Dewatering properties of pulps made from different parts of a Norway spruce (Picea abies)

A single Norway spruce tree (Picea abies) was manually fractionated into heartwood, sapwood, juvenile wood and branches. These fractions were chemically pulped, individually, in laboratory scale. The pulps were characterized and investigated in relation to dewatering behavior and sheet strength properties. An unbleached and unbeaten commercial kraft pulp from softwood fibers was used as a reference, and the fractionated pulps were within the same range in all tested properties. The fractionated pulps were then compared with each other, and fiber characteristics were used to explain differences in dewatering and strength. Heartwood pulp results in stronger and stiffer papers that are harder to dewater. Sapwood pulp gives more open network structures resulting in easy dewatering and high air permeance, although with lower strength properties compared to heartwood. Pulp from Juvenile wood gives s quite strong but brittle sheets, with efficient dewatering. Pulp from branches gives paper sheets with efficient dewatering, air permeance and relatively high elongation of break but lower strength. The results show that there is definitely potential for utilizing more parts of the trees for pulp and paper making, especially when tailoring the raw material origins after preferred paper properties.