Renewable natural gas (RNG) continues to play a significant role in the fueling of medium- and heavy-duty commercial vehicles in California, the state leading the push to eliminate fossil fuels in transportation in favor of electrification.
RNG, however, is not a fossil fuel.
It's produced from carbon already present in the biosphere, being sourced from landfills, wastewater, and agricultural waste—and is chemically identical to conventional natural gas.
[Related: Clean Energy's new RNG production facility requires over 2,000 cows]
A just-released report from The Transport Project (TTP), RNG Coalition, and the California Renewable Transportation Alliance (CRTA) has found that 2024 marked the fifth consecutive year that commercial fleets fueled by RNG in the Golden State have achieved a carbon-negative transport outcome.
[Related: As electric truck demand slows, CNG and RNG-powered trucks accelerate]
The report states that in 2024, RNG made up 99% of all on-road natural gas vehicle fuel in California, thanks to the state's Low Carbon Fuel Standard. According to the California Air Resources Board (CARB), the average carbon intensity of RNG was -194.13 gCO2e/MJ.
In total, 220.87 million gallons of natural gas was utilized as a motor fuel in California last year, with 218.68 million gallons of that total coming from renewable sources. RNG production in California, the report points out, continues to grow fast—23.2% of the fuel used in 2024 was made in-state, up from 6.7% in 2021, mostly from farms.
RNG-fueled trucks and buses not only have negative GHG emissions, but also cut NOx and particulate matter by 90% below federal standards, helping reduce pollution linked to asthma, heart disease, and poor air quality, according to TTP.
"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 and significantly reduce greenhouse gas and criteria pollutants… and it does so without upending existing business operations."
Another key reason why fleets in California and across the U.S. are switching from traditional diesel to RNG instead of battery-electric or hydrogen fuel cell (FCEV) is that the trucks themselves are affordable and scalable. At present, there are currently 505 operational RNG fueling facilities in the U.S. Another 153 are in various states of construction with another 293 planned.
RNG Coalition
Pricier battery-electric and FCEV rigs currently lack a similar and equally reliable nationwide fueling infrastructure, though genuine progress is ongoing for battery-electrics. But 'ongoing' doesn't mean ready for prime time nationwide.
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"Renewable natural gas is a proven, scalable solution helping California advance its clean truck goals," added Nicole Rice, president of the California Renewable Transportation Alliance. "It delivers immediate environmental benefits and supports fleets today, while complementing the broader shift to zero-emission technologies."
