Sustainable palm oil processing : Towards zero discharge treatment of POME

Malaysia is the worlds 2nd largest producer and exporter of palm oil, accounting for nearly 49.5% of world production and 64.5% of world exports. In the oil extraction process, palm oil mill effluent (POME) is generated during the procedures of sterilization, stripping, digestion, pressing, classification, purification and vacuum drying. It is estimated that about 1.5 m3 of water are needed to process onetonne of fresh fruit bunches (FFB), and that half of this amount ends up as POME. The raw POME is a thick brown liquid and is characterized by low pH, high biological and chemical oxygen demand, high contents of salt and suspended solids. As a result, thedischarge of POME has the potential of severely polluting the receiving waterways.About 85% of POME treatment is based on the anaerobic/facultative/aerobic pond system practiced by Malaysian palm oil mills. This system is characterized by a long hydraulic retention time (HRT), the need for large areas of land or digesters, and by a large volume of greenhouse gas (GHG) emissions.To reduce HRT, occupied area and GHG emissions associated with POME treatment, and to take advantage of wastes, the "zero discharge" process mainly routed in the sequence: "Pretreatment - Biological processes - Membrane separation" is developed with the following features: .1- AnaEG - an expanded granular sludge bed, a third generation high efficiency anaerobic biological process. It combines the advantages of Up-flow Anaerobic Sludge Blanket (UASB) and Expanded Granular Sludge Blanket (EGSB)technologies and features simplicity and high treatment efficiency. As the key technology, AnaEG fulfills the degradation and conversion of the extremely high content of organic matter in POME. The resulting generated biogas (mainlymethane) is collected.2.BioAX - an advanced and patented aerobic technology with a highly efficient attached growth bio-system, which features an internal circulation design and high treatment efficiency. As this polishing treatment step is complementary to AnaEG, it converts the remaining organic matter into sludge.3. Membrane filter for the BioAX effluent to remove the solids by ultra-filtration and to desalinate and decolorize the water by reverse osmosis (RO), which achieves dual reuses: the filtrate as boiler water, and the concentrate rich with the residual potash for use as fertilizer in the plantation.4. Collected biogas as boiler fuel gas to co-generate needed steam and electricity.5. Excess sludge generated in the biological system as fertilizer in the plantation after drying.6. Waste oil is recovered for the mill.7. Palm shells are reused to produce activated carbon with well-developed porosity and high hardness.The proposed "zero discharge" treatment process is developed based on the Clean Development Mechanism (CDM) and sustainable development strategy, which are not only for environmental protection but also explores the potential market of CDM in Malaysian palm oil industry.