one of the top notch research topics especially in the context of escalating petro fuel
prices and climatic changes. Microalgae are characterized by an exceptionally
speedy growth rate in comparison to plants/energy crops and additionally a significant proportion of their weight comprises oil. The microalgal oil following suitable
extraction procedures can be reacted with an alcohol to get biodiesel which is
renewable and environmental benign in nature. Also from the theoretical perspective, microalgae present strong candidature as a viable bioenergy feedstock for
biodiesel production. The yield of oil from microalgae (on per unit area basis) is
predicted to be 20,000–80,000 L/acre/year (Demirbas and Demirbas 2010). The
theoretical yield is 7–31 times higher than palm oil (the next best crop for the
production of biodiesel) (Demirbas and Demirbas 2010). Microalgae have been
hypothesized to be the sole source of renewable biodiesel competent of meeting
the international demand for liquid transportation fuels (Chisti 2007).
7.3.2 Bio-Oil from Microalgae
Biodiesel production from microalgae involves lipid extraction followed by
transesterification. Following lipid extraction the microalgal de-oiled cake/remnants
(low value biomasses refuse devoid of oil) are left. Finding suitable prospects for the
microalgal de-oiled cake is one of the utmost challenges for the forthcoming
microalgal bio-refineries (Ferrell and Sarisky-Reed 2010). Previously the microalgal
de-oiled cakes were used as an aquaculture feed. But now with the energy crisis
hitting the block, scientists are more concerned in finding suitable energy based
options from the de-oiled cakes. One feasible alternative in this regard which would
also be influential in reducing the economics of feedstock utility is pyrolysis of
microalgal remnants to obtain renewable bio-oil and other value added products
(bio-char and syn-gas). A few studies done in this direction by Pan et al. 2010, Wang
et al. 2013 warrant the feasibility of pyrolytic bio-oil production from microalgal
remnants.
In the wake of recent advancements in bioenergy research pyrolytic bio-oils have
already gathered the attention of the scientific community in that they offer potential
candidature not only as a chemical feedstock but also as a progressively attractive
fuel option. However, it is interesting to note that there is dearth of scientific
information about pyrolysis of direct microalgal biomass or its remnants in comparison to the pyrolysis of lignocellulosic biomass. A few studies have been conducted
in this regard (Du et al. 2011; Miao et al. 2004; Miao and Wu 2004). Researchers
have suggested that thermo-chemical conversion of de-oiled cake via pyrolysis can
produce bio-oil which in some admiration is superior to bio-oil obtainable via
pyrolysis of lignocellulosic biomass (Du et al. 2011, Miao et al. 2004, Miao and
Wu 2004).
A major lacuna of microalgal biomass as a pyrolysis feedstock is the elevated
nitrogen content in the bio-oil product. As per previous studies (Becker 2006) most
of this nitrogen is present as protein in fast growing autotrophic microalgae. Additional nitrogenous ingredients of microalgae comprise nucleic acids (DNA and
7 Aquatic Microbial Oxygenic Phototrophs: A Short Treatise on Diverse. . .
145
prices and climatic changes. Microalgae are characterized by an exceptionally
speedy growth rate in comparison to plants/energy crops and additionally a significant proportion of their weight comprises oil. The microalgal oil following suitable
extraction procedures can be reacted with an alcohol to get biodiesel which is
renewable and environmental benign in nature. Also from the theoretical perspective, microalgae present strong candidature as a viable bioenergy feedstock for
biodiesel production. The yield of oil from microalgae (on per unit area basis) is
predicted to be 20,000–80,000 L/acre/year (Demirbas and Demirbas 2010). The
theoretical yield is 7–31 times higher than palm oil (the next best crop for the
production of biodiesel) (Demirbas and Demirbas 2010). Microalgae have been
hypothesized to be the sole source of renewable biodiesel competent of meeting
the international demand for liquid transportation fuels (Chisti 2007).
7.3.2 Bio-Oil from Microalgae
Biodiesel production from microalgae involves lipid extraction followed by
transesterification. Following lipid extraction the microalgal de-oiled cake/remnants
(low value biomasses refuse devoid of oil) are left. Finding suitable prospects for the
microalgal de-oiled cake is one of the utmost challenges for the forthcoming
microalgal bio-refineries (Ferrell and Sarisky-Reed 2010). Previously the microalgal
de-oiled cakes were used as an aquaculture feed. But now with the energy crisis
hitting the block, scientists are more concerned in finding suitable energy based
options from the de-oiled cakes. One feasible alternative in this regard which would
also be influential in reducing the economics of feedstock utility is pyrolysis of
microalgal remnants to obtain renewable bio-oil and other value added products
(bio-char and syn-gas). A few studies done in this direction by Pan et al. 2010, Wang
et al. 2013 warrant the feasibility of pyrolytic bio-oil production from microalgal
remnants.
In the wake of recent advancements in bioenergy research pyrolytic bio-oils have
already gathered the attention of the scientific community in that they offer potential
candidature not only as a chemical feedstock but also as a progressively attractive
fuel option. However, it is interesting to note that there is dearth of scientific
information about pyrolysis of direct microalgal biomass or its remnants in comparison to the pyrolysis of lignocellulosic biomass. A few studies have been conducted
in this regard (Du et al. 2011; Miao et al. 2004; Miao and Wu 2004). Researchers
have suggested that thermo-chemical conversion of de-oiled cake via pyrolysis can
produce bio-oil which in some admiration is superior to bio-oil obtainable via
pyrolysis of lignocellulosic biomass (Du et al. 2011, Miao et al. 2004, Miao and
Wu 2004).
A major lacuna of microalgal biomass as a pyrolysis feedstock is the elevated
nitrogen content in the bio-oil product. As per previous studies (Becker 2006) most
of this nitrogen is present as protein in fast growing autotrophic microalgae. Additional nitrogenous ingredients of microalgae comprise nucleic acids (DNA and
7 Aquatic Microbial Oxygenic Phototrophs: A Short Treatise on Diverse. . .
145