Novel extracting methods for conifer stumps

Stumps can play an important role in providing a renewable raw material for energy generation or biorefining. Currently, it is an underutilized resource in the Scandinavian countries because of the high harvesting cost and contaminant problems of the raw material produced. The objectives of this study were: (1) to evaluate the efficiency and functionality of a forwarder-based stump extraction device that splits and vibrates the stump during lifting, (2) to evaluate the efficiency and functionality of a crawler excavator-based stump lifting device that cuts off the lateral roots and lifts the stump, and (3) to create time consumption models for the aforementioned stump extraction systems based on field studies. Both stump extraction devices operated without any unnecessary delays, as there were no breakdowns but the effective stump harvesting time of the crawler excavator-based extraction device was markedly lower than the time taken by the forwarder-based extraction device. Compared to previous studies, the efficiency of the studied devices (expressed as time consumption per harvested stump) was not competitive relative to the conventional method, in which a crawler excavator is equipped with a stump extraction head that breaks up and lifts the stump and the lateral root system completely.