Chemical Recycling of Plastic:
Waste No More?

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 and Unilever 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, Suez and 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.

Waste not, want not

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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.

A hurdle race

Chemical recycling through gasification still has a number of hurdles to take before crossing the finish line. Firstly, gasification plants are built at larger scale than pyrolysis, which means that the initial hurdle for investment is particularly high. Next is the dependency on waste streams that imply logistical costs such as collection and transport, followed by the syngas’ fluctuating flowrates and varying compositions on the gas grid of a chemical production complex.

Pyrolysis has its challenges, too, but due to their smaller scale, it has been easier for companies to keep some pilot facilities running. Even though pyrolysis is capable of handling any type of organic material, non-organic materials such as metals, glass fibers, halogens and often PET need to be removed from the input stream, ideally before the process or through purification of the pyrolysis oil afterwards. Remaining non-organic pollutants represent a cost factor, making ocean litter unviable as an input material, and adding problems such as massive water consumption for rinsing.

Room for growth

But soon, even food-grade plastic could be commercially produced from pyrolysed plastic waste. At the end of 2018, BASF with several partners announced the development of refrigerator components, insulation panels and even mozzarella packaging that consist of polymers generated from such pyrolysed plastic waste. In this ChemCycling collaboration project, waste operators deliver mixed plastic to technology providers for the pyrolysis procedure. BASF then uses the generated naphtha to produce high-quality plastic material that downstream customers use in their final products.

BASF project lead Stefan Gräter states that chemical recycling provides a valuable cleaning function in a circular economy resulting in secondary materials with “virgin” properties. Even under the optimistic assumption that packaging products could be re-designed to a large extent, mechanical recycling would still struggle to meet the required quality standards. Contaminants and additives could be accumulated in the material over several mechanical recycling cycles and might lead to poor product performance or even health risks.

“From this perspective, chemical recycling is a complementary option to established recycling and waste management processes,” Gräter argues. “The objective is to find technology solutions for the type of waste that is not suitable for mechanical recycling.”

To bring it to an industrial scale, chemical recycling needs to strike a balance between economic viability, regulatory compliance and environmental impact. When it comes to the latter, gasification of mixed plastic waste and pyrolysis of sorted plastics yield superior CO2-reduction scores than incineration with energy recovery, according to a recent study by Dutch independent research and consultancy firm CE Delft.

From a business point of view, McKinsey sees “opportunities to build a new and profitable branch of the industry based on recycled plastics” that might represent a profit pool of nearly €50 billion per year worldwide by 2030. Under a scenario where much larger quantities of plastic waste are routed for reuse instead of going to landfill and incineration, they see a “potential for chemical companies to transform two areas: polymers produced from mechanical recycling, and the whole field of pyrolysis and chemical recycling of used plastics Projecting a step further, it’s possible to imagine a wholly new configuration of petrochemical and plastics plants.”

The true potential for chemical recycling to become profitable depends on the sufficient supply of suitable plastic feedstock, and the further development of pyrolysis and gasification technologies to produce high volumes of recyclates with consistent quality at a competitive price. But reaching that potential also depends on conducive regulatory framework. At a policy briefing between stakeholders and European policy makers, EU Environment Commissioner Karmenu Vella emphasized the Commission’s intention to investigate further incentives and regulatory measures to increase the recyclability of plastics and make it a valuable resource. According to Vella, improved sorting and recycling techniques can also contribute to this objective: “The Commission is eager to learn more about chemical recycling.”

It is often said that circular approaches have to be systemic, and plastics are no exception. Scaling a systemic solution towards a circular plastics economy will require a combination of complementary technologies and collaboration between the different parties of the value chain, without favoring one over another. From this perspective, chemical recycling, despite its challenges, seems to have an important role to play.

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