*3.1. Palm Oil Mill Effluent*

Palm oil is a digestible and high nutritive oil manufactured in some regions globally, mainly for food and energy production in some countries. The palm oil industry usually produces two main products, crude palm oil and solid palm kernels [70]. Moreover, residual waste of different types is usually produced from palm oil-agro industrial processes [71]. Many waste types, including palm oil mill effluent (POME), are normally obtained from different extraction processes. The treatment of such waste can confer advantageous attributes to MFC processes, resulting in high energy generation [72,73]. POME inoculated with an anaerobic sludge has been treated as reported by some researchers with the aid of a simple two-chambered MFC. This process demonstrated a higher power output (Pdmax) of 45 mW/m<sup>2</sup> to 304 mW/m<sup>2</sup> ; albeit, achieving a considerably lower coulombic efficiency (CE) percentage of 0.8% and 45% COD removal [72].
