Thermochemical processing of boron-impregnated cellulose insulation waste for upcycling to slow-release boron fertilizers

Boron (B) fertilizers are essential for global crop production. Sustainable B use demands a higher efficiency of B fertilizers through controlled B release and an enhanced B recycling from secondary sources, e.g. B-impregnated cellulose fiber insulation (CFI) waste. In this study, thermochemical treatments based on combustion and py-rolysis were investigated for processing CFI waste into a slow-release B fertilizer. Hot-water extractions of ob-tained materials confirmed that slow-release properties were achieved, and material characterization with XRD, FTIR and 11B-NMR showed that these were largely the result of formation of sparingly soluble Ca-B phases. A seedling toxicity test with fodder rape demonstrated the benefit of this slow-release B in comparison with conventional soluble B to circumvent toxicity, suggesting potential for B application via seed coatings. Finally, a fertilization trial with fodder rape and poppy seed showed that most slow-release B compounds were equally effective as soluble B at recommended B doses, while slow-release B can still benefit from reduced B leaching losses.

Automated summary

Boron (B) fertilizers are crucial for global crop production. A study investigated thermochemical treatments to process cellulose fiber insulation waste into a slow-release B fertilizer, achieving slow-release properties through the formation of sparingly soluble Ca-B phases. Results showed the potential of slow-release B in reducing toxicity and leaching losses, indicating its effectiveness as a B application method.