We're implementing a new compost arrangement: three bins instead of two. In the past, we used two -- a square wire frame, and a cylindrical black plastic. However, with being able to keep the compost pile over-winter, as well as the huge amount of winter rye at the beginning of the year going into the compost this spring, we exceeded our capacity.
So I decided to have us use three cylindrical plastic ones, because they are deformable, and so can be squeezed into the space allocated for composting. Three bins will facilitate turning. With just two bins, we were forced to turn one into the other even while adding new matter, or else not turning to keep new matter separate from more decomposed matter.
With three bins, one bin will be emtpy, and we can alternate turning one of the other compost piles into the empty bin, or even turn both. New matter will go into one of the piles, so that the older pile can more completely mature into good compost. When the older pile is ready for compost extraction, the newer pile will then become the older pile, and we will start a newer pile.