Research on Volatile Fatty Acids Production During the Anaerobic Digestion of Corn Stover Waste in Northeast China: Freeze-Thaw Pretreatment and Effect of Initial pH

The low temperatures in Northeastern China offer a promising and energy-efficient approach for lignocellulose pretreatment. The effects of freeze-thaw pretreatment on the microstructure of corn stover hydrolysis characteristics and fermentation acid production were investigated using corn stover as the raw material. The experimental results demonstrated that the reducing sugar release and soluble chemical oxygen demand (SCOD) values of corn stover following freeze-thaw pretreatment exhibited increases of 15.8% to 67.0% and 13.9% to 68.9%, respectively, compared to those of the control group. Freeze-thaw pretreatment modifies the microstructure of corn stover by breaking hydrogen bonds in the amorphous region between cellulose and hemicellulose, facilitating lignin removal. The acid yield of the treated corn stover under optimal pretreatment conditions is enhanced by up to 77.9% compared with the control group. The initial pH pronouncedly influenced the acid yield of anaerobic fermentation of corn stover, with the highest acid yield of 3.8 g/L observed at pH values between 7.5 and 8. This study provides theoretical guidance for the industrial development of a low-cost and low-energy consumption pretreatment method in lignocellulose wastes.