Certain microbes, particularly bact

Certain microbes, particularly bacteria, use more nitrogen. Or, if there is more nitrogen in the feed, there will be more bacteria. If there is less nitrogen, other microbes, particularly fungi, will take over feeding on the organic matter. In either case, eventually there is a veritable graveyard of dead microbes and microbe manure. When the microbes die, the nutrients become available for other microbes or for plants. When all the food is consumed, the microbe manure improves or becomes more stable with aging, just as with any other manure source.