Microplastic Generation and Persistence of Biodegradable Plastics under Anaerobic Conditions

Area of Science:

• Environmental Science
• Polymer Science
• Microplastics Research

Background:

• Biodegradable plastics (BPs) are replacing conventional plastics.
• Their degradation in anaerobic environments and microplastic generation are not well understood.
• Lack of methods to separate BP-derived microplastics (BPMs) from sludge hinders research.

Purpose of the Study:

• Develop accurate, polymer-specific methods for BPM separation and identification.
• Investigate microplastic generation during anaerobic degradation of eight common BPs.
• Determine the influence of polymer chemistry on anaerobic degradation pathways and outcomes.

Main Methods:

• Developed and validated polymer-specific separation and identification techniques for BPMs.
• Achieved >94.9% recovery rates for most BPMs.
• Analyzed microplastic generation, transformation, and molecular evolution during mesophilic anaerobic degradation.

Main Results:

• Distinct degradation pathways observed based on polymer structure.
• PHB, PHBV, and CDA showed high biodegradability (79.1-87.1%) with transient microplastics.
• PBSA and PLA yielded persistent microplastics with low biodegradability (27.3%, 19.5%).
• PBS fragmented extensively; PBAT and PCL produced limited small microplastics (<300 μm) without significant methanogenesis.

Conclusions:

• Polymer chemistry is key in determining if BPs fully degrade or form persistent microplastics anaerobically.
• Several certified BPs can be significant microplastic sources in anaerobic environments.
• Findings are crucial for waste management and understanding microplastic fate in natural settings.