Recycling Pilot Project
Large-Scale Flat Glass Recycling in Winterthur: A First in Switzerland
Every year, 500,000 tons of window glass are discarded in Switzerland, which is about 16 kg per second – the equivalent of a standard kitchen window. Yet for now, none of this glass is recycled to make new window glass. With this pilot project, we aim to prove that circular economy in the Swiss float glass industry is possible!
Every year, 500,000 tons of window glass are discarded in Switzerland, which is about 16 kg per second – the equivalent of a standard kitchen window. Yet, none of this glass is recycled to make new window glass 1:
– 18% is turned into bottles (downcycling)
– 82% ends up in landfills (landfill B)
This is particularly concerning as flat glass is one of the most CO₂-intensive materials in construction: 1 m² of triple glazing emits up to three times more CO₂ than 1 m² of a 20cm thick concrete slab 2.
The Windows of Opportunities project, led by ZHAW with the support of the FOEN (Federal Office for the Environment), Glas Trösch, SWICA and Birchmeiergruppe, will start on June 23 2025, in Winterthur. The goal of the project is to demonstrate that local and circular flat glass recycling is not only feasible but necessary.
While some players announce future industrial solutions, we are taking action: 5 tons of glass will be extracted, sorted, and recycled – without “downcycling.”
Three key steps will take place this summer in Winterthur and will be documented in videos, photos, and scientific texts:
– June 23: Collection of the 375 sashes at the demolition site
– July 9: Manual separation of glass and frames in our hall
– July 16: Collection and departure of materials to recycling facilities
The aim of this project is to prove that a Swiss flat glass recycling stream is technically, ecologically, and logistically viable. It is part of a broader reflection on circularity in the construction sector. With this project, we aim, among other things, to establish a recycling obligation for windows in Switzerland, so they no longer end up in landfills.
Process
Recycling
This summer, ZHAW, together with Glas Trösch Group, SWICA, Birchmeier Gruppe and with the support of FOEN, launched a pilot project on flat glass recycling.
At the SWICA building in Winterthur, 375 window sashes were dismantled, stored and separated by material before demolition. The goal: to reintroduce recycled flat glass into the replacement building designed by Adrian Streich Architekten – creating a closed loop for windows.
Dismantling
Normally, dismantled windows are thrown into containers together with other materials. At the recycling yard, only about 18% of flat glass is downcycled as container glass, while the majority still ends up in waste incineration plants.
In the pilot project, however, the window sashes were carefully dismantled using simple tools – an essential step towards reuse and proper recycling.
Storage
Dismantling sashes is only the first step. To meet strict flat glass recycling standards, storage and transport also matter.
In Winterthur, sashes were lowered by excavator instead of being carried down stairs, and stored vertically in flat containers. A key requirement: the glass had to remain intact to avoid cross-contamination with other materials.
To be followed…
