8.2.1.2.2 Tubular Photobioreactors (TPBRs)
TPBRs are mainly used for outdoor cultivation processes as they have high surfaceto-volume ratio exposed to sunlight and high photosynthetic efficacy (Brennan and
Owende 2010; Rastogi et al. 2018). Further, they provide an excellent temperature
control and have lower risks of photoinhibition and contamination, thereby allowing
monoalgal culture cultivation (Rastogi et al. 2018). These TPBRs further have a
drawback of possible fouling accompanied by algal growth along the walls (Bahadar
and Khan 2013), possibility of high dissolved oxygen levels, cell damage by shear
stress of pumping, and large space requirement for setup (Rastogi et al. 2018).
8.2.1.2.3 Flat Plate Photobioreactors(FPBRs)
The algal culture proceeds across the flat plate in the form of a thin and dense layer,
thereby resulting in absorption of radiation within the initial few millimeters of
thickness (Richmond et al. 2003; Brennan and Owende 2010). Contrary to the
tubular versions, the flat plate PBRs involve lower dissolved oxygen accumulation
and lower chances of contamination (Rastogi et al. 2018), it provides higher photosynthetic efficiencies, and are thus widely used for algal mass cultivation (Richmond
2000; Brennan and Owende 2010). Despite various advantages, its limitations
include difficulties in scale-up, low surface-to-volume ratios, poor control over
temperature, hydrodynamic stress, and wall growth (Rastogi et al. 2018).
8.2.1.2.4 Penthouse-Roof Photobioreactors (PRPBRs)
PRPBRs are mostly used in regions of temperate climatic conditions and consist of
both indoor and outdoor units. The various parameters of cultivation such as flow
rate, temperature, and oxygen levels can be easily maintained, and collectors are
used to focus and direct the light (Bahadar and Khan 2013).
8.2.1.2.5 Plastic Bag Photobioreactors (PBPBRs)
PBPBRs are attractive and are used commercially due to their lower production
costs. However, the disadvantages are photo-limitation, insufficient mixing,
possibility of leakage, shorter life span, etc. Further, the major hurdle in the
use of these systems is the disposal of large amounts of plastic bags (Wang et al.
2012; Huang et al. 2017).
8.2.1.2.6 Bubble Column Photobioreactors (BCPBRs)
BCPBRs are cylindrical vessels with a height that is more than twice the diameter, where gas mixture is bubbled through the sparger and an external light source
is used to determine its photosynthetic efficiency (Singh and Sharma 2012;
Janssen et al. 2002).
8.2.1.2.7 Helical-Type Photobioreactors (HTPBRs)
HTPBRs are comprised of coiled tubes that are flexible and transparent and have a
small diameter. The degassing unit is either separate or attached, and the culture is
made to traverse through the long tube toward the degassing unit by a centrifugal
pump. Better photosynthetic efficiency can be obtained when carbon dioxide
8 Algal Biomass: Potential Renewable Feedstock for Biofuels Production – Part I
209
TPBRs are mainly used for outdoor cultivation processes as they have high surfaceto-volume ratio exposed to sunlight and high photosynthetic efficacy (Brennan and
Owende 2010; Rastogi et al. 2018). Further, they provide an excellent temperature
control and have lower risks of photoinhibition and contamination, thereby allowing
monoalgal culture cultivation (Rastogi et al. 2018). These TPBRs further have a
drawback of possible fouling accompanied by algal growth along the walls (Bahadar
and Khan 2013), possibility of high dissolved oxygen levels, cell damage by shear
stress of pumping, and large space requirement for setup (Rastogi et al. 2018).
8.2.1.2.3 Flat Plate Photobioreactors(FPBRs)
The algal culture proceeds across the flat plate in the form of a thin and dense layer,
thereby resulting in absorption of radiation within the initial few millimeters of
thickness (Richmond et al. 2003; Brennan and Owende 2010). Contrary to the
tubular versions, the flat plate PBRs involve lower dissolved oxygen accumulation
and lower chances of contamination (Rastogi et al. 2018), it provides higher photosynthetic efficiencies, and are thus widely used for algal mass cultivation (Richmond
2000; Brennan and Owende 2010). Despite various advantages, its limitations
include difficulties in scale-up, low surface-to-volume ratios, poor control over
temperature, hydrodynamic stress, and wall growth (Rastogi et al. 2018).
8.2.1.2.4 Penthouse-Roof Photobioreactors (PRPBRs)
PRPBRs are mostly used in regions of temperate climatic conditions and consist of
both indoor and outdoor units. The various parameters of cultivation such as flow
rate, temperature, and oxygen levels can be easily maintained, and collectors are
used to focus and direct the light (Bahadar and Khan 2013).
8.2.1.2.5 Plastic Bag Photobioreactors (PBPBRs)
PBPBRs are attractive and are used commercially due to their lower production
costs. However, the disadvantages are photo-limitation, insufficient mixing,
possibility of leakage, shorter life span, etc. Further, the major hurdle in the
use of these systems is the disposal of large amounts of plastic bags (Wang et al.
2012; Huang et al. 2017).
8.2.1.2.6 Bubble Column Photobioreactors (BCPBRs)
BCPBRs are cylindrical vessels with a height that is more than twice the diameter, where gas mixture is bubbled through the sparger and an external light source
is used to determine its photosynthetic efficiency (Singh and Sharma 2012;
Janssen et al. 2002).
8.2.1.2.7 Helical-Type Photobioreactors (HTPBRs)
HTPBRs are comprised of coiled tubes that are flexible and transparent and have a
small diameter. The degassing unit is either separate or attached, and the culture is
made to traverse through the long tube toward the degassing unit by a centrifugal
pump. Better photosynthetic efficiency can be obtained when carbon dioxide
8 Algal Biomass: Potential Renewable Feedstock for Biofuels Production – Part I
209