A composter in Minecraft serves four purposes- as a job site block for a villager to become a Farmer, as a way to produce bone meal from unwanted plant and food material, as fuel for a furnace to smelt items, and as a power source for a Redstone Comparator.
Bone meal is useful in Minecraft as a fertiliser and as a white dye. It can also be combined with other dyes to produce colours such as grey, light blue, and lime (among others). Bone meal is created using bone or bone blocks, but also by using composters.
Composters can be crafted using any wood slabs, or they can be found in village farms.
The only foods a composter cannot recycle in to bone meal are:
- Poisonous Potatoes
- Dead Bushes
Everything else can be placed into the composter, where it emits green particles to show the food has entered it, and eventually becomes more and more full until it shows it has composted what is inside. The player can then collect the bone meal by using the composter for a final time. A hopper can also be used in conjunction with the composter by placing it directly below and collecting the bone meal automatically.
Using the composter as a power source depends on how full the composters is- the more full it is the more powerful it is. This works in increments of 7 from 1/7th full composter = 0 signal strength up to 7/7 full composter = 8 signal strength.