Biogas recovery from anaerobic digestion of starched food refuse: what would be proper conditions

Abstract

The research results showed that biodegradation of starch resulted in the decrease of pH and alkalinity in the anaerobic digester, making it hard to achieve optimal conditions for microorganism growth. It were very difficult to control suitable conditions in both batch anaerobic digestion reactor and one stage semi-continuous system as a result of low biogas recovery efficiency. However, it is possible to get highest CH4 concentration of 56.2% and approximately 50% within 7 days in the two-stage continuous system with sludge retention time (SRT) of 60 days. When SRT reduced to 20 days, maximum CH4 concentration in biogas was only 45.1% and maintained for 2 days. About 73.5 m3 biogas/ton of rice remnant by wet weight, equivalent to 247 m3 biogas/ton of rice remnant dry weight were measured from lab-scale two-stage continuous anaerobic digestion system.