High organic load in POME
Palm-oil mill effluent contains dissolved and suspended organic matter. Conventional pond treatment requires large areas and can cause substantial methane emissions.
Palm oil mill waste treatment and bioenergy
POME biogas and biomethane from palm oil mill waste
POME biogas and biomethane engineering concepts convert palm oil mill effluent, decanter sludge, flotation sludge and selected EFB fractions through anaerobic digestion into process energy and fertiliser products while reducing wastewater loads and methane emissions.
Initial challenge
Unused energy, high wastewater loads and nutrient losses
Different residue fractions
The aqueous POME fraction, oil- and solids-rich flotation sludge and decanter sludge require different but coordinated biological treatment routes.
Inhibitors in the process loop
When liquid digestates and biofiltrates are recycled, ammonium and sulphur compounds can accumulate and impair fermentation.
Loss of plant nutrients
Nitrogen, sulphur, phosphorus and potassium are not selectively recovered in uncontrolled treatment and are unavailable to plantations as valuable fertiliser products.
Process concept
POME treatment and anaerobic digestion in separate process lines
Physical pretreatment
POME is separated, for example by dissolved-air flotation and oil/solids removal, into a low-solids liquid fraction and an oil- or solids-rich fraction.
UASB digestion of the liquid fraction
The pretreated low-solids POME fraction is anaerobically treated in a UASB reactor system and used for biogas production.
Suspension preparation and conventional anaerobic digestion
Flotation sludge, decanter sludge and other fine residues are suspended with treated process water and recovered in a separate digestion line. Upstream hydrolysis can further improve degradation.
Biological gas desulphurisation
The raw biogases from both lines are desulphurised together. This produces a sulphurous process liquid that is used internally to recover nitrogen and sulphur.
Inhibitor removal and fertiliser recovery
Biofiltrates and UASB digestates are relieved of excess ammonium and sulphur compounds. The products are an aqueous ammonium sulphate solution and a solid nutrient-rich fertiliser fraction.
Internal process-water recycling
Liquids after inhibitor removal are recycled as suspension medium. This reduces fresh-water demand and the residual wastewater volume requiring treatment.
Suitable material streams
Palm-oil mill residues as an integrated feedstock system
POME
Palm-oil mill effluent containing dissolved and suspended organic matter.
Decanter sludge
Fine, oil- and nutrient-rich residue from mechanical crude-oil clarification.
Flotation sludge
Oil- and suspended-solids-rich fraction separated during POME pretreatment.
Optional additional residues
After suitable size reduction and preparation, fine fractions from EFB, mesocarp fibres or palm-kernel cake can also be integrated into an extended concept.
Client benefits
More value from existing residues
Process energy from own residues
The biogas can be used for electricity, heat and steam or upgraded to biomethane, replacing fossil fuels.
Reduced pond area and wastewater load
Removing organic matter and nutrients reduces BOD and COD loads as well as the demands on downstream pond systems.
Fertilisers for the plantation
Ammonium sulphate solution and solid NPKS-rich fractions return nitrogen, sulphur, phosphorus and potassium to the operational nutrient cycle.
Reduced greenhouse-gas emissions
Closed digestion prevents uncontrolled methane emissions and additionally replaces fossil energy and mineral fertilisers.
More stable biological processes
Separating the material fractions and removing inhibitors from recycled liquids reduces process risks and allows each digestion line to be specifically designed.
Additional revenue potential
In addition to avoided energy costs, revenue may be generated from electricity, biomethane, fertiliser products and, where recognised, emission reductions.
Engineering scope
POME biogas plant and biomethane engineering
Domogalla Engineering develops site-specific concepts for palm oil mills that combine wastewater treatment, anaerobic digestion, methane capture, gas utilisation and nutrient recovery.
POME biogas feasibility study
Material-flow, COD and energy balances define the recoverable biogas potential, reactor concept, required pretreatment and integration with existing ponds and mill utilities.
Palm oil mill effluent treatment
Separation of aqueous and solids-rich fractions allows POME wastewater treatment to be matched with UASB digestion, conventional digesters or a coordinated combination of both.
Decanter sludge and EFB integration
Decanter sludge, flotation sludge and selected prepared EFB fractions can be assessed for co-digestion, hydrolysis and integration into a stable palm oil waste-to-energy system.
Biogas upgrading to biomethane
Depending on gas demand and local infrastructure, captured POME biogas can supply electricity, steam and heat or be upgraded to biomethane for vehicle fuel, industrial use or grid injection.
Relevant experience: Sangatta palm oil residue biogas project in Indonesia.
Technical background
The presented process solution is based on the published international patent application WO 2017/121422 A1. A specific plant concept requires a site-specific analysis of POME and residue quantities, material qualities, existing pond and energy systems, fertiliser use and permitting conditions.
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