NACFE: Natural gas has promise, but not perfect alternative solution

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Updated Mar 28, 2024

NACFE natural gas confidence report cover imageThe North American Council for Freight Efficiency (NACFE) turned its attention to natural gas this week, releasing its newest Confidence Report, Natural Gas’ Role in Decarbonizing Trucking, during a press conference Monday.

NACFE Executive Director Mike Roeth says the council's newest report addresses natural gas as a fuel source and how it could potentially reduce greenhouse gases, while also touching on its short-term benefits to reducing immediate health effects caused by air pollutants like nitrogen oxides and particulate matter.

NACFE notes natural gas has been a common fuel in transportation for decades but recently has experienced a large uptick in interest due to being a lower-carbon fuel than diesel and being cleaner burning (today's natural gas already keep NOx to levels well below California's Omnibus and EPA 2027 requirements).

Diesel emission regulations and natural gas viability chartNorth American Council for Freight Efficiency

Roeth also adds renewable natural gas in particular is being looked at because of its potential to have a negative carbon intensity when the feedstock is from animal waste. He says RNG availability is growing but its long-term access remain somewhat unknown. He states, “The question is how much of it is there, and how much will transportation get to use?”

In revealing the results of its Confidence Report, NACFE assessment of natural gas was measured. 

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“CNG and RNG offer a lot of benefits as we decarbonize the transportation industry, however, there are challenges. Each fleet must assess all of these to be assured it is the right solution while in the messy middle,” says Jeff Seger, NACFE’s clean energy consultant.

NACFE’s new report also provides an overview of the various types of natural gas and details fleets’ experience using natural gas fuel for their medium- and heavy-duty trucks. It looks at available natural gas engines and truck makers that are offering a natural gas option in their product portfolios.

NACFE says fleets most evaluate natural gas advantages and drawbacks when considering if the fuels make sense for their operations from a productivity and sustainability perspective. 

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“Natural gas engines need to be looked at as part of the ‘messy middle’ so fleets can decide if they want to invest in it considering other powertrain options,” says Roeth. “It has it pluses and minuses, but it does produce less CO2 per unit of energy on a full-comparison basis compared to No. 2 diesel fuel.”

Beyond lower emissions and near-zero potential, NACFE says other advantages for natural gas include near diesel performance for larger (15-liter) engines, similar maintenance and service requirements and a growing fueling infrastructure. NACFE says natural gas fueling stations aren't nearly as prevalent as diesel, but the fuel has been around a while so there still a lot more stations than electric, hydrogen and other alternative options.

Benefits and challenges of natural gas use in truckingNorth American Council for Freight Efficiency

Roeth also notes the growing interest around Cummins' 15-liter natural gas engine as a positive. He says NACFE’s research indicates carriers who previously had written off natural gas as a viable option for their operations are now reconsidering the fuel thanks to the larger engine. NACFE's John Baxter attributes the 15-liter's higher torque and quieter performance, as well as easier maintenance thanks to longer spark plug change intervals as reason's for larger engine's growing popularity. 

But storing natural gas is a drawback too. NACFE says more fueling stations need to be added for true long-haul viability and the cost of on-vehicle fuel storage is much higher with natural gas than diesel. Natural gas vehicles also can have experience dangerous methane leaks if not properly stored. And while vehicle performance can be comparative to diesel, natural gas is still a lower efficiency option in miles per diesel equivalent.

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There's also a lot less financial support available for fleets to offset their purchase of new natural gas-powered vehicles. Fleets motivated to hit zero-emission benchmarks may prefer to acquire larger grants and incentives to buy more expensive electric trucks to achieve ZEV goals. Natural gas does not aid California operators looking to hit Advanced Clean Fleets' ZEV mandates. 

NACFE says its Confidence Report addresses nine key findings about natural gas engine use in commercial vehicles:

  • There appears to be a wide range in perception and results regarding the business case for natural gas.
  • There are several positive environmental aspects of natural gas engines.
  • There are environmental concerns with natural gas.
  • Sustainability goals, regulations, and the California conundrum are considerations.
  • The new 15-liter Cummins X15N engine seems promising.
  • Aftertreatment is simple and more reliable.
  • Natural gas is very abundant in the US.
  • There is a question as to whether there will be an ample supply of RNG.
  • Because of economics and the environment, there are a few points to consider when comparing BEV and CNG.

For more information about NACFE's natural gas research, to access this Confidence Report, and all other research into vehicle fuel and propulsion options, check out the NACFE website.