Microalgae-based flue gas CO₂ sequestration for cleaner environment and biofuel feedstock production: a review

Anthropogenic CO₂ emissions are the prime cause of global warming and climate change, promoting researchers to develop suitable technologies to reduce carbon footprints. Among various CO₂ sequestration technologies, microalgal-based methods are found to be promising due to their easier operation, environmental benefits, and simpler equipment requirements. Microalgae-based carbon capture and storage (CCS) technology is essential for addressing challenges related to the use of industrial-emitted flue gases. This review focuses on the literature concerning the microalgal application for CO₂ sequestration. It highlights the primary physiochemical parameters that affect microalgal-based CO₂ biofixation, including light exposure, microalgal strain, temperature, inoculum size, pH levels, mass transfer, CO₂ concentration, flow rate, cultivation system, and mixing mechanisms. Moreover, the inhibition effect of different flue gas components including NO_x, SO_x, and Hg on growth kinetics is discussed to enhance the capacity of microalgal-based CO₂ biofixation, along with deliberated challenges and prospects for future development. Overall, the review indicated microalgal-based flue gas CO₂ fixation rates range from 80 mg L^-1 day^-1 to over 578 mg L^-1 day^-1, primarily influenced by physiochemical parameters and flue gas composition. This article summarizes the mechanisms and stages of microalgal-based CO₂ sequestration and provides a comprehensive review based on international interest in this green technology.