incorporating metals or other additives to be released into the resultant biomass, and
complicating the downstream recycling of the materials into main and co-products.
Adverse impacts were offset in many ways, together with the used flocculants (e.g.,
polyacrylamide and starch) that are biodegradable in nature and electroflocculation
in which flocculant is not added directly.
1.3.6.2 Auto and Bioflocculation
While diverse phenomena occur, it is normal to denote auto and bioflocculation
principally as the same. Autoflocculation (flocculation alone by rise in pH) is an
appealing alternative as it is cost–efficient, lower energy requirements, low or no
toxic to microalgae, and no need for flocculants. This process can occur naturally
with limited CO 2 supply in microalgae cultures that are wide-open in sunlight during
warm and sunshiny day. Microalgae eliminate CO 2 absorbed by photosynthesis in
the culture medium and thus raise its pH content (Barros et al. 2015). Auto and
bio-flocking are both methods which use regular measures hence forcing the cells to
aggregate in floccs. In auto-flocculation, environmental factors such as salinity,
temperature, or pH are engineered to affect the surface charges of the cell and enable
the cells to come into close association so that they can stay in small groups at last.
1.3.6.3 Inorganic Flocculants and Coagulants
Typically, iron or aluminum-based inorganic flocculants and coagulants are used to
counter the surface load. This approach includes a large response of the inorganic
flocculant that supplements the sludge, adding responses and handling (to extract the
chemicals) to the OpEx (Moheimani et al. 2015). In addition, the process is
pH-sensitive and typically works greatest at higher pH but varies with strain and
crop condition. Not all strains of algae react equally to a specific chemical, therefore
alteration will be needed to suit the organism for harvestment (Chen et al. 2011).
Chemical flocculants may result in posing a problem with the downstream
processing of biomass for feed, stock feed for anaerobic digestors, and remaining
ions can pose a problem with the use of digestates for land use for soil modification
(Casey et al. 2011).
1.3.6.4 Organic Flocculants and Coagulants
It is also possible to use organic flocculants and coagulants, bridging polymers
having high molecular weight (e.g., starch and chitosan), which respond to large
aggregates with cells in the crop and aid in speeding flocculation process (Edzwald
1993). Generally, it is claimed that biomass is not contaminated by these biodegradable polymers I comparison to coagulants inorganic in nature, and that cationic
polymers are preferable over neutral along with anionic polymers. Cationic
1 Downstream Processing of Biofuels
21
complicating the downstream recycling of the materials into main and co-products.
Adverse impacts were offset in many ways, together with the used flocculants (e.g.,
polyacrylamide and starch) that are biodegradable in nature and electroflocculation
in which flocculant is not added directly.
1.3.6.2 Auto and Bioflocculation
While diverse phenomena occur, it is normal to denote auto and bioflocculation
principally as the same. Autoflocculation (flocculation alone by rise in pH) is an
appealing alternative as it is cost–efficient, lower energy requirements, low or no
toxic to microalgae, and no need for flocculants. This process can occur naturally
with limited CO 2 supply in microalgae cultures that are wide-open in sunlight during
warm and sunshiny day. Microalgae eliminate CO 2 absorbed by photosynthesis in
the culture medium and thus raise its pH content (Barros et al. 2015). Auto and
bio-flocking are both methods which use regular measures hence forcing the cells to
aggregate in floccs. In auto-flocculation, environmental factors such as salinity,
temperature, or pH are engineered to affect the surface charges of the cell and enable
the cells to come into close association so that they can stay in small groups at last.
1.3.6.3 Inorganic Flocculants and Coagulants
Typically, iron or aluminum-based inorganic flocculants and coagulants are used to
counter the surface load. This approach includes a large response of the inorganic
flocculant that supplements the sludge, adding responses and handling (to extract the
chemicals) to the OpEx (Moheimani et al. 2015). In addition, the process is
pH-sensitive and typically works greatest at higher pH but varies with strain and
crop condition. Not all strains of algae react equally to a specific chemical, therefore
alteration will be needed to suit the organism for harvestment (Chen et al. 2011).
Chemical flocculants may result in posing a problem with the downstream
processing of biomass for feed, stock feed for anaerobic digestors, and remaining
ions can pose a problem with the use of digestates for land use for soil modification
(Casey et al. 2011).
1.3.6.4 Organic Flocculants and Coagulants
It is also possible to use organic flocculants and coagulants, bridging polymers
having high molecular weight (e.g., starch and chitosan), which respond to large
aggregates with cells in the crop and aid in speeding flocculation process (Edzwald
1993). Generally, it is claimed that biomass is not contaminated by these biodegradable polymers I comparison to coagulants inorganic in nature, and that cationic
polymers are preferable over neutral along with anionic polymers. Cationic
1 Downstream Processing of Biofuels
21