Abstract: An integrated liquefaction and gasification process converts bulk particulate halogen-containing waste plastic materials with minimal particle size reduction into a synthesis gas and a non-leachable, vitreous environmentally nontoxic slag. The process involves melting and cracking bulk particulate halogen-containing waste plastic material to form a lower boiling point, lower molecular weight halogen-containing oil composition which then undergoes partial oxidation in a quench gasifier to produce a synthesis gas. Any hazardous gases, liquids or solids that are produced can be purified into commercially valuable byproducts or recycled to the process, which does not release hazardous materials to the environment.