A lot has been claimed about the benefits of aluminium by CAB and many other associations, but we should also ask: “Where would we be today without this material?” With a high strength to weight ratio, aluminium is a structural engineering material, without it we would not have the modern airliners of today, or indeed much in the way of space flight. On the ground, more of our vehicles are now being made from aluminium, as less weight means less energy used in propulsion and potentially longer lasting vehicles. In fact, there are so many uses of the material across our modern life, it is difficult to imagine life without it!
So how does all this translate to aluminium products used in construction? The most obvious is in fenestration, windows, doors, curtain wall and atria roofing. But aluminium is also extensively used today in external cladding of buildings including roofing solutions such as standing seam designs. Despite some recent disastrous building fires where aluminium has been used, aluminium remains completely non-flammable.
Why is it specified so widely? Together with its unique engineering characteristics, aluminium can last the lifetime of a building, or more to the point today, last the lifetime of a building envelope as we look to repurpose and re-clad existing building structures. After the aluminium ‘in-use’ phase, it can easily be removed, recycled and replaced. Aluminium also needs no other supporting material to achieve impressive spans and comes in a wide range of alloy types to suit many applications. With the further advancement of architectural aluminium finishes, now in an unlimited range of powder coatings colours in several exposure classes and the incredibly resilient anodising finishes, we now measure the life expectancy of building envelopes using aluminium in decades, not years.
In fact, 75% of all aluminium in use today, since the material was first commercially produced in the 1880’s, is still in use today. The growing demand for the material means that there is not enough scrap available to meet the growing market sectors across construction, transport and packaging. Today we can only meet a third of the demand by recycling and, as a result, the monetary value of scrap aluminium remains high.
So is aluminium 100% recyclable? In practice, yes, and most importantly, many times over with no loss of structural integrity. The thermal breaks, stainless steel screws, gaskets and hardware can now be easily be removed from post consumer scrap in automated processes, leaving the aluminium in chipped form ready to melt back into billet production with no loss of quality. One of the key facts to aluminium recyclability is that it takes just 5% energy to recycle aluminium compared to the energy needed to extract new aluminium from the earths crust.
Following oxygen and silicon, aluminium is the third most abundant element in the Earth’s crust. Often close to the Earth surface in the form of bauxite, from which alumina is extracted, is easy to source in open cast mines which can quickly be re-landscaped often with the fauna which was initially removed. Aluminium production also continues to become more efficient reducing its embodied carbon with prime (newly mined) ’low-carbon’ billet equating to just 4.00 tCO2e (shorthand for carbon dioxide equivalents). In comparison, the average production of one ton of aluminium primary aluminium has an emission of 16.7 tCO2e. When added with 75% post consumer scrap, as a typical example, the carbon dioxide equivalent is lowered still further to just 2.3 tCO2e. With continuing steps being made in the use of more renewable energy sources to produce aluminium such as hydro electricity and now with the promise of the use of hydrogen in the future, the embodiment of carbon in prime aluminium will continue to fall.
Today, the challenge in recycling aluminium is to keep the post consumer scrap separated into alloy grades, fortunately there are only a few grades used in construction and with the help of a spectrometer these can easily be identified prior to the disassembly of post consumer products. With these recycled material grades, virtually 100% recycling is achievable with no prime aluminium needed to produce new billet.
So should we specify recycled aluminium only? Well no, as there is not enough to go around! A project containing 100% recycled aluminium will only mean more prime aluminium being used in another. As aluminium has a high scrap value, the majority re-enters the supply chain in this ‘closed loop’ scenario.
The Council for Aluminium in building has pioneered its own ‘Closed Loop Recycling’ scheme in the UK dedicated to the aluminium construction market. The scheme expects its members collect and recycle pre-consumer and post consumer scrap in the UK through the scheme members creating a ‘closed loop’ or a ‘cradle to cradle’ cycle which continues to reduce carbon embodiment keeping the material ‘in-use’ in the UK rather than losing this overseas.
The aim of the initiative is to encourage the recycling of aluminium alloys within the same alloy grades. For the CAB scheme we require that extrusion grades of aluminium, namely 6000 series alloys for the architectural aluminium market, are recycled back into the same 6000 series alloys. The same can be said for sheet aluminium recycling, namely with 1000 series alloys. It is important to reiterate that in a ‘closed loop’, an aluminium alloy can be recycled infinitely without loss of its specific characteristics.
Pre-consumer scrap can easily be recycled before it leaves the factory as it is often ‘clean’ and of a known alloy, post-consumer scrap on the other hand, is where the challenge lies. With the many thousands of tonnes of alloy extrusion and sheet used in our buildings across the UK, we now look towards the advantages of deconstruction, separation and recycling, and the ability to see view our built landscape as an ‘urban mine’ for future raw materials. As already stated, we have recycled aluminium over many decades, primarily as it has a high recycle value, but without a ‘closed loop’ we can ‘lose’ the specific grades we require to recycle the aluminium back into the same product type. If we can constrain recycling to specific alloy grades, we can recycle extrusions back into new extrusions and offer a true circular economy for our aluminium products in the UK construction industry.
Key to this capability is the advent of the handheld spectrometer for identifying the content of an aluminium alloy. Easily portable and very quick to use, grades can easily be checked prior to recycling. This means that the aluminium grades could easily be checked and identified on a building site prior to deconstruction. The quantity available on a given site can also be relatively easily calculated before removal, as aluminium extrusions and sheets are usually uniform in shape and easily measured. Skips for the scrap, clearly labelled for the identified grades being removed, can be obtained from recyclers to be placed on site for collection of this valuable post-consumer scrap.
The second challenge is to remove non-aluminium components from the aluminium frames of windows and curtain walling, such as hinges, handles, gaskets, screws and weather seals. Done manually, this could take some time, and we must also consider the removal of thermal breaks made of materials such as polyamide and polyurethane. Fortunately, the technology has advanced considerably, and this process is completely automated. What is supplied back to the smelter is ‘chipped’ aluminium, with minimal contaminants such as paint and thermal breaks which are mostly removed in the process.
CAB’s Closed Loop Recycling Scheme is open to members as part of their membership package. While such closed loop recycling of construction materials is currently voluntary, government legislation could be introduced on ‘embodied carbon’ content in the future and main contractors are increasingly seeking evidence to demonstrate the sustainability credentials of their supply chain. Aluminium scrap is an important resource and we should maximise the quantity and quality of recovered aluminium scrap in the UK to build the circular economy of the future.
CAB encourages anyone working and supplying products within the construction aluminium supply chain to join CAB and ‘join the discussion’. Together we can shape the industry and portray the facts of this amazing material!
CAB and staff are on hand at the offices to answer any aluminium fenestration related questions. Information is regularly updated on the CAB website at www.c-a-b.org.uk. For association membership enquires please contact Jessica Dean at the CAB offices by email jessica.dean@c-a-b.org.uk or by phoning on 01453 828851.
