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454 Refining Biomass Residues for Sustainable Energy and Bioproducts

20.3.2 Microalgae and macroalgae

The production of biofuel using microalgae includes selection of a particular
microalgae cultivation of that specific species, harvesting followed by pretreatment
methods that include acid transesterification, product separation, and anaerobic
digestion (Assacute et al., 2018). Macroalgae are commonly known as seaweeds, it
is generally found in subtidal and intertidal regions of the sea. It includes selection,
cultivation, and harvesting of a particular macroalgae, in continuation with extrac-
tion of biodiesel along with the production of enzymes with alcoholic fermentation
and anaerobic digestion. When compared to microalgae, macroalgae seems to be
more complex. Same feedstock has been converted into different value-added pro-
ducts (Assacute et al., 2018). The production of biodiesel using microalgae and
macroalgae is depicted in Figs. 20.1 and 20.2, respectively.

20.3.2.1 Chlorella
The green microalgae, Chlorella has a high protein content and it can be used for
human consumption, whereas it can accumulate large amounts of lipids when
grown under stress condition. Due to this ability, it can be used for the production
of biofuels. The main disadvantage of the cultivation of Chlorella includes high
cost (Guccione et al., 2014). It is cultivated under photoautotrophic conditions
predominantly in open ponds (Ramaraj et al., 2016). The largest autotrophic pro-
duction of algae was started from the year 2000 in a system of 500 km in glass

Figure 20.1 Production of biofuel using microalgae.