A state of the art review on the cultivation of algae for energy and other valuable products: Application, challenges, and opportunities

Algae have long been investigated as a plausible reserve of several biofuel and bioactive compounds attributed to their fast-growing characteristics, shorter doubling time, and capability of accumulating lipids. Compounds extracted from algae are being studied in various sectors namely, pharmaceutical, cosmetics, cancer biology, nanoscience, food industry, etc. In view of the rich potentials of algae, this present review is aimed to highlight the significance of different cultivation aspects of microalgae like open pond and photobioreactor and advantages and disadvantages thereof. This state-of-the-art review provides the limitations of energy (biodiesel, bioethanol, biohydrogen, biomethane) products obtained from the algae in a perspective of shifting lab-scale into a field scale. In addition to the cultivation systems and biofuels, several non-energy products or value-added products obtained from algae were critically compared and presented. Data from plethora literatures discussing the advanced methods for the extraction of omega-3, omega-6 fatty acids, vitamins and nanoparticles from algae have been discussed extensively. Further, bioactive compounds extracted from several algal strains were listed. Considering the health benefits, anti-angiogenic, and anti–cancer properties of algal bioactive compounds were described along with other industrial applications. Overall, this comprehensive review will help in understanding status of algal biofuel, cultivation systems, metabolites and their application for the betterment of the human society. •Types of microalgal cultivation systems and their challenges were discussed.•Limitations of various biofuels produced from microalgae were presented.•Omega-3 fatty acids, vitamins and nanoparticles from algae were summarized.•Anticancer, antiangiogenic activities of microalgal products were specified.•Economics and environmental impacts of algal bio-refinery were analyzed.