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:
CalEPA has partnered with CDFA, USDA 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.
- History of Anaerobic Digesters at Dairies in California
- Generic Anaerobic Digestion Process (PDF)
- Central Valley Water Board Programmatic EIR for Dairy Digesters (PDF)
- Permit Guidance for Anaerobic Digesters and Co-Digester Manual (PDF, 1.32 MB)
- CalRecycle/Water Board Permitting Manure Flowchart (PDF)
- San Joaquin Valley Air District Permitting Flowchart (PDF) For general assistance with siting and permitting a digester, please visit the Governor’s Office of Business and Economic Development (“GoBiz”).