Circular solution for flat glass

As a glass manufacturer, French-based Saint-Gobain has faced a challenge when it comes to finding recycling solutions to make flat glass circular.

– By 2025, we want to use 20% of “end of life” flat glass from demolitions in our raw materials. Today, we use 1%. But at the same time, 35,000 tonnes of flat glass per year is put into landfills in Sweden, says Oskar Storm, Architectural Projects Specification Manager at Saint-Gobain.

While flat glass is sometimes recycled into other products, Storm and Saint-Gobain see greater potential for a circular transition.

– 98% of all glass bottles and jars are recycled today, often circularly. But old flat glass is used to make glass bottles or fibreglass insulation at best, if it’s not immediately deposited into a landfill. The only way to truly recycle flat glass is by using old flat glass, says Storm.

Saint-Gobain has thoroughly explored all the possible ways flat glass can become a circular product. It includes a collaboration with the Research Institutes of Sweden (RISE), which launched the ”Increased circular use of flat glass” project. It was through the search for partners and pilot projects that Saint-Gobain connected with Ragn-Sells.

– We sought out projects where we could apply our newfound knowledge, visiting glaziers and facade builders, says Storm. Wherever we went, everyone mentioned that they wanted to involve their recycling services provider, Ragn-Sells, so we contacted them.

One pilot project that Saint-Gobain and Ragn-Sells are currently collaborating on is the replacement of the glass facade at SAS's head office in Solna, Sweden. Ragn-Sells collects the old flat glass and, because there is no plant in Sweden, transports it to Saint-Gobain's float plant in Germany.

Camilla Sonnentheil, Head of Business Development at Ragn-Sells Recycling Sweden, is working to find more circular solutions, especially for construction waste.

– In normal cases, old flat glass from demolition projects ends up in landfills, but here we bring it back to the factory in Germany instead, where it can become new again and thus becomes circular. There is certainly a footprint from the transport, but the reduced carbon dioxide emissions in a circular solution can offset it by leaps and bounds, says Sonnentheil.

According to Saint-Gobain's calculations, 1,000 kilograms of shards from discarded flat glass can replace 1,200 kilograms of raw materials needed to produce 1,000 kilograms of new glass. And so the process saves 300 kilograms of carbon dioxide.

– Recycling flat glass is a sensitive process with high purity requirements. It needs further development, but we are well on the way. Above all, there is an enormous desire to find new paths forward, which marks an incredible difference compared to just two years ago, says Storm.