Chemical Assessment of Biodegradable Plastics Performance Under Nigerian Tropical Conditions

Plastic waste management is a critical environmental challenge across Nigeria, and biodegradable plastics have been proposed as a partial solution to reduce the persistence of plastic litter in the environment. However, the actual biodegradation performance of commercially available biodegradable plastics under Nigerian tropical climate conditions is not well documented. This study chemically assessed the performance of five types of biodegradable plastics marketed in Nigeria, including polylactic acid, polyhydroxybutyrate, thermoplastic starch, oxo-biodegradable polyethylene, and cellulose acetate, under simulated tropical soil burial and accelerated UV weathering conditions. Test specimens were prepared and subjected to treatment for 90 and 180 days. Biodegradation was assessed by weight loss, carbon dioxide evolution, tensile property retention, differential scanning calorimetry, and Fourier-transform infrared spectroscopy. After 180 days of soil burial, weight losses ranged from 8 percent for oxo-biodegradable polyethylene to 68 percent for thermoplastic starch. Polylactic acid showed 34 percent weight loss and substantial crystallinity changes by DSC. Infrared spectroscopy revealed progressive oxidation and chain scission in all samples. Oxo-biodegradable polyethylene showed primarily fragmentation rather than true mineralisation, suggesting it may generate microplastic rather than genuinely biodegrading. These findings indicate that performance of biodegradable plastics varies enormously and that not all marketed biodegradable products achieve true biodegradation under Nigerian conditions. Recommendations include adoption of performance-based biodegradability standards for Nigeria and restriction of oxo-degradable additives in single-use packaging.

Keywords: biodegradable plastics, tropical conditions, polylactic acid, biodegradation assessment, Nigeria