Thermophilic Co-Digestion of Sewage Sludge and Brewery Spent Grain

This study examined the effectiveness of thermophilic sewage sludge co-digestion of and milled/non-milled brewery spent grain. In order to evaluate both the biogas potential and the biogas production rate, the experiments were conducted in batch-mode. Five runs were carried out, one of them concerned the anaerobic sewage sludge digestion (as control), whereas the others referred to the co-digestion of sewage sludge with addition of milled and non-milled brewery spent grain at doses of 5 and 10 g. The runs were conducted under thermophilic conditions (temperature 55±1°C) and lasted for 21 days. The effectiveness of the process was assessed on the basis of the volatile solids removal, biogas potential and the rate of biogas production. The physiochemical composition of reactor feed and digestate were characterized. The addition of the brewery spent grain resulted in increase of the biogas potential, but a decrease in the removal of volatile solids. In the case of biogas production rate, the highest value was recorded in the run with the addition of 10 g of milled and non-milled brewery spent grain (0.69 Ndm3dm-3d-1). There was no observed influence of milling on the thermophilic co-digestion effectiveness since the parameters specified revealed comparable values.