Environmental Engineering Reference
In-Depth Information
taBle 14.2
oil extraction efficiency of different methods used for obtaining oil from
Jatropha seed
method
oil yield (%)
Theoretical maximum
44.00
Pressing
Hand press
22.55
Motor press
22.98
Industrial press
27.00
Aqueous oil extraction (AOE)
Basic AOE
16.72
AOE with sonication
29.48
Aqueous enzymatic oil extraction (AEOE)
28.16
AEOE with sonication
32.56
Three-phase partitioning (TPP)
Basic TPP
36.08
Enzyme-assisted three-phase partitioning (EATPP)
40.48
EATPP with sonication
42.68
Source: Bryant C, et al., Jatropha Curcus L.: Biodiesel Solution or All Hype? A Scientific, Economic and Political
Analysis of the Future Energy Crop , 2008. Energy and Energy Policy, available at http://humanities.uchicago.
edu/orgs/institute/bigproblems/Energy/BP-Energy-Jatropha.doc (accessed June 9, 2009)
solvents (mainly supercritical carbon dioxide) or biorenewable solvents such as bioethanol and iso-
propyl alcohol. Although new-generation n -hexane extraction units are far more efficient and cause
far less environmental burdens than the older units, further research on these alternative solvents
needs to be conducted on their commercial viability. Foidl and Mayorga (2007) reported the use of
supercritical isopropanol or carbon dioxide (CO 2 ) in a continuous mechanical oil extraction system,
which left only 0.3% oil (weight basis) in the cake.
Bryant et al. (2008) extracted oil by soxhlet extraction with hexane solvent. There are several
processes for oil extraction that range greatly in cost and efficiency. The oil extraction methods can
be divided into three primary categories: crushing the seeds with a press, aqueous enzymatic oil
extraction, and three-phase partitioning. The oil yield efficiency of different methods used for oil
extraction from jatropha seeds are summarized in Table 14.2.
14.3.4.3 Jatropha oil
The fatty acid compositions and characteristics of the crude jatropha oil are given in Tables 14.3 and
14.4, respectively. It is important to note that the values of the free fatty acids, unsaponifiables, acid
number, and carbon residue show wide variations, although it is a small data set. This indicates that
the oil quality is dependent on the interaction effect of environment and genetics, with the former
having a higher impact than the latter.
The average saturated and unsaturated fatty acids constitute 20.1% and 79.9% of the oil, respec-
tively, which is reflected in the pour and cloud points of the oil. Among the fatty acids present, oleic
and linoleic are the major constituents. The maturity stage of the fruits at the time of collection is
reported to influence the fatty acid composition of the oil (Raina and Gaikwad 1987).
14.3.4.4 Jatropha seed cake
The average crude protein content of the seed cake is 58.1% by weight and has an average gross
energy content of 18.25 MJ/kg (Figure 14.3). On the basis of the extraction efficiency and the aver-
age oil content of the whole seed (34.4% on a mass basis), the seed cake contains 9-12% oil by
weight. This oil content will of course influence the gross energy value of the seed cake. In addition
to high-quality proteins (Figure 14.3), this seed cake contains various toxins and therefore it cannot
be used as fodder (Francis et al. 2005).
 
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