Afaik we can throw bacteria at it and then use something similar to fuel cells to digest their products. There are already robots that you can feed by placing a

Afaik we can throw bacteria at it and then use something similar to fuel cells to digest their products. There are already robots that you can feed by placing apple slices at the right location on them. Methane fuel cells driven by methane from anaerobic bacteria is not hard. The digestion is used for a long time in waste water treatment, and the fuel cells are good enough to be useful for a few years now. It's just that those fuel cells are _expensive_, and the system power density is quite meager, all considered. It also lacks an immune system that keeps the bacteria in check, so it's not that hard to poison (still quite resilient though).