NOVELTY - Methanation of biomass and energy recycling of the generated biogas in least one device exhibiting a fermenter (1), comprises (a) filling the fermenter with biomass by a feed opening (2), (b) closing the feed opening, (c) supplying the methane-rich biogas resulting in a fermentation phase into a first gas storage unit (14), (d) rinsing the fermenter with flushing air and supplying the low methane gas mixture leaving the fermenter during a rinsing phase into a second gas storage unit (15), (e) opening the feed opening, and (f) removing the digestate from the fermenter.    USE - The method is useful for methanation of biomass and energy recycling of the generated biogas in least one device exhibiting a fermenter.    ADVANTAGE - The method is carried out in a cost efficient and environmental friendly manner.    DETAILED DESCRIPTION - Methanation of biomass and energy recycling of the generated biogas in least one device exhibiting a fermenter (1) operating in the batch process, comprises (a) filling the fermenter with biomass by a feed opening (2) opened to the surroundings, (b) closing the feed opening in an air tight manner, (c) supplying the methane-rich biogas resulting in a fermentation phase at least temporarily into a first gas storage unit (14), (d) rinsing the fermenter with flushing air and at least temporarily supplying the low methane gas mixture leaving the fermenter during a rinsing phase into a second gas storage unit (15), (e) opening the feed opening, and (f) removing the digestate from the fermenter, where gas removed from the second gas storage unit is mixed with biogas removed from the first gas storage unit and the so generated mixed gas is then energetically recycled. The method is carried out in the above mentioned cyclic repeated sequence in at least one fermenter. An INDEPENDENT CLAIM is also included for a system for methanation of biomass and energy recovery of the obtained biogas comprising at least one air-tight closable feed opening, at least one gas outlet (3, 4), a purge air inlet having the fermenter, at least one purge air fan, the first gas storage unit, the second gas storage unit, the first and second gas storage unit connected with at least one fermenter, many gas control valves exhibiting gas pipeline network, a means for energy recovery of biogas and a system controller adjusting the gas control valves, where the gas control valves are adjustable by means of the system control so that either the first gas storage unit or the second gas storage unit with at least one gas outlet and optionally only the first gas storage unit or simultaneously both the first and the second storage unit are fluidically connectable with the device for energy recycling of biogas.    DESCRIPTION OF DRAWING(S) - The figure 1 shows a schematic representation of three fermenters comprising the system for methanation of biomass and energetic recycling of the generated biogas.    Fermenter (1)    Feed opening (2)    Gas outlet (3, 4)    First gas storage unit (14)    Second gas storage unit (15)