Biodegradation in Freshwater: Comparison Between Compostable Plastics and Their Biopolymer Matrices

Area of Science:

• Environmental Science
• Polymer Science
• Ecotoxicology

Background:

• Plastic pollution in freshwater ecosystems is a growing concern.
• Biodegradable polymers (BPs) are sought as alternatives, but their environmental degradation is poorly understood.
• In situ studies are needed to assess real-world BP performance.

Purpose of the Study:

• To compare the in situ degradation of compostable items and their polymer matrices in a freshwater ecosystem.
• To analyze changes in material properties, morphology, and microbial colonization over time.
• To evaluate the accuracy of laboratory degradation tests versus natural environmental conditions.

Main Methods:

• Four-month in situ study in a lentic freshwater ecosystem.
• Tested Mater-Bi® (PBAT) and PLA items/matrices, plus PHBV and PP.
• Analyzed morphology, chemical composition, thermal/mechanical properties, and microbial colonization.
• Employed a validated cleaning protocol for surface analysis.

Main Results:

• Limited degradation of pure polymers and commercial products after 120 days, with variations among materials.
• Compostable materials showed significant filler leaching, causing fragmentation.
• PHBV degraded fastest among polyesters; PP showed minimal surface changes.
• Microbial colonization varied, but long-term degradation was constrained by polymer properties and plastisphere development.

Conclusions:

• Standard laboratory tests may overestimate BP environmental degradability.
• In situ assessments are vital for accurate evaluation of polymer degradation in freshwater.
• Careful cleaning and property characterization are essential for reliable results.