Composting from the 20th floor: In one of the gardens I work on we recycle every little bit of leaf, twig, flower, bug (yes even cockroaches), paper we throw into these round bins along with some water. After they are closed shut we give them a spin and let them sit in the hot sun. We do this once a week for one year. We emptied out the years worth of fresh hot compost last week and it was incredibly satisfying giving back this enormous 2 level terrace, what it had given up over the past year. Giving it back nutrients and healthy bacteria that stressed out - high up - container gardens really need. Every garden should have some area where a gardener can chuck the quick degrading refuse, on the ground it's easier to create a little vented box, up on the roof it's more difficult with drain issues. These suckers are cheap so if you're high up, go for it. Oh and check out the pic with the little drain cap, that's the base that drains out the liquid from the compost, creating a delicious compost tea.