Microalgae Cultivation in Wastewater: How Realistic Is This Approach for Value-Added Product Production?

Microalgae cultivation in wastewater is a production approach that combines wastewater treatment with biomass generation for various applications. This strategy aligns with the concept of a circular bioeconomy, which aims to transform waste into valuable resources. However, although this is true, this synergy’s potential bumps into obstacles that still limit the consolidation of the commercial cultivation of microalgae using wastewater. This review analyzed how close or far we are from achieving the successful integration of commercial microalgae cultivation with wastewater treatment for the production of value-added products. The analysis of the scientific literature highlighted that certain strains, such as Chlorella, Arthrospira, and Scenedesmus, can remove up to 90% of nitrogen and phosphorus from effluents while maintaining productivities of up to 45 g/m²/day. The techno-economic analyses presented here indicate that production costs range between 1.98 and 9.69 EUR/kg, depending on the effluent composition and biomass productivity. From an environmental perspective, replacing synthetic media with wastewater can significantly reduce input use, but the environmental impacts associated with energy consumption remain a challenge. This paper also discusses the technological readiness level (TRL), which currently remains between levels 4 and 6, concentrated on demonstration and pilot scales. By gathering and critically analyzing the current literature, this work seeks to answer how realistic and sustainable this integration is today.