Chemical and mechanical pulping of aspen chunkwood, mature wood, and juvenile wood

Chunking is a comminution technology developed at the Forestry Sciences Laboratory in Houghton, MI, to enhance the economics and subsequent utilization of harvesting small-diameter trees from noncommercial or poor-quality stands. Chunkswood, the product of chunking, has previously been evaluated for fuel, forest road building, and flake products and as a lightweight aggregate for concrete. The objective of this study was to explore the technical feasibility of using chunked small-diameter aspen (Populus tremuloides), high in juvenile wood content, as a raw material for chemical and mechanical pulps. Blocky chunkwood particles were destructed by crushing prior to chemical pulping by the kraft and neutral sulfite semichemical (NSSC) processes and mechanical pulping by the thermomechanical pulping (TMP) and chemithermomechanical pulping (CTMP) processes. Conventional 19-mm chips, prepared from mature and juvenile wood aspen, were pulped by the same chemical and mechanical pulping processes from comparison purposes. Chunkwood yielded pulps lower in quality to chipped mature wood for kraft, NSSC, TMP, and CTMP, but better in quality to that obtained from chipped juvenile wood. Chunkwood consumed more energy in producing TMP and CTMP than chipped mature and juvenile woods. Application : this paper presents laboratory pulping results for a different comminution technology that could be used to harvest underutilized or nonconventional forests.