Agriculture could play a larger role in reducing greenhouse gas (GHG) emissions and lowering atmospheric carbon dioxide concentrations by sequestering more carbon. Farm operators can change production practices or land uses to increase the carbon stored in soil or vegetation. Other changes in production practices and land uses can result in reduced emissions of potent non-carbon GHG, such as methane and nitrous oxide. In addition, agriculture can produce biofuels, which can substitute for fossil fuels and thereby potentially reduce greenhouse gas emissions across multiple sectors. All of these actions are considered forms of mitigation.
Several agricultural best management practices could help reduce the sector’s GHG emissions. For example, improved fertilizer management (e.g., reducing application rates and using slow-release fertilizer or nitrification inhibitors) can reduce nitrous oxide emissions. Changes in livestock feed can reduce the amount of methane produced in the animals' digestive systems, and livestock facilities can use methane digesters to reduce methane emissions associated with manure management. Many of these practices come at a cost, either in the form of reduced productivity or increased input and management costs. By examining these costs and how they would be covered, ERS research can estimate the agricultural sector’s potential role in GHG mitigation efforts.
Agriculture and forestry play significant roles in reducing atmospheric greenhouse gas concentrations through carbon storage in soils and vegetation. Several recent studies indicate that farm, ranch, and forest lands could increase sequestration through practices such as conservation tillage, cover cropping, changes in species composition, and other forms of pasture and forest management.
Converting cropland and pasture to forest uses (afforestation) and management of forest land have the highest potential for sequestering carbon. For land remaining in crop and pasture uses, improved grazing management on rangeland and pasture, retirement of cropland (through the Conservation Reserve Program, for example), adoption of no till on cropland, and land use change from cropland to less intensive farmland uses can also sequester carbon. A large proportion of this additional sequestration may be achievable at lower cost than emissions reductions from other sectors.
For more information, see Conservation-Practice Adoption Rates Vary Widely by Crop and Region (EIB-147, December 2015) and the Amber Waves summary, "No-Till" Farming Is a Growing Practice (EIB-70, November 2010), The Use of Markets To Increase Private Investment in Environmental Stewardship (ERR-64, April 2008), Economics of Sequestering Carbon in the U.S. Agricultural Sector (TB-1909, April 2004), and the Amber Waves summary article.
Federal policy can provide incentives to farm operations to adopt practices that reduce on-farm GHG emissions. However, in some cases, producers may face tradeoffs between reduced greenhouse gas emissions and improved water quality when making decisions about manure and nutrient management. For example, open lagoons and other liquid containment facilities store manure that might otherwise contaminate water bodies, but in doing so create conditions for manure decomposition that releases methane. Further actions can be taken by producers to capture the methane gas emissions generated by manure decomposition. For more information, see Managing Manure To Improve Air and Water Quality (ERR-9, September 2005).
The use of methane digesters on dairy and hog farms captures methane produced during manure storage so that it is not released to the atmosphere. Anaerobic methane digesters—biogas recovery systems that burn methane from manure to generate electricity—have not been widely adopted in the United States because costs have exceeded benefits to operators. Producers can use the captured methane to generate electricity for use on the farm or for sale to electric utilities, where feasible, which reduces reliance on fossil fuels and provides an additional source of income.
A policy or program that pays producers for these emission reductions—through a carbon offset market or directly with payments—could increase the number of livestock producers who would profit from adopting a methane digester. ERS research shows that a relatively moderate carbon price of $13 per metric ton of carbon dioxide equivalent emissions could induce significantly more dairy and hog operations, particularly large ones, to adopt a methane digester, thereby substantially lowering emissions of greenhouse gases (see Climate Change Policy and the Adoption of Methane Digesters on Livestock Operations, ERR-111, February 2011).
Bioenergy refers both to biofuels, which are transportation or heating fuels such as ethanol and biodiesel that are derived from plant matter, and to biomass that is burned in a power plant to generate electricity. Bioenergy may play a role in addressing climate change because it can, in some circumstances, substitute for other energy sources such as gasoline or coal that are sources of carbon dioxide emissions.
Federal and State laws and volatile energy prices have created a domestic market for bioenergy crops. The Energy Independence and Security Act of 2007 required that the U.S. use 11.1 billion gallons of renewable fuels in 2009. This mandate increases to 36 billion gallons by 2022. Roughly half of the States have laws requiring a portion of the State's electricity to be generated from renewable sources, some of which could be plant-based sources. Mandates for renewable electricity are also being discussed at the Federal level.
The demand for bioenergy has implications for U.S. and world agricultural markets. ERS provides analysis of these market effects. The production of biomass may affect soil carbon storage, either positively or negatively, according to the same pathways described for carbon sequestration. ERS provides analysis of where and how bioenergy and related crops are grown, which helps policymakers and others determine their effects on the carbon balance.
ERS has approached bioenergy issues in several ways (see the ERS Bioenergy topic page):
- Monitoring the state of the agricultural system and rural communities
- Providing market analyses
- Developing projections of commodity supply, demand, and retail food prices
- Conducting indepth research on policy-relevant topics
For more information, see Increasing Feedstock Production for Biofuels: Economic Drivers, Environmental Implications, and the Role of Research , authored largely by ERS researchers and released by the interagency Biomass Research and Development Board. The report presents an economic assessment of feedstock production from agriculture and forestry sources and analyzes the likely greenhouse gas implications of various policy and economic scenarios. It concludes that farm-sector greenhouse gas emissions of increasing corn ethanol production from 12 to 15 billion gallons a year are likely to be modest. It also shows that a 50 percent increase in corn productivity can reduce greenhouse gas emissions associated with increasing biofuel production by 7.7 million metric tons (CO2 equivalent). This latter finding shows how increased commodity productivity acts as a kind of greenhouse gas mitigation strategy. Many uncertainties remain in this analysis, especially the possible indirect land use changes resulting from biofuel policy. ERS researchers reviewed the current state of the knowledge about biofuels and indirect land use change in Measuring the Indirect Land-Use Change Associated with Increased Biofuel Feedstock Production: A Review of Modeling Efforts: Report to Congress (AP-054, February 2011).
Energy Conservation and Generation
Agricultural producers, like other producers in the economy, use fossil fuels as part of the production process. Farmers can undertake energy conservation and efficiency improvements to reduce their use of these fuels. They can improve their operations' energy efficiency by installing new technology, purchasing new machinery, or using different production methods that can decrease fuel use. Farms can also reduce GHG emissions by switching to alternative fuels that emit fewer greenhouse gases or by generating low GHG emitting power on the farm. For example, farms can capture and burn methane gas or they can install wind or solar power generating facilities to either supply on-farm power or supply the electricity grid with renewable power supplies. See Agriculture’s Supply and Demand for Energy and Energy Products (EIB-112, May 2013) for more details on on-farm energy use and generation.
The Rural Energy for America Program provides funds to agricultural producers and rural small businesses to purchase and install renewable energy systems and make energy efficiency improvements.
Mitigation Policy Design
Federal policy can play an important role in influencing greenhouse gas emissions from agriculture by, for example, providing incentives for landowners to reduce emissions through various mitigation activities. In addition to programs aimed specifically at greenhouse gas mitigation (such as GHG cap and trade programs or renewable energy mandates), USDA’s conservation programs also influence agricultural GHG emissions and sequestrations through the farming practices they support. ERS research on the importance of conservation program designs on environmental outcomes can provide valuable insight into designing effective GHG mitigation policies and programs. Alternatively, several of the activities that count as mitigation have additional environmental benefits, such as providing wildlife habitat or reducing nonpoint water pollution. ERS conducts research on the economic value of these benefits, which could be used to provide additional incentive for GHG mitigation efforts.
Multiple ERS research reports have examined the importance of policy design in achieving environmental benefits in a cost-effective manner from USDA's conservation programs. This value may complement the value of carbon markets. An ERS report (see The Use of Markets To Increase Private Investment in Environmental Stewardship, ERR-64, September 2008) examines the environmental services farmers could provide, identifies impediments to market formation, and explores potential roles for government action. Case studies examined in the report include carbon markets, as well as water quality trading, wetland restoration, and recreation on Conservation Reserve Program lands.
Because many of the practices supported by conservation programs sequester carbon as well as providing other environmental benefits targeted by the current programs, insights from research on existing conservation programs can provide a strong foundation and "lessons learned" for considering the potential implications of alternative approaches to greenhouse gas mitigation policy design and how they interact with existing conservation programs. For example, the Conservation Reserve Program (CRP) retires environmentally sensitive cropland from production and pays farmers to plant conservation cover under 10- to 15-year contracts.
The CRP does not currently preclude participants from receiving additional payments for sequestering carbon. Therefore, a national cap-and-trade system for greenhouse gases that includes credits for agriculture could make participation in both a carbon market and the CRP more attractive. On the other hand, if "stacking" of credits is not allowed, carbon markets and conservation programs may compete for the same land. Thus, coordination between conservation programs and carbon markets is an important policy consideration.
ERS is using its knowledge about land markets, commodity markets, and domestic and international market to provide insight into effective GHG mitigation policy design, and the interaction between conservation and mitigation efforts. For more information, see Additionality in U.S. Agricultural Conservation and Regulatory Offset Programs (ERR-170, July 2014), Baselines in Environmental Markets: Tradeoffs Between Cost and Additionality (EB-18, February 2012), The Role of Agriculture in Reducing Greenhouse Gas Emissions (EB-15, September 2010), The Use Of Markets To Increase Private Investment in Environmental Stewardship (ERR-64, September 2008).
Other related ERS reports include: