Engineers from Stanford University are turning “wired microbes” – naturally-occurring bacteria that produce electricity as they digest plant and animal material – into batteries.
Researchers say these microbial batteries could find their way into sewage treatment plants to help offset electricity use there, or be used to clean up ocean and lake dead zones where organic pollutants have accumulated and cut off oxygen to marine life. Their current prototype is about the size of a D-cell battery.
The microbes are so tiny that 100 of them lined up side-by-side would fit into the width of a human hair. The researchers refer to the white filaments in this scanning electron micrograph as the microbes‘“nanowires,” which connect to the carbon filaments of the battery.
While many research groups over the years have been working to harness the power of these microbes, creating an efficient and cost-effective way to employ them has proven difficult. This new battery can convert 30 percent of the energy in wastewater into electricity, which is on par with the most efficient solar cells on the market. But it uses silver oxide to move the electrons that are produced, which isn’t the cheapest ingredient.
“We demonstrated the principle using silver oxide, but silver is too expensive for use at large scale,” said study coauthor Yi Cui in a statement. “Though the search is underway for a more practical material, finding a substitute will take time.”
The study was published this week in PNAS.