“Think of it as a battery that runs on mud,” says the U.S. Office of Naval Research, and there in a nutshell is the concept behind the Navy’s new microbial fuel cell. The Navy has been using small lightweight microbial fuel cells to power sensors (to track sea turtles, for example) and now its goal is to develop one that is powerful enough to steer a small robotic watercraft.
In a microbial fuel cell, organisms feed on available nutrients and generate an electric current as they metabolize the food. The Navy is working with researchers at the University of Massachusetts on a microbe called Geobacter, which is the most promising in terms of its efficiency at generating electricity. Strains found in the wild have demonstrated a knack for converting nutrients in mud and wastewater into electrical current, and researchers have developed a new strain that is eight times more efficient than others.