Effect of Aerobic Hydrolysis on Anaerobic Fermentation Characteristics of Various Parts of Corn Stover and the Scum Layer

To solve the difficulty of lignocellulose hydrolysis and the formation of crusted scum in anaerobic fermentation, various parts of corn stover, i.e., pith, rind and leaf, were subjected to a two-phase processing including aerobic hydrolysis (AH) and anaerobic fermentation. The results showed that AH significantly broke down the lignin structure of the various components of corn stover and increased the rate of lignin degradation. After 16 h of AH, the lignin degradation rates of the pith, rind and leaf were 4.20%, 3.91% and 4.90%, respectively, and the acetic acid produced accounted for more than 60% of the total amount of volatile fatty acids (VFAs) and ethanol. After hydrolyzing the pith and rind for 12 h and the leaf for 8 h, the maximum methane yields of fresh mass volatile solid (VS) were 323 mL g−1, 251 mL g−1 and 264 mL g−1, respectively, which were increased by 35.02%, 30.05% and 8%, respectively, while the fermentation cycle of T90 (90% of the total gas production) was shortened by 4–5 days. After hydrolyzing the rind and leaf for 12 h and the pith for 16 h, the thicknesses of the scum layer were only 7.1%, 13.6% and 18%, respectively, of that of the untreated group, indicating that AH coupled with anaerobic fermentation can effectively degrade lignin, reduce the thickness of the scum layer and increase the methane yield.