Experiences with the utilization of bark-beetle-killed Norway spruce (Picea abies) pulp- wood in mechanical pulping operations for supercalandered magazine paper

摘要

Bark Beetles like Ips typographius or Pityogenes chalcographus are a big threat for European softwoods, especially for Picea abies (Norway spruce), the most important European tree species utilized in mechanical pulping operations. In recent years the amount of bark-beetle-killed (BBK) Norway spruce rose dramatically. Since 2001 more than 7.8 million m~3 (20 % of the total harvest) of BBK Norway spruce were harvested in south-west Germany. Seven mill-scale grinding and lab-scale bleaching trials were performed to investigate the influence of BBK spruce pulpwood on the pulp and paper quality. The results show that BBK Norway spruce can be used in mechanical pulping operations but the achieved pulp and paper quality is somewhat inferior compared with fresh and sound Norway spruce. The initial brightness was determined to be 60.2 %. At a freeness level of 75 °SR, BBK spruce gave a tensile index of 38.3 Nm/g while fresh Norway spruce produced laboratory sheets with a tensile index of 39.2 Nm/g. It was found that mainly secondary infestations with blue stain and red streak fungi are responsible for the lower pulp and paper quality produced from BBK Norway spruce wood. A rapid and consequent harvesting and processing of bark beetle infected forest stands could be a solution of this problem.