Lignin-Containing Cellulose Acetate Films from Grapevine Waste: A Sustainable Path to Compostable Bioplastics

Grapevine shoots, a viticultural residue rich in cellulose (∼34%) and lignin (20–27%), were valorized through an eco-designed biorefinery process integrating autoclave-assisted pretreatment and organosolv extraction. This approach enabled the corecovery of cellulose and lignin under mild, sulfur-free conditions, followed by a chlorine-free bleaching that retained ∼7 wt % lignin within the cellulose. Rather than being removed, lignin was preserved as a natural additive for its antioxidant and UV-shielding functions, reducing the need for synthetic components. The lignin-containing cellulose was acetylated (DS ≈ 1.7) and plasticized with glycerol to produce biodegradable films. These films fully disintegrated under home composting within 8 weeks, outperforming commercial cellulose acetate. The process aligns with green chemistry principles and EU circular economy goals, offering a sustainable route to multifunctional bioplastics from agricultural waste.