Global greenhouse gas emissions from the agricultural sector totaled 4.69 billion tons of carbon dioxide (CO2) equivalent in 2010 , an increase of 13 percent over 1990 emissions. Global CO2 emissions from transport totaled 6.76 billion tons that year, and emissions from electricity and heat production reached 12.48 billion tons, according to Worldwatch Institute’s Vital Signs Online service.Following are key findings:

• Growth in agricultural production between 1990 and 2010 outpaced growth in emissions by a factor of 1.6, demonstrating increased energy efficiency in the agriculture sector.

• Three most common gases emitted in agriculture are nitrous oxide, CO2, and methane. Methane is generally produced when organic materials—such as crops, livestock feed, or manure—decompose anaerobically .
• Methane accounts for around 50 percent of total agricultural emissions.
• Enteric fermentation—the digestion of organic materials by livestock—is the largest source of methane emissions and of agricultural emissions overall.
• Carbon dioxide is released from soils when organic matter decomposes aerobically . The largest source of CO2 emissions within agriculture is the drainage and cultivation of “organic soils”—soils in wetlands, peatlands, bogs, or fens with high organic material. When these areas are drained for cultivation, organic matter within the soil decomposes at a rapid rate, releasing CO2. This process accounts for around 14 percent of total agricultural greenhouse gas emissions.

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