Posidonia oceanica beach casts revalorization through high-boiling point organosolv solvents

The accumulation of marine plants like Posidonia oceanica on beaches poses ecological challenges but also represents a renewable biomass resource. This study explores the potential of Posidonia oceanica as an alternative source of cellulose and lignin through an organosolv process, using non-conventional high-boiling point solvents such as ethyleneglycol, diethyleneglycol, ethanolamine and diethanolamine. Three operating conditions were tested: minimum (60 % solvent concentration, 160°C), medium (70 % solvent concentration, 170°C), and maximum (80 % solvent concentration, 180°C). The leaves treated with amine-based solvents under maximum conditions exhibited high cellulose purity, viscosity, and delignification, while glycolic solvents produced pulps with higher residual lignin, suitable for high-strength applications like corrugated cardboard. Compared to other raw materials, Posidonia oceanica pulps displayed greater viscosity and Kappa number values, positioning it as a competitive cellulose source. The alkanolamine treatments effectively fractionated the biomass into a cellulose-rich pulp and a lignin-rich black liquor, demonstrating the feasibility of utilizing Posidonia oceanica in a biorefinery process. The study highlights the ecological and economic advantages of utilizing marine biomass in a circular economy, reducing reliance on wood-based resources and mitigating deforestation, while providing value-added products like cellulose and lignin. • Organosolv high-boiling point solvents fractionates Posidonia oceanica residues into a cellulose-rich pulp and lignin liquor. • Pulp treated with alkanolamine solvents showed higher cellulose purity and delignification than glycolic solvents. • P. oceanica is as a competitive, renewable biomass source of cellulose and lignin, supporting a circular bioeconomy.