There is currently no legislation in place in the UK that requires the aluminium content of construction products to have in place a chain of custody to demonstrate responsible sourcing. Responsible sourcing criteria do feature in sustainable building assessment schemes such as BREEAM and LEED and they may feature as part of the product data requested for Building Information Modelling.
Aluminium Stewardship Initiative
There are a number of sector-specific schemes in place (e.g. FSC for timber) and voluntary standards (e.g. BES 6001). For materials traded via commodity exchanges such as aluminium, that may be physically and virtually bought and sold many times before they are incorporated into a building product, there are special demands on responsible sourcing schemes for such materials. The Aluminium Stewardship Initiative (ASI) was formed in 2009 and has published a Performance Standard specific to the aluminium value chain. This standard addresses material stewardship through Life Cycle Assessment (LCA) considerations. ASI has also published a Chain of Custody (CoC) Standard for our industry. These two standards, supporting and normative documents, and an assurance platform, were launched by ASI in December 2017 and they are applicable to all stages of aluminium production and transformation, specifically: bauxite mining, alumina refining, primary aluminium production, semi-fabrication (rolling, extrusion, forging and casting), material conversion, and refining and re-melting of recycled scrap, as well as material stewardship criteria relevant to downstream users of aluminium. CAB is a member of ASI and is currently a member of the ASI Standards Committee in control of these standards.
Chain of Custody
The ASI CoC Standard defines requirements for Entities and Facilities implementing chain of custody management systems, including systems for sourcing, accounting and transfer of CoC Material and Eligible Scrap. CoC Material is a collective term for ASI Bauxite, ASI Alumina, ASI Liquid Metal, ASI Cold Metal and ASI Aluminium produced by, and shipped/transferred to, ASI Certified Entities in accordance with the CoC Standard.
Not all voluntary standards for responsible sourcing demand a chain of custody that traces materials back to their raw or mined state in this way.
End-of-life recycling rate
For some materials (for example, where greater recycling at end-of-life needs to be encouraged) it may be appropriate to measure their recycled content to assess how responsibly they have been sourced. In our view, a better measure of the sustainability credentials of aluminium is the rate of recycling at the end-of-life. As 75% of the aluminium ever produced is still in use, it is easy to see that there is simply not enough recycled content available to meet possible demand. Aluminium building products are collected and recycled at end-of-life very efficiently, and the end-of-life recycling rate for aluminium (>90%) reflects the specific recycling performance of a metallic product such as aluminium independently from market growth or its service life. Hence end-of-life recycling rate is a better way to determine this aspect of the sustainability of aluminium building products.
Aluminium components are often used as important elements in a complex assembly such as a window or curtain walling. We wish to highlight the essential contribution of aluminium to the sustainability of the complete building, often as a critical part of an assembly of materials that form a construction product, and particularly when incorporated in the facade, where it has a positive impact on a wide range of sustainability-related criteria for the building, including:
- visual comfort
- indoor air quality
- energy balance and thermal comfort
- acoustic performance
- safety and security
- life cycle impacts
- durability and resilience
Hence sustainable design decisions for facades should be based on:
- an environmental balance based on the environmental impact of the whole facade and not LCA data alone
- data about the holistic performance related to the building, when using rating systems such as BREEAM and LEED.