RNG Gains New Momentum in Longhaul Trucking
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Range, fuel supply and refueling infrastructure concerns tend to be the biggest bumps in the road for any alternative to a diesel tractor, but recent data and developments indicate at least one emerging technology’s path forward is becoming clearer — renewable natural gas.
And without many of the hurdles that battery-electric trucks face.
Natural gas vehicles consumed the equivalent of 774 million gallons of gasoline in the U.S. in 2024, according to figures released by The Transport Project at the end of June.
Some 86% of natural gas vehicles were fueled by renewable natural gas last year, the advocacy group’s data show, even though the U.S. was the largest producer of conventional natural gas in the world in 2024.
A gallon of gasoline equivalent (GGE) is the most common way compressed natural gas is sold at public fueling stations for trucks or buses. A diesel gallon equivalent (DGE) equals 1.136 GGE, with a gallon of diesel containing around 13.6% more energy than a gallon of gasoline.
North American RNG production capacity is set to reach 604 million cubic feet per day by the end of 2025, according to Wood Mackenzie analysts, after jumping 70 mmcf/d in 2025 and 139 mmcf/d in 2024.
RNG, also known as biomethane, can be transported along conventional natural gas pipelines.
(U.S. Gain via RNG Coalition)
A natural gas-powered tractor running on RNG reduces emissions of nitrogen oxides by 90% compared with its diesel peer, according to consulting firm ICF.
Back-of-cab fuel storage systems are available to power Cummins’ X15N engine in capacities from 60 DGE to 175 DGE. Side or rail mount tanks are offered in 30-100 DGE capacities.
X15N fuel storage systems are available from either Cummins Clean Fuel Technologies or Hexagon Agility. CCFT is a joint venture between Cummins and Rush Enterprises.
A tractor with a natural gas engine can therefore meet the carriers’ range needs when it comes to longer lanes.
Historically, refuse trucks, school buses and commercial buses were the biggest users of CNG and therefore RNG.
That’s expected to change with the introduction of the X15N, particularly after Daimler Truck North America in late April opened the order book for Freightliner Cascadia tractors — the best-selling Class 8 on-highway tractor in America — powered by the engine.
Freightliner previously said in October 2023 that customers would be able to buy Cascadias equipped with the X15N.
(Dairy Cares)
The X15N engine was already available for Kenworth’s T680 and T880 models and Peterbilt’s 579 semi, 567 vocational and 520 refuse models.
Serial production of the X15N engine began in September 2024. Cummins argues the X15N matches the performance of its biggest diesel engine, unlike its predecessors. The X15N is available with as much as 500 horsepower and 1,850 pound-feet of torque.
DTNA’s order book announcement came on the opening day of the 2025 Advanced Clean Transportation Expo in Anaheim, Calif.
The conference was abuzz about the prospects for RNG and other cleaner-burning fuels that can be used by internal combustion engines.
U.S. RNG producers will need to manufacture around 115 million to 120 million gallons of RNG in 2026 if Cummins’ market share ambitions for the X15N come to fruition, Clean Energy Fuels CEO Andrew Littlefair told ACT Expo attendees. Newport Beach, Calif.-based Clean Energy Fuels is the largest RNG supplier in the U.S.
Production of RNG is rising in advance of the expected surge in demand, according to the Wood Mackenzie analysts.
“We forecast RNG production to grow across all types of feedstock, and the resource potential for RNG could exceed 7.8 billion cubic feet per day by 2050,” said Natalia Patterson, senior research analyst at Wood Mackenzie.
(Wood Mackenzie)
The United States has the largest potential among advanced economies, according to a recent report from the International Energy Agency.
In mid-June, the RNG Coalition said the 500th operational RNG facility in North America had been commissioned. A further 153 facilities are under construction and another 293 in the planning and permitting phases, the trade association said.
While the energy return is lower from CNG and therefore RNG, the retail price of CNG is typically less than the average for diesel fuel. In April 2024, the nationwide difference was about 80 cents per DGE, according to data from The Transport Project. In some states, the spread can be closer to $2.50 per DGE, it noted.
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The alternative fuel tax credit provides a 50 cents/gallon credit for natural gas motor fuel credited at the point of dispensing.
The price of RNG has fallen over the past 12 months. As have D3 Renewable Identification Number prices. RINs are part of the Renewable Fuel Standard program, which mandates the blending of renewable fuels into the transportation fuel pool. Starting in 2014, RNG was recognized under RFS.
On May 22, the House of Representatives extended the Section 45Z Clean Fuel Production Tax Credit, which includes support for RNG. On June 28, the Senate’s “big, beautiful bill” included a provision extending the credit through 2029.
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