Challenges and opportunities in the development of industrial processes based on microalgae

Abstract of the oral presentation made at the IV Brazilian Congress of Microalgae Energy Potential & RENUWAL, 2024, Nata, Brasil.

Microalgae-related industrial processes are still an emerging economic sector. Thus, although there is a large list of microalgae-related products and services already commercial, still the potential of this sector has not been fully exploited. The current market of microalgae-related processes will be revised. Thus, the most conventional products and processes are related to the production of nutraceuticals, food additives and foods. New processes are related to the production of feed/aquafeed and agriculture (biostimulants/biopesticides). Some examples of wastewater treatment processes have been also developed in the last years. The most challenging applications are those related to materials and biofuels. The reasons behind the use of microalgae in these sectors will be reviewed. Moreover, the most relevant advances in the scaleup of microalgae production systems, especially those based on the use of raceway reactors, are reviewed. They include (i) the knowledge of the biological systems, (ii) the improvement of the design and operation of reactors, (iii) the enhancement of harvesting/processing technologies, and (iv) the implementation of advanced control systems including artificial intelligence-based tools. Concerning the biological systems, the models recently developed provide a complete overview of phenomena taking place, including the influence of culture conditions, the presence of different microorganisms, and the role of parasites (Sánchez Zurano et al., 2021). These models allow to determine the most efficient strategies to optimize their performance as a function of these variables, including the prevention of crashes. Concerning design, the use of computational fluid dynamics allows building units up to 1 ha, while minimizing energy consumption below 5 W/m³, and improving the light utilization efficiency by 25%(Inostroza et al., 2023). In the case of temperature, new heat exchangers are designed to envisage the opportunity for controlling this variable including in large-scale facilities(Rodríguez-Miranda et al., 2021). The optimization of mass transfer capacity allows for the prevention excess of dissolved oxygen concentrations at the same time optimizing the use of CO₂ for pH control, and allowing the direct capture of CO₂ from the air(Barceló-Villalobos et al., 2022). The use of membranes is a major advance for harvesting/processing. Non-pressure membranes allow to pre-concentrate of the cultures at minimum cost/energy consumption while obtaining cell-free supernatants to be recirculated or for safe disposal, while Low-pressure membranes allow to fractionate of the compounds of microalgae biomass without using solvents to achieve sustainable processes with zero emissions. However, the most revolutionary improvement is the use of advanced control systems that allow for optimisation of the performance of the cultures/systems as a function of target function and environmental conditions. Low-level control strategies allow for the optimization of resources such as energy, nutrients, water, CO₂, etc. High-level control strategies based on artificial intelligence are capable of adjusting the operation conditions to optimise the performance of the overall system. All these advances have been already demonstrated and now are applied in industrial facilities, with examples of those applications being provided.