The effects of biopulping on chemical and energy consumption during kraft pulping of hybrid poplar

Poplar wood chips were treated in a rotary bioreactor for 10 days with the white-rot fungus Phanerochaete chrysosporium KCCM 34740 prior to kraft cooking, in an attempt to improve the pulping and refining efficiency of the wood chips. It was apparent that fungal pretreatment could simultaneously increase screened pulp yield and reduce the kappa number (residual lignin content) of the hardwood pulps. Additionally, lower initial pulp freenesses were observed, while the water retention values of each pulp were elevated, suggesting increased external fibrillation of the pulp fibers. Scanning electron microscopy confirmed this hypothesis. It was also shown that the refining energy required to develop (to achieve a target freeness) the unbleached kraft pulp fibers was significantly lower in fungal pretreated wood, without any deleterious influence on paper quality. These findings clearly suggest that fungal pretreatment of hardwood chips with P. chrysosporium KCCM 34740 can reduce the chemical loading and energy consumption during kraft pulping, and concurrently reduce the energy required during pulp refining.