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Abstract
Analysis of sequential hydrogen-methane and independent methane production were carried out in this study to investigate the optimal bio-energy production from kitchen wastes. The study indicated that production of hydrogen and the sequential methane achieved 75.0 and 287.4 mL/gVS, respectively, during the sequential hydrogen-methane process. Specifically, the sequential methane increased by 34.0% compared to independent methane production. Additionally, the measured concentration of total organic acids increased to 13,599.8 mg/L at the end of hydrogen fermentation, then decreased to 4,284.9 mg/L at the end of the sequential methane process. The major acid component was butyric acid in the sequential methane process as opposed to acetic acid in an independent process. Remarkably, it was found that the major component of extracellular polymeric substances in hydrogen producing sludge was exopolysaccharide, while in both methane producing processes it was exoprotein. The maximum measured concentration of exoprotein and exopolysaccharide reached to 84.3, 36.3 mg/gVS and 63.4, 30.4 mg/gVS, while DNA increased throughout the stages of the two methane processes. These findings may represent a feasible method for high energy achievement from kitchen wastes.