In my fifth blog post, I explored the dangers of microplastics and their potential health impacts. Plastics pose a huge problem as they are nonbiodegradable, breaking down into micro- and nanoparticles over time but never decomposing. This has led to increasing interest in environmentally friendly biodegradable plastics. However, far from being a promising solution, biodegradable plastics overpromise and underdeliver, bringing about their own set of problems.

Shen et al. (2020) discuss the current literature on biodegradable plastics (BPs), a form of plastic that decomposes with the help of microbes into naturally occurring materials such as biomass, water and carbon dioxide. In its production stage, BPs are created using polymers that already naturally exist, such as starch, or by combining natural polymers with synthetic polymers which allows for the resulting structure to be easily degradable (Shen et al., 2020). After its usage, it will be decomposed through 3 phases: biodeterioration (caused by the accumulation of microorganisms on its surface), biofragmentation (caused by depolymerase produced by microorganisms that break down the BPs into molecules) and bioassimilation (where these molecules are taken up by microorganisms as food) (Shen et al., 2020; Figure 1). The end product of these processes is then naturally-occurring materials.

Figure 1: The ideal decomposition process of BPs (Shen et al., 2020)

There have been significant breakthroughs in the research on biodegradable plastics. In 2021, researchers from the University of California found a way to create truly biodegradable plastics using enzymes. Watch this short clip to find out more!

Unfortunately, the truly biodegradable plastics in the video are not yet commercially-available and will not be for a while. For most biodegradable plastics that we know of today, their decomposition process (Figure 1) happens only under specific conditions that may not be naturally available, such as requiring specific pH levels, temperatures, and oxygen content and may be ineffective in environments such as the ocean (Shen et al., 2020). Few industrial facilities that create the exact conditions for decomposition exist, causing BP waste to be treated no differently from conventional plastics in most cities (Beyond Plastics, 2023).

In addition to other practical issues such as the high cost of producing BPs as compared to conventional plastics and no separate management systems for BPs as compared to normal plastics (Shen et al., 2020), Qin and colleagues (2021) address the more pressing issue of BPs potentially being just as pollutive as conventional plastic. Qin et al. (2021) explored the impacts of biodegradable plastic and microplastic on soil environments, pointing out changes in soil physiochemistry and encouraging the formation of biofilms. With biodegradable microplastic (BMPs) intrusion in soils, there may be higher levels of dissolved organic carbon and decreases in dissolved organic nitrogen accompanied by increases in microbial biomass N, both of which are direct impacts on the chemistry of the soil and soil nutrient cycles (Qin et al., 2021). Additionally, microplastics have been known to form biofilms during their weathering process which protect potentially harmful pathogens and harmful microbes to thrive where previously they might not have survived. BMPs further intensify this process due to their greater speed of degradation (Qin et al., 2021). Overall, BMPs may result in the same forms of pollution that microplastics already do (Figure 2) and may even worsen the extent of pollution as they decompose even more quickly with the help of microbes.

Figure 2: Potential of pollution caused by microplastics and biodegradable microplastics (Qin et al., 2021)

Therefore, as with many solutions invented to solve man-made problems, BPs cannot be relied on to be the solution to plastic pollution. Solving the threat of overwhelming plastic pollution first requires less reliance on plastic products by society at large, followed by having more systems in place to monitor the life cycle of plastics.

To that end, governments have finally begun taking action. During the February 2022 United Nations Environment Assembly, the Intergovernmental negotiating committee (INC) was created to develop an international legally binding instruction on plastic pollution focusing on sustainable production and consumption of plastics (UNEP, 2022). The coming together of nations tell of the severity of the problem and will hopefully bring about a radical change in how plastic is viewed and treated as a commodity. Cities will likely see the greatest change given that both unsustainable consumption patterns and the greatest potential for multi-stakeholder cooperation are at the centre of cities (Ingilizian, 2019). Perhaps the quickest way to enact change would be on a personal level – to reduce, reuse and replace plastics wherever possible.

References

Beyond Plastics. (2023). Bad news—Bioplastics are not a solution to plastic pollution. https://www.beyondplastics.org/fact-sheets/bad-news-about-bioplastics

Ingilizian, Z. (2019). 3 reasons why cities can stem the plastic crisis. World Economic Forum. https://www.weforum.org/agenda/2019/06/3-reasons-why-cities-can-stem-the-tide-of-the-plastic-crisis/

Qin, M., Chen, C., Song, B., Shen, M., Cao, W., Yang, H., Zeng, G., & Gong, J. (2021). A review of biodegradable plastics to biodegradable microplastics: Another ecological threat to soil environments? Journal of Cleaner Production, 312, 127816. https://doi.org/10.1016/j.jclepro.2021.127816

Shen, M., Song, B., Zeng, G., Zhang, Y., Huang, W., Wen, X., & Tang, W. (2020). Are biodegradable plastics a promising solution to solve the global plastic pollution? Environmental Pollution, 263, 114469. https://doi.org/10.1016/j.envpol.2020.114469

United Nations Environment Programme. (2022). Intergovernmental negotiating committee (Inc) on plastic pollution. http://www.unep.org/about-un-environment/inc-plastic-pollution