US battery boffins build cow dung fuel cell

Cow dung has provided human beings with fuel for millennia. Now, thanks to research conducted by Ohio State University, it could become the foundation for future notebook power plants.

To be fair, it's not the manure per se that's the power source, but the bacteria crawling through it.

According to researcher Ann Christy, Associate Professor of food, agricultural and biological engineering, the bugs in 0.5l of bovine gastric juices can generate 600mV - half the voltage needed to power up a AA-sized rechargeable battery. The voltage arises from electrons freed when the bacteria digest cellulose in the cow's gut.

Since it's easier to extract the bacteria after they have left the cow's intestinal tract, fecal matter looks like a far better source that the stomach fluid.

Indeed, the Ohio State researchers ran a dung-packed fuel cell for "well over 30 days without a decrease in the voltage output", said co-researcher and Ohio State graduate student Hamid Rismani-Yazdi. The cell generated 300-400mV.

“While that's a very small amount of voltage, the results show that it is possible to create electricity from cow waste,” Christy said.

The downside is size: the experimental fuel cells comprised two cylinders each 30cm high and 15cm in diameter. There's also the problem of how much power the bugs generate.

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