Wastewater contains an elevated amount of chemical energy in the form of organic contaminants. In order to make use of this energy, researchers from around the world study ways to recover it in the form of hydrogen, a process which efficiently eliminates organic matter from wastewater. It not only reduces the amount of energy needed during the process, it also obtains energy from the produced hydrogen. The key to achieve this is what is known as microbial electrolysis cells (MEC). What is needed is a very special type of bacteria, exoelectrogenic bacteria, capable of oxidising organic material and generating electricity which in turn produces hydrogen. These cells only need a bit of added voltage, much less than what is used for water electrolysis, and which is recovered with the hydrogen, thereby generating clean energy.