After the pretreatment with ionic liquid and co-solvent, 27.1–
60.4% of the lignin was removed from the water hyacinth, the crystallinity of the structure was decreased, and the biogas yield and
methane concentration were increased by 16.3–97.6% and 13.2–
28.3%, respectively. When the water hyacinth was pretreated at
120C for 120 min by [Bmim]Cl/DMSO, the biogas production
was the highest and the lag phase was one day. Higher pretreated
temperature and longer pretreated time against the anaerobic
digestion of the water hyacinth. The recovery rates of ionic liquid
and co-solvent were all over 90%.