Burping Cows: Researching How Farms can Help Cool the Planet

Chris Forest
Professor, Climate Dynamics, Penn State

This article is a part of Climate Action at Penn State, a blog highlighting climate solutions, research, and other efforts at Penn State. 

I hadn’t thought much about dairy farms since I was a kid. However, when I started working on a U.S. Department of Agriculture (USDA) research project that examined how to decrease greenhouse gases on dairy farms, I started thinking about cows and dairy farms a lot.

The USDA project involved multiple studies investigating best practices such as different methods of planting to reduce nitrous oxide emissions and as well as altering livestock feeds to decrease methane emissions. It focused on dairy farms in Wisconsin, New York, and Pennsylvania.

To estimate the overall effect of the best practices, one team took the information from the studies, and estimated how many tons of carbon dioxide, methane, and nitrous oxide could be decreased by using these best practices. The results were shown as a reduction of emissions per gallon of milk produced. For example, it was shown it was possible to reduce more methane and nitrous oxide combined per gallon of milk produced for a 150-cow farm than for a 1500-cow farm. This was a reduction of about 25 percent of the farm’s total standard emissions through these best practices.

cows in field


My role in the project was to use these estimates of decreased emissions and calculate how they would affect global mean temperature. By using climate models for very specific situations, we can understand if these practices would be effective or not to help limit global temperature changes.

After the farm teams estimated the overall reductions, we designed multiple scenarios to achieve the reductions by the year 2050 and extended them out to the year 2100. By comparing climate model results with a business-as-usual case, we found that if the agriculture sector as a whole (more than just the dairy sector) reduced its emissions by about 25 percent, we could see a reduction of temperature by 0.6 or 0.7 degrees Celsius compared to a standard case.

It was a much bigger number than we thought. Overall, the predicted temperatures decreased from the 5 degrees Celsius to nearly 4 degrees.

Why is this possible? What was the main cause of this decrease? Mainly, because methane and nitrous oxide are such potent greenhouse gases.

Of course, there is much more carbon dioxide in the atmosphere, so decreasing it is still the primary focus. However, if we can reduce methane, we can have a very strong and immediate effect on the trajectory of the warming of the planet.

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