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In the loop: recycling gypsum

5 May 20 Gypsum is one of the most recyclable building materials in existence – but it seems we’ve only just woken up to the fact. David Taylor reports

Crucible Gypsum Recycling
Crucible Gypsum Recycling

As any DIYer who’s taken a few sacks of plasterboard offcuts to the local dump will tell you, it’s not an easy substance to get rid of. It might look inert but in a landfill site, the gypsum from which plasterboard is made reacts with any decaying organic matter to produce hydrogen sulphide, a poisonous and extremely smelly gas.

But why landfill plasterboard in the first place? Unlike other mineral-based building materials like cement and fired clay, gypsum has the huge benefit of being infinitely recyclable: pound it to a dust and mix it with water and it sets hard. Grind it to a powder again and you’re back to square one: just add water. And so on.

The cost of intercepting the waste stream, separating the gypsum from the paper sheathing and processing the raw material to an acceptable quality standard has meant that until relatively recently very little plasterboard has been recycled by manufacturers, whose primary feedstock remains fresh quarried gypsum.

For many years there has also been another source of cheap gypsum available to manufacturers: desulphurised gypsum, or DSG, a by-product of flue gas desulphurisation at coal-fired power stations. In 2014, more than 75% of plasterboard products in the UK were produced using DSG. 

The shift away from coal power in the UK is undoubtedly good for the environment, but the phasing-out of coal-fired power plants means the disappearance of DSG – and this could have a negative impact on construction’s ability to go green if the only alternative is quarried gypsum.   

The recycling and reuse of waste plasterboard was given a boost in 2007 with the so-called Ashdown Agreement, an industry initiative led by the Gypsum Products Development Association that set targets for the diversion of waste gypsum from landfill.

The key targets set out in the Ashdown Agreement were to reduce the amount of plasterboard waste being sent to landfill from UK plasterboard manufacturing operations to zero tonnes/year by 2015 and to increase the recovery and recycling of plasterboard waste, for use in plasterboard manufacture, to 50% of new construction waste arisings by 2015.

The ultimate goal is to reduce the amount of plasterboard waste sent to landfill to zero by 2025.

“Prior to 2008 very little was recycled – probably less than 2%,” says Steve Hemmings, head of environment & sustainability at Etex, the parent company of Siniat, formerly Lafarge Plasterboard.

Siniat was one of a number of manufacturers, recycling firms, demolition contractors and universities involved in Gypsum2Gypsum, a three-year EU-funded research project launched in 2013. This exercise demonstrated that it is feasible in practice to re-incorporate up to 30% of recycled gypsum in plasterboard manufacturing. Two of the five factories that participated in the project achieved  the 30% target.

There is, however, a cost involved, as the project summary explains:

“Potential cost benefits were levelled, mainly due to the requirement of higher amounts of relatively costly additives. From the cost point of view, process modification investments may become more attractive in the near future, depending on raw material prices and national legislations (e.g. gate fee for land-filling). Stronger economic and environmental benefits can arise in the future, when the necessary process modifications will be optimised and the recycled material quality will consistently rely with [sic] the quality specifications set by the [Gypsum2Gypsum] project.”

Achieving that 30% target was “quite a painful experience,” admits Hemmings, but he says that Etex is continuing to invest in its ability to reuse waste gypsum to make new plasterboard products.  Since 2016 the group has trebled the amount of recycled product it uses and now incorporates “significantly more than the industry standard of 8%”.  

Up to now, the Siniat plasterboard factory in Ferrybridge, West Yorkshire, has been the focus of the company’s research into the recycling and reuse of waste gypsum. After an investment of €10m (£8.8m) by the parent company, a new production line designed to optimise the use of recycled gypsum began operating last year.

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In 2017 Etex took over a failed gypsum recycling plant in Worcestershire and set up a new business, Crucible Gypsum Recycling, to optimise the flow of recycled material back into the manufacturing process. 

Construction is not, of course, the only industry to consume gypsum. The mineral has a multitude of industrial uses ranging from cosmetics to agriculture. And while this means that Crucible potentially has a wide customer base, Hemmings says that its output is intended to be entirely dedicated to the production of plasterboard.

“For us waste gypsum is a strategic resource and we’re keen to keep it in the loop. Once it’s gone into agriculture, say, we’ll never get it back again,” he explains.

Furthermore, Siniat is likely to need a reliable and plentiful supply of recycled gypsum, and not just for the Ferrybridge plant. Last November the company announced plans to invest £140m in a new plasterboard factory on a brownfield site at the Royal Portbury Dock in Bristol, not far from its existing Siniat plant.

Construction is scheduled to begin next year and Etex hopes to start producing the full Siniat range in 2022. The existing Bristol and Ferrybridge plants will remain in full production.

Sustainability is a key feature of the new factory, the company says. Besides a rainwater harvesting system and a fleet of electric-only forktrucks, the plant will “have the ability to use industry-leading ratios of recycled gypsum in its manufacturing operations”.

So with the supply of DSG rapidly drying up and the new Etex factory in the offing, it seems that Crucible Gypsum Recycling doesn’t need to worry about finding a customer for its product. 

Etex's Bristol plant
Etex's Bristol plant

How much plasterboard is currently recycled?

WRAP (The Waste & Resource Action Plan) has estimated that 1.3 million tonnes of waste gypsum are produced annually, both from construction projects and the plasterboard manufacturing process. This material can be broadly divided into three categories based on their origin:

  • Production waste (e.g. gypsum boards that do not meet specifications and waste resulting from the manufacturing process). The volume of production waste currently recycled is approximately 5%.
  • Waste arising from construction sites (construction waste). At current market volumes, the amount of gypsum construction waste currently recycled is estimated at around 7%.
  • Demolition waste. This includes both demolition and renovation waste and is the most complex to address because it adheres to other construction materials (such as plaster skim, paint, timber etc). Demolition waste does not depend on market volumes and its recycling is estimated at only around 1%.

Source: Gypsum2Gypsum

This article was first published in the April 2020 issue of The Construction Index Magazine 

UK readers can have their own copy of the magazine, in real paper, posted through their letterbox each month by taking out an annual subscription. Click for details.

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