Advanced technology and applications of small-scale, modular, and distributed biomass direct air capture systems

Direct Air Capture (DAC) technology, particularly utilizing microalgae, has gained significant attention as a promising approach to mitigating atmospheric CO₂ levels. Small-scale, modular, and distributed DAC systems offer notable advantages in scalability and adaptability, enabling flexible deployment across diverse environments while supporting sustainable bio-product generation, making them a vital pathway toward carbon neutrality goals. This review aims to address three fundamental scientific issues: (a) enhancing the efficiency, scalability, and durability of CO₂ capture processes from low-concentration air, (b) optimizing CO₂ fixation methods to overcome challenges such as slow reaction kinetics, high energy demands, and system stability, and (c) achieving efficient integration of capture and fixation processes to ensure energy efficiency and resource sustainability. The review provides a comprehensive analysis of various DAC technologies, evaluating their advantages and limitations to establish a foundation for an in-depth discussion of microalgae-based DAC systems. Key technical challenges, including CO₂ dissolution, concentration, and transfer, are thoroughly examined, alongside recent advancements in photobioreactor design, gas-liquid mass transfer enhancements, and process optimization strategies. By synthesizing current research progress and commercial implementation efforts, this work aims to identify pathways for scaling up microalgae DAC technologies while addressing technical and economic bottlenecks. Finally, it evaluates the prospects and challenges of commercializing DAC and microalgae DAC technologies, drawing insights from current applications and commercial projects. This work aims to provide a comprehensive analysis of the technical challenges, optimization strategies, and future potential of DAC technologies, offering insights to guide their practical implementation and scalability.