Benefits and oppotunities of separating various tree components

The potential of separating Norway spruce wood raw material into assortments having dissimilar wood and fiber properties is demonstrated using experimental material. The properties of whole trees coming from different stands having varying mean tree age and diameter, as well as the properties of the logs taken from those trees and classified according to age and diameter, are clarified. Fiber length, width and coarseness with wood basic density, and moisture and heartwood content are considered.

Sorting the wood raw material by log age appeared to be more effective than sorting by log diameter. The youngest logs seem to be more suitable for high opacity mechanical pulps and for high tensile strength chemical pulps. The oldest logs provide the most suitable raw material for strong mechanical pulps. This kind of logs having long and coarse fibers may also be suitable for chemical pulps used in sack-papers. The rest of the logs, medium-aged, are apparently the best raw-material assortment for reinforcement pulps. The variation in properties between logs within assortments was observed to be less than within the whole experimental material. This implies that grouping into assortments will reduce pulp property variation.