A Comprehensive Review on Lignin-Based Biodegradable Mulch Films for Sustainable Agriculture

Mulch films play a vital role in modern agriculture by enhancing soil hydrothermal conditions, suppressing weed growth, and improving crop performance. Across 13 major crops, mulching increased yields by an average of 26%, with particularly strong responses in soybean (44%), millet (42%), wheat (29%), and maize (25%), and improved water-use efficiency by up to 33%. However, conventional polyethylene (PE) mulch films accumulate persistently in soils, reaching 7183–10,586 microplastic particles/kg in topsoil after long-term use and contributing up to 56% of total microplastics across the 0–100 cm soil profile. These residues impair enzymatic activity, disrupt nutrient cycling, and alter microbial community structure, making biodegradable alternatives essential for mitigating these issues. Lignin-based biodegradable mulch films (BDMs) have gained increasing attention owing to lignin’s intrinsic UV-shielding capacity, mechanical reinforcement, hydrophobicity, and biodegradability. Lignin-containing films may block UV radiation below 300 nm, reduce visible-light transmittance by ~80%, exhibit thermal stability up to 150 °C, and demonstrate low water vapour permeability (3.41 × 10⁻⁸ g/m·h·Pa) depending on formulation and lignin loading. Incorporation of lignin may enhance biodegradability, increasing soil-burial degradation by 25.47% relative to pure PVA, with composite systems achieving ~55% degradation within 50 days. This review provides a comprehensive assessment of lignin structure, sources, chemistry, extraction methods. It examines lignin as a renewable and value-added feedstock for mulch applications, and critically evaluates the optical, mechanical, thermal, hydrophobic, and biodegradation properties of lignin-based BDMs. The review also discusses their agronomic applications, including weed suppression, soil moisture retention, nutrient management, and soil microclimate regulation, while analysing the economic considerations affecting large-scale implementation and commercial feasibility. Finally, it outlines key research priorities to enable scalable, field-reliable, and environmentally sustainable mulch film technologies.