A method, system, and apparatus for decomposing a biomass feedstock include providing a layer of inert particulate matter, such as sand, to line and insulate the bottom surface of a main chamber of a reactor where pyrolysis and oxidation are conducted to produce char and producer gases as primary products. In an embodiment, feedstock positioned in a side region of the reaction chamber insulates side walls of the main chamber from heat in the center region of the main chamber. In an embodiment of the method, a rate of removal of solid products such as char from the reactor is controlled in response to a temperature detected at a position of an extraction tube inlet of the reactor. Activated charcoal may be obtained as a primary product using the system and method, by feeding oxygen into the reactor at an inlet positioned adjacent to an inlet to the extraction chamber.