Accelerating much-needed circularity for construction glass
When we think of recycling glass, we would probably think of glass bottles and jars. That is a part of the circular economy which many take part in directly and habitually, when we rinse, sort, and deposit glass in recycling bins. Thanks to established collection systems and widespread public awareness, recycling rates for these products are as high as 80 cent in Europe and Japan.
Other types of industrial glass, however, are lagging in circularity.
In some regions, recycling rates of flat glass used in buildings, such as windows and facades, are still at single digits. When houses and buildings are demolished or dismantled, much of this glass is crushed with other materials and sent to landfill or downcycled into products such as glass wool. The circular recycling of windscreens from scrapped cars and glass from used solar panels is also very limited.
All of this is indeed a waste, because glass is extremely well-suited for recycling.
Main markets for flat glass in Europe
Buildings
The largest flat glass market is the building industry, which accounts for more or less 80% of the output.
Transport
About 15% is processed into glazing for the automotive and transport industry.
Other
The 5% remaining is shared between glass for many different applications such as solar applications, appliances (for example fridges or ovens), electronics, furniture, etc.
Source: Glass for Europe
“In theory, glass can be recycled infinitely. It can be melted and moulded to be reborn as the same product with no loss in quality or function, provided it is properly sorted and uncontaminated,” explains Shigeki Yoshiba, President of Architectural Glass Asia Pacific Company at AGC, a global glass and materials company.
The environmental benefits of glass recycling are multi-fold. Foremost is a reduction of the greenhouse gas (GHG) emissions released when extracting and transporting raw materials as well as from fuelling furnaces and directly emitted from melting raw materials. Broken or refuse glass used in recycling – known as cullet – melt at much lower furnace temperatures compared to raw materials like sand or soda ash, thereby reducing energy usage and GHG emissions. AGC estimates that, by replacing virgin raw materials with cullet, greenhouse gas emissions can be reduced by approximately 0.5 to 0.7 tonnes per tonne of glass produced. When calculated as a percentage, 17 per cent of Scope 1 and 2 CO2 emitted in the process of melting flat glass can be cut by using recycled glass, according to the Flat Glass Manufacturing Association of Japan.
Ratio of CO2 emissions (Scope 1 +2) from the flat glass melting process, by source of emissions
* CO2 emitted from raw materials during the dissolution of raw materials
** Reduction of CO2 from heavy oil by replacing virgin raw materials with cullet
Source: Flat Glass Manufacturing Association of Japan
Recycling can also reduce the environmental costs of extracting raw materials from sand pits and quarries, and help raw material importing-countries like those in Europe and Japan secure key ingredients such as silica and soda ash, which have been subject to export bans by key producers.
Recycling can also reduce the environmental costs of extracting raw materials from sand pits and quarries
Consumers, too, are also looking for more circularity and are willing to provide support to make it happen.
“More customers – from general contractors, housebuilders, even convenience store companies – have been contacting us about how we can help them recycle glass used in their buildings,” says Yoshiba.
Circularity for construction glass
However, achieving circularity in construction glass is not as easy as recycling empty bottles or jars.
Separating glass while dismantling or demolishing a building is labour-intensive, time-consuming, and costly, especially when ensuring it is not contaminated with other materials. Even small traces of impurities in cullet can make it unusable for producing flat glass. Moreover, dismantling, collection, and transporting used glass involve multiple actors who need to be brought together.
“We have been trying to take the lead in developing recycling supply chains as we have many contact points and influence across many players, with top market share in Japanese and European markets,” explains Yoshiba. “AGC also has technical expertise such as how to prevent contamination and the efficient use of cullet.”
Closing the construction glass loop
Source: Glass for Europe
Recently AGC has orchestrated a scheme successfully recycling construction glass from two large buildings in Japan and Europe.
Working together with general contractor Shimizu Corporation, AGC recycled 196 tonnes of glass from a dismantled skyscraper in central Tokyo, reducing CO2 emissions from the plate glass production process by approximately 100 tonnes. In Brussels, cullet collected from a large building is being recycled to produce glass with a reduced carbon footprint compared to standard glass. Both projects achieved economic feasibility, explains Yoshiba.
The next step, and greater challenge, is recycling glass from smaller residential homes, which collectively generates more used glass than large buildings. This will require not just creating a recycling system, but also designing glass products to be more easily dismantled and therefore recycled at the end of their use.
Recycling solar panels and automotive glass
Another significant and untapped source of cullet for recycling is the glass used in automotives and solar panels.
AGC is currently working with various partners on schemes for recycling glass. In March 2024, the company demonstrated that it could recycle cover glass for solar panels. With many solar panels deployed in Europe and Japan coming to the end of their 20-to-30-year lifespan, efforts are accelerating across the industry to explore feasible solar cell recycling schemes.
In March 2024, the company demonstrated that it could recycle cover glass for solar panels
Added to these market developments are recent regulatory pressure to recycle flat glass. Japan has enacted a law promoting waste reutilisation to achieve a circular economy and a new law addressing the recycling of solar panel glass is under consideration. These measures are expected to support the expansion of recycling for both construction glass and solar panel glass. In the EU, industry associations are calling for more regulations, including bans on landfilling of construction glass and frameworks to incentivise selective deconstruction, sorting and recovery of construction glass.
“To achieve a circular economy, it is the responsibility of glass manufacturers to draw out the full potential of glass,” says Yoshiba. “With this basic stance, we are fully engaged with the challenge of recycling glass.”