The palm oil industry has continued to grow in Malaysia and worldwide. It provides job opportunities to at least 3 million people along its beneficiation chain and contributed RM37.7 billion to Malaysia�s Gross Domestic Product (GDP) in 2018. At only 10 oil yield from a palm tree, this growth leads to an excess of palm oil by-products in Malaysia. From mill operations alone, palm oil mill effluent (POME) and empty fruit bunch (EFB) accounted for up to 80 (wet basis) of the total mill residues. Malaysia produces approximately 53 million cubic meters of POME annually and typical treatment processes using open ponds are inadequate to cope with this amount efficiently. Anaerobic digestion (AD) and aerobic composting (AC) are potential alternative treatment processes suitable for POME treatment while simultaneously producing value-added products such as biogas and compost fertilizer. To further promote sustainability, other by-products can be used as additives in AD and AC to improve the overall process by formulating the ideal feedstock material which helps to provide optimum conditions for the process. However, technical knowledge is required to sustain bacterial activity in both processes otherwise the fermentation processes are easily disrupted resulting in low methane yield and unhealthy compost. This chapter describes the palm oil industry overview from global and Malaysian perspectives. It outlines the processing approach in the mill, type of products and by-products generated in each processing stage and the treatment strategies used. Two commonly used treatment processes; AD and AC are described in detail with the potential of using co-digestion additives to improve the processes. © 2021, The Author(s), under exclusive license to Springer Nature Switzerland AG.