By Susanne Togeby, AAU Communication og Public Affairs
Photo: BioMat, Evgenia Spyridonos

The built environment significantly contributes to global CO₂ emissions, and there is an urgent need to reconsider traditional materials and methods.

That’s the message from Hanaa Dahy, Associate Professor at Aalborg University, who researches development, design, and application of bio-based and regenerative materials.  She is the architect behind two bridges made of flax fibres, with the latest and strongest built in Ulm, southern Germany. She explains:

“Biobased materials – especially those made from rapidly renewable resources such as flax or hemp – are crucial for reducing the environmental footprint of the construction industry. The current dominance of cement, aggregates, and metals contributes to nearly 40% of global CO₂ emissions. If we are serious about climate goals and resource efficiency, we must rethink how and what we build with.”

Flax fibres can match the strength of steel and concrete

Compared to the previous two bridges made from flax fibres, the latest version is both lighter and stronger. It measures 5.34 metres in width and spans 9 metres in total.

A bridge made from flax may sound fragile, but when flax fibres are combined with other materials, they can attain properties similar to steel or concrete, explains Hanaa Dahy. At the same time, the materials are lighter and more flexible. The bridge weighs only 5 tons but can carry up to 24 tons.

The Ulm bridge is equipped with sensors that monitor the structure and ensure its long-term safety and durability. These sensors are also linked to a musical system that turns the bridge into a kind of instrument when walked on.

Strong Enough to Carry an Ambulance

According to Hanaa Dahy, the technology can be scaled up and applied to larger construction or infrastructure projects.

“The bridge in Ulm is intended for pedestrians and cyclists, and in special cases it could even carry an ambulance. But the technology has the potential to be scaled up and used in larger building or infrastructure projects. The first bridge, located in Almere, spans 15 metres – a major milestone demonstrating its viability,” says Hanaa Dahy.

She also notes that with the rising awareness of material scarcity, carbon neutrality goals, and the need for circular solutions, biobased materials will not only complement but potentially replace mainstream materials in key applications across infrastructure and architecture.

About Hanaa Dahy

Hanaa Dahy is an architect and researcher focusing on the design and application of biobased and regenerative materials at the BioMat@Copenhagen Forskningscenter.

Internationally, she contributes to educating professionals on how to build with future-proof materials.

Se mere på Hanaas Dahys profil

Translated by: Susanne Togeby