Car makers are on a quest to develop more sustainable and more environment friendly sources of power for the cars of the future. Some have, at least for the time being, resorted to using electricity instead of conventional fuel. However, even electricity has its own eco footprint. And some car makers haven't entirely given up on the advantages of fuel. That is why companies like Audi are also investing in research and development that will produce fuel using nothing but carbon dioxide or, in this case, plants.