NOVELTY - The method comprises loading a closed container with cut up plant mass for performing dry fermentation using an anaerobic process by displacing CO2 (carbon dioxide) supply air and/or atmospheric oxygen from the container, taking off methane-containing biogas, and changing the anaerobic process to an aerobic process by injecting air in the container and blowing CO2, where, during the anaerobic fermentation, generated process gas and water are collected and again given over the biomass. Layers or floors having media-perfused pipes (3) or tubes are created in the container.    USE - The method is useful for chronological treatment of biomass to biogas with final compost production.    ADVANTAGE - The method ensures economical, simple and effective chronological treatment of the biomass to biogas.    DETAILED DESCRIPTION - The method comprises loading a closed container with cut up plant mass for performing dry fermentation using an anaerobic process by displacing CO2 (carbon dioxide) supply air and/or atmospheric oxygen from the container, taking off methane-containing biogas, and changing the anaerobic process to an aerobic process by injecting air in the container and blowing CO2, where, during the anaerobic fermentation, generated process gas and water are collected and again given over the biomass. Layers or floors having media-perfused pipes (3) or tubes are created in the container for temperature control and/or humidification of the biomass. The heat generated by the pipes is led out in the aerobic composting process for avoiding overheating of the medium and for maintaining a constant, where the bacteriological activity optimizing heat is continuously deducted or the dry fermentation process of a second unit is supplied for starting the process. The extracted low calorific heat and CO2 directly resulting in the composting process are fed into a biomass generation reactor, in which aquatic plants stacked on aquatic cropland are cultured and propagated. The cultured aquatic plants are partially supplied in the dry fermentation and/or compost process for accelerating the fermentation and/or composting process. The aerobic composting process comprises washing the compost using wastewater, industrial water or process water, filtering the solid particles, and running off the filtered water as a nutrient along the generated heat to aquatic crops present in the biomass production reactor. The biomass comprises organic substrate material such as animal hair, cardboard, wood chips, sludge and/or fermentation residues such as wet fermentation biogas plants and/or liquid stillage waste. An absorption ballast is inserted in the container, before the introduction of biomass in the container, to collect first toxic seeping juices. An INDEPENDENT CLAIM is included for a device for chronological treatment of biomass to biogas.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic view of a stacked arrangement of combined biogas/composting substrate.    Plant substrate layers (2)    Pipes (3)    Controllable valve (4)    Air outlet (12)    Gas outlet. (14)