Microbial Fuel Cells Could Power the Future

Published on 22 Aug, 2017

Technologies that utilize microbial metabolisms to break down organic/inorganic matter in order to produce an electrical current could be a promising solution for both power generation and waste management in the future.

A fuel cell is basically a device that converts chemical energy from a fuel into electricity via a chemical reaction.

Similarly, Microbial Fuel Cells (MFCs) are electrochemical devices that use the metabolic activity of microorganisms to oxidize fuels, and thereby, generate current by direct or mediated electron transfer to electrodes.

The MFC utilizes microbial metabolisms to produce an electrical current from degraded organic/inorganic matter. Microorganisms convert the energy stored in these biodegradable organic and inorganic compounds to electrical energy. Degradation of matter results in the release of electrons, which are then transferred to a cathode, where they combine with protons and electron acceptors that ultimately results in a reduction reaction.

The most prevalent mechanisms through which fuel cells work are alkaline, carbonate, phosphoric acid, solid oxide, and polymer electrolyte membrane.

MFCs are Considered as a Next-generation Energy Source

The main areas of application for MFCs have been waste treatment and electricity generation. Researchers have attempted to use microbes from the genera Geobacter, Saccharomyces, Desulfurmonas, and Escherichia for power generation.

Cambrian Innovation is working with the US army to test an MFC that could turn 2,250 liters of sewage into clean water and generate enough electricity to power itself.

Similarly, under the Living Architecture research project, scientists are developing building materials that can produce electricity. Accordingly, researchers have programmed synthetic microorganisms and inserted them into an MFC, which is then placed inside ceramic blocks. These MFCs, which are effectively alive, produce positive and negative charges. Researchers have also used MFC-laden bricks to power lights in selected urinals at the Glastonbury music festival.

MFCs Have Other Applications Too

MFCs have been used to generate hydrogen gas, wherein the anodic potential is increased with additional voltage. MFC’s have also been employed as biosensors for pollutant analysis and acid and alkali production.

MFCs are suitable for powering electrochemical sensors and small telemetry systems to transmit signals to remote receivers. Microbes have been used as biological oxygen demand sensors. However, MFC’s have been observed to have better operational sustainability and reproducibility, with an operational lifetime of almost five years.

MFCs Need to Overcome a Few Challenges to Reach its Full Potential

MFC development is still in its nascent stage, and the power density that current systems achieve needs further improvement. Researchers are still fine-tuning the process’ efficiencies, especially in areas that involve “scaling up” power generation through higher volumes of substrates. MFC’s application in wastewater treatment also depends on significant variables such as the concentration and biodegradability of organic matter, wastewater temperature, and the presence of toxic chemicals.

In addition to reliability and scalability, MFC systems also need to be simplified in order to make them more cost-effective, a factor that’s likely to affect adoption in an era when power generated through Solar and Wind are on par with coal. The anodic materials currently used in MFC tech such as  graphite foams, reticulated vitreous carbon, and graphite, are far too expensive to be viable on a large scale.  Additionally, the Anode acts not only as a conductor but also as a bacteria carrier. Hence, material factors such as surface roughness, good biocompatibility, and efficient electron transfer between bacteria and the electrode surface are other key factors that need to be addressed in order to promote bio catalytic activity.

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