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What is the future of PVC-U recycling?

2 March 2023

Jason Leadbitter, Sustainability & Corporate Social Responsibility Manager of chemicals company INOVYN, is one of the leading authorities on plastics and their impact on the environment.

We talked to him about the processes involved in recycling PVC-U frames, and how the latest recycling technology could offer a long-term solution to the worldwide problem of plastic waste.

New windows for old

Fewer than 20 years ago, the first 100% recycled PVC-U doors and windows were a proof of concept novelty that showed what could be achieved with mechanical recycling technology.

Today, in more environmentally aware times, recycled PVC-U is a common ingredient in many new PVC-U window and door lines.

So, what does the future hold for what the industry refers to as ‘post-consumer’ PVC-U? And what technologies are around the corner to help it recover, recycle and reuse even more of this valuable resource?

Rethinking the recycling process.

Mechanical recycling has been the standard technique for turning old PVC-U frames into new products for many years. It’s a relatively simple process: Old frames are broken up, cleaned, converted into tiny pellets and then melted to be reformed into new window and door profiles or other products.

Sometimes extra pigments may be added or a ‘skin’ of virgin PVC-U included to make sure the recycled frames are the same brilliant white colour. But apart from that, everything that’s in the old frames goes into making the new ones.

It works because PVC-U is made up of millions of intertwined, spaghetti-like strands, or ‘polymer-chains’ that give it rigidity and strength. (They also help prevent molten drops of plastic forming during house fires, something PVC-U windows have been wrongly accused of in the past.)

When the plastic is heated to melting point during recycling, these strands loosen but, crucially, they don’t break down as other polymers can in some other forms of plastic.

That means, when the melted plastic is reformed into new window frames, the polymer-chains can intertwine again. So the recycled frames are just as strong as the original, virgin PVC-U ones. In fact, PVC-U can be recycled up to 10 times without losing any of its strength.

The only drawback with manufacturing PVC-U frames in this way is that it needs to be free from all other types of plastics. That’s fine when the raw material comes direct from replacement window projects or factory offcuts, as it does in the Eurocell ‘closed loop’ recycling system.

But mixed waste loads, which contain many different types of plastic from all sorts of sources, are simply too costly to sort and separate and often end up in landfill instead.

That’s an awful lot of plastic going to waste every year. So now, the focus for the future is on a newly emerging technology: chemical, or feedstock recycling.

Different materials, different endings.

PVC-U is a very easy material to recycle and re-use, and the replacement window and door industry has an impressive record for recycling old frames and using them to make new ones.

Over 560,000 tonnes of what the industry refers to as ‘post-consumer’ material are recycled across Europe every year, aided by companies like Eurocell, who operate an advanced ‘close loop’ system for the recovery, recycling and reuse of PVC-U frames.

In contrast, recycling rates for timber window frames are much lower, and it’s easy to see why.

Each time PVC-U is recycled, the proportion of additives such as impact modifiers in the mixture can be adjusted to ensure it keeps its strength. Indeed, PVC-U actually gets stronger the first few times it’s recycled. Which means it can be re-processed and used to make the same products it came from, or for high-value ‘upstream’ recycling.

But the fibres in wood...

But the fibres in wood break down immediately when it’s recycled, meaning it can only be used to manufacture chipboard and other low-grade timber products or ‘downstream’ recycling. Alternatively, it can be converted into biomass fuel and burned to produce green energy.

Not that a great deal of wood frames are sent for recycling. It’s estimated up to **50% of the timber windows removed from refurbishment projects in the UK end up as landfill.

This is partly because the timber frame manufacturers have nothing like the advanced pathways for returning and recycling old frames that the PVC-U industry has, and partly because the paint, stains and preservatives in treated wood make it much harder to recycle - not mention more toxic to the environment when it begins to break down in landfill.

And aluminium?

So much for wood. Now how do aluminium window frames fare when they reach the end of their life?  

Like PVC-U, recycling rates for aluminium are impressive, reaching 90% across Europe for the construction and vehicle industries***. And, like PVC-U, aluminium can be recycled and used to make new window and door frames many times over.

The difference lies in the amount of energy consumed - and therefore emissions produced - to recycle each one.

PVC-U is reprocessed at a modest 160-220 degrees centigrade, compared to the 700-750 degrees centigrade or more required to melt down and recycle aluminium.

While aluminium companies will maintain recycling their product uses a fraction of the energy required to make it in the first place, everything is relative; aluminium production is an extremely energy hungry process, requiring huge amounts of power to extract the metal from its ore. So even the small proportion used in recycling still adds up to a hefty fossil fuel footprint.

In conclusion...

Of course, advances in manufacturing, materials technology and recycling techniques will continue to change the relative merits of ‘the big three’. And who’s to say what other miracle material will come along to challenge them in the next few decades?

One thing is certain though: PVC-U is not the poor relation regarding sustainability and recycling that it’s sometimes assumed to be. And when it comes to PVC-U, wood or aluminium, end of life will never be the end of the argument.

*Life Cycle Assessment of PVC and of competing materials. European Commission Publication



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