Spray-dried cellulose nanofibrils microparticles as a vehicle for enhanced efficiency fertilizers

This paper reports the role of cellulose and cellulose nanofibrils (CNFs) as a material to encapsulate nutrients applied in agriculture. Enhanced efficiency fertilizers have been a constant subject during the past decades to achieve slow and controlled release of the nutrients and decrease the environmental impacts caused by traditional fertilization. For this reason, it is important to use bio-based and biodegradable materials as a delivery method capable of covering the nutrients, retarding their solubility and availability in the environment, and avoiding the coating residue in the soil afterward. Here, we report the use of cellulose and cellulose nanofibrils to encapsulate nitrogen- and potassium-based nutrients. The nutrient was dissolved in a cellulose suspension and dried in a Mini Spray Dryer Buchi B-290. The materials obtained were classified as microspheres, microcapsules and tablets. They were characterized by morphology, physical and chemical structures, thermal properties, and release mechanisms. The nutrient availability in the environment was reduced through time for the microcapsules compared to the non-encapsulated and the microspheres. It displayed a reduction from 100 to 97.5% and then to 65.5% (from the non-encapsulated KNO₃ to microsphere then to microcapsule, respectively) after 10 min of water contact. In addition, from 65.5 to 33% for tablet showing the superficial contact effect. The nutrient delivery depends on both the diffusional transport and the relaxational properties of the polymeric chain according to the kinetics mechanism. CNFs played an important role in the nutrient release behavior, which is of interest in the development of enhanced efficiency fertilizers.