Microalgae production at industrial scale: modelling and control challenges

The 21st century society faces significant sustain- ability challenges, including climate change, resource depletion, and environmental degradation. Microalgae have emerged as a versatile and sustainable solution to mitigate these problems. The microalgae production process involves harnessing their ability to convert sunlight, carbon dioxide, and nutrients (contaminants in wastewater media or agriculture effluents) into valuable biomass through photosynthesis, thus providing a synergy between biomass production and environmental reme- diation. When microalgae are produced, the culture conditions, including temperature, light intensity, nutrient concentration, dissolved oxygen, and pH, are critical factors that must be carefully controlled to ensure optimal microalgae growth. The growth dynamics of microalgae is influenced by a multitude of interacting factors that, together with the biological nature of microalgae and the variability of weather conditions, pose a significant barrier to the implementation of effective control algorithms. This tutorial paper summarizes the results of more than 20 years of experience working in the scale-up and development of modeling, control, and optimization methods for microalgae production systems. Theoretical and experimental results at industrial scale will be presented to show the potential of microalgae production systems and how control engineering solutions can contribute to make them more competitive in the market for bioproduct generation and wastewater regeneration. Moreover, ongoing projects, such as REALM, will be presented and summarized to show novel applications of microalgae application and how the control automatic field plays a fundamental role for their optimization.