11 - Jatropha Curcas: A Solution for a Sustainable Energy Supply?

Summary

ABSTRACT

Jatropha is a plant that has yet to be domesticated but that has great potential to be a sustainable source of energy. Its productivity however, is highly unpredictable and variable. Better knowledge of its biodiversity, the continuous breeding for better varieties, and the production and distribution of uniform and superior planting materials would all greatly increase the productivity of Jatropha in plantation. Addressing the issue of toxicity and ecological concerns would also lead to better acceptance of Jatropha.

INTRODUCTION

Commonly named the physic nut, Barbados nut, or purging nut, and as a member of the Euphorbiaceae family, Jatropha curcas is a shrub with a smooth, grey bark that grows up to six metres tall. It has large, pale green and shallow-lobed leaves that are arranged alternately. Its bark exudes copious amounts of watery sap when cut. Native to tropical America, it is cultivated widely in tropical countries throughout the world, mainly as a living fence and hedge plant (Jongschaap et al. 2007).

Jatropha grows in well drained and aerated soils and is well adapted to marginal soils with low nutrient content. Its water requirement is low and it withstands long periods of drought by shedding most of its leaves to reduce transpiration loss. It can also grow in lower temperatures and withstand light frosts. Jatropha has yellow-green flowers, generally with many more male than female flowers on the same plant. These flowers are pollinated by insects, especially honey bees. Seeds mature in about three months after flowering. Jatropha can produce seeds from the first year of planting onwards, for as long as fifty years in humid conditions (Heller 1996). Each fruit contains two to four large, black, oily seeds. The seeds contain up to 37 per cent of non-edible oil with the following four most abundant fatty acid components: palmitic (C16:0), stearic (C18:0), oleic (C18:1), and linoleic acids (C18:2). Jatropha seeds contain considerably more unsaturated fatty acids (oleic acid and linoleic acid) than saturated fatty acids (palmitic acid and stearic acid).