Circularity Fuels advances cow-manure biogas toward daily jet fuel

By Grace Kim

Circularity Fuels says a six-month trial produced synthetic kerosene from raw manure biogas that met ASTM D7566 Annex A1, allowing blending at up to a 50% share with conventional jet fuel.

For aviation, the result establishes eligibility; it does not establish airline supply. The fuel standard is settled; commercial scale is not.

What did the trial demonstrate?

The San Francisco Bay Area startup reported the results in June 2026. It said the trial was “the first to take raw biogas from a dairy’s leftover manure to create synthetic kerosene that meets aviation standards for blending with conventional jet fuel.”

The trial took place at a dairy with about 5,000 head of cattle in California’s San Joaquin Valley, near Madera. As manure breaks down in the farm’s digester, it releases methane and carbon dioxide.

Circularity designed its equipment to use both gases, drawing raw biogas directly from the digester without first removing carbon dioxide. Both gases therefore enter the fuel process rather than requiring a separate carbon-dioxide removal step.

An electrically powered reactor converts methane and carbon dioxide into synthesis gas, a mixture of hydrogen and carbon monoxide. A second reactor applies the Fischer-Tropsch process to convert that gas into liquid hydrocarbons.

Both reactors mount on skids, making the equipment easier to operate at the farm. Circularity has disclosed neither installation costs nor maintenance requirements, and it gives no capacity for the planned demonstration plant.

What does the ASTM standard permit?

Circularity said the fuel met ASTM D7566 Annex A1, the specification for synthetic kerosene made using the Fischer-Tropsch process. Fuel produced under that specification can account for up to 50% of a blend with conventional jet fuel.

That 50% figure defines the permitted blending share, not guaranteed airline adoption. No named airline, flight test or fuel purchase agreement is reported. Eligibility and adoption are separate milestones; only the first is established.

Circularity estimates that capturing methane that would otherwise escape from cow manure prevents more warming than making and burning the jet fuel causes. By the company’s calculation, that makes the fuel “carbon-negative.”

The estimate treats avoided methane emissions as an offset against fuel production and combustion emissions. Circularity supplied the calculation, and no independent verification is cited. Carbon negativity remains a company claim, separate from the ASTM fuel specification.

What does $7 million buy?

The company recently raised $7 million in seed funding to build a demonstration plant that can produce fuel daily. The money will also fund design of the first commercial plant, planned at 75 barrels a day, or a little over 3,000 US gallons.

At continuous operation, that nominal commercial capacity equals 27,375 barrels of fuel a year. Circularity has stated neither the demonstration plant’s daily output nor the commercial plant’s construction cost. The funding is committed; unit economics remain undisclosed.

Trucks Venture Capital and DCVC led the funding round, with Sum Ventures and Automotive Ventures also participating. Circularity says it has raised about $17 million to date, including nearly $7 million in grants.

Circularity has not provided a fuller breakdown of the $17 million by funding source. Grants nevertheless account for nearly $7 million, or roughly 41% of the reported total.

The company said the US Department of Agriculture advanced its application for a federal loan guarantee to the second stage of review. That is progress through review, not an approval or guarantee. The USDA process concerns project financing; it does not extend the ASTM result.

The company disclosed no guarantee amount, terms or decision date. Without those figures, the loan’s effect on financing costs cannot be calculated.

When could airlines buy the fuel?

Over the next 18 months, Circularity intends to:

• Run the demonstration plant, which can produce fuel daily.
• Finish the first commercial plant design.
• Secure fuel purchase agreements with airlines.

The company says it will break ground on a production facility only after those steps. Running the demonstration moves the project beyond its six-month trial. Completing the design must then supply the engineering and cost detail needed for construction, although the source gives no budget.

A signed purchase agreement would establish contracted demand. Breaking ground would begin physical capacity, but both remain future steps rather than completed commercial operations.

Until purchase agreements specify volume and duration, the 75-barrel figure remains a design capacity rather than contracted supply. Without a construction budget, per-gallon price or airline volume, neither cost effects nor network coverage can be calculated.

The next 18 months will show whether daily demonstration output, a completed commercial design, signed airline purchase agreements and progress through USDA review turn a six-month fuel trial into a daily production project. Until then, Circularity has demonstrated fuel quality, not commercial scale.