Closing the polystyrene recycling gap

Over the past few years, the status of polystyrene has gradually been shifting: from its reputation as an unrecyclable pollutant, it is now gaining recognition as an ‘infinitely’ recyclable, valuable resource that is ‘made for recycling’. A new plant in Terneuzen, the Netherlands, opened in June that is demonstrating the circular potential of recycled polystyrene foam.

PolyStyreneLoop is an extraordinary project, both because of the way it has been organised as well as because it successfully, efficiently, and sustainably provides a solution to a very compelling, specific problem. The construction and opening of the plant in June represented the culmination of years of discussion, negotiations, development, and sheer hard work. Sustainable Plastics visited the site on 14 June, just two days before the official opening and met with Lein Tange, one of the directors at PolyStyreneLoop and Alix Reichenecker, Circular Economy Manager.

The plant has been built to recycle only one type of product: polystyrene foam insulation boards from demolition waste. These foam boards, made from both extruded (XPS) polystyrene foam and from expanded foam polystyrene (EPS) are known for their outstanding insulation and shock absorbing abilities.

The main application for EPS is packaging rather than insulation. And while a great deal of EPS packaging is already quietly being recycled, the situation for XPS and EPS demolition waste is completely different. There is a gap here that needed to be filled, according to Lein Tange, which is precisely what this project will do: by turning an unrecyclable product for the first time into a valuable circular plastic.

The PSLoop plant will initially mainly process EPS but will start to handle XPS towards the end of this year.

XPS is produced using a different blowing agent than EPS. The material has a closed cell structure and is often stronger, with a higher mechanical performance and a density range of about 28–45 kg/m3. It is resistant to rotting, highly pressure-resistant, and has long been preferred for insulation purposes. The issue around both EPS and XPS demolition waste is not the foam itself, but the legacy additives incorporated in the material, among which the flame retardant HBCD.

For many years, the flame retardant of choice for applications in the construction industry was hexabromocyclododecane, or HBCD, a product developed in the 1960s. Effective at low levels, it was long considered the best solution. However, due to health and environmental concerns, HBCD is now considered a restricted substance.

In 2013, the substance was classified as persistent organic pollutant (POP) under the UN Stockholm Convention, which meant that all countries signed up to the treaty were required to eliminate its use, manufacture, and importation. The sunset date for HBCD in Europe was in 2015. However, due to the long service lives of products where HBCD has mainly been used, there is still a huge number of polystyrene foam insulation boards containing HBCD to be found in buildings everywhere.

According to Lein Tange, who is the Sustainability Director at ICL-IP, next to acting as director at PolyStyreneLoop, it’s a big enough challenge: “Over the past 40 years, for the most part, only one type of flame retardant has been used, simply because it was the most effective. Normally speaking, you need to add 10-15 percent of a flame retardant to the compound; with HBCD you only need a half to one percent. That was the main advantage.”

The upshot is that some 100,000 tons of foam waste from demolition sites are generated each year. The waste must be treated with care, to ensure no leakage occurs into the environment. As neither HBCD-containing XPS nor EPS can be recycled mechanically, it is mainly disposed of today through controlled incineration.

Tackling the problem

“The idea for the development of a solution to the problem is one that had been simmering for years,” said Tange.  In 2015, a number of parties who had been working on the problem separately came together to see whether the challenge of HBCD could be tackled. “We had our first meetings in 2015, in the offices of ICL,” he said. These parties included the European EPS Industry, Dutch national and provincial authorities, and EPS recyclers, as well as another main player in the project: Jan Noordegraaf, the former managing director of Synbra Technology and now co-director at PolyStyreneLoop B.V. “The combination of Jan’s network and my network, together, proved strong enough to set the project in motion.”

The two were given a mandate to build a 3000 t/pa plant that would demonstrate the technical and economic feasibility of PS foam recycling. The plant was to be built next door to ICL, a producer of flame retardants, and to be targeted wholly at the recycling of the bromine derived from demolition waste.

“No such plant existed as yet in the world ,” said Tange.

The two were pursuing an additional goal, as well. They sought not only to recycle the bromine, but to close the loop for both polystyrene and for bromine. In other words, their idea was to recycle the polystyrene into reusable polystyrene for the production of new insulation foam, to extract the HBCD and supply this to the bromine recovery unit operated by next-door neighbour ICL, where  the bromine, would be extracted and reused.

“So, it’s actually upcycling: we are using the same molecule to make the same product that it originally derived from,” said Tange.

Together with Jan Noordegraaf, he approached the Rabobank for funding for the project. The bank was agreeable, but also advised them to structure the project as a cooperative.

Circular Economy Manager Alix Reichenecker explained: “So now, with the help of the bank, we are structured as a cooperative, with over 70 members and supporters. The cooperative was established in 2017 - a cooperative with a limited liability under Dutch law. That was the start of the project. Our members are from the entire value chain, from raw materials and flame retardant producers to converters and machinery manufacturers. Construction of the plant, which is powered completely by electricity generated by wind power, kicked off 16 December 2019. We built it in a year-and-a-half, almost to the day.”

The right solution

The technology that the PolyStyreneLoop project opted for is based on the concept of selective extraction, known as the CreaSolv Process. The CreaSolv Process was developed around two decades ago by CreaCycle GmbH and the Fraunhofer IVV institute in Freising, Germany.

The idea took hold that this process could offer a solution for managing the foam waste stream deriving from demolition and renovation activities.

“This is the first time the technology is being applied on such a scale,” said  Alix Reichenecker. “This factory will produce 3 tons a year – that’s to test the economic viability.”

And, she emphasised, the process is a physical one. “It is not chemical recycling, although people often think it is. It’s a physical process, in which the polystyrene is dissolved.

She explained that, in simple terms, the factory is much like a big washing machine. “You throw in the dirty clothes, with the detergent -the  CreaSolv solvent - and what come out is clean polystyrene. The polymer chain stays whole and intact. This makes it a physical process rather than a chemical one.”

“Compared to incineration, the process has a >50% smaller carbon footprint according to the LCA that was conducted, because of the energy needed for incineration,” said Reichenecker. Allowing for the effect of wind power, it will come close to 70%.

Where do the boards  that are recycled at the plant come from?

“The feedstock comes from demolition projects and a collection system is now being established -  we have collection points, or HUBs, in Germany and we are setting these up in the Netherlands as well,” said Reichenecker. “The EPS is separated from the other waste at the demolition site, and taken to one of PolyStyreneLoop’s HUBs, where dirt and impurities are removed. The waste is then compacted, reducing the volume by a factor of 20, and transported to us.”

At the plant, the compacted waste is first shredded, after which it is fed into the plant to be recycled. It then first undergoes a dissolution step.

“In the first step, it is dissolved, but still contains all the other additives and substances that were in the waste – we expect about 10 weight percentage contamination,” she said. This is then filtered.

An anti-solvent is added, which transforms the polystyrene into a gel, allowing over 99% of the polystyrene to be recycled. The gel is separated out, while the HBCD remains behind in the solvent. This is distilled, after which the solvent is recovered for reuse.

The HBCD  is then taken to ICL’s bromine recovery unit, where the bromine is recovered.   

“The polystyrene gel is dried, extruded into Loop-PS  - our end product - and stored in the silos at the back of the plant. This is what we sell to the members of our cooperative. The pellets are light grey,” said Reichenecker. “Our members process these pellets into boards that offer the exact same properties as EPS from virgin material.”

The process, added Lein Tange, also eliminates any shorter polymer chains resulting from UV damage. “So, what is left is really only very high-quality polystyrene. The market is waiting eagerly for the output of our plant, as are the cooperative members,” he said.

Next to HBCD, there are other contaminants that are also eliminated during the process. Besides HBCD, old XPS (extruded polystyrene) also contains, for example, the (H)CFCs used as blowing agents in the production of XPS, typically HFC-134a. While an efficient blowing agent, this chemical belongs to the group gasses known as of fluorinated greenhouse gases - f-gases – that are known to have a relatively high global warming potential. HFC-134a has a global warming potential of 1,430, meaning that over 100 years, it traps 1,430 times as much heat as carbon dioxide does. The EU strongly regulates the use of these gasses as an attempt to reduce the environmental impact. Today, in Europe, XPS is foamed with CO2 or a combination of CO2 and organic blowing agents; however, the EPA in the USA still permits the production and use of special blends containing (H)CFCs as blowing agents for XPS.

We expect that in November, we’ll also be starting to capture this substance,” said Reichenecker. “The problem there is that as soon as XPS board breaks, these gases are released. We are currently engaged in testing a pre-treatment step here, on location  - the uncompacted XPS boards are delivered to us, we shredder and compress them, during which the gasses are released but we do this in a vacuum. The captured gasses are supplied to a third party, for destruction. We are left with gas-free XPS which we can then proceed to process. The quantities are relatively small  - the gasses are condensed in cylinders, transported to Germany and destroyed.” The pre-treatment step, she added, has proven to exceed the 95% removal efficiency for (H)CFCs stipulated by the Montreal Protocol.

Bromine recovery

The bromine in the HBCD is recovered for reuse by ICI, as well. “In new flame retardants,” said Tange. However, the bromine-based flame retardants produced today are ‘a whole different story’ from the previous generation of flame retardants. Those, he said, including HBCD, were additives; the new flame retardants are built into the polymer with long polymeric backbones that provide the flame-retarding benefits of bromine.

Moreover, bromine is not the problem, he explained. Bromine is used in many ‘invisible’ applications. It’s an ingredient in cough syrup for children, but it’s also used in the printed circuit boards used in electronic devices, and in cars, where it functions as a flame retardant. It’s used in as a drilling fluid in oil drilling operations, in tire production, in water purification – bromine is used in a much broader range of applications than most people are aware of.”

With HBCD, he continued, what has happened is that as time went by, we gained experience and knowledge that we didn’t have before. “Previously, we weren’t able to measure the leakages into the environment the way we can today, while of course, it was there. Back then, the analyses looked at milligrams per kilo. Today, we’re talking about nanograms and picograms. With the ban on HBCD, we are now acting on the knowledge available to us today.”

An important discussion in that context is the amount of HBCD that the end product produced by PolyStyreneLoop is permitted to contain. As Alix Reichenecker pointed out, while almost all the HBCD is eliminated, a tiny bit always remains behind. “We are allowed to re-use the recycled polystyrene if the UTC, the Unintentional Trace Contaminant, limit value is under 100 ppm. Discussion arose as to whether this should be under 10 ppm, instead. However, in that case, recycling would not be possible. As the EU has committed to reaching 10 million tonnes of recycled plastics used in products by 2025, it is unlikely this limit will be tightened.”

Circular economy

A question that is often asked, said Tange, is whether the project is ‘economic’ – do the benefits outweigh the costs? The answer is less straightforward that it would seem, especially when the goal is circularity.

“So, sometimes you have to look at ‘economic’ in a different way. What does it cost to send the material for incineration? How to value the image boost that comes with using sustainable material ? Or disposing of waste in a sustainable way – after all, people pay to dispose of their material with us. Or the incentives offered for using sustainable board?” he asked.

The amount of pressure and legislation aiming to stimulate the transition to the circular economy is increasing steadily, as target dates start to approach. “As an industry, we pledged to have 10 million tons of recycled material in the market by 2025. To make that happen, we must start today.”

The present PolyStyreneLoop plant will help the producers of EPS and XPS to meet their commitments. Moreover, the cooperative is already looking at the possibility of  a second plant. “We hope to build a 12-thousand-ton/pa plant once the demo plant is up and running in the coming years. In the future, we could use the existing demo plant to investigate the recovery of other additives – for example, from automotive and electronics waste, that could also be extracted using this technology,” said Tange. “With that plant, and perhaps even a third one, we’ll meet our European recycling commitment and be able to fulfil EUMEPS’  - the European association for EPS - voluntary pledge.”