Continuous alkaline pretreatment of Miscanthus sacchariflorus using a bench-scale single screw reactor

• A continuous pretreatment system based on screw extrusion was newly developed.
• Pretreatment was performed by combination of extrusion, soaking, and thermal reaction.
• 90.8% of theoretical glucose yield could be obtained with 10 FPU from 0.5 M NaOH-pretreated solids.
• SHF of high solids loading resulted in 85.0% of theoretical ethanol yield with 20 FPU.
• Theoretically, 172.0 g of bioethanol can be produced from 1 kg of dry biomass.

Miscanthus sacchariflorus ‘Goedae-Uksae 1’ (GU) was developed as an energy crop of high productivity in Korea. For the practical use of GU for bioethanol production, a bench-scale continuous pretreatment system was developed. The reactor performed screw extrusion, soaking and thermochemical pretreatment at the following operating conditions: 3 mm particle size, 22% moisture content, 140 °C reaction temperature, 8 min residence time, 15 g/min biomass feeding and 120 mL/min NaOH input. As a result of minimizing NaOH concentration and enzyme dosage, 90.8 ± 0.49% glucose yield was obtained from 0.5 M NaOH-pretreated GU containing 3% glucan with 10 FPU cellulase/g cellulose at 50 °C for 72 h. The separate hydrolysis and fermentation of 0.5 M NaOH-pretreated GU containing 10% glucan with 10–30 FPU for 102 h produced 43.0–49.6 g/L bioethanol (theoretical yield, 75.8–87.6%). Thus, this study demonstrated that continuous pretreatment using a single screw reactor is effective for bioethanol production from Miscanthus biomass.