Enhancement of substrate solubilization and hydrogen production from kitchen wastes by pH pretreatment

Pretreatment at different pHs was adopted in this study to enhance the substance solubilization and hydrogen production from kitchen wastes through anaerobic digestion. After a pretreatment set at pH = 13, solubilization of kitchen wastes improved substantially as the concentration of soluble carbohydrate, soluble protein, lipids and soluble chemical oxygen demand increased by 283.1%, 203.2%, 259.1% and 108.2%, respectively, as compared with those of the control. The maximum hydrogen production potential reached 105.38 mL/g VS after the pretreatment, which was 2.66 times that of the control. Furthermore, butyric acid and acetic acid were the major components in the total metabolites after fermentation, while propionic acid had a relatively low concentration. Finally, the concentration of exoprotein and exopolysaccharide within extracellular polymeric substances (EPS) kept increasing during the initial 14 and 9 hours, respectively, then decreased afterwards. However, the concentration of DNA increased throughout the whole stage. The total EPS might indirectly indicate the anaerobic digestion process. These findings may represent a feasible method for high-quality treatment of kitchen wastes.