Biohydrogen production from brewery wastewater in an Anaerobic baffled reactor. A preliminary techno-economic evaluation

Abstract

The study aimed to optimise the dark fermentation (DF) process for producing biohydrogen from brewery effluent using an anaerobic baffled reactor (ABR). Temperature, pH, and retention time were considered as the operating parameters. The output parameters were hydrogen production rate (HPR), chemical oxygen demand (COD) removal efficiency, and total volatile fatty acids (tVFA). The maximum HPR was 18.16 mL/h, and the lowest was 0.94 mL/h, all at 35°C, even though the operating pH in both cases was different, pH 5 and 2.5, respectively. Under pH conditions ranging between 4 and 7, high COD removal was more prominent, with 60.81% COD removal found at a pH of 6.5. pH played a pivotal role in the process's general performance; at the same retention time (10.0 h) and temperature (35 ºC), a hydrogen yield of 2.77 mmol/gCOD at pH of 2.5 and 30.98 mmol/gCOD at pH of 5 were recorded. The Design-Expert software was used to design the experimental runs. The model produced predicted an optimum operating temperature of 36℃, pH of 5.6, retention time of 10.2 h and 17.05 mL/h HPR, 49.88% COD removal efficiency and 683 mg/L VFA concentration in the effluent were predicted. A techno-economic evaluation was conducted to assess the feasibility of scaling up the dark fermentation of brewery wastewater at the optimum conditions specified in this research. A 40 million litre per annum dark fermentation system was preliminarily designed, and about 5.5 GL/yr of hydrogen was expected under normalised conditions. The hydrogen cost was US$ 7.35/kg, with a payback period of 5.9 years and a return on the interest of 25.59%.