A Lignin-Based Biodegradable Mulch Film with Zn²⁺ Coordination Networks for Sustainable Agriculture

The environmental persistence of conventional plastic mulch films imposes substantial ecological burdens. With rising demands for sustainable agriculture, biodegradable alternatives attract growing interest. However, existing biobased films often face trade-offs between mechanical robustness, environmental adaptability, and functional versatility. In this study, we fabricated a mechanically enhanced multifunctional lignin-based composite mulch by blending modified sulfate lignin (SKL), poly(vinyl alcohol) (PVA), nanocellulose (CNF), and ZnCl₂. The work elucidated the synergistic interfacial mechanism underlying its superior properties. Zn²⁺ coordination with lignin sulfonic acid groups and SKL/PVA/CNF hydrogen bonding form a hierarchical network. This yields exceptional toughness (40.57 MJ/m³), ∼99% UV-blocking, hydrophobicity, moisture barrier, and thermal stability. The film degraded 70% in 40 days─far exceeding conventional mulch (CM). Its inherent biodegradability offers significant potential to replace agricultural plastics, advancing sustainable materials.