City of San Mateo Digester Gas to Biomethane for Vehicle Fuel

This report for the California Energy Commission is for the City of San Mateo’s project to sustainably and cost-effectively produce low carbon vehicle fuel from the unused digester gas that is generated at the city’s wastewater treatment plant. In the report are the details of the project from inception to design to construction to production as well as costs and schedules.

The concept for the project began in 2014 and construction was completed in 2016. Fuel is being produced and vehicles are being filled and powered with the compressed natural gas. The City of San Mateo is actively participating in the Federal Environmental Protection Agency’s Renewable Identification Number credits and the State of California’s Low Carbon Fuels Standards credits for the biomethane production.

The City of San Mateo’s current challenge is locating and purchasing vehicles equipped to run on compressed natural gas. With only three vehicles in its fleet, gas consumption is only a fraction of what is available. The average usage to date is twelve gas gallon equivalents per day versus the five hundred gas gallon equivalents per day that the system can process from the available digester gas.

With the new and innovative equipment, the City of San Mateo entered into extended 5-year warranty and maintenance service agreements with the equipment manufacturers and has built into the service agreements the training for on-site City personnel. The final outcome of this project will be that the production, consumption and maintenance of the digester gas to biomethane gas will be under the direct control of the City.