Organic mulch can be left at the base of your plants to decompose and turn into humus on its own. However, if taken to the compost pile, it will decompose much more quickly. But your compost pile needs more than just mulch to break down matter effectively. Dry material like mulch and other garden waste should be balanced with moist material like kitchen waste. Otherwise, your pile will be too dry for the composting bacteria to do its job. Add moist material in equal amounts to dry material so that your compost pile is just about as moist as a wrung-out sponge.
Break large pieces of mulch into smaller pieces. Pine needle or leaf mulch can be cut into small pieces with scissors. Break bark mulch into smaller pieces with your hands or chop up the pieces with a sharp knife or small axe. Large pieces can be put into the compost pile if you have no way to cut them, but they will take longer to compost.
Spread the mulch over the top of the compost pile. If you have a large amount of compost that will upset the moisture balance of your pile, add an equal amount of kitchen waste. If you don't have any available immediately, store some of the mulch just to the side of the compost pile and add it in a little at a time each time you add kitchen waste to the pile.
Use a large stick or shovel to turn the compost pile and mix the ingredients thoroughly.
Turn the pile once weekly or each time you add new material. The compost should turn into humus in six months to a year.