Microalgae have emerged as a promising solution for both energy production and environmental remediation. A recent review published in the Journal of Environmental Management explores the potential of using aquaculture wastewater effluents to cultivate microalgae, offering a sustainable pathway for biofuel production and nutrient recovery.
Scientists from “Dunarea de Jos” University Galati, Nantes University Saint-Nazaire, and “Ştefan Cel Mare” University of Suceava identified, centralized, and provided comprehensive information on the key technological and technical factors influencing the growth process of different microalgae species in aquaculture wastewater.
The promise of microalgae
Microalgae can convert sunlight, carbon dioxide, and nutrients into biomass. This biomass is rich in lipids, proteins, and carbohydrates, making it a valuable resource for biofuel production, including biodiesel, bioethanol, and biomethane. Unlike traditional crops, microalgae can achieve higher annual yields and are considered third-generation biofuels, which are more sustainable and environmentally friendly.
One of the most significant advantages of microalgae is their ability to mitigate CO₂ emissions. According to recent studies, 1 kg of microalgae biomass can remove approximately 1.8 kg of CO₂ from the atmosphere. This makes microalgae cultivation a dual-purpose solution: reducing greenhouse gases while producing renewable energy.
Aquaculture wastewater: A nutrient-rich resource
Aquaculture generates large amounts of wastewater rich in nitrogen compounds, phosphates, and dissolved organic carbon. If not properly managed, these nutrients can lead to environmental issues such as eutrophication, which degrades water quality and harms aquatic ecosystems.
Rather than viewing aquaculture wastewater as waste, researchers now consider it a valuable resource for microalgae cultivation. Wastewater provides an ideal growth medium for microalgae, promoting circular economy principles and nutrient recovery. By utilizing aquaculture wastewater, microalgae can effectively remove nutrients from the water, reducing pollution while producing biomass for biofuel production.
Technological advances in microalgae cultivation
The scientific review highlights several technological and technical factors influencing microalgae growth in aquaculture wastewater. Key parameters include pH, temperature, light intensity, and nutrient composition. Among these, pH control is particularly crucial as it directly affects microalgae metabolism and CO₂ availability.
Most microalgae production systems utilize photobioreactors (PBRs), which are closed systems that allow precise control over growth conditions. Compared to open systems like raceway ponds, PBRs can achieve significantly higher biomass yields, ranging from 30 to 100 g/L. This is due to their ability to optimize growth conditions and implement advanced control strategies.
Control strategies for optimal growth
One of the main challenges in microalgae cultivation is maintaining optimal growth conditions. The scientific review identifies pH control as a critical factor, with most control strategies focusing on CO₂ injection to regulate pH levels. Advanced control strategies, such as Proportional-Integral (PI) controllers and Event-Based Generalized Predictive Control (GPC), have been developed to improve CO₂ utilization and reduce operational costs.
For example, a study by Rodríguez-Torres et al. (2021) demonstrated that using a PI controller for pH regulation in thin-layer recirculating and raceway filtration systems improved system performance and reduced CO₂ consumption. Similarly, Fernández et al. (2010) proposed a control strategy that combines a PI controller with a feedforward compensator to account for solar radiation, further enhancing pH control efficiency.
The role of automation and AI
As the microalgae industry grows, the need for automation and advanced control systems is becoming increasingly important. Automation can help optimize growth conditions, reduce operational costs, and improve the overall efficiency of microalgae production systems. For instance, AI-based algorithms and machine learning can be used to monitor water quality and biomass growth in real time, providing valuable insights for process optimization.
The review also highlights the importance of scaling up microalgae production from laboratory research to industrial applications. While pilot studies have shown promising results, large-scale production faces challenges such as high operational costs, inconsistent wastewater composition, and the need for specialized personnel. Addressing these challenges will require continued research and development, as well as investment in advanced technologies.
Future trends and opportunities
A bibliometric analysis included in the review reveals a growing interest in Integrated Multi-Trophic Aquaculture (IMTA) systems, which combine fish farming with microalgae cultivation. These systems not only offer a sustainable solution for wastewater treatment but also generate additional revenue streams through biofuel production and high-value microalgae-based products.
Looking ahead, the review suggests that research should focus on the development of decision-support tools and AI-based forecasting algorithms to optimize microalgae production. By leveraging historical data and advanced analytics, researchers can identify trends and opportunities to improve the efficiency and sustainability of microalgae cultivation.
Conclusion
Utilizing aquaculture wastewater for microalgae cultivation represents a promising approach to addressing some of the most pressing environmental and energy challenges of our time. By transforming waste into valuable resources, this innovative technology aligns with the principles of circular economy and sustainable development.
Contact
Ștefan-Mihai Petrea
Department of Food Science, Food Engineering, Biotechnologies and Aquaculture, “Dunarea de Jos” University Galati
800008, Galati, Romania.
Email: stefan.petrea@ugal.ro
Reference (open access)
Simionov, I., Barbu, M., Vasiliev, I., Condrachi, L., Titica, M., Ifrim, G., Cristea, D., Nuță, F. M., & Petrea, Ș. (2025). Prospective technical and technological insights into microalgae production using aquaculture wastewater effluents. Journal of Environmental Management, 377, 124537. https://doi.org/10.1016/j.jenvman.2025.124537
