The palm oil milling process consists of various operational stages.

In the first stage, the Fresh Fruit Bunch (FFB) is sterilised to ease the separation of fruitlets and EFB. Most of the palm oil mills are using horizontal cylindrical vessels with three bar steams for the sterilisation process. Over the past ten years, continuous steriliser and tilting steriliser are being introduced with the aim to improve milling efficiency by lowering labour and maintenance cost.

However, the new type of steriliser cost more capital compared to the conventional horizontal steriliser. The oil yield can be improved by using various patterns of the sterilisation process.

Following sterilisation, the fruitlets and EFB are threshed via rotating or fixed drum. The separated fruitlets (palm nuts and mesocarp fibres) are passed to the digestion process.

In a steam-jacket drum with high pressure, fruitlets are digested the resulting release of oil-bearing cells which then pass through a pressing process to extract the oil from mesocarp fibres in the fruitlets. The double screw press is quite popular in the milling industry.

During the pressing process, both solid and liquid products are produced. The solid product usually come out in the form of a mixture of mesocarp fibres and palm nuts. Fibres and palm nuts can be separated through inclined rotary separator or depericarper. The liquid products include a mixture of water (45–55%) and palm oil (35–45%).

Besides these, there are also some fibrous materials produced. The palm oil is purified and converted to CPO by using centrifugal and drying operations. For better oil quality, the purified CPO must be stored between 32 and 40 °C.