Enhancing CO2 Fixation in Microalgal Systems: Mechanistic Insights and Bioreactor Strategies.

Abstract

Microalgae are small, single-celled, or simple multicellular organisms that contain Chlorophyll a, allowing them to efficiently convert CO₂ and water into organic matter through photosynthesis. They are valuable in producing a range of products such as biofuels, food, pharmaceuticals, and cosmetics, making them economically and environmentally significant. Currently, CO₂ is delivered to microalgae cultivation systems mainly through aeration with CO₂-enriched gases. However, this method demonstrates limited CO₂ absorption efficiency (13-20%), which reduces carbon utilization effectiveness and significantly increases carbon-source expenditure. To overcome these challenges, innovative CO₂ supplementation technologies have been introduced, raising CO₂ utilization rates to over 50%, accelerating microalgae growth, and reducing cultivation costs. This review first categorizes CO₂ supplementation technologies used in photobioreactor systems, focusing on different mechanisms for enhancing CO₂ mass transfer. It then evaluates the effectiveness of these technologies and explores their potential for scaling up. Among these strategies, membrane-based CO₂ delivery systems and the incorporation of CO₂ absorption enhancers have shown the highest efficiency in boosting CO₂ mass transfer and microalgae productivity. Future efforts should focus on integrating these methods into large-scale photobioreactor systems to optimize cost-effective, sustainable production.