Using cow waste to produce electricity has been done before, for example by using the methane released by this waste to power farm machinery. But now, researchers from Ohio State University (OSU) have found new ways to turn cow waste into elctricity. First, using a half-liter of fluid from the rumen -- the girst and largest chamber of a cow's stomach -- they were able to produce about 600 millivolts of electricity, or half the voltage needed to run a rechargeable AA battery. Then, they used real cow manure to power microbial fuel cells which produced between 300 and 400 millivolts of power. Even if it's too early to know if this electric cow power can be increased to higher levels, the researchers hope that one day farmers will be able to generate enough power for their farms.
Before going further, do you know what is the rumen? It is the first compartment of the stomach of ruminants, and it is there that cellulose is broken down by the action of bacteria. For more information, the University of Minnesota has set up a page about Ruminant Anatomy and Physiology, from which the illustration below has been picked (Credit: University of Minnesota).
The rumen (on the left side of the animal) is the largest of four compartments and is divided into several sacs. It can hold 25 gallons or more of material, depending on the size of the cow. Because of its size, the rumen acts as a storage or holding vat for feed. It is also a fermentation vat. A microbial population in the rumen digests or ferments feed eaten by the animal.
Now that your memory is refreshed about the rumen, let's look at how microorganisms found in cow waste might one day turn into sources of electricity.
Results [from the OSU study] 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 at OSU.]
The research showed how electricity can be created as the microorganisms in rumen fluid break down cellulose – a complex carbohydrate that is the primary component of the roughage that cows eat.
In another experiment, the researchers filled two sterilized glass chambers with cow manure to create microbial fuel cells.
The anode chamber was filled with rumen fluid and cellulose, which served as a food source for the microorganisms. Cellulose is plentiful on most farms, as harvesting usually leaves behind plenty of it in the form of crop residue in the fields.
The other chamber, the cathode, was filled with potassium ferricyanide, a chemical that acts as an oxidizing agent to round out the electrical circuit.
The results obtained, while modest, are promising.
[The output of the fuel cell] reached a consistent maximum of 0.58 volts. After about four days, the voltage fell to around 0.2 volts, at which time the researchers added fresh cellulose to bring the voltage back up to a higher level.
So it is possible to create electricity from cow waste, but what can farmers expect from this research work?
"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.
These findings were presented at the last American Chemical Society national meeting which was held in Washington, D.C. between August 28 and September 1, 2005.
The paper, named "Bioconversion of cellulose into electricity using rumen microorganisms as biocatalysts in a microbial fuel cell," is not currently online, but here is a link to the abstract.
Sources: Holly Wagner, Ohio State University, August 31, 2005; and various web sites
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