A gasifier is disclosed. The gasifier comprises a primary chamber for receiving therein biomass waste material and other related volatile solids to be gasified. A fume transfer vent permits the escape of fumes from the primary chamber. A mixing chamber accepts the fumes from the fume transfer vent. The fumes then flow to an afterburner chamber where a burner member produces a heating flame so as to cause the additional full oxidization of the constituents of the fumes so as to oxidize the constituents. A partitioning wall is disposed between the flame chamber and the primary chamber so as to preclude the heating flame from entering the primary chamber and to also preclude the radiation from the heating flame from directly entering the primary chamber, thereby precluding direct contact and physical disturbance of the waste material. A heat transfer chamber in fluid communication with the afterburner chamber accepts the fully oxidized fumes therefrom. The heat from the full oxidation of the fumes causes heating of the heat transfer chamber. The primary chamber has a heat conductive floor and is superimposed on the heat transfer chamber with the heat conductive floor being disposed in separating relation therebetween so as to permit conductive and convective heating of the primary chamber, thus causing heating of the waste in the primary chamber. An exhaust vent in fluid communication with the heat transfer chamber permits venting the fumes to the ambient surroundings.