Abstract: Apparatus for pyrolytically treating municipal and other waste comprised of solid heat-decomposable material by radiative heating from an open flame and convective heating, the invention particularly provides for heat recovery of a substantial amount of initial energy input. In the several embodiments of the invention, the source of initial heat energy input can vary from gasification of renewable fuel such as wood chips and the like to burning of a primary fuel, such energy input being preferably augmented by burning of at least a portion of the gaseous pyrolytic decomposition gases produced by treatment of the waste. Heat generated during the process of pyrolyzing waste is also utilized to warm combustion air as well as recovered to the extent possible for heating purposes or for the accomplishment of useful work.