Comparison of two stump-lifting heads in final felling Norway spruce stand
The use of stump and root wood chips has increased very rapidly in the 21st century in Finland: in the year 2000, the total consumption of stump wood chips for energy generation was 10 GWh, while in 2010 it was approximately 2 TWh. Metsäteho Oy and TTS Research evaluated two stump-lifting devices for the lifting of Norway spruce (Picea abies) stumps. The productivity and costs of stump lifting were determined. There was one base machine with one operator in the time study. When lifting stumps with a diameter of 30 cm, the effective hour productivity of stump lifting was 11.2 m3 solid over bark (sob)/E0 (4.8 tonD/E0) without site preparation using a Väkevä Stump Processor, and when lifting spruce stumps with a diameter of 40 cm, the productivity was 14.9 m3 sob/E0 (6.5 tonD/E0). When the site preparation (mounding) was integrated into lifting work, the stump-lifting productivity decreased 21–27%. The stump-lifting productivity of the other lifting head (Järvinen) was lower than that of the Väkevä Stump Processor. Some development suggestions for the Järvinen lifting head were presented and discussed. The cost calculations showed that stump-lifting costs are extremely high when stump diameter is less than 20 cm. Therefore, the study recommended a change in the current stump-harvesting guidelines of Finland: The study suggested that all the stumps with a diameter less than 20 cm should be left on the harvesting site.
Received 10 May 2012 Accepted 14 September 2012 Published 31 December 2012