Comparison of process stability in methane generation from palm oil mill effluent using dairy manure as inoculum

- This study investigated methane production from dairy manure as inoculum.
- Addition of dairy manure improved both the start-up time and rate of biogas production.
- Biogas production was achieved at ambient temperature.

The potential of methane production in a continuously stirred tank reactor (CSTR) was investigated using dairy manure as inoculum at pH 6.8 and 37 °C temperature in this study. Two identical anaerobic bioreactors namely CSTR1 and CSTR2 filled with palm oil mill effluent (POME) as a carbon source were used. CSTR1 was not added with the inoculum, while CSTR2 was added with dairy manure as inoculum. Both the reactors were allowed to run for 5 days (d) in batch condition at hydraulic retention time (HRT) 10 d. The CSTR2produced 0.85 L/d gas yield and 59% methane content compared to 0.39 L/d gas yield and 20% produced in CSTR1, respectively. A better chemical oxygen demand (COD) reduction percentage of 48% was found in CSTR2 compared to CSTR1 with 33%. The investigation showed that dairy manure as inoculum has a marked influence on the start-up period and the biogas production rate.