Microalgal remediation and valorisation of polluted wastewaters for zero-carbon circular bioeconomy

[Display omitted] •Catastrophic consequences of CO2 emissions and tactics to mitigate them.•Zero-carbon circular bioeconomy and introduction of related practices in various countries.•Microalgae for Reduce, Recycle, Reuse and Recover concept.•Value-added products - bioenergy, pharmaceuticals, and agriculture. Overexploitation of natural resources to meet human needs has considerably impacted CO2 emissions, contributing to global warming and severe climatic change. This review furnishes an understanding of the sources, brutality, and effects of CO2 emissions and compelling requirements for metamorphosis from a linear to a circular bioeconomy. A detailed emphasis on microalgae, its types, properties, and cultivation are explained with significance in attaining a zero-carbon circular bioeconomy. Microalgal treatment of a variety of wastewaters with the conversion of generated biomass into value-added products such as bio-energy and pharmaceuticals, along with agricultural products is elaborated. Challenges encountered in large-scale implementation of microalgal technologies for low-carbon circular bioeconomy are discussed along with solutions and future perceptions. Emphasis on the suitability of microalgae in wastewater treatment and its conversion into alternate low-carbon footprint bio-energies and value-added products enforcing a zero-carbon circular bioeconomy is the major focus of this review.