8.7.1 Biodiesel Production via Algal Biomass
It is a nontoxic fuel exhibiting high flash point than diesel (50
C and 65
C), has
10% built-in oxygen which allows complete burning, fails to emit sulfur oxides, and
reduces the level of carbon monoxide, unburned hydrocarbons, and other pollutants
(Hemaiswarya et al. 2012). The most commonly used algal feedstocks used for
biofuel production include green algae Chlorella sp. and Chlorococcum sp. In
particular strains such as Haematococcus and Neochlorosis are perfect for biodiesel
and Chlorella, Scenedesmus, and Spirulina for biomethanol production (Maity et al.
2014). Marine microalgae C. vulgaris yielded 22% lipid content and 61% biodiesel
(Mathimani et al. 2015). Moreover, C. vulgaris produced biodiesel, and freshwater
Chlorella strain accumulated high lipid in comparison to cyanobacterial strains
(Mathimani and Nair 2016). As per Maity et al. (2014) Chlorella and
Nannochloropsis strains showed 100 mg/L/day lipid productivity.
8.7.2 Bioethanol Production from Microalgae
The extensive use of sugar and starch materials for the production of bioethanol has
created major competition within the food market in terms of land for cultivation,
making the bioethanol production from these sources economically less feasible
(de Farias Silva and Bertucco 2016; Shuba and Kifle 2018). Thus, microalgae have
been used as an effective alternative as the issues which are present in S
nd GB have
been overcome in T
rd GB. Presently, Chlorella vulgaris has been a good source of
ethanol production due to its high starch content, where 65% ethanol conversion
efficiency has been reported (Shuba and Kifle 2018).
8.7.3 Biohydrogen Production from Microalgae
Hydrogen has been regarded as the “future energy carrier” as it excludes the use of
carbon dioxide in combustion, generates huge energy per unit, and can be
transformed to electricity by fuel cells. The current production of hydrogen is a
fossil fuel-based process and produces large amounts of greenhouse gases (Shuba
and Kifle 2018). As per Melis (2002) by depleting the quantity of sulfur available to
the algae, the internal oxygen flow is interrupted, thereby allowing the production of
hydrogen by hydrogenase. Later, Chochois et al. (2009) stated that direct photolysis
is responsible for the production of hydrogen in C. reinhardtii. The cells are
illuminated after they have adapted to anaerobic conditions, and the electrons
originating from the splitting of water at PSII are driven by photosynthetic electron
transport chain to ferredoxin and then to a reversible iron hydrogenase, thus enabling
the production of hydrogen from water and solar energy (Fig. 8.3). Three methods
can be used to produce hydrogen from algae (i.e., biochemical process, gasification,
and steam reforming).
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K. Agrawal et al.
It is a nontoxic fuel exhibiting high flash point than diesel (50
C and 65
C), has
10% built-in oxygen which allows complete burning, fails to emit sulfur oxides, and
reduces the level of carbon monoxide, unburned hydrocarbons, and other pollutants
(Hemaiswarya et al. 2012). The most commonly used algal feedstocks used for
biofuel production include green algae Chlorella sp. and Chlorococcum sp. In
particular strains such as Haematococcus and Neochlorosis are perfect for biodiesel
and Chlorella, Scenedesmus, and Spirulina for biomethanol production (Maity et al.
2014). Marine microalgae C. vulgaris yielded 22% lipid content and 61% biodiesel
(Mathimani et al. 2015). Moreover, C. vulgaris produced biodiesel, and freshwater
Chlorella strain accumulated high lipid in comparison to cyanobacterial strains
(Mathimani and Nair 2016). As per Maity et al. (2014) Chlorella and
Nannochloropsis strains showed 100 mg/L/day lipid productivity.
8.7.2 Bioethanol Production from Microalgae
The extensive use of sugar and starch materials for the production of bioethanol has
created major competition within the food market in terms of land for cultivation,
making the bioethanol production from these sources economically less feasible
(de Farias Silva and Bertucco 2016; Shuba and Kifle 2018). Thus, microalgae have
been used as an effective alternative as the issues which are present in S
nd GB have
been overcome in T
rd GB. Presently, Chlorella vulgaris has been a good source of
ethanol production due to its high starch content, where 65% ethanol conversion
efficiency has been reported (Shuba and Kifle 2018).
8.7.3 Biohydrogen Production from Microalgae
Hydrogen has been regarded as the “future energy carrier” as it excludes the use of
carbon dioxide in combustion, generates huge energy per unit, and can be
transformed to electricity by fuel cells. The current production of hydrogen is a
fossil fuel-based process and produces large amounts of greenhouse gases (Shuba
and Kifle 2018). As per Melis (2002) by depleting the quantity of sulfur available to
the algae, the internal oxygen flow is interrupted, thereby allowing the production of
hydrogen by hydrogenase. Later, Chochois et al. (2009) stated that direct photolysis
is responsible for the production of hydrogen in C. reinhardtii. The cells are
illuminated after they have adapted to anaerobic conditions, and the electrons
originating from the splitting of water at PSII are driven by photosynthetic electron
transport chain to ferredoxin and then to a reversible iron hydrogenase, thus enabling
the production of hydrogen from water and solar energy (Fig. 8.3). Three methods
can be used to produce hydrogen from algae (i.e., biochemical process, gasification,
and steam reforming).
224
K. Agrawal et al.