Evaluation of Forest Thinning Materials for TMP Production, 2005 Engineering, Pulping & Environmental

The effect of suppressed growth on the fundamental properties of wood fiber was evaluated by SilviScan analysis and tracheid measurement. Suppressed growth reduced cell tracheid length, but the high content of mature wood may translate into longer fibers overall. In pilot-scale refining experiments, blending 25% chips from small-diameter trees (SMD) with 75% mill wood chips produced slightly better quality pulp compared with pulp from a control mill wood chip sample. The pulp from the SMD mix had slightly lower shives and fines content than that of the control pulp. Handsheets from the SMD mix pulp had improved tensile strength and optical properties compared with the control. We conclude that suppressed growth trees are superior to normal growth trees for thermal mechanical pulp production because of uniformity in cell geometry, thin cell walls, and higher content of mature wood. Moreover, the thin cell walls of suppressed growth trees require less refining intensity or energy to produce good quality pulp.