Produktivitet vid stubbskörd

Abstract: Stump harvest could be found in the late 1970's and the early 1980's. And now when the prices on energy are high it has become an interesting topic again. This work has been conducted within Holmen Skog's stump harvest testing in Norrköping. The purpose was to: Investigate the time consumption for harvesting and forwarding of stumps and the distribution of time on the different work phases; Make an economic analysis of stump harvest; Evaluate the number of, and quality of, the soil preparation were no extra measure was taken; Make an overview of the market of stump harvest devices. There are 3-4 different devices for stump harvest on the market and the most common is the Finnish device Pallari. It has been used in this study where harvest of ca 400 stumps has been studied and the time consumption has been recorded. The productivity of stump harvest was on average 4.1 tonTS/G0-tim and the mean size of the stump was 131 kgTS. Time consumption was different according to the diameter of the stump, tree species and the humidity of the soil. Stumps from spruce on fresh soil took less time to harvest than stumps from spruce on moist soil. Stumps from pine took more time to harvest than stumps from spruce. A stump with a diameter of 20 cm took 55-70 s to harvest and a stump with a diameter of 60 cm took 170-220 s to harvest. Due to the larger stumps higher volume was the production in tonTS/h considerable higher for large stumps. The cost for stump harvest and forwarding with this method was on average 77 SEK/MWh when 100 % of the stumps were removed. The average withdrawal was 54.7 tonTS/ha. Crane movement was the work phase that took the longest time, 48 % of the total time consumption was due to that phase. The number of soil preparation points was on average 3675 per hectare.