Hot rock

Heavy industry with a positive environmental impact? Impossible, Peter McCrum thought, before he spoke to insulation manufacturer Rockwool

Rockwool stone wool insulation is, at first glance, an unremarkable product. It’s just the lagging that lines our lofts and fills our cavity walls, right? Well, yes. But there is more to it than meets the eye. It has the unusual quality of having both a positive impact on the environment through its production process, and as a finished product. Actually making the stuff helps the environment, using it does too – in fact, using it saves 100 times the amount of energy it takes to produce.

Recognised throughout the world and with an annual turnover of over £700m/year, Rockwool stands out as a highly successful environmentally sound construction product. And it saves lives.

Energy conservation

“As an insulator it conserves energy resources and reduces air pollution and CO2 emissions by minimising the combustion of fuel. This has incalculable environmental and economic benefits worldwide. As a fire retardant it has the ability to withstand heat of up to 1000°C, providing vital time and protection for those caught in fires,” says Janet Boast, environmental assurance manager. “But what really distinguishes this product and sets it apart in environmental terms is its production process.”

Stone wool is made from basalt volcanic rock, which, when heated at high temperature of over 1500°c with a flux or catalyst, can be spun into ‘wool’. Ordinarily, limestone is used as the flux, but Rockwool now uses slag – a waste product from the manufacture of steel. The advantage of this from a technical perspective is that the process is more efficient – the basalt is converted at a higher rate into wool and at lower temperatures. The environmental benefits of this are obvious: less energy is consumed, more stone wool is produced and waste material, the slag, is recycled. The environmental knock-on effects are also significant; less waste going to landfill, and fewer natural resources, in this case rock and coal, are exploited.

But the benefits don’t end there. The process creates large volumes of waste. Rockwool collects the residue from the spinning chamber – fly ash from the combustion process is filtered from the cupola furnaces, dust is extracted from production saws and offcuts from product sold to customers can be returned and broken down. This is all combined into briquettes with an organic starch, another waste product collected from the food and drink industry. The briquettes make up what is known as a ‘formstone” which is then used as a fuel in the furnaces. The production process can begin again, largely fuelled by its own waste.

Resource efficiency

This still does not tell the whole story. Because the furnaces are able to operate more efficiently, less CO2 is emitted. And more efficient furnaces require less maintenance. This requires less downtime and again helps to save energy. Rockwool have also installed the latest gas abatement technology to their furnaces and, needless to say, its plant in Wales conforms to the requirements of ISO 14001.
Residents nearby now have to endure less vehicle movements because of the more streamlined production process and the minimisation of waste and raw materials used. “Since 1995 we have been able to reduce the number of lorry movements by 9000,” says Boast with evident satisfaction. “I think local residents would acknowledge this.”

Inventive thinking

Rockwool relies on fortunate chemistry and the inventive thinking that has allowed it to create an almost closed production loop. Not only is the company caring for the environment, we can thank it for well-insulated homes and offices which use less resources to heat and – in turn – lessens our own impact.

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