In California, Wet Manure Storage Emits More Methane
New research published in the Journal of Dairy Science suggests that wet storage of manure emissions were 1.7 to 3.5 times higher than manure stored dry on California dairies. The lagoon stored manure also had much higher methane emissions in summer than it did in winter.
“We attributed much of the difference in emissions between dairies to the proportion of manure stored in liquid form,” says Claudia Arndt, a postdoctoral fellow at the Tropical Agricultural Research and Higher Education Center in Costa Rica, who led the research. “This suggests that reducing the amount of manure stored in that manner, or the length of time manure is stored in liquid form, could significantly reduce methane emissions.”
“Until now, relatively little research has been done to measure and pinpoint specific sources of methane emissions at dairies in California,” says Michael Boccadoro, executive director of Dairy Cares.
The information is critical to understanding methane emissions from dairy farms in California because they are being expected to reduce such emissions 40% by 2030. It is estimated that methane emissions from dairy farms account for about 5% of California’s carbon footprint.
“This important work advances our understanding in two areas—how to accurately measure and estimate methane emissions from California, and how to control them,” says Josette Lewis, associate vice president of sustainable agriculture with the Environmental Defense Fund (EDF). EDF provided financial support for the study.
Adds Boccadoro: “It is important that we base our strategies on sound scientific measurements from California dairies, and not just on studies conducted in other states. This information is critical as the dairy community works with our partners, including EDF, the California Air Resources Board (CARB), the California Department of Food and Agriculture, and technology providers to reduce emissions in a cost-effective manner.”
Other study findings:
• Direct methane emissions from ruminating animals, such as cow digestive gases or burps, tend to remain steady year-round.
• Emissions from manure storage can be highly variable and weather dependent; they are three to six times higher in summer than in winter.
• Emissions differences between dairies appear to be linked to the amount of manure that is stored in anaerobic, or wet and airless, conditions.
For the complete Journal of Dairy Science study, click here. Other participants in the research included USDA’s Agricultural Research Service, Penn State University, University of California-Davis and Aerodyne Research, Inc.