Abstract: An apparatus for recovering energy from pyrolyzable, carbonaceous waste materials, for example household refuse, comprising a rotary tube reactor (4) adapted to be charged with the waste materials and producing, as products, a (low temperature) carbonization gas and a pyrolytic coke at a reaction temperature of above 200.degree. C.; a fluidized bed or swirling layer gasifier adapted to be supplied with an oxygen-containing gasifying agent, the pyrolytic coke and, optionally, waste materials and from which exit a hot gas having a temperature of between 400.degree. and 1000.degree. C. and an inert ash. Further, the system includes cleaning stages (8, 20) for the carbonization gas, connected subsequent to the rotary tube reactor and the gasifier (14), and further a combustion device (24) for the cleaned gases, as a part of a boiler system.