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Study on the degradability of plastics with prodegradant additives during anaerobic and aerobic biological waste treatment processes
Summary
Researchers evaluated whether PP and PET plastic packaging specimens containing commercially available prodegradant additives actually degrade under simulated composting and anaerobic digestion conditions. None of the materials fragmented into microplastic particles larger than 1 mm under the tested conditions, though FTIR detected surface oxidation in PP samples and PET specimens showed roughly 6.5% mass loss during anaerobic digestion, calling into question the degradability claims of such additives.
Abstract The degradability of conventional plastic packaging specimens made from PP and PET, that were produced with novel prodegradant additives, was investigated during biological waste treatment processes. The additives were merchandised to foster the degradation of commodity plastics by enzymatic or by abiotic processes. Four different plastic packaging specimens and two different additives were evaluated for their biodegradability during anaerobic and aerobic waste treatment conditions. Aerobic treatment was investigated in laboratory rotting tests, simulating conditions during composting in a plant according to the Austrian state-of-the-art, while anaerobic treatment was investigated in laboratory digestion reactors. The study shows that only the PET specimens showed a loss of mass of ca. 6.5%, during 50 days of digestion at 52 °C. None of the specimens degraded during the aerobic rotting process. None of the materials fragmented into microplastic particles of sizes > 1 mm under the investigated conditions. However, FTIR analysis revealed the oxidation in the case of PP specimens, which indicated a mediated oxidation process during composting, independent of the merchandised mechanism of predegradation. Under anaerobic conditions, the plastic specimens containing reactors produced more biogas within the first 20 days of digestion, that did not originate from an observable degradation of the plastics.
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