Measuring Dairy Cows' Gas Emissions

A University of California researcher is trying to measure the amount of gas cows release into the air. He says his findings are not only controversial, but are being misinterpreted. Tamara Keith of member station KPCC reports.

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If you're passing through California's Central Valley farm country this summer, you might notice something unusual--four large, white biodomes rising from the flat landscape. What's more unusual is what's inside these bubbles--24 cows and some curious research, a study on just how much wind dairy cows pass each day. Member station KPCC's Tamara Keith spent the day with the scientist behind the study. He says his findings are not only controversial but are also being misinterpreted.

TAMARA KEITH reporting:

His work has been called `fart science,' but UC Davis researcher Frank Mitloehner fails to see the humor.

Dr. FRANK MITLOEHNER (UC Davis): Even though I understand that people find it cute to put cows in a bubble because the first thing they think about is, you know, `Oh, I wonder what kind of gas come out off a cow.' But this is not what we are really after. We are after, you know, where within the dairy do emissions come from, and how can we then address mitigating them.

KEITH: It is a serious issue. The smog problem in California's agriculture-rich San Joaquin Valley ranks among the worst in the country. And local air quality regulators say the region's 2.5 million dairy cows are the number-one source for volatile organic compounds, a key ingredient in smog. German-born Frank Mitloehner isn't so sure.

Dr. MITLOEHNER: People naturally wonder how can this be that a dairy produces so much more of these smog-forming gases than trucks and cars? And that's one of the reasons why we do research, because we want to find out is this true, and what kind of gases are emitted, and where are they emitted from?

(Soundbite of gate closing)

KEITH: To figure this out, Mitloehner's putting cows in airtight bubbles. There are four of these bubbles on his experimental farm. They're 70 feet long and 40 feet wide.

Dr. MITLOEHNER: Now we're going inside, and we'll see six cows and whatever they do.

KEITH: What they do is mosey up to check out the visitors. Then the black-and-white Holsteins promptly go back to doing what cows do a lot of, eating and excreting.

(Soundbite of cow urinating and defecating)

KEITH: Cows release plenty of gas, but most of it is methane, which doesn't cause smog. Mitloehner is looking for trace amounts of other gases, for example, purple acetates, which combine with other compounds in the air and do form smog. Mitloehner's research bubbles are carefully climate-controlled and decked out with sensitive air-monitoring equipment. Inside they look like typical drylot corrals. And the cows? They seem oblivious to the fact that they're being monitored.

Dr. MITLOEHNER: They eat a lot, and they rest, and they ruminate. And, you know, whatever they might do, we videotape them and we record the incoming and outgoing air.

KEITH: Mitloehner started putting cows in bubbles and environmental chambers last year, and he says he's already made some surprising and controversial discoveries. First, while substantial, the quantity of gas produced by dairies may not be as much as had been widely believed, he says. Secondly, the cows themselves are a significant source of smog-forming gases, more so than the fresh piles of waste they leave behind. Also a big surprise? Most of the gas emerges not from the cow's tailpipe but from the front end.

Dr. MITLOEHNER: These gases actually do come up--these gases that are produced in the stomach do come up, and we can measure them.

KEITH: The research is incomplete and hasn't been put through the scrutiny of peer review yet. Still, this week the San Joaquin Valley Air Pollution Control District used Mitloehner's early findings to come up with an estimate on how much smog-forming gas comes from the region's dairies, much to the chagrin of Mitloehner, who believes the district may have inflated his results.

Dr. MITLOEHNER: We are now starting to arrive at sound science, so that science-based regulation can be achieved at some point. But right now we are not there.

KEITH: The air district stands by its findings, which rely heavily on Mitloehner's research. Rick McVaigh is director of compliance for the Air District.

Mr. RICK McVAIGH (Compliance Director, San Joaquin Valley Air Pollution Control District): We believe it's the best available number at this time. We did a complete review of all available research, and we took the comments of all scientists, including Dr. Mitloehner, into consideration before we finalized our report.

KEITH: The air district now has to come up with regulations to cut dairy emissions. It has until the end of this year.

For NPR News, I'm Tamara Keith in Davis, California.

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