Hydrogen and ethanol production in anaerobic fluidized bed reactors: Performance evaluation for three support materials under different operating conditions

The objective of this study was to evaluate the influence of different support materials (polystyrene – R1, grounded tire – R2 and polyethylene terephthalate (PET) – R3) on producing hydrogen and ethanol using three anaerobic fluidized bed reactors. Each reactor had a total volume of 4192 cm3 and was fed with media containing glucose as the carbon source (4000 mg L−1) with an influent pH around 5.0 and an effluent pH of about 3.5, a hydraulic retention time (HRT) of 8–1 h at a temperature of 23 ± 2 °C, with thermal treatment of the inoculum. For hydrogen production, the best performance was achieved with R2 (2.11 mol H2 mol−1 glucose), providing the highest H2 content in biogas (60%). In all reactors, the predominant soluble metabolites were acetic acid, butyric acid, lactic acid and ethanol, with small amounts of propionic acid. The reactor R2 produced more acetic and butyric acid (434.74 and 1013.61 mg L−1, respectively). However, reactor R3 showed a better performance for ethanol concentration (1941.78 mg L−1).

► The biological production of hydrogen and ethanol was evaluated in AFBR. ► The AFBRs contained polystyrene (R1), grounded tire (R2), and PET (R3). ► The best performance was achieved with reactor R2 (2.11 mol H2 mol−1 glucose). ► The R3 showed a better performance for ethanol concentration (1941.78 mg L−1).