Methane digester system

Installing anaerobic digesters is one way dairy farmers in California are trying to reduce methane emissions.

Methane has been viewed incorrectly when discussing the climate, according to findings published in a new white paper. While more potent than carbon dioxide, methane is a short-lived climate pollutant. It stays in the atmosphere for about 12 years before it's broken down and removed. Carbon dioxide remains in the atmosphere for centuries, with new emissions adding to those previously emitted.

“Methane, Cows and Climate Change: California Dairy’s Pathway to Climate Neutrality” addresses the issue. The new white paper was co-authored by Frank Mitloehner, Ermias Kebreab and Michael Boccadoro.

Mitloehner is a professor and air-quality specialist for the University of California Davis-Cooperative Extension and head of the university’s Clarity and Leadership for Environmental Awareness and Research Center. Ermias Kebreab is a professor and endowed chair in the animal-science department at UC-Davis, and Michael Boccadoro is the executive director of Dairy Cares, a coalition whose mission is to ensure the sustainability of California's dairy farms.

The main accounting method currently used for measuring impacts of greenhouse gases doesn’t describe how individual gases warm or cool the climate through time. That leads to misinterpretation of methane's role in warming the climate. It also ignores possible solutions that could offset greenhouse gases, according to the authors.

Given greater efficiencies as well as a decrease in the number of cows and total milk production in recent years, the amount of methane emitted by California dairies is less today than it was in 2008. More methane is being broken down than is being emitted into the atmosphere, the authors wrote.

The state’s dairy farmers are further reducing methane emissions by installing anaerobic digesters, compost pack barns and solid separators. Efforts to date will result in a 25-percent reduction of manure-related methane – less than 2013 levels – as projects are implemented in the next few years, according to the California Department of Food and Agriculture.

The California dairy industry’s life-cycle carbon footprint – per gallon of milk produced – is among the lowest of any region in the world, Kebreab said. Further reductions will be accelerated as methane-reduction projects are implemented and feed additives become widely available.

“For other dairy regions a critical first step will be to achieve similar levels of production efficiency – more milk with fewer cows – to begin stabilizing methane emissions and work toward climate neutrality," he said. "The impact of such an accomplishment would have profound global climate effects."

Visit and search for "Methane, Cows and Climate Change" for more information.

The Clarity and Leadership for Environmental Awareness and Research is based in the University of California-Davis's Department of Animal Science. The center is committed to research and science communication and bringing clarity to the relationship of animal agriculture, the environment and people's daily lives.