Fertilizer caking issues: a focus on analytical methods used to characterize coatings and to assess caking phenomena

This paper presents a critical review of analytical methods used to characterize liquid coating agents in granular fertilizers and evaluate granular fertilizer caking. Various techniques applied to analyse the physico-chemical properties of coatings have been detailed. A panoply of techniques including chromatographic methods like gas chromatography-mass spectrometry (GC-MS) and high-performance liquid chromatography (HPLC), and functional analysis techniques such as Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (NMR) have been reviewed. Furthermore, physical methods for characterising coating agents have been discussed, including thermogravimetric analysis (TGA), differential thermal analysis (DTA), and measurements of viscosity, density, and contact angle. Additionally, the paper reviews fertilizer caking evaluation methods, such as accelerated compression tests, bag stacking tests, and centrifugation methods, with emerging techniques like the spring method. This review enhances understanding of anticaking agent control in fertilizer production and highlights the current caking evaluation techniques, their limitations and the need for their improvements.