Circular Economy: Material Flows and Sustainable Materials – Practical Applications

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2.14

Contemporary Wood Buildings: Botanikern in Uppsala

Now we will shift focus to the construction industry, an area responsible for a significant portion of global resource consumption and carbon emissions. We explore how mass timber construction, specifically using materials like Cross-Laminated Timber (CLT), could be a strategy for improved circularity.

The Botanikern housing complex in Uppsala, built in 2019, is our first case study, looking at how bio-based, carbon-storing materials can reduce embodied energy and enable future material reuse. In the video below you get a tour of the building from the architects that designed Botanikern.

The Case for Mass Timber Construction and Cross-Laminated Timber

Globally, the construction industry is highly linear and resource-intensive, with the production of cement and steel alone accounting for large environmental footprints. Switching to wood, a bio-based and renewable material, fundamentally alters this equation by leveraging two key circular benefits:

Carbon Sequestration: As trees grow, they absorb CO2 from the atmosphere. When converted into mass timber products like CLT (a structural wood panel made by layering and gluing boards), the carbon remains stored within the building for its entire lifespan. This effectively turns the building into a carbon sink.
Lower Embodied Energy: Wood requires significantly less energy to process and manufacture into structural components compared to steel or concrete. This drastically reduces the embodied carbon footprint of the building before it is even used.

CLT is a key innovation in mass timber, allowing for the construction of tall, structurally sound buildings. Its benefits include required strength, fire resistance, and the ability to be prefabricated off-site, leading to faster, quieter construction with less on-site waste.

For timber construction to be truly circular and not merely a ‘less bad’ linear choice, the entire system must be redesigned. A circular building goes beyond using sustainable materials, it must be designed for an eventual second and third life through the following principles:

Sustainable Sourcing: The timber used must come from responsibly managed forests, ensuring the resource is truly renewable and supporting biodiversity.
Design for Disassembly: Components must be joined using reversible connections (screws, bolts) rather than irreversible glues or welds. This allows structural elements to be deconstructed at the end of the building’s life and reused as structural elements elsewhere, maintaining their highest value.
Material Passports: Documentation should track all materials and components within the building, making it simple for future owners or deconstruction crews to identify and reclaim valuable resources.
Cascading Use: When structural reuse is no longer possible, the timber should be repurposed in a ‘cascading’ fashion (from structural beam to furniture to particleboard), maximizing its use before final, responsible recycling or use for bioenergy.

Part 1 | Part 2 | Part 3 | Part 4 | Part 5

Contemporary Wood Buildings: Botanikern in Uppsala

The Case for Mass Timber Construction and Cross-Laminated Timber

Further reading, learning and references