Bioethanol production from alkaline-pretreated miscanthus by twin screw extrusion system at pilot scale

Previously, we had reported that Miscanthus sacchariflorus strain Goedae-Uksae 1 (MGU) could be a key energy crop in Korea due to its economic and environmental benefits. In accordance with its practical use for ethanol fuel, we developed the continuous pretreatment system using twin screw extruder at pilot-scale. Effectiveness of the alkaline pretreatment was used as benchmark. The pretreatment scale is approximately 150 kg/d of biomass and 15 L/d of 99.9% bioethanol can be produced through sequential processes; pretreatment, saccharification, fermentation, distillation, and dehydration.

The details of operating parameters of twin screw extrusion are 1) 6.5kg/hr of biomass input, 2) 390L/hr of 0.6M NaOH input, 3) 100^oC of temperature, and 4) 6 mins of residence time. Following the pretreatment, compositional changes of the solid hydrolysate were observed as follows: 40.3 wt% cellulose to 58.6 wt%, 24.1 wt% of hemicellulose to 23.5 wt%, 24.1 wt% of lignin to 12.3 wt%, and 4.0 wt% ash to 1.5 wt%. In partial SSF with high solid loading of pretreated MGU 149kg (DW), 36.7 kg of bioethanol was produced in 620L working volume (220L and 400L) with following conditions; 30FPU of Ctec2 and HTec, 100rpm, 72 hours, total water addition 185L, and 10% (v/v) inoculum of yeast. Finally, the theoretical ethanol yield was 78.8 %.