Abstract

This article discusses the recycling of used petroleum oils, especially those employed as lubricants. The term oil includes a variety of liquid or easily liquefiable, unctuous, combustible substances that are soluble in ether, but not in water, and that leave a greasy stain on paper or cloth. These substances can include animal, vegetable, and synthetic oils, but usually the word oil refers to a mineral oil produced from petroleum. An oil that has been used or contaminated, or both, but not consumed, can often be recycled to regain a useful material regardless of its origin. In the past, used or contaminated oil was often considered a waste and was disposed of in a variety of ways, including incineration, road oiling, landspreading, municipal landfills, and dumping on the ground or into storm sewers. However, growing public awareness of the societal costs of pollution, the advent of periodic petroleum shortages, and increased prices for most kinds of oils and oil products have combined to generate a strong interest in developing ways to conserve the valuable energy and resource content of these products.