Comprehensive Assessment of Co-Digestion Capacity, Costs, Impacts, and Operational History in California

Recent legislation in California aims to reduce short-lived climate pollutants like methane released from decomposing organic material in landfills. One potential alternative to landfilling this organic material is to co-digest it at municipal wastewater treatment plants and beneficially use the biogas generated. This study conducted on behalf of the California State Water Resources Control Board assesses the feasibility of co-digesting food waste in existing anaerobic digesters across California. This study quantifies the costs and benefits to co-digestion and estimates the amount of food waste that could be diverted and the amount of methane emissions that could be reduced. Six case studies are also presented of wastewater treatment plants who have implemented or plan to implement food waste co-digestion to understand their lessons learned through this process. The full results of the study will be documented in a comprehensive report to be published soon by the California State Water Resources Control Board. As such, this paper provides a preview and short summary of key results.