Technology and systems for efficient stump harvesting under ecological restrictions

In the process to replace fossil fuels with renewable energy sources a large expansion of biofuel-based energy production has begun and is ongoing in Sweden. This has led to an increased demand of biomass from the forest, which makes stumps an interesting source of bioenergy. Stump harvesting is today limited due to technical and environmental constraints, due to the excavator-based technology and harvesting technique. The aim of the project is to develop new knowledge and technology for stump harvesting and to analyze various systems of stump harvesting. The hypothesis is that a harvest of the central part of the stump as an extension of the butt log could be done much more rational and environmentally friendly than today's stump harvesting. The ecological impact of stump harvesting should be so small that it can be done on most sites. The project includes four studies: 

1. Torque necessary to uproot and to cut the roots around pine stumps have been study to see if development of stump harvesting heads that twist the stump could be possible. The results show that large torques are required to harvest stumps.
2. A system analysis on technologies for efficient stump harvesting has been made where a conventional system has been compared to an integrated system for simultaneous stump and stem harvest. The integrated system consisted of a feller-puller, a processor and a forwarded and the central part of the stump was harvested with the tree and forwarder to the landing as a extension of the but log. The results show that an integrated system could be profitable.
3. To the summer (2012) a field study will be made where the productivity and ground disturbance of two stump harvesting heads will been compared in fresh and older clear cuts. This is made to investigate what the soil disturbance is after stump harvesting in a scientifically way.
4. Time consumption on new technology for stump harvesting. A time study of a new prototype aggregate for stump harvesting head will be made.