Design and manufacture of high nitrogen content sulfurcontaining fertilizers is of crucial importance in sustainable food and energy crop production. The availability of large elemental sulfur amounts in oil refining and natural gas processing facilities, in combination with decreasing sulfur deposition into soil from natural and anthropogenic sources in a bioavailable sulfate form, calls for innovative engineering solutions that bridge this gap via sustainable sulfur processing. Diurea sulfate-based liquid and compound solid granulated fertilizers were synthesized in this work, and their resulting physicochemical properties were determined. First, phase compositional information on the 2CO(NH 2 ) 2 ·H 2 SO 4 −CO(NH 2 ) 2 −H 2 O ternary system was measured, and high nitrogen content, ∼15:1 N:S ratio liquid fertilizer grades, were established. Next, diurea sulfate granulation experiments using (i) dolomite, (ii) byproduct material after the phosphoric acid extractive production, CaSO 4 ·0.5H 2 O, and (iii) dolomite combined with diammonium phosphate, (NH 4 ) 2 HPO 4 , and potassium chloride, KCl, were performed. Using diurea sulfate, 16−16−16−5.5(S)−0.4(MgO)− 0.6(CaO) compound granulated fertilizers were successfully obtained, and time-resolved changes in their crystalline phase composition during granule curing were monitored using XRD. The granule crushing strength measured increased to 3.800 MPa within the 30 day storage thus resulting in high quality fertilizer material.

Design and use of the adjustable N:P 2 O 5 ratio fertilizers is crucial in proper nutrient management if sustainable phosphorus use is to be ensured. Overfertilization with phosphorus can lead to its fixation in soil, as well as the unwanted environmental phenomena, such as eutrophication. Urea phosphate, CO(NH 2 ) 2 •H 3 PO 4 , based liquid fertilizers were synthesized in this work, and their resulting physicochemical properties were determined. For this purpose, phase composition information on the CO(NH 2 ) 2 •H 3 PO 4 −CO(NH 2 ) 2 −H 2 O ternary system was analyzed, and critical points on the polytherm were determined. Liquid fertilizer compositions were determined and their corresponding physicochemical properties established. Raman spectroscopy showed that CO(NH 2 ) 2 •H 3 PO 4 partially retains its strong bonding interactions between both molecular adducts in aqueous solutions suggesting their improved nitrogen management efficiency in soils. Effect of these acidic pH fertilizer solutions on the pH of soil was determined and was found negligible. The potential of these fertilizers for reducing the loss of nitrogen from the wet soil is also discussed.