Audi is set to release a number of natural-gas [NG] powered vehicles this year, such as the Audi A3 Sportback TCNG. It can run on petroleum-sourced NG, which is abundant, but is also a carbon-positive fuel. In order to make these vehicles greener, a carbon-neutral fuel would be even better.
To that end, Audi is building a new plant to generate synthetic methane fuel, run on solar- and wind-power. It is a given that solar- and wind-power, which is abundant in Germany, is the cleanest energy that can be found. Where this process makes carbon-neutral fuel, though, is how the fuel is made.
Chemistry is all around us, even within us, breaking apart some compounds and creating others that are useful for life itself. Natural photosynthesis is a great example of solar powered chemistry, and is used by green plants to convert water and carbon dioxide into sugars and oxygen.
Sugars and fuels are very similar in that they are made up of carbon chains. With a little bit of tweaking, synthetic photosynthesis can be used to make synthetic fuels, such as Audi’s synthetic methane.
The new plant, SolarFuel, is designed to manufacture enough fuel for about 1,500 of Audi’s new NG vehicles. The amount of carbon dioxide emitted by burning SolarFuel’s synthetic methane is the same as was extracted from the atmosphere to synthesize it.
Carbon-neutral is certainly better than carbon-positive. There are a couple of catches, though, since the process is only about 40% efficient. Large-scale production, hopefully, will bring that up to 60%. Additionally, methane, as a greenhouse gas, is about 20x more potent than carbon dioxide, so hopefully SolarFuel can keep that under control.