The Power of Bacteria: Microbial Fuel Cell Technology

This year’s British Science Week focusses on theme “Innovating for the future”, celebrating the diverse world of science, technology, engineering and maths.

Due to the ever growing importance of discovering more sustainable ways to produce energy, our scientists at BioLabtests took a closer look at existing research into bacteria that can harness the ability to produce electrical energy, the so called Microbial Fuel Cell (MFC) Technology.

Combating Climate Change

It is widely known that the use of unsustainable energy sources such as fossil fuels, coal and nuclear power are impacting climate change by contributing to global warming. When fossil fuels are burned, carbon dioxide and other greenhouse gases are released into our atmosphere and become trapped, which has the effect of heating up the earth. This in turn is causing dramatic weather changes and changes to our ecosystems. It is therefore suggested by many that we move to renewable resources that are not detrimental to our environment as one part of the solution.

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The idea of bacteria producing electrical energy was first by professor M. C. Potter in the 20^th century, who observed that E. coli had the ability to produce energy. However, this research did not gain a lot of traction until the production of Microbial Fuel Cells (MFC) ,and it was not until recently that MFC’s were used in wastewater treatment.

There are various types of MFCs that produce electricity in a variety of different mechanisms. Microbial fuel cells use the power of redox reactions to either reduce or oxidise organic compounds to produce an electrical current. Bacteria can transfer electrons to the anode via three different ways: through use of a soluble mediator, direct electron transfer through the use of cytochromes on the outer membrane, or finally pili can be used to transmit electrons.

Some microorganisms can reduce compounds and, in the process, donate electrons to the anode to create an electrical current. These microorganisms are able to oxidise organic compounds into carbon dioxide during this process. Other microorganisms perform oxidation reactions at the cathode. This in turn reduces organic compounds in the cathode chamber, for example they can reduce water to oxygen in aerobic conditions.

These redox reaction mechanisms have the potential to clean up greenhouse gasses that are polluting the atmosphere and use these compounds to produce energy. For example, research has shown the ability of bacteria to reduce carbon dioxide to methane or acetate. A species of bacteria named G. sulfurreducens has shown the potential to do this. This process would then be able to contribute to a reduction in the levels of carbon dioxide in the atmosphere.

Due to these successful redox reactions, MFC’s have shown promising results in certain real-life applications. One such application is the treatment of wastewater, using microorganisms to reduce organic waste compounds and purify wastewater, as well as producing small amounts of electricity in the process.

The Future Outlook

However, despite the success in wastewater treatment, Microbial Fuel Cells still do not present a viable option for large scale renewable energy sources for everyday lives due to the low energy output. Research has shown that if quicker electron transfer to the anode is achieved via nanotechnology, it could show potential to produce more energy at a larger scale. Research has also demonstrated that the use of carbon nanotubes (CNTs) could significantly amplify the electron transfer capability, which again shows great promise for future applications of MFC’s.

The climate change crisis is an ever-growing threat to our environment, which is why research into renewable energy sources has never been more pressing. Overall, Microbial Fuel Cells are a promising application, but more research is needed to harness their potential to make a significant impact in society.

References:

1. https://microbialcellfactories.biomedcentral.com/articles/10.1186/s12934-019-1087-z
2. https://climate.nasa.gov/effects/
3. https://royalsocietypublishing.org/doi/10.1098/rspb.1911.0073
4. https://www.sciencedirect.com/science/article/pii/B9780123850157000120#s0050
5. Qiao, C.M. Li, S.J. Bao, Q.L. Bao Carbon nanotube/polyaniline composite as anode material for microbial fuel cells J. Power Sources, 170 (2007), pp. 79-84