Abstract
In this research, a small-scale biogas plant using methane fermentation was developed. The electrical energy consumed by the
heater/pump and the outside temperature of the small-scale biogas plant were logged from 1 July 2007 until 31 July 2009. The
thermal efficiency of the small-scale biogas plant was calculated based on the electrical energy consumed by the heater/pump and
the generated gas quantity. The results showed that a total thermal efficiency of 17.5% was obtained in the system. To improve
thermal efficiency in the small-scale biogas plant at the University of Miyazaki, Japan, it is necessary to reduce the power
consumption of the heater/pump during spring and summer.