Abstract: A method for the decomposition of waste material in which the waste material and a stream of air are introduced into a first chamber to initiate the decomposition reaction and thence into at least one additional chamber to complete the reaction. Heated gases produced by the reaction are recycled and brought into heat exchange relation with the incoming air and with the waste material in the first chamber to raise the temperature of the incoming air and waste material to thereby increase the efficiency of the decomposition method. Apparatus includes heat exchange conduit means adapted to conduct the recycled heated reaction gases to the first chamber into heat exchange relation with the waste material therein and into heat exchange relation with the air being introduced to such first chamber.