EXPERIMENTAL LAB-SCALE BIOGAS PRODUCTION BY ANAEROBIC CO-DIGESTION OF AGRICULTURAL RESIDUES AND BREWERY WASTEWATER

Abstract

As a result of environmental and economic concerns, anaerobic co-digestion process has gained increasing interest as a viable technology for both energy production and waste treatment. In this work, anaerobic co-digestion of agricultural residues (animal slurry and corn grains) and wastewater from a local brewery plant was studied using a laboratory-scale experimental installation. Multiple batch experiments (Tst1-Tst7) were carried out in which the influence of the substrate mixture ratio, the temperature and the purging of N₂ of the reactor on the process was analyzed. Batch anaerobic-digestion experiments were performed at initial pH values between 7.5÷7.9 and at two temperature regimes (termophilic and mesophilic) and the substrates involved in the experiments were characterized using solid biofuels European Standard (EN 14774, EN 14775, EN 14918, EN 15297). The biogas was characterized by determining the CH₄, CO₂, and H₂S fraction over time. The best results were obtained when nitrogen purging was used to minimize the exposure of the substrate mixture to oxygen at an operating temperature of 45°C and a volume ratio of animal slurry to wastewater of 3:1 and 150 g of corn grain. Higher operating temperature and N₂ purging had a positive impact by increasing biogas production and decreasing the H₂S fraction of the total produced gas.