The Effects of Different Pomegranate Wastes, Poultry Manure and Cow Sludge Ratios on Biogas Production

Context: Anaerobic digestion of organic waste is one of the efficient ways to reduce methane emissions in atmosphere and produce pure bio-methane for fuel consumptions. Aims: In this study, the effects of pomegranate wastes, poultry manure, and cow sludge treated with various ratios of respectively 60, 13, and 27% (T1), 89, 0, and 11% (T2), 28, 28, and 44% (T3), and 0, 34, and 66% (T4) were investigated. Evaluation of the pH, total solids (TS), volatile solids (VS), and the ratio of carbon-to-nitrogen (C:N) parameters on the digestion yield in the optimal treatment was another objective of this study. Materials and Methods: The waste concentration (7%) was evaluated based on the TS and over a period of 15 days on the performance of anaerobic digestion. Furthermore, a pretreatment of thermal–chemical processing (boiling in acetic acid and nitric acid) was considered to remove lignin from pomegranate peels. The process of anaerobic digestion was divided into four stages of the setting up, including startup period, the first stage of the stabilization period, the second phase of the stabilization period, and the consolidation phase. Results: The results showed that there was a significant difference in biogas production between the T3 with efficiency of 0.50 L/gr VS and cumulative biogas production value of 5885 ml/day and the T2 with efficiency of 0.60 L/gr VS and cumulative biogas production value of 718 ml/day. The third treatment (T3) was detected as the optimum. In this treatment, the superior performance of anaerobic digestion in the days of third to ninth of the experiment led the highest removing percentage of VS. The C:N ratio remained in the optimal range during the experimental period. Conclusion: The results of this study in a laboratory scale for biogas production appear to be a challenging process so that the substrate composition had a great influence on the performance.