Anaerobic Digestion Information

Biogas recovery systems are sometimes known as anaerobic digesters or "biodigesters" because they use a process called anaerobic digestion. During anaerobic digestion, bacteria break down waste in an oxygen-free environment. One of the natural products of anaerobic digestion is biogas, which typically contains between 60 to 70 percent methane, 30 to 40 percent carbon dioxide, and trace amounts of other gases.  Applications of anaerobic digestion for biogas capture include wastewater treatment plants, Dairies, and at organic waste processing facilities.

Biogas can be used to produce electricity using engines or fuel cells, or it can be converted to transportation fuel or “biomethane” (which has the same properties as natural gas).

CalEPA is working to help permit anaerobic digesters at both dairies and wastewater treatment plants.

Links for more information on biogas:

Dairy Digesters

CalEPA has partnered with CDFAUSDA and U.S. EPA to form a dairy digester task force. One of the recommendations of this task force was the implementation of a consolidated permit process to aid permitting of dairy digesters and to clarify permitting processes and requirements. Consolidated Permit Fact Sheet (PDF)

Relevant Permitting Agencies have developed flow charts to demonstrate the different permitting scenarios for dairy digester projects based on project characteristics.


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Last updated: November 10, 2015
California Environmental Protection Agency,
General Public Contact, (916) 323-2514