Abstract: Method and apparatus for incinerating low density organic materials using a pair of side by side multiple hearth furnaces are disclosed. The first furnace of the pair operates in a temperature-controlled reducing atmosphere to achieve complete volatilization of non-fixed carbon contained in the fuel feed stock. The second furnace operates in a temperature-controlled oxidizing atmosphere to achieve complete oxidation of all fixed-carbon contained in the char output of the first furnace. The gaseous products of both furnaces are combined and burned in a low - Btu gas burner, thus providing the heat input to a power boiler or other process suited to the heat quality produced.