Development of enhanced efficiency fertilizers: use of biopolymers as matrices for nutrient release

Author(s)

Lucas Luiz Messa

• Document type: Doctoral Thesis
• Press: Pirassununga.
• Institution: Universidade de São Paulo (USP). Faculdade de Zootecnica e Engenharia de Alimentos (FZE/BT)
• Defense date: 2022-02-23

Examining board members

Roselena Faez; André Ricardo Fajardo; Adriana de Campos Pastre; Luiz Antonio Pessan; Walter Ruggeri Waldman

• Advisor: Roselena Faez

Abstract

Enhanced efficiency fertilizers (EFFs) are systems capable of delaying the availability of plant nutritional content minimizing environmental pollution by reducing the loss of agricultural inputs during application. Recent research highlights the use of natural and biodegradable sources for EFFs development, particularly biopolymers, due to their intrinsic biodegradability, non-toxicity, renewability at relatively low cost. However, the use of biopolymers in the EFFs development commonly requires the addition of extra chemicals, including the incorporation of synthetic polymers, crosslinking agents, polymerization initiators, organic solvents, ionic liquids, etc., or complex and expensive production process impairing their application in agriculture. Therefore, the present work aimed to develop new biopolymer-based EEFs with a minimal additional chemical. For this, several experiments were carried out aiming to: i) develop EEFs based on chitosan and/or cellulose individually or in combination; ii) characterize their properties to find the optimal condition to synthesize EEFs; iii) propose solutions for the challenges encountered during the production process; iv) and elucidate the relationship between the chemical structure and release mechanisms. In short, cellulose was extracted from sugarcane bagasse using three well-established extraction methods, and then cellulosic derivatives were easily produced via acid hydrolysis and chemical phosphorylation for further use in the EEFs development. Combining solubilized chitosan, sulfated cellulose nanofibers (S-CNF), and NPK fertilizer, followed by spray-drying yielded microparticles with tunable release behavior depending on the fertilizer content and the concentration of S-CNF in composition, releasing a maximum of 48, 78, 96% of H2PO4-, NH4+ and K+ within 24 h, respectively. As a simpler strategy and without requiring additional chemicals, EEFs were produced from aqueous suspensions of phosphorylated cellulose loaded with NPK fertilizer followed by spray, freeze- or oven-drying. The different solid structures built, i.e., microparticles, three-dimensional porous solids, and films, had release behavior tunable by the ratio of anionic/cationic charges (cellulose-O-HPO3-/cation+) along with the drying methods, releasing 58, 60, 89% NH4+, K+, and H2PO4- ions released after 7 days. Thus, these approaches have shown to be effective in controlling the release properties of systems based on cellulose and/or chitosan to be biodegradable and renewable, increasing the potential for using biopolymers in the EEFs development. These results are of great importance and clearly indicate that the biopolymer materials developed allow significant improvements in technologies for the release of fertilizers. (AU)

• FAPESP's process: 17/03980-7 - Fertilizer-releasing biocomposites based on chitosan and cellulose obtained by spray drying technique
• Grantee: Lucas Luiz Messa
• Support Opportunities: Scholarships in Brazil - Doctorate (Direct)