Researchers at Michigan Technological University are developing a microbial fuel cell system that could help underwater sensors stay submerged longer by generating electricity from organic matter already present in seawater.

The project is part of the Defense Advanced Research Projects Agency’s BioLogical Undersea Energy, or BLUE, program, which aims to create self-refueling underwater power systems for long-endurance ocean sensors. Current underwater monitoring systems mostly rely on batteries that require expensive retrieval and replacement operations.

The Michigan Tech-led team is testing microbial fuel cells, or MFCs, that use bacteria to convert dissolved organic material and microscopic marine biomass into electrical current. Researchers say the technology could eventually support naval defense sensors, ecological monitoring systems, and underwater acoustic networks.

“There are increasing deployments of all kinds of sensors in the marine environment for observing ecological conditions, organism migrations, and acoustics relevant to naval defense,” said Amy Marcarelli, distinguished professor of biological sciences at Michigan Tech.

The researchers have already completed a 30-day underwater deployment in Chesapeake Bay, where prototype systems continued producing electricity while fully submerged.

Microbes generate ocean power

Microbial fuel cells work by using bacteria that naturally transfer electrons during metabolism. In the system designed by the Michigan Tech team, those electrons move between an anode and cathode, creating usable electrical current.

One of the main engineering challenges is that ocean water contains far less organic material than environments where microbial fuel cells are commonly used, such as wastewater plants. Marine environments also contain high oxygen levels that interfere with the microbes’ energy-generation process.

To improve performance, the researchers used granulated activated carbon inside tubular fuel cells. The material concentrates organic matter and provides a surface where microbes can form biofilms and continue generating electricity even in oxygen-rich conditions.

“The basic idea is that microbes move electrons around during their metabolic processes,” said Marcarelli. “In a microbial fuel cell, those processes transfer electrons from an anode to a cathode, creating an electrical current we can harness.”

Researchers also redesigned the system to improve energy efficiency and simplify deployment. Newer versions use modular, stackable units with individual pumps and control boards.

The latest prototypes were tested in Galveston Bay, where three out of four units reportedly generated power successfully during underwater trials.

Sensors stay submerged

The system is designed to operate fully underwater without depending on surface wave energy or human maintenance. Researchers say that could allow ocean sensors to remain active for longer periods in remote environments.

The team also built predictive models using remote sensing and environmental data to estimate where microbial fuel cells could generate enough power across global coastal regions.

“What we’re really doing on our end is combining remote sensing assets, field data, experimental lab data and then actual MFC deployment experiments,” said Michael Sayers, chief research scientist at the Michigan Tech Research Institute.

Researchers are now preparing a larger deployment involving 10 microbial fuel cells in Chesapeake Bay. The goal is to study long-term performance and estimate whether the systems could eventually support year-long underwater operations.