Kraft Pulp from Norway Spruce (Picea Abies) Thinned at 30 Years Age, 1993 Pulping Conference Proceedings

This study illustrates the influence of growth rate on the kraft pulp properties of 30 to 35-year-old Norway spruce (Picea abies) removed during a thinning. Wood from the fastest growing stand had a mean annual ring width of 5.6 mm and a mean basic density of 323 kg/m³, whereas corresponding values for the slowest growing stand were 2,9 mm and 384 kg/m³, respectively. The remaining stands had intermediate ring widths and basic densities. Process and pulp characteristics were found to be similar for wood from stands with a mean annual ring width between 3 mm and 4 mm and a mean basic density ranging from 350 to 400 kg/m³ . Wood from the stand with a mean ring width exceeding 5 mm and a mean basic density of 323 kg/m³ had shorter fibers and longer cooking time to reach a certain kappa number, compared with wood from the other stands. Furthermore, this wood consumed more chemicals and yielded l-2 percentage units less pulp. The volume of wood needed to produce, 1 ton of pulp was 6.4 m³ for the fastest growing trees and 5.2 m³ for the slowest growing ones.