NOVELTY - The system has a reactor (12) i.e. fixed bed reactor, including an upper section (14), a central section (16) and a lower section (18), and a feedstock inlet (20) arranged in the upper section to receive a carbonaceous feedstock e.g. wood. An oxidant inlet (24) is placed in the lower section to receive an oxidant (26). A raw product gas outlet (28) is positioned in the upper section. A recycle conduit (30) couples the raw product gas outlet to the lower section and recycles raw product gas from the upper section to the lower section.    USE - Gasifier system for gasifying a carbonaceous feedstock e.g. biomass such as wood, woodchip, sawdust, bark, seed, straw, grass, agricultural and forestry waste, forest and agricultural residue, and energy crop, and mixture of coal and biomass (all claimed), into product gas i.e. synthesis gas (syngas). Can also be used for coal or coal-containing material.    ADVANTAGE - The system can optimize a set of heating conditions while inexpensively producing high yield of the product gas with reduced tar content as a gas stream is made to react with char and ash products or catalytic activity of char is utilized to decompose the tar. The product gas exiting the reactor allows recovery of heat from a heat exchange unit so as to preheat the oxidant and/or raw product gas, thus improving overall efficiency of the system.    DETAILED DESCRIPTION - The oxidant is selected from air, oxygen, a mixture of air and steam, a mixture of air and carbon dioxide and a mixture of air, steam and carbon dioxide. An INDEPENDENT CLAIM is also included for a method for converting a carbonaceous stream into product gas in a gasifier system.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic view of a gasifier system.    Reactor (12)    Upper section of reactor (14)    Central section of reactor (16)    Lower section of reactor (18)    Feedstock inlet (20)    Oxidant inlet (24)    Oxidant (26)    Raw product gas outlet (28)    Recycle conduit (30)