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Published Date: 24/04/2015

In an effort to curb future CO2 emissions, Audi has taken a big step in creating its own synthetic fuel - Audi e-diesel - at its plant in Dresden, Germany.

Audi make first steps in e diesel

The planned CO2-neutral fuel has seen its first few batches produced at the new plant in a joint-venture between the German manufacturer and energy technology corporation sunfire.

In order to have as little negative impact as possible on the environment, the e-diesel is created out of only the raw materials of water and carbon dioxide, brought together using green power to form a liquid fuel and acts on the power-liquid (PtL) principle.

To help achieve this, direct air capturing, a technology of Audi’s Zurich-based partner Climeworks, sees a portion of CO2 extracted from the ambient air.

The process to create Audi’s e-diesel initially sees water heated up to form steam before being broken down into hydrogen and oxygen via high-temperature electrolysis (peaking at 800 degrees C), and is a more efficient method to conventional techniques due to the heat recovery.

Following this, the hydrogen reacts with the CO2 in synthesis reactors at high pressure and high temperature, resulting in a liquid made from long-chain hydrocarbon compounds known as blue crude. Overall, the processes efficiency is at around 70 per cent, and the blue crude can be refined much like fossil fuel oil to yield the end product, Audi e-diesel.

The main advantages to the fuel include it being free from sulphur and aromatic hydrocarbons, as well as having a high cetane number that allows it to be readily ignitable. Audi’s e-diesel has been shown in lab research to be suitable for mixing with fossil diesel, or prospectively, being used as a fuel in its own right.

The coming months will see the Dresden plant produce over 3,000 litres of Audi e-diesel, and is the pinnacle of the manufacturer’s research with sunfire into CO2-neutral fuels since it began in 2009. In further advances, Audi has been producing its e-gas (synthetic methane) in order to power the Audi A3 Sportback g-tron, while research is on-going into the synthetic manufacture of Audi e-gasoline with Global Bioenergies of France.

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