Got methane?

Coase Colored GlassesLast year officials claimed that dairy farms are a big producer of the smog we get during the winter. This piece from teh Sacramento Bee suggests we need to keep asking, "But is it true?"

Cows get whiff of vindication in smog study
By Edie Lau -- Bee Science Writer
Published 2:15 am PST Thursday, January 27, 2005
Cows may not be quite the pollution-making machines they're purported to be, after all.
At least when it comes to smog-forming gases, typical California dairy cows emit only half the amount that state air regulators have been blaming on them, according to early results from a University of California, Davis, study.

Moreover, it's not cow manure that gives off so much of the unwanted gases, the research found - rather, it's cow burps.

"It has large implications," said Frank Mitloehner, the animal scientist and air-quality specialist who did the study. "It will change the way dairies are regulated in this state, I believe."

How much gas comes out of a cow is one of the most avant-garde questions in the field of air quality today. Thanks to a 2003 law, which removed age-old exemptions given to livestock operations, California is preparing for the first time to place controls on air pollution from farm animals.

On Wednesday, Mitloehner and other researchers on the topic of livestock emissions were called by the California Air Resources Board staff to Fresno to present results from their work.

Other studies address issues such as how much methane - a greenhouse gas - comes from dairies, ammonia and hydrogen sulfide levels on cattle feedlots, and emissions from chicken and turkey farms.

Mitloehner's study was funded by the U.S. Environmental Protection Agency and the San Joaquin Valley Air Pollution Control District. The findings are incomplete and have not yet been peer-reviewed. UC Davis publicized highlights in a news release.

Mitloehner's measurements show a cow produces about 6.4 pounds of volatile organic compounds per year. VOCs are ingredients in the development of ground-level ozone, a scourge of Central Valley air.

In their estimates, California air board staff have figured that a cow produces 12.8 pounds of VOCs a year - a flawed figure that was based upon a misinterpretation of a study done in 1938.

The consequences are huge. California is the nation's No. 1 dairy producer, with some 3 million cows. Most of those animals live in the San Joaquin Valley, a segment of the Central Valley reaching from Lodi to Bakersfield. Based on the faulty number, regulators projected that dairy cow waste would surpass passenger cars as a pollution source in the San Joaquin Valley by 2010.

Patrick Gaffney, a state air pollution specialist, said last year that he knew the cow number was shaky, but it was the only figure the agency had to work with, and he looked forward to receiving more reliable data.

On Wednesday, air board spokesman Jerry Martin acknowledged the importance of the new information. "This type of information will go a long way toward developing regulations that are fair both to the public and the farmers," he said.

Martin also noted that the data will have to be confirmed, and compared with results from other studies.

The ongoing UC Davis study measures the gaseous output from a sampling of Holsteins, which are the predominant milk-producing cows in the state. The animals are kept for three days in special chambers in which researchers can measure their emissions, whether from their mouths, hindquarters or waste.

Mitloehner said the most surprising finding so far is that when the cows are removed and their manure left behind, VOC levels drop to near background levels.

"At the time that the animals were chewing their cud, when they were belching, we saw the peaks (in gas emissions)," he said. "That indicates the gases ... are released when the animal ruminates."

The rumination "is going to be very tough to mitigate," said Michael Marsh, head of the trade association Western United Dairyman.

"I don't know what kind of device you might come up with," he said with a wry laugh. "Maybe some antacids."

Mitloehner's idea is to test the gas-producing capacity of various dairy cow diets to try to find something that minimizes VOCs without compromising milk production.