Animal Science Faculty Do Cutting Edge Research

Bovine Bio-bubbles Help Quantify Air Emissions

Hoping to track down the real numbers on how much of what kinds of gases cows emit, Dr. Frank Mitloehner, a Cooperative Extension air quality specialist, has put cows in plastic bubbles and is measuring what comes out of them.

Last June, Dr. Mitloehner and his students—Andrea Schnitz, Wendi Jackson, and Kevin Eslinger—built four big airtight bio-bubbles on campus by covering 40 by 70 foot corrals with Quonset hut-type frames 15 feet high and then stretching white, high-tech plastic over them. Ten Holstein heifers or mature dry cows live in each one. Fresh air blows in and the animals consume carefully measured feed and water. All air that escapes is measured for gases and dust. Temperature, humidity, pressure and air volume are being measured as well.

As Gary Anderson, department chair, points out, “This project demonstrates how research in the Department of Animal Science changes with needs of our stakeholders. For example, over the past decade or two research needs for the dairy industry have shifted from how to produce more milk to how to do it in an environmentally sustainable system. In response, the department recruited as a Cooperative Extension specialist an agricultural engineer who has established a research program to address air quality issues confronting dairymen and feedlots.”

Andrea Schnitz, graduate student, sprays urease inhibitor to the pen surface, a once-a-week treatments to block the reaction of urea from the urine mixing with urease in the feces. This mixing contributes to ammonia emissions.

What prompted Dr. Mitloehner’s unusual research project is concern over air quality in the San Joaquin Valley, which ranks among the worst in the country. The valley has a high concentration of dairy farms that add dust and air emissions to the atmosphere. California has about 1.6 million cows producing milk and a similar number of dry cows and heifers. These animals are blamed for much of the bad air in places like the San Joaquin Valley, but no one knows exactly how much ammonia, fine particulate dust and volatile organic compounds a cow creates, from one end or the other.

Good scientific data upon which to base governmental regulations are hard to find. In 1997, the San Joaquin Valley Air Pollution Control District used a flawed value to create an emissions limit for volatile gases produced by cows. Volatile organic compounds are precursors in the formation of ozone, the pollutant that most plagues Valley air. Dr. Mitloehner and others tracked down the origin of the mistake. A 1938 study on the nutritional physiology of ruminants determined that a mature cow emits 160 pounds of methane a year. Then in 1978, a scientist misquoted the number as the total organic gases produced, and other researchers perpetuated the error by citing that paper. To add to the confusion, methane is not reactive, although it is an organic gas (and doesn’t form ozone) .

“The emission factor that determines dairy emissions today is derived from a study that is not only critically outdated but that did not measure volatile organic compounds at all,” Mitloehner says. “Nonetheless, this is how air-quality regulators are determining who requires a permit until better data are available.” This situation illustrates how detailed data about the dairy industry’s role in air quality are badly needed to give the industry and state agencies current information for regulatory decisions.

Mitloehner’s $600,000 study is funded by the State Water Resources Control Board and Merced County, with additional matching funds from UC Davis.

His team of graduate students and staff researchers is investigating several methods to reduce dust, ammonia and volatile organic compounds. Rice straw bedding, for instance, may reduce ammonia emissions by mechanically separating urine from feces. It also keeps livestock pens drier in winter and reduces dust in summer, meanwhile creating a new use for an agricultural waste product.

Dr. Mitloehner knows dairy air. He studied ways to reduce stockyard emissions in Texas before becoming a UC Davis Extension Specialist in 2002. Last spring, he worked with more than 800 dairy producers in air-quality workshops throughout the San Joaquin Valley, educating them on air quality issues, helping them conduct on-farm assessments and walking them through the newly mandated permitting process. This educational effort is part of the California Dairy Quality Assurance Program, a collaborative program that includes industry, state regulators, environmental groups and the University of California. And, the research ongoing in the Department of Animal Sciences should yield solid data for use in future regulatory decisions.