There are many strategies that farmers, businesses, and consumers can adopt to reduce greenhouse gases related to agriculture. First, farmers can replace fossil fuels such as gasoline and diesel with biofuels such as ethanol or biodiesel. Ethanol is a fuel alcohol that is produced by a fermentation process that uses yeast to convert the sugars found in plants into a combustible alcohol fuel. Ethanol can offset varying amounts of fossil fuel-generated carbon dioxide depending on the material used to produce the etha-nol. For example, Brazil, located in a tropical climate, can efficiently grow sugarcane. Sugarcane is an excellent source material for ethanol because the sugars in sugarcane can be easily converted into alcohol. In the United States, corn is the primary feedstock for ethanol. It is more costly to convert corn into sugar because the sugars are bound up in long starch molecules. These carbohydrates must be broken down in order to free up the sugars to be converted into alcohol. Therefore, researchers in the United States are working hard to discover ways to lower the costs of producing corn-based ethanol.
Researchers are also studying how to use other plant materials to produce fuel. Cellulosic ethanol is not yet a commercially-viable strategy, but many predict that it will be in the near future. Cellulose is the fibrous or "woody" part of many plants. For example, high concentrations of cellulose are found in the stock and leaves of corn. It would be beneficial to use this part of the corn for ethanol production because it is usually considered a waste product. Cellulosic ethanol would allow the corn kernel to be used for food rather than as a source material for ethanol. The challenge is that the sugars in the cellulose are tightly bound to starch molecules. Consequently a more expensive, enzyme-driven process must be used to convert the sugars into alcohol. Therefore, cellulosic ethanol is not commercially viable now, but many countries, including the United States, are spending hundreds of millions of dollars to discover how it could become a commercially viable fuel.
In addition to ethanol, research is being conducted on other plant-based alcohol fuels such as methanol and butanol. These fuels can also be produced from organic materials including grains and wood fibers. They are currently not commercially viable, but some researchers claim that they may be even better than ethanol as an alternative fuel. Diesel produced from plant material can also reduce greenhouse gases. Crops known as oilseeds, such as cottonseed, sunflower, soybeans, and canola, can serve as the source material to produce a diesel product that has performance characteristics similar to petroleum-derived diesel, without emitting the same volume of greenhouse gases.
Farmers can also modify their management practices so that farmland can serve as a sink to sequester carbon dioxide. For example, farmers can create buffers comprised of trees, shrubs, and natural grasses along rivers to prevent soil erosion and the loss of nutrients due to runoff. The Conservation Reserve Program in the United States pays farmers to take marginal cropland out of production as a way to reduce soil erosion.
Farmers can also create windbreaks near farmhouses and outbuildings. Windbreaks can create a microclimate that can moderate temperature extremes by blocking cold winds or providing shade on hot summer days. This can lower energy use and costs on farms. Windbreaks can also serve as carbon sinks, whereby trees and other plants absorb carbon dioxide. Farmers can also adopt conservation tillage strategies that leave part of the organic residue on the field after the harvest. This material slows runoff, thereby reducing soil erosion and nutrient loss. The decomposing material also replenishes the nutrients in the soil. All of these practices can reduce the energy used, and greenhouse gases produced, on the farm.
Livestock producers can reduce the impact of their operations by changing how they manage animal waste such as methane and manure. Some farmers are experimenting with anaerobic digesters that convert manure into more manageable waste solids that can be used as an organic fertilizer. The digester also creates methane as a byproduct, which can be captured and used as a renewable fuel.
Finally, some writers argue for a move away from large-scale industrial agriculture to place more emphasis on so-called civic agriculture as a way to slow global warming. Civic agriculture includes local food systems and organic foods. Local food systems reduce greenhouse gases by reducing transportation costs. Traditional food supply chains can stretch thousands of miles from the point of production to the place of consumption. Local food advocates suggest that food could be grown and consumed locally. Organic agriculture reduces the use of greenhouse gases because organic farmers cannot use petroleum-based herbicides or pesticides.
sEE ALso: Alternative Energy, Ethanol; Food Production; Methane Cycle.
BIBLIoGRAPHY. Consultative Group on International Agricultural Research, www.cgiar.org (cited September 2007); Thomas Lyson, Civic Agriculture: Reconnecting Farm, Food and Community (University Press of New England, 2004); Patrick Michaels and Robert Balling, The Satanic Gases: Clearing the Air about Global Warming (Cato Institute, 2000); National Sustainable Agriculture Information Service, www.attra.ncat.org (cited September 2007); Monte Oneal, et al., "Climate Change Impacts on Soil Erosion in Midwest United States with Changes in Crop Management," Catena (v.61, 2005); Organisation for Economic Co-operation and Development, www.oecd.org (cited
September 2007); Agnès Sinai, "China: The Sky Darkens," Le Monde Diplomatique (April 2006); U.S. Department of Agriculture, www.usda.gov (cited September 2007); U.S. Energy Information Administration, www.eia.doe.gov (cited September 2007); U.S. Environmental Protection Agency, www.epa.gov (cited September 2007); Matthew Wald and Alexei Barrionuevo, "The Energy Challenge: A Renewed Push for Ethanol, Without the Corn," New York Times (April 17, 2007); World Bank, www.worldbank.org (cited September 2007).
Christopher D. Merrett Western Illinois University
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