Abstract: An apparatus and method for starved air gasification of solid organic materials, including biomass and other wastes, to convert the chemical energy stored in such materials to thermal energy or gaseous products that may be used in biochemical and/or chemical synthesis. Specifically, the system utilizes a gasifier having a “moving bed of ash” hearth wherein the feedstock is partially oxidized at a low temperature (less than 1500 degrees F.) in a square or rectangular chamber having a vaulted, tapered or flat roof. Combustion gases from the gasifier are held at temperature using a recovery and regeneration chamber, and then undergo secondary oxidation in an oxidizer. The high temperature gases produced by the system can be utilized to advantage, for example, as the thermal energy source for a conventional heat recovery device such as a heat exchanger, steam generator, hot oil or air heater, or steam boiler.