Granule Microstructure Design through Dry Compaction and Layer-wise Agglomeration

This dissertation investigated the influence of formulation and process design on the internal density structure and nutrient release of urea fertilizer as an alternate route to overcome nutrient leaching problems. The first part of the work focused on producing urea composites with different binders to optimize the formulation and composite microstructure. The second part of the study compared the microstructure and release kinetics of dry compacted and bilayer urea granules. Finally, the third part determined nitrate and ammonium leaching using disturbed soil column experiments. The optimization of granule microstructure and formulation design developed in this work yielded a 97.5 % reduction in the initial dissolution rate of modified urea granules compared to conventional urea fertilizer. Thus, the development of processing platforms focused on granule internal density distributions demonstrated a fundamental contribution to optimizing nutrient release properties.