Property changes of conventional plastic waste mixed with municipal solid waste after 10-year degradation experiments simulating landfill conditions

The cumulative amount of plastic waste (PW) produced worldwide is staggering, and approximately 38% is disposed of in landfills. Currently, there is little information about the properties of landfilled PW to support proper recovery and management, nor to prevent secondary pollution, e.g., microplastics. In this study, the municipal solid waste (MSW) containing PW was excavated from four landfills in the United States and degraded in landfill simulators for 4–5 years. The degraded MSW and PW was stabilized for another 5–6 years. The degraded, fresh, semi-fresh, and mechanically damaged PW samples are characterized using scanning electron microscopy, goniometer, Fourier transform infrared spectroscopy, and differential scanning calorimetry. Significant changes in contact angle and carbonyl index are observed in the degraded samples compared to the semi-fresh samples. The changes in properties are confined to the PW surfaces, while the bulk crystallinity shows no obvious alternation. This study presents the first series of correlations between the changes in plastic carbonyl index due to degradation and the MSW characteristics including initial composition, biogas generation rate, and biodegradation-induced vertical strain.