Audi has revealed that it has managed to use water and air to create its own synthetic diesel fuel, or liquid “e-diesel,” as an alternative fuel source for cars. The German automaker worked with clean technology company Sunfire to create the fuel at its plant in Dresden through a “power to liquid” process that uses carbon dioxide, according to CNN. Carbon dioxide, created mostly through the burning of fossil fuels, is the most common of greenhouse gases and is a major contributor to global warming.