Commercial fleets fueled by renewable natural gas (RNG) in California achieved carbon-negative transportation outcomes for the sixth consecutive year in 2025, according to a report from The Transport Project, RNG Coalition and the California Renewable Transportation Alliance.

The report says RNG accounted for 98% of the natural gas used by on-road natural gas vehicles in the state and achieved an average carbon intensity score of -198.32 gCO2e/MJ, making it the lowest-carbon transportation fuel under California’s Low Carbon Fuel Standard.

Although RNG represented just 6% of alternative transportation fuel used under the program, it generated more than 25% of all greenhouse gas emission reductions, according to the report.

“When used as a transportation fuel, RNG displaces gasoline and diesel in applications that are difficult – if not virtually impossible – to electrify,” said Daniel Gage, president of The Transport Project. “Renewable natural gas offers the most immediate, cost-effective, and scalable way to deploy clean trucks and buses.”

The report also notes nearly 22% of the RNG used by California fleets was produced within the state, up from less than 7% in 2021, while arguing RNG offers a lower-cost pathway to reducing emissions than battery-electric trucks in many heavy-duty applications.