Beijing is a big city, and it generate a lot of empty plastic bottles. These are the guys that deal with this problem. They collect the empties, sort them, pack them into huge bags made from old rice sacks, load them into a truck, and take them someplace where they are undoubtedly paid a very small price per kilo of plastic. [NOTE: The "someplace" where they take all of the empty plastic bottles is probably a pretty impressive site. Mountains and mountains of plastic].