Synthesis of Biodiesel/Bio-Oil from Microalgae - Biotechnological Applications of Microalgae - page 110

are available in nature, and several of these species may be explored for their
feasibility to be cultured as oleaginous species. The future seems bright for micro-
algae to provide a future alternative to the other fuels.
8.6 CONCLUSION
The oil extracted from microalgae consists of polar lipids and neutral lipids. The
neutral lipids consist of triglycerides, free fatty acids, hydrocarbons, sterols, wax
and sterol esters, and free alcohols. Because only triglycerides and free fatty acids
are saponifiable, they must be separated from the others so as to convert them to
biodiesel by esterification or transesterification. The synthesis of biodiesel/bio-oil
from microalgae involves several steps, including selection of an appropriate species
among a large diversity of species of microalgae (around 300,000). For the production
of bio-oil, a thermochemical method is adopted for the preparation of fuel from
microalgae through pyrolysis, direct combustion, or thermochemical liquefaction,
wherein the organic compound is thermally decomposed at high temperature
in the absence of oxygen. A high yield of bio-oil (97.05%) was obtained through
liquefaction of Dunaliella tertiolecta . Thermochemical catalytic liquefaction has
an advantage over pyrolysis or direct liquefaction, in that a low nitrogen content is
present. A high oxygen content has been observed, which requires deoxygenation of
the bio-oil. Other compounds are also formed along with bio-oil, such as bio-char,
gases, and ash, all of which lower the calorific value of the fuel. The amount of
biodiesel obtained from microalgal oil can be enormous The fatty acid composition
of the feedstock has been found to play a significant role in the composition of the
biodiesel. A trade-off between the oxidation stability and low-temperature proper-
ties of biodiesel has been observed and hence a balance between the two must be
maintained.
ACKNOWLEDGMENTS
Bhaskar Singh is grateful to the Council of Scientific and Industrial Research (CSIR)
New Delhi, India for the award of Research Associateship.
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