Investigation of the effect of slurry mixing ratio and temperature on biogas production from cattle dung in a field-scale anaerobic digestion plant

Abstract

The substrate/water ratio and temperature effects on biogas production rate were investigated using cattle dung as substrate. Initially, laboratory-scale experiments were performed considering three substrate/water ratios of 1:1.5, 1:1 and 1.5:1 in both controlled (35°C) and uncontrolled environments for 55 days. The substrate/water ratio of 1:1 achieved the highest specific cumulative biogas yield of 247.75 and 311.14 ml/gVS for uncontrolled and controlled digesters, respectively, and consequently, considered for field-scale experiments that were performed in 1 m³ capacity anaerobic digestion plant at three different phases. An average volume of 6.26 m³/week of biogas was generated during the summer season (first phase) against the loading of 50.00 ± 1.50 kg cattle dung slurry/day. Subsequently, in the third phase of the experiment, the integration of the solar-assisted heating system improved the cumulative biogas yield by an average of 9.93% over the digester without solar-assisted heating (second phase) during the winter season. The correlation coefficient (R²) value was also found to be approximately 0.99, revealing that predicted results perfectly fit experimental values. The present study confirms that adopting a passive solar-assisted heating system for a field-scale anaerobic digestion plant is a novel approach towards enhancing the biogas yield.

KEYWORDS:

• Anaerobic digestion
• substrate/water ratio
• temperature
• solar-assisted heating system
• kinetic analysis

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This study is part of a project (grant number: ECR/2016/001830) funded by the Science and Engineering Research Board (SERB) to the School of Energy Science and Engineering, Indian Institute of Technology Guwahati, India. The financial assistance provided by SERB is gratefully appreciated.