Reframing Microalgal Flue Gas Valorization Beyond Carbon Metrics Within A Sustainable Development Paradigm

The increasing concentration of atmospheric CO₂ due to fossil fuel–based industrial activities has intensified the need for effective and sustainable carbon mitigation strategies. Microalgae have attracted significant attention as promising biological systems due to their high biomass yields, photosynthetic efficiency, rapid growth rates and ability to utilize CO₂. In addition to carbon capture, microalgae offer the potential for wastewater treatment and the production of value-added products such as biofuels and biochemicals. Industrial flue gas, commonly regarded as a major emission source, contains not only CO₂ but also nitrogen and sulfur oxides that may serve as nutrients for microalgal growth under controlled conditions. This review critically examines microalgal flue gas valorization from the perspective of carbon neutrality, carbon negativity and sustainable development. The mechanisms of CO₂ fixation, the physiological responses of microalgae to flue gas components and the key technical and environmental limitations of large-scale applications are discussed. The study emphasizes that microalgal technologies should be assessed within a holistic sustainability framework that integrates carbon mitigation, resource efficiency and environmental impacts. Such an approach is essential for advancing microalgae based systems as viable tools for climate action and sustainable development.