Abstract: A method and a combustion furnace are provided by means of which waste which is predominantly of organic nature can be burnt effectively and uniformly. The combustion furnace comprises two bottlenecks, one above the other, constituted by rocking grates. The upper rocking grate essentially serves to subject the solids to pre-combustion, namely to drying, degasifying, and partial gasifying, and to supply the material uniformly in doses to the fire bed which is located on the lower grate and in which complete gasification takes place. Rotational movements of both grates provide for uniform passage of the material through the shaft without the risk of burn-through occurring along the edges so that the entire combustion process becomes highly uniform.