Multifaceted application of microalgal biomass integrated with carbon dioxide reduction and wastewater remediation: A flexible concept for sustainable environment

Microalgae are ubiquitous, diverse, and photosynthetic organisms in nature and have prominent applications in carbon dioxide (CO₂) mitigation and wastewater remediation. This review has compiled the recent trends in the potential application of microalgae for wastewater treatment and combating CO₂ emissions and multifaceted use of its biomass for the co-production of bioenergy and human health products. In specific, this review critically addressed; (a) global scenario of carbon footprint and wastewater remediation and concept of circular bioeconomy, (b) approaches of sterile and non-sterile cultivation of microalgae, (c) state-of-art biorefinery especially for harvesting of algal biomass, d) details of microalgal high-value compounds (HVAC) such as lipids, fatty acids, carbohydrates, carotenoids, sterols, and polyphenolic compounds, (e) recent biomass to biofuel strategies, and (f) market analysis, recent challenges and future progress. The review establishes that the microalgae can simultaneously treat different types of wastewater, recover nutrients/metals, and mitigate CO₂ from flue gas via its biofixation ability. The flocculation method is found to be best for harvesting the algal biomass. The non-sterile cultivated biomass can be utilized for biofuels production, and sterile biomass can be used to produce HVAC compounds that have significant application in human health.