Potential for biogenic carbon storage towards a net-zero built environment in Switzerland

The built environment is a major contributor to global greenhouse gas (GHG) emissions, posing challenges for achieving net-zero targets by 2050. This study examines the potential of an increased use of biobased materials in the Swiss residential building stock to mitigate emissions while increasing biogenic carbon storage. Using a Python-based building stock model, the study evaluates the effectiveness of increasing the share of biobased materials in both renovations and new constructions under different scenarios compared to climate goals. Results indicate that renovations will become the dominant driver of building stock emissions and biogenic carbon storage potential by 2050. While new construction activities will decline due to demographic trends, renovations will contribute nearly four times more to GHG emissions than new buildings. Nevertheless, new constructions are more effective at storing biogenic carbon, achieving a biogenic-to-emissions ratio of 300 % by 2050, compared to 176 % for renovations. By mid-century, the yearly biogenic carbon storage in buildings could reach 2.5 Mt. CO₂, approaching a balance with yearly GHG embodied emissions. However, even in the most optimistic scenario, increasing biobased material use alone reduces cumulative emissions by only 5–8 % compared to business as usual, underscoring the need for additional emission reduction strategies, including decarbonizing material production and reducing construction activities. The long-term analysis reveals that biogenic carbon storage potential is constrained by demolition rates (assuming full re-emission at the end of life), with a higher demolition rate accelerating carbon turnover and limiting storage capacity. A cumulative maximum biogenic carbon stock of 300–400 Mt. CO₂ is projected in the long-term, surpassing Switzerland's expected cumulative net emissions removals by 2050 by 6 times. This study highlights the built environment's potential as a long-term carbon reservoir and emphasizes the necessity of targeted renovation strategies, regulatory policies, and material production improvements to achieve climate goals effectively.