Artificial photosynthesis: a contribution to the energy transition

For some years now, Creavis researchers have been working on the idea of using bacteria to produce specialty chemicals by fermentation from syngas, which is a mixture consisting mainly of carbon monoxide (CO) and hydrogen (H2). Syngas can be obtained from a wide variety of sources, such as industrial waste gases, and is therefore available everywhere. A process of this type has many advantages: recyclability of waste gas streams as raw material for production of higher-grade products; binding of gases harmful to climate ; and the reaction of these raw materials under mild conditions and with high selectivity, as is characteristic of fermentation processes. 

In the Clostridium species of bacteria the biotechnologists found the right fermentation agents. These bacteria are anaerobic (that is, they grow in the absence of oxygen) and are present everywhere in the world, particularly in the soil and in the digestive tract of higher organisms. It proved relatively easy to induce clostridia to produce C2 compounds such as ethanol and acetic acid. The Creavis researchers’ next goals were to produce longer chain alcohols and organic acids and to further develop the process to the point of continuous production. 

In both areas they have made great progress: Creavis’s biotechnology laboratories in Marl can now also produce C4 and C6 compounds (such as butanol and hexanol) with high selectivity by gas fermentation; for C2 compounds this is already possible in a continuous process. This is an innovation in the fermentation world and also the ideal precondition for interlinking the process with classical chemical production.

It is now planned to develop a continuous laboratory process for hexanol production in the three-year P2X project (under the Kopernikus initiative of the BMBF, the German Federal Ministry of Education and Research), which was initiated at the end of 2016. The culture media for gas fermentation with clostridia will also be further optimized in the project. The scientists see potential for further improving the cost efficiency of the process, especially for components such as trace elements and vitamins.  

The aim of the Kopernikus initiative, with total funding of €400 million and a scheduled time frame of 10 years, is to support the transition to renewable energy sources in Germany. Siemens is also represented in the initiative with a project for conversion of carbon dioxide (CO2) from industrial waste gases into syngas using power from renewable energy sources such as solar and wind. It is planned to link the technologies of the various Kopernikus projects from 2019 onward. But Siemens and Evonik had already decided at an earlier stage to join forces. 

In the Rheticus project, initiated in January 2018, they plan to combine CO2 electrolysis and gas fermentation in a kind of “artificial photosynthesis” and to scale up the process from the laboratory to a pilot plant to be built at Evonik in Marl. The project is expected to run for two years initially and is supported by the BMBF to the tune of €2.8 million. The linking of the two technologies offers the possibility of making power from renewable energies—which is usually generated decentrally and in widely fluctuating amounts—available at the point of use and for conversion to specialty chemicals. 

For instance, electrolysis that could be powered by solar energy produces syngas from CO2 and water; in the subsequent fermentation process, bacteria convert the syngas to butanol or hexanol, specialty chemicals that are required for specialty polymers or dietary supplements, for example. The process could replace conventional processes using fossil fuels and reduce CO2 pollution in the atmosphere. In this way Siemens and Evonik plan to make their contribution to the energy transition, in Germany and the world over. 

Nature Catalysis

Further scientific information about the Rheticus-project is available in the new online-only journal Nature Catalysis. It cover