Making carbon neutral airplane fuel out of thin air

Magicians make a living out of convincing an audience they’re able to pull objects out of thin air. We know it’s a trick and willingly suspend our disbelief for entertainment. Now science has devised a way to bring sorcery into reality, but instead of rabbits or playing cards, they’re conjuring jet fuel.

It might sound like it’s ripped from the pages of fantasy or science fiction, but it’s real, according to a recent paper published in the journal Nature. Aldo Steinfeld, Professor of Renewable Energy Sources at ETH Zurich, and colleagues, developed a proof-of-concept fuel production plant on the roof of ETH’s Machine Laboratory building. It’s been in operation for the last two years and the team believes it’s now ready for prime time.

Reduction of carbon emissions continues to be a global challenge as the effects of anthropogenic climate change continue and increase. As of 2018, roughly 3% of CO2 emissions came from aircraft, with another 5% coming from maritime shipping. The transition to electric vehicles continues apace and reduces some of those emissions, but there are limitations, largely due to battery life, which poses a challenge for long-distance travel like flights or trans-oceanic shipping.

A shift to greener combustible fuels could help lower the burden of flying and sailing on the environment by essentially recycling carbon emissions. ETH’s small roof-top factory pulls carbon dioxide and water out of the air before feeding them into a solar reactor. The reactor generates heat up to 1,500 degrees Celsius (2732 degrees Fahrenheit) and includes a ceramic structure made of cerium oxide which reacts with CO2 and water to create syngas. Those gases are then processed into hydrocarbons.

The process creates droplets of liquid fuel (methanol and kerosene) which can then be burned in the same way as traditional fuels. The major difference is the process extracts the same amount of carbon from the atmosphere during production as it later releases when burned. So long as renewable energy sources like solar power are used during production, the whole process is carbon neutral.

Similar efforts are underway from the U.S. Air Force, who is working with another company to extract fuel from the air in order to sidestep logistical challenges of transporting fuels around the world.

These experiments show the feasibility of producing liquid fuels from materials present in the air — the trick works — the challenge now is bringing it to scale in a way which is competitive with existing infrastructure.

The study authors project a large facility could produce fuel at a cost of 1.2 to 2 euros per liter, which is admittedly more expensive than existing sources. And the initial costs of construction are a challenge. They suggest a gradual approach, wherein airlines might be required to acquire some percentage of their fuel supply from this method. This strategy would infuse the nascent industry with the needed funds to scale and would have minimal impact on the overall cost of flight.

As indicated by the Air Force efforts, this process of fuel production has the benefit of being able to occur anywhere, so long as there’s a sufficient source of sunlight for energy. Scientists suggest building a facility in desert regions where they would have an ample supply of sunlight. This has the added benefit of using space which is currently not being used for housing, commerce, or agriculture.

The small roof-top fuel plant’s production is minimal, generating about one deciliter (one-tenth of a liter) of fuel per day. According to the team’s projections, a plant a square kilometer in size could produce 20,000 liters per day, and a plant spanning a third of California’s Mojave Desert could produce enough fuel to supply the whole aviation industry.

A shift to this alternative fuel source is estimated to enable an 8% reduction in overall carbon emissions, and the underlying technology could further pull carbon from the air for sequestering if scaled sufficiently. There aren’t any magical solutions to the climate crisis, but there are scientific ones that feel a bit like magic. That might have to be good enough.