Low-cost slow-release fertilizers fabricated by hot-melt encapsulation from biomass waxes

Despite the widespread use of polymer-coated slow-release fertilizers (SRFs), conventional coating techniques often suffer from complex processes, long production times, and high cost. To address these limitations, this study develops a novel hot-melt encapsulation strategy using biomass waxes as coating materials. By modulating the cooling rate, the crystallization behavior and crystallinity of the four waxes (i.e., paraffin wax, beeswax, rice bran wax, and carnauba wax) can be effectively regulated, which enhances surface roughness and hydrophobicity on the coating surface, thereby extending the nutrient release duration. The results show that the carnauba wax exhibits outstanding crystallization capability, achieving a crystallinity of 52.77% at a cooling rate of 1 °C min −1 . This favorable crystallization behavior leads to significantly increased surface roughness and a high water contact angle of 125.2°. The optimized carnauba wax-coated SRF with 9% coating content attains a nutrient release longevity of 56 days. Pot experiments confirm that the SRFs effectively promote the growth of corn plants. This hot-melt encapsulation process is straightforward, environmentally benign, and cost-effective, presenting a promising strategy for the scalable production of high-performance bio-based SRFs.