Farmers apply nutrients in the form of chemical fertilizers and animal manure, which provide crops with the nitrogen (N) and phosphorus (P) necessary to grow and produce food. However, N and P are lost from the farm fields and negatively impact air and downstream water quality. Fertilizer application on land remains a major contributor to nonpoint nutrient pollution resulting in harmful algae blooms (HABs), and is expected to increase at an alarming rate in many regions. Mobility of N-fertilizers in the environment is critical. Urea, CO(NH2)2 is the most prominent N fertilizer accounting for ~60% of global nitrogen fertilizer use. It is produced via an ammonia (NH3) intermediate formed using the Haber process where hydrogen from natural gas is combined with N2 obtained from air under high temperature and pressure in the presence of a catalyst. The process is energy intensive and uses up to 1% of global energy and ~4% of natural gas. Approximately 40% of nitrogen fertilizer applied is not used by crops and lost to the environment, water and air, contributing to HABs unless exogenic organophosphorus compounds, such as urease enzyme inhibitors, are utilized. New approaches that provide for more sustainable nitrogen management in the environment are needed. The presented work will focus on in silico and experimental work to obtain N-efficient urea cocrystals via mechanochemical synthesis with abundant minerals, such as gypsum. In particular, DFT reactivity description based on chemical potential calculations of urea cocrystals under environmentally relevant conditions of relative humidity and temperature will be described as well as the time dependent synthesis and nutrient release properties of the ionic urea cocrystals. Additionally, in situ Raman spectroscopy single particle studies will reveal the propensity of urea react in the environment with various carboxylic acid facilitated by relative humidity.

Reducing agricultural nitrogen losses via mechanochemically synthesized urea cocrystals

ACS Fall 2021

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