ONR’s microbial fuel cell generates electricity from mud

It is estimated there are approximately five nonillion (that’s 5x10 to the power of 30) bacteria on Earth, and although they generally get a bad rap, there are actually many beneficial bacteria that are vital to life on our planet. As we’ve seen previously, scientists are now looking to harness bacteria to produce electricity through microbial fuel cells. These microbial fuel cells (MFCs) convert chemical energy to electrical energy to offer a clean, efficient and reliable alternative to batteries and other environmentally harmful fuels. Recognizing this potential the Office of Naval Research (ONR) has developed an MFC that could revolutionize naval energy use by converting decomposed marine organisms into electricity.

These fuel cells convert naturally occurring fuels and oxidants in the marine environment into electricity making them a viable power source for long-term operation of autonomous underwater unmanned vehicles, in-water sensors, and devices used for surveillance and monitoring the ocean environment.

"Think of it as a battery that runs on mud," ONR Program Manager Dr. Linda Chrisey said. "They are sustainable, environmentally friendly and don't involve hazardous reactants like a regular battery might because they use the natural carbon in the marine environment. For example, we are working on a 4-foot long autonomous underwater vehicle that will settle on the seafloor and recharge its batteries using this fuel cell approach. We are already able to power many types of sensors using microbial fuel cells."

Dr. Leonard Tender, a research chemist in the Center for Bio/Molecular Science and Engineering at the Naval Research Laboratory (NRL), working with scientists from the University of Massachusetts at Amherst, started to investigate electricity-generating microorganisms. The most promising, called Geobacter, was discovered in the Potomac River immediately downstream of NRL.

Geobacter, which helped the “Electric Microbe” make it onto Time magazine’s “Top 50 Inventions for 2009” list, has tiny hairlike extensions called pili that it uses to generate electricity from mud and wastewater. Researchers have developed a strain of Geobacter that is eight times more efficient than other strains at producing power. With its powerful return of clean energy it could reduce carbon emissions in the environment and change the way we fuel our vehicles and supply power to our homes.

"Essentially, they could go on for years without any kind of battery replacement," Chrisey said. For this reason, Navy researchers at the Space and Naval Warfare Systems Center (SPAWAR) Pacific are using fuel cell-powered devices to track Pacific-endangered green sea turtles.

"The device is light, efficient and environmentally friendly," said Bart Chadwick, SPAWAR's Head of Environmental Sciences Branch. "The technology is helping track sea turtle populations, if they are feeding near Navy shorefront facilities, which informs Navy decision-making on port operations or construction."

ONR will highlight the microbial fuel cell as part of a showcase of its energy research initiatives for an Earth Day event on April 22 at the Pentagon.