Chemicals of concern: Overhaul urgently needed to fix 'failed' plastic recycling systems

Jun 06, 2024

A marine biologist specialising in micro-plastics looks at sea sample taken from the Mediterraneean Sea as part of a scientific study about microplastics damaging marine ecosystems, near Villefranche-Sur-Mer, on the French Riviera. REUTERS/Eric Gaillard

July 5 - Recycling is promoted as a solution to the plastics crisis engulfing humanity, but despite all the pledges to use more recycled material, it still only makes up a tiny fraction of the feedstock for plastics manufacture, and just 9% of plastics are ultimately recycled.

There are two imperatives for improving on this: cutting the greenhouse gas emissions associated with plastics manufacturing – put at 3% of global emissions – and ending waste.

But recycling plastics is not straightforward, and many polymers can’t easily be transformed back into their building blocks for a closed loop. As a result, they are burned, landfilled or dumped.

In June, negotiators working to agree a global plastics treaty met in Paris to discuss measures to end plastics waste, ranging from cutting production to waste management. Not unsurprisingly, the plastics industry thinks measures should be taken downstream, but as Yoni Shiran, who leads on plastics for consultancy Systemiq, puts it: “There's a wide recognition, certainly for most countries, that we need to be holistic in this approach. The solution here is much more complex than any one part of the value chain, or any one solution, or any one country.”

Shiran co-authored a U.N. Environment Programme report ahead of the negotiations that proposed a complete systems overhaul to eliminate problematic and unnecessary plastics, expedite reuse and recycling and encourage sustainable alternatives. Such shifts could cut the outflow of mismanaged waste by over 80% by 2040, the report said, but they require strong and enforced global regulation – something a business coalition of more than 80 organisations has called for. A “high ambition coalition” of governments, now numbering 60, has committed to developing a legally binding instrument to address the whole lifecycle of plastics.

Plastics get labelled by polymer type, such as the ubiquitous PET (polyethylene terephthalate) used for water bottles, but they’re actually a complex mixtures of chemicals that can include processing aids, colourings, flame retardants and plasticisers, along with unintentional additions during manufacturing or use that can impact recycling.

Activists hold a banner as Greenpeace International unveils an art installation by artist Benjamin Von Wong, ahead of the four-day summit of the United Nations Environment Programme on reducing plastic pollution, in Paris, France May 27, 2023. REUTERS/Michaela Cabrera

PET trays, for example, can’t be put in the same recycling stream as PET bottles because they contain a wider range of chemical additives. Mixed layers of different plastics can’t be recycled because they resist separation.

The constituents of plastics are a closely guarded secret that requires detective work to unravel. At present a team at the U.S. National Renewable Energy Laboratory (NREL) is trying to identify additives in over 20 commodity plastics.

Other researchers have identified upwards of 10,000 chemicals that may have been used in plastics production. Aside from their effect on recycling, we’re also coming to realise that many impact the environment and human health, because they can leach out during the plastics lifecycle. These “chemicals of concern” can disrupt hormones, cause cancers and poison humans and other organisms. But the science is evolving, and safe levels (if any) aren’t clear. Even where the science is beyond doubt, such as on persistent organic pollutants (POPs) regulated under the Stockholm Convention, some are exempted for use in plastics.

Shiran suggests that ultimately legislation will be needed to force transparency around the chemicals used, including processes and volumes, as well as to proscribe unsafe chemicals. “Many of the companies who are selling the stuff don’t know, exactly. So, they're also asking about regulations. Sometimes (they’re) asking people at Systemiq or others, ‘please tell us which chemicals of concern should we just phase out of our supply chains and which not’, because they're confused.”He adds: “It's all a massive confusion, partly maybe even intentional confusion, because some people benefit from this confusion.” Getting a definitive list of substances to be banned is going to be difficult ahead of a treaty next year, but an evolving list could be updated over time as we learn more about what to restrict.

A new report from Greenpeace highlights research that concludes that toxicity can build up in recycled plastics, either through contamination or as a result of the recycling process itself. The Organisation for Economic Co-operation and Development (OECD) has begun to look at the chemical content of recycled plastics to assess what happens when different materials are mixed and whether additional chemicals are introduced during use.

Bottles made from PET on a conveyor at a recycling plant in Switzerland. REUTERS/Arnd Wiegmann

The automotive industry – a major user of plastics – is possibly the farthest forward in understanding the materials used in manufacturing, with an International Materials Data System and a global database of hazardous materials.

When it comes to the plastics industry, an umbrella body, the International Council of Chemical Associations (ACCI) is developing a database of additives that will detail applications and existing scientific assessments. It also plans a risk assessment framework for additives. The aim is to have both ready by the end of treaty negotiations next year. The work will be shared with regulators.

There is a big difference between a material being theoretically recyclable and being designed to be recycled in practice. The Ellen MacArthur Foundation suggests that for recycling to happen at scale, at least 30% of a material needs to be recycled across a population of 400 million people (about the size of the EU).

That means streamlining the polymers we use to get scale, says Shiran. “Right now, it's the Wild West – people use any polymer, any additive, any colour, any size, any shape.”

The Consumer Goods Forum has developed “golden design rules” such as using only transparent or uncoloured PET, reducing plastic over-wraps and removing PVC, fibres and aluminium foil from flexible packaging, while the OECD has developed design guidance for manufacturers, including additive considerations.

At a recent webinar, Ann Tracy, chief sustainability officer at Colgate-Palmolive described how it opted for HDPE (high density polyethylene), commonly used for plastic milk bottles and which can be recycled (potentially up to 10 times) to replace the multiple layers of different plastics used to make its toothpaste tubes. “It took quite a few years to get it right, because (HDPE is) a rigid plastic, and we had to make it feel like a tube,” Tracy said.

An employee works on a vehicle at a GM assembly plant in Kansas. The automotive industry has an International Materials Data System and a global database of hazardous materials. REUTERS/Dave Kaup

Significantly, Colgate-Palmolive has shared the technology with competitors, with the aim of having three out of four toothpaste tubes recyclable by 2025.

Ideally, plastics would be mechanically recycled, which means they are broken down and reformed into pellets for processing back into plastic. It’s the least expensive process in terms of infrastructure and energy requirements. Researchers at NREL find mechanical recycling of the most widely consumed polymers, including PET and HDPE, comes out ahead of chemical processes, in terms of economics and environmental impact, on one cycle.

But there are quality implications, with many plastics being “downcycled”, and material losses including in the form of microplastics, which get washed into watercourses.

And even PET, which in theory can be mechanically recycled many times, isn’t. In Europe, just 17% of PET bottles put on the market end up as recycled content in new bottles. Far more ends up in textiles, which will not be recycled. Consultancy Eunomia estimates the recycled content of PET bottles could improve to 75% with greater use of deposit return schemes, encouraging manufacturers to switch to clear PET, and by making closed loop recycling a priority.

The industry has been investing in so-called “advanced recycling” techniques of pyrolysis and gasification, which use high temperature and pressure. These require large amounts of energy and emit greenhouse gases and pollutants, while the output typically doesn’t get used to make new plastics. The NREL researchers assessed them as having 10-100 times the economic and environmental impact of virgin polymer production.

In May, seven chemicals companies in the World Economic Forum’s Low-Carbon Emitting Technologies initiative –­ BASF, Covestro, Dow, Mitsubishi Chemical, SABIC, Solvay and LyondellBasell – signed an agreement with the Dutch independent research organisation TNO to establish an R&D Hub for Plastic Waste Processing. The hub will focus on developing new technologies for waste processing with a lower CO2 footprint and greater levels of plastic waste recycling.

U.S.-based PureCycle will be producing resin at its polypropylene recycling plant in Ohio. PureCycle/Handout vie REUTERS

The most promising chemical recycling processes are only now coming out of the lab. But “there's no one technology to rule them all. All of them have trade-offs, all of them might be good for one thing, but not so good for another,” says NREL lead researcher Taylor Uekert. “We need to collaborate, to figure out how we can most optimally combine these technologies to tackle the problem.”

Some solutions are emerging. In June, U.S.-based PureCycle was due to begin testing the first resin produced at its polypropylene recycling plant in Ohio. The first off taker will be Proctor & Gamble, whose scientists developed the solvent technology.

PureCycle estimates its process uses 79% less energy and will produce 35% fewer carbon emissions than for new polypropylene production. Its solvent is recovered and re-used. Crucially, the process doesn’t break down the polymer chain, but just how many times the resin can be recycled depends on what happens in subsequent processing.

Two European firms are focused on returning PET to its original building blocks for repeated recycling from PET bottles or textiles without losses in quality. France-based Carbios has developed an enzyme process to break down the polymer and aims to have the first industrial scale plant in operation in 2025, with backing from Indorama Ventures, a recycled PET resin producer.

Carbios says its process results in a 51% reduction in carbon emissions compared with the manufacture of new PET. Dutch firm Ioniqa has built a 10,000 tonne plant to demonstrate its solvent technology, which turns all types of PET applications back into the monomers. It claims the process emits 75% less emissions than manufacturing PET from oil. Ioniqa is working on expanding its process to other plastics.

Recycling alone can’t solve the plastics crisis. As UNEP’s report makes clear, other necessary steps involve eliminating problematic and unnecessary plastics, as well as avoiding the use of plastics through re-use or refill models. Streamlining the types of plastics that remain would generate economies of scale as well as make sorting for recycling easier. That would also keep the carbon locked up if the industry is to meet its climate obligations.

This article is part of the latest issue of The Ethical Corporation magazine, unpacking the plastic waste epidemic. Download a free copy here

Angeli Mehta is a science writer with a particular interest in the environment and sustainability. Previously, she produced programmes for BBC Current Affairs and has a research PHD. @AngeliMehta