( ty said. Putting a couple of these ...)It's electric: Cows show promise as powerplants

"Putting a couple of these fuel cells together should generate enough power to run a rechargeable double-A battery," Rismani-Yazdi said.

In related work done in Christy's lab, she and Rismani-Yazdi, along with a number of undergraduate students, used actual cow manure to power a microbial fuel cell. These individual cells produced between 300 and 400 millivolts.

"The students put a few of these cells together and were able to fuel their rechargeable batteries over and over again," Christy said.

In that work, the researchers didn't need to use cellulose to feed microbes, as some plant material passes undigested through a cow.

"We've run some of these trials well over 30 days without a decrease in the voltage output," Christy said. "Both studies suggest that cow waste is a promising fuel source. It's cheap and plentiful, and it may someday be a useful source of sustainable energy in developing parts of the world."

While the source of energy for the fuel cell used in these studies is somewhat unique, microbial fuel cells aren't a new idea; other scientists have produced electricity from a handful of specific microbes and also from effluent from municipal wastewater.

"Although it's too early to tell if this kind of fuel cell can produce significantly more electricity, the fact that the rumen fluid worked in our study means that there are additional electricity-producing microbes that we have yet to identify," Christy said.

"The hope is that one day livestock farmers could use their farm's livestock waste lagoon as a huge fuel cell and generate enough power for their operation," Rismani-Yazdi said.