Obtaining a biodegradable fiber material that can be used as a material from processed fermentation residues from biogas plants.

The invention relates to the production of lignocellulosic fibers with special chemical and mechanical properties from the digestate of biogas plants which use sufficient fiber-rich biomass such as straw， grass， annual and perennial plants as input. This makes it possible to obtain biodegradable fiber material for a wide range of applications such as the manufacture of wood fiber boards， papers and cardboard， nonwoven and insulating materials， injection molding， 3D printing and fiber molding products. In order to achieve this， the valuable lignocellulose fibers from the fermentation residue must be separated from the rest of the residue in such a way that they are freed from volatile ammonia and adhering minerals and impurities. According to the invention the object is achieved in such a way that the fiber-rich fermentation residue is mechanically separated in a manner known per se， the solid fermentation residues obtained are then mixed with a recycling water to a pumpable dry matter content of 10 to 18%， and the ammonium nitrogen is removed from this mixture after pre-comminution in one or more stripping containers arranged in succession at a negative pressure of 10 to 80 kPa and heating to 40 to 90 ° C. without the addition of chemicals， and the mixture treated in this way is mechanically separated again ， after which the fibers contained are present in a cleaned and separated form. Adhering sand， minerals and organic fines are removed by 40 to 90% and are practically completely converted into another recycling water when subsequently suspended.