https://permies.com/t/69798/critters/Deep-litter-system-KNF-progress

Deep litter systems are living systems in which a thick layer of carbon-rich organic matter hosts a thriving microbial community which works to break down solid and liquid wastes from animals as they are produced.  Such as system doesn't require regular cleaning out, and has the added benefit of producing high quality, rich compost.  If set up right, they are low maintenance and doubly productive systems.  They are especially well suited for animals that like to root or scratch, like chickens and pigs, which keep the littler mixed while enjoying their natural habits.   This concept can be applied in a number of different ways, and there's no one right way to do it.  The goal, though, is to always have a healthy, living litter.  On our farm we always say that the litter of your pen should smell like the forest.  If it doesn't, there's something that needs adjusting.   A lot of what we have learned has come from Korean Natural Farming (KNF),  and although we haven't followed any one recipe exactly, we have borrowed heavily from that tradition for the systems you'll see below.