Dark fermentation for hydrogen production using POME: Insights on scale-up, pressure control, energy recovery and key process variables

In 2024, global palm oil production reached 78 million tons, generating approximately 240 million tons of palm oil mill effluent (POME). Although non-toxic, POME has high organic load and polluting potential, but also serves as a promising raw material for biohydrogen production through dark fermentation. Experimental results showed that thermal pretreatment of anaerobic sludge was essential to enhance H 2 yields, while sterilization of POME was unnecessary, offering potential cost reductions. The best H 2 conditions evaluated (40 g COD /L, 35 °C, with pressure relief) yielded 36 N-mL/L.g COD with productivity of 32 N-mL/L.h and a specific production of 1423 ± 130 N-mL/L. Scale-up from 300 mL to 7000 mL maintained comparable performance, suggesting the process feasibility. Furthermore, subsequent anaerobic digestion of the effluent produced methane (2918 N-mL/L and 57% COD reduction in 35 days), supporting a two-stage valorization strategy. These findings highlight POME potential for sustainable bioenergy production and industrial application.