Biomedical Engineering Reference
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of biodiesel were determined. The acid value of the biodiesel (0.40 mg KOH g −1 ) was
within ASTM (American Society for Testing & Materials) D 6751 specifications for
biodiesel. The values of the other important parameters (i.e., density, ash, flash point,
pour point, calorific value, cetane number, water content, and copper strip corro-
sion) were characterized. It was found that some of the parameters (i.e., density, ash,
flash point, and water content) did not meet the ASTM specifications. The density of
biodiesel was found to be low (801 kg m −3 ), whereas the Indian specifications have
a range of 860 to 900 kg m −3 . The ash content of the biodiesel was 0.21 mass%, in
contrast to the 0.01% specified by Indian standards. Similarly, the flash point also
had a low value of 98°C instead of the minimum value of 120°C. The water content
(<0.02 vol.%) was also slightly higher than specifications (<0.03 vol.%). However,
other parameters (i.e., pour point, calorific value, and cetane number) were found to
be within Indian specifications.
An in-situ transesterification method has been adopted by Velasquez-Orta et  al.
(2012) for the transesterification of microalgae, Chlorella vulgaris . The in situ
transesterification of this microalga was performed by combining the two steps of lipid
extraction and transesterification into a single step. Although the reaction ran to com-
pletion in less time (75 min) using NaOH as the catalyst, a low conversion of FAME
(77.6 ± 2.3 wt%) was obtained that does not meet the specifications of the European
Union (EN 14103), which specifies that the ester content must be at least 96.5% (Sarin
et al., 2009). However, when an acid catalyst (sulfuric acid) was used, a high FAME
yield of 96.8 ± 6.3 wt% was obtained although a longer reaction time (20  h) was
required. Also, a high methanol ratio (600:1) was employed, which will escalate the
production cost of biodiesel. Tran et al. (2012) produced biodiesel from Chlorella vul-
garis (ESP-31) using an enzyme ( Burkholderia lipase) as a heterogeneous catalyst. The
biodiesel was synthesized in  two ways: (1)  transesterification of microalgal oil, and
(2) direct transesterification of the microalgae after disruption of its cells by sonica-
tion. A moderate conversion (72.1%) of the microalgae to biodiesel was obtained with
the first method, whereas a high conversion (97.25%) was obtained using the second
method. The immobilized enzyme was reused for six runs without any significant loss
in catalytic activity. Being catalyzed by an enzyme, the catalyst was found to func-
tion even in the presence of water (>71.39 wt%). However, a higher molar ratio (67.93,
methanol to oil) was needed to achieve an ester conversion of greater than 96 wt% of
oil that will escalate the production cost of the biodiesel.
The fuel properties of the biodiesel synthesized from the microalgal oil derived from
Chlorella protothecoides has been investigated by Chen et al. (2012). The microalgal
oil methyl ester (MOME) with a high ester content (97.7%) demonstrated development
of biodiesel of high fuel quality with a cold filter plugging point of −13°C, which is an
indication that the fuel may be used even under extremely cold conditions. The vis-
cosity of the MOME was 4.43 mm 2 s −1 at 40°C, which is within the specifications for
biodiesel specified by the ASTM. However, the oxidation stability of the fuel was low
(4.5 h), which was due to high amounts of unsaturated fatty acid content in the MOME
(i.e., 90.7 wt%). The induction time as per the Indian and European specifications is at
least 6 h (Sarin et al., 2009). Hence, it had been recommended that the MOME should
use up to 20 vol% blended with mineral diesel. A higher blend of biodiesel in mineral
diesel will require the addition of antioxidants so that the fuel does not get oxidized
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