Grass clippings make an ideal organic green input for compost piles. Clippings are high in nitrogen so they stoke the microbial processes that occur with composting, and their fine texture allows them to break down quite rapidly. Green grass clippings should be used in compost piles with equal amounts of brown organic matter to ensure a good nitrogen-oxygen balance and prevent foul smelling odors from building up in the pile.
Add grass clippings to an established compost pile in an amount not to exceed 50-percent of the pile volume. Lay the clippings on top of the pile and leave for one to three days to begin to break down. Return after three days and turn the grass clippings into the center of the pile to heat up and break down further. Turn a pile with fresh grass clippings every two to five days to prevent it from becoming smelly.
Start a new compost pile with grass clippings by clearing a site for the pile directly on soil cleared of any grass, plants, rocks and roots. Layer equal amounts of green grass clippings with brown organic material, such as dried leaves or coffee grounds, in layers up to 2 inches thick. Alternate between the green and brown material until all of the clippings are layered in.
Put down a 2-inch-thick layer of garden soil, finished compost or well-aged livestock manure over the top of the new compost pile. Water the pile from the top lightly until just moist, but not soaking wet. Turn the pile at least once every five days with a large garden fork moving undigested material into the center and broken down material out of the center to the top and sides of the pile.