Materials Fill the gap,
Materials Fill the gap, not the landfill Governments and institutions have been scrambling to rectify the global environmental disaster caused by the accumulation of plastic waste. This plastic waste comes in macroscopic forms such as bottles, plastic bags, and polyester clothing. In the best-case scenario, it is regulated and dumped into overcrowded landfills or in the worst case, it escapes into the open environment as litter directly endangering the health and safety of wildlife and local populations [1]. Alarmingly an even more insidious type of plastic, ‘microplastic’, or plastic waste so small it is invisible to the eye, has been making headlines as it can be found in the water, soil, and even inside of our bodies [1]. The steps being taken to address this issue focus on banning specific single-use plastic items or their substitution with more sustainable alternatives (reusable, recyclable, or compostable). This is part of an overall shift from a linear economy to a circular economy. To accelerate this change, governments have passed their own single-use plastics bans or have committed themselves to initiatives such as the New Plastics Economy, Global Commitment led by the Ellen Macarthur Foundation (EMF) [2]. The goal is to ‘build a circular economy around plastics’ by initially setting strict goals around certain single-use plastic items for 2025. With these measures in place there is an incentive for building a future where plastics are either replaced and or are fully circular. In the meantime, there are still large gaps that need to be filled by addressing singleuse-items that fall outside of traditional packaging or consumer products. Personal protective equipment, sterile items, and chemically contaminated consumables are items that are not easily substituted with other materials as these applications require high-performance and durability that only plastics can currently provide. Additionally, these items have recyclability challenges due to contamination or are used in remote environments (such as for agricultural applications) where they cannot be efficiently collected [3]. These items are usually landfilled or incinerated, both of which do not fall under the Ellen Macarthur Foundation’s definition of circular [2]. The current COVID-19 pandemic has only exacerbated this type of waste due to the significant increase of personal protective equipment (PPE) and sterile consumables. Sources have cited that over four million tonnes of polypropylene waste from PPE have been disposed of over the course of the pandemic and will continue to grow [3]. These hard to remediate items are important and will not disappear. A solution is to develop innovative materials and circular product design. Biodegradable and compostable plastics are viable options to tackle this problem, as they have the potential to match the performance needed for these applications [4]. On the other hand, some of these plastics display incomplete degradation ultimately leading to microplastics. To elevate degradable plastics into truly sustainable and viable alternatives major improvements and innovations are needed. Scientists have been designing materials that allow rapid degradation – much more efficient than their traditional counterparts. In addition, the onset of degradation can be controlled or triggered. In recent years, triggered degradation plastics that utilise hydrolytic enzymes have created attention in the media due to their speed of degradation and broad applicability. The idea of enzymes that can degrade plastic, particularly polyesters, is not new as the entire concept of microbial biodegradation hinges on this process. Scientists managed to remove the microbe from the picture by directly mixing the enzymatic material with the plastic – a sort of trojan horse plastic composite. Under the right conditions, degradation happens from the inside out for these novel plastics. Scientists around the world are working on developing and optimizing these materials. At Scion, a Crown Research Institute in New Zealand, researchers have been exploring how to design and manufacture these materials using solvent-free thermoplastic processing techniques. Being able to thermally process them is key to ensuring their viability commercially. Day 0 Day 3 Day 8 26 bioplastics MAGAZINE [06/21] Vol. 16
By: Angelique Greene Kate Parker Scion Rotorua, New Zealand Materials One major issue to overcome when working with enzymes is that they denature when exposed to elevated temperatures outside of their optimal range of activity. However, certain solid-state commercial lipases (a type of enzyme) maintain activity in a solvent-free environment even when exposed to temperatures upwards of 130 °C [5]. This temperature range is ideal for lower melting point biodegradable plastics, meaning that the enzyme and the plastic can be compounded directly without any additional steps. To test this theory, the researchers 3D printed the enzymatic bioplastic into single and multi-material objects such as a hatching Kiwi bird (see pictures). These objects were then degraded resulting in total degradation after a 3 to 8-day period and avoiding any microplastics formation. Being able to directly compound the enzyme with lower temperature bioplastics is certainly promising and a cheaper option, however, this direct compounding technique will not work for higher melting point bioplastics. Scion is currently exploring polymeric or inorganic supports to protect the enzyme during processing with high melting point plastics. A place where high-temperature processing could make a significant impact is by giving industrially relevant but problematic bioplastics like PLA the ability to degrade faster and to completion. Complementary to this work at Scion, the French startup, Carbios (Saint-Beauzire), has been working on utilising polyester degrading enzymes developed by Novozyme (Bagsværd, Denmark) to develop novel process-scale enzymatic recycling methods that are milder and more eco-friendly than conventional chemical recycling [6]. Additionally, research groups at the University of California, Berkeley, have been looking at ways to improve the efficiency of the enzymes during degradation and investigating the mechanistic considerations of the process [7], and the Fraunhofer Institute for Applied Polymer Materials (Potsdam, Germany) has been working on processing these materials into films [8]. At the same time biotechnologists and enzymologists are working hard to engineer enzymes that are more efficient at degradation than currently available alternatives. This technology is just emerging and there are still scientitic challenges to be addressed. It will require a significant effort to get these technologies to a truly commercially ready stage. There will be no magic silver bullet to solve the issue of hard to remediate single-use plastic waste and it will take a multitude of approaches like the ones mentioned above and more traditional approaches such as consumer education and improvements to existing recycling technology. www.scionresearch.com References: [1] The Royal Society Te Apaarangi. (2019, July). Plastics in the Environment Te Ao Hurihuri – The Changing World. https://www.royalsociety.org.nz/ assets/Uploads/Plastics-in-the-Environment-evidence-summary.pdf [2] Ellen Macarthur Foundation. (2020, February). New plastics economy global commitment commitments, vision and definitions. https:// www.newplasticseconomy.org/assets/doc/Global-Commitment_ Definitions_2020-1.pdf [3] Nghiem, L. D., Iqbal, H. M. N., & Zdarta, J. (2021). The shadow pandemic of single use personal protective equipment plastic waste: A blue print for suppression and eradication. Case Studies in Chemical and Environmental Engineering, 4, 100125. doi: https://doi.org/10.1016/j. cscee.2021.100125 [4] European Environmental Agency. (2021, April). Biodegradable and compostable plastics challenges and opportunities. https://www.eea. europa.eu/publications/biodegradable-and-compostable-plastics/ biodegradable-and-compostable-plastics-challenges [5] Greene, A. F., Vaidya, A., Collet, C., Wade, K. R., Patel, M., Gaugler, M., . . . Parker, K. (2021). 3D-Printed Enzyme-Embedded Plastics. Biomacromolecules, 22(5), 1999-2009. doi:10.1021/acs.biomac.1c00105 [6] Enzymes. (2021, April 9). Carbios. https://www.carbios.com/en/enzymes/ [7] New process makes ‘biodegradable’ plastics truly compostable | College of Chemistry. (2021, April 21). Berkeley College of Chemistry. https://chemistry.berkeley.edu/news/new-process-makes- %E2%80%98biodegradable%E2%80%99-plastics-truly-compostable-0 [8] Fraunhofer Institute for Applied Polymer Research IAP. (2021, June 1). Enzymes successfully embedded in plastics. Press Release. https:// www.fraunhofer.de/en/press/research-news/2021/june-2021/enzymessuccessfully-embedded-in-plastics.html Magnetic for Plastics www.plasticker.com • International Trade in Raw Materials, Machinery & Products Free of Charge. • Daily News from the Industrial Sector and the Plastics Markets. • Current Market Prices for Plastics. • Buyer’s Guide for Plastics & Additives, Machinery & Equipment, Subcontractors and Services. • Job Market for Specialists and Executive Staff in the Plastics Industry. Up-to-date • Fast • Professional bioplastics MAGAZINE [06/21] Vol. 16 27
