Evaluation of the degradation of plastics PET and PE type under composting conditions using coffee pulp as substrate

Abstract

The indiscriminate use, the alarming accumulation of plastic, and its subsequent poor well-disposal and management have generated the current environmental problem. As an environmentally friendly and effective strategy, composting processes arise like a method for waste treatment. This study explored the degradation of polyethylene terephthalate (PET) and low-density polyethylene (PE) plastic types under composting conditions for 90 days using coffee pulp as substrate into the compost. The degradation was estimated from weight variation over time, the thermal stability of the PET and PE samples was carried out using thermogravimetric analysis (TGA/DTA) whereas the chemical and morphological changes on the samples were assessed by FT-IR and SEM. The bacterial communities of composting were also investigated by 16S rRNA gene clone analysis. The results showed a partial degradation of PET and PE samples under composting conditions for the period of time considered. However, a strong adhesion effect was observed for PE samples which give place to a variation on the thermal stability of the samples. 16S RNA gene clone analysis showed that Sphingobacterium was the dominant bacteria, which is not related with the degradation of plastic material on composting. This result could be related with a reduced degradation during the composting treatment.