Enhanced biogas production from fecal sludge by iron metal supplementation: iron enriched fertiliser as a byproduct

Abstract

Iron has strong influence on microbial metabolism and can inhibit activity of microbes in cases of excessive concentrations or of low bioavailability of nutrients. Addition of iron fulfils the deficiency of seven enzymes provided by eight microorganisms. These enzymes are very essential for the microbial activity during anaerobic digestion for enhanced methane production. In this study the anaerobic digestion of fecal sludge was conducted in the presence of iron powder (Fe) as a trace element and the temperature was maintained at mesophilic range i.e. 35°C. For the correction of C: N ratio, co-digestion of fecal sludge and kitchen waste was done. The gas produced was measured by water displacement method. Biogas production from human feces as substrate when supplemented with different concentration of iron powder resulted with improved amount of methane as that from the fecal sludge in the control. Results showed that the production of methane was improved to 53.11 % and 64.74 % in the presence of iron powder, respectively at the dose rate of 0.25 g Fe and 0.5 g Fe per 200 g sludge. The increase in methane yield from Co-digestion was found to be 76.27 % as compared to that of fecal sludge in control.