Environmental Engineering Reference
In-Depth Information
concerning the long-term and cumulative impacts of jatropha seed cake on soils have not been
addressed. In the event that detoxification becomes viable, the use of seed cake as animal feed will
be more beneficial.
14.4 ProductIon oF BIodIesel From JatroPha oIl
The use of straight jatropha seed oil in compression ignition (CI) engines is restricted by some
unfavorable physical properties, particularly its viscosity. Because of higher viscosity, the straight
jatropha oil causes poor fuel atomization, incomplete combustion, and carbon deposition on the
injector and valve seats resulting in serious engine fouling. It has been reported that when direct
injection engines are run with neat vegetable oil as fuel, injectors get choked up after few hours and
lead to poor fuel atomization, less efficient combustion, and dilution of lubricating oil by partially
burnt oil (Ma and Hanna 1999). One possible method to overcome the problem of higher viscosity
is blending of jatropha oil with diesel in the proper proportion, and the other method is transesteri-
fication of oil to produce biodiesel. It is reported that the transesterification process has been proven
worldwide as an effective means of biodiesel production and viscosity reduction of vegetable oils
(Peterson et al. 1992). Biodiesel is now gaining more attention as an alternative fuel for substitut-
ing diesel because it is renewable in nature, produces less emissions, and it can be produced from
locally available oils/fats.
14.4.1 p
rEparation
of
o
il
for
B
iodiESEl
p
roduction
Raw jatropha oil contains wax and gums, such as phospholipids, due to which its viscosity becomes
high. The phospholipids can possibly deactivate the alkaline catalyst in biodiesel production
(Freedman et al. 1984). Also it was reported that 50 ppm phosphorus in oil reduced the yield of
methyl esters by 3-5% (Gerpen 2005). Higher phosphorus content also causes higher sulfate ash
of biodiesel and thus leads to higher particulate emissions, which in turn may influence the perfor-
mance of the catalytic converters (Mittelbach 1996). Therefore, conventional biodiesel processes
often have a degumming operation to remove phospholipids. Jatropha oil has less than 1% free
fatty acids (FFAs), and, taking into consideration the other fuel properties such as pour point and
flash point, it should be degummed and made free from impurity by using toluene or by means of
filtration with 5-µm filter paper before transesterification. This will help in easy completion of the
process and production of good-quality biodiesel. But, if a two-step process (esterification/pretreat-
ment followed by transesterification) is followed for producing biodiesel when the FFA level is
more than 1%, there is no need for degumming because the esterification or pretreatment is more
or less similar to the degumming operation. Phospholipids are hydrophilic and tend to aggregate
when moisture is present, especially in the presence of acidic water. The sedimentation and washing
may remove most of the phospholipids. Lu et al. (2009) studied the effect of phospholipids on the
esterification/pretreatment of jatropha oil and investigated the process by adding phospholipids into
the refined
oil. From this study it was found that phospholipids did not show much influence
on the
final FFA conversion during esterification/pretreatment, as shown in Table 14.6.
The phospholipid
content decreased from the original 0.33% to the final 0.04% (on an average 92% reduction) after
the pretreatment process.
14.4.2 B
iodiESEl
p
roduction
t
Echnology
A number of technologies have been developed to obtain biodiesel from jatropha oil either having
low or high level of FFAs. A brief review of different methods followed for producing biodiesel
from jatropha oil is presented here. Production of biodiesel from any feedstock is largely dependent
on the origin of plant, type of oil extraction process involved, quality of feedstock, FFA contents of
oil, production technology adopted, postproduction parameters, and the desired biodiesel quality
