algae which gave a biogas yield of 1,184 mL g
À1 VS
À1 with 54.9%, methane content
for a cumulative 30 days period [36]. Fresh Ulva gave a biomethane yield of 183 L
CH 4 /kg VS, and dried, washed, and macerated Ulva gave a biomethane yield of
250 L CH 4 /kg VS. Codigestion with diary slurry gave a biomethane yield of 220 L
CH 4 /kg VS [2]. It should be noted that due to seasonal variations, the methane yield
will be different for various species of algae [37]. Generally macroalgae commonly
known as seaweeds yield a considerably lower amount of methane [38]. Mixed
samples of Pilayella sp., Ectocarpus sp., Polysiphonia sp., Cladophora sp., and
Enteromorpha sp. with small amount of seagrass Z. marina which were collected
from Sopot beach, Poland, and Skåre beach in Sweden were found to have good C/N
ratio and could be an alternative solution for codigestion with other biomass
[39]. Methane production from anaerobic digestion of whole seaweeds or their
residues after alginate extraction is more viable from an environmental point of
view than the exploitation of natural gas [40].
2.2 Biochar
Biochar can be produced from algal blooms by pyrolysis which is a high temperature
thermal decomposition in an inert atmosphere. Lyngbya species and Cladophora
species, algal blooms, from Maumee bay of Lake Erie, USA, were collected and
pyrolyzed at 510–600
C to yield a biochar (48 wt% of algal mass) having a calorific
value of 25.6 (MJ/kg). Algal biochar made by this thermochemical method also had
a significantly higher nitrogen content [41]. Biochar can be used as a soil amendment
which increases quality of soil by increasing nutrient retention capability of soil.
Biochar has good tensile strength and hence can be used in the production of carbon
nanotubes, activated carbon, and carbon fibers [42]. Synthesis gas can also be
produced by steam reformation of biochar [43].
2.3 Biooil
Biooil or more specifically algal oil can be produced by subjecting the algal bloom to
thermal degradation in the absence of air at temperatures usually ranging from 300 to
900
C. Microcystis species, a blue-green alga which was harvested from Dianchi
Lake in China, was subjected to pyrolysis in a fixed bed reactor from 300 to 700
C,
and a maximum of 54.97% biooil was obtained with a heating value of 31.9 MJ/kg
which was much higher than pyrolysis of cellulose materials [44]. Algal bloom from
Meiliang Bay of Taihu Lake, China, was pyrolyzed from 300 to 700
C in a fixed bed
reactor to yield 59% biooil with a higher heating value of 21 MJ/kg [45]. It is the
most promising product which has high heating value and can be used for production
of electricity or heat or for cogeneration or as feed stock for industrial operations.
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A. Annam Renita and P. Senthil Kumar
À1 VS
À1 with 54.9%, methane content
for a cumulative 30 days period [36]. Fresh Ulva gave a biomethane yield of 183 L
CH 4 /kg VS, and dried, washed, and macerated Ulva gave a biomethane yield of
250 L CH 4 /kg VS. Codigestion with diary slurry gave a biomethane yield of 220 L
CH 4 /kg VS [2]. It should be noted that due to seasonal variations, the methane yield
will be different for various species of algae [37]. Generally macroalgae commonly
known as seaweeds yield a considerably lower amount of methane [38]. Mixed
samples of Pilayella sp., Ectocarpus sp., Polysiphonia sp., Cladophora sp., and
Enteromorpha sp. with small amount of seagrass Z. marina which were collected
from Sopot beach, Poland, and Skåre beach in Sweden were found to have good C/N
ratio and could be an alternative solution for codigestion with other biomass
[39]. Methane production from anaerobic digestion of whole seaweeds or their
residues after alginate extraction is more viable from an environmental point of
view than the exploitation of natural gas [40].
2.2 Biochar
Biochar can be produced from algal blooms by pyrolysis which is a high temperature
thermal decomposition in an inert atmosphere. Lyngbya species and Cladophora
species, algal blooms, from Maumee bay of Lake Erie, USA, were collected and
pyrolyzed at 510–600
C to yield a biochar (48 wt% of algal mass) having a calorific
value of 25.6 (MJ/kg). Algal biochar made by this thermochemical method also had
a significantly higher nitrogen content [41]. Biochar can be used as a soil amendment
which increases quality of soil by increasing nutrient retention capability of soil.
Biochar has good tensile strength and hence can be used in the production of carbon
nanotubes, activated carbon, and carbon fibers [42]. Synthesis gas can also be
produced by steam reformation of biochar [43].
2.3 Biooil
Biooil or more specifically algal oil can be produced by subjecting the algal bloom to
thermal degradation in the absence of air at temperatures usually ranging from 300 to
900
C. Microcystis species, a blue-green alga which was harvested from Dianchi
Lake in China, was subjected to pyrolysis in a fixed bed reactor from 300 to 700
C,
and a maximum of 54.97% biooil was obtained with a heating value of 31.9 MJ/kg
which was much higher than pyrolysis of cellulose materials [44]. Algal bloom from
Meiliang Bay of Taihu Lake, China, was pyrolyzed from 300 to 700
C in a fixed bed
reactor to yield 59% biooil with a higher heating value of 21 MJ/kg [45]. It is the
most promising product which has high heating value and can be used for production
of electricity or heat or for cogeneration or as feed stock for industrial operations.
132
A. Annam Renita and P. Senthil Kumar