A new initiative in Japan aims to transform the way window glass from buildings is recycled. Three major companies, Sekisui House, Daiei Kankyo and AGC, have announced the launch of the country’s first demonstration project for circular recycling of architectural window glass. The project will begin in the Kansai region in March 2026.

The initiative introduces a closed-loop or “horizontal recycling” model, where window glass removed during building renovations is recovered and recycled into new window glass of equivalent quality. This approach contrasts with the current situation in Japan, where much of the glass waste generated during demolition or renovation is either landfilled or down-cycled into lower-grade products.

Japan produces more than 500,000 tonnes of waste window glass every year, making improved recycling methods increasingly important for both environmental and resource-efficiency reasons. By recovering glass directly from discarded window sashes during renovation projects, the demonstration project aims to show how this material can be reused as a valuable raw material for new architectural glass.

Within the project framework, Sekisui House will collect and consolidate discarded window sashes from renovation works. Daiei Kankyo will dismantle the sashes and carefully separate the glass, establishing processes to ensure consistent quality and traceability. The recovered glass will then be processed by a specialised recycler into high-purity cullet.

Using this recycled cullet as part of the raw material mix, AGC will manufacture new architectural window glass that meets the same performance and quality standards as glass produced from virgin materials.

The initiative is expected to help reduce industrial waste, lower landfill volumes, conserve natural raw materials and decrease greenhouse-gas emissions, as recycled cullet melts at lower temperatures than newly extracted materials.