NOVELTY - The method comprises supplying a given quantity of a biomass to a fermenter (9) of a biogas plant (1) and anaerobically fermenting the biomass in the fermenter under production of biogas. A hydrolysis device (3) is arranged upstream to the fermenter and to which a given quantity of a degradable, hydrolysis-specific organic biomass (2) is supplied to hydrolyze at a given temperature for a given retention time such that a degradable and/or hydrolysis substrate (12) convertible to biogas is produced. The organic biomass is formed by cellulose and/or lignin-containing biomass-solids.    USE - Method for producing biogas from organic biomass such as manure, corn or grain, where the biogas is useful for environmental friendly energy production.    ADVANTAGE - The method is capable of simply, reliably and economically producing biogas with higher throughput without using any additional equipment, such as stirrer in an energy-efficient manner.    DETAILED DESCRIPTION - The method comprises supplying a given quantity of a biomass to a fermenter (9) of a biogas plant (1) and anaerobically fermenting the biomass in the fermenter under production of biogas. A hydrolysis device (3) is arranged upstream to the fermenter and to which a given quantity of a degradable, hydrolysis-specific organic biomass (2) is supplied to hydrolyze at a given temperature for a given retention time such that a degradable and/or hydrolysis substrate (12) convertible to biogas is produced. The hydrolysis-specific organic biomass is formed by cellulose and/or lignin-containing biomass-solids. A predetermined quantity of organic biomass formed from short-chain hydrocarbon molecules is supplied to the fermenter in addition to the hydrolysis substrate. A dosing device (4) is arranged upstream to the hydrolysis device and from which a predetermined quantity of a hydrolysis-specific organic biomass is supplied to the hydrolysis device at a given time. The pH value in the hydrolysis device is adjusted to 2-4. The hydrolysis-specific organic biomass for the generation of a pulpy, pasty hydrolysis substrate is hydrolyzed in the hydrolysis device at 25-75 degrees C and/or with a biomass retention time of 2-4 days. The hydrolysis-specific organic biomass is linearly fed into the hydrolysis device after dosing by a screwing or a spiral conveyer, along a given hydrolysis distance, where the hydrolysis substrate is removed from the hydrolysis device at given time in given quantities. The hydrolysis substrate is partially downstream in the hydrolysis device and collected in hydrolysis substrate collector upstream to the fermenter. A given quantity of the collected hydrolysis substrate is supplied to the fermenter at given time. A separator is downstream to the hydrolysis device and into which a part of the hydrolysis substrate is separated into hydrolysis solid substrate and into hydrolysis liquid, where the hydrolysis solid substrate is dosed into the fermenter at given time and in given quantity and the hydrolysis liquid is partially dosed as hydrolysis liquid re-circulate at given times and in given quantity of the hydrolysis device. From the collector, a partial flow of the hydrolysis substrate is led to the separator and a partial flow of the hydrolysis substrate is led to a fermenter. A post-fermenter and/or an end bearing are arranged downstream to the fermenter and from which the re-circulate is supplied to the fermenter at given time. The organic biomass formed from short-chain hydrocarbon molecules is dosed to the fermenter. A space velocity adjusted in the hydrolysis device is by 10-20% of organic dry substance/m3. The space velocity adjusted in the fermenter and the post-fermenter is 4-7% of organic dry substance/m3 with a fermentation temperature of 35-55 degrees C. INDEPENDENT CLAIMS are included for:    (1) a device for the production of biogas; and    (2) a hydrolysis device for biogas production.    DESCRIPTION OF DRAWING(S) - The diagram shows a schematic view of a method for producing biogas.    Biogas plant (1)    Hydrolysis-specific organic biomass (2)    Hydrolysis device (3)    Dosing device (4)    Fermenter (9)    Degradable and/or hydrolysis substrate. (12)