Self-Sustaining Bacteria-Fueled Power Cell Holds Promise for Future Energy Needs

It is possible that instead of coal, oil, or even solar energy, self-sustaining bacterial fuel cells could provide power for the future.

A team of scientists at Binghamton University, State University of New York have developed the next step in microbial fuel cells (MFCs) with the principal micro-scale self-sustaining cell, which produced power continuously for 13 days through symbiotic relations of two types of bacteria.

This concept of creating electricity through synergistic cooperation is not new. However, much of this work is still in its nascent stages.

Seokheun Choi, Assistant Professor, Binghamton University

Choi is one of the co-authors of "Self-sustaining, solar-driven bioelectricity generation in micro-sized microbial fuel cell using co-culture of heterotrophic and photosynthetic bacteria," along with PhD candidate Lin Liu.

"The evolution of this technology will require additional exploration, but we, for the first time, realized this conceptual idea in a micro-scale device," Choi said.

In a cell chamber approximately one-fifth the size of a teaspoon - 90 μL - the research team placed a mixed culture of heterotrophic and phototrophic bacteria. Phototrophic bacteria uses carbon dioxide, sunlight, and water to create its own energy, while heterotrophic bacteria has to "feed" on available organic matter or phototrophic bacteria to live – imagine cows grazing in a grassy field.

When sunlight reached the cell, an initial dose of "food" was introduced into the chamber to trigger growth of the heterotrophic bacteria. Through cellular respiration, the heterotrophic bacteria generated carbon dioxide waste, which was used by the phototrophic bacteria to resume the symbiotic cycle.

After that cycle was fixed, the team stopped adding extra "food" sources for the heterophic bacteria, and enough phototrophic bacteria was there to withstand the metabolic processes of the heterophic bacteria. Those metabolic processes produced an electrical current - 8 μA per square centimeter of cell - for 13 continuous days. The power was approximately 70 times more than current generated by just phototrophic bacteria.

Heterotrophic bacteria-based fuel cells generate higher power, while photosynthetic microbial fuel cells provide self-sustainability. This is the best of both worlds, thus far.

Seokheun Choi, Assistant Professor, Binghamton University

The innovation is promising, but it is a primary step in the advancement of bacteria-generated power. Generally, the tiny size of the cells permits a short start-up time and small electrical resistances to be overcome.

However, a typical 42" high-definition TV takes around half an amp of electrical current to operate which would, hypothetically, require approximately 62,500 cells from the experiment. In reality, these cells will be used to offer power in dangerous or remote locations for low-power items like infrastructure diagnostic sensors and health monitors.

There are some challenges of using this technique. Balancing both microorganisms' growth to maximize the device performance and the need to make sure that this closed system will permanently generate power without additional maintenance are two we have found. Long-term experiments are needed.

Seokheun Choi, Assistant Professor, Binghamton University

The current research is the latest in a string of battery-related and microbial-based power studies Choi has been involved in. Last spring for the first time ever, the scientists connected nine biological-solar (bio-solar) cells into a functioning bio-solar panel.

The phototrophic bacteria were used in that experiment. That panel produced the most wattage of any current small-scale bio-solar cells: 5.59 µW. Choi has also designed a microbe-based battery that can use human saliva as a power source, an origami-inspired microbe-based paper battery, battery designs inspired by Japanese ninja throwing stars, and a battery that can be printed on paper.

The research paper will be published in the Journal of Power Sources on April 30.