In 2011, Audi announced radical plans to start energy production using wind farms located in the North Sea. By feeding this renewable energy back into the grid, Audi could boast that the energy used by its future electric cars would be completely clean.

However, instead of stopping there, Audi looked at turning some of the renewable energy into liquid fuels that could used by more conventional cars. The first was a synthetic gas chemically similar to natural gas that Audi started producing in 2013, called e-gas. This was followed in 2015 by a synthetic gasoline, called e-benzin. (Benzin is the term for gasoline in Audi’s home market of Germany.)

Now Audi is preparing for the start of production of synthetic diesel, called—you guessed it—e-diesel.

For e-diesel, Audi together with partners Ineratec and Energiedienst will construct a plant in Laufenburg, Switzerland. The plant will be able to take excess energy generated by hydropower as well as CO2 from the air and turn this into a fuel that can power diesel cars, making them almost CO2 neutral.

The process works by initially using renewable energy to split water into hydrogen and oxygen via electrolysis, essentially the reverse of what goes on in a hydrogen fuel cell. The hydrogen then reacts with CO2 using a special technology. Typically, the CO2 is obtained from the air or bio waste gases. Long-chain hydrocarbon compounds are formed and then separated into e-diesel. A wax is also generated and can be used in other areas of industry.

Construction of the Laufenburg e-diesel plant will start in early 2018 and should be completed before the year is out. It’s only a pilot plant to test the viability of the technology. Audi estimates that around 105,000 gallons of e-diesel can be produced each year once the plant is up and running.