TECHNOLOGY FOCUS - INSTRUMENTATION AND TESTING - Preferred Method: The control valve is controlled such that the volume flow of the filtrate is maintained at 50-300 l/hour, preferably at 170 l/hour. The volume flow of the filtrate is determined and monitored through a flow measurement in the filtrate line. The pressure in the filtrate line and the pressure in a concentrate line (7) leading the concentrate is determined, where the control valve is closed when the pressure in the filtrate line is lower than the pressure in the concentrate line, and the control valve is opened again, when the pressure in the filtrate line is higher than the pressure in the concentrate line. A turbulent flow is generated in the filtering device for cleaning the filtering device. The two control valves are successively arranged in the filtrate line for regulating the volume flow of the filtrate. The dry substance content and/or the density of the livestock manure in the storage container and/or the pressure upstream of the filtering device is determined and the filtering is terminated when the dry substance content and/or the pressure upstream of the filtering device reaches a predetermined limit. The concentrated livestock manure is removed from the storage tank after or during filtering and is supplied to a fermentation container of the biogas plant, and the storage tank is filled with an amount of new livestock manure, which corresponds to the total amount of withdrawn livestock manure and the filtering is continued. The removal is carried out periodically. The pump pumps the livestock manure during filtering operation into the filtering device and simultaneously supplies back the concentrate into the storage tank. The filter element is formed by a sieve cylinder and/or a perforated sheet, where the filter element is arranged vertically. A flow rate sensor is arranged in the filtrate line for measuring the volume flow of the filtrate. Preferred Components: The limit value of the dry substance content is 12-18%. The limit value of the pressure upstream of the filtering device is 1.5-5 bars. The system comprises: a first pressure sensor in the filtrate line and a second pressure sensor in the concentrate line; and a device for determining the dry substance content in the reservoir and/or a third pressure sensor, which is upstream of the filter device. EXAMPLE - No suitable example given.