costs of production. The selection of harvesting technology is crucial to economic
production of algal biomass (Zhou et al. 2014). The processes involved include
flocculation, filtration, flotation, centrifugal sedimentation, also extraction and purification. Well-known methods of the oil extraction are: (1) Expeller/Press, (2) solvent
extraction, and (3) supercritical fluid extraction. The most popular chemical solvent
for extraction is hexane. Supercritical fluids are selective, thus providing the high
purity and product concentration. This can extract almost 100% of the oils all by
itself (Elegbedea et al. 2017).
1.3
Process of Algal Biomass Into Biofuels
1.3.1 Cultivation of Algae
Cultivation of microalgae can be conducted in batch, semi-batch, and continuous
systems. Batch culture consists of a single inoculation of cells in container of media
over several days of growth period until the cell density reaches a maximum/
desirable level ready to be transferred to larger culture volumes to continue growth
before reaching the stationary phase. The semi-batch system allows a portion of the
culture to be harvested and replenished with fresh medium. In a continuous system,
Fig. 1.1 The classification of biofuels (adapted from Dragone et al. 2010)
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N. Maheshwari et al.