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To identify the optimal methanol volume, wet microalgae biomass (100 mg dry weight

equivalent) of Chlorella pyrenoidosa were reacted with 6 mL n-hexane, 0.5 M sulfuric acid
and different volumes of methanol ( 2, 4, 6, 8 and 10mL) at 90°C for 120 min. The results

showed that the biodiesel yield was increased from 30.47% to 92.34% with the methanol
volume increasing from 2 mL to 6mL (Figure 2). The maximum biodiesel yield of 92.34%

was obtained at 6 mL of methanol. Further, increasing methanol volume to 8 mL, the
biodiesel yield was decreased to 88.69%. Cao et al., 2013 has suggested that during

transesterification, more methanol was needed to shift the reversible reaction forward (as

observed) perhaps due to the increased contact area between methanol and lipid, resulting in
higher yield of FAME. In the present research, we found that the volume of methanol

necessary for maximal direct conversion of algal lipids to biodiesel was higher than that

reported by Wahlen et al., 2008 and Ehimen et al., 2010. It was stated that the optimum
molar ratio of methanol to oil for the transesterification of the microalgae Chlorella sp. in

situ is 315:1, while a higher alcohol content does not show a positive effect. Velasquez-Orta
and Harvey (2012) found that the highest ester yield (77.6%) in the

transesterification of microalgae Chlorella vulgaris oil was obtained at a molar ratio of
alcohol to oil of 600:1. Given that methanol is a poor solvent for oil and therefore limits the

mass transfer of oil to alcohol, it is suggested to use additional solvents for the in situ

transesterification process to increase the oil extraction efficiency from biomass.

CONCLUSIONS

From these results, it can be concluded that the moisture content of the raw material has a
significant influence on the efficiency of biodiesel synthesis and the economic indicators of

the in situ process since the removal of moisture requires additional energy costs. This effect

is particularly true when microalgae biomass is used in biodiesel synthesis, with drying costs
account for up to 70% of the biodiesel production cost.

REFERENCES

Wahlen, B. D. Willis, R. M. and L. C. Seefeldt, 2011. Biodiesel production by simultaneous

extraction and conversion of total lipids from microalgae, cyanobacteria, and wild
mixed- cultures. Bioresource Technology, 102(3), 2724–2730.

Li, P., Miao, X. R. Li and Zhong, J. 2011. In situ biodiesel production from fast-growing

and high oil content Chlorella pyrenoidosa in rice straw hydrolysate. Journal of

Biomedicine and Biotechnology, vol. 2, Article ID 141207, 8 pages,

695