Posted: Thursday, June 03, 2010 11:00 AM
U.S. Agricultural Research Service
Each cow in a pasture can emit about 350 liters of methane per day, according to Agricultural Research Service estimates.
Scientists: Updated numbers will lead to more realistic impact assessment
By TIM HEARDEN
A key study due out later this year will shed much-needed light on the nature and scope of air emissions from dairies and other livestock operations.
Funded by members of the livestock industry and conducted by more than a half-dozen universities across the country, the National Air Emissions Monitoring Study will quantify methane and other pollutant levels at dairy, poultry and swine operations.
Monitoring work for the two-year, $14.6 million study has just been completed at some 50 sampling locations, and researchers are now modeling the data, said Frank Mitloehner, a University of California-Davis air quality specialist who spearheaded the project in California.
"I think that it's probably half a year from now that the first data will be finished," Mitloehner said. "It's extremely complex because we have continuous data for a two-year period for 50 locations, so we're talking about billions of data points, or at least millions. It's a large number."
There's one conclusion that Mitloehner can draw, however: Dairies in the West have fewer emissions than those back East, he said.
"The Easterners are closed barns because of the cold winters there, while the ones in the West are open with free stalls," he said. "Because they are open there's much more wind flow, and when you have more wind flow there's a dilution effect. Because of that dilution effect, we measure lower emissions here in the West."
The study was spurred by a 2003 National Academy of Science report that urged the U.S. Environmental Protection Agency and other entities to update how they measure emissions from animal-feeding operations, many of which had grown in size.
Joining Mitloehner in the study were scientists from Washington State, Purdue, Cornell, Iowa State, North Carolina State and Texas A&M universities and the University of Minnesota.
UC-Davis bioenvironmental engineering researcher Ruihong Zhang is helping Mitloehner with the California data, while Pius Ndegwa, a biological systems engineering expert, is heading WSU's effort.
The project was launched in 2007 as part of a consent agreement involving the National Chicken Council, National Pork Board, the National Milk Producers Federation and the National Egg Board.
Individual livestock producers paid fees to support the study. The fees were technically fines, Mitloehner said, which shielded the producers from air-quality lawsuits during the study. More than 26,000 monitoring agreements were signed, representing about 14,000 swine, dairy, egg-laying and broiler chicken farms, according to the EPA.
Through the study, the scientists aim to accurately assess emissions from livestock operations and compile a database for estimating emission rates, according to a summary of the project on Purdue University's website.
The EPA plans to use the data to improve its method for estimating emissions from individual animal-feeding operations, the agency explained in a news release.
Results from the study will come on the heels of a new report by the United Nations' Food and Agriculture Organization that showed the global dairy sector contributes just 2.7 percent of the world's greenhouse gases and that North American dairy farms have the world's lowest emissions.
The report, "Greenhouse Gas Emissions from the Dairy Sector," asserts the U.S. livestock industry has the least emissions of greenhouse gases per unit in the world and that its efficiency could be a model for the rest of the world.
Farmers and ranchers have been concerned about the potential fallout from the EPA's ruling in December that greenhouse gases pose a public health threat. An EPA analysis under the George W. Bush administration estimated that if greenhouse gases were regulated, cattle operations with as few as 50 head would be impacted.
Mitloehner said he doesn't know what regulations could look like as a result of the emissions study, but the study will give the government better data.
"They need to have some idea of what's being released," he said. "This will really help give them an impression of, 'Is it a big issue or not a big issue?'
"Currently they just don't have the information," he said. "I think it will be very important to them."
National Air Emissions Monitoring Study: https://engineering.purdue.edu/~odor/NAEMS/index.htm
U.S. Environmental Protection Agency NAEMS page: www.epa.gov/agriculture/airmonitoringstudy.html