Enhancement of Fecal Sludge Conversion Into Biogas Using Iron Powder During Anaerobic Digestion Process

Abstract

Anaerobic digestion is often used to stabilized and convert organic wastes into methane and biological fertilizer. However, when applied to fecal sludge, it doesn’t yield good methane due to its high content of nitrogen. Here we have conducted anaerobic digestion of fecal sludge in the presence of iron powder (Fe) as electron donor. Results showed that 4822.7 mL CH4 kg-1 was successfully recovered from fecal sludge in the control. The use of Fe in the anaerobic bio-digester remarkably improved methane yield. Indeed, up to 9933.3 mL CH4 kg-1 wet sludge was recovered when Fe is properly used (1 g Fe for 400 g wet weight), compared to 4822.7 mL kg-1 in the control. The concentration of methane in the produced biogas increased from 58.0% in the control to 72.5% and 77.6% in the presence of iron powder, respectively at the dose rate of 0.5 g Fe and 1 g Fe per 400 g wet sludge. COD removal efficiency was also greatly improved. 65.5% of COD was removed when excreta was properly spiked with Fe (1g Fe) against 42.2% in the control. This corresponds to an increasing rate of 23%. Furthermore, the presence of Fe in the digesters considerably reduced the odor by trapping produced sulphur ion and prevent the formation of H2S responsible for the sickening odor.