Zurich's pioneering work in CO₂ separation at Werdhölzli: a 178 million investment in our future
The city of Zurich has made a groundbreaking decision: The voters approved a loan of 178 million Swiss francs for a CO₂ separation plant at the Werdhölzli wastewater treatment plant approved. The project promises to remove 200,000 tons of CO₂ from the atmosphere over the next ten years. But what does this investment really mean for our climate future?
The need for carbon capturing
One thing is becoming increasingly clear: without active CO₂ removal from the atmosphere or directly at source, e.g. at sewage treatment plants, waste incineration plants and cement works, we will not achieve our climate targets. Carbon capturing is no longer an option, but a necessity on the road to net zero. As a society, we must accept and bear the associated costs.
"As a society, we need to start understanding that we urgently need carbon capturing for net zero and that it will cost something."
The cost issue
At CHF 890 per tonne of CO₂, the project is at a realistic level by international standards. Swiss Re, for example, pays a similar amount to Climeworks for its plant in Iceland. By way of comparison: the Climate Cent paid CHF 600 per tonne until 2023, while the Swiss Confederation now expects to pay CHF 430 per tonne, e.g. for infrastructure projects.
Technical implementation and challenges
The project aims to capture 20,000 tons of CO₂ per year:
10,000 tons are to be transported to Norway by rail and stored in empty oil fields
The other 10,000 tons are intended for local use, probably in concrete construction
The concrete problem
One interesting aspect is the limited absorption capacity of CO₂ in recycled concrete. With around 5-10kg of CO₂ per cubic meter of concrete, the planned 20,000 tons would theoretically require 4 million cubic meters of concrete - which corresponds to around a quarter of Switzerland's annual requirements. This clearly shows the current limits of this technology.
Open questions on CO₂ balancing
The creditability of CO₂ storage remains a key question: Who owns the "sink capacity" from Werdhölzli?
a) The City of Zurich, which pays for and operates the facility?
b) The processing company that puts the CO2 into the crushed waste concrete (and currently sells it to third parties)?
c) The concrete supplier who turns this granulate back into concrete or
d) the end user, i.e. the property owner?
These questions still need to be clarified. Interestingly, business cases worth millions are currently being financed on model b).
Alternative approaches with OPENLY
OPENLY sees buildings as CO2 storage sites. For comparison: the CO2 stored in the Valley Widnau pilot project using biochar alone has a sink capacity of 70 tons. The total project with structurally installed biogenic building materials amounts to 750 tons. These sink performance can be certified with immediate effect.
"27 OPENLY projects (400 apartments) per year would have the same effect as the entire Werdhölzli complex."
Conclusion
The approval of this pioneering project in Zurich is an important step in the right direction as it will initiate the establishment of an entire ecosystem of CO2 capture, transportation and storage. As one of the wealthiest countries in the world, Switzerland not only has the means, but also the responsibility to develop and scale up such technologies. Only through practical experience can we make the necessary progress in the fight against climate change. Because CO2 is a physical problem - it can only be solved with hardware.