NOVELTY - The methane fermenter comprises a volumetric reactor arranged to provide a gas phase portion and a liquid phase portion of the reactor, a first ring bubble-distributor (102) for methane-containing gas, a second ring bubbler-distributor (103) for oxygen or air, a liquid recirculation loop (107), a gas recirculation loop, a first input nozzle for input of a nutrient medium into the liquid recirculation loop, a second input nozzle for input of water into the liquid recirculation loop, and a heat exchanger (111) for removal of heat from the fermentation process.    USE - The methane fermenter is useful for producing protein (claimed) such as Gaprin (RTM: Protein) and biomass.    ADVANTAGE - The methane fermenter economically and efficiently produces the protein with high safety without using separate compressor in an environmentally friendly manner, and increased capacity.    DETAILED DESCRIPTION - The methane fermenter comprises a volumetric reactor arranged to provide a gas phase portion and a liquid phase portion of the reactor, a first ring bubble-distributor (102) for methane-containing gas, a second ring bubbler-distributor (103) for oxygen or air, a liquid recirculation loop (107), a gas recirculation loop, a first input nozzle for input of a nutrient medium into the liquid recirculation loop, a second input nozzle for input of water into the liquid recirculation loop, a heat exchanger (111) for removal of heat from the fermentation process, an ejector (112)arranged to add recirculating gas into the liquid recirculating loop, a pipeline for feeding a gas-liquid mixture into the reactor, and an output nozzle. The output nozzle is located at the top of the fermenter. The fermenter further comprises a pump located in the liquid recirculation loop for re-circulation of the liquid phase, a damper-separator arranged to provide effective separation of the gas and liquid phases, an internal pipe arranged to remove liquid from the reactor to be recirculated by the liquid recirculation loop, a cone damper located with the internal pipe so as to stop rotation of the liquid inside the internal pipe, an off-gas pipeline arranged to remove waste gas, a measuring device located in a nozzle in the off-gas pipeline, a sampling device, external circulating loops in the reactor to provide for simultaneous recirculation of gas and liquid phases of the reactor, and an apparatus to supply ammonia via direct fed line to maintain pH. The ejector is arranged to distribute recirculating gas in the form of small bubbles in the recirculating liquid phase to form a gas liquid mixture. The pipeline is located at the base of the reactor, and is arranged to maintain upward rotation of the gas liquid mixture in the reactor. The damper-separator is arranged to provide effective separation of the gas phase portion and the liquid phase portion at the top of the reactor, and comprises components including a horizontal grid structure, a plate structure with valves, caps a liquid overflow, a cyclone and a group of cyclones. The recirculation loop is arranged such that recirculating liquid exits the fermenter via the recirculation loop at the base of the fermenter. The cone damper is located on top of the internal pipe. The recirculation loop is arranged such that the recirculating gas exits the fermenter via the recirculation loop at the top of the fermenter. The measuring device is arranged to control reactor pressure, is located in a nozzle in the reactor. The sampling device is located in a nozzle in the off-gas pipeline and arranged to sample the content of the off-gas and to sample the content of oxygen in the fermenter continuously. The internal pipe and nozzle are arranged to supply ammonia solution to the reactor. An INDEPENDENT CLAIM is included for a method for methane fermentation.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic view of a fermenter apparatus.    First ring bubble-distributor (102)    Second ring bubbler-distributor (103)    Liquid recirculation loop (107)    Heat exchanger (111)    Ejector. (112)