Research Projects

Project at a Glance

Project Status: active

Title: Quanitifcation of the emission reduction benefits of mitigation strategies for dairy silage

Principal Investigator / Author(s): Mitloehner, Frank

Contractor: UC Davis

Contract Number: 11-325

Research Program Area: Emissions Monitoring & Control

Topic Areas: Agriculture

Research Summary:

Recent studies indicate that dairy silage (chopped plants preserved by fermentation) is likely a significant source of volatile organic compounds (VOC) and nitrogen oxides (NOx), both of which are ozone precursors. Out of the approximately 1,700 dairy farms in California, more than 80 percent are located in the San Joaquin Valley (SJV), which has been classified as an extreme ozone nonattainment area. More research is needed to better quantify both the total silage emissions and the various emission species. The proposed research expands upon previous flux chamber measurements (Schmidt, 2009), with additional measurements using Fourier Transform Infrared (FTIR) spectroscopy and wind tunnels. By using multiple sampling techniques, this research will significantly increase the quantity and quality of data available with a goal of publishing the results in a peer reviewed journal. The project further expands on past work by including emissions measurements through the entire silage management cycle, from the creation of the silage pile to the feeding process. The research will evaluate typical piles at typical dairies (i.e., dairies implementing commonly established measures such as standard chop-size and minimum pile density) and will also quantify reductions from less common practices (such as Ag-bags and feed additives) included as compliance options in the SJV Air Pollution Control District (SJV District) Rule 4570. One other mitigation strategy, water addition, will also be evaluated. The tasks were selected in consultation with the SJV District.

The SJV District currently estimates that silage accounts for at least 60 percent of total dairy VOC emissions. During a recent study on fermentation of alfalfa and corn silage, the Mitloehner research team found that NOx emissions from silage may be significant, a finding that is supported by previous studies (including Maw et al, 2001). Other studies (including Augusto et al, 2002) have proposed potential biochemical pathways for NOx formation. The evaluation of the emissions impact from various mitigation strategies will improve quantification of the benefits of the Rule 4570 as well as the overall emissions profile for dairies.


For questions regarding research reports, contact: Heather Choi at (916) 322-3893

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