Abstract: The invention relates to a method for using biomass in a biogas process. The aim of the invention is to use substrates having a high nitrogen and solid content, and which using a small amount of water, has very good energy balance and is particularly environmentally friendly. Said aim is achieved by the virtue of the fact that the substrate is treated with a recirculated product in order to form a pumpable medium, and additionally treated with bacteria in cyclones and fermenters, which simultaneously removes the nitrogen in a stripping process, separates the solid fermentation radicals and further uses the recirculated product as a heat-exchanger and reaction medium. Said process is environmentally friendly and has a very good energy balance.