Avaliação do emprego de resíduo agroindustrial como revestimento para ureia na obtenção de um fertilizante de eficiência aprimorada

Abstract

Due to the increasing population, and consequently, the increasing demand for food, agricultural alternatives are needed to achieve high productivity and sustainability. The use of fertilizers with improved efficiency allows nutrients to be released in synchrony with crop needs, without the need for intensive fertilization and preventing nutrient saturation in the soil. In view of the great economic and environmental interest in the integral utilization of lignocellulosic materials, this work aimed the evaluation of a controlled, release coating having grape bagasse as matrix, for urea. The grape bagasse was treated by different processes, such as steam explosion autohydrolysis and washing with deionized water to remove soluble compounds. The treatment steps made it possible to clean and de-structure the grape bagasse in natura so that the fibers of the biomass were favorable for the impregnation of urea. The steam explosion occurred at 175 ºC and 7.6 bar, with a retention time of 5 min. The washes occurred in two cycles of 2 h each, at a temperature of 80 ºC, using deionized water as solvent at a ratio of 1:40 m/v. After treatment, the biomass was dried and pulverized. Then, the improved efficiency fertilizer was produced by impregnating urea into the treated grape bagasse at different concentrations (30, 40 and 50 % m/m). The characterization of each step was performed through Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA) and differential thermal analysis (DTG), and finally, the controlled release tests in aqueous medium. With the analyses, it was possible to prove the presence of the unstructured lignocellulosic macromolecules in the treated grape bagasse, and also that the treatments were efficient, making the bagasse with a high reduction of soluble compounds. Through the controlled release tests, it was confirmed that the fertilizer of improved efficiency reached the objective of delaying the solubilization of urea, since the test performed with 10 g of pure urea, lasted for 2 min and 33 s, having 100% of solubilized urea, while the fertilizers of improved efficiency spent 12 h of exposure having the maximum of 54.737% of urea solubilization, where the remainder was incorporated into the biomass. Even without having presented a standard solubilization profile, the results obtained are significant for the production process of controlled release fertilizers, as they meet the necessary requirements. [resumo fornecido pelo autor]