Here’s an interesting news article involving water quality. Engineers from Stanford are developing techniques to harness electricity from microbes as they work to clean human sewage. Basically, by inserting positive and negative electrodes into wasterwater, the researchers “fish for electrons”. During reactions that degrade organic molecules, microbes cluster around the negative electrode and produce electrons, which are then captured by the positive electrode.

We’ve known about these energetic biodegradation reactions for many years, but only now are techniques being developed to efficiently harness the electricity. The researchers estimate that about 30 percent of the potential energy in the wastewater can be harnessed, about the same rate as commercially available solar panels. While there is much less potential energy available from these reactions compared to solar radiation, the added value is that the wastewater is being cleaned, or “reclaimed,” by these reactions, which means some of the energy currently being consumed to treat wastewater might be offset.

The study was published in the Proceedings of the National Academy of Sciences (PNAS) on 16 September 2013: Microbial battery for efficient energy recovery. Xing Xie, Meng Ye, Po-Chun Hsu, Nian Liu, Craig S. Criddle, and Yi Cui; doi:10.1073/pnas.1307327110