Process optimization and modeling of anaerobic digestion of cow manure for enhanced biogas yield in a mixed plug-flow reactor using response surface methodology

Majid Rasouli^{⃰ 1}, Yahya Ajabshirchi¹, Seyyed Mohammad Mousavi², Mohsen Nosrati², Soheila Yaghmaei³    

¹Department of Biosystem Engineering, Faculty of Agricultural Engineering, University of Tabriz, Tabriz, Iran ²Biotechnology Group, Chemical Engineering Department, Tarbiat Modares University, Tehran, Iran ³Department of Chemical and Petroleum Engineering, Sharif University of Technology, Tehran, Iran

DOI : http://dx.doi.org/10.13005/bbra/1909

ABSTRACT: Pilot scale experiments were performed on the digestion of dairy cow manure in a semi-continuous process using a mixed plug flow reactor (MPFR) to determine the effects of organic loading rate (OLR), temperature and mixing levels on production biogas and methane yield. Response surface methodology (RSM) was applied for the design and analysis of experiments with the optimization of OLR, temperature and mixing level during the biogas production process. Experiments were designed as per the central composite design technique. Four cubic mathematical models were derived for prediction of the responses. The optimization study has been carried out to identify the highest yields achievable when the factors temperature and mixing are minimized. In process optimization, maximum values of biogas production and methane yield were achieved as 0.570 m³/m³ day and 0.113 m³/kgVS added, respectively, with an OLR of 3.15 kgVS/m³ day, temperature of 37.66 °C and mixing regime of 20.32 rpm for 10 min per 2 hours.

KEYWORDS: Anaerobic digestion; Bio-gas; Mixed plug flow reactor (MPFR); Response surface methodology (RSM); Optimization

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