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ITOKI CORPORATION (Headquarters: Chuo-ku, Tokyo; President and CEO: Koji Minato; hereinafter "ITOKI"), together with Hitachi, Ltd. (hereinafter "Hitachi") and Tokuyama Corporation (hereinafter "Tokuyama"), has demonstrated the upcycling*1 of plate glass recovered from solar panels, a waste-prone issue, into furniture components, with the aim of realizing a resource-circulating society. Specifically, Tokuyama's low-temperature pyrolysis method recovered high-quality plate glass, and Hitachi's non-destructive strength estimation technology evaluated the effects of deterioration such as cracking*2 and alkaline elution*3, making it possible to reuse the plate glass as is. Furthermore, ITOKI has prototyped a conference booth that utilizes the unique characteristics of the recovered plate glass, proposing new value for recycled materials. This will enable the creation of sustainable spaces that are both environmentally friendly and beautiful in offices and public spaces, providing users with a new value experience that combines social contribution and design. This initiative marks the first time that plate glass recovered from solar panels has been reused in office furniture without being crushed*4, and is expected to reduce waste and CO₂ emissions by up to 50% compared to manufacturing new glass, thereby supporting the creation of sustainable social infrastructure. Going forward, in order to commercialize this initiative, we will collaborate with partners in a variety of fields, including office furniture and building materials, to build supply chains, consider business models, and further standardize quality verification and evaluation technologies, accelerating the realization of a decarbonized and resource-circulating society.

From the 2030s onwards, the amount of solar panels discarded at the end of their lifespan is expected to increase, reaching a maximum of 500,000 tons per year in Japan. Against this backdrop, countries around the world, including the European Union (EU), are making recycling mandatory and implementing strict disposal regulations. The plate glass used in solar panels accounts for approximately 60% of their weight, and reusing this glass in a high-value-added manner is crucial to increasing the recycling rate of solar panels. Currently, methods are being considered for crushing the glass and using it as roadbed material*5 or glass raw material. While upcycling plate glass as is offers the potential to create new value, reusing it without evaluating quality degradation, such as cracking and alkali leaching, that occurs during long-term outdoor use poses safety and durability challenges.
To address these challenges, Hitachi, Itoki, and Tokuyama began joint research in September 2024 and embarked on a new initiative to reuse plate glass recovered from solar panels as furniture components.

The features of the technology and solution developed by the three companies to safely reuse plate glass recovered from solar panels while maintaining its high quality are as follows:

Tokuyama has established, through joint research with NEDO, a technology that uses its unique low-temperature pyrolysis technology to recover high-quality plate glass, cells, and interconnectors that make up used solar panels.*6 By optimizing the pyrolysis conditions and processing process, the company has succeeded in turning the main components into raw materials (horizontal recycling). Furthermore, by identifying issues that must be addressed before the plate glass can be directly recycled into products and reflecting these findings in quality control and processing processes, the company is able to supply higher-quality components.

Hitachi has developed a technology to estimate the strength of recovered glass by comprehensively evaluating the impact of cracks and alkali elution, two factors that cause glass deterioration, on glass strength, and combining this with image processing to identify the factors. This enables upcycling of recovered glass while ensuring its safety and durability. Hitachi is also promoting a variety of initiatives, including the creation of a recycled materials marketplace*7, the development of upcycling technologies*8, and the formulation of a grand design at the Hitachi-AIST Circular Economy Collaborative Research Lab*9. In collaboration with these activities, Hitachi aims to implement this technology in society as One Hitachi, expand the lineup of recycled materials marketplaces, and realize a harmonized society where the environment, happiness, and economic growth are in harmony.

ITOKI has created a prototype web conference booth that retains the minute irregularities of recycled glass and uses them as a design material to block views. In order to efficiently reuse recycled glass, which has limited thickness and uneven sizes, safety is taken into consideration by using laminated glass, and the panel structure was redesigned to maintain strength by mixing glass and steel surfaces. By proposing new value for recycled materials, it also contributes to raising awareness of the SDGs*10. The prototype also combines upcycled materials, which ITOKI has been working on, for the tabletop material and sofa upholstery.

By estimating the strength of the recovered glass and processing it into laminated glass, it was confirmed that it could be used as a component for office furniture. It was also estimated that CO₂ emissions could be reduced by up to 50% compared to manufacturing new glass*11.

Going forward, the three companies will collaborate with partners in a variety of fields, including office furniture and building materials, to build supply chains, consider business models, and further standardize quality verification and evaluation technologies in order to meet the needs of many customers seeking the development of sustainable products. By calling for collaboration and standardization across the industry, they will accelerate the realization of a sustainable, decarbonized, and resource-circulating society and the implementation of recycling in society.
Part of the results of this study will be presented at the 2025 Joint Autumn Conference of Resource and Materials-Related Academic Societies, to be held at Hokkaido University from September 2nd to 4th, 2025.