Improving and using recycled gypsum – the Knauf commitment
Gypsum, the basic material of plasterboard, is a plentiful and widely available material. It is also eminently recyclable and the plasterboard industry has been at the forefront of a drive to develop a circular economy for construction products.
Knauf, as one of the world’s leading manufacturers of building materials, is well advanced on the journey towards building such a structure for its product manufacture.
In 2010, the Plasterboard Sustainability Action Plan was published, with the plasterboard industry being recognised as a trailblazer in its determination to reduce the impact of plasterboard manufacturing and waste. The process has involved the whole supply chain in developing a way of working that eliminates landfill waste and brings reclaimed, post-consumer gypsum into the manufacturing of new products.
The circular economy concept – in action
As long ago as 2015, Knauf signed an agreement with waste management company Countrystyle to develop a facility both to recycle Knauf’s own production waste and to process post-consumer plasterboard products. By mid-2017, a 5,300m2 facility had been constructed at Countrystyle’s main Ridham Dock site, just a mile down the road from Knauf’s Sittingbourne plant.
Knauf’s agreement with Countrystyle includes the recycling of manufacturing waste – offcuts and plasterboard which hasn’t hit quality control standards. All this waste goes to Countrystyle for re-processing. No manufacturing waste goes to landfill.
Countrystyle, however, is part of a nationwide group of waste management companies who also reclaim and re-process post-consumer plasterboard waste from construction and demolition sites. Knauf uses the gypsum that emerges from the end of this process and, in 2019, the Company took back around 45,000 tonnes of recycled gypsum from Countrystyle for use in its manufacturing.
Matt Wood, Manufacturing Manager at Knauf Sittingbourne, said “Around 10% of the gypsum in our finished board products is from recycled gypsum.
“The environmental benefit in terms of improving the circular economy and reducing haulage miles and emissions are obvious, but there is also a cost benefit to us. Sending our production waste to landfill would incur significant financial cost, as well as environmental costs, so the recycled product is actually cheaper. With better technology we hope to be able to further increase the percentage of recycled gypsum that we use.”
The co-location of Countrystyle and Knauf’s Sittingbourne plant have obvious advantages – not least the minimal transport required for both manufacturing waste and the supply of recycled gypsum. It is a textbook example of how to build a mutually beneficial closed-loop recycling system.
Establishing a nationwide mechanism for collection and recycling of gypsum has required industry-wide co-operation and Knauf is currently chair of the Gypsum Product Development Association (GPDA).
This organisation exists to pioneer new applications for gypsum-based building products and also advises on matters of environmental impact. One aspect of this is to encourage and support a whole supply chain to manage the collection, processing and use of pre- and post-consumer gypsum.
Balancing the benefits
Post-consumer plasterboard is generated as buildings get refurbished or demolished. It is, of course, therefore heavily contaminated with paints, nails, ceramic etc. Processing is a longer and more complicated task than for pre-consumer waste, and the quality of the reclaimed gypsum is different, presenting challenges for the manufacturing of new plasterboard material.
One of these is the fact that that post-consumer recycled gypsum uses more water in the process to manufacture high-quality plasterboard. Recycled gypsum produces a slurry which is more viscous, requiring the addition of more water to bring it to the right consistency for the manufacturing process. The subsequent drying process in the calcination plant is therefore longer and requires more heat.
The net result is a higher use of both water and energy for product manufacturing, which must be balanced against the environmental benefits of using recycled material.
Knauf has kept this delicate balancing act within its own control. It’s been over a decade since the Company installed a new calcination plant and equipment at the Sittingbourne plant, alongside new gypsum milling equipment, making the whole process of calcining gypsum much more energy efficient.
Heat exchanging equipment has been installed at the Immingham plant, saving approximately 10% of energy usage. Excess water content of boards was also reduced by around 12.5%, with proportionate savings in the gas needed to dry it, plus a saving of 100 tonnes of water per day.
Knauf’s Immingham plant does not benefit from the immediate proximity of a reprocessing plant in the same way as Sittingbourne, but a relationship with Roy Hatfields waste management in Rotherham is allowing the plant to develop a similar strategy to that used in Sittingbourne.
In 2019 the Immingham plant used some 27,500 tonnes of recycled gypsum in its manufacturing, a total that is set to rise further over time.
A supply chain for waste
Collecting and processing post-consumer waste has been the major challenge in establishing the virtuous circle of gypsum recycling.
Since 2010 a whole infrastructure has been established to achieve this. Individual companies – such as Countrystyle and Roy Hatfields – supply dedicated skips to building sites to collect plasterboard waste, while brokers such as Reconomy work to connect building contractors with recycling companies.
Green initiatives and technologies are constantly being developed, and Knauf is fully committed to researching and developing new ways to reduce the environmental impact of our business. Increasing the volume of recycled gypsum in our products and in the market as a whole is one part of this process.
