A peer-reviewed laboratory study found a wide gap between plastics carrying the same biodegradable label. In oxygen-free landfill leachate, PHB converted rapidly to biogas, PLA needed much longer and PBAT remained largely intact. The findings concern controlled bottles and a particular microbial community, with real landfill conditions adding further complexity.
Plastics sold as biodegradable followed sharply different paths in a peer-reviewed laboratory experiment. Researchers incubated plastic films without oxygen in leachate from South Korea’s Buyeo landfill. At 35 °C, polyhydroxybutyrate, or PHB, reached 99.9 per cent mineralization within 17 days. Polylactic acid, or PLA, reached 83.6 per cent over 320 days. Polybutylene adipate terephthalate, or PBAT, remained largely intact.[1]
Mineralization here describes conversion of polymer carbon into biogas. The percentages came from net gas production relative to theoretical production, with plastic-free bottles accounting for gas from the leachate itself. Surface examinations accompanied these measurements: PHB deteriorated rapidly, PLA developed damage more slowly and PBAT showed little change. These tests followed the films’ transformation rather than simply their disappearance from view.[1]
Microbial sequencing separated genes potentially involved in polymer breakdown from the smaller group showing transcriptional activity. Much of this activity took place in microbial films growing on the plastics. Gene similarity alone cannot establish which material an enzyme breaks down. The bottles also leave out temperature variation, oxygen gradients and mixed waste found in operating landfills, so their rates cannot supply a universal disposal timetable.[1]
