Biogas production from lignocelluloses by N-methylmorpholine-N-oxide (NMMO) pretreatment: Effects of recovery and reuse of NMMO

The effects of N-methylmorpholine-N-oxide (NMMO) pretreatment on barley straw and forest residues were investigated for biogas production. The pretreatments were performed at 90 °C with 85% NMMO for 3-30 h. The best pretreatment conditions resulted in 100% improvement in methane yield during the subsequent digestion compared to that of the untreated lignocelluloses. Methane yields of 0.23 and 0.15 Nm3 CH4/kg VS were obtained from barley straw and forest residues, respectively, corresponding to 88% and 83% of the theoretical yields. In addition, the effects of the pretreatment with recovered and reused NMMO was also studied over the course of five cycles. Pretreatment with recycled NMMO showed the same performance as the fresh NMMO on barley straw. However, pretreatment of forest residues with recycled NMMO resulted in 55% reduction in methane yield.