Valorization of Residual Algal Biomass for Natural Colorant Recovery and Textile Applications

Residual algal biomass generated by coastal accumulations, cultivation systems and industrial processing is a renewable feedstock for sustainable textile coloration. This paper reviews the recovery of chlorophylls, carotenoids and phycobiliproteins and evaluates their potential in dyeing, printing and functional finishing. Solvent selection is governed by pigment polarity: hydroalcoholic media are suitable for lipophilic chlorophylls and carotenoids, whereas buffered aqueous systems protect water-soluble phycobiliproteins. Literature data indicate that ultrasound, freeze-thaw treatment, pulsed electric fields and supercritical carbon dioxide can improve extraction performance while limiting thermal degradation. Reported textile applications include green, yellow, brown, red and blue shades on wool, cotton and silk, together with antioxidant activity and ultraviolet protection. The remaining exhausted biomass may subsequently be converted into biosorbents, biochar, biostimulants, biodegradable composites or biogas. A cascading biorefinery approach therefore supports waste prevention, resource efficiency and the development of lower-impact textile processes and creates a coherent basis for future experimental optimization.