Impact of Mountain Pine Beetle-Attacked Lodgepole Pine Logs on Veneer Processing

Abstract

Pilot plant tests and mill trials were conducted to quantify the impact of using mountain pine beetle(MPB)-attacked lodgepole pine (Pinus contorta Dougl.) wood on green veneer processing, and determine if it makes economic sense to sort and process MPB logs separately from normal logs of white SPF (spruce-lodgepole pine-alpine fir) mix for plywood manufacturing. The results demonstrated that log dry-out, improper log conditioning, and veneer peeling contribute to the breakage of veneer ribbon, and in turn, loss of veneer recovery at the green end when processing MPB wood. Compared with the green SPF veneer controls, green MPB veneer has lower moisture content (MC) with smaller variation. The MPB veneer can be clipped narrower with an equivalent of 1% increase in recovery due to less width shrinkage, and be sorted more accurately requiring only two green sorts: heart and light-sap. The MPB veneer can also be dried faster with a reduction in drying time by about 25% for the heart veneer and 35% for the light-sap veneer. However, due to higher volume of narrower random sheets and increased waste from manual handling and composing, the net recovery of the MPB logs is about 8% lower than that of the control SPF logs. Furthermore, the color of the stained MPB veneer is lightened after drying, but it still causes interference with visual grading. Since MPB wood has unique MC and processing characteristics, it is recommended that it be sorted in the log yard when its proportion reaches about 10% of the total logs procured.