Environmental Engineering Reference
In-Depth Information
Green water comprised of difference between
water obtained as precipitation and that lost
through soil moisture evaporation and evapo-
transpiration. The microalgae-based biofuel had
a blue WF varied as a function of pathway in-
volved in the production of fuel and location and
ranged from 23-85 m
3
ﾷGJ
−1
. It has been reported
that the process water uses during cultivation,
harvesting, and extraction accounts for majority
of the blue WF (97.6 %) which was followed by
fuel conversion (2.4 %) and transportation and
distribution (0.002 %). The green WF from mi-
croalgae based biofuel has been reported to be
negative thus showing water gain in the basin.
The green WF has been reported to vary among
the geographic locations from 1.3-17 m
3
ﾷGJ
−1
.
The total WF comprising both blue and green
water ranged from 18-82 m
3
ﾷGJ
−1
. The sustain-
ability of production of biofuel from microalgae
in terms of WF lies in the usability of wastewa-
ter. Utilization of domestic and industrial waste-
water for the culture of microalgae thus has the
potential to lower the total WF in synthesis of
biodiesel.
of oil and biodiesel respectively. This has been
attributed to high demand for energy in the pro-
duction process. With biorefinery approach, the
carbon footprint is expected to get lower owing
to production of more than one utility product.
8.4
Sustainable Production of
Biofuels
8.4.1
Value Added Product Basket:
Pigments, Nutraceuticals and
Bioactive Compounds
Microalgae are a very diverse group of organ-
isms that are the key components of ecosystems
and produce a variety of valuable compounds as
secondary metabolites in different phases of life
cycle (Pulz and Gross
2004
; Skjanes et al.
2013
).
Microalgal biomass cultivation is regarded as a
potential way to overcome our current depen-
dence on fossil fuels, as microalgal biomass can
be utilized for synthesis of number of biofuels
like biodiesel, bioethanol, biohydrogen (Guldhe
et al.
2014
; Singh et al.
2014
). High production
cost has become a major bottleneck for biofu-
els production from microalgae (Spolaore et al.
2006
). However, integrated biorefinary approach
can make microalgal biofuel production econom-
ically viable (Vanthoor-Koopmans et al.
2013
).
Commercial realization of the microalgae as
a source of renewable biofuel is feasible when
constituents of the algal biomass are exploited
for biofuels as well as for value added coprod-
ucts (Yen et al.
2013
). Thus, the development and
focus was changed toward the potential of grow-
ing microalgae commercially for its applications
in field of health food for human consumption,
aquaculture and animal feed, coloring agents,
cosmetics, and other commercial products. Car-
bohydrate, protein, and lipids are the major con-
stituents of microalgae which can be exploited
commercially for different markets (Borowitzka
2013
). Other compounds viz., fatty acids and
steroids, carotenoids, phycocolloids, lectins,
mycosporine-like amino acids, halogenated com-
pounds, polyketides, and toxins, synthesized by
8.3.2
Carbon Footprint
With the increasing environmental concerns, the
usage of biofuels has increased considerably.
Hence, just like the carbon footprint is accounted
for fossil fuels, the biofuels also should be mea-
sured in terms of carbon footprints (Johnson and
Tschudi
2012
). Hammond and Seth (
2013
) esti-
mated the global carbon footprint of biofuels to
be 0.248 bn global hectares (gha) in 2010 and
may reach to 0.449 bn gha by 2019. It was also
estimated that the total environmental footprint
of the global biofuel produced was 0.720 bn gha
for 2010 and could reach 1.242 bn gha by 2019.
Fahd et al. (
2012
) reported the carbon footprint
during the production of biodiesel. It was re-
ported that the emission of CO
2
and other green
house gases were relatively low during the pro-
duction of seeds that amounted to 0.53 g
CO2-
equiv
per g dry seed. In the processing steps, i.e.,
oil extraction and biodiesel production, the emis-
sions reported is 0.99 and 1.72 g
CO2-equiv
per g
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