Pretreatment of oil palm empty fruit bunch (OPEFB) by N-methylmorpholine-N-oxide (NMMO) for biogas production: Structural changes and digestion improvement

- Oil palm empty fruit bunch was pretreated by NMMO.
- The pretreatment was performed at 90, 120 °C for 1, 3, 5 h using NMMO 73%, 79%, and 85%.
- The pretreatment increased the amorphous phase of OPEFB's cellulose up to 78%.
- Methane yield was improved up to 98.3% compared to the theoretical yield.