CAB Chief Executive, Justin Ratcliffe looks at issues ranging from low energy recycling to buildings being ‘urban mines’.
When considering a specification, it is essential to consider the responsible sourcing, effectiveness, durability, and the potential recycling of any material. BioRegional in its report on the Bedzed housing development, designed by Bill Dunster Architects, noted that: ‘The embodied energy of a material needs to be considered over the lifespan of the material, for example aluminium is a highly durable material with a long lifespan of (over) 60 years and therefore is an appropriate solution….despite its high embodied energy’.
Well before this others recognised the importance of aluminium in the coming centuries. In 1857 Charles Dickens became very interested in the discovery of a new metal that he believed would have an outstanding future – this was of course aluminium, yet it is only in the last 100 years that it has advanced from being a rarely used material to the second most used metal worldwide.
Aluminium can be indefinitely recycled
Once an aluminium product has reached the end of its useful life it can be infinitely recycled with no loss of quality. Furthermore, the mineral Bauxite from which aluminium is extracted is the third most abundant material in the Earth's crust and is mined virtually at the surface. The areas of mining, being mostly shallow, are easily put back to the original land use often with new benefits to the local community.
Buildings as ‘Urban Mines’
The energy used for primary production is embodied, to a large extent, in the metal and, consequently, in the building too. Today’s buildings and their contents therefore present large ‘urban mines’ of around 400 million tonnes of aluminium metal that can be extracted and recycled by future generations not just once but repeatedly. Aluminium is extensively employed in buildings, but it does not remain permanently in place. In highly-developed countries, aluminium in buildings of all types amounts to between 120 and 200 kg per person. Aluminium recycling therefore not only represents good urban housekeeping, it provides major energy benefits today and tomorrow.
Aluminium For Future Generations
We can see that an aluminium ‘bank’ of material is being formed in the world which is available for future generations to use. It is estimated that 663 million tonnes of aluminium is in use around the globe. To meet our needs for aluminium we currently add about 40 million tonnes of new prime aluminium to the ‘bank’ every year, with a further 40 million tonnes from ‘bank’ recycling.
Being virtually 100% recyclable, aluminium is also not flammable and does not give off toxic fumes when subject to fire. By selecting the right alloy the designer is offered a wide range of properties including high strength – up to 400 Mpa, low density, high thermal conductivity and good forming and jointing characteristics.
Low energy recycling
By using only 5% of the initial energy required to form aluminium, the material can easily be recycled without loss of properties. Nowadays recycling plants collect various grades of aluminium which are used in extrusion, sheet and cast production and recycle these grades separately so that they can be put back to their former use with little or no further refinement and addition of alloys.
One of the most important issues is of that of ‘aging’. As aluminium ‘ages’ it becomes stronger. Part of the process in extrusion is in an accelerated ageing process which consists of heating the profiles at high temperature for a matter of a few hours. Whereas other materials ‘age’ and cannot be recycled with new material, aluminium of any age can be recycled as the ageing process is lost upon remelt of the material.
What of finished profiles, corrosion, thermal breaks, hardware, screws, etc. in the recycling process? As the material reaches melting point, heavier elements sink in the melt and lighter elements such as ash from powder finishes and thermal breaks float to the surface. Any gasses that are produced are recycled and burnt again to ensure no release of toxic gasses to the environment. Many systems today are being designed to be ‘deconstructable’ to allow materials to be separated and recycled.
The Council for Aluminium in Building offers specifiers support in the specification and use of aluminium in the UK’s building industry. Further information is available at www.world-aluminium.org and www.eea.net . CAB is also very active on the European stage ensuring that changing European legislation meets the requirements of the UK market. Your support is needed and for more details on CAB and becoming a member of the trade association contact Julie Harley at the CAB office