Author:  Jena Wilson, UNL student in Biological Systems Engineering

Agriculture in the United States provides a significant contribution to greenhouse gases, accounting for 9% of total emissions (US EPA). Animal agriculture is a large component of agriculture and contributes to these emissions. Around the world, animal agriculture contributes 15-24% of total greenhouse gases in the atmosphere (Fiala, 2008). In beef production, both cow-calf operations and feedlots produce large amounts of these gases. By implementing simple changes in cattle’s diet, though, there are several ways to reduce the number of these greenhouse gas emissions.  

Greenhouse Gas Production and Cattle Contribution

Greenhouse gases are defined by the Environmental Protection Agency (EPA) as gases that trap heat in the atmosphere. These gases allow sunlight to reach Earth unimpeded, but trap heat in the lower atmosphere. Many greenhouse gases occur naturally in the atmosphere, such as carbon dioxide, methane, and nitrous oxide. There are other gases that are synthetic, which are mostly fluorinated gases such as hydroflourocarbons and perfluorocarbons. 

Human activities that interfere with the carbon cycle, such as mining and deforestation, cause an increase in naturally occurring greenhouse gases. These greenhouse gas emissions can be quantified as a “carbon footprint”, or a sum of the total emissions being released by an operation or household. Each activity producing emissions is listed with the total amount of emissions in a carbon footprint. By identifying emission sources, changes can be made to processes to decrease the total emissions.  

Methane is a greenhouse gas that is produced by methanogens that are part of the cattle gastrointestinal microbiome, as a byproduct during microbial fermentation of feed in the rumen by methanogens. The gas is then released into the atmosphere primarily through cattle belching.

Diet and Greenhouse Gases

Diet is one of the biggest influencers on carbon emissions from cattle and the microbial population that produce methane within the rumen. The microbes involved in digesting carbohydrate-rich diets, such as grains, are different than those involved in digesting cellulose-rich diets, such as grass or hay. These different microbes produce different levels of methane.

Cattle fed high-grain, low-forage diets produce 42% more methane than those fed-low grain, high-forage diets (Boadi et al.,2004). Methane (CH4) is composed of carbon and hydrogen. The formulation of diet influences the carbon: nitrogen ratio of manure, which impacts the amount of methane released. Diets high in grain have higher levels of readily fermentable carbohydrates, which create methane to be released into the atmosphere. Grain type can also change the amount of methane emissions. During the finishing phase, cows fed a corn-based diet released less methane than cows fed a barley-based diet (Beauchemin and McGinn, 2005).

Incorporating fats into the diet increases the density of energy being consumed. By increasing energy consumed through fats, the diet can switch to being low grain, high forage without sacrificing energy and growth (Boadi et al., 2004). Cattle fed an increased forage diet in conjunction with added fats produce less methane, and therefore less greenhouse gases, than low forage and high grain diets. Fat supplements fed with high forage will require less grain, causing less methane to be produced and released. Fats can be toxic to methanogens that produce methane, having an inhibitory effect on methane production. Adding unsaturated fats in the diet is a good way to reduce the amount of methane.

There are some methane-reducing feed additives on the market currently that can be used as a supplement in cattle’s diets. These additives inhibit methanogens in the cattle’s rumen, reducing the amount of methane produced. As previously mentioned, unsaturated fats are a type of supplement that can be added to feed to reduce methane. There are also different synthetic chemicals that have been developed to have similar effects. There are also different natural compounds, such as seaweed and tannins, that can be added to feed to reduce methane. One certain type of seaweed has been found to reduce methane production by 80% in cattle (agric.wa.gov.au).

Next Steps

Finding ways to develop novel feed-additives will decrease the amount of methane produced by cattle. By developing new nutrition plans that incorporate increasing forage and fats, and decreasing grains such as barley, overall greenhouse gas emissions from cattle can be reduced. Incorporating these changes even in small amounts will make an overall large impact on greenhouse gas emissions from cattle operations. For additional information and next steps, see the Additional Readings below.

Additional Readings:

Methane (Anaerobic) Digesters  

Ways to Reduce Methane Production in Cattle 

Growing Cattle and Methane Emissions

Sources:

Beauchemin, K.A., McGinn, S.M. (2005). Methane emissions from feedlot cattle fed barley or corn diets. Journal of Animal Science, 83(3), 653-661.

Boadi, D. A., Wittenberg, K. M., Scott, S. L., Burton, D., Buckley, K., Small, J. A., & Ominski, K. H. (2004). Effect of low and high forage diet on enteric and manure pack greenhouse gas emissions from a feedlot. Canadian Journal of Animal Science,84(3), 445-453.

Fiala, N. (2008). Meeting the demand: An estimation of potential future greenhouse gas emissions from meat production. Ecological Economics,67(3), 412-419. doi:10.1016/j.ecolecon.2007.12.021

U.S. EPA Website 

Western Australia Department Primary Industries and Regional Development – Agriculture and Food