Technical and environmental assessment of coated urea production with a natural polymeric suspension in spouted bed to reduce nitrogen losses

Abstract

Urea is the most used nitrogen fertilizer in the world, but should be supplied to the plants in a controlled way to make it as efficient as possible. Otherwise, nitrogen losses due to volatilization and leaching can reach up to 70%. The production of coated urea with slow-release polymers can be a good alternative not just to reduce the nitrogen losses but also to avoid the greenhouse gases emissions related to the high consumption of this fertilizer. Therefore, the aim of this study is to evaluate the technical and environmental aspects of coated urea production in a spouted bed to control the nitrogen volatilization. The influence of the operating conditions in the coating performance was evaluated using a central composite rotational design and the environmental performance was determined using a life cycle assessment. The coating performance results showed that coated urea particle growth ranged from 0.8 to 4.4%, the coating efficiency presented results between 17 and 47% and the nitrogen volatilization reduction was significant (11–50%). The highest nitrogen volatilization reduction was obtained for suspension flow rate equal to 15 mL/min and air temperature equal to 85 °C. The daily volatilized nitrogen release profile and the microscopic analysis showed that the coating film was effective in controlling nitrogen release contained within the particle. The environmental analyses demonstrated that coated urea had a lower impact than uncoated, for most of the impact categories under study, indicating that the coating process is also appropriate to reduce the environmental impacts of urea fertilization.