Do you ever wonder what happens to the bottles and jars you put out in the recycling every week?
Maybe they鈥檙e made into new bottles and jars 鈥� maybe not. Who knows? Who even cares?
For most people, recycling is something we entrust to others once we鈥檝e done our bit and handed the material over.
But for the demolition industry, recycling is hard-wired into the business model.
Demolition contractors have traditionally earned a proportion of their income from scrap metal sales 鈥� the fluctuating price of scrap steel can mean the difference between profit and loss for some companies.
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But other materials are also recycled these days, though not necessarily for profit, and every demolition site will have some method of segregating these materials: timber into this skip, plasterboard into that one, masonry into another and so on.
Just like domestic bottles and jars, building glass from windows and doors, can also be recycled. But very little of it currently goes back into the production of more plate glass.
According to Richard Calcutt, technical project manager for closed-loop recycling at glass manufacturer Saint-Gobain, less than 1% of all post-consumer float glass in Europe is currently recycled as new float glass.
Calcutt explains that there are three types of crushed glass waste 鈥� known as 鈥榗ullet鈥� 鈥� that can be recycled. The first is 鈥榠nternal cullet鈥�, the material left over from Saint-Gobain鈥檚 own production process. This can be fed straight back into the production line.
The second category is pre-consumer cullet, the offcuts and trimmings returned to Saint-Gobain by its manufacturing customers, such as window companies.
And the third category is post-consumer cullet, the glass from windows, doors and panels recovered from the built environment during demolition or dismantling.
It is this material that is most difficult to process for recycling, which is why much of it still treated as waste.
Between 300,000 and 700,000 tonnes of glass a year is sent to landfill or 鈥榙own-cycled鈥� 鈥� in other words used for aggregate, fill or another low-value application.
Saint-Gobain is working to change this with its 鈥淕lass Forever鈥� initiative, launched in 2019. This scheme 鈥� described by the company as its 鈥渃ircular economy approach to sustainability鈥� 鈥� involves partnering with customers to collect and sort post-consumer glass from demolition sites and window-replacement projects.
The glass is then returned to Saint-Gobain鈥檚 float-glass factory in Eggborough, near Goole, where it is crushed to produce cullet, which can be re-manufactured into new float glass.
Of course, cooperation with customers in the field is key to making this arrangement work, and Saint-Gobain has been busy enlisting partners from the construction and waste management sectors in order to create a network for efficient and safe glass recovery.
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One of those partners is Berkshire-based General Demolition, which since 2021 has been exploring the potential for increasing the amount of arisings that can be reused and recycled.
鈥淭raditionally, we have never sent glass to landfill,鈥� says General Demolition director George Stainton. He says that the company has been sending up to 200 skip-loads of glass a day to its yard in Walton on Thames from where it is then taken to Tilbury to be crushed by a specialist recycling firm.
This conventional method of recycling 鈥� just like the domestic kerb-side collections 鈥� usually means down-cycling: crushing the glass for low-value use. The arrangement with Saint-Gobain is quite different in that General Demolition knows that the glass it recovers from its site will be remanufactured.
鈥淭his is a direct loop 鈥� we鈥檙e closing the circle,鈥� says Stainton. 鈥淭he glass goes straight back to Saint-Gobain to be made into new float-glass.
鈥淲e do essentially the same thing with British Gypsum for our waste plasterboard,鈥� he adds.
Since launching its new sustainability strategy in 2021, General Demolition has established numerous partnerships with materials suppliers and recycling specialists to recycle and, wherever possible, reuse arisings from its sites.
Architectural hardware is now removed and processed by ironmongery supplier Franchi for reuse. Carpet and carpet tiles are similarly sent for recycling or reuse to specialist firms Material Index and Envirocycle.
General Demolition is also talking to Kingspan about salvaging raised access flooring tiles for reuse, says Stainton.
But carefully deconstructing a building and sorting the various materials that come out of a demolition site is a painstaking and labour-intensive process.
鈥淭raditionally, a demolition contractor would want to get rid of all arisings as cheaply as possible 鈥� and, ideally, get paid for it,鈥� says Stainton. Scrap metal is a relatively easy win. But just as you don鈥檛 get paid to recycle your bottles, building glass is not traditionally a source of revenue for the demolition industry.
Now, though, Saint-Gobain pays its partners to recover glass for recycling 鈥� though George Stainton says the operation is essentially cost-neutral and General Demolition isn鈥檛 doing it for the money. His priority is sustainability.
Accurate sorting and segregation is essential when recycling glass says Stainton. 鈥淚t鈥檚 the biggest challenge. The material has to be clean and free of contaminants. And it鈥檚 not just a case of separating the glass from other materials but also segregating the different glass streams,鈥� he adds.
This is one of the reasons why recycling glass from demolition sites has only recently become viable, explains Calcutt: 鈥淐ontaminants are a serious issue and it鈥檚 absolutely critical to control it.鈥�
Saint-Gobain has therefore invested heavily in specialist equipment to analyse and screen out any contaminants in cullet arriving back at its Eggborough factory. But equally important is that its partners on site, like General Demolition, establish rigorous internal procedures and quality controls into their deconstruction processes.
General Demolition鈥檚 first collaboration with Saint-Gobain was on the 2021 refurbishment of the Grade II-listed 鈥� and appropriately named 鈥� 21 Glasshouse Street in London鈥檚 West End for the Crown Estate.
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Here, General Demolition recovered 36 tonnes of toughened, laminated and secondary glass for recycling at the Eggborough plant. To ensure the correct procedure, Calcutt attended the site and carried out a thorough inspection, resulting in a detailed report identifying the types of glass present and, crucially, identifying which could be recycled and which couldn鈥檛.
Plate, toughened and laminated glass can all be recycled, but fire-rated borosilicate glass has very different properties and is not suitable. 鈥淚f even a small amount of the wrong glass gets mixed with the cullet it can cost millions in terms of lost float-glass,鈥� he says.
A particularly troublesome contaminant is nickel. Tiny inclusions of nickel sulphide can expand, causing catastrophic failure of the glass 鈥� a problem that plagued several buildings in the City of London during the early 2000s building boom.
Hence, Saint-Gobain is careful to provide guidance to its partners on site and help them establish the correct procedures, including using nickel-free grinding discs.
鈥淲e put the effort in early to educate our post-consumer partners and it has been worthwhile,鈥� says Calcutt. 鈥淰ery little has been rejected so far.鈥�
Calcutt also works with contractors like General Demolition to find the most efficient way to collect and transport the recovered glass back to the Eggborough factory.
Transport is critical, explains Calcutt. Glass is heavy and transporting it can be expensive, so Saint-Gobain has enlisted the help of local hauliers who can carry back-loads of glass to Eggborough rather than run an empty wagon. Calcutt has even used barges to carry the material and keep transport costs low.
Most of the recovered glass is broken down on-site and tipped into special one-tonne bags supplied by Saint-Gobain, but where that is not suitable (for example with large-format cladding panels) the material can be collected in roll-on, roll-off skips, says Calcutt.
Although the Glass Forever initiative is still relatively new, Calcutt says Saint-Gobain has already enlisted more than 100 partners like General Demolition.
And while less than 1% of all post-consumer glass in Europe is currently recycled, Saint-Gobain aims to be recycling 40% by 2030. The Eggborough plant is at the forefront of glass recycling, says Calcutt.
鈥淪aint-Gobain is global, but the UK innovation is already being shared across Europe and beyond. The UK is definitely leading from the Saint-Gobain point of view.鈥�
Council pioneers closed-loop recycling retrofit
Saint-Gobain was one of a number of materials suppliers that came together last year to create a closed-loop recycling supply chain for Cambridge City Council.
Along with window manufacturers Eurocell and Asset Fineline and insulation firm Aran Insulation, Saint-Gobain helped retrofit 46 council houses to meet 鈥榥ear-Enerphit鈥� standards.
Enerphit is the Passivhaus standard for retrofits that achieve thermal insulation similar to Passivhaus new-build levels.
The project involved fitting Eurocell鈥檚 Modus 75mm profile windows to the houses. These triple-glazed windows achieve a U-value of 0.8W/m虏K and significantly reduce heat loss, helping the homes meet strict energy efficiency targets.
The closed-loop recycling process meant the old PVC-u windows, once removed, were collected, recycled and manufactured into new frames.
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聽Saint-Gobain supported the project through its Glass Forever programme, recycling end-of-life glass and producing high-performance glazing to complement the Modus window system.
This initiative supports the council鈥檚 goal of achieving net zero operational energy, where energy consumption equals renewable energy produced on-site, as part of the government鈥檚 拢3.8bn Warm Homes: Social Housing fund.
Aran was the council鈥檚 principal contractor for the project and appointed Asset Fineline to cover all the window and door requirements.
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