Cows Show Promise as Powerplants

Photo: A brown cow

Results showed that the microbes in about a half a liter of rumen fluid – fermented, liquefied feed extracted from the rumen, the largest chamber of a cow's stomach – produced about 600 millivolts of electricity. That's about half the voltage needed to run one rechargeable AA-sized battery, said Ann Christy, an associate professor of food, agricultural and biological engineering at Ohio State University.

While rumen fluid itself won't be used as an energy source, some of the microorganisms found in the fluid are also found in cow dung, which may prove to be a good source for generating electricity. In fact, in a related experiment, the researchers used cow manure directly to create energy for a fuel cell.

Using cow dung as an energy source isn't a new idea – some farmers already use the methane released by livestock waste to power machinery and lights. But converting methane into electricity requires costly equipment.

This research showed how electricity can be created as the microorganisms in rumen fluid break down cellulose. “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.; Source: Ohio State University