Ecobot III eats food and needs to poop

Who would have thought that a robot might actually consume actual food and generate organic instead of nuclear waste? That's what a group of researchers at the University of Bristol are doing, working on robots which draw power by digesting food. The Ecobot III is the culmination of their work so far, as it feeds on processed sewage thanks to its 48 microbial food cells. Microbes within will extract energy from the food by digesting it, while the robot will extract some of it by harvesting the electrons put off by the microbes. There was enough energy extracted for the robot to move around, not to mention returning to feed and purge when necessary.