Circularity: Why can’t we recycle buildings as well?

Humans have been building and rebuilding their homes, palaces and walls using the limited resources they had on hand for millennia. Reuse was key, eliminating the need to extract or transport new materials. Egypt’s Giza pyramids, for example, lost their smooth facing of limestone when it was repurposed to build the old city of Cairo.

All of that changed with the Industrial Revolution, which upended the old hierarchy of cost and value. To be effective, went the thinking, it had to be new. As a result, a growing number of buildings and the bulk of their materials were carted off to landfills.

Today, the construction sector is responsible for more than one third of the solid waste produced worldwide. It consumes half of all the virgin raw materials we extract, and generates nearly 40% of the CO₂ discharged into the atmosphere. To tackle the climate emergency, we need to eliminate those emissions by 2050. And given the rising tensions over access to raw materials, it’s clear the time has come for “buildings as material banks.”

Total or partial deconstruction?

Back in 2015, the European Union lent its support to an ambitious research program dubbed BAMB, or Buildings as Material Banks.

The BAMB program immediately led to six construction projects, one of which, known as BRIC (for “Build Reversible in Conception”), was located in Brussels, Belgium. That project involved rapidly dismantling a 70-square-meter office building and then rebuilding it, in its entirety, as a larger, 130-square-meter retail shop. In the years since, the building has been rebuilt once more, this time as a radio broadcast studio. The technique used for the building’s structure – a wood frame assembled without the use of nails or adhesives – borrows heavily from traditional wood framing. The interior work, including the insulation, draws on very contemporary materials, such as wood-fiber gypsum panels and cellulose wadding made from recycled paper: proof that this isn’t all about nostalgia!

The other avenue being explored by BAMB promoters is partial deconstruction. There, as with a conventional building, the structure is built to last as long as possible, but it’s also designed to accommodate continued repurposing and reconfiguration. “How do you maintain the residual performance of a reinforced concrete or metal beam that’s 50 or more years old, once it’s been removed?” says Saint-Gobain Group Circular Economy Leader Xavier Meyer. “It’s much easier when you have solutions used in short cycles, such as interior walls used in commercial buildings, especially if they’ve been designed from the outset to be easily dismantled.”

That was the model used in designing the Olympic Village that will house athletes competing in the 2024 Paris Olympics. The Village’s 120,000 square meters of construction will be entirely converted to office, retail and residential space once the Olympics are over. With that in mind, Saint-Gobain has developed, manufactured and delivered 60,000 m² of next-generation Placo® interior partitions. This uncoated, adjustable temporary divider system includes a unique installation process to ensure it can be removed without a trace, and was specially designed for easy reuse. Says Maïté Ketterer, Circular Economy Director at Saint-Gobain Solutions France, “The Olympic Village is the building of the future: transparently designed and consisting of simple systems and healthy materials that don’t lead to problems later on”.

Industries are venturing into new territory

Recycling or reuse? That’s the second conundrum being debated in resource-based construction. Reuse has the advantage of eliminating emissions generated by a new manufacturing cycle. Recycling, on the other hand, produces higher-performance materials that will minimize the footprint of the buildings they’re used to construct. Each approach can have value, depending on the circumstances.

TO READ: THE SUSTAINABLE CONSTRUCTION PROJECT PATHWAY, FROM SOURCING TO WASTE MANAGEMENT

On one hand, disassembling, transporting, sorting, cleaning, storing and marketing materials for reuse is costly. Only a few operators are currently able to handle that process at scale, such as Belgium’s Rotor, which already offers more than 3,000 products for reuse at its website. It’s a model initiative, but one whose success depends on whether project owners agree to take on the added costs and limitations involved in using secondhand materials. Twenty-three organizations from both the public and private sectors (including Saint-Gobain) have just joined forces to create DRASTIC[1], a new project backed by the European Union. It means to test new solutions organizers hope will prove more competitive. In Germany, for example, the Saint-Gobain Group will be installing, removing and then reconditioning insulation from the outside. The project will also examine topics such as the reuse of metal structure components, construction wood and energy-generating photovoltaic façades. The work is getting underway in October 2023.

With recycling, one obstacle is that virgin raw materials are sometimes available at very low cost. Gypsum, for example, is widely accessible and available in large quantities. There too, Saint-Gobain is positioning itself as a leader, incorporating used plasterboard into its production in Western Europe despite the added cost involved in some countries. That’s helping to lay the groundwork for a long-term recycling infrastructure. Meanwhile, new regulations in France will promote waste sorting at building sites as a first step towards recycling. That’s one way to accelerate the transition to a circular construction industry, a goal Saint-Gobain has been preparing for over many years. “We’re poised to use flat glass from building sites in our glass furnaces on a massive scale. Each tonne of cullet used in the furnaces prevents 700 kilograms of CO₂, all Scopes combined”, says Maïté Ketterer.

Building memory

Whether you opt for partial or total deconstruction, reuse or recycling, you can’t properly recover a building at the end of its life without knowing what it contains! So you have to keep a memory of what was used in the building and a history of each component. Building information modeling (BIM), a digital tool now used in the construction of numerous buildings, seems like the perfect solution. Dutch architect Elma Durmisevic has been active in circular construction for two decades. As part of the BAMB project, she has developed a “reversible BIM tool,” computer software that can measure the reuse potential of every component in a building based on its characteristics: its composition, the initial assembly technique, subsequent treatments or alterations and possibly, in the future, its resale value. Thus, with just a few clicks, the BIM could report on a building’s residual value and describe how it could be disassembled.

TO READ: REAL BUILDINGS, VIRTUAL TWINS: CONSTRUCTING THE FUTURE

In the future, on leaving the factory, every product will need to come with a digital passport bearing all the necessary information about its reusability and recyclability, including, for example, what substances it contains. That’s something the European Union is addressing, since there is currently no standardized format in place. Luxembourg has taken the initiative by proposing one such resource, known as a Product Circularity Data Sheet (PCDS), to which anyone may contribute. Saint-Gobain has, naturally, signed on to that project. “When it comes to hazardous substances, only the European Union has experience with reporting requirements, as part of the REACH regulation for chemicals,” says Pascal Éveillard, Director of Sustainable Business Development at Saint-Gobain. “Elsewhere, notably in the United States, they’ve opted to go the route of voluntary reporting via labels. The ongoing revisions to E.U. regulations on construction products are expected to add provisions for reuse and tighten reporting requirements for environmental performance, particularly with regard to circularity. That’s likely to provide a big boost to reuse and recycling!”