Agriculture's Greenhouse Gas Emissions
Farming and ranching account for about 10% of California's global warming gases when transportation of farm products to market are included with production practices.
Farming releases all three of the most common types of agricultural greenhouse gas emissions:
Major Greenhouse Gases from Agriculture
Carbon dioxide is the most prevalent greenhouse gas and therefore has the greatest impact. However, pound for pound, methane is 21 times more powerful than carbon dioxide in accelerating climate change. Nitrous oxide is 300 times more potent than carbon dioxide. Although there is not as much nitrous oxide being released into the atmosphere, the amount that is released has a disproportionate effect as does methane when compared to carbon dioxide.
Agricultural Sources of Greenhouse Gases
Most people know that power plants generating electricity from coal, oil and natural gas emit carbon dioxide, as do car and truck engines that burn gasoline or diesel. Farm tractors, trucks and other vehicles associated with agricultural operations also emit carbon dioxide. In addition, carbon dioxide can be emitted from the soil, particularly during tillage or other operations that expose soil to oxidation. Over time, soil carbon can be converted to carbon dioxide, reducing organic matter and adversely affecting soil properties. Scientists estimate that since California farmers first broke ground to plant crops, over half the organic matter in soil has been lost. The good news is that changing practices can potentially reverse this decline.
Agriculture accounts for 30% of the approximately 29 million metric tons of methane emitted from human-related activities in the U.S. (as of 1998), primarily from livestock. About 50% of agriculture's methane is given off by dairy cows through flatulence or burping. Most of the rest comes from the anaerobic decomposition (decomposition without air) of livestock wastes as well as other organic material. Rice growing is another source of methane, albeit a small one. It results from anaerobic conditions that exist in rice fields, mainly from decomposing rice straw that is now left in the wet fields (where it was once burned). Tractors also produce small quantities of methane from tailpipes. Most agricultural methane emissions can be mitigated with available practices and technologies.
Agriculture accounts for about 70% of nitrous oxide emissions in the U.S., primarily from the interaction of irrigation water and excess fertilizer during crop production, and secondarily from the production of nitrogen fertilizer. Nitrous oxide typically forms in the soil under wet conditions and when farmers apply more nitrogen fertilizer than crops naturally take in. Using nitrogen fertilizer and irrigation water more efficiently can reduce nitrous oxide emissions significantly.
Most of California's agricultural-generated greenhouse gases can be mitigated. Because they typically result from leakage and inefficiency, there is an economic advantage to reducing emissions, making the adoption of alternatives more likely. With California's aggressive greenhouse gas reduction targets and the scientific news about climate change worsening steadily, it is crucial to involve California farmers in capturing and reducing their greenhouse gas emissions.