Audi backs synthetic fuels development

Two promising avenues of study are pointing to a future of off-set fuels for internal-combustion engines – and Audi is leading the way with the help of corporate partners.

As long as three years ago we reported that Audi had set to work producing bio-diesel from waste products and genetically-modified bacteria, but now the car manufacturer and its partners have gone a step further.

Late last month Audi announced it had produced the first batches of a synthetic diesel, 'e-diesel', at a new production plant in Dresden, Germany. The plant is operated by a team named Sunfire, which takes renewable energy from wind, solar or hydro-electric sources, and splits hydrogen and oxygen atoms apart in water molecules by the process of reverse electrolysis.

In an explanation published by Gizmag, the remaining hydrogen is mixed with carbon monoxide (converted from carbon dioxide by removing one oxygen atom from each molecule). This blending of hydrogen and CO yields long-chain hydrocarbons that Audi refers to as 'blue crude'. Some of the CO2 is supplied from a biogas facility, but some of its take directly from the atmosphere. The e-diesel produced by this method burns cleaner in diesel engines, since there's no sulphur content. Audi and Sunfire anticipate that the fuel could go on sale – once production is set up on an industrial scale – for not much more per litre than the pump price for the fossil fuel equivalent.

In the weeks since then, Gizmag has also reported a similar scheme for synthetic petrol production. Audi's partner for the project this time around is Global Bioenergies, which has developed a procedure to extract gaseous isobutane from renewable biomass sugars. The process begins with the biomass, like corn-derived glucose, and the conversion to gaseous isobutane results in a substance that is the building block for plastics and fuels. In this case, Global Bioenergies sends the gaseous isobutane from its home base in France to Germany, where the substance becomes synthetic, 100 octane petrol. This is referred to as either Isooctane or, within Audi, as 'e-benzin'.

Once again, as with the 'e-diesel', the 'e-benzin' contains no sulphur, but it also contains no trace of the toxic chemical benzene. According to the makers, e-benzin is also better for performance engines running a high compression.

"To me this is a historic moment," said Global Bioenergies CEO Marc Delcourt, as quoted in the Gizmag article. "It is the first time that we have produced real gasoline from plants."

In the short term, Audi and Global Bioenergies will set their sights on commercialising the process and ramping up production. A new plant will be established in Germany, to produce 100 tonnes of isobutane and isooctane during 2016.

And further down the track, the partners will put aside the renewable biomass in favour of working directly with water, hydrogen, carbon dioxide and sunlight alone to produce e-benzin. When that happens, Audi will be involved in two distinct production processes making combustible synthetic diesel and petrol from water, air and sunlight.