Pine and spruce stump harvesting productivity and costs using a Pallari KH 160 stump-lifting tool

Even though stumpwood may become a significant part of the future fuel mix for combined heat and power plants in Sweden, the harvesting of stumps after regeneration felling is still only performed on a trial basis. Results from time studies on two, 23 tonne, excavators fitted for stump lifting, together with follow-up data on stump lifting and forwarding, are presented. Lifting, splitting, and piling the stumps accounted for 17, 32, and 32%, respectively, of the total productive work time. A predictive model was developed to estimate operational times and productivities when lifting pine and spruce stumps. Stump diameter, species, and terrain conditions contributed significantly to the fit of the model. The model predicts that productivity of stump lifting in spruce sites with easy terrain conditions and average stump diameters of 20 and 40 cm will be 1.23 and 4.19 oven-dry tonnes (ODT) per productive work hour, respectively. This is 43% higher than in pine sites with difficult terrain conditions and the same diameters. In the follow-up data, the productivity in stump lifting varied from 1.5 to 2.9 ODT per productive work hour while the cost for lifting and extraction to roadside varied from 37.8 to 59.4 €/ODT.