Forecast Emissions

EPA estimates 1997 U.S. methane emissions from livestock enteric fermentation at 34.1 MMTCE (6.0 Tg), which accounts for 19 percent of total U.S. methane emissions in 1997. EPA expects methane emissions from livestock enteric fermentation to increase through 2020 as livestock populations grow to meet domestic and international demand for U.S. livestock products. In 2010, methane emissions are forecasted to reach 36.6 MMTCE (6.4 Tg) as shown below in Exhibit 6-1. When estimating methane emissions from livestock enteric fermentation, EPA categorizes livestock populations, collects population data, and develops emission factors that account for the diversity of feed and animal character-istics throughout the U.S. Among livestock, cattle are examined more closely than other livestock species because they are responsible for the majority of U.S. livestock emissions, and significant variation exists in feed and animal characteristics for cattle. The greatest opportunity for reducing methane emissions from cattle is to increase pro-duction efficiency through improved management techniques. This chapter describes methane emissions from livestock enteric fermentation, the methodology used to estimate methane emissions, and the approaches underway to reduce emissions from cattle. Cost-effective management practices and techniques can be used to improve animal health and nutrition, increase production efficiency, and reduce methane emissions per unit of product. Based on assumptions about the use of these practices to improve productivity, EPA has developed three scenarios (low, middle, and high) of future emissions from livestock enteric fermentation. Unlike other chapters in this report, no cost estimates have yet been developed for methane reduc-tions from enteric fermentation