Effect of C/N ratio in methane productivity and biodegradability during facultative co-digestion of palm oil mill effluent and empty fruit bunch

Abstract The effect of carbon to nitrogen (C/N) ratios towards facultative co-digestion of palm oil mill effluent (POME) and empty fruit bunches (EFB) in terms of methane production and biodegradability of the substrates was experimentally evaluated. The experiment was performed with different EFB and POME loadings which are adjusted to specific C/N ratios. Based on the methane production, gross electricity production from the co-digestion was also calculated and presented. The results showed that cumulative methane production increased from 0.17 L CH 4 (without EFB admixture) to 2.03 L CH 4 in response for the treatment with C/N ratio of 45. After the digestion process, BOD and hemicellulose shows the highest biodegradability rate in POME and EFB, respectively. The maximum estimated gross electricity production of 196 kWh was observed with C/N ratio of 45 (10 L of POME, 3.1 kg of EFB). Conclusively, co-digestion of POME with EFB generates higher methane production, and this relates with the higher degradation of organic substrates.