Compost helps the soil by improving its structure, so it retains more moisture and allows for more air flow. Decomposed organic matter, or compost, also provides nutrients for plant growth. Gardeners can make compost with leaves, grass clippings, kitchen wastes and other organic matter. The time it takes to make compost varies from a few months to a few years, depending on the method used. Some composting aids are designed to speed up the composting process.