Polyethylene and related hydrocarbon polymers ("plastics") are not biodegradable

Area of Science:

• Polymer Science
• Environmental Microbiology
• Biotechnology

Background:

• Research on the biodegradation of polyethylene (PE) and polystyrene (PS) is increasing.
• The definition of biodegradability is often diffuse, leading to questionable claims.
• Many studies report marginal weight loss or fragmentation, not true biodegradation.

Purpose of the Study:

• To critically evaluate the evidence for the biodegradation of hydrocarbon polymers.
• To investigate the validity of claims regarding PE and PS biodegradability.
• To highlight alternative explanations for observed polymer degradation phenomena.

Main Methods:

• Review of existing literature on polymer biodegradation.
• Analysis of data from studies using bacterial strains and insect larvae.
• Consideration of alternative explanations for polymer mass loss and surface changes.

Main Results:

• No convincing evidence for the substantial biodegradation and mineralization of PE or PS has been found.
• Observed effects are often attributable to polymer impurities, additives, low molecular weight oligomers, or physical fragmentation.
• Evidence for biotic/abiotic oxidation is insufficient to claim biodegradability.

Conclusions:

• The widely claimed biodegradability of PE and PS lacks robust scientific evidence.
• The expanding research in hydrocarbon polymer biodegradation may be misguided.
• Further research using methods like isotope-labeled polymers is needed to convincingly demonstrate biodegradation.