Improvement of fermentable sugar recovery and bioethanol production from eucalyptus wood chips with the combined pretreatment of NH4Cl impregnation and refining

Abstract A combined pretreatment of NH4Cl impregnation and refining was developed to recover the fermentable sugars and improve the bioethanol yield. The xylose was recovered to decrease the cost of bioethanol production, moreover, the impregnation using nonmetal salt had little influence on the environment, and the energy consumption of the refining process was hugely reduced by the impregnation. The results showed that a high-temperature, short-time impregnation (170 °C, 10 min) led mainly to hemicelluloses degradation, where 97.4 % of the xylose was recovered from the impregnation liquor. 97.9 % of the cellulose in the refined solid substrate (SS) was converted to glucose by enzymatic hydrolysis, and 80.3 % of which was further fermented to bioethanol. The pretreatment energy efficiency was up to 260 g sugar/MJ, nearly three times higher than that using H2O impregnation and refining. Finally, the bioethanol yield (BY) and the xylose recovery reached to 189.75 and 150.95 g/kg wood, respectively.