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Fri May 20 2022

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A solution to asbestos waste?

28 Jan A pioneering research project is developing a commercial-scale method of diverting asbestos-containing waste from landfill and transforming it into a harmless – and useful – building product. David Taylor reports

One of the biggest health & safety headaches for the construction industry is the ever-present risk of asbestos turning up, whether in a building under refurbishment or simply buried in a brownfield site.

Tonnes of the stuff – most of it in the form of asbestos-cement roofing or cladding sheets – still exist in buildings, just waiting to become somebody’s problem. And a problem it certainly is, with the cost of disposal, not to mention the disruption caused by its discovery, potentially impacting a construction project.

This article was first published in the January 2022 issue of The Construction Index Magazine. Please sign up online 

Wouldn’t it be great if, instead of being a troublesome (and potentially deadly) waste material, old asbestos-cement were a recyclable raw material for new products?

Well, now it is – at least in theory. Earlier this year, a new company called Thermal Recycling completed a demonstration project that successfully recycled asbestos-containing products into a safe material that can be used as a cement substitute.

Called Calmag, the recycled product is made from cement roof sheets containing chrysotile asbestos. Thermal treatment changes the chemical and physical composition of the asbestos, producing an asbestos-free material that is then crushed. The end product can be used as a sustainable aggregate and added to concrete mixes.

Supported by a government grant, Thermal Recycling opened its demonstration plant in Wolverhampton in September 2020. The aim was to prove that its technology could convert asbestos roofing on an industrial scale and in a commercially viable and environmentally safe way.

The project involved making prototype construction products from Calmag – named because it comprises calcium, aluminium and magnesium as silicates, carbonates, sulphates and oxides.

Independent laboratories then conducted extensive technical assessments of the product’s characteristics, including compression strength, load-bearing capability and water permeability. The research showed that Calmag is effective as a cement substitute.

Market research was also conducted in different sectors to identify potential users of the product.

The original idea for what became Calmag came from Steve Beaumont, a director of Therser Services, a manufacturer of industrial furnaces and kilns. “He is an expert in thermal techniques,” says Thermal Recycling chairman Graham Gould, “and he knew that asbestos could be safely recycled.”

Together with his business partner, property developer Liam Wordley, Beaumont set about finding somewhere they could set up a trial production facility and, crucially, drum up some financial support from potential investors.

This is where Gould came in. “Steve and Liam went to see a private equity business in London and although it wasn’t the sort of project they would invest in, one of the partners thought it was something that would interest me and he got in touch.”

The partner was right: Gould, who has a background in project development and business strategy, came on board to draw up a business plan and find other investors.

Realising that the project needed sound scientific back-up, Gould also secured the involvement of the University of Wolverhampton to monitor and analyse the process and its product. Under the auspices of the university’s Brownfield Research and Innovation Centre (BRIC) a research programme was drawn up to further develop the understanding of the asbestos conversion, or ‘denaturing’, process developed by Thermal Recycling.

Before any of this, however, Thermal Recycling had to build a test kiln to prove that asbestos-cement could indeed be denatured and recycled. To do this, the company had to design and build a special kiln for that purpose.

Then it had to jump through numerous regulatory hoops to get an Environment Agency permit and secure planning permission for its full-scale demonstration project. This involved carrying out an exhaustive environmental assessment, drawing up a detailed operating procedure and developing the required specialised abatement technology.

These days, anything that entails the handling or processing of asbestos-containing materials is very strictly controlled, and for good reason. Furthermore, because we now know how deadly any exposure to this material can be, persuading any investor or business partner to come on board a pilot project such as Thermal Recycling’s is a long and delicate process.

“Getting all the necessary approvals is a very, very big deal,” says Gould.

Perhaps one of the biggest hurdles the company has had to overcome is to convince others that, by simply applying heat, deadly asbestos fibres can be denatured and transformed into something harmless.

It might seem too good to be true but it’s true nonetheless, says Gould: “Denaturing means changing the fundamental properties of a material. By applying heat you cause physical and chemical reactions to convert the asbestos into something else. It quite simply isn’t asbestos anymore,” he says.

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Gould concedes that other processes have been used in laboratory conditions to denature asbestos. “There are a number of people who claim to have developed processes to denature asbestos or render it harmless,” he says, “but there’s a huge difference between doing something on a small, unregulated, scale and doing it on a full-scale industrial basis.”

He adds: “People have known for many years that asbestos can be denatured, but nobody has ever reached the stage we’re at now.”

Proving that it is possible to transform old asbestos-cement sheets into something relatively inert and harmless is one thing; to prove that there is a market for that material is another.

Thermal Recycling applied for, and was awarded, a Smart grant from Innovate UK (the government’s ‘arm’s-length’ R&D funding agency) to carry out tests and research the potential market for its Calmag product. Testing was done by Lucideon, the independent materials testing and assurance company, at its Stoke-on-Trent facility.

The research concluded that Calmag can be used as a cement substitute, replacing up to 10% of cement in most mixes. This has a clear benefit given current efforts to reduce the climate impact of the cement industry’s enormous carbon footprint.

“This was really important research for Thermal Recycling; identifying a market for Calmag defines us as a circular economy business,” says Gould. “This also reinforces our vision for the company; we can not only divert asbestos away from landfill, but also offer a sustainable product to the construction sector.

“There is a pleasing symmetry to being a business that is involved in removing the problem of asbestos for future generations and being able to use the converted material which contributes to creating a better future for that generation,” adds Gould.

He believes that the market for cement substitutes has never been stronger – and Calmag can exploit that, now that the traditional substitutes are becoming increasingly scarce. Pulverised fuel ash (PFA) and ground granulated blast-furnace slag (GGBS) are derived from coal-fired power generation and steel production respectively – two industries that are fast disappearing from the UK.

“Also, PFA has some technical issues that we don’t have with Calmag,” adds Gould.

At present, the only way of disposing of asbestos is in specially licensed landfill sites. Approximately 60% of asbestos taken to landfill is in the form of the type of roofing sheets that comprise Thermal Recycling’s feedstock. Gould would like to see all of this converted into Calmag.

“Landfill isn’t the answer,” he says. “When you do that you’re not removing it; you’re just moving it,” he adds, and who can argue with that?

This article was first published in the January 2022 issue of The Construction Index Magazine. Please sign up online 

What is chrysotile?

Chrysotile, also known as white asbestos, is the most common type of asbestos, comprising over 90% of all asbestos found in the UK.

It is a naturally-occurring mineral belonging to the amphibole group of asbestos silicates of which there are six types, all forming long fibrous or needle-like crystals.

This characteristic fibrous structure has been exploited by humans for a variety of purposes throughout history; asbestos fibres have even been found in ancient pottery, having been mixed into the clay to strengthen it.

Its resistance to fire is well known and it is also an excellent thermal and electrical insulator. Its fibres are so long, soft and flexible that chrysotile can be woven into a fabric and was widely used to make protective clothing for workers in industries such as steelmaking.

Because the fibres also have good tensile properties, they were often mixed into other materials, such as cement, to improve strength.

All types of asbestos are hazardous to health. Their fibrous crystals each consist of many microscopic ‘fibrils’ that can be released into the atmosphere and inhaled. They are highly carcinogenic and can lead to serious conditions such as mesothelioma, asbestosis and lung cancer.

In the UK, the use of all asbestos materials was banned outright in 1985 and since 2012 owners of non-domestic buildings have had a duty of care to manage asbestos on their premises, having it removed by a licensed contractor if necessary.

This article was first published in the January 2022 issue of The Construction Index Magazine. Please sign up online 

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