NOVELTY - Concentrating the dry substance content of pumpable livestock manure for a biogas plant, preferably liquid manure into a storage tank (1), which is at least partially filled with livestock manure, comprises: directing, preferably pumping the livestock manure to a filtering device (3), in which at least one filter element is flooded and a concentrate with a high solid content and a filtrate with a low solid content are separated; and recycling the concentrate into the storage tank, where the volume flow of filtrate is regulated by at least one control valve (6).    USE - The method is useful for concentrating the dry substance content of pumpable livestock manure for biogas plant.    ADVANTAGE - The method is simple and increases the biogas yield from manure by four-fold compared to untreated substrates at lesser volume flow.    DETAILED DESCRIPTION - Concentrating the dry substance content of pumpable livestock manure for a biogas plant, preferably liquid manure into a storage tank (1), which is at least partially filled with livestock manure, comprises: directing, preferably pumping the livestock manure to a filtering device (3), in which at least one filter element is flooded and a concentrate with a high solid content and a filtrate with a low solid content are separated; and recycling the concentrate into the storage tank, where the volume flow of filtrate is regulated by at least one control valve (6), which is arranged in a filtrate line (5) leading the filtrate.    INDEPENDENT CLAIMS are also included for:    (1) a system for concentrating the dry substance content of pumpable livestock manure for biogas plant, preferably liquid manure comprising the storage tank, which is at least partially filled with livestock manure, filtering device into which the livestock manure is pumped by a pump, and having filter element, which is flooded to separate concentrate with high solid content and filtrate with a low solid content, concentrate line through which the concentrate is fed back into the storage tank, at least one control valve, which is arranged in a filtrate line for leading the filtrate, and an arrangement, which regulates the volume flow of the filtrate by adjusting the control valve; and    (2) a biogas plant comprising the system.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic representation of the system for concentration liquid manure in batch mode with a dry substance monitoring.    Storage tank (1)    Filtering device (3)    Filtrate line (5)    Control valve (6)    Concentrate line (7)