Abstract: This invention describes a process and apparatus for the combustion of wastes, wherein the wastes are combusted in a combustion chamber and the temperature of the combustion chamber is controlled by changing the amount of combustion air as a function of the slag flow rate. The combustion can be carried out substoichiometrically in a reducing atmosphere because of additives which are introduced into the slag in the form of fine dusts. On account of the substoichiometric operation, the requirement for fluid wastes and/or supplemental fuel is drastically reduced, the capacity of the rotary tubular kiln is increased and nitrogen oxides formation is reduced.