A method and a device for the thermal decomposition of an initial material, in particular, for the decomposition of meat and bone meal, oil sludges, for example, from cleaning tankers, autofluff (also called autofluffy), basic glycerin, for example, from biodiesel production, paint sludges from paint shops, contaminated soils, coated wood, and plastics such as plexiglass. According to the present method, organic initial materials are thermally decomposed very completely in nearly all cases. The very complete decomposition is achieved by adding foreign particles such as metal spheres to the initial material which is being thermally decomposed.