Ethanol and biogas production from birch by NMMO pretreatment

Birch wood was pretreated with N-methylmorpholine-N-oxide (NMMO or NMO) followed by enzymatic hydrolysis and fermentation to ethanol or digestion to biogas. The pretreatments were carried out with NMMO (wNMMO = 85%) at 130 °C for 3 h, and the effects of drying after the pretreatment were investigated. Enzymatic hydrolysis of the untreated wood resulted in 8%–10% of theoretical glucose yield after 4 days hydrolysis, while the NMMO pretreatment improved this yield to 91%. Consequently, ethanol production yield from NMMO-pretreated materials resulted in around 9-fold improvement compared to the untreated wood. On the other hand, drying of the pretreated wood had a negative impact and decreased the yield of enzymatic hydrolysis by 4%–10%. Digestion of the untreated wood with thermophilic bacteria resulted in maximum methane yield of 158 cm3 g−1 of VS in 30 days, while the NMMO pretreatment improved the methane yield up to 232 cm3 g−1 of VS (80% of the theoretical biogas yield) in just 9 days.

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► Birch wood was pretreated with NMMO at 130 °C under atmospheric pressure.
► NMMO pretreatment significantly improved the hydrolysis, ethanol, and biogas yields.
► Ethanol yield of birch wood was improved from 8.5% to 76.8% of theoretical yield.
► Biogas yield of birch wood was improved from about 55% (30 days) to 80% (9 days).
► Drying after pretreatment decreased the hydrolysis efficiency but not biogas yield.