Environmental Engineering Reference
In-Depth Information
shows the procedure of mechanical and chemical methods followed for extraction of oil from jat-
ropha seeds.
14.3.4.1 mechanical extraction using a screw Press
In this method, seeds are pressed in a manual ram press or in a powered screw press to expel the oil,
leaving seed cake. For mechanical extraction of oil from the seeds, the extraction rate of the ram
press is low (60-65% of the available oil) as compared with the powered screw press (75-80% of
the available oil). The leftover seed cake still contains some oil. One liter of oil can be expelled from
approximately 3 kg of seeds (Henning 2004). The seeds can be subjected to a number of extrac-
tions by passing through the expeller. Up to three passes is common practice. Pretreatment of the
seeds (e.g., cooking) increases the oil yield of screw pressing up to 89% after a single pass and 91%
after two passes (Beerens 2007). The theoretical maximal amount of oil in a jatropha seed has been
reported to be approximately 48.6% (Kandpal and Madan 1995).
14.3.4.2 chemical extraction
The reaction temperature, reaction pH, time requirement, and oil yield of different chemical extrac-
tion methods tested on jatropha seeds are summarized in Table 14.1. The
n
-hexane method is the
most common chemical extraction method. It results in the highest oil yield, but it also takes the
most time. In aqueous enzymatic oil extraction, the use of alkaline protease gave the best results
(Winkler et al. 1997; Bryant et al. 2008). Furthermore, it is shown that the ultrasonication pretreat-
ment is a useful step in aqueous oil extraction. Adriaans (2006) opined that solvent extraction is eco-
nomical only for the large-scale production of more than 50 t biodiesel per day. It was reported that
the conventional
n
-hexane solvent extraction is hazardous to the environment (generation of waste-
water, higher specific energy consumption, and higher emissions of volatile organic compounds)
and human health (working with hazardous and inflammable chemicals). Using aqueous enzymatic
oil extraction greatly reduces these problems (Adriaans 2006), as does the use of supercritical
taBle 14.1
effect of reaction Parameters on different chemical extraction methods on oil
yields from Jatropha seed
reaction
temperature (
°c)
time
consumption (h)
extraction method
reaction ph
oil yield (%)
n
-Hexane oil extraction (soxhelt
apparatus) first acetone,
second
n
-hexane
-
-
24
95-99
-
-
48
-
AOE
-
-
2
38
50
9
6
38
AOE with 10 min of
ultrasonication as pretreatment
50
9
6
67
AEOE (hemicellulase or
cellulase) AEOE (alkaline
protease)
60
4.5
2
73
60
7
2
86
50
9
6
64
AEOE (alkaline protease) with
5 min of ultrasonication as
pretreatment
50
9
6
74
Three-phase partitioning
25
9
2
97
AOE, aqueous oil extraction; AEOE, aqueous enzymatic oil extraction.
Source:
Achten, W.M.J., et al.
Biomass Bioenergy,
32, 1063-1084, 2008.
