Conversion of bark-rich biomass mixture into fermentable sugar by two-stage dilute acid-catalyzed hydrolysis

Despite high availability and low cost, bark has not actively been considered as a biomass feedstock for producing bio-based products due to its high content of extractives and lignin. In this study, to investigate the feasibility of utilizing bark-rich sawmill residues for producing value-added materials, the mixed Hemlock hog fuel/pin chips (85:15 by dry weight) from a local sawmill were converted into fermentable sugar by two-stage dilute sulfuric acid-catalyzed hydrolysis. Combining the sugar yields from the first-stage (190 °C for 150 s with 1.1% acid) and second-stage (210 °C for 115 s with 2.5% acid) hydrolyses, which aimed to maximize the recovery of mannose/galactose and glucose, respectively, 13.6 g of glucose (46% theoretical maximum), 10.5 g of mannose and galactose (98% theoretical maximum), and 2.8 g of xylose (85% theoretical maximum) were obtained per 100 g of the original dry feedstock.