Project seeks to improve the efficiency of microbial fuel cells

In MFCs, electrons from microbial metabolism flow from bacteria toward an anode then on through an external circuit, finally converting oxygen into water at the cathode and closing the cycle.

Susan Rosser, principal investigator on the EPSRC-funded project, told The Engineer: ‘Bacteria use carbon when they metabolise and they produce electrons as a by-product.’

‘Certain strains of bacteria have the capability to transfer those electrons to electrodes, which can produce a current,’ she explained.

Rosser claimed that the power generated by MFCs is still too low for practical application despite work being done to improve this situation, such as altering the hardware of microbial fuel cells or changing the electrode material.

‘We’re taking a biological engineering approach where we’re using synthetic biology in order to engineer the bacteria to be more productive,’ Rosser added.

There are a variety of ways through which bacteria transfer electrons to electrodes and Rosser hopes to pinpoint and further understand these in her research.

‘Certain bacteria create nanowires and electrons are transferred along these, while other bacterium transfer electrons through direct contact with the electrode,’ she said.

‘In addition, there are types of bacteria that create electron mediator compounds that travel back and forth between the bacteria to the electrode and dump the electrons at the electrode,’ added Rosser.

She hopes to further understand these methods and engineer bacteria that have combined ways of transferring electrons.

MFCs have the potential to generate renewable electricity from a vast array of carbon sources, such as wastewater, agricultural by-products and industrial pollutants.

Rosser said: ‘There are huge potential applications. We’re hoping to use pollutants as carbon sources. This would mean that pollutants would be captured by an MFC placed at the end of a pipe instead of being released into the environment.’

MFCs also have the potential to power remote environmental sensors that currently rely on batteries that have to be changed when they run out.

In addition, NASA has shown an interest in MFC technology, which could be used in conjunction with human waste produced by astronauts.