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X3Energy operates several alternative fuel filling stations in Colorado like their newest in West Greeley on Wednesday, Oct. 20, 2021. The company sources compressed natural gas from renewable sources like landfills and sewage treatment plants.(Valerie Mosley, Special to the Colorado Sun)

The fuel that comes out of the gleaming pumps at X3CNG’s west Greeley station has the telltale smell of fossil fuel. It runs a big truck with the heavy-duty efficiency of a fossil fuel. 

But the impact of the transaction can be the opposite of burning fossil fuel. 

X3CNG and many of its competitors in the natural gas fuel business say they are now filling up Colorado’s big fleet truck operators with nearly 100% renewable natural gas. That’s the methane collected from garbage rotting at landfills, from manure ponds at big farms, and from sewage treatment plants. 

That means the compressed natural gas fueling stations that dot the Front Range can actually keep new carbon from the atmosphere, by both replacing relatively dirty diesel and by using up methane that would otherwise escape. Burning methane creates CO2, but in the process destroys a substance that has 86 times the greenhouse-creating potency of carbon dioxide.

“As an energy source, renewable natural gas can ‘decarbonize’ the gas grid,” concluded a market study by the Colorado Energy Office. The study said the most efficient sources, such as manure-derived methane, can be a 300% emissions reduction from the impact of producing and burning diesel.

Compressed natural gas was once seen as a “bridge fuel,” cleaner than diesel and gasoline engines, and useful in particular for large fleets that convert their hauling stock from diesel and gas to natural gas fuel. CNG could help run the medium- and heavy-duty trucking fleets responsible for a large portion of greenhouse gas emissions until electrification technology improved to extend range and reduce battery weight. 

But the pressure to eliminate fossil fuels only grew, and scientists and entrepreneurs combined to build projects refining usable methane emanating from rotting organic materials. Though Colorado lags in collecting large quantities of methane at its landfills, sewage treatment or big farms, natural gas pipelines are gathering it from projects in other states for commercial use.

X3CNG says it moved to a fully renewable supply in the second quarter of 2021 at its nine Colorado locations, bought from suppliers who bring it in pipelines from out of state. A competitor, Clean Energy, also says it is close to 75% renewable use at its stations across the country. 

X3Energy operates several alternative fuel filling stations in Colorado like their newest in West Greeley on Wednesday, October 20, 2021. The company sources compressed natural gas from renewable sources like landfills and sewage treatment plants.(Valerie Mosley/Special to the Colorado Sun)

Pipelines near landfills or other methane producers buy the gas and mix it with the fossil natural gas they ship around the country. As with windmills putting electricity into the grid, there’s no way to separate out which customer is using what kind of gas. But finding customers who want to advertise their commitment to renewable natural gas encourages distributors to speed up  and expand renewable projects.

With few viable electric motors on the market so far in heavy trucking, there are years of growth available in a renewable gas system, promoters say.

“From the transportation side, I think it’s unlimited,” said X3CNG President James Mora. 

State energy officials agree there is great potential during the lull before heavy trucking switches to clean hydrogen or electric engines. Though “unlimited” may be too strong a phrase. Even if Colorado does develop local commercial-scale sources of renewable gas, the most it could replace is “nearly 142 million gallons of diesel, or 24% of the state’s total diesel consumption for transportation,” the Energy Office market study said.

Still, that would make a significant contribution to the greenhouse gas emission cuts the state is committed to in target years starting in 2025. The state study said developing Colorado’s renewable biogas sources and using them in vehicles would remove 1.44 million metric tons of the CO2 caused by burning fuels each year. 

Colorado’s fleet conversion credits, used to help industries switch medium and heavy trucks away from diesel and gasoline fuel, could formerly be used for vehicles burning fossil gas. That is now phasing out. In the future, Energy Office executive director Will Toor said, the conversion help will only go for engines burning renewable gas. Either form of the gas can be burned in the same converted engine, but the companies will have to formally commit to buying only renewable gas, Toor said, in an email. 

Even renewable engines won’t get the credits indefinitely, he added. 

“Ultimately decarbonizing hard-to-decarbonize sectors, such as long-haul trucking and heavy industry, is going to require more scalable solutions, such as electrification and the use of green hydrogen,” he said. 

Colorado’s biogas projects so far involve landfills or sewage treatment plants producing relatively small amounts, which are then purified to methane and used locally in converted municipal vehicles. Such projects have come online in recent years in Longmont, Boulder, Englewood and Grand Junction. The Englewood project produces enough to be injected directly into Xcel’s local pipeline system, used primarily in building heating. 

Mora said he’s hoping for larger scale local biogas projects that X3CNG can tap into. 

“My anticipation is that we’re going to be able to source the gas regionally. Ideally you want to be as close as possible to your source,” he said. “But I think that we’re in this space right now where we have to start somewhere.”

X3CNG is part of a company headquartered in Italy, where a big differential between European natural gas and gasoline prices promoted more extensive use of compressed natural gas in fleets. X3CNG saw opportunity in building up a natural gas fuel network in the U.S., and now is pushing for renewable gas to overcome any remaining environmental concerns about fossil fuels, Mora said. 

Heavy truck operators holding out for electric engines may not see manufacturers come through for five or six years, and when they do, the earliest machines will no doubt be expensive, he added. 

“We can implement something today,” Mora said. “Put something to work right now and then, as these other solutions come out in the future, then we work towards that.”

Michael Booth is The Sun’s environment writer, and co-author of The Sun’s weekly climate and health newsletter The Temperature. He and John Ingold host the weekly Sun-Up podcast on The Temperature topics every Thursday. He is co-author with...