Performance evaluation based on long-term operation results of biogas plant for livestock manure management

In this study, we report the long term operation results of analyses of characteristics of the Rakuno Gakuen University Biogas generation plant (BGP), which has been in operation since March 2000. We evaluated using data for the 11-year period between April 2000 (FY2000), when BGP was built, and March 2011 (FY2010). The average biogas production per unit showed substantial fluctuations during this period, increasing from 20 m³ during the trial operation period in FY2000 to 30–40 m³ in FY2001–FY2006, and then decreasing to 15–25 m³ in FY2007–FY2010. The optimal methane fermentation facility temperature for steady methane gas production was approximately 40 °C. In FY2007, this BGP experienced its first localized functionality decline in energy use, including methane fermentation and power generation facilities. This resulted from changes in the substrate characteristics, inputs, and methane fermentation facility temperature, indicating that operations need to accommodate such changes in the long term.