Environmental pollution mitigation through utilization of carbon dioxide by microalgae

Anthropogenic emissions of CO₂ have reached a critical level and the global surface temperature is expected to rise by 1.5 °C between 2030 and 2050. To ameliorate the current global warming scenario, the research community has been struggling to find more economical and innovative solutions for carbon sequestration. Among such techniques, the use of microalgal species such as Chlorella sp., Dunaliella tertiolecta, Spirulina platensis, Desmodesmus sp., and Nannochloropsis sp., among others have shown high carbon tolerance capacity (10-100%) for establishing carbon capture, utilization and storage systems. To make microalgal-based carbon capture more economical, the microalgal biomass (∼2 g/L) can be converted biofuels, pharmaceuticals and nutraceuticals through biorefinery approach with product yield in the range of 60-99.5%. Further, CRISPR-Cas9 has enabled the knockout of specific genes in microalgal species that can be used to generate low pH tolerant strains with high lipid production. Inspite of the emerging developments in pollution control by microalgae, only limited investigations are available on its economic aspects which indicate a production cost of ∼$ 0.5-15/kg microalgal biomass. This review intends to summarize the advancements in different carbon sequestration techniques while highlighting their mechanisms and major research areas that need attention for economical microalgae-based carbon sequestration.