Sorting Robot

In my book I write about bots that comb the streets for trash and discarded goods.  They act as cleaners, recyclers, and they also hook into nearby buildings to share or get electricity (depending on who has the surplus).  I can also see them coming to our homes and discarding something that has broken or is unwanted.  Let's say your computer is out of date and you're ready to trade it in.  If we're still operating in a scarce society, subscribing to this bot's service could grant significant discounts on your next computer, reusing the rare metals and other expensive components.  If we're in a post-scarcity world then this will just help minimize waste and serve as an example of how technology can breed efficiency and sustain a (nearly) harmless system for us.