1.2.4 Downstream Processing of Third Generation
of Biofuels
Microalgae have gained substantial attention recently as an enticing source for the
industrial development of unconventional biofuels, predominantly biodiesel and
aeronautics energies. Moreover, to its capability for advanced biofuels and
bioproducts as an alternative biomass, the gathering of diluted crops of algae from
large crop volumes desirable for production of biofuels and bioproducts is a considerable barrier to the algal biofuel’s economic feasibility (Kim et al. 2013). Although
sedimentation along with centrifugation are now surmounted to capacities that will
require straight application to the production of algal biofuel, their economics for
biofuel production are not optimistic. Despite the numerous advantages associated
with biofuel production using microalgae, the commercial feasibility of the
microalgae-based biofuels industry is nearly equivalent with that of either the
petroleum industry or the bioethanol industry. One of the key motives for the great
algal biofuels production expense is the absence of an extremely inexpensive
method which incorporates the several phases involved with harvesting, extracting,
and transforming biomass to biodiesel. As per Kim et al. (2013), for most downstream production, a secondary or thickening phase is necessary to increase the
concentration of solids. For this secondary concentration stage, the final solid
content required varies and 50% solids is the range mostly for downstream practices
that will be able to withstand substantial moisture range.
1.3 Harvesting Method
1.3.1 Settling/Sedimentation/Gravity Sedimentation
Among all the methods to extract algal cultures, easiest way is naturally settling of
cells due to gravitational force. It has been applied to various algal strains so far and
is generally applicable in high bacterial load wastewater treatment which includes
nutrient rates to support clumping and settling. The density of cell and the radius of
algal cell influence the system flow rate and its usefulness, in turn improved by
lamella separators and sedimentation tanks (Chen et al. 2011). Settling is also done
for the introduction of flocculant/coagulants. While this is indeed the slowest
possible segregation alternative, it is still the one with the lowest energy demand.
1.3.2 Centrifugation
Most microalgae can be retrieved by centrifugal force from dilute suspension.
Centrifugation offers both enhanced harvesting performance and improved
18
A. Shrivastava et al.
of Biofuels
Microalgae have gained substantial attention recently as an enticing source for the
industrial development of unconventional biofuels, predominantly biodiesel and
aeronautics energies. Moreover, to its capability for advanced biofuels and
bioproducts as an alternative biomass, the gathering of diluted crops of algae from
large crop volumes desirable for production of biofuels and bioproducts is a considerable barrier to the algal biofuel’s economic feasibility (Kim et al. 2013). Although
sedimentation along with centrifugation are now surmounted to capacities that will
require straight application to the production of algal biofuel, their economics for
biofuel production are not optimistic. Despite the numerous advantages associated
with biofuel production using microalgae, the commercial feasibility of the
microalgae-based biofuels industry is nearly equivalent with that of either the
petroleum industry or the bioethanol industry. One of the key motives for the great
algal biofuels production expense is the absence of an extremely inexpensive
method which incorporates the several phases involved with harvesting, extracting,
and transforming biomass to biodiesel. As per Kim et al. (2013), for most downstream production, a secondary or thickening phase is necessary to increase the
concentration of solids. For this secondary concentration stage, the final solid
content required varies and 50% solids is the range mostly for downstream practices
that will be able to withstand substantial moisture range.
1.3 Harvesting Method
1.3.1 Settling/Sedimentation/Gravity Sedimentation
Among all the methods to extract algal cultures, easiest way is naturally settling of
cells due to gravitational force. It has been applied to various algal strains so far and
is generally applicable in high bacterial load wastewater treatment which includes
nutrient rates to support clumping and settling. The density of cell and the radius of
algal cell influence the system flow rate and its usefulness, in turn improved by
lamella separators and sedimentation tanks (Chen et al. 2011). Settling is also done
for the introduction of flocculant/coagulants. While this is indeed the slowest
possible segregation alternative, it is still the one with the lowest energy demand.
1.3.2 Centrifugation
Most microalgae can be retrieved by centrifugal force from dilute suspension.
Centrifugation offers both enhanced harvesting performance and improved
18
A. Shrivastava et al.