Kraft Pulping Using Red Pine (Pinus densiflora) Root Biomass

Abstract

The competition for biomass between the bioenergy and conventional forest product industries has resulted in increased utilization of unused residual wood biomass. This study investigates the anatomical, chemical and pulping characteristics of red pine root biomass to focus on kraft-pulping raw material. In a chemical compositional analysis, the root biomass was found to have lower Klason lignin and higher polysaccharide contents than the trunk biomass. Meanwhile, in a carbohydrate compositional analysis, the root biomass showed higher cellulose and glucomannan, but lower xylan compared with the trunk biomass. In terms of anatomical features, the cell wall thickness in earlywood was not significantly different (3.8 μm for the trunk cell and 3.3 μm for the root cell), but that in latewood was significantly different (6.3 μm for the trunk cell wall and 3.8 μm for the root cell wall). In kraft pulping, the trunk biomass showed a better response to pulping than the root biomass in terms of the kappa number at the same pulping condition. In terms of fiber morphology, the trunk fiber was longer (2.2 mm) and thinner (30.6 μm) than the root fiber (2.1 mm and 32.9 μm). In terms of the polysaccharide loss during kraft pulping, xylan in the trunk and cellulose in the root was more vulnerable to pulping chemicals; however, glucomannan was the most vulnerable component to kraft pulping. Based on the tensile–tear plot, the root fiber showed better response to beating, but lower fiber strength.