China clay, or kaolin, is synonymous with Cornwall and south-west Devon, and has been a major industrial output of the region since its discovery there in 1746. China clay has many uses in paper, ceramics and specialities including paints, rubber, plastics and pharmaceuticals.
China clay mining leaves behind quarries and spoil material. Imerys, a china clay producer with extensive operations in south-west England, takes its responsibility to restore its sites seriously. The company is always looking at innovative ways to enhance its restoration activities, and one area relating to soil creation has sparked an entire industry in researching, manufacturing and installing soils - and provided focus on the development of a zero-waste economy.
Imerys has teamed up with problem-solver and organics recycling specialist 4R Recycling, part of 4R Group, to manufacture high-quality soil materials from waste products from a variety of activities. In what is thought to be an industry first, 4R has worked closely with the Environment Agency and other partners to take dredged material from Falmouth harbour and make high-quality soils from it.
Disposing of the dredged material to landfill, which is the traditional route, was going to be prohibitively expensive and stood in the way of a proposed £1.5m marina redevelopment by Premier Marinas. 4R’s solution ensured that the cost of processing the material was affordable and the marina development went ahead. And a need for additional soils was solved as a result.
Imerys incorporates a mixture of organic materials, supplied by 4R from regional producers, into restored areas and uses them to create soils. Materials as diverse as woodchip, biosolids, plasterboard gypsum, compost and marine dredgings have all been used. There have even been trials using wool-rich carpet as mulch-mats, with fantastic results.
The outcome for the natural environment through the use of manufactured soils to restore china clay spoil tips - such as the Dubbers tip, near Nanpean in Cornwall - is significant too. Restoring and planting slopes dramatically reduces erosion and run-off, and plant growth on restored sites absorbs five or six tonnes of carbon dioxide from the atmosphere per hectare per year.
Chris Varcoe, mineral services manager of Imerys Minerals, says: “We are committed to restoring our china clay sites in a sustainable manner. Using organic waste in this way enables us to enhance our restoration activities significantly. We also provide councils and businesses in the region with local, long-term recycling outlets for their organic by-products.”
It is difficult to comprehend the scale of these projects. At Lee Moor, near Plymouth, Imerys and 4R have worked together to restore more than 20 hectares to a mixture of grassland and woodland. And it is this scale that has the potential to become a major driver for the zero-waste economy. And across the country, there are thousands of hectares of land that require restoration, but a severe lack of soil to do so.
The before and after pictures here demonstrate the visible benefits of restoration, a requirement of almost all former mineral planning permissions. Some of these sites have been operational for decades, but many are now being returned to a combination of heathland, grassland, woodland, agricultural use, nature conservation and public open space.
Colin Rudd, 4R Group’s technical director, continues: “This area of regulation is very complex, and our approach is to demonstrate beyond doubt that the products we manufacture are safe and help to enhance the environment by solving problems and avoiding the use of virgin products. That is why we have invested heavily in growing trials in our glasshouses, as well as in-situ test plots to demonstrate the benefits and fitness-for-purpose of the products we manufacture.”
The research is not limited to soils and growing media. 4R’s extensive knowledge and team of soil scientists have developed a range of products, including fertiliser replacement products such as the award-winning Potassic Lime, 2011’s Recycled Product of the Year. The company is also responsible for solving the problem of managing cement industry by-products that are rich in potash but increasingly expensive to landfill, indirectly inflating the cost of construction.
Of course, nothing is easy. Some organic materials present difficulties, such as odour, or there will be a need to carefully stabilise or blend different products to ensure they provide just the right mix of nutrients. In the case of the dredgings, the material was moved in 4R’s fleet of lorries, retained and sampled on-site to demonstrate that the chemical parameters rendered it safe for use.
Once in place, the material was cultivated and seeded, with trials having already demonstrated that a recreated acid grassland would normally be established within 12 months of the beginning of the project, subject to weather and seasonal factors. Root growth and ground coverage result in a stable, sustainable and restored landscape.
With perhaps a million tonnes of digestate from anaerobic digestion schemes being produced every year by 2020, the development of sustainable, affordable markets for organic materials and mature, co-operative regulation of a responsible industry could lead to a huge boost to local economies, and the protection and creation of jobs, from plant operatives to soil scientists to landscape architects.
The challenge is for regulation to keep up with industry, rather than putting the brakes on innovation and green growth. But 4R’s experience with Falmouth’s dredgings, Imerys’ need for soil and the cost-effective solution demonstrates what can happen: when there’s a will, there’s a way.
Mike Holt, Managing Director of 4R Group
4R Group Ltd
4R Group specialises in a range of environmental, waste recycling and consultancy services. 4R also develops and manufactures fertiliser replacement and animal bedding products for the agricultural, industrial and commercial sectors. For more information: www.4r-group.co.uk
Imerys Minerals Ltd
Imerys mines natural resources and converts them into value added products for its customers. With 245 industrial facilities in 47 countries, the company has more than 15,000 employees and mines 29 minerals. In the UK Imerys Minerals Ltd manages the extraction, processing and marketing of Kaolins, Ball Clays and Calcium Carbonate. For more information: www.imerys.com