11th July 2012
A new biofuel production process is claimed to produce more than 20 times as much energy than existing methods.
A team at Michigan State University has developed bioelectrochemical systems known as microbial electrolysis cells, or MECs, using bacteria to break down and ferment agricultural waste into ethanol.
While similar microbial fuel cells have been investigated before, the maximum energy recovery from corn stover, a common raw material for biofuel, is only about 3.5 percent.
But, thanks to the use of a second bacterium, the MSU platform averages 35 to 40 percent, just from the fermentation process – and adds a second stage that doubles this figure.
“This is because the fermentative bacterium was carefully selected to degrade and ferment agricultural wastes into ethanol efficiently and to produce byproducts that could be metabolized by the electricity-producing bacterium,” says MSU microbiol;ogist Gemma Reguera.
“By removing the waste products of fermentation, the growth and metabolism of the fermentative bacterium also was stimulated. Basically, each step we take is custom-designed to be optimal.”
The second bacterium, Geobacter sulfurreducens, generates electricity – although this isn’t harvested as an output. Instead, it’s used to generate hydrogen, to increase the energy recovery process even more.
“When the MEC generates hydrogen, it actually doubles the energy recoveries,” says Reguera. “We increased energy recovery to 73 percent. So the potential is definitely there to make this platform attractive for processing agricultural wastes.”