Charged-cellulose nanofibrils as a nutrient carrier in biodegradable polymers for enhanced efficiency fertilizers

An enhanced efficiency fertilizer (EEF) is essential for sustainable agriculture, and here, we evaluated cellulose nanofibrils (CNF) as a nutrient carrier dispersed in biodegradable polymeric matrices. CNF were functionalized with negative (CNF^-) and positive (CNF⁺) charges to improve (i) the CNF-nutrient and (ii) the CNF-polymeric matrix interactions. The CNF encapsulated the KNO₃ nutrient by spray drying (microcapsules) and then inserted into a poly (hydroxybutyrate)/starch-based matrix by melt-compounding (tablets). These materials were morphologically, structurally, and thermally characterized before and after biodegradation. Nutrient release profiles showed the microcapsules released the nutrients for up to 1 h, while the tablets did for 8 h in water and over 80 days in soil. Tablets with CNF^- released NO₃^- faster than K⁺, and those with CNF⁺ behaved inversely. Besides, the biodegradation efficiencies were up to 75 % in 120 days. The CNF charges affected nutrient release and the matrix biodegradation, ensuring the matrices were harmless to the environment.