For optimal rotting of organic material, a supply of oxygen and therefore mixing of the rotting material is necessary. Special machines are used to turn larger compost windrows. In this master thesis, the composting process with a Topturn X4500 of Komptech GmbH is simulated. In the course of the simulation, the drum torque, mixing of the compost windrow and wear on the segments of the turning drum will be represented. A practical test will be used to verify the accuracy of the simulation results. In order to be able to evaluate the mixing, two horizontal layers of differently colored wood chips will be placed inside the windrow to be turned. After the turning process has been carried out, samples will be taken with the help of a specifically manufactured core drill. These samples provide information on the mixing due to the volume fractions of the bulk materials contained. The wear evaluation is carried out on the basis of the material removal on coated roll segments. For model calibration in the simulation program, the bulk materials are subjected to various measurement procedures. After an initial simulation evaluation, several optimization tests will be carried out, in the course of which the used particle shapes and contact models will be modified.