German carmaker Audi is engaged in the development of CO2-neutral, synthetic fuels. The latest project is a pilot plant in Dresden, which produces water, CO2 and green energy diesel fuel. Together with the project partners Climeworks, Sunfire and the plant was opened earlier this month.

With the cooperation Audi proves with its partners, that the industrialisation of the so-called e-fuels is possible. The pilot plant has officially launched on November 11. The raw materials required for the Sunfire system, which operates on the power-to-liquid principle, carbon dioxide, water and electricity. The carbon dioxide is by direct air capture – extracted from the ambient air – a technology partner of the Swiss Climeworks.

In a separate process, driven by green electricity, there is electrolysis of water split into hydrogen and oxygen. The hydrogen reacts with the carbon dioxide in two chemical processes at 220deg Celsius and 25 bar to an energy-containing liquid consisting of hydrocarbon compounds, the so-called Blue Crude. This process achieves an efficiency of up to 70 percent.

The pilot plant, which stands on the site of Sunfire in Dresden-Reick can produce about 160 litres Blue Crude in the first stage per day. Of which in turn can be up to 80 percent converted into synthetic diesel. This fuel – Audi e-diesel – is free of sulphur and aromatics, and also has a high cetane number. Its chemical composition allows a mix with fossil diesel in any proportion. It can therefore be used as a ‘drop-in fuel’.

This project, which was funded by the German Federal Ministry of Education and Research and took over two years of research and preparation, saw Audi combine two innovative technologies – firstly, capturing CO₂ in ambient air and the power-to-liquid process for the production of synthetic fuel. In the automotive sector Audi is the exclusive partner.

Through collaboration with Sunfire, Audi is already since 2009 engaged in the development of CO2-neutral fuels. The Audi e-gas plant in Lower Saxony Werlte already produces comparable synthetic methane (Audi e-gas) which customers of the A3 Sportback g-tron can obtain through a special fuel card. Together with the French company Global Bioenergies explored the synthetic production of Audi e-gasoline. And with the US company Joule runs pursued by microorganisms a project using the production of synthetic fuels Audi e-diesel and Audi e-ethanol. For the owner of an Audi A3 Sportback e-tron, Audi offers a green power solution.