It’s important in your compost to have the right ratio of carbon and nitrogen. And the right ratio is thirty to one. So you really don’t need a lot of manure or grass clippings- it’s mostly dead leaves and scraps from your yard, trimmings and things like that. Grass clippings, in fact- just pure green grass clippings have a ratio of twenty to one.
The reason you need nitrogen is for the microorganisms’ bodies. They need the nitrogen which becomes the protein of their bodies. If you have too much nitrogen, the microorganisms die. And if you have too little, your compost is dry and it doesn’t break down, because of the lack of microorganisms.