This is one of those self-explanatory ones, but here is an excerpt anyway:
The fuel cell is essentially a battery in which bacteria consume water-soluble brewing waste such as sugar, starch and alcohol.
The battery produces electricity plus clean water, said Prof. Jurg Keller, the university’s wastewater expert.
The complex technology harnesses the chemical energy that the bacteria releases from the organic material, converting it into electrical energy.
The 660-gallon fuel cell will be 250 times bigger than a prototype that has been operating at the university laboratory for three months