Research breakthrough in microbial fuel cell converts waste to energy

November 20 2008 / by Garry Golden
Category: Energy   Year: 2018   Rating: 4 Hot

What happened?
Researchers at the University of Minnesota-Twin Cities believe they have found a unique species of bacteria, Geobacter sulfurreducens, that can convert wastewater organic compounds into electricity using a low cost carbon (graphite) electrode.

“Other species of bacteria may produce just as many electrons as they oxidize available fuels, but their cell membranes act like an insulator for electron transport,” said Daniel Bond, a microbiologist at the University of Minnesota-Twin Cities. “With Geobacter, it’s the difference between a rickety one-land bridge and a modern 12-lane highway. The electrons pass easily through internal membranes and cell walls and hop onto the electrode.” As each “hop” requires them to travel about 10 Angstroms.

Geobacter has proteins that guide electrons all the way to the electrode. “This makes Geobacter unique in comparison to other bacteria,” Bond said. “Because of the distances involved, we know that multiple proteins are involved, which adds to the complexity and why we can’t just clone a gene into E. coli to do this.”

Why is this important to the future of energy?
While traditional batteries and fuel cells often use expensive precious-metal catalysts (e.g. platinum) to strip electrons off the fuel source to generate electricity, microbial fuel cells use biological agents to do the heavy work.

A microbial fuel cell based on Geobacter would require only an inexpensive form of carbon (graphite) to help the bacteria transfer electrons onto the surface of electrodes. This novel design of microbial fuel cells could be scaled to efficiently convert waste organic matter (e.g. sewage, food waste) to electricity.

What to watch

We are still in the early phases of developing scalable microbial fuel cells. But the potential is significant!

Food processing facilities and sewage treatment plants are often mentioned as potential early adopter environments.

Looking years ahead we can also imagine microbial fuel cells being used in home energy appliances. Delivering electricity from bio organic waste.

Research Next Steps & Biosensor applications

Materials gather from US NSF press release:

‘There are uses for remote power sources deep in the ocean for sensors and communications and what a Geobacter battery lacks in power, it makes up in simplicity and efficiency. “There are no moving parts, it just works,” Bond said.

“These bacteria exist to oxidize metal and pass electrons to whatever will take them,” he said. “With the graphite electrodes, we fool the Geobacter into thinking they have an unlimited supply of metal; instead of a few bites, they get an all-you-can eat buffet.”

The bacteria eat and grow and eat and grow but instead of getting fat like we do, they make additional copies of themselves. “The surface area of the electrode is limiting at some point. We don’t really know how many bacteria we can pack on.”

Another application for this mighty microbe is in waste-water treatment plants. The current technology requires a lot of oxygen, which gets expensive to pump in. Geobacter could help purify the water and simultaneously produce enough electricity to help pay the power bill. “Part of our lab is working to scale-up the technology, but most of the work focuses on ‘how’ and ‘why,’” Bond said.

When it comes to the inner workings of a bacterial cell, scientists have 100 years of knowledge to build on. But research on how the cells get electrons to the surface is only about 10-20 years old.

“We’re lucky Geobacter’s outer surface has an affinity for graphite. We’re working on making a better ‘lock-and-key’ connection,” Bond said. “Right now it just sort of fits.”

US National Science Foundation Press release

Image Credit: Geobacter Project at University of Massachussetts

Image Two Credit & Further Reading
Electricity Production by Geobacter sulfurreducens Attached to Electrodes by Daniel R. Bond and Derek R. Lovley, 2003

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