Environmentally Friendly Slow-Release Urea Fertilizers Based on Waste Frying Oil for Sustained Nutrient Release

Abstract

Novel biobased polyurethane (PU) was synthesized by using waste frying oil-based polyol (WFOP) and isocyanate for slow-release fertilizers (SRFs). Epoxy resin (EP) was used to modify PU to synthesize the interpenetrating network (IPN) for improving the properties of the coating film. Nine polymer-coated nitrogen (N) fertilizers were prepared from these composite coating materials. The N release characteristics of the PU-coated urea (PCU) in water and soil were determined. Degradation behavior of coatings in the soil was evaluated. Results showed that 20% EP in the coating increased the cross-linking density by 77.9%, reduced the coating porosity by 28%, and thus slowed the nutrient release from the PCU significantly. Because of its compact structure, the water absorption rate of the EP-modified PCU shell was slower than that of the unmodified ones. All the PCUs, especially the EP-modified ones, showed excellent slow N release behaviors. In addition, the biopolymers derived from waste frying oil also displayed good biodegradability in the soil environment. Findings from this work indicated that the slow release and environmentally friendly PCUs have great potential for applications in horticulture and agriculture.

A Biochar-Based Route for Environmentally Friendly Controlled Release of Nitrogen: Urea-Loaded Biochar and Bentonite Composite

“…Nitrogen fertilizer is essential for maintaining the soil fertility and plant growth, but nitrate leaching, ammonia volatilisation, and nitrous oxide emissions cause high N losses, resulting in low efficiency of N utilisation, high economic costs, and environmental pollution 1–4 . Previous studies have paid much attention to use polymers as coating materials for achieving controlled- release of urea 5 . Although the coating materials can retard the nutrient release rates, the cost, nondegradability, and nonrenewability of such coating materials lead to negative environmental and economic impacts 6 .…”

Properties of Coated Controlled Release Diammonium Phosphate Fertilizers Prepared with the Use of Bio‐based Amino Oil

“…with 9.0 wt % PU resulted in around 70% phosphorus release after about 500 h). Novel biobased polyurethane (PU) was synthesized by using waste frying oil-based polyol (WFOP) (Liu et al, 2017) or waste palm oil-based polyol (WPOP) (Liu et al, 2018) and isocyanate for SRFs. In the case of WFOP, epoxy resin diglycidyl ether of bisphenol A (EP) was used to modify the coating in order to improve the properties of the film.…”

Environmentally Friendly Fertilizers Based on Starch Superabsorbents

“…In both cases, the behavior observed in the curves that represent the release kinetics consists of three zones or stages, which give it a characteristic “S” shape. A first stage where the fertilizer is slowly released, followed by a rapid release zone where the greatest amount of fertilizer is released in all materials and finally, an area where the release reaches a constant value [18,43]. The rapid increase in KNO 3 and NH 4 NO 3 between t = 0 and t = 0.5 h is due to the occurrence of a burst effect due to the amount of fertilizer deposited on the surface of the charged hydrogel [8].…”

“…The rapid increase in KNO 3 and NH 4 NO 3 between t = 0 and t = 0.5 h is due to the occurrence of a burst effect due to the amount of fertilizer deposited on the surface of the charged hydrogel [8]. The increase in the release rate in the second zone is attributed to the progressive expansion of the polymer matrix due to its swelling [43]. This behavior is accentuated with the increase in the initial concentration of fertilizer loaded (see Figure 10).…”