The palm oil production process starts after the FFB are harvested and the fruits are separated from the bunches. The first step in processing is at the mill where the CPO is extracted from the fruit. The process of refining palm oil is as follows.
1.Harvesting
As fruit ripen, FFB are harvested using chisels or hooked knives attached to long poles. Each tree must be visited every 10-15 days as bunches ripen throughout the year. Harvesting involves the cutting of the bunch from the tree and allowing it to fall to the ground by gravity. These fruit bunches (each bunch weighing about 25 kg) are then collected, put in containers and transported by trucks to the factories (Poku, 2002). FFB arriving in the factory are weighed accordingly.
2 Threshing (removal of fruits from the bunches)
The FFB consists of fruits embedded in spikelets growing on a main stem. Manual threshing is achieved by cutting the fruit-laden spikelets from the bunch stem with an axe or machete and then separating the fruits from the spikelets by hand. Children and the elderly in the village earn income as casual labourers performing this activity at the factory site. In a mechanised system, a rotating drum or fixed drum equipped with rotary beater bars detach the fruits from the bunches, leaving the spikelets on the stem (Poku, 2002).
3 Sterilisation of bunches
Sterilisation or cooking means the use of high temperature wet-heat treatment of loose fruits. Cooking normally uses hot water while sterilisation uses pressurised steam. Cooking typically destroys oil-splitting enzymes and arrests hydrolysis and autoxidation, weakens the fruit stem and makes it easy to remove the fruits from bunches, helps to solidify proteins in which the oil-bearing cells are microscopically dispersed, weakens the pulp structure, softening it and making it easier to detach the fibrous material and its contents during the digestion process, breaks down gums and resins.
4 Crushing process
In this process, the palm fruits will be passed through shredder and pressing machine to separate oil from fibre and seeds.
5 Digestion of the fruit
Digestion is the process of releasing the palm oil in the fruit through the rupture or breaking down of the oil-bearing cells. The digester commonly used consists of a steam-heated cylindrical vessel fitted with a central rotating shaft carrying a number of beater (stirring) arms. Through the action of the rotating beater arms the fruit is pounded. Pounding, or digesting the fruit at high temperature, helps to reduce the viscosity of the oil, destroys the fruits’ outer covering (exocarp), and completes the disruption of the oil cells already begun in the sterilisation phase (Poku, 2002).
6 Extracting the palm oil
There are two distinct methods of extracting oil from the digested material. One system uses mechanical presses and is called the “dry” method. The other called the “wet” method uses hot water to leach out the oil.
In the “dry” method, the objective of the extraction is to squeeze the oil out of a mixture of oil, moisture, fibre and nuts by applying mechanical pressure on the digested mash. There are a large number of different types of presses but the principle of operation is basically the same. The presses may be designed for batch (small amounts of material operated upon for a time period) or continuous operations (Poku, 2002).
A unique feature of the oil palm is that it produces two types of oil – palm oil from the flesh of the fruit, and palm kernel oil from the seed or kernel. For every 10 tonnes of palm oil, about 1 ton of palm kernel oil is also obtained. Several processing operations are used to produce the finished palm oil that meets the users’ requirements. The first step in processing is at the mill, where CPO is extracted from the fruit (Poku, 2002).
7 Kernel recovery
The residue from the press consists of a mixture of fibres and palm nuts which are then sorted. The sorted fibres are covered and allowed to heat by own internal exothermic reactions for about two or three days. The fibres are then pressed in spindle press to recover a second grade (technical) oil that is used normally in soap-making. The nuts are usually dried and sold to other operators who process them into palm kernel oil.
Large-scale mills use the recovered fibres and nutshells to fire the steam boilers. The superheated steam is then used to drive turbines to generate electricity for the mill. For this reason it makes economic sense to recover the fibres and to shell the palm nuts. In the large-scale kernel recovery process, the nuts contained in the press cake are separated from the fibres in a depericarper. They are then dried and cracked in centrifugal crackers to release the kernels. The kernels are normally separated from the shells using a combination of winnowing and hydrocycloning. The kernels are then dried in silos to a moisture content of about 7% before packing (FAO, 2002).
8 Refining process
After the process of extraction, CPO goes through a refining process to become refined oil. The refined oil will undergo a fat segregation process to get refined palm oil. Finally, the refined palm olein which is a part of fractionation process will be used in related industries (Poku, 2002).
9 Oil storage
Palm oil is stored in large steel tanks at 31 to 40°C to keep it in liquid form during bulk transport. The tank headspace is often flushed with CO2 to prevent oxidation. Higher temperatures are used during filling and draining tanks. Maximum storage time is about 6 months at 31°C (Poku, 2002).
10 Packing process
Having passed through production process and inspection under standard quality control system, all refined oils will be stored in a stock tank ready for delivery. It will be partly transported to modern packaging plants of the company under the sanitary and safety standard before
supplying to customers in the form of refined palm olein from pericarp contained in various types of packaging availability as PET bottle, tin, and soft pack (CPOI, 2008).
11 Delivery
The products will be stringently inspected before loading, and then delivery to customers by using either high standard tanker trucks for mass consumption as industrial usages or different types of truck which suite for each customer size. For export market, the products will be supply as bulk shipment by using vessel with loading capacity either 1,000 tonnes or 2,000 tonnes upon requests (CPOI, 2008).
The entire production processes from harvesting of fruits bunches to oil extraction and from refinery to supply chains involve various resources and technologies at different points and associated with different environmental and social issues.