Closing summer, investors gathered in the auto car parking zone of a converted warehouse in Santa Cruz, California.

Purchase McGinnis, the founder and chief govt of Prometheus Fuels, was as soon as ready to blow their enjoy horns his “Maxwell Core.” The pipe-fashioned tool is filled with a membrane riddled with carbon nanotubes, forming pores that separate alcohols from water. 

That day, it was as soon as linked to a tank stuffed with both. As McGinnis explained how the abilities worked, his workers frail it to maintain the tank of a Harley-Davidson motorbike. The alcohol seeped thru the membrane, concentrating it ample to vitality the automobile, which had been converted to bustle on the gasoline, he says.

Attendees had been then invited to steal the Harley for a trudge.

It was as soon as a theatrical demonstration of the abilities key to McGinnis’s beguiling pitch: Prometheus will change into the global gasoline sector by drawing greenhouse gasoline out of the air and changing it into carbon-fair fuels which are as low-place as soiled, old ones.

Investors enjoy thrown cash at the firm. Prometheus says it has raised extra than $50 million from BMW’s Investment arm, delivery big Maersk, Y Combinator, and others. The startup has already struck deals to sell hundreds of hundreds of gallons of its fuels to American Airlines and diversified aviation firms. It earned a shoutout in a Biden administration announcement detailing US efforts to shift toward sustainable aviation fuels. And after closing its endeavor spherical final September, the firm launched that it was as soon as valued at extra than $1.5 billion. 

One of the best discipline? There is runt on hand proof it might well perchance genuinely are living up to its lofty claims. 

McGinnis and his workers enjoy built a prototype that mixes the nanotube membrane with a tool that sucks down carbon dioxide and a contemporary electrochemical cell. The system converts the captured carbon into alcohols and then concentrates them, avoiding what would otherwise be an costly and vitality-intensive distillation step as well as diversified charges.

A business-scale model would bustle on renewable vitality and add a perfect stage: changing those alcohols into synthetic forms of gasoline, diesel, and jet gasoline. McGinnis has claimed that the ensuing fuels will likely be “place aggressive” with those derived from fossil fuels and won’t emit to any extent additional greenhouse gasoline than the direction of will get rid of from the air.

The abilities would behold nothing adore the gargantuan refineries that the area is dependent on for its transportation fuels. They might well well be modular items that will likely be built anyplace, moderately cheaply. Closing April, Prometheus launched it expects to enjoy half of a million of those vegetation operating by 2030. Those might well well perhaps collectively create about 50 billion gallons of gasoline per Three hundred and sixty five days and suck down virtually 7 billion quite loads of carbon dioxide by the stop of the final decade. 

If these fuels might well well perhaps additionally be produced at the charges and on the scales claimed, Prometheus might well well perhaps additionally well overhaul the global vitality market. It might well perhaps perchance perhaps offer a easy diagram to neutralize the emissions of the autos and trucks already on the boulevard, as well because the area’s fleets of ships and planes. And it might well well perhaps minimize the tension to continue extracting fossil fuels and building oil refineries, easing the grip of petrostates and the area’s addiction to petroleum.

But Prometheus’s assertions enjoy raised eyebrows amongst researchers, entrepreneurs, and endeavor capitalists. A complete lot of experts who enjoy reviewed an investor presentation obtained by MIT Expertise Review are doubtful that the firm can elevate out the claimed charges.

“It’s funny,” says Eric McFarland, a professor of chemical engineering at the College of California, Santa Barbara. “It’s the tech bubble again,” he added later. “Folks are placing cash into moderately quite loads of issues that in a roundabout contrivance won’t ever work, and here’s one of them.”

Others are skeptical that a little startup has quietly built-in current chemistry, contemporary catalysts, and a leap forward membrane into a single place-efficient kit that will with out drawl scale to business phases. They present that the firm hasn’t publicly demonstrated a fully working system, submitted the direction of to behold overview, or supplied extra detailed records on the contrivance in which it works, even to just a few doable investors.

The reality that the firm widely missed its enjoy targets for turning in synthetic fuels to the market has raised additional doubts. McGinnis before the entirety mentioned that Prometheus would sell its different gasoline for $3 a gallon by sometime in 2020, undercutting gasoline supplied at the pump. As a replacement, two years later, the firm has yet to portion together an built-in tool that generates fuels that might well well perhaps vitality unparalleled autos this day.

All of this has created a notion amongst some that McGinnis, a theater main and playwright earlier than he earned a doctorate in environmental engineering from Yale, is a bit of a showman. His courageous claims enjoy likely helped the firm strike deals, observers snarl, however it’s made it extra difficult to decipher the reality from the hype. 

Most exterior observers that MIT Expertise Review spoke with gentle factor in it might well well perhaps steal decades earlier than carbon-capturing factories can spit out fuels as cheaply as we are in a position to dig them up. Some maintain they never will. 


Prometheus, and a few diversified startups working to create fuels from captured carbon, listing the stop product as “electrofuels,” for the explanation that direction of would successfully change into the vitality in electrical energy into liquid fuels. The promise is that they would perchance provide a lacking portion in the climate puzzle: a carbon-fair vitality source for the full transportation sector.

Batteries work excellent for electrical passenger autos, however this can gentle steal decades to supplant the full world’s autos and trucks, and produce out the foremost charging infrastructure. And no person expects batteries to vitality gargantuan ships and planes anytime soon.

It’s simply hard to beat the vitality density and convenience of liquid hydrocarbon fuels. They’re low-place and so they’re easy to ship, retailer, and combust, says Merritt Dailey, a researcher at the Middle for Detrimental Carbon Emissions at Arizona Recount College.

Electrofuels provide a diagram to continue the usage of such fuels, alongside with our current infrastructure, with out adding to any extent additional greenhouse gasoline than the direction of will get rid of. The clearest direction for producing these fuels is to produce disclose-air-take care of vegetation that employ sorbents or solvents to take care of carbon dioxide. Separately, devices known as electrolyzers can destroy up water to create a well-organized bear of hydrogen, which can then be reacted with the carbon to produce hydrocarbons.


All that is easy chemistry, and it’s the direction that one of Prometheus’s rivals, Carbon Engineering, is pursuing. In 2017, the firm, essentially based fully mostly in British Columbia, added the flexibility to create fuels from captured carbon onto its pilot plant in Squamish. In addition, it launched plans gradual final Three hundred and sixty five days to delivery bear work on a business plant halt to Merritt, BC, which might well well perhaps create extra than 25 million gallons of low-carbon versions of gasoline, diesel, and jet gasoline per Three hundred and sixty five days.

But the subject is that disclose-air-take care of tools and electrolyzers are both costly to produce and bustle. It requires with out a doubt wide heat to separate the nonetheless carbon dioxide from the sorbents and concentrate the gasoline; and it takes moderately quite loads of electrical energy to vitality the electrolyzers.

A be taught on electrofuels final Three hundred and sixty five days in Environmental Science & Expertise chanced on that with unparalleled technologies, even at stout business scale, a gasoline similar would place spherical $16.80 a gallon. It estimated that charges might well well perhaps additionally descend to about $6.40 in the next decade and $3.60 by 2050, however very best if there are main place reductions in the foremost tools and electrical energy.

Given these charges, most observers factor in that electrofuels won’t accomplish a foothold in the market with out emissions mandates, steep carbon prices, or diversified supportive insurance policies. Carbon Engineering, as an illustration, says it’s banking on executive subsidies to produce the economics work.

But Prometheus guarantees that its fuels will compete straight away with those created from oil, largely on myth of it’s avoiding key steps that produce diversified electrofuels so costly. What’s extra, the firm claims it won’t be decades earlier than this occurs, however lawful just a few years. 

Undercutting gasoline

In 2012, McGinnis left a desalination startup he cofounded, Oasys Water, however persisted working on programs of bettering a core portion of the abilities: membranes.

He came to point of curiosity on the doable of carbon nanotubes, that will also be designed to soak up or reject decided compounds. He spent years figuring out how to embed them into plastic sheets, aligning them perpendicular to the outside to bear selective pores in the supplies.

He coauthored a 2018 paper in Science Advances that showed he might well well perhaps form carbon nanotube membranes that had been efficient at rejecting salt and magnesium sulfate. Extra refinements and experiments yielded nanotubes with openings lawful gargantuan ample to enable advanced alcohol molecules thru, whereas the inner tended to repel water. McGinnis grew to change into convinced he might well well perhaps employ the abilities to simplify a costly and intricate step in one pathway for producing synthetic fuels. 

In gradual 2018, McGinnis replied to Y Combinator’s name for carbon elimination startups to notice to its accelerator program and obtained in, which he says marked the formation of Prometheus Fuels.

Within the midst of YC’s Demo Day in San Francisco the next March, McGinnis reportedly stood on stage to elevate his pitch to the gang of investors and blow their enjoy horns a refrigerator-size prototype of the tool he had done days earlier than the match.

It had sprung a leak and wasn’t operating, Science wrote at the time, however that didn’t prevent him from making a courageous claim: “At the present time, gasoline sells for $3.50 a gallon in California. Subsequent Three hundred and sixty five days, we are in a position to be selling it for $3 per gallon.” 

The formula

The formula breaks down into four predominant stages, in step with Prometheus’s investor supplies. 

Within the 1st step, industrial followers arrangement in air and blow it thru a combination of water and diversified compounds, which McGinnis says might well well perhaps contain sodium carbonate. That then readily reacts with carbon dioxide molecules in the air, transferring great of the carbonate to bicarbonate.

The ensuing solution then strikes into a battery-adore cell with a membrane in the center and electrodes on both stop, which uses electrical energy to spark a sequence of chemical reactions that create advanced alcohols. It’s geared up with a catalyst in step with abilities licensed from Oak Ridge Nationwide Laboratory. In an earlier description, that lab mentioned it had developed a catalyst created from miniature carbon spikes embedded with copper nanoparticles. When a voltage was as soon as applied, it converted carbon dioxide dissolved in water into ethanol “with a yield of 63%.”

Prometheus’s carbon nanotube membranes attain into play in step three, conserving apart the alcohols from the water. 

And in a perfect step, diversified catalysts are frail to combine the alcohols and convert them into synthetic gasoline, diesel, or jet gasoline. In 2020, Prometheus licensed separate abilities from the Oak Ridge lab that will also be frail to create jet gasoline from ethanol, thru a multistep direction of that relies on a contemporary though unspecified catalyst. 

The final direction of is significantly diversified from the one diversified firms changing captured carbon into fuels are taking. As McGinnis explained in a Joule commentary, the Prometheus programs can operate under unparalleled atmospheric tension and at room temperature. The abilities also avoids the heat vitality wanted to create concentrated carbon dioxide as well because the capital charges of an electrolyzer devoted to producing hydrogen. As a replacement, the firm claims, it might well perchance synthesize alcohols straight from carbon dioxide dissolved in water, and then convert those into unparalleled fuels.

If they’ve certainly discovered how to take care of out this, it “might well well perhaps lead to foremost vitality and worth financial savings,” says Evan David Sherwin, a postdoctoral researcher at Stanford who produced the Environmental Science & Expertise be taught.

One among the final slides in the investor supplies exhibits a Prometheus-branded gasoline space, with a crimson neon “Zero Fetch Carbon” stamp selling gasoline prices of $3.50 a gallon and diesel at $3.75, well under newest average US prices.

‘Out over their skis’

McGinnis later pushed wait on his goal date for turning in fuels, announcing in that March 2020 Joule portion: “We mission that by placing all of those advances together, this will be likely to produce renewable gasoline from [direct air capture] CO2-to-fuels all around the next two years that is place aggressive with fossil gasoline.”

When asked about that line, David Keith, a Harvard professor and founding father of Carbon Engineering, mocked it in an electronic mail: “I mission that by optimally placing all my beautiful tips together it wants to be likely, all around the next two years, for me to send a 5.13b climb [a very difficult rock-climbing grade] whereas getting elected to the Nationwide Academy and likewise launching an initiative that catalyzes global under-ocean [high-voltage, direct-current electric transmission line] interconnects.”

Each and each of Prometheus’s self-imposed crop-off dates enjoy now passed. 

McGinnis blames the delays on the pandemic and subsequent offer chain disorders, and declines to remark particularly when the firm will likely be selling gasoline at the pump. “I maintain adore I obtained myself in anxiousness on myth of I predicted issues and then covid took place,” he says.

But he provides later that if “the entirety goes our diagram,” they would perchance present the gasoline later this Three hundred and sixty five days, and “maybe” delivery delivery it commercially in 2023. 

Assorted disorders enjoy also caught the eyes of out of doors observers.

The first is the solar place Prometheus is banking on for its place estimates: 2 cents per kilowatt-hour, which McGinnis says was as soon as in step with the news that the metropolis of Los Angeles had negotiated a contract to take hold of renewable vitality for that amount.


But the Los Angeles figures mirrored a 25-Three hundred and sixty five days contract with a huge buyer that was as soon as in a position to procure rates no longer going to be afforded to a single plant. The unsubsidized charges in case you produce and arrangement vitality straight from a gargantuan solar mission in the sunniest aspects of the US is spherical 3 cents per kilowatt-hour, says Ramez Naam, a well-organized vitality investor centered on the solar sector, who is bullish on electrofuels. And charges plug up from there if a plant is drawing on vitality from additional away.

“I maintain they’re out over their skis moderately bit,” he says, though provides that solar charges might well well perhaps attain the phases the firm is projecting sometime in this decade.

Relying entirely on well-organized electrical energy, which is foremost to produce the carbon-fair math work, creates diversified constraints. To feature profitably whereas relying fully on solar or wind vitality, the vegetation themselves will might well well perhaps additionally gentle be very low-place, highly computerized and in a position to flexibly ramping up and down as phases of electrical energy generation fluctuate. Or they’ll have to contain vitality storage, adore gargantuan battery banks, which would a good deal amplify charges. In some regions, the vegetation might well well perhaps also depend on exact sources of carbon-free vitality adore nuclear, geothermal, or a combination of wind and solar sources that largely steadiness every diversified out.

When asked about the disorders raised by variable renewable vitality, McGinnis mentioned in an electronic mail that the gasoline forges are designed to operate flexibly, mercurial flipping on and off relying on availability and pricing of electrical energy. The amenities might well well perhaps additionally also depend on hydrogen they generate as a byproduct to bustle the direction of in decided circumstances, he added.

Perchance one of the best request is how well the moderately quite loads of experimental aspects of Prometheus’s system, in particular the electrochemical cells that create alcohols, will work exterior the lab.

Sean McCoy, an assistant professor in the division of chemical and petroleum engineering at the College of Calgary, says that tutorial groups enjoy explored key aspects of this direction of as well. But he provides it’s largely early-stage be taught that has bustle into challenges, noting that others working on an electrochemical direction of for changing carbon dioxide to alcohol enjoy produced “very low yields.”

“Is it technically likely to take care of out it the diagram they imply? Yes,” he wrote in an electronic mail. “But, unless they enjoy solved some main complications in the front stop, they are potentially many years from making this a business reality. Can they elevate about out it for a spot that is aggressive with fossil (with out subsidies or carbon pricing … )? I doubt it.”

McFarland provides that it might well well perhaps be very costly to elevate about the prolonged sequence of reactions wanted to generate advanced alcohols, given the high place of the electrochemical cells and the electrical energy required.

“Even when it charges them very best 2 cents [per kilowatt-hour] then they won’t be in a position to compete with fossil fuels,” he mentioned in an electronic mail.

Of direction, some maintain it’s no longer going any firm or direction of might well well perhaps ever create synthetic fuels from disclose air take care of at similar charges, given the costly hardware, the electrical energy requirements, and the flexibility of main oil-producing nations to power down the worth of fossil fuels by opting to create extra oil.

“You might well well perhaps perhaps additionally’t beat the free vitality of the solar that went into the vegetation that fashioned fossil fuels to delivery with,” McCoy says. “That’s the subject.”

It’s also conspicuous to just a few that Breakthrough Energy Ventures, Carbon Hiss and Lowercarbon Capital—three prominent endeavor capital companies with a reputation for scientific rigor and a few extent of curiosity on carbon elimination—haven’t invested in the firm. Project sources snarl the final place and technical claims gave the influence highly no longer going, and that McGinnis wouldn’t enable them to entirely vet decided scientific claims, which was as soon as considered as a crimson flag.

Stanford’s Sherwin says that the direction of “doesn’t seem crazy,” however he notes some of Prometheus’s place and effectivity assumptions elevate out appear “very aggressive.”

He raises yet another design, noting that any firm working on electrofuels will have to operate overtly, or be discipline to oversight, to produce decided the stop product is de facto carbon fair.

“It’s going to be with out a doubt foremost for synthetic hydrocarbon manufacturers to enjoy very clear and poke verification of the source at every step,” he says. “On account of it wouldn’t be hard the least bit to enjoy a magic field and sell gasoline.”

‘Correct across the corner’

In an emailed response to these disorders, McGinnis mentioned the firm will employ an fair manner of carbon-fair certification when it’s on hand. He added that there will likely be additional programs of verifying how the fuels had been produced, including thru analysis of the carbon.

He careworn out that the investor supplies weren’t designed as a stand-by myself file, noting they also supplied some companies additional records on their direction of thru a spoken pitch and diversified supplies.

“Anybody who has very best been in a position to read the pitch deck however didn’t procure it as fragment of a pitch will likely be lacking foremost context,” he wrote, adding that skeptics that weren’t otherwise conflicted might well well perhaps be convinced “if they’d entry to our records, models and strategies.”

McGinnis mentioned the firm has miniature how great it shares about its direction of to guard intellectual property, including to endeavor companies that had invested in competing firms. He says he asked such companies to depend on technical due diligence the firm had obtained from third occasion consultants.

McGinnis previously declined to discuss decided aspects of the direction of in component with MIT Expertise Review as well, citing identical reasons.

“We’ve obtained some programs that we filed patents for, and enjoy some change secrets and programs on, that I’d are making an strive to share with you,” McGinnis says. “But we’re gentle at some stage in of finalizing some of the patents.”

But he means that Prometheus doesn’t face scientific challenges at this point, announcing “there’s nothing between us and delivery gasoline diversified than scaling.” Now that the firm has raised its Sequence B funding spherical, he plans to rent mercurial and switch forward great sooner.

McGinnis provides that they’ve already begun talking with regulators about the steps they’d have to steal to sell the gasoline straight away.

Prometheus’s investors also dwell optimistic.

Marcus Behrendt, the manager govt at BMW i Ventures, the endeavor arm of the auto big, says his neighborhood is “very assured” that Prometheus is heading in the correct route and that its carbon-fair fuels are “lawful across the corner.”

“If he’s profitable, here’s going to be a terribly gargantuan sport-changer—and the percentages aren’t against him,” Behrendt says.

McGinnis says it’s steadily safe to be cynical and rob that startups will fail, for the explanation that giant majority of them elevate out. But, he provides, then you definately’ll also omit that uncommon one which does elevate a accurate leap forward.

“I realize people announcing ‘I’ll factor in it after I peek it,’” he says. “That’s why it’s so lovely that we don’t want anybody else’s permission to plug to market. On account of we both elevate out ship gasoline or we don’t.”

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