Comparison of Hydrogen Peroxide and Ammonia Pretreatment of Corn Stover: Solid Recovery, Composition Changes, and Enzymatic Hydrolysis

Three pretreatments, hydrogen peroxide pretreatment (HP), ammonia fiber expansion pretreatment (AFEX), and hydrogen peroxide presoaking prior to AFEX (H-AFEX), were employed to improve enzymatic digestibility of corn stover. Effects of varied chemical loadings on solid recovery, composition changes, and enzymatic hydrolysis by different methods were investigated and compared. The influences of the lignin solubilization and xylan removal from treated corn stover on subsequent enzymatic hydrolysis were assessed. The highest fermentable sugar yields of HP, AFEX, and H-AFEX processes following enzymatic hydrolysis at 15 FPU/g glucan for 72 h were 370.9, 497.8, and 527.6 g monosaccharides per kilogram of untreated dry biomass, respectively. For AFEX and H-AFEX, solubilization of 15–20% of the lignin and removal of 5–10% of the xylan resulted in close to optimal enzymatic digestion. As a result, a certain amount of lignin solubilization and xylan removal were necessary for an effective pretreatment for bioethanol production.