Fragmentation and Mineralization of a Compostable Aromatic-Aliphatic Polyester during Industrial Composting

Compostableplastics support the separate collection of organicwaste. However, there are concerns that the fragments generated duringdisintegration might not fully biodegrade and leave persistent microplasticin compost. We spiked particles of an aromatic-aliphatic polyestercontaining polylactide into compost and then tracked disintegrationunder industrial composting conditions. We compared the yields againstpolyethylene. The validity of the extraction protocol and complementarymicroscopic methods (& mu;-Raman and fluorescence) was assessedby blank controls, spike controls, and prelabeled plastics. Fragmentsof 25-75 & mu;m size represented the most pronounced peakof interim fragmentation, which was reached already after 1 week ofindustrial composting. Larger sizes peaked earlier, while smallersizes peaked later and remained less frequent. For particles of allsizes, count and mass decreased to blank level when 90% of the polymercarbon were transformed into CO2. Gel permeation chromatography(GPC) analysis suggested depolymerization as the main driving forcefor disintegration. A transient shift of the particle compositionto a lower percentage of polylactide was observed. Plastic fragmentationduring biodegradation is the expected route for decomposing, but noaccumulation of particulate fragments of any size was observed.

Automated summary

Compostable plastics, when added into composting, undergo disintegration under industrial composting conditions. Fragmentation peaks were observed, with 25-75 μm size fragments reaching the highest peak after only one week. Larger fragments peaked earlier, while smaller ones peaked later and were less frequent. Depolymerization was identified as the main driving force for disintegration, and there was no accumulation of particulate fragments of any size.