Bioethanol production from lodgepole pine by SO2-catalyzed steam explosion

In this study, the beetle-killed lodgepole pine from the Province of British Columbia, Canada was used as the raw material for steam explosion to investigate the effects of the process of bioethanol production with enzymatic hydrolysis and subsequent fermentation. The results indicated that the lower SO2 absorption and the lower moisture content (dry basis) of the raw material affected the efficiency of the steam explosion; Water-washing on the pretreated substrate had no significantly influence on the enzymatic hydrolysis. The cellulose-glucose conversions were kept as 42% without significant variation while the substrate consistency increased from 20 mg/mL to 150 mg/mL, which implied that increasing the substrate consistency had no significant influence on enzymatic hydrolysis. Additionally, the fermentation results showed that the exploded substrate without water-washing was beneficial for subsequent fermentation. The ethanol yield in SHF and SSF only could reach 66% and 55%, respectively, compared with the theoretical ethanol yield. As a result, applying SO2-catalyzed steam explosion for enzymatic hydrolysis with lower SO2 absorption and lower moisture content of raw material is not very efficient and needs further optimization for the lodgepole pine.