Environment Technology

Organic Plastics Produced From Flue Gas and Electricity With Microbes

Microswimmer

The “BioElectroPlast” is a project funded by the Federal Ministry of Research to find ways to produce organic plastics efficiently and inexpensively. As part of this project, scientists at Karlsruhe Institute of Technology (KIT) are using microorganisms that produce polyhydroxybutyric acid from flue gas, air and renewable power. Microbial electrosynthesis, when optimized, could for example be used for the storage of power from regenerative sources in the form of chemical products, or for the future production of biofuel.

An increasing consumer demand for sustainable products increases the demand for organic plastics to be used for garbage bags, disposable cups or packaging. Professor Johannes Gescher of KIT’s Institute for Applied Biosciences (IAB) is head of the Applied Biology Group coordinating the “BioElectroPlast” project. Gescher focuses on a method to produce organic plastics at low costs while consuming a minimum of resources. The project also aims to use the greenhouse gas carbon dioxide (CO2) as a cheap and widely available raw material in the chain of values added. Applying renewable power is another goal of the project.

Microbial electrosynthesis is a relatively new technology first described by researchers in the USA six years ago. The process uses certain microorganisms growing on a cathode to bind CO2, and uses the cathode as the only energy and electron source. In contrast, a chemical process requires high pressures and temperatures, which result in a high energy input, as well as expensive catalysts. Up to now, microbial electrosynthesis has been used mainly to produce salts of acetic acid (acetates).

Biologist Johannes Eberhard Reiner, KIT, with the reactors for microbial electro-synthesis. (Image Credit: Constanze Zacharias)
Biologist Johannes Eberhard Reiner with the reactors for microbial electro-synthesis. (Image Credit: Constanze Zacharias)

Johannes Eberhard Reiner of the IAB explained that the process has been optimized so that the microorganisms are supplied with more energy for the production of molecules of higher complexity such as polymers. Air is mixed with the CO2 and the microorganisms then uses the oxygen as an electron acceptor. The process is comparable to human breathing, where oxygen also serves as electron acceptor. In human beings however, electrons are released by the metabolizing of our food in the cells and do not come from a cathode. They are then transferred to the oxygen for energy production.

The scientists use a newly isolated microorganism that permanently regenerates itself as a biocatalyst. Flue gas is used as a CO2 source and the concentration of this greenhouse gas is thus reduced.  This also means that other sources of organic carbon, such as agricultural products that are usually applied as biotechnological substrates, are no longer required. This avoids competition with food and feed production. Finally, regenerative sources are used to supply the electric power needed for the “Bio-ElectroPlast” process.

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