CHEMICAL AND MECHANICAL PULPING OF ASPEN CHUNKWOOD, MATURE WOOD AND JUVENILE WOOD

Chunking is a comminution technology developed at the Forestry Science s Laboratory in Houghton, MI, to enhance the economics and subsequent utilization of harvesting small-diameter trees from noncommercial or p oor-quality stands. Chunkwood, 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-diamet er aspen, high in juvenile wood content, as a raw material for chemica l and mechanical pulps. Blocky chunkwood particles were destructured b y crushing prior to chemical pulping by the kraft and neutral sulfite semichemical (NSSC) processes and mechanical pulping by the thermomech anical pulping (TMP) and chemithermomechanical pulping (CTMP) processe s. Conventional 19-mm chips, prepared from mature and juvenile wood as pen, were pulped by the same chemical and mechanical pulping processes for comparison purposes. Chunkwood yielded pulps lower in quality to chipped mature wood for kraft, NSSC, TMP, and CTMP, but better in qual ity to that obtained from chipped juvenile wood. Chunkwood consumed mo re energy in producing TMP and CTMP than chipped mature and juvenile w oods.