A method is provided for thermally processing waste to produce steam and generate energy while minimizing air pollutants in a staged thermal reactor. The method includes gasifying the waste to convert the waste to a fuel gas and a substantially carbon free, inert, granulated, sintered mineral ash and reforming the fuel gas auto-thermally to minimize creation of nitrogen oxide when the fuel gas is combusted. The method further includes burning the reformed fuel gas to minimize creation of nitrogen oxide in a flame region of a fuel gas burner and recirculating cooled flue gas to control oxygen content and temperature during the reforming operation and the burning operation. In one example, reforming the fuel gas converts non-molecular nitrogen species into molecular nitrogen in an auto-thermal non-catalytic reformer unit by decomposition reactions promoted by a prevailing reducing gas atmosphere.