certain negative environmental impacts. 45−47 Overall, decisive action is needed to ensure safe and sufficient N fertilizer supply under turbulent times, and sustainable chemistry and engineering have to play a significant role. This is substantiated by the fact that the population is projected to increase to ∼9.8 billion by 2050, while the N-rich protein diet is also expected to increase as 99% of the population growth from 2020 to 2050 is projected to occur in Asia and Africa, currently on a low-protein diet. 48 We hope that this editorial will stimulate and seed creative thinking in obtaining sustainable synthesis routes of efficient and stable N fertilizers from widely available waste, rather than utilizing natural gas.

Ammonium carbonates are a group of fertilizer materials that include ammonium bicarbonate, ammonium carbonate hydrate, and ammonium carbamate. They can be synthesized from diverse nutrient-bearing liquid waste streams but are unstable in a moist environment. While extensively utilized several decades ago, their use gradually decreased in favor of large-scale, facility-synthesized urea fertilizers. The emergence of sustainable agriculture, however, necessitates the recovery and reuse of nutrients using conventional feedstocks, such as natural gas and air-derived nitrogen, and nutrient-containing biogenic waste streams. To this extent, anaerobic digestion liquid presents a convenient source of solid nitrogen and carbon to produce solid fertilizers, since no significant chemical transformations are needed as nitrogen is already present as an ammonium ion. This review describes detailed examples of such feedstocks and the methods required to concentrate and crystallize solid ammonium carbonates. The technologies currently proposed or utilized to stabilize ammonium carbonate materials in the environment are described in detail. Finally, the agricultural efficiency of these materials as nitrogen and carbon source is also described.

Phosphate minerals play an important role in the natural cycle of phosphorous, both in the solid form used in agricultural applications and as aerosolized apatite mineral particles. Mineral surface aging processes, such as organic acid processing, have a significant effect on the phosphate particle physicochemical properties, particularly, their hygroscopicity. In this study, hydroxyapatite was used as a model for low solubility apatite phosphate minerals and subjected to acid processing with formic acid (FA) vapor to simulate the atmospheric processing caused by volatile organic compounds present in the troposphere. Hydroxyapatite particles were shown to react with the FA vapor to form Ca(HCOO) 2 on the particle surface, resulting in a heterogeneous microparticle surface, as evidenced by spatially resolved Raman spectroscopy. Due to the more soluble nature of the Ca(HCOO) 2 formed on the surface, the hygroscopicity of the acid-processed particle surfaces was shown to increase using dynamic vapor sorption studies. The maximum water uptake at 95% RH was shown to increase from 0.4 to 0.82% and 3.26% after 24 and 48 h of laboratory acid exposure, respectively. Conventional adsorption models, including Brunauer−Emmett−Teller and Freundlich, were used to fit the adsorption data. The heat of sorption values of the 48 h acid-exposed sample was shown to converge to the heat of condensation of water at higher coverage values compared to untreated and 24 h processed hydroxyapatite.

Urea cocrystal materials have recently emerged as high nitrogen (N) content fertilizers with low solubility capable of minimizing N loss and improving their use efficiency. However, their effects on crop productivity and N2O emissions remain underexplored. A greenhouse study was designed to evaluate sorghum (Sorghum bicolor (L.) Moench) yield, N uptake, and N2O emissions under six N treatments: C0 (without fertilizer), UR100 (urea), UC100 (CaSO4⋅4urea cocrystal) at 150 kg N ha−1, and CaSO4⋅4urea cocrystal at 40%, 70%, and 130% of 150 kg N ha−1 (UC40, UC70, and UC130, respectively). The results demonstrated that UR100, UC100, and UC130 had 51.4%, 87.5%, and 91.5% greater grain yields than the control. The soil nitrate and sulfur concentration, N uptake, and use efficiency were the greatest in UC130, while UR100 had significantly greater N2O loss within the first week of N application than the control and all the urea cocrystal treatments. UC130 minimized the rapid N loss in the environment as N2O emissions shortly after fertilizer application. Results of this study suggest the positive role of urea cocrystal in providing a balanced N supply and increasing crop yield in a more environmentally friendly way than urea alone. It could be good alternative fertilizer to minimize N loss as N2O emissions and significantly increase the N use efficiency in sorghum.

A tandem strategy that recovers NH4+ and PO43- nutrients from simulated wastewater in a solid form after the Fenton oxidation of emerging organic contaminants was developed. Mesoporous Cu-MgO nanoparticles were...