Epsilon Archive for Student Projects

Abstract

In Sweden, the demand for bio energy has increased in recent years due to the current energy and climate debate. In 2008, the energy supply of Sweden was 612 TWh, biofuels accounted for 123 TWh of these. Stumps have been highlighted as a potential fuel in recent years and the Swedish Forest Agency expects a technically and biologically feasible potential of 20.7 TWh annually between 2010 and 2019. The idea of utilize stumps is not new. During the 19th century stumps were used for tar production and during the 70’s and 80’s attempts were made to use stumps in the pulp industry. Recent tests with stump lifting for energy use have been done within the Project Bioenergy Farms which runs from 2008 to 2011. Norra Skogsägarna (a forest owners association in he north of Sweden) has had the responsibility for these tests within the project.

The aim of the thesis was for the behalf of Norra Skogsägarna examine how the factors transportation distance, object size and quantity of stumps per hectare affected the costs of three different transport systems.

A system where the stumps coarse crushed at the road side was the cheapest system and profitable up to about 84 km. A system where the stumps were crushed at a terminal before transport to the heating plants were only profitable up to 9 km. Delivering stumps uncrushed directly from the forest to the heating plant was profitable up to about 22 km. For all systems, however, the size of the site played a large role but the most important factor was the amount of stumps per hectare. Also lifting cost, hauling cost and moisture content had a significant impact on the total system cost.

The lifted stump volume (m3f) was on average 35% of the harvested stem-wood volume (m3fub).