you don't even need a bin. A spot in the yard (heck, even IN the turtle pen) where you pile up leaves and dirt, and occasionally insert some vegetable scraps is all you need. Grass clippings work well too. Look up "vermicomposting" on the web to find simple ways of doing it. Worms you can order online are easily found this way. I order once a year (and am holding off for another month on my next pen expansion to make this year's order) but each year I just look online and find a worm farm and order earthworms delivered to my front door.