A California startup says it has found a cheaper way to turn an overlooked farm waste product into sustainable aviation fuel, potentially opening a new pathway for airlines racing to meet emissions targets.

Circularity Fuels announced it has completed what it describes as the world’s first end-to-end conversion of raw agricultural biogas into sustainable aviation fuel (SAF). The six-month pilot transformed methane-rich gas from a California dairy farm’s manure digester into jet fuel that meets ASTM standards for commercial aviation.

The achievement could reshape the economics of SAF production. The company estimates that commercial plants using its technology would cost roughly one-fifth as much as comparable facilities currently being developed in Europe.

Turning waste into fuel

The demonstration took place at a dairy farm near Madera, California, home to more than 5,000 cattle. Like many operations across the country, the farm produces biogas through manure digesters. Much of that gas often goes unused or gets released into the atmosphere.

Circularity’s system converts that waste stream directly into aviation fuel on-site. According to the company, the pilot operated continuously for thousands of hours using untreated biogas composed of roughly 65 percent methane and 35 percent carbon dioxide. The process produced finished jet fuel that can blend with conventional Jet-A fuel at concentrations of up to 50 percent.

The system combines two modular reactors designed for distributed deployment. An electrified bi-reforming reactor converts the raw gas into synthesis gas, while a compact Fischer-Tropsch reactor transforms it into liquid hydrocarbons suitable for aviation use.

Circularity said its reforming unit achieved methane conversion rates above 98 percent and carbon dioxide conversion rates exceeding 90 percent during testing.

Lower-cost SAF pathway

Sustainable aviation fuel remains in short supply worldwide. Current production satisfies less than one percent of global demand. Most SAF today relies on used cooking oil as feedstock.

Critics argue that supply constraints and import dependence limit its long-term potential. Alternative approaches, such as power-to-liquid e-fuels, also face economic hurdles due to rising electricity costs. Circularity believes agricultural biogas offers a more practical option.

The company projects commercial installations could cost less than $100,000 per barrel per day of installed capacity. Those economics could allow SAF derived from dairy waste to compete directly with fossil-based jet fuel prices. “The hard part of this industry was never designing a theoretical plant that could make SAF,” said Dr. Stephen Beaton, founder and chief executive officer of Circularity Fuels. “It was proving you could do it continuously, from real biogas, at a cost that pencils.” He added that the company has now demonstrated the technology using “real feedstock from a real dairy farm.”

Carbon-negative potential

Circularity’s internal life-cycle analysis suggests the fuel could achieve a carbon intensity score of negative 350.7 grams of CO2 equivalent per megajoule under California’s regulatory framework. That figure stems from capturing methane that would otherwise escape into the atmosphere. Methane traps significantly more heat than carbon dioxide over shorter timescales.

Craig Hartman of Hartman Engineering said dairies have long lacked practical ways to monetize biogas without investing heavily in gas-cleaning infrastructure. “Circularity is the first team I’ve seen take raw biogas straight from a digester and turn it into finished jet fuel on-site,” Hartman said.

Following the successful pilot, Circularity plans to begin construction on its first commercial facility in 2027. The company is targeting dairy and agricultural regions across the United States while also exploring opportunities in Latin America and Europe.

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