Microplastic formation during degradation: bioplastics vs conventional plastics

Biodegradable plastics are increasingly promoted as alternatives to conventional fossil-based plastics, but under non-ideal end-of-life conditions they may fragment into microplastic particles instead of fully biodegrading. In this work, the degradation of bioplastics and conventional plastics was compared under two pathways: accelerated UV ageing in saline water and mechanical abrasion with sand. PLA, PHB, LDPE, and PP were studied under UV ageing, while PLA, PHB, TPS, LDPE, and PP were evaluated under mechanical abrasion. Degradation was assessed through mass loss, surface changes, colour variation, mechanical properties, and microplastic generation. Under accelerated UV ageing, PLA and PHB showed the strongest degradation, with higher mass loss, more pronounced surface damage, larger colour changes, and greater mechanical deterioration than LDPE and PP. Under abrasion, PHB and TPS showed the highest mass loss, while LDPE and PP were more resistant. Microplastic generation increased with degradation time for all materials, although with clear differences depending on polymer type and degradation route. Overall, the results show that the biodegradable plastics evaluated in this study did not necessarily present a lower risk of microplastic release than the conventional plastics tested under the same conditions. Under the same degradation conditions and exposure time, some biodegradable polymers generated even larger amounts of particulate material, indicating higher potential for microplastic generation.