Raw material resources The UK brick industry manufactures in the region of 2.7 billion bricks per annum (2003 figures), consuming approximately 8 million tonnes of raw materials, primarily clays, marls, silt- and mud-stones from across the UK. The raw materials are highly variable in their characteristics and give rise to bricks and pavers of wide ranging technical performance. Planning constraints for new quarries and stricter environmental impact conditions of the working of clay pits and quarries means that the value of the workable reserves in the ground are as high as ever. Raw materials are the ‘life blood’ of the brick industry, and the deposits are a major financial and strategic factor in the operation of the brick manufacturing industry. An alternative to using virgin raw material, even at a level of 5%, potentially reduces the year on year consumption of the clays by 350k-400k tonnes. Financial penalties Currently two major issues in the UK brick industry that have the potential of imposing severe financial penalties are those of energy consumption and hydrogen fluoride emissions. High energy consumption As a very significant energy user, the UK brick industry has a yearly consumption of approximately 4.06 billion kWh equivalents of natural gas, (= c. 138.7 million therms, = c. £ 37.5 million) based on 2003 energy data collected by CERAM. Any potential savings on the volume of the energy used to manufacture the bricks would therefore offer significant financial savings. Current UK environmental legislation and proposed UK and European controls and upper limits on ‘greenhouse gas emissions’ have given rise to new and challenging business drivers for the industry, such as the current Climate Change Levy (CCL) agreements, and the forthcoming European Union Emissions Trading Scheme (EU ETS). The adoption, in the UK, of the EU ETS in 2007 will, under current plans, impose an upper limit on a manufacturer’s generation of ‘process CO2’ meaning that once reached, the only option will be to buy CO2 credits at the prevailing market price, or cease production. It is envisaged that the cost of CO2 could be as high as £7 - £10 per tonne, some 5-8 times higher than at the present, a potentially expensive on-cost as a direct result of energy usage. High levels of pollution In addition to the energy related emissions there are also ‘pollution’ emissions that the brick industry has for some years been required to minimise, namely those of hydrogen fluoride (HF). HF is naturally occurring in the clay minerals used to manufacture the bricks. When heated to above 800°C the breakdown of the clay minerals releases the HF into the kiln atmosphere where it can either react with other minerals found in the bricks, such as lime, or is emitted along with the other combustion exhaust gases via the stack, and then to air. Brickworks that currently have high HF levels in the clay, are required to ‘scrub’ the exhaust gases prior to being discharged to the air. The current permitted emission limit is 10mg/m3. The majority of manufacturers are required to use methods such as ‘end of pipe’ solutions, typically limestone scrubbers, to comply with this level of emission. What is being done about it? It is in consideration of these financial and operational constraints that the government’s Waste and Resources Action Programme (WRAP) has been funding investigation into alternative ways of brick manufacture. Two years of research are now beginning to produce results such as in the recently published project report by CERAM Building Technologies. This report shows that there is indeed a good prospect for incorporating material such as powdered glass into the manufacture to reduce costs and emissions while retaining an equivalent quality of brick. Hope in Glass The project undertaken by CERAM carried out small scale trials on bricks made from 3 different clay types and with different properties. A large scale trial was then carried out on bricks made from Etruria Marl. The results showed significant improvement both in energy consumption and in HF emissions. The addition of powdered glass, of particle size 80% below 80 micron, at 5% and 10% levels in bricks was seen to have significant effects on the vitrification of the bricks during the normal works firing schedule. The result of this was an increase in compressive strength, and a reduction in water absorption. In addition to the glass particle size, clay type appeared to have a very significant effect on the degree of improvement observed, and therefore the level of benefit is very much dependent on the primary raw material type. It was possible to replicate the physical properties of clay only bricks fired to the normal works firing schedule, whilst reducing the firing temperature and the firing time, the ultimate result of which is the reduction of energy used. The full scale works trial undertaken on the extruded, solid, Etruria Marl pavers showed a potential energy saving of up to 20%, along with an increase in throughput of 7.7% by the addition of 5% recycled powdered glass. In addition to the energy savings, a reduction of 33% of the level of HF emission was achieved. It is thought that the generation of the glass melt at lower temperatures than normal, resulted in the capture of the HF in the glassy ceramic matrix. Additional benefits observed and measured during the project include a 10% reduction in electrical energy required during extrusion; enhanced quality, especially for freeze-thaw durability and water absorption values for Class B Engineering bricks. Reduction in used energy (Natural Gas) also reduces the levels of ‘process CO2’ emitted which assists the manufacturer in achieving the energy (CCL) and emission (EU ETS) related environmental legislative taxation targets. Conclusion Although the UK brick industry is facing challenges and difficulties, research such as CERAM’s shows some prospect of light at the end of the tunnel. Continued research and an innovative approach should provide hope that the industry can meet the challenges of increased energy and pollution controls against a background of strategic use of raw material.
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