<p>The continuous increase in atmospheric carbon dioxide (CO₂) concentrations due to human activities has intensified the need for efficient carbon capture strategies. Microalgae-based biofixation is considered a promising approach due to its high growth rates and carbon assimilation capacity; however, the effect of different CO₂ supply strategies on cultivation performance is not yet fully understood. This study evaluates the impact of batch and continuous carbon dioxide supplementation on the growth and biofixation efficiency of <i>Arthrospira platensis</i> cultivated in Zarrouk medium using two photobioreactor systems. In the continuous system, a carbon dioxide flow rate of 10 mL/min resulted in the highest specific growth rate (0.2 day^− 1) and biomass productivity (0.27&#xa0;g L^− 1 day^− 1), indicating optimal cultivation conditions. In the batch system, carbon dioxide removal efficiency reached up to 97.8% under elevated carbon dioxide concentrations, demonstrating the high carbon uptake capacity of the strain. In addition, controlled carbon dioxide supply contributed to maintaining the pH within the optimal alkaline range, supporting stable growth conditions. The results highlight the critical role of carbon dioxide delivery strategy in optimizing cyanobacterial growth and biofixation efficiency, supporting the potential application of <i>Arthrospira platensis</i> in scalable carbon capture and biofuel production systems.</p> Graphical abstract <p></p>