Abstract: Combustible carbonaceous and sulfur-containing wastes, especially waste liquors of cellulose plants, are burnt with a combustion-sustaining gas having a greater oxygen concentration than atmospheric oxygen (e.g. pure oxygen) and the gaseous products of the combustion are subjected to scrubbing to remove carbon oxides. The process is carried out under pressure and preferably with two-stage combustion so that carbon monoxide produced in an initial stage can be burnt further in the combustion chamber of a gas turbine to drive the latter and generate at least part of the power necessary to operate the compressor for the oxygen-rich gas.