Energy Valorization of Water Hyacinth: Effect of Torrefaction on Pellet Quality for a Circular Bioeconomy

Water hyacinth (Eichhornia crassipes), one of the most aggressive invasive aquatic species in tropical ecosystems, poses severe ecological and socio-economic challenges. This study investigates its valorization as a solid biofuel through pelletization and torrefaction, contributing to circular bioeconomy strategies. Pellets (6 mm) produced from leaf biomass without binders were subjected to torrefaction at 230°C, 260°C, and 290°C for 30 min. Their physical, chemical, and energetic properties were evaluated according to ISO 17225-6. Results demonstrate that torrefaction significantly enhances fuel quality, reducing moisture content by up to 68.7% and increasing fixed carbon content, while improving hydrophobicity and storage performance. The highest heating value reached 17.23 MJ/kg at 290°C (+6.08% compared to untreated pellets). Although bulk density and mechanical durability decreased at higher temperatures, pellets torrefied at 230°C achieved optimal compliance with durability standards, indicating a trade-off between mechanical integrity and energy performance. These findings confirm that water hyacinth can be effectively transformed into a viable solid biofuel, offering a dual environmental benefit: renewable energy production and invasive species control. The study provides a relevant framework for integrating problematic aquatic biomass into sustainable energy systems in tropical regions.