Anaerobic Biohythane Production in an Internal Two-Stage Bioreactor: Kitchen Waste Concentration Optimization

An internal two-stage bioreactor constructed with a hydrogen chamber and a methane chamber with a working volume of 300 mL and 4700 mL, respectively, was operated using various kitchen waste (KW) concentrations from 10 to 80 g COD/L with a hydraulic retention time of 2 days to characterize the biomethane production performance. The results showed that daily biohythane production exhibited a similar increasing trend at KW concentrations of 10 to 40 g COD/L. The peak biomethane production was 2481 mL/day at a KW concentration of 40 g COD/L. The KW concentration could also affect the COD, carbohydrate, lipid, and protein removal efficiencies. These removal efficiencies were somehow dependent on the KW concentration, with two notable KW concentration groups of 10–20 g COD/L and 40–80 g COD/L. After 80 days of cultivation, Firmicutes dominated the hydrogen chamber, and Methanobacteriaceae and Methanomicrobiaceae dominated the methane chamber. This study presents the optimal KW concentration for high biohythane production efficiency in a novel internal two-stage bioreactor and reveals the dominant microorganisms in its microbial community.