Outlook on biorefinery potential of palm oil mill effluent for resource recovery

Global uptrends in palm oil industry have been observed while a vast amount of waste, particularly palm oil mill effluent (POME) which is a type of wastewater that can cause severe environmental pollution has been discharged. This has caused remarkable challenges for palm oil mills to obey the regulations of standard discharge limits, resulting in development of several bioremediation methods and bioreactors, which are presented in this paper. For further utilisation of POME, researches have been carried out to develop value added products from POME and to make POME as energy resources. Indeed, POME with high chemical and biochemical oxygen demand as well as mineral content is suitable and useful raw material. Simultaneous wastewater treatment and production of bioenergy and bioproducts will make palm oil industry more clean, sustainable and environmentally friendly. Hence, this review comprehensively summarizes the production of renewable energies (methane, biohydrogen, syngas, biodiesel and biocrude oil) and high value products (microalgae, yeasts, enzymes and bioplastics) from the POME wastewater, critically analysing their current developments and future prospect. Nevertheless, there are still research needs in order to improve the biorefinery and bioremediation of POME.