Comparison of two stump-lifting heads in final felling Norway spruce stand

Abstract

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 m 3 solid over bark (sob)/E 0 (4.8 ton D /E 0 ) without site preparation using a Väkevä Stump Processor, and when lifting spruce stumps with a diameter of 40 cm, the productivity was 14.9 m 3 sob/E 0 (6.5 ton D /E 0 ). 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.

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

“…The results of the present study largely agree with those of Laitila et al (2008) and Kärhä & Mutikainen (2009), especially concerning the amount of productive time spent in different activities. Splitting stumps and shaking off impurities (SPLIT), and stump piling (PILE) proved to be the most time consuming work elements with the widest spread of values around the means (Table 4).…”

“…According to Kärhä & Mutikainen (2009), 14 % (ca. 1.2 TWh or 0.23 million ODT) of wood-chip production in Finland was derived from stumpwood in 2008.…”

“…The stumps are then shaken to remove most of the attached soil and stones, and piled for subsequent transport to the roadside and on to the receiving plant. As only one scientific paper (Laitila et al 2008) and some conference contributions (Kärhä & Mutikainen 2009;Lazdinš et al 2009;Jouhiaho et al 2010) have appeared presenting recent time studies on stumpwood harvesting there is a need for further research in order to get a better understanding on the factors that have an impact on the productivity of stumpwood harvesting operations.…”

Vertical force requirement for stump lifting

“…Lifting the stumps left in the soil is one of the most energy demanding forest operations (Laitika et al 2008;Kärhä, Mutikainen 2009). Szepesi (1966) estimated the force required for stump extraction, based on the weight below the cutting plane, the branching roots and the texture of various soils, as several hundred thousand Newton.…”

Technology and energy balance in stump harvesting with MCR500

“…Two stump-lifting technological patterns, based on two different buckets, suitable to aggregate with the same excavator, were compared. The main difference between both cases was the diverse mode of the implementation of the necessary movements by a relevant bucket to get the stump out of the ground [4]. The description of the new technology for stump uprooting is available in the recent review (2015) of the newest technologies to obtain bioenergy from forest in Finland.…”