RNG-Fueled Fleets in California Mark Five Years of Carbon-Free Outcomes

Washington, DC – Last calendar year marked the fifth consecutive year that commercial fleets in the State of California fueled by bio-CNG (renewable natural gas, or RNG) achieved a carbon-negative transportation outcome, according to a report released today by The Transport Project (TTP) and RNG Coalition alongside partner California Renewable Transportation Alliance (CRTA).

Lowest carbon intensity fuel: -194
Renewable natural gas accounted for 99% of all on-road fuel used in natural gas vehicles in California in 2024, driven by the state’s successful Low Carbon Fuel Standard (LCFS) program. According to data from the California Air Resources Board (CARB) the annual average carbon intensity score of bio-CNG in that mix was -194.13 gCO2e/MJ.^[1]

In fact, bio-CNG holds the lowest average carbon intensity of any clean fuel option on California’s roadways today and is the only fuel producing a negative carbon intensity fleet outcome in the California Low Carbon Fuel Standard (LCFS) Program, which includes ethanol, biodiesel, renewable diesel, bio-CNG, bio-LNG, electricity, alternative jet fuel, and hydrogen.^[2]

Close to one-quarter of all CO2e reductions
Even more, while RNG made up just 5.6% of all on-road alternative fuels dispensed by volume under the California LCFS in 2024, it generated 22.5% of all carbon dioxide equivalent (CO2e) emission reductions of on-road alternative fuels reported. ^[3]

Captured above ground from organic material in agricultural, wastewater, landfill, or food waste, RNG can produce carbon-negative results when fueling on-road vehicles like short- and long-haul trucks, transit buses, and refuse and recycling collection vehicles.

“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.”

Overwhelmingly renewable; growing in-state production
TTP and RNG Coalition report that in 2024 a total of 220.87 million gallons (DGE)^[4] of natural gas were used as motor fuel in the state. Of that, 218.68 million gallons (DGE) were from renewable sources.^[5] Even more, rapidly increasing amounts of RNG motor fuel used in California are produced in state; 23.21% in 2024 versus just 6.74% in 2021, and the overwhelming majority is from agricultural operations.^[6]

“Renewable Natural Gas (RNG) continues to decarbonize heavy-duty trucking in California and beyond amid historic growth of RNG facilities across North America,” said RNG Coalition’s Sam Wade, VP of Public Policy. “On the demand side, RNG use in California has grown 44% over the last five years, displacing millions of tons of greenhouse gas emissions and generating more reductions than any other clean fuel under California’s Low Carbon Fuel Standard. With 99% of natural gas vehicles in California already operating on RNG, the challenge before us is to accelerate the conversion of diesel engines to those fueled by RNG, so these benefits are extrapolated across all medium- and heavy-duty fleets in the State, and beyond.”

In addition to their negative greenhouse gas (GHG) emissions, ultra-low NOx medium- and heavy-duty RNG-fueled trucks and buses perform at levels that are 90% below the federal nitrogen oxide (NOx) standard and 90% below the federal particulate matter (PM 2.5) standard.^[7]  NGVs virtually eliminate criteria pollutant emissions that contribute to asthma, heart disease, and poor air quality.

Most cost-effective, immediate emissions reduction
Investing in RNG-fueled trucks and buses provides policymakers the most cost-effective way to achieve significant emissions reductions from commercial transportation sources today. With $100 million in grant funding covering the full price of new clean vehicle purchases, investing in RNG-fueled Class 8 trucks delivers six times more greenhouse gas and two times more criteria pollutant emissions reductions than deploying similar battery electric trucks. If $100 million in new truck grants covered just the incremental truck purchase cost over legacy diesel, RNG investments deliver 12 times more greenhouse gas and 3.5 more criteria pollutant emissions reductions than battery electric, deploying 1,333 RNG trucks versus just 357 battery electric trucks.^[8]

“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. We support a technology-neutral approach that embraces all pathways to cleaner air and lower emissions. RNG is ready now and plays a vital role in achieving a sustainable clean truck transition. We’re proud to support policies that drive meaningful progress.”

More clean trucks deployed = more emissions reduction
Unlike developing heavy-duty ZEV options including battery electric and hydrogen, RNG-fueled trucks and buses have access to an established California public fueling infrastructure and a mature network of servicers and suppliers. RNG trucks are affordable and scalable, meeting range and operations requirements for any commercial medium- and heavy-duty application. And RNG fueled trucks and buses do not rely on components sourced and controlled overseas.

Today’s 2024 RNG Volumes report – including graphics – can be accessed at: TTP’s website HERE and RNG Coalition’s website HERE.

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^[1] California Air Resources Board, Low Carbon Fuel Standard Program Reporting Tool Quarterly.  Available at:  https://ww2.arb.ca.gov/resources/documents/low-carbon-fuel-standard-reporting-tool-quarterly-summaries.

^[2] Ibid.

^[3] Ibid.

^[4] DGE = diesel gallon equivalent.

^[5] Total Natural Gas in Transportation Figure derived from U.S. EIA’s Annual Energy Outlook (2023) and RNG numbers derived from U.S. EPA Renewable Fuel Standard Program reporting with adjustments made based on fueler member reporting.

^[6] California Air Resources Board LCFS Data Dashboard, Figure 10b, last updated 6/6/25. Accessible at: https://ww2.arb.ca.gov/resources/documents/lcfs-data-dashboard

^[7] Cummins, Inc.  Available at: https://www.cummins.com/engines/natural-gas/on-highway.

^[8] https://transportproject.org/wp-content/uploads/2025/08/TP-RNG-CA-Decarbonize-Final-8-28.pdf

The Transport Project is a national coalition of roughly 200 fleets, vehicle and engine manufacturers and dealers, servicers and suppliers, and fuel producers and providers dedicated to the decarbonization of North America’s transportation sector.  Through the increased use of gaseous motor fuels including renewable natural gas and hydrogen, the United States and Canada can help achieve ambitious climate goals and greatly improve air quality safely, reliably, and effectively without delay and without compromising existing commercial business operations.  Find out more at: transportproject.org.

RNG Coalition is the non-profit association providing leadership, public policy advocacy and education for the sustainable development, deployment, and utilization of renewable natural gas. Membership is comprised of 400+ companies committed to supporting RNG Coalition’s mission and Sustainable Methane Abatement & Recycling Timeline (SMART). RNG Coalition represents industry, including leading companies, municipalities, ports and airports, colleges, and universities throughout the United States and Canada. Find out more at: www.rngcoalition.com.

 The California Renewable Transportation Alliance is an advocacy and education association that represents fleet operators, vehicle engine manufacturers, renewable fuel producers, utilities and fuel providers. Our member companies are dedicated to providing alternative transportation fuel and technology options to further California’s climate change goals and support the broader use of renewable natural gas (RNG) as a transportation fuel to improve emission reduction outcomes to reach our goals. Find out more at: https://ca-rta.org/.