Though its popularity has died down recently now that GMOs, vaccines, and the origin of the 9/11 attacks have become much more exciting fodder for conspiracy theorists, for years, there have been rumors that car companies have known how to run cars on water, but that the oil companies or the federal government were keeping them quiet. Those conspiracy theorists conveniently forget the existence and popularity of early steam cars, but at the same time, it would be great if the only fuel needed to power cars was a substance as cheap and abundant as water.

You still can’t pour water into your fuel tank and run your engine on water power, but Audi has just opened a pilot plant in Dresden, Germany, that is producing biodiesel from a process that uses water, carbon dioxide, and green power. The resulting substance is being called “blue crude,” and when it’s refined, it behaves just like regular diesel fuel. In fact, it’s so similar to diesel that Audi is able to put it directly into an A8 TDI without a problem.

To create this fuel, water is heated up to become steam, and then high-temperature electrolysis splits it into oxygen and hydrogen. Under pressure and at high temperature, the hydrogen reacts with the carbon dioxide. When cooled, the resulting product is a thick liquid that is similar to unrefined diesel and can then be refined from blue crude to what Audi is calling “e-diesel.” The resulting fuel is better than petroleum-derived diesel due to its lack of sulfur and neutral scent. It also has a high cetane number, the diesel equivalent of gasoline’s octane rating, which means it combusts easily.

The efficiency of the entire process currently sits around 70%, but the production of e-diesel is also entirely carbon-neutral. Power for the plant comes from renewable energy like wind and solar power, while the carbon dioxide is supplied by both a biogas facility and technology that allows the factory to capture carbon dioxide from the air.

“This synthetic diesel, made using CO2, is a huge success for our sustainability research. If we can make widespread use of CO2 as a raw material, we will make a crucial contribution to climate protection and the efficient use of resources, and put the fundamentals of the ‘green economy’ in place,” said Johanna Wanka, Germany’s federal minister of education and research.

While Audi’s e-diesel may sound revolutionary, the idea has been around since the 1920s. It’s known as the Fischer-Tropsch process, and it’s existed for nearly 100 years. It’s never been pursued on a large scale before because of how inefficient it is, especially when using coal to generate the heat needed to convert the water into steam and separate its hydrogen and oxygen atoms. In a sense, diesel produced with the Fischer-Tropsch process is a lot like Dippin’ Dots — it’s been the fuel of the future for years, but the future never quite got the hint.

Does this mean that Audi is just blowing smoke and pretending it’s invented something revolutionary for the sake of free news coverage? That’s not necessarily the case. The process itself may not be efficient enough for widespread use now, but instead of using coal for heat, Audi is using renewable sources like solar energy and wind power to generate the heat. Not only does that make the process more environmentally friendly, it also theoretically provides a stable way to store renewable energy. Instead of relying on huge batteries to hold electricity generated by solar, wind, or water, it could instead be used to create e-diesel.

Producing e-diesel on a large enough scale to be practical is going to require a lot of energy, and the plants are going to be expensive, but the finished product certainly has a lot of potential. Plus, as petroleum gets more expensive to obtain, the cost of sustainably produced e-diesel will begin to look a lot more attractive. The fuel of the future isn’t exactly relevant today, but in 50 years, it could easily end up being very important.

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