Commercial systems consisting of a close-coupled gasifier and combustor are manufactured by CHIPTEC Wood Energy Systems and are widely used in the Northeast to supply hot water and steam to schools and commercial buildings (Bravakis, 1996). The plants are fueled with wood chips that are conveyed to the refractory-lined gasification chamber by an automated feeder. The fuel can contain up to 45% moisture. An induced draft fan draws air into the crossdraft gasifier, and the resulting low-energy product gas, which is produced under oxygen-deficient conditions, is passed to the combustion chamber. High tem­perature combustion, a 20:1 turn-down ratio, refractory heat storage, and controlled air allow the gasifier to respond quickly to boiler demand. Gasifier outputs range in size from 0.5 to 10.5 GJ/h, and the corresponding firing rates are 50.8 to 965 kg/h with wood chips having a 35% moisture content. The smaller systems have stationary grates and the larger systems are equipped with moving grates.