Components and Uses
Jatropha plants generate various useful products
Cultivation of Jatropha curcas plants on wastelands results in the productive use of such land and helps eventually to reclaim the land for agricultural production.
Jatropha fruits yield a number of fractions:
All these fractions find uses that give them commercial value:
- The husks can be put back into the soil as mulch.
- From the seeds, the oil can be extracted which is the raw material for high quality biodiesel.
- The seed cake left over after the extraction of the oil is a natural fertilizer with pesticidal properties. It can also be used as fuel, replacing e. g. coal. Seed cake has an energy content of approx. 20 MJ/kg which is only about 15% less than best quality coal.
The high market potential of the various fractions increases the attractiveness of Jatropha cultivation, especially for small farmers.
The fruits can be plucked when they start to become yellow. Mostly, in small farms, they are collected after they dry on the tree. The fruit sheath can be removed manually or using small scale deshellers. Once removed, the fruit sheath can be put into the soil as mulch. They can also be used as fuel as they have an energy content of over 14 MJ/kg.
Currently, Jatropha oil is extracted mostly by using screw presses, where dried Jatropha seeds are crushed whole. The seeds (including shells) have an oil content of more than 35% by weight. Using a screw press the normal extraction percentage of oil is 25-30%. This means that the seed cake comprises 70-75% of the seeds. This seed cake can be used either as a fertiliser or as a fuel.
On an average, the seed cake contains 3-4.5% N, 0.65-1.2% P2O5, 0.8-1.4% K2O and 0.2-0.35% S and is hence an excellent organic fertiliser. The phorbol esters present in the seed cake act as a biological pesticide particularly against soil nematodes, slugs and snails that are harmful to plants. However, they do not accumulate in the soil as they are broken down by soil microbes. This pesticidal effect increases the value of the seed cake as an organic fertiliser especially for biological farming. The average proximate composition, gross energy and phorbolester content of the jatropha seed cake is shown below.
Average chemical composition, gross energy content and phorbol ester content of jatropha seed press-cake (dry matter basis)
|Gross energy MJ/kg||21|
|Phorbol ester mg/g||0.7|
With a gross energy content of 20 MJ/kg, the seed cake also has potential as a domestic fuel.