It has become obvious that while battery-electric powertrains are a viable solution for short- and regional-haul fleets, zero-emission options for longer-range applications are sorely lacking.

It’s true that fuel cell battery-electric vehicles have the potential to move into long-haul applications. But no products are commercially available yet. And even if they were, acquisition costs and infrastructure issues are problematic. (As is still the case for commercial BEVs.).

Optimists in the industry are hopeful that internal combustion engines fueled by liquid hydrogen will one day offer fleets a viable, zero-emission option for long-haul applications.

But the best-case scenario is that hydrogen engines – assuming the technology proves out and production and infrastructure issues are resolved – could be a decade or more away from making a meaningful contribution to trucking’s decarbonization efforts.

A growing chorus of voices in the trucking industry has been lately proposing another, short-term, solution: renewable natural gas as a commercial vehicle fuel.

Is Renewable Natural Gas A Near-Zero-Emissions Fuel?

There is an immediate problem with natural gas, however. And it is one that seems to have caused the California Air Resource Board (CARB) and the U.S. Environmental Protection Agency to dig their heels in opposition to its widespread use as a truck fuel: Natural gas is not a zero-emission fuel.

“Renewable natural gas that is created by anerobic digesters (made from animal waste) get you pretty close to almost-zero carbon output when burned in a truck engine,” explains Kevin Otto, a former Cummins engineer who is now an analyst for the North America Council for Freight Efficiency (NACFE). 

“The problem that I think that CARB is trying to address is that in inner city areas where there is a lot of truck traffic, the emissions from engines are still a problem from a health perspective for residents. So CARB seems to want to deal with this problem by getting rid of internal combustion engines in these areas.”

The good news about natural gas from a NOx standpoint, Otto adds, is that it is a “heck of a lot better than diesel” in terms of tailpipe emissions.

“The latest diesel emissions regulations are now down to .035 grams per horsepower hour,” Otto says. “And you can beat that number easily with a natural gas engine.” 

In layman’s terms, that puts a natural gas engine at about 95% of the way toward a complete, zero-emission powertrain.

Admittedly, it’s not perfect.

But a rising chorus of voices in the industry are starting to ask why natural gas doesn’t make sense as a short-term, low-emission fuel for long-haul trucks?

“Natural gas is here and ready now,” Jim Nebergall, general manager, hydrogen internal combustion engines, Cummins, told me at press event held at the OEM’s headquarters in Columbus, Indiana, this past summer. 

“Moreover, its available at lower cost as a vehicle level. And it most likely will always be a lower initial cost. Because there's a lot less complexity in the fuel delivery system's lower pressures.

"It can do the job. It has the power of the torque and get the job done. You can get the range that you're used to with the diesel cost per mile is lower than diesel, and then it should continue to be that way with the low cost and stability of natural gas pricing.”