Audi has been an active member of green thinking in the automobile world. Its new focus is the processing of e-fuels from air, water and green electricity. Audi has just opened a pilot plant for the e-fuel project located in Dresden. This plant will be producing diesel fuel from complicated processing done with partners companies Climaworks and sunfire. At its current state, the pilot plant on sunfire grounds in Dresden has a capability of producing about 160 litres of Blue Crude a day, which eventually can be converted to about 80 percent synthetic diesel. This clean fuel is termed as Audi e‑diesel is free from sulphur and aromatic compounds. Another advantage of this e-diesel is a high cetane number. A high cetane rating implies that the fuel ignites very easily and its characteristic properties allow it to be blended in any ratio with conventional fossil diesel. This means that it can be used as a drop-in fuel.
The sunfire plant functions according to the power-to-liquid principle and requires carbon dioxide, water and electricity as raw materials. Carbon dioxide is harnessed directly from ambient air through the use of direct air capturing, a method developed by Swiss partner Climeworks. On the other hand in a separate process, an electrolysis unit powered with green electricity splits water into hydrogen and oxygen. This hydrogen is then reacted with the carbon dioxide in two chemical processes conducted at 220 degrees Celsius and a pressure of 25bar to produce an energetic liquid, made up of hydrocarbon compounds, which is actually Blue Crude. This process surprisingly is up to 70 percent efficient.
Source : CarDekho