A method and apparatus for incineration of combustible material including the processing of sewage sludge from wastewater treating plants and the initial activation and regeneration of activated carbon granules or powder used for adsorption in wastewater treatment and the like. The method is carried out by supporting the combustible material in an enclosure, directing infrared radiation on the material, and controlling the atmosphere in the enclosure around the material for purposes of controlling the oxidation process initiated by the heat from the infrared radiation. In a more specific form the method includes a step of counter-flowing combustion gases over the combustible material to supplement the infrared heat. The combustion chamber of the enclosure is operated at a slight vacuum to minimize escape of noxious odors. In practicing the method with sewage sludge, the sludge is first pre-dried and fragmented before introducing it into the enclosure. In the enclosure the sludge is burned by the combined heat of the infrared and counter-flowing combustion gases to incinerate all combustible material in the sludge. When applied to carbon particles, the method comprises the burning of bonding agents and other foreign matter present in the carbon when the carbon is initially activated, and when the method is applied to regeneration or reactivation of the carbon, the contaminants on and within the carbon resulting from the adsorption process are burned from the carbon with the atmosphere controlled to prevent oxidation of the carbon itself.