The present application discloses an apparatus for gasification of solid, liquid and gaseous organic feed materials having a fuel value into synthesis gas. The apparatus comprises: a gasification reactor vessel having a tapered interior with a minimum of four zones for introducing reaction gas mixtures, a central perforated diffuser pipe, a solid and liquid material inlet at the upper end of the uppermost zone, a solid and gas discharge outlet at the lower end of the bottom zone, wherein the reactor vessel defining a sequence of reaction zones from the material inlet to the material outlet including drying, pyrolysis, combustion and gasification zones, and confining downwardly moving the column of the feed materials within the zones, gas feed inlet pipes for introducing reaction gas into the zones, a synthesis gas discharge pipe below the zones, and a heat exchanger below the zones.