NOVELTY - The system comprises a vessel, perforated tubes (20, 22), an annular space (60), and a gas-specific membrane system. The vessel comprises a multi-stage reactor comprising a leach-bed reactor and a suspended- growth reactor. The suspended-growth reactor is present in a fluid communication with the leach-bed reactor. A portion of the tubes divides the leach-bed reactor from the suspended-growth reactor within the vessel. The annular space is placed between the tubes, and comprises an area for anaerobic fermentation producing carbonic acid and dissolved fatty acids.    USE - The system is useful for producing a gas such as a hydrogen gas from solid biological material such as organic solid waste including biomass wastes, food wastes, and farm wastes, where the hydrogen gas is useful as a fuel.    ADVANTAGE - The system is capable of economically, efficiently and rapidly producing the renewable and sustainable hydrogen gas in pure and sterile form with less energy consumption, and exhibits good performance and stability.    DETAILED DESCRIPTION - The system comprises a vessel, perforated tubes (20, 22), an annular space (60), and a gas-specific membrane system. The vessel comprises a multi-stage reactor comprising a leach-bed reactor and a suspended- growth reactor. The suspended-growth reactor is present in a fluid communication with the leach-bed reactor. A portion of the tubes divides the leach-bed reactor from the suspended-growth reactor within the vessel. The annular space is placed between the tubes, and comprises an area for anaerobic fermentation producing carbonic acid and dissolved fatty acids. The gas-specific membrane system is disposed above the leach-bed reactor and the suspended-growth reactor and is in the fluid communication with the multi-stage reactor. The suspended-growth reactor comprises a continuous stirred-tank reactor, a magnetic stirrer, and a light source. The leach-bed reactor comprises a fixed-bed reactor.    DESCRIPTION OF DRAWING(S) - The diagram shows a schematic view of a reactor.    Tubes (20, 22)    Tank (30)    Wet cattle manure (40)    Leachate (50)    Annular space. (60)