Microalgae can turn wastewater from farms, factories and cities into biofuels, pigments and protein-rich food ingredients. A review published in Blue Biotechnology examines how algae-based phycoremediation strips nitrogen, phosphorus and heavy metals from effluent while producing biomass for biodiesel, biogas, astaxanthin, phycocyanin and other high-value products. The economics hinge on using wastewater as a free source of water and nutrients. Chlorella, Spirulina and other strains have shown strong nutrient removal in raceway ponds and photobioreactors, with bacterial partnerships improving treatment performance. Products like astaxanthin, with a market above 550 million USD per year, and fucoxanthin, priced up to 80,000 USD per kilogram, make the biorefinery model more viable than fuel-only production. Scale-up remains the bottleneck. Only about 15 microalgae strains are cultivated industrially, and high cultivation and harvesting costs still block wide deployment. The review points to genetic engineering, co-cultivation with bacteria and better pretreatment as the levers that could close the gap between lab results and commercial plants.
