Aims:This research aims to investigate the potential of biohythane (biohydrogen and biomethane) production from palm oil mill effluent (POME) in a two-stage anaerobic digestion (AD) system.Methodology and results:A two-stage AD system was configured with a thermophilic dark fermenter (TDF) for biohydrogen (H2) production and a thermophilic anaerobic contact digester (TACD) for biomethane (CH4) production. To adjust pH 5.5 for dark fermentation, the settled sludge was recirculated from TACD to TDF. The hydraulic retention time (HRT) applied in TDF and TACD was 3.75 and 6.25 day, respectively.Conclusion, significance and impact of study:The sludge recirculation from TACD was able to adjust the pH in TDF to the optimum value of 5.5. The total COD and TSSdegradation were 63.12 and 77.94 %, respectively. The H2production in TDF was 1.54 L H2/L POME and the CH4production in TACD was 19.87 L CH4/L POME. The H2and CH4yielded 0.085 L/g CODremovedand 0.339 L/g CODremoved, respectively, with total energy recovery equivalent to 661.02 MJ/m3POME. Only 2.28 % of this energy was contributed by H2and the remaining was dominated by CH4.