ARBOK-POMEGAS: Vacuum Degassing and Graphene-Sorbent Concentration of Methane from Palm Oil Mill Effluent Ponds

Palm oil mills discharge 2.5-3 t of effluent (POME) per ton of oil into open ponds, where anaerobic decay releases methane, a greenhouse gas 28 times stronger than CO2, directly into the atmosphere. The gas is not collected because pond gas is wet and carries hydrogen sulfide, so conventional upgrading requires drying and desulfurization stages that remove the economic case. ARBOK-POMEGAS is a site-level assembly in which (i) vacuum degassing of the effluent removes up to 94% of dissolved methane and 88% of hydrogen sulfide, (ii) a rapid-cycle adsorption unit on hydrophobic, sulfur-inert thermally expanded graphite (TEGA) with vacuum regeneration at 15-20 kPa concentrates the methane to about 90% CH4 without a drying or desulfurization stage, and (iii) the gas is used first for the mill's own electricity, with the surplus compressed into cylinders for nearby households. The degassed effluent is treated by vacuum evaporation (AZOW), returning more than 90% of its volume as process water and yielding an organo-mineral fertilizer and ammonium sulfate. For a mill of 10,000 t of oil per year the balance gives 1,400-3,800 MWh of captured gas per year against a mill demand of 2,000-2,600 MWh of gas for its 700-900 MWh of electricity. The estimated effect is up to USD 1.4 million per year per mill, with about 10,000 t of CO2 avoided.