Co-digestion of sewage sludge and wheat straw in presence of iron scraps in mesophilic and thermophilic conditions for generating methane

The present study investigated the comparative effect of anaerobic co-digestion of sewage sludge and wheat straw along with waste iron scraps on enhanced methane yield under mesophilic and thermophilic temperature. The co-digestion of sewage sludge with wheat straw enhances the cumulative biogas yield by 6.92 and 5.69 folds under mesophilic and thermophilic conditions respectively. The iron scraps of 250 mg/l as an additive were found to be more effective for methane enhancement as compared to 500 mg/l, under both conditions. The co-digestion of both substrates under mesophilic and thermophilic conditions could enhance 2.67 and 2.37 (approx.) folds methane yield, whereas waste iron scraps supplementation of 250 mg/l further improves it to 3.7 and 4.36 folds (approx.) methane yield respectively. The highest methane yield was observed in the thermophilic digester T-250 followed by M-250, M-500, T-500, M-CTRL, and T-CTRL. Among the tested models, the exponential model was best fitted for the methane production rate. The modified Gompertz model and logistic function model at mesophilic and thermophilic conditions respectively best evaluate the methane yield kinetics.