recycling
Visitors often ask, empty water bottle in hand, "is there recycling here?"
And the answer is No. And Yes.
No, no one melts old bottles into new ones. But yes, everything gets re-used.
Bottles are useful for storing water or cooking oil or whatever. Why would you not use the free ones that muzungus throw away?
Kids outside of Kigali have figured out that if they run alongside cars and ask for empty bottles, they often get them. An easy thing to ask for.
Really, it's just a low-tech, highly efficient method of recycling.