Investigation and comparison of bench-scale anaerobic digestion system performance under thermophilic and mesophilic conditions for producing biomethane from solid organic wastes

Document Type : Research Paper


1 Department of Energy Engineering and Economic, Science and Research Branch, Islamic Azad University, Tehran, Iran.

2 Department of Chemistry, Islamshahr Branch, Islamic Azad University, Islamshahr, Tehran, Iran.

3 Department of Engineering and Technology, Astara Branch, Islamic Azad University, Astara, Iran.



The outcomes of every batch of anaerobic digesters vary due to differences in equipment, feed composition, and operating conditions. The performance of a bench-scale anaerobic digestion system was investigated in this study with the goal of biomethane production, considering mesophilic requirements at 37°C and thermophilic conditions at 57°C. Three experiments were carried out under mesophilic and thermophilic conditions. A blend of water and solid organic waste was used in the first experiment. The second test involved a mixture of water, material that had undergone prior digestion, and solid organic waste. The third trial incorporated water, previously digested material, solid organic waste, and cow manure as part of the feed. Based on the result, in the third experiment, over 32 days within mesophilic conditions, the average daily biogas and biomethane production per unit of feed mass was quantified as 1610 and 447.10 ml, respectively. Furthermore, the measurements indicated 62.22% and 99.99% increases compared to similar feed subjected to thermophilic conditions. Moreover, the data displayed growth rates of 8.05%, 96.04%, and a substantial rise of 69.47% and 147.7% compared to the outcomes of the second and third experiments performed under mesophilic conditions. Additionally, it can be included that the digestion period of the third test was 60 days shorter than that of the second and one day less than the first trial when operating under mesophilic conditions. As a result, the most effective method for anaerobic digestion involved blending solid organic waste, previously digested material, cow manure, and water under mesophilic conditions.


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