Biodegradation of plastic materials in various aquatic systems

Thanks to my father’s profession, I had the opportunity to live in various cultures around the world, which gave me firsthand exposure to the Earth’s diverse ecosystems and fostered a deep appreciation for nature. In college, I spent much of my free time birdwatching and collecting insects, and it was during these moments that I began to notice the tangible impact of human activities on the environment. One striking experience was encountering a pile of plastic waste in the middle of Tam Dao National Park, a protected area in Vietnam. Witnessing such pollution in a pristine rainforest
motivated me to pursue research in environmental engineering, aiming to create a safer and more sustainable future. As a Master’s student in the Waste-Innovation Technology for Humanity Lab (WITHLAB) at the Korea Advanced Institute of Science and Technology (KAIST), I focus on tackling plastic pollution through environmental microbiology research.

My research primarily centers on addressing plastic pollution in aquatic systems. Over two million tons of plastic waste enter aquatic environments annually, presenting a major obstacle to conserving clean and sustainable water resources. One promising solution to this problem lies in adopting biodegradable plastics as alternatives to conventional, non-degradable plastics. Biodegradable plastics can be broken down, depolymerized, and eventually mineralized by microorganisms in natural environments, converting them into CO 2 , biomass, and water. Given their environmental benefits, the production of biodegradable plastics has been steadily increasing and is projected to grow further in the coming years.

Despite all of the opportunities offered through biodegradable plastic production, I began questioning the effectiveness of the biodegradable plastic breakdown in natural aquatic environments. Certifications for biodegradability are typically based on laboratory conditions that are optimized with high temperatures and nutrient availability – conditions that seldom represent real-world aquatic systems. As a result, this curiosity led me to investigate the biodegradation behaviors of two widely used biodegradable plastics, polybutylene adipate terephthalate (PBAT) and polyvinyl alcohol (PVA), within simulated wastewater, freshwater, and seawater microcosms. My findings revealed distinct degradation patterns across the aquatic systems, evident from changes in the physicochemical properties of PBAT and PVA films and the microbial composition of plastic-associated biofilms. Notably, PBAT exhibited near-zero biodegradation rates in both freshwater and seawater, whereas PVA demonstrated potential for degradation in these environments. Interestingly, pre-exposure to nutrient-rich wastewater, an artificial environment with greater bacterial diversity than natural waters, significantly accelerated the degradation of both polymers.

Altogether, my findings highlighted that many biodegradable plastics are rarely degradable in natural aquatic environments. A more context-specific evaluation is crucial to accurately assess the degradation potential of these materials. Furthermore, wastewater demonstrated its potential to support the biodegradation of these plastics, suggesting an opportunity to utilize existing wastewater treatment systems to eliminate biodegradable plastics effectively.

Through my work on plastic pollution, I have come to understand that tackling this issue requires a combination of global and localized solutions. Collaboration among researchers from diverse fields – including materials engineering, systems biology, and water engineering – is essential. I hope this article inspires a shared commitment to addressing plastic pollution and fostering healthier aquatic ecosystems.

Reference:

1. Kim, Youngju, et al. “Biodegradation of poly (butylene adipate terephthalate) and poly (vinyl alcohol) within aquatic pathway.” Science of The Total Environment 953 (2024): 176129.
2. Lebreton, Laurent CM, et al. “River plastic emissions to the world’s oceans.” Nature communications
   8.1 (2017): 15611.

Written by: Youngju Kim

Young (Youngju) Kim is a Master’s student in the Department of Civil and Environmental Engineering at KAIST, working under the supervision of Professor Jaewook Myung. His research focuses on the biodegradation of various materials in aquatic environments, with an emphasis on microbial ecosystems and their interactions with plastic waste. Beyond research, Young is a passionate wildlife enthusiast who enjoys birdwatching and insect collecting.