Making fuel is supposed to be difficult. You have to wait for dinosaurs to evolve, go extinct and spend millions of years decomposing into thick, black goo. Then you have to drill that goo out of the ground, ship it half way around the world in massive tanker vessels, refine it, transport it and pump it into a waiting car.
Or you could just combine water and atmospheric CO2 to create e-diesel.
That's the route Audi has chosen and its Dresden-based plant has just this week made its first batch of one of the world's first entirely eco-friendly hydrocarbon fuels.
Of course, it's not quite that simple (nothing ever is) but the process is sound, and while the plant is set to produce a mere 3,000 litres of e-diesel over the coming months it's at least a hint at a possibility of a chance that the internal combustion engine may not yet be dead.
The process, as far as Audi will let us in on the secret thus far, takes water heated up to form steam which is broken down into hydrogen and oxygen by means of high-temperature electrolysis (running an electric current through the steam). This process, involving a temperature in excess of 800 degrees Celsius, is said to be more efficient than other techniques because of heat recovery, for example.
Outside air
It’s then combined with carbon-dioxide (CO2) from two sources – a nearby biogas facility and CO2 actually scrubbed from the outside air. That’s right, this is a fuel that actually removes carbon from the atmosphere. Well, borrows it anyway.
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 efficiency of the overall process – from renewable power to liquid hydrocarbon – is very high at around 70 per cent. Similar 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 burns well. Audi says it can already be mixed with regular diesel to reduce a car’s carbon footprint, and has the potential to become a fuel in its own right.
Component
Reiner Mangold, head of sustainable product development at Audi, sees Audi e-diesel and Audi e-fuels in general as an important component that complements electric mobility.
"In developing Audi e-diesel we are promoting another fuel based on CO2 that will allow long-distance mobility with virtually no impact on the climate. Using CO2 as a raw material represents an opportunity not just for the automotive industry in Germany, but also to transfer the principle to other sectors and countries."
