All organic material will naturally rot down into compost. Have a look in a local wood and you’ll see it happening all over the place. Making compost is a bit like making yoghurt or wine, you need two types of ingredients to make a compost batch work.
Here’s the scientific bit:
Green things This is the simplest way to describe things that are high in nitrogen. They will be the wetter, mushier things in the mix – plant cuttings, fruit and vegetable waste, horse manure etc. They are often full of water and tend to seal themselves together and stop air from circulating. This can cause your compost to smell and work much more slowly, which is why you need some...
Brown things Otherwise known as carbons. Carbon is the building block of life so it is in almost everything that is or ever has been alive. In composting terms its most useful form is in the form of wood pulps - paper and cardboard, or the other fibrous parts of plants, including wood shavings. The carbon's job is to separate the greens and allow air to circulate around the compost heap or bin. The nitrogen in the greens helps the carbons to break down too.
You need about one part green to two parts brown to make the process work.
Method
put in a warm place, making sure that plenty of air can get through it
turn it regularly for six to eight weeks and it will be ready to use
you may want to take it out of the composter and let it mature in the open for a while
there are, of course many different ways that compost can be made