Concerns about climate change and fossil fuel shortages are encouraging interest in stumps, as alternative energy sources. Stumps are an almost unused resource in the context of bio fuels. Stump harvesting signifies an intensification of forest management compared with conventional stem-only or above-ground biomass-only harvesting. There are many benefits of stump harvesting. These include: the production of wood fuel, fossil fuel substitution, and improved soil preparation.Removing tree trunks in Hungary has been going on according to the principle of stump extraction, which means stumps are removed by grabbing technology. Experiments have been carried out to reduce the extraction force. In the Great Hungarian Lowland, where large areas require the operation implementation, stump extraction is done by special, hydraulic driven baggers equipped with a special bucket. During operation of the equipment, we carried out measurements of the extraction force and the time requirement. The experiments are designed to carry out the measurements with different soils and different tree species. According to our proposal the suitable force and torque required to remove stumps can be significantly reduced if before the lifting the soil — root connection is loosened. One of the possible ways to implement this task is the use of vibration. Since relatively great vibration power and wide domain of frequency are necessary, therefore we prepared the loosening machinery elements of alternating-current hydraulics system. Based on constructions variants we created a tractor-mounted experimental alternating-current hydraulic stump-loosening machine. It was designed with the ability to produce horizontal vibration in order to loosen stumps.
