The annual production of beet sugar in Poland in 2021/2022 marketing year was 2.3 million tonnes. The by-product of beet sugar processing is beet sugar pulp, which utilization may be challenging. The sugar beet pulp may be managed in the agricultural biogas plants. One way of biogas production intensification is substrate disintegration. This study covers the analysis of the hydrodynamic disintegrator dedicated for the agricultural waste pretreatment aimed at biogas production intensification. The process can be divided into two stages: mechanical shredding in the knives zone and substrate cavitation in rotor grooves. Aiming at hydrodynamic disintegrator assessment, especially in the frames of rotational speed mathematical model of the processes was built and implemented in Ansys CFX numerical environment. The sugar beet pulp has been subjected to rheological tests to determine the medium viscosity. The fluid was identified as non-Newtonian, viscoplastic. The Herschel-Bulkley model was used for the viscosity calculation. Three rotational speeds were considered: 1500 rev/min, 2500 rev/min and 3000 rev/min. The shear stress field in the knives zone and low-pressure zones in the rotor grooves were analyzed. The largest cavitation volume was suspected in the case of the highest considered rotational speed.