2.4 Bioethanol
Ethanol can be produced from algal bloom by fermenting the algae with microorganisms which is capable of metabolizing sugars. Algae have various carbohydrates
such as starch, cellulose, laminarin, mannitol, and agar which can be fermented with
suitable microorganisms to give a good yield of bio ethanol [27]. The kelp Laminaria digitata which is highly prevalent along the coast of the UK especially in the
month of July was fermented with yeast Pichia angophorae owing to its high
laminarin and mannitol content. A maximum yield of 167 mL ethanol at approximately 69 h incubation was obtained at 5% dry weight kelp, pH 4, and at 24
C
[37]. Laminarales especially L. hyperborean collected from the Norwegian coast
was fermented with Zymobacter palmae under anaerobic conditions and gave a
maximum ethanol yield of 0.38 g ethanol (g mannitol)
À1 . This yield was attributed to
the carbohydrates present in the Laminarales fronds [46]. Saccharomyces cerevisiae
was used to ferment L. japonica collected from the floating residue of L. japonica
industry, China, at 30
C for 36 h, and 0.143 L ethanol from 1 kg floating residue
could be achieved on acid pretreatment followed by enzymatic hydrolysis [47].
2.5 Adsorbent
Algae has the ability to store fluorides and heavy metals than any other land or
aquatic species [48–54]. Algal biomass is collected, dried, and used such as an
adsorbent or can be subjected to chemical treatment to enhance its adsorption
capacity. Algal bloom in a wastewater treatment plant in coke-oven industry was
valorized into a potential biosorbent. A consortia of Leptolyngbya foveolaurum and
Chlorococcum infusionum was found in the storage tank of wastewater effluent
treatment plant. The algal bloom hindered the reuse of the water after tertiary
treatment by increasing the pH and biological oxygen demand of the treated water.
The dry biomass was subjected to adsorption of fluoride, and the adsorption capacity
of the mixed consortia was found to be 34.36 mg/g at temperature 30
C for an
adsorbent dosage of 3.5 g/L. The adsorption characteristics were best explained by
Freundlich isotherm model and first-order kinetic model [23]. A similar case was
reported for the algal biomass collected from ponds in Osmania University campus,
Hyderabad, India. The algal biomass was dried, and the dried algal biomass was used
for fluoride removal which gave a fluoride removal of 64% for 300 min and followed
a pseudofirst-order kinetic model [55].
2.6 Biofertilizer
Algae can be dried, powdered, and applied as such to plants or can be composted
with other biomass before application as fertilizer. Eutrophied algal bloom compost
can be both mature and highly stable which has high potential as a soil amendment
Valorization of Waste Algal Boom for Value-Added Products
133
Ethanol can be produced from algal bloom by fermenting the algae with microorganisms which is capable of metabolizing sugars. Algae have various carbohydrates
such as starch, cellulose, laminarin, mannitol, and agar which can be fermented with
suitable microorganisms to give a good yield of bio ethanol [27]. The kelp Laminaria digitata which is highly prevalent along the coast of the UK especially in the
month of July was fermented with yeast Pichia angophorae owing to its high
laminarin and mannitol content. A maximum yield of 167 mL ethanol at approximately 69 h incubation was obtained at 5% dry weight kelp, pH 4, and at 24
C
[37]. Laminarales especially L. hyperborean collected from the Norwegian coast
was fermented with Zymobacter palmae under anaerobic conditions and gave a
maximum ethanol yield of 0.38 g ethanol (g mannitol)
À1 . This yield was attributed to
the carbohydrates present in the Laminarales fronds [46]. Saccharomyces cerevisiae
was used to ferment L. japonica collected from the floating residue of L. japonica
industry, China, at 30
C for 36 h, and 0.143 L ethanol from 1 kg floating residue
could be achieved on acid pretreatment followed by enzymatic hydrolysis [47].
2.5 Adsorbent
Algae has the ability to store fluorides and heavy metals than any other land or
aquatic species [48–54]. Algal biomass is collected, dried, and used such as an
adsorbent or can be subjected to chemical treatment to enhance its adsorption
capacity. Algal bloom in a wastewater treatment plant in coke-oven industry was
valorized into a potential biosorbent. A consortia of Leptolyngbya foveolaurum and
Chlorococcum infusionum was found in the storage tank of wastewater effluent
treatment plant. The algal bloom hindered the reuse of the water after tertiary
treatment by increasing the pH and biological oxygen demand of the treated water.
The dry biomass was subjected to adsorption of fluoride, and the adsorption capacity
of the mixed consortia was found to be 34.36 mg/g at temperature 30
C for an
adsorbent dosage of 3.5 g/L. The adsorption characteristics were best explained by
Freundlich isotherm model and first-order kinetic model [23]. A similar case was
reported for the algal biomass collected from ponds in Osmania University campus,
Hyderabad, India. The algal biomass was dried, and the dried algal biomass was used
for fluoride removal which gave a fluoride removal of 64% for 300 min and followed
a pseudofirst-order kinetic model [55].
2.6 Biofertilizer
Algae can be dried, powdered, and applied as such to plants or can be composted
with other biomass before application as fertilizer. Eutrophied algal bloom compost
can be both mature and highly stable which has high potential as a soil amendment
Valorization of Waste Algal Boom for Value-Added Products
133