Evaluation of forest thinning materials for TMP production

We used SilviScan analysis and tracheid measurement to evaluate the effect of suppressed growth on the fundamental properties of wood fiber. 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 thermomechanical 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 may require less refining intensity or energy to produce good quality pulp. Application: The results of this study may help mills improve pulp production through better use of potentially neglected fiber resources.