if the existent research gaps are addressed properly. Research gaps need to be
addressed for cost cutting in every step of the supply chain and commercially realize
the full potential of microalgal biofuel and associated value added products. An
integrated bio-refinery based approach is always preferable, where in the microalgal
feedstock can be converted to biofuel in conjugation with a spectrum of other
valuable products. The idea of zero waste bio-refineries is very popular in modern
times, where in any waste generated in the production scheme automatically
becomes the feedstock for the next product. Although significant progress has
been achieved in the field of microalgal biotechnology, much more strenuous
research is warranted to realize economically competitive algal biofuel and other
value added products. Many subareas such as microalgal biology, strain improvement, microalgal cultivation systems (mostly mass culture approaches), process
optimization, microalgal harvest and dewatering, new extraction technologies,
genetically engineered strains (GMOs), biomass conversion, product recovery, coproduct generation, value addition, fuel processing, economic analysis, etc., still
remain the cardinal check points. However, addressing all these is beyond the scope
of the present article. This article will consider only the life cycle assessment part.
Although microalgae based biofuel production is emerging out as a top notch
domain of research, there are many challenges and technical obstacles for massive
commercialization of the fuel processing technologies. Microalgal biofuel production involves complicated cultivation, harvesting, dewatering, oil extraction, conversion, and purification steps. Adoption of suitable and efficient harvesting, extraction,
or conversion technology is very crucial for an overall sustainable process economics (Shi et al. 2019).
Several methodologies for assessing environmental impacts and better
sustainability for chemical process industry have been followed in recent years.
Life cycle assessment (LCA) study among these is viewed as of paramount importance and imperative for microalgae based biofuel productions (Shi et al. 2019;
Wang et al. 2011; Lardon et al. 2009). However, these analyses also give different
results as biofuel production from microalgae largely relies on assumptions
pertaining to algae cultivation methods, biomass yield and lipid content parameters,
oil extraction methods and post treatment processes related to purification and
upgradation (if any). For example, dewatering has been proposed as the most energy
consuming and GHG emitting steps in an overall LCA of algae biodiesel production
(Sander and Murthy 2010).
Another LCA results reported that flocculation had the lowest impact among
three algae harvesting options, namely centrifugation, filtration, and flocculation/
settling. The results of the study also showed chitosan and hexane as the most
suitable, energy intensive flocculant and solvent, respectively (Brentner et al. 2011).
In a recent finding, “after modeling 160 pathways for combinations of different
technologies of each process stage, the overall best-case scenario for well-to-wheel
study was found to be flat-plate photo-bioreactor cultivation, chitosan flocculation,
supercritical methanol combined extraction and transesterification, and energy recycle through recovery of biogas, from a LCA perspective, and total life cycle GHG
emission amounts to 8.05 g CO 2 eq per MJ of biodiesel (Shi et al. 2019).” Although,
7 Aquatic Microbial Oxygenic Phototrophs: A Short Treatise on Diverse. . .
147
addressed for cost cutting in every step of the supply chain and commercially realize
the full potential of microalgal biofuel and associated value added products. An
integrated bio-refinery based approach is always preferable, where in the microalgal
feedstock can be converted to biofuel in conjugation with a spectrum of other
valuable products. The idea of zero waste bio-refineries is very popular in modern
times, where in any waste generated in the production scheme automatically
becomes the feedstock for the next product. Although significant progress has
been achieved in the field of microalgal biotechnology, much more strenuous
research is warranted to realize economically competitive algal biofuel and other
value added products. Many subareas such as microalgal biology, strain improvement, microalgal cultivation systems (mostly mass culture approaches), process
optimization, microalgal harvest and dewatering, new extraction technologies,
genetically engineered strains (GMOs), biomass conversion, product recovery, coproduct generation, value addition, fuel processing, economic analysis, etc., still
remain the cardinal check points. However, addressing all these is beyond the scope
of the present article. This article will consider only the life cycle assessment part.
Although microalgae based biofuel production is emerging out as a top notch
domain of research, there are many challenges and technical obstacles for massive
commercialization of the fuel processing technologies. Microalgal biofuel production involves complicated cultivation, harvesting, dewatering, oil extraction, conversion, and purification steps. Adoption of suitable and efficient harvesting, extraction,
or conversion technology is very crucial for an overall sustainable process economics (Shi et al. 2019).
Several methodologies for assessing environmental impacts and better
sustainability for chemical process industry have been followed in recent years.
Life cycle assessment (LCA) study among these is viewed as of paramount importance and imperative for microalgae based biofuel productions (Shi et al. 2019;
Wang et al. 2011; Lardon et al. 2009). However, these analyses also give different
results as biofuel production from microalgae largely relies on assumptions
pertaining to algae cultivation methods, biomass yield and lipid content parameters,
oil extraction methods and post treatment processes related to purification and
upgradation (if any). For example, dewatering has been proposed as the most energy
consuming and GHG emitting steps in an overall LCA of algae biodiesel production
(Sander and Murthy 2010).
Another LCA results reported that flocculation had the lowest impact among
three algae harvesting options, namely centrifugation, filtration, and flocculation/
settling. The results of the study also showed chitosan and hexane as the most
suitable, energy intensive flocculant and solvent, respectively (Brentner et al. 2011).
In a recent finding, “after modeling 160 pathways for combinations of different
technologies of each process stage, the overall best-case scenario for well-to-wheel
study was found to be flat-plate photo-bioreactor cultivation, chitosan flocculation,
supercritical methanol combined extraction and transesterification, and energy recycle through recovery of biogas, from a LCA perspective, and total life cycle GHG
emission amounts to 8.05 g CO 2 eq per MJ of biodiesel (Shi et al. 2019).” Although,
7 Aquatic Microbial Oxygenic Phototrophs: A Short Treatise on Diverse. . .
147