Effects of mountain pine beetle grey-stage infestation and chip moisture content on TMP pulping of lodgepole pine

We performed pilot-plant thermomechanical pulping on green and dry, mountain pine beetle-infested, grey-stage lodgepole pine sapwood chips with different moisture contents. The energy requirements and the tensile strength of the thermomechanical pulps (TMPs) from the dry, early-grey-stage chips were similar to those from the green chips, but there were indications of slightly higher energy requirements and lower tensile strength for the pulps from the late-grey-stage chips. The late-or early-grey-stage TMP had lower sheet density (because of the lower chip moisture content), lower ISO brightness, and higher handsheet surface roughness than the green TMP. Chip blends with 50% and 25% of late-grey-stage chips could be used to produce TMP pulps with energy requirement, tensile strength, handsheet surface roughness, and density similar to those of green TMP, but with lower ISO brightness. The fiber saturation points of the green and the late-grey-stage chips were estimated to be 23.1% and 22.4% (wet basis), respectively.