Bioethanol Production from Paper Sludge by Subcritical Water Pretreatment and Semi-simultaneous Saccharification and Fermentation

Paper sludge (PS) from paper mills has a significant potential for bioethanol production. In this study, waste-paper-containing PS is used as the raw material for bioethanol production because the annual waste paper utilization rate has increased globally. Although PS does not require delignification, the antiseptics and deinking agents in waste paper-containing PS inhibit enzymatic reactions such as saccharification and fermentation. Their removal is important, but it has not yet been reported. Using subcritical water pretreatment, the selective decomposition of enzyme inhibitors in PS is examined without the generation of other enzyme inhibitors. The optimum pretreatment conditions are identified as 240 °C, 3.3 MPa, 3 min, and pH 4.5. Glucose was obtained in 71