Algae Valorization Pathways and Their Potential Relevance to Nutrient Recovery in Eutrophic Waters

Eutrophication driven by excess nitrogen (N) and phosphorus (P) remains a pervasive global water-quality challenge, necessitating scalable nutrient recovery strategies that extend beyond conventional treatment approaches. This review synthesizes the emerging literature on algae-based systems as dual-purpose platforms for nutrient mitigation and biomass valorization. We examine systems including seaweed bioextraction, integrated multi-trophic aquaculture, algal turf scrubbers, and wastewater phycoremediation, while highlighting reported nutrient removal efficiencies and operational constraints. Beyond remediation, the spectrum of valorization pathways considered ranges from biofertilizers, feed, bioenergy, and materials to nutraceuticals, cosmetics, biomedical materials, biomanufacturing, and methane-mitigating livestock additives. The review emphasizes the economic and logistical challenges linking remediation-scale biomass production to commercial markets, including the contamination risk, processing intensity, regulatory classification, and scale mismatch. We propose an integrated remediation–valorization framework to guide research, policy, and industry toward nutrient-circular, economically viable restoration strategies.