In a study published in Results in Surfaces and Interfaces, Karthikeyan Ramesh and Vimala Raghavan explored a method to reduce nitrogen fertilizer loss, a major source of environmental pollution. They created bentonite-urea beads (BU) and biochar-bentonite-urea beads (BBCU) using banana leaf sheath (BLS) biocharBiochar is a carbon-rich material created from biomass decomposition in low-oxygen conditions. It has important applications in environmental remediation, soil improvement, agriculture, carbon sequestration, energy storage, and sustainable materials, promoting efficiency and reducing waste in various contexts while addressing climate change challenges. More. The goal was to achieve a slow release of nitrogen to match the plant’s needs and minimize environmental impact.  

The researchers found that BBCU beads had significantly improved water absorption (89%), swelling ratio (2.75), equilibrium water content (68%), and water retention (73.23%) compared to BU beads. This enhanced water retention capacity of BBCU beads facilitates a gradual release of fertilizer, aligning with the plant’s growth cycle and maximizing fertilizer effectiveness.  

The successful incorporation of nutrients into the composite materials was confirmed through Fourier-Transform Infrared spectroscopy (FT-IR) and X-Ray diffraction (XRD) analysis. Thermogravimetric analysis (TGA) demonstrated that the BBCU beads had slightly higher thermal stability than BU beads, likely due to the presence of BLS biochar.  

Scanning Electron Microscopy (SEM) revealed that BU beads had a dense structure with a relatively smooth surface. In contrast, BBCU beads exhibited an undulated and highly porous surface, which contributed to their increased water absorption and retention capabilities. Elemental analysis confirmed the presence of nitrogen in the fertilizer beads. Nutrient release studies demonstrated a steady release of nitrogen from BBCU beads in the soil, indicating their potential to reduce environmental pollution associated with conventional fertilizers.  

This research offers a promising strategy for converting agricultural waste into valuable slow-release fertilizers, addressing both agricultural and environmental challenges.  

SOURCE: Ramesh, K., & Raghavan, V. (2025). Biochar/bentonite composite beads for controlled nitrogen release and reduced environmental impact: From banana waste to sustainable food security. Results in Surfaces and Interfaces, 19, 100500.