Producing biogas comprises fermenting biomass in a hydrolysis- and a first methanizing step, separating gas mixture in to methane- and carbon dioxide containing gases and reacting hydrogen and carbon dioxide to methane using bacteria

摘要

Production of biogas by fermentation of biomass in a biogas plant, comprises: fermenting biomass in at least two steps, which are a hydrolysis- and a first methanizing step; separating gas mixture produced in the first methanizing step in two gas portions, where a first- and second portion mainly consists of methane and carbon dioxide, respectively; introducing the carbon dioxide and hydrogen containing hydrolysis gases derived from the hydrolysis step, in the reactor of a second methanizing step; and reacting hydrogen and carbon dioxide to methane in the presence of methanogenic bacteria. Independent claims are also included for: (1) a biogas plant for carrying out the above process, comprising at least one hydrolysis reactor, at least two methanation reactors, which are a first methanation reactor and a second methanation reactor, at least a separation device for separating two gas-portions of the gas mixture resulted from the first methanation step, at least a transporting device for transporting the carbon dioxide from the first methanation step to the second methanation reactor, at least a transporting device to transport hydrogen-containing hydrolysis gases derived from the hydrolysis reactor to the second methanation reactor, at least a feeding device to introduce gases in the second methanation reactor, at least a feeding device for feeding a bacterial culture in the second methanation reactor, where the bacterial culture includes methanogenic bacteria; and (2) an immobilized bacterial culture used in the above process or in the biogas plant, where the bacterial culture comprises methanogenic bacteria.