A unique reactor design allows the conversion of raw biogas (methane and carbon dioxide) into synthesis gas (syngas; hydrogen and carbon monoxide) at capital costs 100 times lower than those for gas-fired reformer reactors. Developed by e-fuels startup company Circularity Fuels (Palo Alto, Calif.; www.circularityfuels.com), the Ouro reactor has demonstrated the ability to convert an undervalued feedstock — waste biogas from a California dairy farm — into syngas that can be made into low-carbon sustainable aviation fuel (SAF) through Fischer-Tropsch (F-T) synthesis.
In conventional steam-methane reforming (SMR), catalyst-filled tubes are heated with gas-fired burners to convert pressurized methane to syngas. “Among the issues with SMR are that only a thin layer of the catalyst material nearest to the tube surface is active, and the tubes are centrifugally cast from expensive alloys, such as Hastelloy or Inconel, to withstand the high pressures and temperatures,” explains Circularity CEO Stephen Beaton. “Also, typical reforming catalysts and reactors are not well suited to handling the CO2 component of biogas.”
“We set out to design an incredibly efficient, incredibly cheap reactor that can convert raw biogas, and if it can convert raw biogas, we can also convert CO2 and hydrogen via the reverse water-gas shift reaction,” Beaton says.
The Ouro reactor is designed with a 10- to 90-microns-thick layer of catalyst material mounted on corrugated foil that is made from an iron-chromium-aluminum alloy. The catalyst-foil sheets are spiral-wound, allowing a much smaller reactor footprint than conventional reformers (see figure).
An electrical current is applied to the alloy layer to provide heating (to about 800°C), and the thin catalyst layer is fully utilized to convert biogas as it moves through narrow channels in the reactor.
The factor-of-100 capital-cost savings are realized by the much smaller reactor, the elimination of the need to hold high pressure in the tubes and by the design of the reactor, which avoids the problems associated with uneven heating in reformers, Beaton says.
After demonstrating its technology with raw biogas, the company plans to build a pilot plant at the California dairy farm that will begin operation in summer 2026. The company also plans a 50–100-bbl/d demonstration plant in 2029 that will include a separate F-T unit to take the syngas to synthetic crude, which can then be refined to SAF.