Insights on industrial symbiosis applied to algal wastewater treatment: Decoupling remediation from valorization to achieve technological readiness.

Despite over six decades of research, microalgae-based wastewater treatment systems coupled to biomass valorization pathways remain stagnant at Technology Readiness Levels (TRL) of 4-6, failing to bridge the gap between pilot demonstrations and widespread commercialization. In this sense, an important, still underexplored structural problem is the persistent "dual-function" paradigm, which aims to simultaneously optimize environmental remediation and biomass valorization within a single reactor. This approach frequently generates operational incompatibilities, resulting in biomass with variable composition, potential contaminants, and limited market value, often suitable only for saturated, low-margin sectors (e.g., bioenergy and fertilizers). This paper argues that overcoming this bottleneck requires a fundamental shift in business models towards industrial symbiosis and process decoupling. Drawing on the principles of different Eco-Industrial Parks, the researchers propose a modular framework where wastewater treatment is optimized for regulatory compliance, while the resulting biomass and treated effluent serve as intermediate feedstocks for separate, specialized downstream biotechnological units. By decoupling these functions, facilities can resolve the trade-offs between hydraulic throughput and cultivation control. This study concludes that adopting such modular, circular economy-driven strategies is essential to improve economic feasibility, ensuring biomass quality, and finally advancing algal-based technologies toward mature commercial readiness (TRL 7-9).