PULLMAN, Wash. – In a hallway in a building at the engineering end of campus, a string of small, red LED lights blink unobtrusively, powered by a bucket of muddy water.Dedicated crews of microscopic bacteria in the mud generate electricity by doing what bacteria do best: eating.
“The microbes eat organic material and transfer electrons to an anode buried in the sediment,” said Timothy Ewing, the Ph.D. student who helped put together the microbial fuel cell powering the lights. “The electrons then flow through an external circuit to the cathode up near the surface of the water where they are transferred to oxygen, completing this part of the electricity generating process.”
The microbes are quick eaters, too. Food is at their cell-tips so they can produce electrons easily.
“The microbes eat organic material and transfer electrons to an anode buried in the sediment,” said Timothy Ewing, the Ph.D. student who helped put together the microbial fuel cell powering the lights. “The electrons then flow through an external circuit to the cathode up near the surface of the water where they are transferred to oxygen, completing this part of the electricity generating process.”
The microbes are quick eaters, too. Food is at their cell-tips so they can produce electrons easily.
For this simple application of blinking a few lights, a power management system uses a boost converter to store energy in a capacitor until there is enough power to activate the lights. The 500-600 milliseconds between blinks is the amount of time it takes the microbes to generate enough energy.
National Science Foundation funds outreach
Ewing and his advisor, associate professor Haluk Beyenal, set up the microbial fuel cell (MFC) in the hallway of Dana Hall as a form of outreach, hoping the blinking lights would catch the eyes of passing students.
The effort also included a two-semester laboratory research class in chemical engineering led by David Thiessen and advised by Beyenal. The course taught students how to build and test different aspects of microbial fuel cells.
Thiessen is an assistant research professor in physics and astronomy. Beyenal’s 2010 National Science Foundation CAREER award helped fund the outreach.
Low maintenance energy source
MFCs are unique forms of alternative energy since they are low maintenance. The fuel cell in Dana will stop powering the lights when the microbes run out of organic material to consume; but when placed somewhere like a waste water treatment plant, MFCs can run continuously.
Researchers can simulate those continuous conditions in the lab by using river or waste treatment water and replenishing organic materials periodically. For example, systems that Beyenal set up in his lab four years ago using river water and wastewater are still generating energy today.
Researchers can simulate those continuous conditions in the lab by using river or waste treatment water and replenishing organic materials periodically. For example, systems that Beyenal set up in his lab four years ago using river water and wastewater are still generating energy today.
Alternative energies add up
Although it is not yet practical to consider MFCs a significant alternative energy source, they can be used to generate power at remote locations where needed. For example, Ewing is researching the use of MFCs to power machines that aerate water in treatment plants.
His research specifically focuses on how to efficiently capture electrons to develop useful applications of MFCs. This work was funded by Beyenal’s NSF CAREER award as well.
“It is important to have an awareness of all alternative energies,” Ewing said. “We may not be able to power the world with this one energy source, but if we can start taking things off the grid little by little, then we’ll be saving energy.”