From our viewpoint, the quantities of carbon alone—which rise as smoke from the Duisburg steelworks as carbon dioxide—would suffice to cover the entire need for kerosene of a major airline. Of course, we still have got a bit to go to reach this vision. But we have demonstrated on the laboratory scale that this concept works and could be of interest commercially. In addition to the exhaust gases, syngas—similar gas mixtures from home and industrial waste incineration—can also be used for the engineered process.

—Stefan Jennewein of IME, who is coordinating the project

The biochemists at IME use syngas—a mixture of carbon monoxide, carbon dioxide and hydrogen—as a carbon resource for fermentation. Using strains of the bacterium Clostridium, they transform the syngas either into short-chain alcohols such as butanol and hexanol, or into acetone. To do so, IME engineered new genetic processes for the efficient integration of large gene clusters in the Clostridium genome. At the same time, Fraunhofer further expanded its syngas fermentation system and used it for experiments with the steel and chemicals industry.

The chemists around Axel Kraft at UMSICHT evaporate the residual fermentation products and in a continuous catalytic process, couple the fermentation molecules into an intermediate product consisting of long-chain alcohols and ketones.

This interim product already meets the standards for ship diesel, and, like fats and oils, can be converted through hydrogenation into diesel fuel for cars or kerosene for planes.

Kristian Kowollik from the environmental engineering department at ICT obtains specialty chemicals from the interim product connected with this, which already can now directly replace petroleum-based products. For example, amines can be used in the pharmaceutical industry or the production of tensides and dying agents.

In the next stage, the scientists will strive to demonstrate that their technology also works with large quantities.

Over the next one-and-a-half years, we aim at gaining a better understanding of the processes, and to optimize them. Our goal is to apply for certification processes for the fuels. That is how its viability for practical use will be officially validated. For vehicle diesel, that takes about one year, and for kerosene about three years.

—Axel Kraft

Resources

• Sebastian de Vries, Tom Ostlender, Gabriele Philipps and Stefan Jennewein (2015) “Identification of a primary-secondary alcohol dehydrogenase loss-of-function mutant induced by random mutagenesis in Clostridium ljungdahlii for syngas-based acetone production”, P117, Annual Meeting and Exhibition Society for Industrial Microbiology & Biotechnology (August 2015)

• Breitkreuz, K., Menne, A. and Kraft, A. (2014), “New process for sustainable fuels and chemicals from bio-based alcohols and acetone.” Biofuels, Bioprod. Bioref., 8: 504–515. doi: 10.1002/bbb.1484