Delimbing hybrid poplar prior to processing with a flail/chipper

Processing whole trees into pulp chips with chain flail delimber/debarker/chippers (DDCs) is costly. Production rates of DDCs are limited by the residence time required to remove limbs and bark. Using a pull-through delimber, we delimbed trees prior to flailing and chipping, with the objective of speeding up the latter processes. Pre-delimbing increased the productivity of the DDC by about 10 percent. The reduced cost of flail/chipping did not cover the additional cost of delimbing with the machine mix tested, but changes to equipment and operating conditions might improve the situation. In the test configuration, the delimber processed 175 trees per productive hour, about half as many as the DDC. Delimbing separated about 35 dry pounds of limbs per tree, which may have higher value than the mixture of limb and bark residues produced by the DDC from whole trees.