Aviation faces perhaps the biggest challenge in transitioning away from fossil fuels—but the industry now appears to be coalescing around a synthetic jet fuel solution.

The weight and volume of batteries make them unsuitable for aeroplanes of more than approximately six passengers, so a molecule-based solution is essential. Renewable fuels, which can be blended and used in conventional engines, offer the most promise.

“We want to derisk all the technologies behind these synthetic fuels” Cortijo, Repsol

Bio-kerosene, although more advanced in terms of its development, has limited potential due to the lack of organic feedstock—which anyway has its own environmental problems—and therefore production capacity.

Instead, synthetic kerosene is the most viable long-term alternative, with the global aviation industry to need 500mn t of renewable fuel annually by 2050, UK jet engine manufacturer Rolls-Royce estimates. Commercial development, however, has remained slow.

Spanish oil and gas company Repsol is building a €60mn ($72.4mn) demonstration plant in Bilbao—one of the first of its kind globally—to manufacture synthetic fuels for aviation, ground transport and, eventually, shipping.

The refinery will make green hydrogen through renewable electricity-powered electrolysis of water, also capturing CO₂ from the adjacent refinery’s steam reforming plant in order to manufacture synthetic fuel. In later phases, the plant is expected to capture CO₂ from the atmosphere.

“We want to derisk all the technologies behind these synthetic fuels,” says Javier Ariztegui Cortijo, Repsol’s senior manager of product design and energy systems.

“Part of what we want to prove with this demo plant is how all these standalone technologies can be combined together to work synergistically and in an efficient and reliable way. Synthetic fuel plants should have a reliability comparable to conventional refineries and be able to operate 24/7.”

Repsol is in the process of deciding which CO₂ capture technology to deploy.

“The economics of the plant are still theoretical. If we can achieve the projected numbers our plan is to build a full-scale industrial plant that could produce 200,000 to 500,000t of synthetic fuel annually,” adds Ariztegui. “We could start producing that by the end of this decade.”

Rival projects

Meanwhile, Germany’s Raffinerie Heide has an agreement with national airline Lufthansa to produce and supply synthetic kerosene. The refiner, along with five other institutions including Chemieanlagenbau Chemnitz, has also launched the KEROSyN100 research project, which aims to develop and produce environmentally friendly synthetic kerosene.

The three-year project, which will make green hydrogen via excess electricity from a nearby offshore wind farm, received €4.2mn in government funding.

Although the fuel will produce CO₂ when burned, it has an abatement potential of around 70pc, according to Heide chief executive Juergen Wollschlaeger.

The project remains in an R&D phase, Wollschlaeger says, with further work required to identify and improve the catalyst as well as to finalise the plant design. Production will start in 2023, with the plant producing 1,000t per month. “We certainly believe there is a sizeable market opportunity here,” he adds.

Netherlands’ SkyNRG, a market maker and trader of sustainable jet fuels, is developing a demonstration synthetic fuel plant based on CO₂ capture in the Netherlands that will have an initial daily production capacity of 1,000 litres.

SkyNRG does not develop technologies in-house, so is partnering with specialists across the world such as Switzerland’s Climeworks and Canada’s Carbon Engineering.

“We are working with both of them—they have different technological approaches,” says Oskar Meijerink, senior project lead at SkyNRG, which facilitated KLM’s inaugural commercial flight using renewable fuels, the world’s first such trip.

The company has supplied renewable fuels to more than 30 airlines globally. “The systems are pretty modular so you can scale up pretty quickly once the technology is perfected,” says Meijerink.

500mn t/yr – Renewable aviation fuel required by 2050

The European trio are notable in their willingness to embrace the risk and uncertainty in crafting such nascent technology and industrial techniques. A 2019 paper by the German Aerospace Centre warns private investment will be insufficient to hasten development of so-called power-to-liquid (PtL) production and use.

“In order to avoid the market failure emanating from the first-mover disadvantage, the state could offer guaranteed prices for PtL fuels,” the report adds. “This would create legal certainty for investors and incentives for PtL production.”

Another consideration is the large amount of energy required to make synthetic kerosene.

“It will only work if there is an abundance of renewable electricity available at an affordable price,” adds SkyNRG’S Meijerink. “Globally, we still rely on fossil fuels to make electricity, so the development of renewable jet fuel must go together with the expansion of renewable electricity capacity.”

 

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Author: Matt Smith