Renewable pellets obtained from aspen and birch bark

Abstract

In the industrial processing of logs, large amounts of bark can be utilized as pellets. This study sought to establish conditions for the efficient use of bark, in the form of pellets, as a solid, renewable fuel. First, the physical properties of the bark (10% moisture content, 618-kg/m3 density for aspen, and 749-kg/m3 density for birch) and pellets obtained from the shredded bark were determined. Then, the calorific properties (calorific value, calorific density, and ash content) of the shredded native bark and bark treated at 180 °C, 200 °C, and 220 °C for 1h, 2h, and 3 h were determined. The sawdust samples that underwent the torrefaction treatment were analyzed to find the mass loss. The mass losses of the birch bark were 20.0% (native bark) to 39.0% after a heat treatment at 220 °C for 3 h. An increased calorific value, up to 9.6%, showed that both the temperature and duration of the treatment improved the calorific properties of the bark. The findings of this paper highlighted the fact that bark can be used as a fuel source in log processing factories.