When it comes to the circular economy transition, plastics recycling is as much of a challenge as an opportunity. Could chemical recycling make the plastics value chain more circular whilst providing a profitable new industry branch?
Plastic pollution of the oceans, the resulting damage to wildlife, and the human health risks from microplastic have ignited public concern and heated discussions around plastic reduction. The decisions by China, Malaysia and soon Vietnam to stop imports of plastic waste — and growing public pressure — have prompted the realisation that exporting, burning and burying are not the right solutions to the smouldering plastic crisis. Global approaches are needed to deal with the predicted doubling of the global production of plastic over the next 20 years fuelled by increasing consumption, particularly in developing countries.
Under the New Plastics Economy global commitment initiated by the Ellen MacArthur Foundation, consumer brands including Coca-Cola, Colgate, H&M, PepsiCo, SC Johnson andUnilever vowed to make all their plastic packaging either reusable, recyclable or bio-degradable by 2025. In January, the global Alliance to End Plastic Waste — featuring petrochemical and packaging giants including BASF, Braskem, DSM, ExxonMobil, Henkel, Procter & Gamble, Suezand Veolia — committed to invest €1,3 billion over the next five years into innovative technology to help recover and recycle plastics waste from the land and the ocean.
The problem remains that so little of the collected plastic waste actually gets turned into new material. This is a significant loss of valuable resources to the economy, and a huge cost to the environment. In Europe, for example, of the 30 percent of plastic waste that got collected in 2016, only 31.1 percent actually got converted into new products. This is mainly because mechanical recycling — shredding into resin pellets — only works for pure streams of plastic types, such as PET bottles; composite, dirty materials usually get incinerated. As a consequence, more than half of Europe’s plastic converters are running short on suitable waste. Producers that want to use recycled material for their products cannot rely on steady supply streams of quality feedstock.
A fresh look at chemical recycling
To tackle this situation, industry is taking a fresh look at chemical recycling. The technology is not new — it has been used to turn plastic into fuel for decades. What is new is the growing market demand for high-quality plastic recyclates, due to significantly higher targets for recycled plastic in packaging products and a heightened sense of corporate responsibility.
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For lawmakers, the concern is to avoid “waste-to-fuel lock-ins.” In Europe, the revised EU waste legislation states that plastic waste can be considered as recycled only if it is not subject to energy recovery and is reprocessed into new materials that are not to be used as fuels. This definition is technology-neutral, but is complex when it comes to transforming plastics back into basic chemicals. The ultimate goal is nothing less than closing a gap in the waste-management process to seize the benefits of a circular plastic economy.
There are four methods of chemical recycling, which are substantially different in terms of waste input and obtained products:
- Depolymerisation turns monoplastic (ex: PET bottles) back into monomers, which can be re-polymerized into new PET-based products.
- Solvolysis (dissolution) is used to break down certain plastics such as expanded polystyrene (EPS) into monomers with the aid of solvents.
- Pyrolysis converts mixed plastics into tar oil, which can be cracked down and further refined for new plastics production.
- Gasification is able to process unsorted, uncleaned plastic waste and turn it into syngas, which can be used to build bigger building blocks for new polymers.
The latter two — pyrolysis and gasification — transform plastics, and most of their additives and contaminants, into basic chemicals; in theory, any kind of plastic waste can be converted. To meet the same quality standards as primary feedstock, some pre-sorting of non-organic waste or purification of the output material may be necessary. If the resulting oil and gas are used for chemical production, the final plastic products will be identical to those produced from conventional feedstock.
To this end, Air Liquide, Nouryon (formerly AkzoNobel Specialty Chemicals), Enerkem, Shell and the Port of Rotterdam are preparing a commercial-scale gasification facility to be operational in 2020. The objective is to produce syngas and methanol from organic waste that Nouryon would turn into chemical products. In addition to mixed plastic waste, the pilot plant will also be able to process biomass, diapers, rotten paper and the like.
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