Recycling materials used to be a common practice in the built environment. Two hundred years ago if you knocked a building down, you just reused as much of the stone, bricks and timber as possible.

Today, in the era of steel, concrete and glass structures, we have got into the bad habit of sending almost everything to landfill (only 6% of construction materials are reused in an industry responsible for 40% of CO2 emissions). 

The principles of the circular economy, the shift from take/make/dispose to design for reuse, have been slow to become the norm in the built environment sector. There are many practical hurdles to overcome, like the need to develop so-called digital ‘materials passports’ that capture and store information on the materials used for future users to work from – perhaps decades into the future. Another brake on progress has been that more and more projects are organised through collaborative BIM models which aren’t currently set up to recognise or work with recycled materials – the effect being that the idea isn’t even entertained. Typically, even developers and constructors with the best of intentions find it hard to overcome the lack of a standardised way of evaluating and incorporating recycled material into their projects. 

Software and hard physical issues

As an organisation, Arup has long been interested in how the circular economy could reshape built environment practices for the better, and it’s been clear that digital tools will play a key role in making the leap to greater recycling. Lacking a detailed account of existing materials’ current state, attempts at ‘circular construction’ to date mostly involve recasting or chopping elements up for reuse, leading to the higher costs, and production of yet more CO2 emissions, diminishing the value of recycling in the first place.

So how do we increase the quality and quantity of recycled content in the construction process? Most structural calculation software views all materials as ‘new’ and can’t readily work with pre-used elements. So how can used materials be made acceptable to digital platforms that increasingly shape and manage projects?

Firstly, we need to 3D scan the materials’ geometry, then evaluate its structural properties and strengths, before collating these data points in a new digital model, and then formatting this data in ways that programs like Revit or Oasys GSA can understand. For developers and clients hesitant about depending on pre-used steel, glass or concrete, confidence is key. Any circular/digital process will need to do a robust analysis of the material’s current strength and corrosion level, with a credible validation process.

From bin to BIM

Almost all the steps in the process of taking existing building components ‘from bin to BIM’ do in fact already exist and we are currently working on a system that connects the dots in the process flow. Once all the elements are in place, we foresee creating a pilot project that will test at 1:1 scale how key structural elements like steel beams can be identified, integrated in a design, and be recovered to form the basis of a new structure.

The circular path to a net zero built environment

Whole life cycle carbon assessments are becoming the norm, indeed, at Arup we have just committed to carrying them out on all projects – both new buildings and refurbished ones. Indeed, commitments to net zero aren’t really achievable without these assessments. As our own global architecture leader, Nille Juul Sorensen, has observed about the idea of sustainable construction, “we will only really get change if we can design with what’s already available.”

This should lead to growing demand for this level of materials intelligence including insights into past uses, across the industry. A related implication is that design-for-reuse should also lead to architectural forms that are inherently easier to deconstruct ,and thus where a far greater percentage of materials end up reused.

Attitudes (and practices) are changing

There are signs that recycled materials are becoming more accepted by developers; they’re a chance to demonstrate the strength and credibility of net zero commitments in a market where this is now a growing reputational factor. As projects like the refurbishment of 1, Triton Square demonstrate, there is also a increasing interest and perceive commercial value to approaching buildings as forms that can be reimagined in situ, without the need to demolish, waste resources and start over from a blank slate.

Where else might recycling building materials take us? The key is to keep sight of digital tools’ power to scan, identify and catalogue elements at scale. Imagine digitally mapping not just buildings but whole cities, leading to catalogues of ‘available in future’ building components.

At the same time we can easily foresee that design software could intelligently select relevant components to create object libraries or design solutions based on reused building elements. This should not just accelerate circular construction but also help develop a new and honest architectural language that celebrates the composite design approach and not tries to mimic an existing aesthetic using different materials.

Recycling is an old, even timeless idea, but one that can now embody the most ambitious and sustainable outcomes. We’re excited to see where we can take it.