topics: Agriculture, Climate Change