Abstract: In a hydrocarbon release rate controlling method, a first chamber is provided capable of receiving successive batches of feed materials for thermal processing having widely varying energy content, heating is produced in the first chamber to cause pyrolyzing of the feed materials into fluid materials, a second chamber is provided communicating with the first chamber and capable of receiving the fluid materials from the first chamber and communicating the fluid materials to a discharge location, heating is produced in the second chamber to cause oxidizing of the fluid materials into discharge gases reaching the discharge location, a jacketed vessel is provided defining a channel surrounding the first and second chambers containing a flow of coolant fluid through the channel, separate variable flows of primary and secondary air are respectively produced into and through the first and second chambers, the temperatures in the first and second chambers are sensed, the temperature of the coolant in the channel of th