Up in the air

On a graffiti-tagged dead-end street in East Williamsburg, a neighbourhood that marries industry with Brooklyn cool, Air Company might seem, at first glance, to be just another artisanal distiller. Housed in one of a pair of galvanised-steel Quonset huts (a nightclub occupies the other), the start-up’s distillation machinery is running round the clock to keep up with the demand for its Air Vodka. A gold-medal winner in the 2019 Luxury Masters spirits competition, the beverage has the distinction of being “carbon negative”; according to the company, the act of producing each bottle removes 450g of greenhouse gases from the atmosphere.

Air makes its vodka and other products, including a fragrance and a hand sanitiser, in a similar way to how plants create nutrients from the sun’s energy. It takes carbon dioxide, captured at industrial facilities before it is emitted into the atmosphere, and hydrogen, generated from water using an electrolyser (a device that splits water into oxygen and hydrogen atoms), then runs them through its proprietary Carbon Conversion Reactor, which is powered by electricity from wind and solar sources. The result is pure ethanol, which, paired with water, becomes a premium vodka sold at $75 (€68) a bottle.

The company combines the diverse talents of co-founders Stafford Sheehan and Gregory Constantine. The former has a doctorate in physical chemistry from Yale University and a fascination with the idea of turning emitted carbon into useful products, such as fuel; the latter, meanwhile, is an Australian with a background in marketing who previously worked for spirits giant Diageo.

Carbon diversion isn’t cheap, says Sheehan. Producing alternative fuels means competing with fossil-fuel giants. “Look at that reactor,” he says, pointing to a machine that is roughly the size of a Volkswagen Beetle. “Now, compare it to an oil refinery. Those facilities have their own zip codes.” Air needed a product that could help to fund its research and would combine Sheehan’s scientific knowhow with Constantine’s ability to tell a good consumer story – something that they could sell at a premium. “The vodka,” says Sheehan, “is a by-product of our research and development.”

Last year the company received a call from members of the US Air Force (usaf). “They said, ‘We’re looking for innovative solutions from an aviation perspective,’” says Constantine. Air had been one of the winners of Nasa’s co2 Conversion Challenge in 2021, a project exploring ways to turn the chemical compound into sugar, which astronauts could one day use to make useful products such as adhesives, food and medicine on Mars. The usaf had got wind of some of the work that Air was doing to convert co2 into sustainable aviation fuel (saf). “They told us, ‘There’s an opportunity if you guys have the ability to deliver volumes within 90 days.’”

Though Air was struggling to keep up with the demand for its vodka, the company decided that the “internal sprint” was worth it. Air Factory One, as the Brooklyn site is known, produced about 20 litres of Airmade saf, poured it all into “dairy cans” labelled with hazmat stickers, placed them on a pallet and shipped them to Florida. There, the Brooklyn-produced jet fuel was pumped into an unmanned aerial vehicle with no special modifications made to the engine. The usaf was impressed with what it saw. “The most recent round of testing confirmed it as the first fuel made entirely from carbon dioxide emissions that matches the properties and performance of Jet a-1 [conventional jet fuel],” it reported. 

On the strength of that test, Air was awarded a $65m (€59.2m) grant from the US Department of Defense’s Defense Innovation Unit this year to install its saf production technology at military bases, partly to reduce the risks of transporting fuel (for every 24 fuel convoys that the US Army undertook in Afghanistan, it sustained an average of one casualty).

That a small company best known for producing top-shelf vodka is fuelling the planes of the world’s largest air force shows how wide-ranging the search for sustainable aviation fuel has become. As aviation bodies and airline carriers commit to the goal of carbon neutrality by 2050 – and to myriad intermediate targets ahead of that – the hunt is on for a reliable, cost-effective alternative fuel that can “drop in” to existing engines. According to the International Air Transport Association, saf is expected to contribute about 65 per cent of the carbon savings (with improvements in aircraft and traffic management, among other things, expected to supply the rest).

Of course, saf is hardly new. More than 450,000 commercial flights have flown on conventional fuel blended with a sustainable alternative since 2008, when a Virgin Atlantic 747-400 flew from London to Amsterdam partly powered by a biofuel comprised of coconut and babassu oils. If you have flown out of an airport such as Los Angeles International (lax), you have probably been on a plane whose tanks contained at least a small amount of saf. 

The number of approved means of producing saf, however, has grown in recent years. Fuels produced through the conversion of biomass waste have been joined by so-called “power to liquid” solutions, such as Air’s, whose “feedstock” is not a waste oil but co2. “We have a methodology to produce a synthetic jet fuel from fats and greases, sugars and starches,” says Steve Csonka, executive director of the Commercial Aviation Alternative Fuels Initiative. “We’re almost there with a full suite of technologies to produce fuel from all manner of circular-economy waste streams.” 

All of this technological innovation will be needed to close a huge supply gap. Last year about 300 million litres of saf were produced, according to the iata. That compares to a pre-pandemic consumption height of 359 billion litres of conventional fuel. To put it another way, the entire annual output of Air Company’s Air Factory One would be sucked up and expelled by the engines of a wide-body plane on a single flight from New York to London. The need to produce sufficient quantities of fuel – and at a cost that is more competitive with fossil fuels – is leading companies to scour the planet for the raw materials for saf. “Even with this whole suite of technologies, there’s no silver bullet,” says Csonka.

The world’s largest saf producer is Neste, a Finnish energy company formed after the Second World War to secure the country’s fuel resources. Headquartered in Espoo, it was long known as Neste Oil but it dropped the second word in 2015, signalling a move away from fossil fuels. Jonathan Wood, Neste’s vice-president for renewable aviation, tellsmonocle that the company had long had a prowess for converting lower-cost “sour crude”, largely from the former Soviet Union, into high-quality diesel. A few decades ago it began to use that expertise to develop technologies to transform fats into fuels and began opening renewable refineries. It produced its first saf in 2007. “The renewable part of the business wasn’t making money for years,” says Wood. “But we stuck it out. Now it’s making a return and that’s going into the renewables arm of the business.” Neste – and, indeed, Finland – has one remaining crude-oil refinery but that too will soon shift to renewables.

While the company produces 3.3 million tonnes of renewable fuel and other products a year, only about 100,000 tonnes are bound for aeroplanes. By the end of 2023, however, Neste expects to have boosted its saf-production capacity to 1.5 million tonnes, thanks to new refineries in Rotterdam and Singapore. Even this increased supply would account for less than 1 per cent of global aviation fuel, says Wood. With an EU mandate expected in 2025 to call for saf to comprise 2 per cent of Europe’s aviation fuel, “Neste’s production alone would exceed what that would require,” he says.

Neste produces a kind of saf known as Hydroprocessed Esters and Fatty Acids (hefa) by using hydrogen to convert a feedstock, such as cooking oil, into jet fuel. While Wood underscores the importance of working with larger sites of carbon emissions, such as factories, much of Neste’s fuel comes from the fryer baskets of restaurants – from Wingstop to Burger King (in the US alone, Neste collects oil from about 80,000 restaurants). At the most recent Super Bowl, in Arizona, Neste, working with US company Mahoney Environmental, collected about 3,220 litres of cooking oil. That oil, however, needed to be transported back to Finland to be refined, which is one reason why Neste’s saf can cost as much as five times more than traditional fuel (the Neste saf used at airports including lax, meanwhile, is shipped from Finland). Wood points out that carbon-pricing regimes that impose costs on the externalities of emissions, as well as the efficiencies and learning effects of scaling up production, will eventually force fossil-fuel and saf prices to converge. In the meantime, government policy must support the forward-looking bets of Neste and others, he says.

The more saf that Neste produces, the greater the pressure on the available quantities of cooking oil, or whatever the feedstock happens to be, and the more you risk competing with sectors such as the food industry. That is why companies are seeking to broaden the range of materials that can be converted into saf. For example, US-based saf pioneer World Energy uses tallow, a by-product of beef production. But Timothy Obitts, ceo of Washington-based Alder Fuels, warns that there’s a finite supply of even tallow. “In North America, there’s about eight billion pounds [3.6 million tonnes] of tallow produced every year,” he says. “If you were to take all of the tallow in North America and make 100 per cent of that into jet fuel, you would be talking about a billion gallons [3.8 billion litres] of saf.” Not a small number on the face of it. “But we need 25 billion gallons [95 billion litres] and it continues to grow,” he says. How to meet that demand? “The only way we’re going to get there is by looking at abundant biomass that is scalable and commercial.”

Alder uses waste products from forestry and agriculture for its feedstock. These range from bagasse, the fibrous residue from sugar-cane production, to purpose-grown grasses such as miscanthus. The advantage of the latter, notes Obitts, is that you’re “using dirt that can’t bear crops and basically rehabilitating it”. Alder builds on pyrolysis, a heat-driven decomposition process, to create a kind of oil. “People have been trying to figure out for years how to make this pyrolysis oil,” says Obitts. “It’s simple and easy to make, and can be refined.” Through Alder’s proprietary process, backed by grants from the US Department of Energy, a “greencrude” is produced that, says Obitts, has the potential to be “a lot closer to the price of fossil crude oil without the incentives”. Citing research from the US Department of Energy, he says that the use of existing forestry and agricultural residues could supply enough biomass-derived fuel to offset about 75 per cent of conventional fuel consumption in US aviation.

Alder is in a rapid commercialisation phase and already has a commitment from United Airlines to its product. There are currently only two facilities in the US that produce saf at scale, says Csonka. But more are on the way. “If you look at the offtake agreements [the arrangements that airlines make to buy a company’s future production], the entire production of jet fuel has been more or less completely purchased for the first 12 facilities.” Nine of those 12, says Csonka, “don’t even have even concrete or steel in the ground but the airlines have bought fuel from them. We have a lot of production in our future.” 

At the site of the Germany Aerospace Center in the town of Jülich, North Rhine-Westphalia, two towers rise from a field. They are surrounded by a cluster of more than 2,000 mirrors that track the sun’s movement and beam the reflected light towards the towers. Last year, Swiss start-up Synhelion, which was spun out of research by eth Zürich, used the facility to produce “sun-to-liquid” synthetic fuel, or “syngas”, on an industrial scale for the first time.

Gianluca Ambrosetti, Synhelion’s co-ceo and co-founder, says that the idea of using mirrors – “heliostats” – to harness the power of the sun’s rays has a long history, from the mythical story of Greek sailors using bronze shields as mirrors to destroy the Roman fleet in 212bc to the deployment of solar-concentration power plants in places such as Spain and California. The technology fell out of favour, he says, after the price collapse of photovoltaic panels but it has an advantage when it comes to producing fuels: heat. Synhelion has been able to reach temperatures exceeding 1,500c in its receiver; that heat is directed into a reactor, along with bio- methane and co2, to produce a syngas that is then converted into sustainable liquid fuel. Because heat can be stored much more efficiently than electricity, he says, the plant can run at night using the preceding day’s sunlight. He explains that the whole process echoes the way in which greenhouse gases are created, albeit in this case harnessed for benevolent ends. “We are turning an enemy into a friend,” he says.

Backed by investment from Swiss International Air Lines, as well as industrial firms such as Mexico’s cemex (with which it is developing a way to drive cement production with solar thermal energy instead of burning fossil fuels), Synhelion has broken ground on an industrial demonstration plant in Jülich, with plans to construct a commercial facility in Spain in 2025. Ambrosetti says that the plant will produce 1.25 million litres a year. That scale would be below the radar for the fossil-fuel world but he says that for “solar people”, it’s “already huge”.

While scale will be the watchword in the world of saf over the coming years, Ambrosetti says that, unlike in the technology industry, this isn’t “a winner-takes-all game”. “Because of the way that energy conversion works, you will have a series of boundary conditions that makes one technology better than the other,” he says. As crucial as government intervention is, favouring one technology at the expense of others could hinder innovation, which might be the most crucial feedstock of saf. How quickly we will reach genuinely sustainable flying is a roundly debated question, one that might ultimately be driven more by policy and price than technological feasibility. But one thing is clear: there is no one fuel yet poised to fill every tank.