Abstract: A one-step thermal treatment process for liquefaction of solid wastes selected from the group consisting of printed circuit board wastes, plastic wastes, rubber wastes, scrap fires, used cables/wires, auto shredder residues, contaminated soils, and waste lubricating oils to recover valuable oil products. Apparatus is provided and includes a means for continuous feeding, an inclined screw liquefaction reactor(ISLR), and means for handling oils and gas products. Wastes are liquefied in used lubricating oils or recycled heavy oil product at relatively low temperatures, and the unliquefied inorganic materials are recovered.