Mechanical characterization of algal cultivation systems for enhanced mass transfer

Mass transfer limitations pose a significant barrier to the industrial-scale deployment of algal cultivation systems, hindering efficient nutrient and gas exchange critical for applications in biofuel production, wastewater treatment, and carbon sequestration. This review aims to address this challenge by systematically evaluating mechanical strategies to enhance mass transfer, offering a novel integration of fluid dynamics, transport phenomena, and process engineering principles tailored to algal biotechnology. Unlike prior studies emphasizing biological or biochemical aspects, this review uniquely focuses on mechanical methods—stirring, bubbling, paddlewheel systems, and photobioreactor design—quantitatively assessing their impact on mass transfer optimization. Through mathematical modeling and empirical case studies, this review demonstrates that mechanical enhancements can increase mass transfer coefficients by 30–60 %, with innovative systems like rotating membranes reducing energy consumption by up to 90 % compared to conventional approaches. However, scale-dependent flow dynamics present persistent challenges, with transfer efficiency declining by 30–60 % from laboratory to industrial scales without adaptive design adjustments. This review bridges mechanical engineering and algal biotechnology, providing a robust analytical framework supported by predictive models and validated data to overcome mass transfer barriers. These findings underscore the potential for mechanically optimized systems to improve scalability and economic viability, advancing algae-based technologies toward sustainable industrial solutions. By addressing a critical research gap, this review offers actionable insights for researchers and engineers seeking to enhance algal productivity across diverse applications.