Self-sustaining bacterial fuel cells may be the power the future instead of coal, oil, or even solar energy.

The next step in microbial fuel cells (MFCs), the first micro scale self-sustaining cell, has been developed by scientists at Binghamton University, State University of New York. The cell generated power through symbiotic interactions of two types of bacteria for 13 days.

Seokheun Choi, a Science Assistant Professor at Binghamton University Electrical and Computer noted that the concept of creating electricity through synergistic cooperation is not new. Much of this work is however still in its embryonic stages. Choi, together with PhD candidate Lin Liu are the co-authors of the paper “Self-sustaining, solar driven bioelectricity generation in micro sized microbial fuel cell using co-culture of heterotrophic and photosynthetic bacteria” that was published in the Journal of Power Sources.

Choi added that although the evolution of this technology will require additional exploration, they have actualized this conceptual idea in a micro-scale device for the first time.

The researchers placed a mixed culture of heterotrophic and phototrophic bacteria in a cell chamber about one-fifth the size of a teaspoon (90 microliters). Heterotrophic bacteria must feed on organic matter that is provided or phototrophic bacteria to survive, whereas phototrophic bacteria use sunlight, carbon dioxide and water to make its own energy.

To stimulate growth of the heterotrophic bacteria, an initial dose of food was added to the chamber while the cell was exposed to sunlight. The heterotrophic bacteria produced carbon dioxide waste through cellular respiration. The phototrophic bacteria then used this carbon dioxide waste to kick-start the symbiotic cycle.

Once the cycle was stable, the team stopped adding additional food sources for the heterotrophic bacteria. As there was enough phototrophic bacteria to sustain the metabolic processes of the heterotrophic bacteria, the metabolic processes generated an electrical current of eight micro amps per square centimeter of cell. This cycle was sustained without outside interference for 13 days. The power produced was about 70 times greater than what could be delivered by phototrophic bacteria on their own.

Choi explained that thus far, this is the best of both worlds – photosynthetic microbial fuel cells provide self-sustainability while fuel cells based on heterotrophic bacteria generate higher power.

Although the breakthrough is promising, it is a very early step in the development of power generated by bacteria. The small size of the cells allows for small electrical resistances to overcome and a short startup time. A common, 42″ high definition television needs about half an amp of electrical power to function. This would theoretically mean that it requires about 62,500 cells from the experiment. These cells will rather be used to supply power in dangerous or remote locations for low power devices such as infrastructure diagnostic sensors and health monitors.









Choi explained that using this technique has some inherent challenges. The first is the need to ensure that this closed system will generate power permanently without needing additional maintenance, while the second is to balance the growth of both microorganisms to maximize the device’s performance. He added that long-term experiments are needed to iron out these challenges.

Choi has worked on a series of microbial based and battery related power studies, of which the current work is the latest. Researchers connected nine biological solar cells (bio solar) into a working bio solar panel for the first time ever last spring. Only phototrophic bacteria were used in that experiment. That panel generated 5.59 microwatts – the most power produced by any existing small-scale bio solar cells.

Choi has also developed: