The U.S. Department of Agriculture has released the first detailed data on the amount of greenhouse gases commercial dairies emit in southern Idaho.
The yearlong study was conducted by scientists from the Kimberly-based USDA Northwest Irrigation and Research Laboratory.
"This is an area that needs more information," said April Leytem, the lead researcher on the project. "More data is needed as more people look into dairy farm regulation. A lot of research is driven by politics, so it makes sense we would be doing this now."
Dairy farm greenhouse gas emissions have not been measured to this degree before, Leytem said. The project was also started because of a growing concern over ammonia contamination, as well as an interest in studying how these gases contribute to climate change.
However, studying and gathering data on dairies is far from easy.
"It's very difficult to contain the emissions and measure it," she said. "You have to use high-tech equipment, use a lot of weather instrumentations, air movements and then link the two together with a computer model to analyze the data."
Researchers selected two dairy farms that each held 10,000 milk cows. Each facility had 20 open-lot pens, a manure solid separator, compost yard and wastewater storage pond.
Overall, the data showed that all 20,000 cows generated an average of 3,575 pounds of ammonia, 33,092 pounds of methane and 409 pounds of nitrous oxide every day.
The dairies' greenhouse gases emissions varied by the time of day and the season of the year. The data showed that greenhouse gases were the most potent from afternoon to mid-evening, due to the higher temperatures and increased wind activity.
The farms also were much more likely to produce more gases during the spring and summer months than in winter. During the spring, open lots produced almost 80 percent of the facilities' ammonia and methane emissions.
Whether these numbers should provoke any concern is still up in the air, Leytem said. The Environmental Protection Agency does not regulate dairy greenhouse gas emissions, and just the hint of any regulation has proven extremely controversial in the past.
"There hasn't been a line drawn by the EPA," Leytem said. "These numbers are trying to get at a baseline. The EPA has not given a level they consider to be good or bad."
While the study was mainly funded by the USDA, the Idaho Dairymen's Association also helped pay for parts of it.
"We strongly believe in science," said Bob Naerebout, the dairy association's executive director. "These kinds of studies are well-needed. The data was close to what we expected to find. The EPA conducted a study similar to this across the nation, and our numbers are coming close to their numbers."
Now that the data has been collected, the research team is moving forward to develop management practices for the dairy farms.
"The focus is on reducing emissions," Leytem said. "We're done with the basic monitoring. Now we can go back and ask, how can we use this information to lower emissions?"