Assessment of sludge reduction and biogas production in two-step anaerobic co-digestion using sesame oil cake and sewage sludge

Abstract

The aim of this study was to investigate the sewage sludge reduction and biogas production using two-stage anaerobic co-digestion of sesame oil cake and sewage sludge. In the first stage (acidogenic fermentation), sesame oil cake (SOC) was acidogenic fermented to produce fermented sesame oil cake (FSOC). In the second step (anaerobic co-digestion), sewage sludge and FSOC were mixed in various ratios of (100:0 (R1), 70:30 (R2), 50:50 (R3), and 30:70 (R4)) and observed for 30 days at a mesophilization temperature of 35±2 °C. In the anaerobic co-digestion using FSOC as a co-feedstock, the volatile solids (VS) and total solids (TS) removal were in the range of 53.7–64.9 and 42.6–53.2% for R2 and R3, respectively. The highest cumulative biogas production (389.67 mL/g·VSin) and methane production (0.56 m3·CH4/kg·VS) was achieved with the R3. In addition, R3 had the shortest reaction delay time (λ), and stabilization of the process was the fastest of all samples. The co-digestion performance index (CPI) was determined to be 1.29, 1.39, and 1.10 for R2, R3, and R4, respectively. The highest value for R3 confirmed the highest synergistic effect. This suggests the possibility of biogas production using sesame oil cake. HIGHLIGHTS Anaerobic co-digestion of fermented sesame oil cake (FSOC) and sewage sludge.; TS and VS removal were increased from 28.5 to 53.2% and 37.6 to 64.9%, respectively.; The highest cumulative biogas and methane production were achieved by 5:5 mixing ratio of FSOC and sewage sludge.; Co-digestion performance index was over 1, confirming that there was a synergistic effect.;

Keywords

• acidogenic fermentation
• anaerobic co-digestion
• biogas
• methane production
• sesame oil cake
• sludge reduction