Melt-blended biodegradable mulching films with zeolite fillers from industrial by-products: A scalable, solvent-free route for controlled zinc delivery

To produce functionalized mulching films with added agronomic benefits, poly(butylene succinate- co-adipate) (PBSA) composites were developed by incorporating small amounts (2–4 wt%) of two different zeolitic tuffs through melt compounding. One of the zeolitic tuffs, sourced as byproduct of quarrying operations, was enriched in zinc ions (Zn2 +) by cation-exchange process, enabling the zeolite to act as a reservoir of an essential micronutrient for plant growth. All the composite films were characterized in terms of mechanical and thermal properties to evaluate their suitability for agricultural applications, where flexibility and thermal stability are critical. Among the tested formulations, PBSA composites containing 4 wt% chabazite-rich zeolitic tuff exhibited good mechanical performance, with suitable elongation at break values. The addition of polyethylene glycol (PEG) enhanced filler dispersion, thereby preserving the mechanical properties of the composite. Kinetic release studies on composite granules and film demonstrated a controlled release of Zn2+, with values of 14.9 ± 1.91 mg/kg and 9.33 ± 1.56 mg/kg for the material in granular and film forms, respectively, after 96 h of extraction. Overall, the results support the development of biodegradable mulching films that combine mechanical robustness with functional agronomic benefits, potentially contributing to more sustainable and efficient agricultural practices through weed suppression, soil protection, and micronutrient enrichment.