Degradation of conventional and biobased plastics in soil under contrasting environmental conditions

Abstract

Plastics are essential materials, but their extensive production poses a threat to the environment. Biobased plastics provide an alternative, that reduce, in many cases, their perdurability. The degradation of conventional (polyethylene (PE) / polyethylene terephthalate (PET) and polyamide (PA) / polypropylene (PP)- ethylene vinyl alcohol (EVOH)-PP) and polylactic acid (PLA)-based materials was evaluated through an in situ manipulative experiment for one year simulating different soil scenarios. The degradation of the materials was evaluated by means of weight loss, differential scanning calorimetry and infrared spectroscopy. Conventional materials showed values less than 2% of weight loss for all treatments after one year. The weight loss in PLA-based materials was notably enhanced at temperatures above 20°C and with high water availability, while soil texture showed a minor influence. The carbonyl and crystallization indices, as well as the enthalpy of fusion, detected early signs of degradation of biobased materials and confirmed the degradation detected by weight loss. This study highlights that the degradation of materials can be markedly different depending on the environmental conditions in terrestrial environmental compartments such as soil, where water availability and temperature can be more variable than in marine environments. Thus, the certification of material degradability needs to be linked to the specific environmental compartment and conditions in which the material has been tested.