Al Fin says that we’ve entered The Age of Sustainable Machines from DARPA:
A new type of autonomous robot will soon be loosed upon the land. A robot that forages, grazing on weeds and shrubbery, on rotten logs — even on dried out roadkill and other carcasses. This is DARPA’s EATR (Energetically Autonomous Tactical Robot), by RTI. It will be fueled by the Cyclone external combustion engine that can run on virtually any type of dry carbonaceous material.
I, for one, welcome our new robot overlords.