Physicochemical Changes in Windrow Co-Composting Process of Oil Palm Mesocarp Fiber and Palm Oil Mill Effluent Anaerobic Sludge

The effect of hydraulic retention time and volatile fatty acids produced during fermentation were investigated on biohydrogen production from palm oil mill effluent in a 50 L bioreactor. The fermentation was done in three different hydraulic retention times; HRT 5, HRT 3 and HRT 2 days. Hydraulic retention time and volatile fatty acids concentration showed a vital role in response to the biohydrogen concentration, biohydrogen rate and biohydrogen yield. The maximum biohydrogen concentration was obtained at HRT 2 days with 30% hydrogen content in biogas. The biohydrogen yield and rate were 1054 NmL/L-POME and 44 NmL/h/L-POME, respectively. The lowest biohydrogen yield and rate were observed at HRT 5 days with 557 NmL/L-POME and 5 NmL/h/LPOME, respectively. Meanwhile, the accumulation of propionic acid concentration up to 7 g/L was suggested as a factor that reduced the biohydrogen production