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Jatropha curcas: an overview

March 2nd, 2010 No comments

Consider the food or energy crops priority, it is important to choose the suitable energy crops converting to biofuels. Corn has become the very emblem of plenty, with rich golden cobs of corn overspilling from some of the most effectively farmed arable lands on the earth. Jatropha curcas, on the other hand, is an unprepossessing and indeed toxic plant, better suited to scrubland and hedges. Yet in the world of biofuels, ugly-duckling jatropha has the potential to be, if not a hero, and a harbinger of better things to come [1].

Jatropha curcas L. is a drought-resistant shrub or tree belonging to the genus Euphorbiaceae, which is cultivated in Central and South America, South-east Asia, India and Africa [2]. J. curcas is easy to establish, grows relatively quickly and is hardy, being drought tolerant. It is not browsed, for its leaves and stems are toxic to animals, but after treatment, the seeds or seed cake could be used as an animal feed. J. curcas meals contain high true protein, high energy and low fiber [3]. Various parts of the plant are of medicinal value, its bark contains tannin, the lowers attract bees and thus the plant has a honey production potential; its wood and fruit can be used for numerous purposes including fuel. Of particular importance, the fruit of J. curcas contain viscous oil that can be used for soap making, in the cosmetics industry and as a diesel or kerosene substitute or extender. This latter use may be of importance when examining practical substitutes for fossil fuels to counter greenhouse gas accumulation. Also, like all trees, it fixes atmospheric carbon, stores it in wood and assists in the build up of soil carbon [4].

There are many positive claims on J. curcas, include that the crop: reclaims marginal soil, grows well under saline conditions, is drought tolerant and may have low water use (or high water use efficiency), has low nutrient requirements, is an energy crop, grows seeds with high oil contents, provides high oil yields, provides oil with high quality, requires low labor inputs, does not compete with food production, is tolerant or resistant to pests and diseases. These claims have been proved in traditional and low scale production. However, related to high oil yield production, is not backed up by scientific finding so far, especially in large scale production [5]. J. curcas is still a wild plant which exhibits a lot of variability in yield, oil content and oil quality. Given the booming interest which J. curcas receives nowadays, there is an urgent need for better data to guide investments. Preliminary results on the lifecycle energy balance and global warming potential of biodiesel from J. curcas are favorable, but it is important to note that the GHG balance is tightly linked to the type of land use which is removed and to the intensity of the cultivation [6]. Due to this unproved claims, various ministerial meetings that might have given the national mission on biofuel the seal of approval have been postponed in favour of higher-priority issues. Despite this, several states like India and China have enthusiastically hopped aboard the J. curcas express, providing free plants to small-scale farmers, encouraging private investment in J. curcas plantations and setting up biodiesel processing plants [7].

However, Jatropha biodiesel had comparable fuel properties with those of diesel and conforming to the latest standards for biodiesel (see Table 1.4) [8]. The choice of using J. curcas bio-diesel (i.e. methyl esters) or the J. curcas oil depends on the goal of the use (e.g. electricity or transport) and the available infrastructure. Studies show that transesterified J. curcas oil achieves better results than the use of pure J. curcas oil, straight or in a blend, in unadjusted diesel engines. Changing engine parameters shows considerable improvement of both the performance and the emission of diesel engines operating on neat J. curcas oil. More trials on the use of straight J. curcas oil in different diesel engine setups should be tested and investigated. Accurate measuring and reporting on emissions contributing to global warming, acidification, eutrophification, photochemical oxidant formation and stratospheric ozone depletion is very relevant. The long-term durability of the engines using bio-diesel as fuel requires further study as well [9].

Table 1.4. Fuel properties of jatropha oil, jatropha biodiesel and diesel [8]

Property Unit Jatropha oil Jatropha biodiesel Diesel Biodiesel standards
ASTM D 6751-02 DIN EN 14214
Density at 15 oC kgm-3 940 880 850 860-900
Viscosity at 15 oC mm2s-1 24.5 4.80 2.60 1.9-6.0 3.5-5.0
Flash point oC 225 135 68 > 130 > 120
Pour point oC 4 2 -20
Water content % 1.4 0.025 0.02 < 0.03 < 0.05
Ash content % 0.8 0.012 0.01 < 0.02 < 0.02
Carbon residue % 1.0 0.20 0.17 < 0.30
Acid value mgKOHg-1 28.0 0.40 < 0.80 < 0.50
Calorific value MJ kg-1 38.65 39.23 42

References:

  1. Nature Editorial, Kill king corn, Nature, 2007, 449, 637.
  2. G. M. Gübitz, M. Mittelbach, and M. Trabi, Exploitation of tropical oil seed plant Jatropha curca L., Bioresources Technology, 1999, 67, 73-82.
  3. H. P. S. Makkar, A. O. Aderibigbe, and K. Becker, Comparative evaluation of non-toxic and toxic varieties of Jatropha curcas for chemical composition, digestibility, protein degradability and toxic factors, Food Chemistry, 1998, 62 (2), 207-215.
  4. K. Openshaw, A review of Jatropha curcas: an oil plant of unfulfilled promise, Biomass and Bioenergy, 2000, 19, 1-15.
  5. R. E. E. Jongschaap, W. J. Corre, P. S. Bindraban and W. A. Bradenburg, Claims and facts on Jatropha curcas L.: Global Jatropha curcas evaluation, breeding and propagation programme, Plant Research International B.V., Wageningen, 2007, 44 pp.
  6. W. M. J. Achten, E. Mathijs, L. Verchot, V. P. Singh, R. Aerts, and B. Muys, Jatropha biodisesel fueling sustainability?, Biofuels, Bioprod. Bioref., 2007, 1, 283-291.
  7. D. Fairless, The little shrub that could – maybe, Nature, 2007, 449, 652-655.
  8. A. K. Tiwari, A. Kumar, and H. Raheman, Biodiesel production from jatropha oil (Jatropha curcas) with high free fatty acids: An optimized process, Biomass and Bioenergy, 2007, 31, 569-575.
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