Separation of the apparatus for drying and degassing organic waste from the shaft furnace containing a gasification chamber and a combustion chamber increases the through-put capability of the shaft furnace gasification. The gasification is promoted by the addition, in the same direction of flow as the partly carbonized waste material, of a gas such as air, steam, carbon dioxide or oxygen adjusted in accordance with the changes in composition of the material that is gasified. The drying and degassing chamber is a rotary drum feeding the dried and degassed material into the top of the shaft furnace. An intermediate chamber may be imposed between the rotary drum and the shaft furnace at the top of the shaft furnace so that a sieve can separate incombustible material such as metal parts for withdrawal through a gas-tight sluice. A narrow gap, either a straight gap between moveable members or an annular gap defined by a rotary plug, provides the communication between the gasification chamber and the combustion chamber below. Material is held above the gap for completion of gasification and the actual combustion with additional air supply takes place in the combustion chamber.