Researcher puts cows in a bubble to test emissions

The results could affect California's dairy industry if farmers have to comply with new air quality rules.

DAVIS, Calif. -- How much gas does a cow pass?

It's a serious question for California's dairy farmers, because the answer could cost them big money to comply with new state air quality regulations coming down the pike.

And it's certainly no laughing matter for Frank Mitloehner, whose work is quantifying bovine emissions. He doesn't appreciate that his research at the University of California has been laughed off by some people.

"We're not talking about flatulence," Mitloehner said.

There are more than 3 million cows in California, the vast majority living in the Central Valley, home to some of the most polluted air in the country. How much to blame the cows and how much to blame the cars for the bad air is no small concern.

Mitloehner's research has suggested that cows are responsible for far fewer of the compounds that contribute to smog, known as volatile organic compounds or VOCs, than previously thought, perhaps as little as half the amount.

That puts Mitloehner in the middle of a dispute coming to a head today, when the San Joaquin Valley Air Pollution Control District will announce its new emissions factor for cows -- the amount of VOCs, in pounds, that a cow releases each year. The number will eventually determine which dairies must apply for air quality permits and invest in mitigating air pollution equipment.

That is a multibillion-dollar decision, Mitloehner said. "It's not just a number."

The current emission factor per cow, based on a 1938 study, is 12.8 pounds of VOCs a year.

Groups on both sides of the issue have proposed higher and lower numbers. Mitloehner says he just wants to make sure the new number is based on science.

His solution was to recreate a cow's living conditions in a modern dairy and then seal it off. In one experiment, eight cows spend two days in an air-conditioned "bio-bubble," where they eat, chew and emit compounds while machines monitor the air.

The chief offender appears to be the ruminating process. After a cow eats, the food is briefly deposited in its bathtub-sized stomach. There it mixes with bacteria, begins to break down and produces methane, a greenhouse gas. About 20 minutes later, the food comes up again as cud. As the cow chews it, the methane is released into the air. The process also emits methanol and ethanol, both VOCs.

For some in the industry, the results indicate that dairy farmers who may be forced to mitigate pollution may be trying to fight nature.

"Is this something that we really want to do, try to regulate a living thing?" said J.P. Cativiela, a program coordinator for Dairy CARES, an industry-funded environmental group.

Cativiela said changing a cow's food may prove more effective than expensive technologies. He and other industry advocates are concerned that regulators will call for expanded use of methane digesters.

The digesters cover a dairy's lagoon of diluted waste, trap pollutants and create electricity. They also cost about $1 million a piece, and industry groups argue their effectiveness is unproven.

San Joaquin regulators say Mitloehner's research will be just one factor in the decision.

"The district's assessment is based on all of the science in total," said spokeswoman Jaime Holt. "It is not based on any one study, or any one process being measured."