I make my own soil for container gardening, and a critical component is poop. I feed my Eisenia fetida worms the house rabbits' poop and other organic waste, and the worms digest it down to worm castings. The worms even eat junk mail and cardboard.
First, the bunnies do their thing. In large volumes, every day.
The droppings get filtered out with a cat litter scoop. I avoid the urine-soaked bedding- it can hurt the worms. The dry bedding is ok, though. I compost the urine-soaked bedding separately- it's high in nitrogen.
The worms get fed their favorite food. To Eisenia fetida, bunny poop is ice cream. This bin needs some fresh bedding on top, but there is no odor and the worms are crawling all around it, so the bin is well-aerated and healthy.
It all gets digested, and redigested, into this fabulous stuff-- worm castings. The more times it passes through the guts of the worms, the better it becomes.
Finally, the castings go to the plants. I use my castings for everything- even my seedling start mix. Then, the plants feed us and the rabbits. See? Circle of life. Or as I like to call it, the Bunny Biosphere.
The stars of the show. See the little kid worms in the middle of the picture? There are probably 40,000 worms between my two bins.