High-solid pretreatment of rice straw at cold temperature using NaOH/Urea for enhanced enzymatic conversion and hydrogen production.

A high-solid loading pretreatment using NaOH/Urea solution at -12 °C was proposed to pretreat rice straw (RS) for enhanced saccharify and hydrogen production. Results shown NaOH/Urea pretreatment exhibited excellent pretreatment performance at solid loading ranged from 10% to 100% (w/v) with an average reducing sugar conversion of 80.22% was obtained which was 31.89% higher than that untreated RS. Upon fermentation of 100% solid loading pretreated hydrolysate, the H2 yield of 72.5 mL/g-pretreated RS was calculated based on substrate consumption, which enabled 49.5% higher reducing sugar transfer to H2 through material balance. FTIR and XRD analysis further demonstrated that the cold NaOH/Urea pretreatment at 100% (w/v) could effectively disrupt the lignin structure and decrease the cellulose crystallinity. The present study suggested a high solid loading pretreatment with NaOH/Urea at cold temperature could be a valuable alternative for better techno-economic of the lignocelluloses - to - sugars - to H2 routes.