Quantification of the natural biodegradability and assessment of environmental impacts to determine the overall sustainability of bioplastics

Between massive growth in plastic production and its inability to decompose quickly, plastic pollution is increasing rapidly, particularly in aquatic ecosystems. Wind and water currents transport plastic waste to areas with little water movement, creating massive conglomerates of plastic waste and negatively impacting water quality. Most of these plastics are single-use plastic, so there is a critical need to shift toward bioplastics. In this research, the biodegradability of bioplastics, specifically polylactic acid (PLA) and polyhydroxyalkanoate (PHA), was quantified as a function of carbon dioxide (CO₂) production in lake, river, and marine environments. Biodegradability was also measured using Attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy analysis to visually assess functional group changes in the plastic polymers before and after experimentation. In addition to lab-based quantification of bioplastic biodegradation, this research investigated the environmental impacts of traditional plastics compared to bioplastic alternatives using Life Cycle Assessment (LCA). Two comparative LCAs were conducted to account for varying end-of-life treatment of plastics; the first represented the current state of plastic waste management, and the second represented the goals set by the US Plastics Pact to reduce plastic in landfills and increase recycling of plastics. Experimental data found that PHA showed evidence of biodegradation best in rivers, followed by lakes and then marine environments while PLA showed minimal degradation in all aquatic environments. The ATR-FTIR analysis showed some new peak formation and changes in peak intensity in preliminary results with the marine samples. The LCA results showed that while bioplastics had comparable environmental burdens in the production stage, their benefits were clear when end-of-life applications (i.e., organic recycling) were effectively considered. Between the current and target scenarios, there were reductions across all environmental impact categories for bioplastics, and they had a lower environmental burden than traditional plastics. It was concluded that PHA degraded in some natural water bodies and that both PHA and PLA are a more sustainable alternative to traditional single-use plastics.