Harnessing the potential of microalgae for carbon sequestration to achieve net-zero emissions

Increasing concentration of greenhouse gases (GHGs) in the atmosphere causes global warming. Carbon dioxide (CO2) is one of the Major GHGs contributing around 60% towards global warming. Enhanced anthropogenic activities lead to higher atmospheric concentrations of GHGs and increase the global atmospheric temperature, having negative consequences for agriculture, food, and livelihood security. To combat these adverse environmental consequences, efforts should be made to mitigate climate change through carbon sequestration following a natural and sustainable approach. In this context, microalgae play an important role in carbon sequestration and climate change mitigation. They have higher carbon capture potential by converting the atmospheric CO2 into biomass through photosynthesis. Further, algal biomass could be used for the production of biofuels, biochar, and other value-added products, offering green alternatives. This study presents an analytical framework by linking biological CO2 fixation mechanisms with downstream valorization pathways and techno-economic evaluations. Microalgae utilization also has promising business opportunities in biofertilizers, biofuels, and carbon trading sectors. However, large-scale carbon sequestration by microalgae is limited due to high cultivation costs and a lack of suitable species for macro-level production. Therefore, optimization of the photosynthesis efficiency, extending the photoperiod, and employing genetic engineering methods such as gene editing, improvement of Calvin-Benson-cycle-key-enzymes, and altering light-harvesting complexes could enhance the carbon sequestration potential of microalgae. Specifically, the review analyses the microalgal carbon sequestration potential, influencing factors, and advanced enhancement techniques, and highlights the green utilization of algal biomass in sectors like biofertilizers, biofuel, nutraceuticals, and animal feed.