Cleaning Up In California

by Tom Bryan (Ethanol Producer Magazine) In the lower Central Valley, Calgren Renewable Fuels makes three biofuels—ethanol, biodiesel and renewable natural gas—and the latter operation just keeps growing. -- As out-of-state ethanol producers strive for lower carbon intensity scores to make good in California’s market, one legacy low-CI producer in the Golden State is ironically more focused on a different output—renewable natural gas.

“We’ve been at this—dairy digester, manure-derived biogas production—for some time now, and it’s worked out really well,” says Lyle Schlyer, president of Calgren Renewable Fuels LLC in Pixley, California. “The bulk of our biogas doesn’t power our biofuel plants. It goes to RNG, which is a more profitable end use. It earns us a D3 RIN, which we don’t receive when the biogas is used for energy onsite.”

Calgren, a 58 MMgy corn dry mill built in 2009, primarily rails in corn from the Midwest. Schlyer says the plant is currently running at a relaxed pace. “I’d like to say we we’re at full capacity,” he says, “but that’s seldom the case.”

To be clear, Schlyer says, the ethanol plant is in nice shape and running well—partially powered by biogas—as is Calgren’s co-located 5 MMgy biodiesel plant, which utilizes brown grease (trap grease, animal waste, etc.) and distillers corn oil (DCO) at about a 50/50 ratio. “We initially thought we’d use less brown grease—maybe 20%—but ended up hitting a higher number,” he says, adding that the biodiesel plant has been a “challenging but fruitful” part of Calgren’s biorefining experience since it came online in 2019. “We’ve had to learn a lot over the past few years, but it’s worked out nicely. The brown grease aspect has been especially good.”

Calgren, which operates another ethanol plant of the same size and design in south-central Kansas (Pratt Energy LLC), has morphed its Pixley biorefinery into what it is today—an integrated ethanol/biodiesel/RNG complex—through stages of layered investment.

The RNG produced at Calgren's facility is mostly used as a carbon-negative fuel for heavy-duty vehicles like transit buses and long-haul trucks, but it can also be delivered to customers to generate clean electricity and heat homes and businesses, which is what Southern California Gas Co. plans to eventually do.

Just a few years ago, it was reported that Calgren’s affiliated dairy digesters represented the manure waste from over 65,000 cows in the Pixley area, but Schlyer says that number is over 100,000 today. “Candidly, our diary digester work has been so successful that it’s hard to not keep building more,” he says, describing how the company sells RNG to SoCalGas, which has committed to replacing 20 percent of its traditional natural gas supply with RNG by 2030.

Aemetis also Going All-In on Biogas/RNG
In Keyes, California, Aemetis Inc. has optimized its unique geographic location in a way that truly highlights the benefits of biogas integration and usage. Starting roughly a year and half ago, the 60 MMgy advanced biofuel producer began using biogas to directly power a boiler at the plant. Doing so allowed Aemetis to expand its dairy-based biogas business.

“We are in the middle of the world’s largest dairy shed,” says Eric McAfee, CEO of Aemetis. With a $4.1 million grant to construct a biogas upgrading facility, Aemetis was able to utilize a pipeline already delivering biogas from more than a dozen anaerobic digesters at dairies in two California counties.
This January, the company also completed a biogas pipeline spanning 36 miles across multiple dairy digester sites. The California Air Resource Board, through the California Energy Commission, supplied grant money for the pipeline.

In early April, Aemetis successfully completed testing of its biogas-to-RNG upgrading and compression facility. Pacific Gas & Electric is now conducting final tests of the utility gas pipeline interconnection—already constructed—which will enable the injection of RNG into PG&E’s pipeline. Ultimately, Aemetis would like to grow the operation to include more than 60 dairies and capture more than 1.6 million MMBtu of biomethane per year. READ MORE