Best-in-class concrete: Same carbon footprint. Twice as expensive. Why?
The second phase of our OPENLY Valley Widnau project is just around the corner—and we’re focusing on transparency and practicality. For the first time, we’re using two different concrete concepts with nearly identical carbon footprints but very different approaches and cost structures.
Biochar concrete from CarStorCon®
In Phase 1, we relied on biochar concrete from CarStorCon® Technologies: 904 m³ of concrete with a standard CO₂ emission of 238 kg per m³, of which 53 tons of CO₂ were offset by biochar—resulting in an impressive net balance of just 179 kg of CO₂ per m³. The additional costs amount to around 400–500 CHF per ton of CO₂—a certifiable process that enables active CO₂ sequestration.
Eco-concrete from Holcim & Vicat
In Phase 2, we are using newly available eco-concretes from Holcim EcoPlanet and Vigier Ciment Progresso. With 340 m³ of concrete, we achieve a CO₂ footprint of 175 kg per m³, but through avoidance rather than offsetting. The additional costs here amount to approximately 200 CHF per ton of CO₂—though this cannot be certified.
The concrete for both phases was developed by Sigmund Sieber AG, delivered using electric mixers, and installed by Gautschi AG.
What does this mean for you as a developer or investor?
There is no simple answer from SIA, Minergie, or DGNB that tells you which path to choose. The key question is rather: How do you want to achieve your carbon footprint? Do you want to actively sequester CO₂ and have it certified, or do you prefer to avoid emissions at a lower additional cost?
Anyone can build to standard. But a comparison of our two phases makes one thing clear: at the systemic level, there is no clear price on CO₂, no incentives, and no legal requirements. At OPENLY, we are committed to closing this gap and making sustainable construction measurable and transparent.
If you’re interested in seeing these two “concrete concepts” in person, come visit us in Widnau (public tours are held on the last Thursday of every month) and experience innovation and responsibility in construction—firsthand and up close.
We look forward to hearing from you!