If you don't have a Labrador roaming your kitchen looking for bits of food (as I do), this cleaning robot may be the next best thing. The Bio Clean is a concept design by Kyuho Song that vacuums up dust and food waste, converting the latter into biofuel to power itself. As Yanko Design notes, "the details are sketchy but the logic is sound."
One problem with biofuels is their production leads to the razing of grassland, rainforests, savannas and other ecosystems. Not an issue with the Bio Clean. The Roomba-like robot may not power a Navy strike force, but it keeps itself going, meaning a little less electricity needs to be produced from potentially unclean sources.
While there aren't any notes on how the fuel production would work, the idea is now out there. It's just a matter of getting the science to follow; I'm sure someone can figure it out.