Circularity Cuts Cost Of Making Sustainable Aviation Fuel From Bio-Methane

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Manure — regardless of its source — produces methane when it decomposes. Dairy farms have an abundance of cow manure, which they store onsite in large, covered containers called manure digesters. The waste from their cows is pumped into those sealed tanks, where bacteria break it down into methane-rich “biogas” and a nutrient-rich “digestate” that can be used as fertilizer. In most dairy farms today, the methane is released directly into the atmosphere or flared off, which is another way of saying burned.

Instead of being vented or flared, the biogas from the manure digesters can be converted to fuel for aircraft and diesel-powered trucks and that is exactly what Circularity Fuels in California has done. During a recent six-month trial, biogas from a manure digester at a California dairy farm was successfully converted to a drop-in aviation fuel that meets ASTM D7566 Annex A1 specifications. That’s the standard that has to be met to make sure the fuel will not damage the jet engines of commercial aircraft.

Based on the result of the trial, Circularity claims its proprietary technology allows the construction of sustainable aircraft fuel facilities that cost just 20 percent of similar installations in Europe. That would lead to SAF that is cost competitive with jet fuel made from fossil fuels. At the present time, everyone in the industry is looking for ways to increase the supply of sustainable aviation fuel at a price that is affordable. Until that price point is reached, SAF will be nothing more than window dressing while the airline industry continues burning traditional Jet A at the rate of 300 million gallons a day.

Turning Waste Into Fuel

In a press release on Jane 15, 2026, Circularity noted that international geopolitics — such as starting stupid wars for no apparent reason — has destabilized crude oil markets and sent the cost of air travel soaring. SAF offers a domestically produced alternative, it said, but today’s global SAF production still meets less than 1 percent of demand. SAF production today is dominated by used cooking oil, which suffers from limited scale and doesn’t mitigate energy security risks given the majority of it is imported from China. Advanced SAF proponents have touted e-fuels as the solution, but rising utility rates make that approach economically challenging.

“The world’s waste biogas resource is large enough to supply the entire global jet fuel market. The dairy farm in California where the company’s technology was tested is home to more than 5,000 cows. At the present time, it vents nearly all of its biogas to the atmosphere. The Circularity system let dairy operators monetize that methane on-site, without the cost of removing carbon dioxide.”

Over thousands of operating hours, Circularity’s two-reactor system operated on raw biogas — 65 percent methane and 35 percent carbon dioxide — drawn straight from the dairy’s digester — and produced finished jet fuel. “Both are modular, low cost, skid mounted reactors, so the system is sized for the small, distributed scales at which biogas is actually produced,” the company said.

“The pilot program was the first to convert raw biogas into ASTM D7566 Annex A1 jet fuel using a fully integrated, modular system. The Ouro reactor achieved more than 98 percent methane conversion and more than 90 percent CO₂ conversion in a single electrified step. The high CO₂ content of biogas has historically been the main barrier to economical conversion. The resulting fuel can be blended up to 50 percent with conventional Jet A for use in commercial aircraft today. Internal life-cycle modeling based on California’s regulatory framework puts the fuel’s carbon intensity at -350.7 gCO₂e/MJ, firmly net carbon-negative.”

The negative score is made possible because producing the fuel consumes methane that the dairy would otherwise vent to the atmosphere. The avoided methane outweighs all emissions from producing and burning the fuel, making each gallon equivalent to removing roughly 100 pounds of CO₂e from the atmosphere, according to the company.

Commercial Viability

“The hard part of this industry was never designing a theoretical plant that could make SAF. It was proving you could do it continuously, from real biogas, at a cost that pencils,” said Stephen Beaton, the founder and CEO of Circularity Fuels. “We’ve now done that. The full stack works end-to-end on real feedstock from a real dairy farm, and the economics put commercial SAF from dairy waste within reach of fossil jet fuel.”

“For two decades, we’ve watched dairies flare or vent biogas because the only off-take options required millions in cleanup equipment and a pipeline next door,” said Craig Hartman of Hartman Engineering, a developer of agricultural biogas projects. “Circularity is the first team I’ve seen take raw biogas straight from a digester and turn it into finished jet fuel on-site. That changes the conversation for every dairy operator we work with.”

With the integrated technology stack now validated in the field, Circularity Fuels expects to break ground on its first commercial site in 2027, targeting agricultural biogas resources across the United States, Latin America, and Europe. It is backed by $8 million in seed funding together with awards from ARPA-E, the National Science Foundation, and the California Energy Commission.

On its website, Singularity Fuels says, “For centuries, access to cheap liquid fuels and chemical feedstocks has depended on who sat above the right subsurface resources. Cheap renewable power changed what’s possible. Industrial plants and farms off-gas enormous streams of waste carbon while much of the world faces fuel and feedstock shortages. By pairing abundant waste carbon with low cost renewable electricity in the Ouro Reactor™, we make synthetic hydrocarbons abundant and affordable, and give every region a path to energy resilience that doesn’t depend on what lies beneath it.”

The Rest Of The Story

Researchers at the Johns Hopkins School of Public Health published a study recently that found bio-digesters, which are supported by large federal and state grants, offer somewhat fewer benefits than advocates claim. They noted that digesters may often end up “pollution swapping” — reducing methane emissions while increasing ammonia emissions, toxic byproducts from biogas flaring, and other pollutant releases into the environment. “Digesters don’t appear to be the solution for agricultural contaminants that proponents would have everyone believe,” said Brent Kim, an assistant scientist who was one of the authors of the study.

The researchers suggested that digester technology promotes industrial scale agriculture, which has been widely demonstrated in prior studies to pose elevated risks from air and water pollution, animal-to-human disease transmission, and other public health hazards to rural populations.

“When we adopt a measure to address a problem, even an ineffective measure, society and policymakers tend to move on as if the problem has been solved,” says Kim. “Evaluating the state of scientific evidence surrounding newly purported ‘solutions’ is a critical step when we’re dealing with complex, systemic problems for which silver bullets rarely exist.”

There are hundreds of bio-digesters in the US and the majority of them are in California, which heavily subsidizes the technology. The question is whether making SAF from the existing bio-digesters is making a bad situation a little more tolerable or whether it will encourage the construction of more bio-digesters that have limited environmental benefits.

SAF may be a partial solution to low-carbon air travel, one that provides dairy farmers with an additional revenue stream, but it shouldn’t interfere with better options on the horizon that will eliminate virtually all emissions from commercial air travel. Sustainable aviation fuel may be a bridge to the future, but it is no substitute for true zero emissions flight.