Open solid waste may pollute directly the air, besides this by washing with rainwater run-off it may pollute a large area and cause soil and water pollution. On the other hand, the closed compost system of solid waste may provide good manure. Moisture control is done and micro-organisms help to stabilize the organic matter. First, the fungi start to work, and at last, actinomycetes break down the waste and convert it to humus known as compost making a good fertilizer.