Assessment of Greenhouse Gas and Air Quality Benefits of Dairy Digester Installation In California

Quantifying the impact of dairy biogas digesters on air quality and greenhouse gas emissions.

University of California, Riverside


Riverside, CA

Recipient Location


Senate District


Assembly District



Amount Spent



Project Status

Project Update

The dairy digester was installed at the project site in 2021 and is in operation. Seasonal field surveys at the dairy site began early in 2022 and will be completed early in 2023. These surveys include not only measurements at different components of the study site, but also road surveys of other dairies in the region. The researchers have met with dairy industry leaders to update them on the status of research and plans.

The Issue

Dairy farms are the largest single source of methane emissions in California. Roughly half of those emissions, or a quarter of the statewide total, come from manure management, where methane is primarily generated from manure stored in anaerobic conditions, such as in lagoons. To mitigate these emissions, the state has invested more than $150 million dollars in the construction of dairy digesters. However, the effectiveness of these digesters in reducing methane emissions, and their impact on overall greenhouse gas emissions from dairy farms, has not been tested in the field.

Project Innovation

The researchers are taking advantage of a comprehensive set of seasonal measurements of methane, nitrous oxide, and ammonia emissions and their drivers at a dairy prior to an anaerobic digester being installed. By repeating these seasonal measurements following the installation and operation of the digester, the researchers will be able to quantify the impact of dairy digesters installation on dairy farm emissions at a well-characterized site. In addition, the researchers will measure the stable carbon isotope of methane emissions from dairy farms in the region from public roads will be made.

Project Goals

Measure reductions in methane and other pollutants with the use of dairy bio=digesters.

Project Benefits

There is a need for quantifying the benefits of using dairy digesters as a climate change mitigation strategy; consistent with the goals of Senate Bill 32 of 2006 and Executive Order
B-30-15. The project will provide the first detailed quantification of the changes in air quality and greenhouse gas emissions from a dairy with the installation of a biogas digester. The project will also evaluate the emissions associated with alternative manure management approaches. Confirmation of emission reductions with the use of dairy biogas digesters will confirm the benefits of using this technology. Finally, the project will test an innovative approach to differentiating between enteric and other methane emissions. If successful, this will improve the identification of specific sources of methane emissions at a dairy and enhance mitigation measures to address this.

Environmental & Public Health

Environmental Sustainability

Verifying the expected greenhouse gas emissions reductions has environmental benefits if leaks or shortcomings in the management system can be identified and mitigated. Further, the project will evaluate emissions of ammonia, an important precursor to the criteria air pollutant PM 2.5, and hence may benefit public health if ways to reduce ammonia emission are identified.

Key Project Members

Project Member

Francesca Hopkins



The Regents of the University of California on behalf of the Berkeley campus


Regents of the University of California, Davis


USDA Salinity Lab


Match Partners


University of California, Riverside


USDA Salinity Lab


Contact the Team