Biochemical methane potential of brewery wastes and co-digestion with glycerol

Abstract

Beer production generates huge amounts of streams with high energetic potential. This work investigates the energetic valorization of the brewery wastes, trub (T) and spent grain (SG), by anaerobic digestion processes. T had a higher BMP (251±2 L CH4 kg-1 COD) than SG (191±3 L CH4 kg-1 COD). The methane yield (72±1%) and methane production rate (1.08±0.10 d-1) were also higher for T because of the recalcitrant nature of SG (55±1% and 0.21±0.01 d-1). The co-digestion ratio of 10%T + 90%SG produced 199±2 L CH4 kg-1 COD. Due to the high proteins content of T and SG, 54.0±6.6 and 30.5±1.7 respectively, crude glycerol (CGly) is a promising co-substrate, with high energy potential and ideal to optimize the C:N ratio for the anaerobic digestion process. The co-digestion with 10% (w/w) of CGly increased the methane production to 328±5 L CH4 kg-1 COD (yield = 94±2%). Adding higher concentrations of CGly caused inhibitions, decreasing the methane production. Therefore, it seems that the addition of, up to 10% (w/w), of CGly had a positive synergetic effect on the brewery wastes anaerobic digestion.