Deciphering the Formation Mechanism of Recalcitrant Microplastics during Bioplastic Degradation in Aerobic Environment.

Biodegradable plastics are frequently characterized as materials capable of complete mineralization under specific environmental conditions. Although the application of bio-based substitutes for traditional plastics has become widespread, numerous studies have reported that these materials also contribute to microplastics contamination and plastic pollution. However, the formation and degradation dynamics of recalcitrant microplastics remain insufficiently understood. This study investigated the degradation behavior of two typical compostable polyester plastics over a 100-day period under aerobic conditions. Results showed that microplastics in compost were mainly distributed around 15-20 μm, and a significant proportion of aromatic ring structures persisted in the degradable products. Besides, an appropriate amount of nitrogen supplement promotes microbial growth facilitating plastic degradation, playing a significant role in the mineralization process. Therefore, modulation of nitrogen represents an effective strategy to promote plastic degradation while mitigating microplastic formation. This finding offers novel insights for the degradation of biodegradable polyester plastic and the fate of their derived recalcitrant microplastics.