The Solar-Jet project has successfully demonstrated the entire production chain for renewable kerosene obtained directly from just sunlight, water and carbon dioxide captured from the air. The process also has the potential to produce other types of fuel, such as diesel, gasoline or pure hydrogen, for transport applications in a more sustainable way.

The project was funded by the European Union and involved several European institutions including ETH Zürich, Bauhaus Luftfahrt, Deutsches Zentrum für Luft- und Raumfahrt, ARTTIC and Shell Global Solutions.

Although the individual steps of the process have previously been demonstrated, they have never before been integrated into a complete end-to-end system.

The Solar-Jet project used concentrated sunlight to produce sufficiently high temperatures to break up the carbon dioxide and water into hydrogen, carbon monoxide and oxygen. The oxygen was then removed using ceria (ceriom oxide) which, when heated to 1500ºC releases its oxygen as a gas which was pumped out. The reduced ceria then took up the oxygen released from the carbon dioxide and water, leaving just hydrogen and carbon monoxide, or “syngas”.

This solar-driven redox cycle is still at an early stage of development.

The syngas was then converted into kerosene using the commercial Fischer-Tropsch process. This process, which was developed in the 1920s, is a collection of chemical reactions that is already being used on a global scale to make kerosene that is approved for use in aviation.

The combined approach has the potential to provide a secure, sustainable and scalable supply of renewable fuel for aviation and general transport applications.