Degradation of excavated polyethylene and polypropylene waste from landfill

Luisa Canopoli; Frédéric Coulon; Stuart T Wagland

doi:10.1016/j.scitotenv.2019.134125

Degradation of excavated polyethylene and polypropylene waste from landfill

Sci Total Environ. 2020 Jan 1:698:134125. doi: 10.1016/j.scitotenv.2019.134125. Epub 2019 Aug 26.

Authors

Luisa Canopoli¹, Frédéric Coulon¹, Stuart T Wagland²

Affiliations

¹ School of Water, Energy and Environment, Cranfield University, Cranfield, Bedfordshire, MK43 0AL, UK.
² School of Water, Energy and Environment, Cranfield University, Cranfield, Bedfordshire, MK43 0AL, UK. Electronic address: s.t.wagland@cranfield.ac.uk.

PMID: 31783451
DOI: 10.1016/j.scitotenv.2019.134125

Abstract

In 2016, it was estimated that 7.4 million tonnes of plastic waste have been disposed in landfill in Europe. This waste represents an important opportunity for resource recovery through enhanced landfill mining consistent with recent Circular Economy initiatives. However, a recent review found a lack of data describing the degradation of excavated plastic waste and the potential impact on recycling products such as pyrolysis oil. In this study, the physicochemical characteristics of the main plastic types found in landfills and their implications for recovery and recycling were investigated using a combination of scanning electron microscopy energy dispersive spectroscopy (SEM-EDS), attenuated total reflectance Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC). Loss of gloss was visually detected for the buried plastic waste samples (polyethylene (PE) and polypropylene (PP)) compared to fresh plastic samples. The SEM-EDS analysis further showed that oxygen was the main element related to the plastic surface alteration. The carbonyl index (CI) of plastic samples buried for >10 years was between 1.5 and 2 times higher than <10 years and fresh materials. Similarly, the degree crystallinity of the old samples (>10 years) was 2 times higher than the fresh and < 10 years samples. Based on these findings, tertiary recycling, such as pyrolysis, seems to be a convenient route for upcycling of recovered plastics from municipal solid waste landfills.

Keywords: Enhanced landfill mining; Excavated plastic; Plastic degradation; Plastic recovery.