ARB Research Seminar

This page updated December 1, 2016

Quanitification of the Emission Reduction Benefits of Mitigation Strategies for Dairy Silage

Photo of Frank Mitloehner, Ph.D.

Frank Mitloehner, Ph.D., Professor, Department of Animal Science, University of California, Davis.

December 01, 2016
Cal EPA Headquarters, 1001 "I" Street, Sacramento, CA

Research Project


Dairy silage (the preserved dairy feed through fermentation) has been identified as a significant source of volatile organic compounds (VOCs) which are ozone precursors, and thus may contribute to the extreme ozone nonattainment of the San Joaquin Valley (SJV) where 80% of California's 1,300 dairy farms are located.

This project monitored VOCs and NOx emissions throughout different phases of silage management at dairies, evaluated the mitigation potential of several silage management practices on VOCs recommended by the San Joaquin Valley Air Pollution Control District (SJVAPCD), and developed and validated a new VOC model simulating silage emissions from California dairies. The study indicated that storage of silage in Ag-Bag (a plastic bag manufactured exclusively for silage storage) rather than in conventional piles, removing silage from storage pile (defacing) by lateral- rather than perpendicular- cutting or using raking, and adding water to the feed material (also known as total mixed ration or TMR) resulted in lower emissions of VOCs. Storage of silage in Ag-Bag, however, did not lower NOx emissions compared to conventional piles. Adding microbial and chemical additives to silage even enhanced VOC emissions except for potassium sorbate fortified at 0.1% (wet silage).

A new VOC emission model was developed in this project and incorporated into a whole-farm modeling approach, which was adopted in evaluating the effect of different mitigation practices on VOC emissions. The simulation results indicated that most of the VOC emissions from silage would occur during feeding rather than the storage phase, and thus mitigation efforts should focus on feed lanes, not the exposed face of silage piles, at dairies. Further field studies are needed to verify this conclusion.

Speaker Biography

Frank Mitloehner, Ph.D., is a Professor and Air Quality Specialist in Cooperative Extension, Department of Animal Science, University of California, Davis. Dr. Mitloehner is an expert for agricultural air quality, livestock housing and husbandry. Overall, he conducts research that is directly relevant to understanding and mitigating of air emissions from livestock operations, as well as the implications of these emissions for the health and safety of farm workers and neighboring communities. Professor Mitloehner has served as chairman of a global United Nations Food and Agriculture Organization (FAO) partnership project to benchmark the environmental footprint of livestock production. Dr. Mitloehner served as workgroup member on the President's Council of Advisors on Science and Technology (PCAST) and as member on the National Academies of Science Institute of Medicine (IOM) committee. Professor Mitloehner received his MS degree in Animal Science and Agricultural Engineering from the University of Leipzig, Germany, and his PhD degree in Animal Science from Texas Technical University.

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