Cows and Climate Change:
Cattle CH₄ Emissions Mitigation in the United States

Emma Lisa Schipper

As the world turns to watch the events at the Third Conference of the Parties of the United Nations Framework Convention on Climate Change in December 1997, climate change is raising awareness also in the United States, the single largest emitter of greenhouse gases. The U.S. will be responsible for implementing mitigation strategies as a result of anticipated binding emissions reductions aimed at eventually meeting 1990 emissions levels. Carbon dioxide (CO₂) has the greatest impact on global warming of the greenhouse gases, but one methane (CH₄) molecule can absorb 21-25 times the radiative energy of one molecule of CO₂. For this reason, a small reduction in CH₄ emissions could have the same effect as a large reduction in CO₂. CH₄ emissions from cattle in the form of enteric fermentation and anaerobic decomposition of manure are responsible for 21 percent of anthropogenic CH₄ emissions in the U.S., and therefore form a substantial source of greenhouse gas emissions. This study examines the reduction potential of mitigation strategies for cattle CH₄ emissions in the U.S., and what impact this could have on domestic mitigation of greenhouse gases. The U. S. Environmental Protection Agency (EPA) has proposed technical, economic, and regulatory strategies that are expected to result in CH₄ emissions reductions. However, after close analysis of the options suggested, it does not appear as though the U.S. has the potential to reduce CH₄ emissions from cattle unless there is a substantial reduction in the size of the national cattle population. In addition, some reduction potentials have not been explained. An exploration of new options shows that while reduction of emissions may be possible with the implementation of strategies to change human demand for beef, in fact the only true reduction possibilities lie in recovering CH₄ from covered manure storage lagoons, or culling cattle herds. Although reducing CH₄ emissions from cattle should not be relied on as a significant option for greenhouse gas reduction in the U.S., looking internationally for opportunities for CH₄ reduction cannot be discounted. Finally, in depth studies such as this one should be done for all greenhouse gas sources and reduction strategies to identify the best areas for mitigating climate change.