The astonishing resources of the physic nut tree

In Cape Verde, an interesting project has been set up on behalf of the Ministry of Rural Development, at Loura, a village of 110 families, 25 km from the capital. The aim of the project is to create an agro-industrial unit to produce and process physic nuts. The physic nut tree, also known as jatropha and the oil tree, is a shrub that had already been cultivated in Benin, Madagascar, and the Cape Verde islands during the Second World War for the manufacture of soap and the extraction of fuel oil from the seeds. But these activities were abandoned in the 1950s with the boom in the oil industry. On an area of about 100 hectares, 100 000 shrubs have been planted, and experts responsible for the initiative hope that by 1990 they will be producing around 175 tons of physic nuts. A semi-industrial process will be used to extract 50 000 litres of oil a year. Artisanal methods obtain only 35 500 litres and cost twice as much. Jatrophas are an important source of energy, and the major objective of the project is, of course, to produce fuel, sufficient to run the semi-industrial plant and to make possible the introduction of experimental stoves into homes and thus save fuelwood. Physic nut oil will also replace lamp oil in the home, and residues from the agro-industrial complex at Loura will be used to run generators. This raw material should also yield 4.5 tons of soap a year at an expected retail cost of FF 90/kg, substantially less than imported soap, which costs FF 115/kg.

The promoters of the project hope to create a new economic activity for Loura with positive social and political effects, but they also expect jatropha plantations to be an important ecological achievement. The project is part of a reforestation programme to prevent erosion. Planted in hedges, the shrubs can function as windbreaks to protect annual crops.

It is hoped that this initiative will be an example for other villages of Africa, Asia, and Central America where the shrub grows.

The jatropha, indigenous to the arid regions of Brazil, is an oleaginous shrub (Jatropha curcas) and a member of the family Euphorbiaceae. It was introduced to the Cape Verde islands in the sixteenth century by Portuguese navigators, but it has also been cultivated in India for several generations. It grows both spontaneously and under cultivation in village plots, both in dry tropical countries and in humid equatorial regions. Although it prefers cool soils, it also grows vigorously - with almost no care - on arid escarpments, and can adapt to long periods without rain.

The jatropha is a vigorous softwood plant, 2-6 metres tall. It flowers twice a year; its fruit, indehiscent on the tree (i.e., it does not open spontaneously when it ripens), is a small dark-brown spherical capsule that contains the seeds. Propagation takes place in the rainy season by cuttings or by seeds. The plant begins to bear fruit at three or four years and remains productive for 30 to 50 years.

The numerous properties of jatropha seem to warrant expanding cultivation. Indeed, the shrub is used in many tropical countries as a windbreak, as a barrier against erosion, to make enclosures, and as fuelwood. The fact that it adapts to ecologically deprived areas means that it can easily be integrated in reforestation programmes. According to Georges Martin, an authority on the species, it could be extremely useful in fighting desert encroachment in the Sahel. Jatropha also has therapeutic properties; it is used in Indian vedic traditional medicine and is renowned as a cathartic. All its various parts find medical uses in western and southern Africa, Burma, Brazil, Japan, Cape Verde, and Thailand.

A decoction of its roots can be used as a remedy for digestion problems. Its leaves are used for skin troubles (particularly scabies and dartres); and, in the past, Senegalese women used them to protect their hands when applying henna to their hair.

Because the sap is a coagulant, it is used to dress wounds. And finally, the curcas oil extracted from the seeds contains a toxic principle which, though it cannot be used for human consumption, is known for its purgative and diuretic effects. In addition to its medical properties, jatropha is apparently also a molluscicide, as proven by an experiment performed in Senegal by the Parasitological Department of the National Stockbreeding and Veterinary Research laboratory of Dakar. According to G. Vassiliades, author of the report on this study, the leaves, stems, seeds and kernels have the properties required to combat aquatic molluscs, such as Lymnaea natalensis or Bulinus guernei, carriers of human and animal disease.

But jatropha has an even more important characteristic. Its oil, which has always been used to make soap, varnish, and dyes, and as lamp oil, is a very efficient fuel.

In 1985, the National Botanical Research Institute of Lucknow in India published the conclusions of its research: curcas oil mainly consists of glycerides, and of stearic, palmitic, myristic, oleic and linoeic acids; its molecular structure is comparable to that of colza oil; it has absolute viscosity, determined at a temperature of 35°C and 100°C, and very weak acidity. With all these properties, it can be used as a lubricant and converted to replacement fuel in diesel engines. The numerous properties of this plant definitely imply that it could be used to give new impetus to economic activity in certain developing countries. But, as stressed by G. Martin and A. Mayeux, engineers at the Institute for Research on Oils and Oilseeds in Paris, in an article on energy oil crops, it is essential to continue to set up and implement research programmes in order to create a real jatropha development policy.

Anne Le Nir