microbial fuel cellGenerating electricity through bacteria in waste water.
Check out this explanation from Penn State – Microbial Fuel Cell Page

Renewable and clean forms of energy are one of society’s greatest needs.  At the same time, 2 billion people in the world lack adequate sanitation and the economic means to afford it.  In this research, we are working to address both of these human needs. Energy costs are an important factor in wastewater treatment. In the USA, for example, 5% of electricity we produce is used for the water and wastewater infrastructure (all aspects, including pumping, treatment, etc.), with 1.5% used for wastewater treatment alone.

Microbial fuel cells (MFCs) represent a completely new method of renewable energy recovery: the direct conversion of organic matter to electricity using bacteria. While this sounds more like science fiction than science, it has been known for many years that bacteria could be used to generate electricity.  However, expensive and toxic chemicals were needed to shuttle electrons from the bacteria to the electrode and purified chemicals (such as glucose) were needed for the bacteria to grow on. We now know that we can make electricity using any biodegradable material– even wastewater– and that we don’t have to add any special chemicals if we use bacteria already present in the wastewater. While some iron-reducing bacteria, such asShewanella putrefacians and Geobacter metallireducens [they reduce Fe(III) to Fe(II)], can be used to make electricity, there are many other bacteria already present in wastewater that can do this.

How does a microbial fuel cell work? When bacteria are placed in the anode chamber of a specially-designed fuel cell that is free of oxygen, they attach to an electrode.  Because they do not have oxygen, they must transfer the electrons that they obtain from consumption (oxidation) of their food somewhere else than to oxygen– they transfer them to the electrode. In a MFC these electrons therefore go to the anode, while the counter electrode (the cathode) is exposed to oxygen. At the cathode the electrons, oxygen and protons combine to form only water.  The two electrodes are at different potentials (about 0.5 V), creating a bio-batter (if the system is not refilled) or a fuel cell (if we constantly put in new food or “fuel” for the bacteria).

Look closely at microbial fuel cells and see how they work to send off electrons to produce electricity. It is an interesting study about a future renewable energy technology.