Improving Biogas Production Performance From Pomegranate Waste, Poultry Manure and Cow Dung Sludge Using Thermophilic Anaerobic Digestion: Effect of Total Solids Adjustment

Abstract

Context: Biogas is one of the most important sources of renewable energy and is considered as an environmental friendly energy source. One of the most important parameter influencing the production of biogas is total solids (TS). Aims: In this study, the effects of different total amount of solids, which consisted of 5, 10, 15, 20, 25, and 30% treatments, on the biogas production were examined. The solids were obtained at a thermophilic temperature (55°C) from a mixture of pomegranate rind, cow manure, and sludge in 15 days using one-liter glass bottles. Materials and Methods: The influences of TS, volatile solids (VS), pH, and carbon-to-nitrogen ratio on the biogas production volume from optimized TS treatment were also evaluated. In addition, pomegranate peel was pretreated for lignocellulosic destruction. Results: The results showed that the biogas production increased from 0.273 to 0.736 L/day with an increase in TS from 5 to 25%. The 25% treatment had the highest mean biogas production (i.e., 0.736 L/day). Significant difference was observed between the 25% treatment and all other treatments except the 20% treatment. The regression model showed that the VS was the only parameter that had a significant effect on biogas production. This parameter justified about 74.1% of the biogas production accuracy. Conclusion: Anaerobic digestion is an appropriate technology to achieve the organic fraction of solid wastes. Due to higher biogas production, dry anaerobic digestion is of more importance than wet and semi-dry anaerobic digestion.