- Oxo-degradable plastics
- Oxo-biodegradable plastics
- Oxo-fragmentable plastics
- Pro-oxidant additive containing plastics
- Photo/thermo-degradable plastics
- Biodegradable plastics
Oxo-degradable plastics are conventional, fossil fuel-based plastics mixed with additives((Typical oxo-degradable additives include organic salts of transition metals like iron, nickel, cobalt, or manganese, which react with oxygen to promote the breaking of chemical bonds in the plastic’s molecular structure.)) (sometimes called pro-oxidants or pro-degradents) that can accelerate the material’s breakdown into smaller pieces when exposed to sufficient sunlight, oxygen, and/or heat.
Real world conditions, however, do not always allow for this fragmentation to happen, and oxo-degradable plastics sometimes remain intact for years when littered in the open environment, resulting in the same ecological impacts as conventional plastics (e.g. entanglement). When they do successfully fragment, oxo-degradable plastics simply undergo an expedited process of breaking into smaller and smaller fragments, contributing to microplastic pollution rather than becoming organic matter like their biodegradable or compostable counterparts.
In countries that do not have or do not enforce labeling standards, some oxo-degradable plastic companies may make misleading claims that their products are biodegradable, compostable, or good for the environment, and consumers should carefully inspect products making such claims for certification logos or oxidative additives on their labels.
Bans & Restrictions
In 2019, the European Parliament voted to ban the use of oxo-degradable plastics throughout the European Union,((Directive (EU) 2019/904 of the European Parliament and of the Council of 5 June 2019 on the reduction of the impact of certain plastic products on the environment. https://eur-lex.europa.eu/legal-content/EN/TXT/?uri=CELEX%3A32019L0904&qid=1632025768756)) citing oxo-degradable plastic’s inability to “properly biodegrade” or compost,((Oxo-degradable plastics are not compostable and are not intended for processing in industrial composting systems, making consumer understanding of terminology and how to dispose of them critical to avoid contamination of organic waste streams.)) and its negative effects on recycling processes.((European Parliament (2018, September 13), MEPs propose ways to boost plastics recycling [Press release]. https://www.europarl.europa.eu/pdfs/news/expert/2018/9/press_release/20180906IPR12112/20180906IPR12112_en.pdf)) The Australian government is also set to phase out any “plastic packaging products containing additive fragmentable technology that do not meet relevant compostable standards” by 2022.((Australian Department of Agriculture, Water, and the Environment. (2021). National Plastics Plan 2021. Australian Government. http://www.environment.gov.au/system/files/resources/a327406c-79f5-47f1-b71b-7388407c35a0/files/national-plastics-plan-2021.pdf)) Additionally, a group of over 150 businesses, industry associations, non-governmental organizations, scientists, and elected officials from around the world have endorsed a statement published by the Ellen Macarthur Foundation calling for the ban of oxo-degradable plastics.((New Plastics Economy. (2019). Oxo-degradable plastic packaging is not a solution to plastic pollution, and does not fit in a circular economy. Ellen Macarthur Foundation. https://www.newplasticseconomy.org/assets/doc/Oxo-statement-May2019.pdf))
Substituting oxo-degradable plastics for conventional plastics neither contributes to circular economic goals nor reduces plastic waste and pollution. Moreover, their inherent property to fragment into very small, but not ultimately biodegradable, pieces, makes them intrinsically dangerous to wildlife, the food web, and human health.
By design, the additives in oxo-degradable plastics make them less durable than conventional plastics, limiting their suitability for reuse and potentially reducing the quality and economic value of mixed recyclable materials when they end up in recycling systems.((Hornitschek, B. (2012). Impact of Degradable and oxo-Fragmentable Plastic Carrier Bags on Mechanical Recycling. Transfer Center for Polymer Technology (TCKT) on behalf of the European Plastic Converters (EuPC). https://ec.europa.eu/environment/ecoap/sites/default/files/forum/final_impact_of_degradable_and_oxo-fragmentable_plastic_carrier_bags_on_mechanical_recycling.pdf))((Aldas, M., Paladines, A., Valle, V., Pazmiño, M., Quiroz, F. (2018). Effect of the Prodegradant-Additive Plastics Incorporated on the Polyethylene Recycling. International Journal of Polymer Science, 1-10. https://doi.org/10.1155/2018/2474176))((Greene, J. Biobased Biodegradable and Degradable Plastics Effects on Recycled Plastics. https://www.researchgate.net/profile/Joseph-Greene-9/publication/265991203_Biobased_Biodegradable_and_Degradable_Plastics_Effects_on_Recycled_Plastics/links/556cca2708aec2268305487e/Biobased-Biodegradable-and-Degradable-Plastics-Effects-on-Recycled-Plastics.pdf))((Eunomia. (2016). The Impact of the Use of “Oxo-degradable” Plastic on the Environment. European Commission DG Environment.))
As for their impact on plastic pollution, oxo-degradable plastics are intended to reduce the buildup of plastic waste in the open environment by quickly fragmenting into smaller pieces. However, evidence suggests that in real world environments where exposure to sunlight, oxygen, and heat varies, oxo-degradable plastics often fail to fragment as quickly as intended, sometimes persisting for years as litter.((Mclauchlin, A., Thomas, N. (2012). Oxo-degradable plastics: Degradation, environmental impact and recycling. Proceedings of the Institution of Civil Engineers: Waste and Resource Management, 165(3), 133-140. https://doi.org/10.1680/warm.11.00014))((California Integrated Waste Management Board. (2007). Performance Evaluation of Environmentally Degradable Plastic Packaging and Disposable Food Service Ware – Final Report. https://www2.calrecycle.ca.gov/Publications/Download/863?opt=dln))((Eunomia. (2016). The Impact of the Use of “Oxo-degradable” Plastic on the Environment. European Commission DG Environment.))((Feuilloley, P., César, G., Benguigui, L., Grohens, Y., Pillin, I., Bewa, H., Lefaux, S., Jamal, M., (2005). Degradation of polyethylene designed for agricultural purposes. J. Polym. Environ, 13, 349–355. http://dx.doi.org/10.1007/s10924-005-5529-9))
When fragmentation does occur, the resulting small fragments and microplastics become difficult or impossible to collect, guaranteeing that the material will stay in the environment, where it can have potentially toxic effects on surrounding wildlife.((Schiavo, S., Oliviero, M., Chiavarini, S., & Manzo, S. (2020). Adverse effects of oxo-degradable plastic leachates in freshwater environment. Environmental Science and Pollution Research, 27(8), 8586-8595. https://doi.org/10.1007/s11356-019-07466-z)) Moreover, the accelerated fragmentation of oxo-degradable plastics means that microplastics are formed more quickly and build up in a shorter period of time compared to conventional plastics.((Eunomia. (2016). The Impact of the Use of “Oxo-degradable” Plastic on the Environment. European Commission DG Environment.)) A shift to oxo-degradable plastics, therefore, would result in more, not less, microplastic pollution.
Some studies suggest that this fragmentation can lead to at least partial biodegradation, that is, the breakdown of the material by microorganisms, under the right conditions.((Yashchuk, O., Portillo, F.S., Hermida, E.B. (2012). Degradation of Polyethylene Film Samples Containing Oxo-Degradable Additives. Procedia Materials Science, 1. 439-445. https://doi.org/10.1016/j.mspro.2012.06.059))((Eunomia. (2016). The Impact of the Use of “Oxo-degradable” Plastic on the Environment. European Commission DG Environment.)) However, there is no conclusive evidence that full biodegradation, i.e. final breakdown of such plastics into CO2 and H2O, occurs in the real world,((Eunomia. (2016). The Impact of the Use of “Oxo-degradable” Plastic on the Environment. European Commission DG Environment.))((UNEP. (2015). Biodegradable Plastics and Marine Litter. Misconceptions, concerns and impacts on marine environments. United Nations Environment Programme (UNEP).)) and numerous studies show that oxo-degradable plastics do not biodegrade even years after fragmenting.((Feuilloley, P., César, G., Benguigui, L., Grohens, Y., Pillin, I., Bewa, H., Lefaux, S., Jamal, M., (2005). Degradation of polyethylene designed for agricultural purposes. J. Polym. Environ, 13, 349–355. http://dx.doi.org/10.1007/s10924-005-5529-9))((Briassoulis, D., Babou, E., Hiskakis, M., Kyrikou, I. (2015). Analysis of long-term degradation behaviour of polyethylene mulching films with pro-oxidants under real cultivation and soil burial conditions. Environ. Sci. Pollut. Res., 22, 2584–2598. http://dx.doi.org/10.1007/s11356-014-3464-9))((Briassoulis, D., Babou, E., Hiskakis, M., Kyrikou, I. (2015). Degradation in soil behavior of artificially aged polyethylene films with pro-oxidants. J. Appl. Polym. Sci. 132. http://dx.doi.org/10.1002/app.42289))
In this way, use of oxo-degradable plastics would not reduce plastic pollution, and could even make the plastics crisis worse.