A biogas energy recovery system was constructed at the Las Gallinas Valley Sanitary District (District) wastewater treatment plant in San Rafael, California. While the potential to generate renewable energy from the treatment of wastewater is well established in the industry, this system utilizes the digester gas generated by the WWTP to operate a pre-commercial biogas utilization system that consumes 100 percent of the WWTP’s methane generation. The biogas energy recovery system is comprised of a BioCNGTM 50 System to condition digester gas; two 65-kilowatt microturbines to generate heat and power for the site; a hydronic boiler to provide supplemental heating; and a time-fill compressed natural gas filling station to fuel the District’s compressed natural gas flusher truck.
As part of its continued efforts to reduce its reliance on non-renewable energy resources and further its strategic environmental plan, the District envisioned replacing the outdated internal combustion engine previously used for combined heat and power generation. The biogas energy recovery system replaced the internal combustion engine with a more environmentally forward-looking system that provides greater self-sustainability for the site.
Anaerobic digestion, coupled with combined heat and power and the production of renewable compressed natural gas for transportation, provides optimal end-use flexibility for digester gas. The importance of biogas utilization to reduce methane emissions in California is substantial. Since capturing and beneficially using biogas is the best way to mitigate methane emissions, the project demonstrates the application at wastewater treatment facilities throughout the state to help meet the requirements of SB605 (Short-Lived Climate Pollutants) and AB32 (Global Warming Solutions Act), as well as California’s other renewable energy mandates.
Author(s)
Jessica Bernardini, P.E., Paul Stout, P.E., Garth Bowers, P.E. (AZ)
