Sustainability of Aluminium
September 2017

Sustainability is still very much a buzz word for not just architects but the whole aluminium in building supply chain. Here we answer some of the many FAQ’s that receives on the subject.

1 What are the key environmental credentials of aluminium that architects should be aware of?
The key environmental credentials of aluminium that architects should be aware of include its exceptional:

• durability
• recyclability
• flexibility
• strength to weight ratio.

Aluminium is the third most abundant element in the Earth’s crust and the most abundant metal. It makes up about 8% of the Earth’s crust by mass, in the form of various oxides and silicates, and almost all metallic aluminium is produced from the ore bauxite, which is first converted to aluminium oxide (alumina) and then to aluminium. Although aluminium was discovered in 1808 by Sir Humphry Davy as a constituent of alum, a complex salt, it was almost 80 years later that the Hall-Héroult process was invented, allowing the affordable volume production of aluminium for the first time. The strong chemical bond between aluminium and oxygen in alumina means that production of virgin aluminium metal is energy-intensive, but this affinity for oxygen is also behind the inherent durability of the metal, as a thin surface layer of aluminium oxide forms when the metal is exposed to air, effectively protecting the metal from corrosion. Surface treatment by anodising or powder coating can further enhance this durability, as well as provide an enormous colour palette for architects to work from, particularly relevant for the facade.

Although commercial production of aluminium started some 130 years ago, the fact that about half of the 1.2 billion tonnes of aluminium ever produced is still in its “first use” is testament to its durability. Indeed, including recycled material, some 900 million tonnes of aluminium is still in productive use, a resource available to many sectors and an energy bank for future generations. Aluminium is almost infinitely recyclable with no loss of material qualities. Recycling of aluminium requires up to 95% less energy than producing the same amount of virgin aluminium from bauxite. While consideration of recycled content might encourage more recycling for some materials, recycling rates are already very high for aluminium in the built environment, with widespread recognition that aluminium is a valuable resource. Studies have shown that more than 95% of the aluminium content is collected from demolished buildings in Western Europe. This is one reason why it is better to think about the end-of-life recycling rate, as it promotes the production and preservation of recyclable materials. Rather than encourage designers to focus on their material source, the end-of-life recycling rate approach encourages circular economy thinking.

2 What initiatives are being undertaken to improve aluminium's environmental performance at the moment and in the near future.

Increased environmental awareness in recent years, driven by regulatory and market demands for improved environmental performance, has given rise to the importance of life cycle assessment (LCA) as a decision-making tool. The collection of global aluminium industry data for use in LCAs has been undertaken for many years by the International Aluminium Institute, which has recently published the 2015 dataset for the primary aluminium industry, demonstrating the global aluminium industry’s commitment to reporting its environmental impacts. This allows production facilities to benchmark their environmental performance and drives improvement. The latest data show that new, high efficiency plant and the adoption of the best available technology is reducing the environmental impact of aluminium production against a range of metrics.

In 2009, a global group of stakeholders from the aluminium industry, civil society, research and policy organisations, and industrial users of aluminium products joined forces to assess environmental challenges, opportunities and needs. This assessment resulted in a report by Track Record: Responsible Aluminium Scoping Phase Main Report. The report underscored the need for an international multi-stakeholder approach that could complement existing sustainability programmes throughout the aluminium industry. This finding ultimately led to the establishment of the Aluminium Stewardship Initiative (ASI). There are now over 50 members of ASI, including CAB, working towards a responsible aluminium value chain. Two standards form the core of the ASI Certification programme: Performance Standard and Chain of Custody Standard. ASI is on track to launching the Performance and Chain of Custody Standards, supporting and normative documents, and assurance platform by end 2017/beginning 2018.

3 Do current environmental rating systems adequately and fairly reflect aluminium's position alongside other related materials?

Based on a detailed analysis of twelve case studies, the Towards Sustainable Cities Programme has argued that the service life of aluminium windows should be revised upwards from 40 years to at least 80 years. The oldest extant aluminium components of architecture in this study are now 120 years old.

As the building and construction industry increases its use of LCA and Environmental Product Declarations (EPD), there is a need to deepen the understanding of these tools. A whole life approach and assessment of the full life cycle of the building should not only consider the operational and embodied emissions, but also the end of life stage and the associated additional aspects and benefits resulting from end of life management (e.g. recycling).

There is a need to ensure the consistent application of the whole life assessment methodology and, referring to the modular approach in EN 15804, to systematically address both Module C (end of life) and Module D in the life cycle assessment. This is particularly important for metals which are highly recyclable and able to contribute effectively to the circular economy.

Acknowledgment: Towards Sustainable Cities Research Programme, funded by International Aluminium Institute, Programme Director: Michael Stacey of Michael Stacey Architects. To download the Towards Sustainable Cities (2016) reports, go to: World Aluminium Publications.