The researchers collected the fluid through a cannula, a surgically implanted tube that leads directly from the cow's hide into its rumen. The cow used in the study ate a normal diet.
The researchers filled each of two sterilized glass chambers with strained rumen fluid to create the microbial fuel cell. Each chamber was about a foot high and about 6 inches in diameter.
The chambers were separated by a special material that allowed protons to move from the negative (anode) chamber into the positive (cathode) chamber. This movement of protons, along with the movement of electrons across the resistor and wire that connects the two electrodes, creates electrical current.
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.
Two small pieces of plain graphite served as the fuel cell's electrodes (an electrode draws and emits electrical charge.) A piece of graphite was placed in each chamber. The researchers used a meter to measure the output of the fuel cell.
That output 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.
"While that's a very small amount of voltage, the results show that it is possible to create electricity from cow waste," Chris
Source:Ohio State University