Biovalorization of brewery waste by applying anaerobic digestion

In the food industry, the brewing sector holds a strategic economic position: in the year 2013, the beer production of the EU-28 was equal to 383,553,000 hL. The brewing process includes chemical and biochemical reactions and solid-liquid separations, involving the generation of various residues and by-products, among which the major two fractions are brewer’s spent grain (BSG), and exhausted brewery yeast (BY). Although until today their main use has been for animal feed, in recent years, several studies have investigated the application of anaerobic digestion in order to revalue the brewery wastes. In this work, specific methane production (SMP) and first-order solubilisation (disintegration + hydrolysis) rates (ksol) for BSG and BY were evaluated. Biomethanation tests were performed in 5-L fed-batch stirred reactors at several substrate/inoculum ratios. The obtained SMP ranged from 0.255 L CH4 gCOD-1 for exhausted brewery yeast to 0.284 L CH4 gCOD-1 for brewer’s spent grain. The estimated ksol values ranged from 0.224 d-1 for BSG to 0.659 d-1 for BY.