Thermophilic biohydrogen production using a UASB reactor: performance during long‐term operation

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AbstractBACKGROUNDThe efficiency of H2 production by dark fermentation described in the literature is around 50% of the maximum theoretical value and the experiments are mostly carried out over short‐term operations. This present study evaluated H2 production in a UASB (upflow anaerobic sludge blanket) reactor operated at 55 °C for 366 days using a synthetic substrate based on sucrose. The reactor response to an increased organic loading rate (OLR) was assessed by applying three different hydraulic retention times (HRTs): 12 h (211 days), 6 h (71 days), and 2 h (84 days).RESULTSCH4 was observed in the biogas during startup. The highest average values of the molar H2 flow rate (MHFR), volumetric H2 production rate (VHPR), and H2 yield (HY) were achieved at a HRT of 2 h, and were, respectively, 14.00 ± 5.24 mmol h−1, 75.33 ± 24.65 mL H2 L−1.h−1, and 1.73 ± 1.14 mol–H2 mol‐suc−1. Considering only the unstable steady‐state period, HY average at a HRT of 2 h was 2.56 ± 0.84 mol–H2 mol‐suc−1.CONCLUSIONOperational conditions were found to be the main factors responsible for removing methanogenic microorganisms from the system. Increase in the OLR enhanced H2 production and the ethanol pathway proved to be favorable for H2 production. © 2015 Society of Chemical Industry