ETH Zurich, one of Europe’s leading universities in science and technology, is exploring alternatives to reduce the climate impact of construction. Concrete and steel dominate the building sector, but their production releases large amounts of CO₂. Researchers and architects at ETH are turning back to natural resources such as earth, straw, and timber. Their work focuses on updating these materials with modern techniques to make them fit for contemporary use.

Natural Materials and Climate Benefits

Renewable resources like wood, earth, and straw require less energy to produce than conventional materials. They also act as carbon stores. As these resources grow, they absorb CO₂ from the atmosphere. When used in construction, this carbon remains locked in the building for decades.

In Switzerland, about 50 million tonnes of soil are excavated every year, most of which is discarded. Using clay-rich soil for construction instead of sending it to landfill could reduce waste, cut transport emissions, and support local supply chains. Natural materials can also improve indoor climates. Studies show that they can reduce allergies and asthma.

Updating Traditional Techniques

The challenge is to adapt old methods to today’s needs for durability, efficiency, and cost control. ETH researchers are testing prefabricated earthen components and new mixes such as “liquid earth,” which can be poured like concrete. Straw is also being re-examined as insulation. It regulates humidity and provides thermal comfort, but its role as a load-bearing material remains limited.

Architect and ETH Professor Roger Boltshauser has long worked with rammed earth, where layers of soil are compacted into solid walls. His team designed the kiln tower at the Brickworks Museum in Cham, the first prestressed earthen structure. Combining earth with timber or steel reinforcement makes it possible to use the material in larger projects.

Timber Research

Timber is another focus at ETH. It is renewable, lightweight, and strong, while also storing carbon. Prefabricated timber elements are already popular in Swiss cities, especially for extensions and additional storeys. Professor Ingo Burgert’s team is working on ways to improve wood’s resistance to water, sunlight, fungi, and insects. They use bio-based treatments such as shellac and tannins to avoid harmful chemicals.

As spruce trees struggle with climate change, researchers are also looking at other species. They are testing techniques such as split wood, which makes better use of each tree.

Towards Wider Use

Earth, straw, and timber still represent a small share of the building market. To encourage broader adoption, ETH has launched the Atlas of Regenerative Materials. This platform highlights projects that use natural and bio-based materials. It aims to show that these resources, when combined with modern technology, can meet today’s standards while lowering the environmental footprint of construction.

Source: ETH Zurich
Image: Sandro Livio Straube / Empa