Livestock Measures

Animal husbandry generates significant greenhouse gas (GHG) emissions in the form of non-CO2 gases such as methane and nitrous oxide. These gases are generated via enteric fermentation and the decomposition of manure.

Ruminant animals, such as cattle and sheep, are able to digest tough, cellulosic plants because they have two-part stomachs. Chewed plant matter is moved into the first stomach, where it is fermented by the action of microbes. Fermented plant material is then moved into the second stomach for digestion. Methane is a byproduct of microbial fermentation in the first stomach, which is belched by the animals and reaches the atmosphere. Measures to reduce enteric fermentation are still in development and are not widely used in commercial practice. The most common measure is altering the diet of ruminants, providing feed that results in less methane during fermentation. Experimental approaches include development of vaccines against the microbes that generate methane and genetically engineering cattle to require less feed (by increasing the efficiency of conversion of plant matter into animal tissue).

Manure from all livestock (not just ruminants) produces methane as it decomposes, particularly if it decomposes under anaerobic (oxygen-free) conditions. Larger agricultural operations, primarily for hogs and dairy cattle, often mix manure with water to form a slurry, which is stored until it is ready to be applied to fields as a fertilizer. The water creates an oxygen-free environment, so the decomposing manure produces methane. One of the best techniques for reducing GHG emissions from manure is the use of an anaerobic digester, a technology that recovers the methane produced during decomposition of the manure. Recovered methane can be used to provide energy. Switching from wet to dry manure management can also reduce methane production but might not be practical for some large livestock operations. Covering open-pit lagoons and flaring the captured methane is another option, and it offers the co-benefit of reduced odor.

Few policies have been used in real-world practice to control enteric fermentation emissions. However, a variety of policies have been used to encourage better manure management. For example, the U.S. Rural Energy for America Program (REAP) provides financial assistance to farmers implementing energy and efficiency projects, including anaerobic digesters. The energy produced by an anaerobic digester could create carbon credits or offsets under a carbon cap-and-trade program. Some farmers may choose to build an anaerobic digester as a means of complying with requirements that establish minimum standards for effluent discharge. Finally, farmers may be incentivized financially or required to cover open-pit lagoons, for example, for reasons of odor control.

There are also indirect emissions associated with livestock husbandry, including emissions from the growing of feed crops and the transportation of feed crops and livestock. Measures to reduce emissions from growing feed crops are included in the cropland management policy, while emissions related to transportation might be addressed via various transportation sector policies.

Reducing demand for animal products (for example, by substituting plant-based products) is another technique for reducing emissions from livestock operations. However, a reduction in demand for animal products is not a part of the livestock measures policy. Rather, it is govered by its own policy lever in the EPS.

For a more detailed discussion, see the applicable chapter of Designing Climate Solutions, our book on smart energy and climate policy design.