A review on the sustainable starch-based bioplastics synthesis and characterizations derived from renewable natural extracts

The escalating environmental burden of petroleum-based plastics have intensified the demand for sustainable and biodegradable alternatives. Bioplastics derived from renewable natural extracts (RNEs) have emerged as a promising solution to reduce dependence on fossil fuels, greenhouse gas emissions, and persistent plastic pollution. This review critically evaluates sustainable bioplastics synthesised from RNEs, emphasising starch matrices reinforced with plant extracts, essential oils, and polyphenols that can improve tensile strength by 20–60%, enhance thermal stability by 10–30 °C, and reduce water vapour permeability by up to 40% compared to neat starch films. The review also addresses fabrication techniques, including solvent casting, extrusion, injection moulding, compression moulding, and thermoforming, and assesses their scalability and energy demand. However, the usage of extrusion-based processes can reduce solvent use by >80% compared to casting methods. Furthermore, the comprehensive characterisation approaches for physicochemical, thermal, mechanical, and biodegradation performance are consolidated, with many RNE-based films achieving 60–90% biodegradation within 90–180 days under composting conditions. Moreover, challenges related to cost (20–50% higher than conventional plastics), processing compatibility, and regulatory harmonisation still persists. Therefore, RNE-derived bioplastics applications demonstrate strong potential in food packaging, agriculture, biomedical, and construction sectors within circular-economy frameworks.