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Audi e-diesel and e-ethanol

The mobility of the future that Audi is planning will be sustainable: efficient and climate-friendly. Together with a firm from the USA, the Company is developing the synthetic liquid fuels of tomorrow, Audi e-diesel and Audi e-ethanol.

Only four elements are required for the production of the new Audi e-fuels: water, CO2, sunlight and tailored, single-cell microorganisms less than a thousandth of a millimeter in size. Just like plants, these conduct oxygen photosynthesis, which means that they use sunlight and CO2 in order to grow. They do not need an environment of clean drinking water; saltwater or process water are sufficient. Oxygen is produced as a byproduct of the process.

Audi’s partner, the biotech company Joule of Bedford, Massachusetts, founded in 2007, has optimized this process so that the microorganisms produce and excrete either ethanol or alkanes – key components of diesel fuels – directly from carbon dioxide (CO2) and sunlight. The CO2 required for photosynthesis can come from the exhaust flow of a factory or biogas plant or even from the air. The fuels are separated from the water and cleaned.

The Audi-Joule joint demonstration plant was opened in 2012 in Hobbs, New Mexico, a very sunny region of the United States. The first Audi e-ethanol was produced in early 2013 in transparent plastic tubes. Audi e-diesel is expected to follow in the next few years. The chemical properties of Audi e-ethanol are identical to those of classic bioethanol. This e-ethanol can be admixed with fossil fuel gasoline (e.g. E10) or, alternatively, can be used as the basis for E85 fuel (85 percent ethanol, 15 percent gasoline).

Audi and Joule are working at the same time to produce synthetic diesel fuel, Audi e-diesel. A major advantage of the new fuel will be its purity. In contrast to petroleum diesel, it is free of sulfur and aromatics. Audi e-diesel will also offer excellent ignition performance thanks to its high cetane number. And its chemical composition will permit unlimited blending with fossil fuel diesel.

The demonstration plant already illustrates the major advantages of Audi e-ethanol and Audi e-diesel over conventional bioethanol and biodiesel: No biomass is required for the production of the new fuels, and they can be produced in regions that are unsuitable for agriculture. Their yield per acre (0.0015 square miles) is expected to be roughly 20 times greater than with conventional biofuels produced from corn, for example. The comprehensive life cycle analysis shows the tremendous potential of the Audi e-fuels for reducing CO2 emissions. A car that uses Audi e-fuels ultimately has a CO2 footprint on par with that of an electric car powered by electricity generated with wind or solar energy.

The collaboration with Joule dates back to 2011. Audi has acquired the exclusive automotive-sector rights to its American partner’s patented technology. The collaboration also includes technical support, where the German engineers are contributing their expertise in the area of fuel and engine testing. Commercial production of the new fuels could begin within the next five years.