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Issue 03/2022

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Highlights: Injection Moulding Beauty & Healthcare Basics: Biocompatibility of PHA Starch

Recycling Designing for

Recycling Designing for recycling of the future The issue is familiar and pressing – currently, only 9 % of plastic waste is recycled globally, the rest ending up in landfills, in incinerators (thus generating pollution), or in the environment. People want solutions. Multiple processes that fall under the umbrella of chemical recycling (also sometimes referred to as advanced recycling, chemical conversion, molecular conversion, or conversion technologies) have been proposed as solutions to recycle more plastic, but unfortunately a basic problem is that many of these technologies are currently used as pathways to turn plastics into fuels – and this is not recycling. True recycling returns materials to the manufacturing cycle; it doesn’t destroy them under the guise of producing energy (which so far, is still the status quo for chemical recycling). And there is another fundamental problem with applying any of these technologies to current plastics: toxic chemicals in = toxic chemicals out. Plastics, whether they are derived from fossil fuel or biobased feedstock, can contain hundreds of toxic additives such as plasticizers, stabilizers, flame retardants, and pigments, and may contain toxic monomers [1]. These substances pose health and environmental threats over the life cycle of the material, from production to use to disposal or recycling. Neither mechanical recycling nor chemical recycling can effectively deal with these toxic chemicals – they may be incorporated into the recycled product itself [2], or concentrated in hazardous waste if separated from the desired monomers or polymers. Chemical recycling facilities in the USA utilizing pyrolysis or solvent purification generate large quantities of hazardous waste [3]. It is important to move away from circulating the most toxic chemicals on the market, and intentionally design materials and chemicals to be safe from the start, with their end of life in mind. The European Union Chemicals Strategy for Sustainability published in 2020 works towards this goal by encouraging innovation for safe and sustainable chemicals coupled with better protections for human health and the environment through regulation [4]. Because (most) bioplastics are not derived from fossil fuels, there is significant potential for these biobased materials to be an important part of the sustainable and non-toxic materials cycles envisioned by the EU Strategy, if materials can start to evolve today to meet what is needed for tomorrow. Three of the Strategy’s key elements that are particularly relevant to recycling considerations are: 1. getting rid of the most hazardous materials, 2. encouraging chemicals that are safe and sustainable by design, and 3. creating nontoxic materials cycles. Getting rid of the most hazardous materials The EU Strategy calls for banning the most harmful chemicals from use in consumer products – those that cause cancer, gene mutations, disruptions to the reproductive or endocrine system, or are persistent and bioaccumulative. Many chemicals currently used in plastics and bioplastics would meet this criterion, including per-and poly-fluorinated alkyl substances (PFAS), halogenated flame retardants, heavy metals, and many more. If manufacturers removed these types of hazardous chemicals from materials, there would be far less concern for toxic contamination or re-circulation in recycling. Safe and sustainable by design While removing known toxic chemicals is critical, this alone is not enough. Where a function is needed, it is also key to replace known toxic chemicals with safer chemicals, not chemicals that are inadequately tested or of unknown toxicity (i.e. a “regrettable substitution”). The EU Strategy promotes a safe-and-sustainable-bydesign approach to chemicals that “focuses on providing a function (or service), while avoiding volumes and chemical properties that may be harmful to human health or the environment”. Manufacturers should use green chemistry principles to guide chemicals development and selection as a priority in product design from the outset, on equal footing with cost and functionality. This includes designing for the end-of-life, which should feed into a materials manufacturing cycle, instead of disposal (including both landfill and waste-to-energy processes). Nontoxic materials cycles Overall, current plastic product design prioritizes functionality in the use phase, with little to no consideration for the end-of-life. This disconnect is a major contributor to the plastic waste crisis. Designing for a non-toxic materials cycle means that both the recycling process and the recycled materials are free from hazardous chemicals. Chemical recycling today falls short on both these measures and is most often not true recycling. But emerging molecular technologies have the potential to deliver in this regard, such as enzymatic depolymerization of biobased polymers used to feed building blocks back into polymer production, performing true recycling [5]. These types of reactions generally do not need high heat or toxic solvents and do not generate hazardous by-products. If applied within a cycle of safer, sustainable materials without toxic additives or components, such technologies could be a part of the recycling of the future. 44 bioplastics MAGAZINE [03/22] Vol. 17

By Veena Singla, Senior Scientist Tessa Wardle, Environmental Health Intern Natural Resources Defense Council San Francisco, CA, USA Recycling Conclusion These three elements from the EU Strategy point the way towards designing materials today for a healthier, more sustainable future where both hazardous chemicals and waste are minimized, and products are safely recycled as part of a circular economy. Companies that integrate these elements into their business strategies will be wellpositioned to take advantage of related economic incentives and get ahead of regulations. The plastic pollution crisis is solvable, and recycling technologies (including certain forms of advanced recycling) are a part of the solution – but only when applied to materials that do not contain hazardous chemicals, that are safe and sustainable by design, and that feed into nontoxic materials cycles. References [1] [2] S0304389422001984 [3] [4] [5] S0167779919300897 Stay in the loop! Subscribe for free! @ Subscribe for free! @ Subscribe for free! @ bioplastics MAGAZINE [03/22] Vol. 17 45

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