Evaluation of Jatropha macrocarpa as an oil crop for biodiesel production in arid lands of the Dry Chaco, Argentina

Abstract

Jatropha macrocarpa grows naturally in arid environments of the Dry Chaco, northwestern Argentina, where freezing winters make impossible the cultivation of other species of the genus Jatropha. This article is the first report of J. macrocarpa seed productivity aimed to quantify the reproductive performance and seed oil characteristics at different stages of fruit ripening. In addition, J. macrocarpa is evaluated as a new oil crop for biodiesel. Fruits from natural populations near La Rioja city were hand-harvested during the 2007/8 reproductive season and classified according to 7 fruit sizes, from the smallest fruits (G1) to the largest (G7 or mature). Total seed production averaged 87 ± 8 g plant-1 throughout the growing season. Explosive dehiscence of mature fruits produced 46% of total seed loss. Mature fruits produced individual seeds of 550 ± 7 mg with a medium-to-high seed oil concentration ranging from 36 to 40%, and biomass allocation to seeds was 36% of total fruit biomass. Fruits harvested early, at the G6 stage, were lighter and had a significantly less oil concentration. Main fatty acids in mature seeds included linoleic (50%), oleic (32%), palmitic (8.5%) and stearic (7%) acids. Biodiesel quality parameters indicated only slight differences for cetane number and iodine value with respect to European normative requirements. The acceptable oil content of J. macrocarpa shows promise to be used for biodiesel production. However, the low productivity per plant and the explosive fruit dehiscence need to be corrected substantially by breeding.