The efficiency of nitrogen explosion pretreatment on common aspen – Populus tremula: N2- VS steam explosion

Abstract Steam explosion (SE) and nitrogen explosive decompression (NED) for pretreatment of common aspen (Populus tremula), were investigated in their potential to increase bioethanol and biogas yields from hardwood materials. The pretreated biomass was used in a separate enzymatic hydrolysis and fermentation steps, and in biogas potential measurements. Parameters describing biogas production, glucose and ethanol yields, hydrolysis and fermentation efficiencies were used as indicators to assess the efficiency of pretreatments. The highest glucose yields were achieved from the steam exploded material (200 °C), while the NED-pretreatment was more efficient at lower temperatures. For NED a glucose yield of 81.06 g/kg at 175 °C was achieved while the SE method resulted in 51.57–80.75 g/kg at a temperature range of 170–190 °C. The highest ethanol yields were 37.07 g/kg at 150 °C (NED) and up to 92.99 g/kg at 200 °C (SE). The highest methane yield of 167.7 g/kg was achieved with SE-pretreatment at 170 °C, while the NED resulted in methane yield of 104.7 g/kg at 125 °C. In both cases the methane yields decreased as the pretreatment temperature increased. Even though NED resulted at 175 °C in higher glucose yields compared to SE, the fermentation process was impeded.