Of all the oil producing crops with the highest yield potential, Jatropha is the only one adapted to depleted soils in tropical semi-arid regions. Of the top six species in the list presented above, Jatropha is the only drought tolerant.
Amazingly, Jatropha achieves a high yield despite being a non-domesticated plant. Given the genetic makeup of this species, we can expect to dramatically improve this yield (kg of oil/ha).
Sunflower plants yield more than twice the amount of oil per unit area than do soybean plants, and yet sunflower oil is still more expensive than soybean oil. That is because the soybean cake meal has a considerable value on the market. Jatropha cake meal is protein rich, making it a highly attractive animal feed. Making Jatropha seeds edible will increase its economic value (two worthy products instead of one).
Jatropha seed toxicity is caused by two toxin families
a) The phorbol esters
Phorbol esters are not destroyed by heat and are deadly. Phorbol ester free Jatropha have been reported in Quintana Roo, Mexico where seeds are roasted and consumed by humans. These are reported as the Jatropha non-toxic ‘variety’ or ‘provenance’.
The nutritional value of Jatropha meal of the non-toxic provenance is high, and potential exists for its incorporation into the diets of poly and monogastrics, fish and possibly humans.
b) Lectins (especially curcin)
Curcin is a Ribosomal Inhibiting Protein. It can be completely denatured and inactivated by a heat treatment at 121°C for 30 minutes. Lectins are not deadly. Feeding with cake meal containing active Curcin will result in a lost of weight.
Lectin-free variety must be developed or cake meal must be heated to 121°C for 30 minutes before being labeled as a feed for cows, goats and pigs
In a study on transmission of toxicity, Sujatha et al (2005, Plant Growth Regulation 47:83–90) show that seed toxicity is a maternal trait in Jatropha.
TABLE Phorbol ester contents in different Jatropha varieties and crosses involving toxic and non-toxic varieties.
Estimation of phorbol esters was done on F1 seeds that were obtained from the parental plants following crossing.
The pollen donor does not affect seed toxicity. Farmers planting non-toxic varieties can safely use or sell the cooked meal as feed, without worrying about toxic plants in nearby fields.
Jatropha oil is reported to be oxidatively unstable
This is true: like soybean oil and sunflower oil, Jatropha oil is oxidatively unstable in its unhydrogenated form. Factors thought to contribute to oil instability include fatty acid content (especially linolenic acid), enzymatic activity occurring in the seed itself and other factors. Oil stability can be increased through purification, hydrogenation, and proper handling of oil. This is however, a major source of concern for seed storage and seed transportation.
There are two ways to get oil with enhanced oxidative stability.
1) Through hydrogenation
Hydrogenation of oil increases the melting point and improves stability of the oil from the effects of oxidation and flavor deterioration by adding hydrogen to unsaturated fatty acid bonds (Erickson et al., 1980. Handbook of Soy Oil Processing and Utilization. American Soybean Association and the American Oil Chemist’s Society. St. Louis, Missouri and Champaign, Illinois).
2) Through selection of high oleic and tocopherol content Jatropha varieties
When using improved high oleic varieties, there is no need for costly industrial hydrogenation. That is why: achieving varieties with high concentration of oleic acid and low concentration of linoleic acid in its seed oil is an important breeding objective.
High γ-tocopherol varieties would also be less prone to oxidation (tocopherols are nature's anti-oxidant: α-tocopherol is vitamin E)
Plant breeding is the most cost-effective way to achieve oxidatively stable Jatropha oil.
• Haiti presently imports over twice as much diesel fuel as gasoline (ethanol is a substitute of gasoline).
Jatropha curcas could be a very profitable crop for developing world farmers. It grows where not much else grows. Jatropha curcas is well adapted to degraded and depleted soils in drought-prone areas.
Without fertilizer and no crop improvement whatsoever, Jatropha already gives better yield than any cereal or food grown in arid regions. An improved non-toxic Jatropha curcas variety could prove to be a major 'cash' crop.
However, with low yielding trees, a 33% oil content (of dry seed weight) and a value of $600/ton (US$) of oil with a toxic seed, you need over 3 tons of seeds in order to extract 1 ton of oil. There is insufficient incentive for farmers to grow it.
If oil content is >40% and the rest of the product is edible protein the seed is worth between $250/ton (price of corn) to $500/ton (price of soybeans) to the farmer. That is between 25 cents to 50 cents per kilo of seeds. It is sustainable (you just increased the farmer's revenue by over 100%). We need to select for high yielding edible Jatropha varieties with high oil content.
Plant breeding is the most cost effective way to achieve an economically profitable Jatropha agriculture.
All of the above are correct. An edible Jatropha variety would not just be an 'energy crop' but would be similar to soybeans - a multipurpose crop providing food, feed and energy.
Jatropha has few requirements with respect to its environment. Because of this, it can grow in areas that are unsuitable for other plants, because they are too dry or too arid, or because they have been left by humans because of soil depletion.
Over the decades, the Haitian peasants have deforested the mountains to make charcoal for cooking. On many of Haiti’s watersheds, there is virtually no vegetation left. These areas are generally not cultivated and not suitable for annual crops. Jatropha grown there would not compete with food crops.
There are about 600,000 ha of such underutilized land in Haiti (a little over one fifth of the total landmass).