Nanozeolite-Coupled Biochar-Based Controlled-Release Phosphorus Fertilizer: Performance, Release Mechanism, and Techno-Economic Analysis

Phosphorus fertilization is critical for crop production; however, traditional chemical phosphorus fertilizers (Chem-P) are highly inefficient, which leads to nutrient loss and environmental pollution. Here, a new nanozeolite-coupled biochar-based phosphorus fertilizer (ZEO/BC-PSRF) was developed using a simple disc granulation process, with kaolinite serving as a binder. The controlled-release performance of this fertilizer was evaluated through water release testing, where ZEO/BC-PSRF demonstrated the slowest phosphorus release, with only 29.4% being released after 24 h, compared with 43.8% for BC-PSRF (without nanozeolite) and 54.3% for Chem-P. Additionally, ZEO/BC-PSRF exhibited the best controlled-release performance in column leaching tests, with a cumulative P release rate reaching 23.4% after 42 days. A greenhouse pot experiment with tomato demonstrated that ZEO/BC-PSRF significantly enhanced seedling growth and increased the levels of vitamin C and lycopene in the harvested fruits compared with the BC-PSRF and Chem-P treatments. Mechanistic investigations suggest that the primary mechanism for the controlled release of phosphorus from ZEO/BC-PSRF is the enhanced adsorption of phosphorus onto the ZEO/BC. Further, ZEO/BC-PSRF maintained the highest available soil phosphorus content, promoting the growth of phosphorus-utilizing soil bacteria and facilitating enhanced phosphorus uptake by tomato. An economic feasibility analysis confirmed the potential for cost-effective large-scale production, while a comparison of carbon emissions indicated that the application of ZEO/BC-PSRF had the capacity to reduce greenhouse gas emissions in contrast to traditional Chem-P. This study highlights the potential of combining biochar and zeolite as a sustainable and low-cost solution to enhance the efficacy of phosphorus fertilizers in agricultural production while simultaneously reducing carbon emissions.