NOVELTY - A disintegrating system (30) for treating organic material comprises: multiple disintegrating units (31, 32) each having inlets (33, 34) for receiving materials (A, B) and disintegrating unit outlets (37, 38) for outputting treated material, respectively, in which inlet of first unit is configured to receive organic material; where first feedback pipe (35) is connected between outlet of first unit and inlet of second unit, and outflow (39) of disintegrating system is connected to outlet (37) of first disintegrating unit, and sum of introduced materials is available at the outflow.    USE - As a disintegrating system for treating organic material (preferably for a biogas producing system that uses anaerobic digestion of organic matter) (claimed).    ADVANTAGE - The system and method allow for disintegration of at least one organic material to control viscosity of organic material, while maintaining high dry solids contents of organic material; compared to the prior art systems and methods. In the system different organic materials can be mixed together more easily before introducing into biogas producing system by controlling flow through a number of pumps; and an increased amount of biogas can be produced in anaerobic digestion process for producing biogas compared to prior art systems. Further, the organic material with low dry solids contents can be subjected to ultrasonic treatment compared to prior art systems.    DETAILED DESCRIPTION - A disintegrating system (30) for treatment of organic material comprises: multiple disintegrating units (31, 32) each having inlets (33, 34) for receiving materials (A, B), and disintegrating unit outlets (37, 38) for outputting treated material, respectively, in which inlet of first unit is configured to receive organic material; where first feedback pipe (35) is connected between outlet of first disintegrating unit and inlet of second disintegrating unit, and an outflow (39) of disintegrating system is connected to outlet (37) of first disintegrating unit, and sum of introduced materials is available at the outflow. The disintegrating system further comprises a feedback pipe arranged to feed back at least a part of treated material at outlet of each disintegrating unit to inlet of same disintegrating unit. A second feedback pipe (36) is connected between outlet of second disintegrating unit, and inlet of the first disintegrating unit. A first feeding pump is provided to feed organic material to inlet of first disintegrating unit, and a second feeding pump is provided to feed material to inlet of the second disintegrating unit; and a feedback loop pump is provided in feedback pipe having flow capacity of at least equal to flow capacity of each feeding pump. The outflow is connected to outlet of first disintegrating unit, or multiple disintegrating units. A feed forward pipe is connected between outlets of second and first disintegrating units. A second feedback pipe is connected between outlet of second disintegrating unit and inlet of third disintegrating unit, and second feed forward pipe. A viscosity detector is provided to determine viscosity of treated material at outlet of the first disintegrating unit, and a control unit (65) is configured to receive measured parameters from viscosity detector to control flow through first feedback pipe. The disintegrating units are ultrasonic reactors, or mechanical dispersion devices. An INDEPENDENT CLAIM is included for a biogas producing system using anaerobic digestion of organic matter comprising: a tank reactor containing biogas-producing bacteria for digestion under anaerobic conditions, and provided with inlet for receiving organic material for biogas production; feeding device to feed organic material into tank reactor to obtain digestion while producing biogas and forming digested sludge; and further comprising the disintegrating system(s) configured to feed treated organic material to inlet of tank reactor.    DESCRIPTION OF DRAWING(S) - The figure shows the disintegrating system in which more than one organic material is treated.    Disintegrating system (30)    First disintegrating unit (31)    Second disintegrating unit (32)    Inlet of first disintegrating unit (33)    Inlet of second disintegrating unit (34)    First feedback pipe (35)    Second feedback pipe (36)    Outlet of first disintegrating unit (37)    Outlet of second disintegrating unit (38)    Outflow (39)    Control unit (65)    Introduced materials (A, B)