Popular Science ran a most interesting article about two robotic devices that consume living matter and convert it into energy to power themselves.
The first robot known as EcoBot II built by Bristol Robotics Laboratory digests organic material (flies) using a microbial fuel cell (a tank like stomach that digests and produces energy from the digesting matter). Eight digested flies produce enough power to move the robot seven feet.
The second robot known as EATR is a car like robot that is able to use its saw and arm to chop down twigs, and dead tree branches and insert them into its combustion chamber where they are converted to energy. This robot is able to get about 100 miles per 150 pounds of vegetation and is programmed to recognize and retrieve its own fuel source. Advanced programming restricts the robot into only recognizing plant matter as a harvest-able fuel source, so it won’t try to hack at the nearest living animal and try to use it as fuel.
Self powered machines that fuel themselves are not only possible but technology is rapidly becoming more advanced and affordable that within the next fifteen to twenty years many machines may exist on bio fuels and can renew their own power sources by “feeding” themselves.