Finished compost (or humus) is decomposed organic material. When turned into the soil it goes right to work as organic matter. Besides enriching the soil, compost also recycles what would otherwise be considered home and yard waste. Backyard composting transforms waste into a valuable resource and reduces landfills. Also keep in mind that compost alone is only a soil amendment and not a fertilizer source. Compost works best when supplemented with fertilizer either as the pile is being built or later added to the soil.