The facility in Dresden operates according to the power-to-liquid (PtL) principle and uses green power to produce a liquid fuel. The only raw materials needed are water and carbon dioxide. The CO2 used is currently supplied by a biogas facility. Additionally, initially a portion of the CO2 needed is extracted from the ambient air by means of direct air capturing.
How it is made:
1. Water is heated up to form steam is broken down into hydrogen and oxygen by means of high-temperature electrolysis.
2. In two further steps, the hydrogen reacts with the CO2 in synthesis reactors, again under pressure and at high temperature. The reaction product is a liquid made from long-chain hydrocarbon compounds, known as blue crude.
The process's overall efficiency is about 70 per cent. Similarly to a fossil crude oil, blue crude can be refined to yield the end product Audi e-diesel. This synthetic fuel is free from sulphur and aromatic hydrocarbons, and its high cetane number means it is readily ignitable.
Audi conducted tests to conclude that this product can either be admixed with fossil diesel or, as a fuel in its own right.
Furthermore, the company is also developing synthetic petrol Audi e-gasoline.
