studied biogas production from manure in a
thermophilic serial digestor with 15 days HRT and obtained a
biogas production rate of 14.9 L/L feed. Similar work was conducted
by Boe and Angelidaki (28) and their results were 17.3 L/L feed.
Dareioti et al. (29) determined the biogas production rate of 1.82 L/
L$d per reactor volume in a mesophilic two stage system at 19 days
HRT. Due to five different OLRs between 1.9 and 4.67 g VS/L$d, results
under this study changed between 10.3 and 23.2 L/L feed
which are appropriate and even higher than other studies.