Botanical Description and Varieties
The oilpalm, Elaeis guineensis, is a robust, stately palm, unlike the delicate graceful coconut palm. When fully grown it can reach 20 meters on a single stout stem, normally 50 cm in diameter and large pinnate fronds.
It is native of freshwater riverine and swamplands of the Guinea Coast of West Africa, where it long formed the principal natural product of the country, occurring wild or in a semi-cultivated state over a wide area.
The palm is monoecious, (bearing both male and female flowers on the same tree but in separate bunches), and the flowers are partly wind pollinated. However, recent work has shown that the palm weevil Elaeidobius kamerunicus, from West Africa, plays a key role in the pollination of palms in their natural environment. This weevil was not present in the vast areas of palms planted in South East Asia over the last 20 years. Its introduction there recently, in place of assisted pollination, has very greatly improved yields, particularly of kernels, and saved very considerable sums of money. After pollination, the fruit matures and ripens in about five months.
The fruit is produced in bunches of 1000-2000 nuts/heads with several surrounding the trunk at the base of each frond. The nut is reddish-orange in colour and 3-4 cm in length when fully matured, and consist of an outer fibrous pulp layer, a middle hard black seed coat and an inner nut that also renders oil. One head can weigh between 10-30 kg, so when it is cut from the tree, it falls to the ground with a shaking thud. The heads are handled carefully, because they have long thorns that stick through the tightly packed nuts.
There are three major groups: Dura, Piscifera and Tenera, the latter being the most productive.
Dura has a large seed coat and inner kernel, but only a thin outer pulp from which most of the oil is extracted.
The original four palms, planted for ornamental purposes in the Botanical Garden in Bogor, Indonesia, in the last century, from which most palms of the extensive oilpalms plantations in South East Asia are derived, had a very high percentage of mesocarp to fruit, up to 65%, and a large thick kernel with no ring of fibres round it. The oil-to-bunch ratio is low. Material derived from these palms is known as Deli Dura, and is used as the female parent in breeding programmes.
Piscifera has no seed coat and a very small kernel but a very thick outer layer of pulp. However this variety is usually a very low producer and the oil is often of lesser quality. The majority of piscifera bunches abort at a early stage of development. It is however used as a male parent with dura to produce tenera.
Tenera (D x P) combines the favourable characteristics of both parents, with comparatively thin shells, and a high ratio of mesocarp to fruit. It has been widely used in commercial plantings throughout South East Asia, Africa and Surinam.
In addition there are many cultivars within those three groups.
More recently, work has been undertaken on Elaeis oleifera, a palm native to Central and South America. While it possesses certain desirable characteristics such as short stem growth, polyunsaturated oil and probably resistance to certain diseases, its oil yield is low. Although steps to cross it with piscifera progeny show some promise, a further disadvantage is that its flowers are not attracted to the pollinating weevil Elaeidobus kamerunicus.
In the last 10 years considerable advances have been made in the development of tissue techniques for Oilpalms; palms produced in this way are now becoming available for commercial plantings.
A decline in yield, combined with the height of the palms, which makes harvesting difficult, dictates replanting after 20-24 years.
Cultivation, Propagation and Planting. The palm thrives in a hot humid climate, with a well-distributed rainfall in excess of 1525 mm per year and prefers low lying, alluvial soil. It is normally grown in coastal or low lying inland areas below 650 m.
The annual production of palm oil has expanded, primarily over the last 20 years, to over 4 million m.t. Of this, more than half is produced in Malaysia, and less than a quarter in Indonesia, the next largest producer. The palm oil production in Central America and Surinam is declining due to political instability.
Fresh seeds may germinate in 4-5 months after planting. For commercial purposes, they are normally subjected to heat treatment to speed up germination. Thereafter they are transferred to polybags for eight to twelve months, and then planted out in the field, generally on a 9m equilateral triangular spacing, to give 140 palms per hectare.
Under good conditions palms begin to bear fruit after 18 months to two years in the field, reaching peak yields after about 8 years. Yields of up to 30 m.t. of fresh fruit bunches (f.f.b.) per hectare per year have been recorded on coastal soils. Figures of 20-24 m.t of f.f.b. per hectare are however more usual.
Harvesting and Oil Extraction. Ideally, harvesting rounds should be carried out at 7-10 days interval. Harvesters use long aluminium or bamboo poles with knives on them. Bunches and loose fruit detached during harvesting are collected manually and taken by buffalo, push carts, tractors or lorries to the mill for processing as quickly as possible. The fresh fruit bunches can weigh up to 70 kg, bear numerous oval fruitlets. Fresh fruit bunches will give 17-22% crude palm oil, increasing as the palm reach maturity.
Once in the factory, fruit bunches are subjected to four stages of semi-continuous processing involving sterilization, bunch stripping, oil extraction, clarification and purification. It is important that f.f.b. be sterilized as soon as possible after harvesting to terminate the build-up of free fatty acids in the fruit. This build-up commences immediately after harvesting, and is hastened by bruising. Crude palm oil is generally sold on the basis of a maximum of 5% free fatty acids.
The outer covering of the fruitlet (pericarp) yields crude oil in its unrefined state. This is the oil traditionally used in West Africa for cooking. The hard kernel shell within the pericarp is split to produce the kernel and this is also crushed for kernel oil.
Fibre from the pericarp from which the oil has been extracted is mixed with kernel shell to fire the furnaces producing the power to run the factory. Stripped bunches are either burnt to produce an ash with a high potash content, which is returned to the field as a fertilizer, or used untreated as mulch for young palms.
After the oil has been further refined, the soft portion is used in various types of cooking oil and synthetic shortenings, while the hard portion is used for soap and detergents.
Sources: Tropical Planting And Gardening by H.F.Macmillan and Zaire Native Fruits, by R.M.Danforth and P.D.Noren.
DATE: July 1994
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