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.”