A method and two embodiments of apparatus for providing efficient combustion wherein air and combustible materials are introduced into a bottom portion of a vertical chamber which is substantially open at its top, the combustible material being dispersed upwardly through a combustion zone with combustion products exiting through the open top of the chamber, gases which tend to be trapped beneath the combustion zone being vented from the chamber through suitable conduits and returned to an upper portion of the chamber if desired for more complete combustion. One embodiment of the apparatus includes a feed duct extending downwardly through the chamber for introducing combustible material thereinto. Another embodiment of the apparatus includes a feed assembly with a hopper and feed mechanism for respectively receiving combustible material and urging it upwardly through a feed duct into the chamber.