Sewage treatment plants represent an interesting source of electricity. Oregon State University (OSU) have studied and developed a new type of coating that, if applied on the positive electrodes of microbial electrochemical cells used in such plants would raise the electricity production by about 20 times.
They coated graphite anodes with a nanoparticle layer of gold. Other experiments used palladium, but with less success. The method is believed to be expensive, though, and that’s why the same researchers looked for and found another metal that they could cover the electrodes with: iron. For some types of bacteria, they believe, iron nanoparticles could produce the same results as gold.
“This is an important step toward our goal,” said Frank Chaplen, an associate professor of biological and ecological engineering. “We still need some improvements in design of the cathode chamber, and a better understanding of the interaction between different microbial species. But the new approach is clearly producing more electricity.”
The process of harvesting the electricity from sewage works with the help of bacteria that form a thin film floating over the water in the anode chamber. The bacteria consume the nutrients in the sewage and grow, and in the meanwhile they also release electrons. The method is good because it recycles stuff and the electricity is very cheap to make.