Biobased Poly(3-hydroxybutyrate)/Starch/Cellulose Nanofibrils for Nutrients Coatings

The coating of nutrients to obtain enhanced efficiency fertilizer (EEF) is a common practice in agriculture. The material used as a matrix to coat or carry nutrients on the EEFs must be nutrient compatible, control the release, degrade after use, and be harmless to the environment. The present study aims at the preparation of a sustainable matrix based on natural and biodegradable polymers. First, cellulose nanofibrils (CNFs) have encapsulated potassium nitrate nutrients through spray drying, producing microparticles. Then, the polymeric matrix based on thermoplastic starch (TPS) and poly (3-hydroxybutyrate) (PHB) has coated the CNF-KNO3 microparticles by a melting process. The chemical and physical characterization and the biodegradation evaluation have ensured that the matrices are harmless to the environment. The nutrient release tests have evaluated the effectiveness of the matrix in postponing nutrient discharge. The matrix has first released the nutrient (first three days) and then started to degrade (the 7th day’s peak of biodegradation). All matrix formulations have shown to be biodegradable, and the EEF based on PHB, TPS, and CNF showed the highest levels of biodegradation. Characteristics attributed to CNFs and TPS effect on the degradation processes. Thereby, sustainable matrices for the enhanced efficiency fertilizers based on PHB, starch, and cellulose nanofibrils are feasible to be obtained and applied.