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Work system study of three stump-lifting devices in Finland

Stump and root wood procurement has increased in the twenty-first century in Finland. Potential amounts of techno-economically harvestable stump wood account for 2–11 TWh, depending on the cost-efficiency of the stump procurement. For increasing stump wood consumption of energy plants lifting technology of stumps requires further development. In this research, three stump-lifting devices were compared. These devices were connected to human–machine systems which operated in similar study stands. Based on the machine, time, stand, cost and biomass data, productivity and cost-efficiency of the stump-lifting devices were determined in the work system study. The productivity of stump lifting was 16.4 m³ sob/process-hour (7.1 tD/process-hour) to the stumps with a diameter of 40 cm on sites processed using Terosa stump-lifting device and Hakkila's biomass model were used in the system. Further, the stump-lifting costs with Terosa were around 37% (sob/E0-hour) lower than those of Väkevä and Xteho. In this respect the machinery equipped with Terosa provides the cost-efficient stump-lifting system. Based on herein reported study, it can be stated that Terosa is a promising stump-lifting device that enables cost-efficient extraction of stump wood.