By Phil Slinger – CAB CEO
Aluminium has always been valued for its lightness, strength and resistance to corrosion. The ease at which it can be infinitely recycled and it is widely used in construction, transport and packaging which means it also carries a premium scrap value. As an engineering material, aluminium can be extruded, cast and rolled to form material ready for a wide range of design applications. Easy to construct and install in buildings, its removal at the end of its life has always been done since scrap aluminium has always carried a cash value.
So what is the difference between ‘deconstruction’ and ‘demolition’? It comes down to how an existing buildings materials are regarded. Demolition regards all material in the building as waste. Deconstruction, on the other hand, recognises the inherent value in all the materials used in the building construction. The principles of deconstruction recognises the costs required to source new raw materials and its transport and manufacture. In short, all materials from a deconstructed building are valuable, a simple example is to ‘downcycle’ (producing a lower value product than the original) waste building concrete as new hardcore, with deconstructed building material never leaving site.
All buildings today should be ‘Designed for Deconstruction’ (DfD). The BRE have developed an outline methodology to assess building designs so that they can be reviewed to show their carbon impact on the environment by achieving higher levels of resource efficiency and, at the same time, embedding circular economy thinking. Key here is the choice of material as some materials are composites that could be difficult to separate on deconstruction.
Obviously, any demolition or deconstruction creates vast amounts of carbon, the latter less so, which is unnecessary if the existing building can be ‘repurposed’. With today’s technology we can repurpose some, if not all buildings, possibly several times. A good example of this is the Roundhouse in London, built originally as an engine shed in 1847, then converted to a warehouse in 1871. After falling into disuse, it was refurbished and opened in 1964 as a concert venue, it then fell into disuse again and was sympathetically restored, opening again in 2006 as one of London finest small-to-medium sized venues. Today we see existing buildings having their external skins replaced, often with aluminium facades, with these buildings taking on a dramatic change in use with reduced carbon emissions.
The majority of aluminium used in construction is either in extrusion form, sheet form or cast, making it relatively easy to remove and recycle if the products have reached the end of their useful life. Some composite materials, including aluminium, may not be recyclable, so the choice of these materials should be carefully considered. Back in 2003 when the old Wembley Stadium was being ‘demolished’, 96% of all the aluminium used in the building, some 200 tonnes, was removed and recycled. This data was confirmed at the time by ‘TU Delft’, a University in the Netherlands, that remains at the forefront of research into the circular economy.
We can apply the principles of deconstruction to any building, maximising its material value whilst reducing its carbon impact. Aluminium can be deconstructed and reused in several ways.
In its simplest form, physically removing the various aluminium items from a building and sending the aluminium for recycling. The ‘cleaner’ the scrap the more valuable it is as scrap. The weight of gaskets, hardware and thermal breaks in the profiles reduces the aluminium content on weighing and has an impact on recycling as further deconstruction may be necessary prior to recycling.
CAB’s own closed loop recycling scheme goes further by recycling the scrap within recognised aluminium grades. By using an XRF analyser (X-ray fluorescence) which is a powerful, nondestructive technique for measuring elemental composition from magnesium (Mg) to uranium (U), these handheld XRF analyzers are portable devices that offer immediate composition of an alloy revealing its grade. Incorporating modern techniques that remove unwanted items such as screws and thermal breaks, the resultant, chipped aluminium is ready to be remelted for new product whilst maintaining its original grade.
Today we are beginning to ‘Designed for Deconstruction’ (DfD) which can enable constructed items to be reused in new buildings, this is where aluminium engineering excels and there are already some very good examples of this form of construction which we hope to discuss in the future.
