Researchers measure animals' true effect on greenhouse gases

By TIM HEARDEN
Capital Press

Researchers at the University of California-Davis are set to rebut a 2006 United Nations study that asserted that livestock operations are responsible for 18 percent of the world's greenhouse gases.

In a journal article due out Oct. 1, the research will demonstrate that American beef and dairy production accounts for a much lower percentage of the gases believed to cause global warming.

The study, titled "Clearing the Air: Livestock's Contribution to Climate Change," makes use of U.S. Environmental Protection Agency reports that agriculture as a whole emits only 5.8 percent of the nation's greenhouse gases, said Frank Mitloehner, a livestock air quality specialist who worked on the project.

In California, where about 20 percent of U.S. cows reside and produce some 280 million pounds of manure a day, state officials say only 5.4 percent of greenhouse gases come from agriculture, Mitloehner said.

Researchers have also found that livestock accounts for a far lower level of volatile organic compounds (VOCs), which combine with oxides of nitrogen to create smog, than had been previously thought.

"Cars produce way more smog-producing gases than cows or steers ever will," Mitloehner told a room full of cattle producers in Palo Cedro, Calif..

The UC-Davis study was funded by numerous organizations including the National Cattlemen's Beef Association, which was concerned about negative media coverage of beef following the UN's report, "Livestock's Long Shadow."

The UN asserted that on a worldwide scale, livestock creates more greenhouse gases such as carbon dioxide, methane, nitrous oxide and ozone than does transportation. Further, it said livestock causes 40 percent of all methane and 65 percent of all nitrous oxide.

Based on the study, news organizations have erroneously applied the percentages to livestock operations in the United States, and even to individual states, Mitloehner said. However, the EPA has found that livestock is responsible for less than 3 percent of America's global warming-related emissions, he said.

The U.S. has a very small amount of the world's livestock, agriculture and livestock-related greenhouse gases, and its transportation system is much more advanced than in many undeveloped countries, he said.

The U.N. lists the clear-cutting of forests for livestock production as the No. 1 contributor to livestock-related climate change, but the U.S. is growing its forest land, Mitloehner said.

To determine the actual emissions from cattle, UC-Davis' research team studied Holstein and Angus calves and cows of various sizes and measured all sorts of gases.

The study made use of the unique conditions of California's Central Valley, which creates a "perfect trough" to trap air pollution, Mitloehner said. The research was completed in late 2008 and its findings have been undergoing a peer review.

Among its discoveries was that the researchers found higher methane levels depending on what the animal was fed, on its metabolism and other factors, Mitloehner said. The "take-home message" when it comes to dairies was that lagoons are the smallest source of VOCs, while the biggest source on a dairy is silage, he said.

"That finding has completely changed the perception of dairies," he said. "Now, it's 'What can we do to manage the feed?' ... Silage will be the biggest area of research in the coming year."

Staff writer Tim Hearden is based in Shasta Lake. E-mail: thearden@capitalpress.com.