Continuously fed anaerobic digesters for biogas production from agro-industrial lignocellulosic wastes: Experimental and modeling studies

Abstract

In this study, recovery of methane-rich biogas recovery from lignocellulosic waste materials were assessed experimentally and theoretically in continuously fed anaerobic digesters under mesophilic and thermophilic conditions. Potato peels (PPs) and sunflower hulls (SSHs) were selected as abundantly available waste materials utilized in this study individually as substrates inoculated with chicken dung. The results showed that average recovered biomethane-rich biogas from PPs was 60% higher than from SSHs at steady state conditions achieved after approximately 20 days of continuous operation. Microbial growth in the biodigesters was assessed by Monod model, Halden model, and Chen- Hashimoto model in terms of methane yield and substrate utilization rate. First order kinetic model was adopted to describe the kinetic of anaerobic digestion process in the continuously operated digesters. The results predicted by Monod model significantly fitted the experimental results with correlation coefficients (R2) > 0.93. However, the results predicted by Chen- Hashimoto model exhibited less significancy with the measured results for the SSHs, whereas, those obtained by Halden model were insignificant for both substrates. The outcomes of first order kinetic model for continuously operated anaerobic digesters showed that this model produced perfect goodness of fit with the experimental data.