The digestion temperature has an influence on the
ultimate methane yield, as well as the methane content.
In the mesophilic temperature range, 25–35 C, the higher
the temperature, the better the methane yield. However,
the yield did not linearly increase with increasing temperature.
The yields at 30 and 35 C were similar, but were quite
high compared to that at 25 C, by more than 13–17%.
However, this result does not mean the higher temperature
the more optimal, due to the larger energy requirement at
higher digesting temperatures. Therefore, careful consideration
of the net energy balance between the increased heating
energy demands and improved additional methane
production at higher operating temperatures must be
simultaneously taken into account when deciding the economical
digesting temperature. Furthermore, this net
energy balance is inevitably dependent upon the VS content
of the feed, as methane comes from the degradation
of VS. Temperature shocks led to a reduction in the biogas
production rate compared to that of the control, but recovere ered rapidly. Once recovered, no clear difference in the biogas
yield was observed between the control and the
temperature shock reactor. This result indicates that,
although methanogens are quite sensitive to temperature
they have considerable ability to adapt to temperature
changes.