Cattle accounted by EPA for leading methane source

cattle-ghg-emissionsAgriculture just can’t get a break from the EPA. First, this past December and January, corn farmers and agribusiness alike were sending in comments to the Environmental Protection Agency to oppose EPA’s proposed changes in the Renewable Fuels Standard (RFS) that would affect corn-ethanol production and much of the Midwest’s economy.

Now, a draft report on greenhouse gas emissions from EPA reports that cattle primarily are “enteric fermentation,” which is the leading cause of methane emissions. Conversely, the report also shows that overall, agriculture produces a small percentage of total greenhouse gas emissions and provides significant sequestration of carbon.

According to a Drovers CattleNetwork article on the issue, the draft report attributes 25 percent of U.S. methane emissions to enteric fermentation. The next-leading source of methane emissions is natural gas systems, at 18 percent of the total. Although a small percentage of total greenhouse gas emissions, methane is considered 20 times more effective than CO2 at trapping heat in the atmosphere. The report shows methane emissions from ruminant livestock declining in recent years due to the decline in cattle numbers. The authors also note that feeding practices can influence emissions due to enteric fermentation, as high-quality, concentrated feeds such as grain-based rations reduce methane emissions relative to forage diets.

Agricultural overall is responsible for 8.1 percent of total U.S. greenhouse gas emissions, according to the report. Agricultural soil management is the largest source of emissions in the agricultural sector, in terms of carbon dioxide equivalents, as nitrous oxide (N2O) emissions from fertilizing activities are considered approximately 300 times more powerful than CO2 at trapping heat in the atmosphere. The report lists enteric fermentation as the second-largest agricultural source of greenhouse gas emissions, followed by manure management. 

The draft 1990-2012 Greenhouse Gas Emissions Inventory is now available for public comment. An EPA web page includes links to each section of the report, an executive summary and instructions for submitting comments.

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