Indonesia is the largest palm plantation that reaches 32 million tonnes palm oil production per year with 84 million tones Palm Oil Mill Effluent (POME) as liquid waste. POME contains many organic substances. The quality of POME for its utilization is generally measured in COD which has range 30000 -100.000 ppm. Microbial convertion for biogas especially for bio-H2 enrichment, the active sludge was pretreated physically to suppress methanogenesis microbes. H2 Biogas production was conducted at

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... H 5-6. Additional 10% phosphate buffer was done in the beginning only. The production of H2 biogas was influenced by hydrostatic pressure in closed batch system. Inoculumsmedium ratio also influenced the H2 biogas productivity, reached 0.7 ml / ml POME with more than 50% H2. Scaling up anaerobic in 2.5 L working volume bioreactor, H2 biogas productivity reached 0.86 ml / ml POME by 10% inoculums because of no hydrostatic pressure. In bio-reactor, H2-CO2 in H2 biogas was affected by the amount of active sludge. In the beginning of H2 biogas, H2 reached 80%. However, at subsequence process, fed batch, with retention time 2.5 day and 3 days H2 biogas production, the active sludge was accumulated and caused the decreasing H2, finally only 46% at the 3 rd day. The consortium tended to produce more CO2 as the result of primary metabolite rather than H2. Raising inoculums to level 15% improved productivity only in the beginning but H2 content was getting less, only 59%. Additional feeding would cause more accumulation sludge and more decreasing H2 content to 31% on the 3 rd day. Thus, the ratio of active sludge and substrate availability must be controlled to gain optimum H2. Limited substrate will cause the direction of bio-conversion more in CO2 rather than H2.