Influence of C/P and C/N ratios and microbial characterization in hydrogen and ethanol production in an anaerobic fluidized bed reactor

The aim of this study was to evaluate the influence of C/P and C/N ratios on the production of hydrogen and ethanol in four anaerobic fluidized bed reactors: R1 (C/N = 100), R2 (C/N = 150), R3 (C/N = 200), and R4 (C/N = 250). The hydraulic retention time (HRT) was maintained at 2 h, and the C/P ratios varied from 300 to 1100. Reactors were filled with grounded tire and fed with synthetic substrate containing glucose (5000 mg L−1). The effluent pH was around 3.7. The highest values for hydrogen yield (HY) and hydrogen production rate (HPR) were obtained at a C/P = 700 ratio in all reactors. The best performance was achieved at R3 (C/N = 200): HY of 0.76 mol H2 mol−1 glucose and HPR of 0.70 L h−1 L−1. The highest value for ethanol yield was obtained at C/P = 700 in R1 (1.5 mol EtOH mol−1 glucose). Ethanol- and hydrogen-producing fermenters, such as Ethanoligenens sp. and Clostridium sp. were identified by molecular analysis. Lactobacillus sp. was also identified in this study.