Ceresin wax enhances hydrophobicity and density of bio-based polyurethane of controlled-release fertilizers: Streamlined production, improved nutrient release performance, and reduced cost

Bio-based coated controlled-release fertilizers (BCRFs) can significantly improve nutrient utilization and reduce pollution. However, challenges such as spray gun clogging, adhesion and tearing between fertilizers during the actual production of BCRFs pose a severe challenge to production chain development. In addition, the poor hydrophobicity and cross-linking properties of bio-based coatings severely affect the controlled release properties of BCRFs. Although some measures have been taken to ameliorate the above problems, the cumbersome and costly modification process is challenging to be applied on a large scale. Therefore, the primary goal of this work is to search for a more straightforward and efficient method of production and modification to address the aforementioned unresolved challenges in the field of CRFs. In this study, bio-based polyester polyol (BPP) was used as the base for polyurethane reaction, and low-viscosity castor oil (CO) was used as the modifier to reduce the viscosity of BPP. This led to the preparation of Inter-Modified Coated Controlled-Release Fertilizers (ICRFs) to prevent spray gun clogging. Building upon this, hydrophobic and dense wax-based coated fertilizer (WBCF) was prepared by modifying ICRF with Ceresin wax to alleviate the challenges associated with adhesion and tearing between fertilizer particles during the coating process. The WBCF exhibited remarkable controlled-release characteristics, with a nitrogen (N) release longevity of nearly 180 days, requiring only 3 % of the coating materials. This work provides a simple and efficient strategy for overcoming the key constraints in the development and production of CRFs and provides insights into developing green, low-cost fertilizers with excellent controlled-release properties. •Wax-based bio-based coated fertilizers (WBCFs) were fabricated.•The enhanced nutrient release longevities (21–180 days) were obtained.•Wax relies on permeability to plug pores, effectively slowing nutrient release.•The problem of uneven fertilizer coating in CRF production was solved.•The problem of spray-gun clogging in CRF production was solved.