In situ degradation of biodegradable bio-based plastics in urban soil: Pilot study for PLA, PHB, PHBH, and Bio-PBS in central Tokyo, Japan.
Kobayashi A, Harada Y, Mitoma Y
Soil Health
PubMedThose 'compostable' plant-based plastic bags and containers you toss in your garden compost bin may still be sitting there largely intact years later, quietly cluttering the soil your vegetables grow in.
Scientists buried four types of plant-based 'biodegradable' plastics in Tokyo city soil for four months and found most barely broke down at all. The plastics made from a type of bacteria-produced material did degrade faster, especially when buried alongside food scraps. The plastics made from corn starch (PLA) and another common bio-plastic showed almost no weight loss, though their chemical structure was beginning to change.
Key Findings
PHB and PHBH plastics lost more mass when buried with food waste, dropping from 91–99.5% remaining down to 77–91% remaining over 120 days.
PLA and Bio-PBS showed almost no weight loss (98.3–100% mass remaining), even after 4 months in urban soil.
Researchers estimate complete degradation of these bio-plastics in Tokyo urban soil could take at least several years under normal conditions.
chevron_right Technical Summary
Biodegradable plastics marketed as eco-friendly take much longer to break down in urban soil than expected — potentially years — though mixing them with food waste speeds up the process for some types.
Abstract Preview
Biodegradable bio-based plastics (BBPs) are increasingly replacing conventional plastics for reducing negative environmental impacts, while few studies tested BBPs' biodegradability in urban soil, ...
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