In March this year, an Airbus A321neo took off from Toulouse airport. In its tank was a liquid on which the aviation industry has pinned a huge amount of promise: sustainable aviation fuel (SAF), a low-carbon alternative to traditional jet fuel made from crude oil.
Policy changes in Europe and the US, plus a series of technological breakthroughs, mean there’s increasing interest in this greener fuel — and startups working on the technology to produce SAF are seeing an uptick in investor interest.
One of those is Oxford University-spinout Oxccu, which has just raised a $23m round from roster of investors whose futures are somewhat tied to the fuel’s development: oil majors Aramco Ventures and Eni, United Airlines, commodity trading house Trafigura, plus climate-focused VCs Clean Energy Ventures and Kiko Ventures.
“People will keep flying,” says Andrew Symes, founder and CEO of Oxccu, which is working on technology to help create e-fuels, a type of SAF. “The onus is on the industry, and on the scientists, to try and solve the problem.”
Not all SAF is created equal
At present, very few planes fly with any SAF in their tanks. The European Commission wants at least 2% of jet fuel to be made from sustainable sources by 2025 — rising to 70% by 2050.
To reach that 2050 figure, it's estimated that the airline industry will need 450bn litres of SAF yearly. It’s a huge increase: today, the world’s biggest producer, Finnish company Neste, makes 45m litres a year.
SAF falls into three categories: biofuels, fuels made from waste and e-fuels. Biofuels are made from biomass — typically plant matter. Like conventional jet fuel, biofuel creates CO2 when it's burnt, but, because it’s made from plants which have pulled CO2 from the air, rather than oil from under the ground, it's considered to be more sustainable.
The problem with biofuel is that a huge amount of land is needed to grow the crops, leading to deforestation and leaving less room for food production. Making things worse, nearly all of the world's SAF at the moment is biofuel. If it takes up more and more land, it could have serious climate ramifications.
E-fuels: aviation's only hope?
Oxccu is working on tech for the third category, e-fuels, which are the furthest away from production. No one is producing it at scale — but it’s the category that policymakers and academics say has the most potential.
E-fuels are made by combining captured CO2 with hydrogen to form a fuel. The fuel still produces CO2 when it’s burnt but, because it’s made from CO2 that’s been captured from the atmosphere, it’s circular and more or less carbon neutral.
E-fuels can be made from CO2 using direct air capture (machines which pull CO2 from the sky) or from point-of-source emissions (CO2 captured from oil or gas production). Symes envisions the industry will start by using point-of-source CO2. “Then we can use biogenic [CO2 released in natural processes] or direct air capture CO2 in the future. And that will be a fully circular fuel, that will be carbon neutral.”
Using point-of-source emissions brings down the environmental impact compared with regular kerosene, but it also relies on the continuation of existing fossil fuel industries. Direct air capture pulls existing CO2 from the sky — but the industry is still nascent.
Paul Peeters, professor of sustainable transport at Breda University in the Netherlands, says e-fuels are the only way the aviation industry will get greener at scale. “The aviation industry is very aware that this is their only chance to stay credible,” he says. “An important advantage of the fuels is that you can really close the cycle.”
E-fuels’ energy intensity
That said, Peeters cautions that e-fuel production also requires a huge amount of energy, both for direct air capture plants and to produce green hydrogen for the process. At present, he says, you need five times the amount of energy to produce the fuel as the amount of energy stored in the fuel.
Models suggest that, even with upped efficiency, e-fuel production would take a chunk of the world’s renewable energy to produce.
“You would need something like 10-15% of all renewables in the future, just to produce fuel for aviation, which is just a half a percent of the global economy — and mainly just a small elite which flies a lot,” says Peeters.
Oxccu's tech, Symes says, can reduce the energy intensity of e-fuels, by lowering the amount of green hydrogen (which is produced using energy) needed and recirculating some of the heat produced in the process.
Bringing down the cost
Another hurdle for e-fuels is cost. “Everyone loves the idea of turning CO2 into fuel, because you've got an enormous amount of feedstock and it can scale rapidly, but the challenge has been around cost,” says Symes.
That’s where Oxccu’s tech comes in. The company is producing a catalyst that makes the fuel production process one-step rather than two-step. There’s growing consensus that government regulation will also have to come in to bring the cost of SAF down compared to conventional jet fuel.
Oxccu is currently building a facility at Oxford airport to demonstrate its catalyst. After the pilot, it intends to sell the tech to other vendors. Fossil fuel companies are particularly interested in e-fuel tech (hence Aramco’s backing of Oxccu). The Middle East in particular is emerging as an interested region — it’s a key refuelling hub for planes and has a significant amount of green energy to use in the production process.
‘We have to restrict aviation growth’
Despite his optimism about e-fuels, Peeters believes that urgent regulation is needed to curb the growing number of flights. The more flights people take around the world, the more renewable energy would have to be funnelled into e-fuels to curb the flight’s environmental impacts.
“We have to restrict the growth of aviation, at least to zero, maybe even go down in some places, to take into account developing countries taking a little bit more because they have nothing at the moment,” Peeters says.