Fate of Biodegradable Polymers Under Industrial Conditions for Anaerobic Digestion and Aerobic Composting of Food Waste

Biodegradable polymers were introduced in the past decades in order to address the issue of plastic pollutions, and these materials have thus required the development of methodologies to understand and evaluate their disintegration. The aim of this study was to simulate the organic fraction of municipal solid waste (OFMSW) treatment in laboratory-scale and to assess the biodegradation of poly(lactic acid) (PLA) water bottles and starch-based bags under real industrial conditions of anaerobic digestion and aerobic composting. Methane production and loss of mass were determined to estimate the anaerobic degradation; whereas phytotoxicity tests were carried out to provide an evaluation of the compost quality. To visualize the effects on the materials, SEM analyses, differential scanning calorimetry (DSC) and FT-IR/ATR spectroscopy were performed. Different outcomes were found for the tested bioplastics products. PLA bottles didn’t biodegrade under anaerobic conditions and the pieces appeared wrap up at the end, while starch-based bioplastic bags performed 85.79% of disintegration degree. CH4 production was between 40 and 50% for both the products. Phytotoxicity test on the final composts highlighted negative effects on both selected seeds for PLA solutions. Water-soluble lactic acid from degraded PLA bottle significantly reduced the pH of compost affecting seed germination and germination indexes. Both bioplastics showed chemical modification according to DSC and FT-IR/ATR analyses.