Enhanced simultaneous saccharification and fermentation of Napier grass and Napier silage for two stage bio-hydrogen and methane production using organosolv and hydrothermal

Abstract This study aims to enhance the simultaneous saccharification and fermentation (SSF) of Napier grass and silage for two-stage bio-hydrogen and methane production using organosolv and hydrothermal pretreatments. The organosolv pretreatment of Napier grass and silage, catalyzed by sodium hydroxide and sulfuric acid, substantially increased hydrogen yields 1.34 and 1.55 times compared with those of untreated Napier grass and silage, respectively. In the second-stage fermentation, the hydrogenic effluents from each treatment were further converted to methane. A maximum methane yield of 278.2 ± 3.2 and 263.4 ± 6.2 mL/g-substrateadded was obtained from the effluents of the auto-catalyzed (without catalysts) organosolv-pretreated Napier grass and silage, respectively. Consequently, a maximum total energy yield of 11.0 kJ/g-substrateadded and 10.4 kJ/g-substrateadded was gained from the auto-catalyzed Napier grass and silage, respectively. The organosolv pretreatment of Napier grass and silage was more successful in the two-stage SSF hydrogen and methane production than the hydrothermal pretreatment.