Minecraft wiki entry for Bone_meal_farming, associated text: Items can be inserted into the composter by placing a hopper on top of a composter. The farm starts by adding unwanted compostable items into the chest on the top left (see picture). The items in the chest occasionally drop into a minecart with a hopper that travels along a track over the hoppers above the composters. The items are taken out of the hopper minecart and into the composter, and composted automatically. When the composter is fully fertilized, the bone meal is taken into the bottom chests.