According to Prometheus investor materials, the process is broken down into four main steps.
In the first step, industrial fans suck in air and blow it through a mixture of water and other compounds, which McGinnis says could include sodium carbonate. It then readily reacts with carbon dioxide molecules in the air, converting most of the carbonate to bicarbonate.
The resulting solution is then moved into a battery-like cell with a membrane in the middle and electrodes at both ends, which uses electricity to drive a series of chemical reactions that form complex alcohols. It is equipped with a catalyst based on technology licensed from Oak Ridge National Laboratory. AT early description, the lab said it had developed a catalyst made from tiny carbon spikes with copper nanoparticles. When voltage was applied, it converted the carbon dioxide dissolved in water into ethanol “with a yield of 63%”.
The Prometheus carbon nanotube membranes come into play in the third step, separating the alcohols from the water.
And in the final step, various catalysts are used to combine the alcohols and convert them into synthetic gasoline, diesel or jet fuel. In 2020 Prometheus licensed separate technology from the Oak Ridge Laboratory, which can be used to produce jet fuel from ethanol using a multi-step process based on a novel, though unspecified, catalyst.
The overall process is quite different from that used by other companies that process captured carbon into fuel. As McGinnis explained in Joule’s comment, Prometheus systems can operate at standard atmospheric pressure and room temperature. This technology also avoids the thermal energy required to produce concentrated carbon dioxide, as well as the capital cost of an electrolyzer designed to produce hydrogen. Instead, the company claims it can synthesize alcohols directly from carbon dioxide dissolved in water and then turn them into standard fuels.
If they really figured out how to do it, it “could lead to significant energy and cost savings,” says Evan David Sherwin, a research fellow at Stanford University who prepared the Environmental Science and Technology study.
One of the last slides in the Investor Materials shows a Prometheus-branded gas station with a red neon “Zero Net Carbon” sign advertising $3.50/gallon gas and $3.75/gallon diesel, which well below current prices. average prices in the USA.