Something along bio-tech lines. Audi and US-based fuels specialist Joule have developed a remarkable process to produce e-ethanol and e-diesel, whereby microorganisms suspended in brackish or waste water can use sunlight and waste CO2 to create fuels without need for biomass.

The ‘refineries’ responsible for them are photosynthetic microorganisms, which are injected into brackish water standing in lengths of pipe. Measuring around three thousandths of a millimetre in diameter, these organisms have been genetically modified to prevent them from multiplying using the sunlight-aided photosynthesis process as they normally would.

Instead, they are stimulated to use this process to convert the waste CO2 and the waste water into liquid fuels, which they then secrete, and which can then be easily separated from the water and concentrated without the need for any further manufacturing steps.

It’s an exceptionally simple and relatively inexpensive process, without needing crop-based biomass that has traditionally been a key constituent of synthetic fuels. In essence, the resource-sparing process means that facilities can be located in remote areas, even a desert.

Already, Audi and Joule have commissioned such a demonstration facility in New Mexico, and it’s already producing sustainable e-ethanol, which has the same chemical properties as bio-ethanol. At a blend of 85%, mixed with 15% fossil-fuel petrol, the Audi e-ethanol can power petrol vehicles capable of running on E85 fuel, with only minor modification needed.

As for the e-diesel, it will work highly effectively with existing Audi TDI clean diesel systems without the need for modification. In contrast to petroleum-based diesel, which is a mixture of a wide variety of organic compounds, this one is not only free of sulphur and aromatics, but is also easy to ignite thanks to its high cetane value. Large scale commercial application may still be some time away, but the concept sounds promising – waste not, indeed.