The partners in the EU KEROGREEN project have developed a scalable process for the production of green kerosene for use as an aviation fuel based on a new plasma technology. The work was coordinated by the Dutch Institute for Fundamental Energy Research (DIFFER) in Eindhoven, and a research facility was set up at Karlsruhe Institute of Technology (KIT).

The technology is in the final phase of system integration, in which the individual elements are already connected to a closed unit, but are still at a different levels of development.

The process is essentially based on three steps:

1. The CO₂ from the ambient air is first fed into a reactor in which it is decomposed into carbon monoxide (CO) and oxygen by a plasma generated with microwave radiation. The plasma serves to split CO₂ into CO and O₂ at high conversion ratio by employing microwave technology. The technology is scalable to the MW range, does not use scarce materials and instantly switches on and off with the flick of a switch, responding well to the intermittent nature of renewable electricity.

2. The oxygen is then removed, while the CO is partially converted into hydrogen in a second reactor by means of a water gas shift reaction. The oxygen separator employs high temperature oxygen conducting membranes that selectively transport the oxygen out of the mixed gas stream. Plasmolysis combined with electrochemical oxygen transport forms the innovative part of the project.

3. This hydrogen and the remaining CO (in combination referred to as synthesis gas) are converted into hydrocarbons in a third reactor using Fischer-Tropsch synthesis.

High molecular weight hydrocarbons that cannot be used for the production of kerosene are split in the plant within the process. The final product is the basic component of the fuels common in air traffic. This raw material can then be refined to the desired kerosene or stored directly as an energy storage device.

Synergy between plasma-activated species and the novel perovskite electrodes of the oxygen separator raise CO productivity and energy efficiency. CO₂ emitted upon fuel usage is recirculated as feedstock to the process by direct air capture. The technology relies on inexpensive existing infrastructure for storage, transport and distribution.

Although, according to the findings of the researchers, plasma technology would be possible up to the megawatt range, it is also suitable for use in small, decentralized production plants in container format.

Future plants will be modular and scalable and could therefore be easily integrated into an offshore wind farm or a solar park in the desert. If wind or sun are not present, the plasma reactor would temporarily switch off and simply restart with available energy.

—Professor Peter Pfeifer from KIT’s Institute of Microprocess Engineering