The hydrogen production was improved by a C/N ratio of 53.4 used in C2 and
C4. The average hydrogen production rate in C4 was 7.6 NL H2/LCMd, which indicates a high hydrogen
potential compare to substrates such as POME and wheat starch. In this condition, the biogas composition
was 0.1%, 50.6% and 39.0% of methane, carbon dioxide and hydrogen, respectively.