NOVELTY - The method comprises fermenting a fermentation substrate (1) in a biogas plant (A) and subsequently energetically utilizing the obtained biogases in a combined heat and power unit, where the animal and/or plant materials are provided as fermentation substrate. A bioreactor (B) is upstream to the biogas plant for aerobic treatment and hydrolysis of the fermentation substrate. The biomass containing microorganisms is introduced in addition to the atmospheric oxygen (2), where the heat energy originates from the connected combined heat and power unit.    USE - Method for efficient operation of a biomass fermentation plant, which is useful in agriculture, food industry and disposal industry.    ADVANTAGE - The method ensures economical and efficient operation of the biomass fermentation plant with less energy consumption and less investment costs.    DETAILED DESCRIPTION - The method comprises fermenting a fermentation substrate (1) in a biogas plant (A) and subsequently energetically utilizing the obtained biogases in a combined heat and power unit, where the animal and/or plant materials are provided as fermentation substrate. A bioreactor (B) is upstream to the biogas plant for aerobic treatment and hydrolysis of the fermentation substrate. The biomass containing microorganisms is introduced in addition to the atmospheric oxygen (2), where the heat energy originates from the connected combined heat and power unit and the bacterial biomass (10) from the subsequent processing steps. The fermentation substrate (4) pretreated in the bioreactor, the further fermentation substrate and optionally the concentrated bacterial biomass form an input material for the biogas plant. The fermentation residual remaining in the biogas plant is further processed in the bioreactor under the effect of heat energy during the addition of atmospheric oxygen and biogenic substances as a carbon source. The biomass separation is downstream to the bioreactor in the form of micro-filtration, sedimentation and/or electro-coagulation, where permeate developed during the micro-filtration is introduced again into the bioreactor, the aqueous residual phase is discharged and the biomass is again introduced into the fermentation process such as in the bioreactor and/or the biogas plant. The biomass is optionally subjected to a concentrator in a separator or to a decanter, where the developed liquid phase is discharged and the concentrated bacterial biomass is provided as additional input material for the biogas plant. The heat energy introduced earlier in the fermentation process is provided for the bioreactor of the combined heat and power unit or other energy generating systems e.g. fuel cells.    DESCRIPTION OF DRAWING(S) - The diagram shows a schematic representation of a method for efficient operation of a biomass fermentation plant.    Fermentation substrate (1)    Atmospheric oxygen (2)    Pretreated fermentation substrate (4)    Bacterial biomass (10)    Biogas plant (A)    Bioreactor. (B)