Valorization of brewery waste slurry with glycerol as co‐substrate for hydrogen and butyrate production using dark fermentation

Abstract

AbstractBACKGROUNDAmong the methods to produce hydrogen biologically, dark fermentation stands out mainly due to its low operating requirements. Organic wastes, such as brewing industry waste slurries and glycerol, can provide a cost‐effective feedstock with the additional potential of generating value‐added byproducts, while addressing a wastewater treatment issue.RESULTSThe hydrogen production potential in dark fermentation of a high‐strength brewery waste slurry was optimized with a selected seed sludge, initial COD concentration of 50–60 g L−1, pH 6.4 and fermentation time of 30 h. The main end product was butyric acid, accounting for over 50% of the carboxylic acids. The efficiency of the process on the basis of volume of H2 obtained per gram of COD converted into organic acids was 393 ± 5 and 430 ± 6 mL without and with glycerol, respectively, and the molar ratio of H2 per mole of substrate was 71% of the theoretical molar yield when the fermentation is dominated by butyrate as the end product.CONCLUSIONSA proposed brewery sludge treatment system comprising dark fermentation followed by anaerobic digestion is promising and can be more advantageous than anaerobic digestion alone with an increase of 18.5% in energy potential. Alternatively, with recovery of valuable butyrate, a reduction in 4.5 kg of CO2 emissions per cubic meter of sludge treated can be achieved, with a 27% net loss in energy potential. © 2023 The Authors. Journal of Chemical Technology and Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry (SCI).