Synergistic influence of sequential alkaline-liquid hot water pretreatment on the fractionation of Pakchong grass, a hybrid cultivar of Napier grass

This study explores the fractionation of Pakchong grass as a biofuel feedstock, an area that lacks extensive research compared to elephant grass (Napier grass). A two-stage pretreatment strategy (sequential alkaline-liquid hot water (LHW)) was applied to this grass, known for its high cellulose content and favorable growth conditions. The results demonstrated that this approach substantially enhanced the delignification and extraction of hemicellulose, achieving high lignin removal rates up to 97.57 %, while retaining most of the cellulose. The optimal treatment combination (2 % NaOH for 90 min followed by LHW at 160 °C for 30 min) yielded a final biomass composition of 64.38 % cellulose, 28.79 % hemicellulose, and 1.15 % lignin. Structural analyses validated the efficiency of this two-stage pretreatment in improving biomass composition for sugar production. The results showed that sequential alkaline-LHW pretreatment could be an option in enhancing biomass readiness for subsequent enzymatic hydrolysis and fermentation. • Two-stage alkaline-LHW pretreatment was subjected to a Napier grass hybrid. • The optimal treatment combination was 2 % NaOH followed by liquid hot water at 160 °C. • Lignin was significantly removed by 97.57 %, leaving only 1.15 % left. • The deconstructed biomass showed a favorable composition for subsequent hydrolysis. • Sequential alkaline-LHW pretreatment can be an option for grass fractionation.