The building sector is developing concrete measures to reduce its carbon footprint, particularly in the production of concrete and steel. Christian Paglia, a leading expert in construction materials, observes significant progress, although several technical standards still require adaptation.
According to the Federal Office for the Environment, the manufacture of construction materials accounts for around 10% of Switzerland’s greenhouse gas emissions – a figure largely driven by cement and steel production. To advance its transition towards a low-carbon model, the construction sector – valued at nearly 35 billion francs, or 5% of GDP in 2021 – is reinventing itself through new, less energy-intensive materials and processes, such as LC3 concrete. Experts are also prioritizing the reuse of components and the integration of end-of-life planning for buildings, as highlighted by Christian Paglia, Director of the Institute for Materials and Construction at the University of Applied Sciences and Arts of Southern Switzerland (SUPSI).
What technical solutions are currently available to reduce CO₂ emissions from concrete production?
Christian Paglia: The priority is to adopt solutions that can partially replace Portland cement – the traditional clinker-rich cement whose production generates large volumes of CO₂ – with lower-emission alternatives. One of the most promising today is LC3 cement, which contains a high proportion of calcined clay and limestone. The Aargau-based company JURA has developed a 100% Swiss LC3-type cement. Researchers are also investigating other options, such as incorporating agricultural residues (rice husk ash, wood litter) and clean incineration waste with low heavy-metal content into cement formulations. The standards issued by the Swiss Society of Engineers and Architects now permit the certification of alternative cements, provided they deliver the same mechanical performance as conventional concrete. For example, CEM VI cement integrates recycled demolition materials.
Another key factor is reducing transport distances using locally sourced materials. This not only lowers emissions but also strengthens local manufacturing and recycling supply chains, making the sector less reliant on imports.
Steel is also a major source of CO₂ emissions. How can it be made less polluting?
Paglia: One of the most effective processes is to recycle steel. For the same volume, recycling steel from scrap emits roughly 50% less CO₂ than producing it from ore. Today, all steel produced in Switzerland comes from this recycling process, which uses electric arc furnaces rather than far more polluting coal-fired blast furnaces. To further reduce the carbon footprint, direct reuse of steel components – without sending them through the recycling process – should also be encouraged. This practice already exists, but large-scale adoption faces two major hurdles: the lack of clear standards governing reuse, and the need to assess the condition of components at the end of their service life.
Architectural planning is also an important factor in reducing the sector’s carbon footprint. What are the current challenges in this area?
Paglia: Builders and property owners are increasingly considering a building’s end-of-life stage with a view to reusing materials. Solutions exist to strengthen reuse potential, notably by promoting the standardization and prefabrication of components. However, the sector still lacks clear guidelines for improving prefabricated elements and assembly methods.
For companies, what economic opportunities arise from decarbonization?
Paglia: A shift in material technologies can be seen as a major opportunity to add value to local resources. For example, priority can be given to using locally sourced wood ash to replace imported components. Another solution is to reuse the muddy cementitious residues from concrete mixers. Instead of sending these residues to landfill, they can be incorporated into concrete production to reduce the share of Portland cement – the main source of CO₂ emissions. At SUPSI, we are currently developing projects along these lines in cooperation with a regional concrete producer.
Innovative projects have successfully constructed buildings with low CO₂ emissions and even turned them into carbon sinks, notably by utilizing hempcrete. Are these solutions promising?
Paglia: Hempcrete offers interesting properties for thermal and acoustic insulation. In terms of reducing environmental impact, it has clear advantages; however, it can also be more challenging to reuse because it does not possess exactly the same mechanical properties as conventional concrete. It is also essential to ensure that the hemp used comes from sustainable sources.
