editorial Plastic upcycling Plastic waste is a serious matter of concern due to its disruptive impact on the environment. While disposal and reclaim strategies represent the frst lines of intervention to solve this problem, upcycling options based on catalytic transformations will eventually be necessary to reconvert enormous quantities of such material.

ecent estimates suggest that 4.8 to is just a small part of the globally produced in single use plastic bags — into liquid 12.7 million metric tonnes of plastic plastic trash — the tip of the iceberg. One hydrocarbons with a narrow molecular may have entered the ocean in 20101. should also consider the plastic reclaimed weight distribution, which can be applied R 5 Only part of such waste can be tracked from municipal solid waste, which is even as lubricants and waxes . In this case, the within the ocean’s garbage patches or on larger in volume and is usually destined to desired selectivity could be achieved by coastal areas in the form of buoyant plastic end up in dumps or landfills. What to do tuning the structures of Pt nanoparticles objects. In fact, a large fraction of such waste with all this garbage? Can we make good supported on SrTiO3. has a tendency to degrade and settle below use of it as raw material? Conventional Plastic conversion is not a restricted the sea surface layer, where it can be further recycling strategies based on mechanical area of research, if one looks at the ingested by marine organisms and finally methods or incineration are downcycling diversity of possible approaches. Besides accumulates in the ecosystem2. The related approaches: they usually lead to products the heterogeneous or organocatalytic environmental and health threats are with lower values than the corresponding methods mentioned above, biocatalysis is well known. original plastic (often low-quality plastic) also contending for its place. Enzymes, in While the use of plastic is integral to or inefficient energy recovery in the form of fact, have shown very interesting activity modernity and has brought enormous heat3. However, plastic waste can be seen as in degrading plastics. Recently, Japanese benefits to different sectors including an important feedstock for the preparation scientists were able to isolate a specific food packaging, medical devices, and of value-added materials, and here catalysis bacterium from a microbial community telecommunications, it is obvious enters the scene. localized in the vicinity of a PET recycling that current disposal and end-of-life plant that features two enzymes competent management strategies are no longer “However, plastic waste can for the hydrolysis of PET and its related sustainable. In order to provide a solution, be seen as an important intermediate — mono(2-hydroxyethyl) a number of commendable initiatives terephthalic acid — respectively6. Such have been kicked off, at least when it feedstock for the preparation families of enzymes are expected to comes to plastic accumulated within of value-added materials, play an important role in the development seas and waterways. A few days ago, for of practical upcycling schemes in instance, the Ocean Cleanup — a private and here catalysis enters the the future. environmental organization — announced scene.” The sceptical reader may at this point the intention to deploy automated plastic think that plastic reclaiming, recycling collection units in heavily polluted rivers Catalytic recycling of plastic is not yet and upcycling has little hope due to following successful trials in Indonesia employed on a large scale, but has certainly economic constrains, especially in light and Malaysia. The organization has shown great promise. Thermal treatment of of the current use once and discard claimed a removal capacity per unit of reclaimed polyethylene terephthalate (PET) paradigm. However, feasibility studies 50,000 kg per day so far, complementing in the presence of a commercial guanidine have shown that even employing existing its ongoing efforts to reclaim plastic waste catalyst and excess amounts of ethylene technologies — that is, mechanical from the oceans via specialized collection glycol, for instance, leads to the recovery of recycling and standard catalytic pyrolysis systems. And this is just one of a number bis(2‐hydroxyethyl) terephthalate4. Thus, — the economic gain may be significant. of efforts targeting plastic waste removal. such a chemical can be newly employed McKinsey has recently published a study In fact, different technologies are under for the preparation of high-quality PET. suggesting margins of around US$60 investigation — see for instance the Clearly, the nature of the catalytic process billion for the plastic and petrochemicals Great Bubble Barrier — but also different depends on the chemical properties of sector if recycling based on existing water environments prone to plastic the plastic to be transformed. Therefore, technologies would be applied to 50 accumulation are being targeted, like approaches that are closer to the refining per cent of the plastics worldwide — marinas (for example, the Seabin Project). of crude oil may be necessary in the case incidentally, no more than 12% is Moreover, the form of organization of more inert macromolecules, like for currently valorized. can vary, so next to business-oriented instance polyolefins. When conducted in Developing advanced and more- approaches — 4ocean, for example — one a non-selective fashion, such processes efficient catalytic conversion schemes for can find consortia like the Alliance to End can afford a mixture of hydrocarbons the upcycling of plastic waste is therefore Plastic Waste, a not-for-profit organization that can find application as alternative an exciting opportunity for academic working in partnership with several fuels. However, increasing the degree of practitioners, and it is expected to further multinational companies linked to the selectivity, value-added chemicals can increase the profitability of the sector. plastic value chain. be targeted. A recent example has shown Building blocks, monomers, and fine If these initiatives are successful, and we for instance the possibility of using chemicals obtained in this manner can all hope so, the amount of collected marine hydrogenolysis to convert high-molecular- then be supplied to the polymer and fine litter is expected to be fairly large. But this weight polyethylene — typically found chemical industry, according to the circular

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economy principle. At Nature Catalysis, Published online: 14 November 2019 2. Lebreton, L., Egger, M. & Slat, B. Sci. Rep. 9, 12922 (2019). we look with excitement at the future of https://doi.org/10.1038/s41929-019-0391-7 3. Rahimi, A. & García, J. M. Nat. Rev. Chem. 1, 46 (2017). 4. Fukushima, K. et al. J. Polym. Sci. A 49, 1273–1281 (2011). this area, where catalysis once again has 5. Celik, G. et al. ACS Cent. Sci. https://doi.org/10.1021/ the possibility to contribute to a more References acscentsci.9b00722 (2019). sustainable future. ❐ 1. Jambeck, J. R. et al. Science 347, 768–771 (2015). 6. Yoshida, S. et al. Science 351, 1196–1199 (2016).

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