This Tower in Spain Creates Carbon-Neutral Jet Fuel From Just Water, Sun and Air

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Eric Mack
3 min read
A tower catches sunlight directed from reflective panels on the ground

The solar tower fuel plant during operation in Spain. 

IMDEA Energy

What's happening

A European Union-backed project has scaled up the production of synthetic kerosene for aviation that doesn't contribute to the climate crisis.

Why it matters

About 5% of human-caused climate change can be traced back to air travel.

Exhaust from air travel is one of the top conduits of carbon into the atmosphere that contributes to climate change. A project in Europe has demonstrated that carbon neutral fuels can be created with little more than the basic elements that plants rely on. 

Researchers designed, built and tested a system that produces kerosene fuel for flight using little more than water, carbon dioxide and sunlight.

The technology to create jet fuel quite literally from thin air has been around for a few years now; the breakthrough here is scaling the process up from the laboratory to an industrial proof of concept. 

"We are the first to demonstrate the entire thermochemical process chain from water and CO2 to kerosene in a fully-integrated solar tower system," Aldo Steinfeld, a professor at the Swiss Federal Institute of Technology in Zurich (ETH Zurich), said in a statement. 

Steinfeld is co-author of a paper on the system published in the July 20 issue of the journal Joule

Something like 5% of human-caused climate change can be traced to aviation, which largely relies on fuels refined from crude oil. It's tough to find clean alternatives for many long commercial flights. 

"We can produce synthetic kerosene from water and CO2 instead of deriving it from fossil fuels. The amount of CO2 emitted during kerosene combustion in a jet engine equals that consumed during its production in the solar plant," Steinfeld said. "That makes the fuel carbon neutral, especially if we use CO2 captured directly from the air as an ingredient, hopefully in the not-too-distant future."

Related projects like Climeworks, which also has origins at ETH Zurich, are developing systems that can suck significant quantities of CO2 out of the atmosphere to be used for creating fuel and other useful products that might otherwise be derived from fossil fuels. The result is like taking pollution out of the air before using it and putting it back into the atmosphere, unlike most fuels that simply add to the problem of climate change without trying to compensate for it on the front end. 

Steinfeld's European Union-backed project produces so-called "drop-in" fuels that could be used in existing aviation engines or mixed with conventional kerosene. 

The actual facility that produces the sustainable fuel is located at IMDEA Energy Institute in Madrid and is made up of 169 panels that reflect sunlight, concentrating solar radiation into a reactor mounted on top of a tower. That concentrated heat and radiation drives cycles of chemical reactions with the reusable compound cerium oxide inside the reactor. 

This process converts water and CO2 into synthetic gas, or syngas, which is made up of hydrogen and carbon monoxide. It's then converted from a gas to liquid fuels like kerosene or diesel. 

The paper out this week says that the solar reactor's efficiency level -- the portion of solar energy input into the system that was converted into the energy content in the syngas produced -- was about 4%. Steinfeld hopes to increase this to 15%, which could eventually reduce the number of reflective panels required, increase the system's fuel output, or both.