|Small Scale Processing of Oilfruits and Oilseeds (GTZ, 1989, 100 p.)|
|1. Oil Plants and their Potential Use|
|1.2 The major oil plants|
The sheanut or karite, Vitellaria paradoxa (syn.: Butyrospermum parkii), is a wild-growing tree in the countries south of the Sahel zone. The tree is relatively small, growing to a height of some 12 metres, having a thick trunk and a number of spreading branches which form a dense crown. It bears fruit after 10 to 15 years, reaching full bearing capacity at 20 to 25 years.
From Senegal to Sudan, the fruit, which requires 4 to 6 months to mature, is locally of substantial economic importance in particular for rural women who collect the nuts and process them to a butter-like edible substance. Average yield per tree is 15 to 20 kg of fresh fruit, with one third of the trees being productive each year. 50 kg of fresh nuts give 20 kg dry kernels which yield about 4 kg of shea butter.
The kernel of the nut contains 32 to 54 % fat. In international trade, shea butter serves as a cheaper substitute for cocoa butter and is in high demand when prices for the latter are up. It is also valuable for the cosmetic industry. With an estimated total production (collected nuts) of 500000 tons per year, Nigeria, Ghana, Ivory Coast and to a lesser extent, other countries in West Africa, are reported to export altogether about 30 000 tons.
Actual production and even export figures, however, are difficult to verify. In Mali, for example, production of kernels in the season 1985/86 is estimated to be 44000 tons, of which 10200 tons were officially exported. Inofficially, an estimated additional 16000 tons have left the country for unknown destinations.
Cotton, Gossypium spp., is basically a textile plant, which is mainly cultivated for its hair or lint (9.5 to 20 mm long) on the stem and leaves. Apart from the commercial value of the fibre, however, the seeds contain about 25 % oil thus making cotton the third most important oil crop. Of additional value is the protein-rich (40 %) oilseed cake, which gives a good protein supplement for cattle. The oilcake, however, can contain free gossypol, a pigment sometimes found in cottonseed. In this case, the use of the cake is limited to feeding to non-ruminants in small quantities.
World production of the seeds has exceeded 30 million tons in recent years, and of cottonseed oil between 3 and 4 million tons (see Tables I and 2). Major producers of cottonseeds are China, USSR and the USA. Although the plant originates from semi-arid zones in Africa, the continent as a whole (mainly Egypt and Sudan) only contributes 7 % to world production. World trade in cottonseed oil is dominated by the USA and Brazil. Due to the relatively low oil content of the seeds, solvent extraction is generally applied as a larger industrial operation; small-scale equipment does not appear to provide economic extraction.
Linseed, Linum usitatissimum L., is also mainly cultivated for its fibre, but is in multiple use as a spice and an oil yielding plant. World production in linseeds has considerably decreased over the last two decades and currently stands at about 2.5 million tons annually. The major producers are Canada and Argentina; production in Africa is negligible. Linseed oil is used mainly for technical purposes (paints) and faces heavy competition from other vegetable oils and in particular synthetic products. The market for the oil is more or less taken by Argentina (71 %) and the Federal Republic of Germany (17 %). Small-scale extraction is done in India.
Maize (Corn in American diction), Zeamays L., is basically a starch plant, but the oil content of the germ is also used on a commercial scale. The plant originates from Central and South America from where it began to spread to almost all parts of the world. Today, the USA is the largest producer, both American sub-continents together still contributing the majority (60 %) to the total world production. Maize oil is rather a minor byproduct of the maize starch manufacturing industry and is extracted on an industrial scale. World trade in maize oil amounts to about 300 000 tons annually, largest exporters being Europe and the USA. Africa accounts for net imports of some 10 000 tons a year.
Safflower, Carthamus tinctorius, originates from the eastern Mediterranean and the Persian Gulf and was first cultivated for the orange dye obtained from the florets. The seeds of modern varieties, however, contain 36 % to 48 % oil with good qualities for human consumption; a fact which now constitutes the main purpose for the cultivation of the plant whose seeds are suitable for small-scale processing.
The plant is a highly branched, herbeceous annual, varying in height from 30 to 150 cm and generally has yellow flowers. The fruit resembles a small, slightly rectangular sunflower seed, but with a thicker, more fibrous hull. It gives best yields (but with I ton/ha still low) in semiarid climates. Due to its fairly good drought and salt resistance, safflower is suitable for areas where other oil seeds are difficult to grow.
World production of safflower seed increased sharply in the 1960's but has since remained static at just below I million tons a year, with India accounting for more than half of the total. Safflower is still considered a typical small-holder crop and is mostly processed and consumed locally; for large plantations, as those in Mexico until recently, other oil seeds, particularly hybrid sunflower, appear to be more profitable.
Castor, Ricinus communis, is indigenous to eastern Africa, most likely originating in Ethiopia, but has a contemporary world-wide distribution in the warmer regions. Originally a tree with heights up to 10 m, most mechanically cultivated varieties today are short-lived dwarf annuals and only 60 to 120 cm high. Castor plants also grow wild in many countries and production could be substantially increased if incentives were sufficient. This is particularly so in eastern Africa, from the southern Sudan to southern Tanzania, where there are extensive areas with wild species.
Castor seeds (or beans") almost exclusively originate from the developing countries, the major producers being China and Argentina. Although Africa does not play a major role in official statistics of world production (3 %), castor seeds might well be of greater economic significance in the local context. In world trade of castor oil, Brazil and India clearly dominate the supply side with a combined market share of over 90 %; largest importing region is Western Europe.
A large proportion of castor seeds on local markets in less developed regions is obtained from wild or semi-cultivated plants. At least in Africa, systematic cultivation of pure stands of castor by peasant farmers is the exception. More often castor is interplanted with other crops, sown along borders of fields, planted in areas unsuitable for other crops or merely protected when found growing naturally. In a cultivated stage, yields per ha are a mere 0.5 to I ton. The seeds, however, have a high oil content of 42 % to 56 % and are suited for small-scale processing methods. The oil is used for a variety of technical purposes.
Other oil yielding plants suitable for small-scale processing, which, for reasons of space cannot be dealt with in detail, include:
- Physic Nut (Purgier), Jatropha curcas, the oil of which is
mostly used for soap and might be economically used as a fuel on the Cape Verde
- Niger Seed, Guizotia abyssinica, which is produced in India and Ethiopia and gives a good edible oil,
- Babassu, Orbignya oliefera, originating from Brazil with nuts containing 2to 8 kernels with 60 % oil similar to coconut oil,
- Cohune, Orbignya cohune, growing in Central America, the nuts containing a kernel with 60 % oil comparable to coconut oil,
- Neem, Melia azadirachta L. (A-adirachta indica), growing in Africa, SE-Asia and India, with seeds containing 45 % oil, which is mainly used for soap and medical purposes,
- a large number of wild growing oil yielding plants of local importance.