Environmental Engineering Reference
In-Depth Information
yellow. Maturity is attained 90 days after flowering (Heller 1996). Because all of the fruits do not
mature at the same time, they have to be harvested manually at regular intervals, making this opera-
tion very labor-intensive (Heller 1996; Singh et al. 2006). The time and length of the harvest period
is likely to vary according to the seasonal conditions of the locality. In semiarid regions, the har-
vesting spans over a period of two months, which implies daily or weekly harvests. In permanently
humid situations, weekly harvest is necessary throughout the year. Separation of the seeds from the
husks can be done manually or mechanically (Gour 2006).
Apparently, the yield depends on a range of factors such as water availability, soil conditions,
altitude, sunshine hours, and temperature. No systematic research seems to have been conducted
yet to determine the influence of these factors and their interactions on seed yield. The seed yields
reported for different countries and regions range from 0.4 to over 12 t/ha per year after 5 years of
growth (Jones and Miller 1992). In relatively poor soils, the yields have been reported to be 1 kg per
plant, whereas in lateritic soils the seed yields have been reported as 0.75
-
1.00 kg/plant (Openshaw
2000). Thus, the average yield can be considered as 4.00-6.00 t/ha per year depending on the
agroclimactic zone and agricultural practices (Biswas et al. 2007). Harvesting of the seeds takes
place during the dry season, which is normally a quiet period for agricultural laborers. The ripened
fruits are plucked from the trees manually, and the seeds are sun-dried (three weeks) or oven-dried
(105°C) to reduce the moisture content up to a certain level. The dried pods are collected, and the
seeds are separated manually or mechanically. Seeds are once again dried under sunlight for four
days until the moisture reaches approximately 6-10% before oil extraction. Drying of seeds is
necessary because moist seeds can develop mold and can jam the pressing equipment.
14.3.4 o
il
E
xtraction
m
EthodS
The seeds contain on an average approximately 34% oil. The oil contains a toxic substance, cur-
casin, which is a strong purgative (Chachage 2003). To prepare the kernels for oil extraction, they
should be solar heated for several hours or roasted for 10 min. This process breaks down the cells
containing the oil and eases the oil flow. The heat also liquefies the oil, which improves the extrac-
tion process. The seeds should not be overheated. The oil from jatropha seeds can be extracted by
mechanical extraction using a screw press or chemical extraction (solvent extraction). Figure 14.2
Oil extraction
methods
Chemical
methods
Mechanical
methods
Seed in
hopper
Seed
kernel
Keeping the
solution in beaker
for 24 hours
Manual/
mechanical
grinding
Seed
grinder
Filtering
Pressing grinded
seed
JCL paste mixed
with CCL
4
Shaking for
72 hours
Oil
production
Oil
Cake
Jatropha oil
FIGure 14.2
Flowchart for mechanical and chemical methods of oil extraction.
