Audi pilot plant produces synthetic diesel using only water, CO2 and green electricity

The new experimental factory is partly funded by the German government, and is a collaboration between Audi, Climeworks and Sunfire.

In the test plant, an electrolysis machine uses green electricity to split water into its constituent elements: hydrogen and oxygen. The hydrogen produced via this method is chemically reacted, via two different processes, with carbon dioxide that's extracted directly from surrounding air.

These two chemical reactions take place under high pressure (2500 kilopascals) and high temperature (220 degrees Celcius), and produce an energetic soup of hydrocarbon compounds dubbed Blue Crude. Audi claims that producing Blue Crude in such a manner is 70 per cent efficient.

Blue Crude, like regular crude oil that's formed from long dead organisms, can be refined into fuel. At the German pilot facility, Audi and its partners produce synthetic diesel or e-diesel. According to Audi, around 80 per cent of the produced Blue Crude can be successfully converted into diesel fuel.

While this latest development is certainly a step in the right direction towards carbon-neutral driving, the plant can only produce 160 litres of Blue Crude daily, which in turn yields just 128L of e-diesel.

Audi claims that its e-diesel has a high cetane number, although it has yet to publish a figure. The company's synthesised diesel fuel is said to be free from aromatics and sulphur, and can be combined in any ratio with regular fossil-derived diesel.