Green recovery of cellulose from Posidonia oceanica leaf deposits: A sustainable biomass source

Leaves deposits of Posidonia oceanica on the beaches cause some inconveniences especially for the tourism economy of the coastal cities. Developing strategies to remove beached seagrass while adding value to this biomass represents a promising option for municipalities, aligning with circular economy principles. In this study, Posidonia oceanica leaf deposits were used for cellulose extraction through an eco-friendly process involving alkaline delignification, ethanolic extraction, and bleaching in hydrogen peroxide (H₂O₂) aqueous solution. The effects of the bleaching solution’s acidity and the inversion of bleaching/delignification phases on recovery efficiency, quality, and morphology of cellulose were evaluated. For comparison, a cascaded extraction treatment involving a harsh chemical (i.e., sodium chlorite ‒ NaClO2) as a bleaching agent was also performed. The yield and morphological features of the extracted cellulose were barely affected by the treatment method. XRD and NMR analyses demonstrated that bleaching with H₂O₂ increased the crystallinity index of cellulose compared to the chlorinated counterpart of ~ 20%, although slightly weaker lignin removal performance was observed from compositional analyses. Overall, these results indicate that H₂O₂ can serve as a green alternative to chlorine-based agents for chemically treating seaweed biomass, such as Posidonia oceanica leaves, to recover cellulose for potential applications in various sectors, including the food industry.