Complex study of bioplastics: Degradation in soil and characterization by FTIR-ATR and FTIR-TGA methods

Abstract

Today our society faces a twofold problem: the depletion of resources and the accumulation of waste. Today's market dictates that conventional plastics should be replaced by bioplastics, but there is a lack of research on using bioplastics, still sparking debates whether bioplastics are more sustainable than conventional plastics. This research investigates bioplastic degradation characteristics in soil (ATR-FTIR), thermal stability under pyrolysis and applicability for waste-to-energy using thermal analysis (TG) and evolved gas analysis (FTIR). Biodegradation experiments revealed that only bioplastic made of corn starch was able to completely and rapidly degrade in soil, while other bio-based and petroleum-based plastics only changed the colour and became softer. This proves that bioplastics are thermochemically altered and close in properties to conventional plastics, and solutions must be taken to recycle them properly or convert them into energy, otherwise, they are the exact source of microplastics. Thermogravimetric together with evolved gas analysis (TGA-FTIR) revealed that the gaseous yield from bioplastics is in the range of 80–99%, with the onset of degradation at 203.0–272.5 °C in N2 environment, or 10–20 °C degrees below by enriching the environment with steam. Mainly, pyrolysis of volatile products of bioplastics are carboxylic compounds, alkanes, alkenes, aromatic hydrocarbons, amines, CO, and CO2 depends significantly on the chemical composition of plastic.