A large quantity of solar panel cover glass is expected to reach the end of its useful life and be disposed of in the late 2030s, giving rise to concerns about a serious environmental impact. The success of this recycling trial opens possibilities for more extensive reuse.

In October of 2023, AGC was first in Japan to successfully conduct a demonstration test to recover glass from used solar panel cover glass that has reached the end of its use. Then in March of 2024, the same solar panel cover glass was used as raw materials for the production of float glass—the first successful demonstration test of its kind in Japan. In addition to reducing industrial waste, our new technology is expected to make possible the previously technically difficult feat of recycling cover glass for float glass.

Photovoltaic power generation has become a focus among renewable energy sources. However, the useful life of solar panels is estimated at 20 to 30 years, and several hundred thousand tons are expected to be disposed of annually starting in the late 2030s. Cover glass accounts for approximately 60% of the total weight of these panels, and the serious environmental impact of landfilling and disposing it as industrial waste is raising concerns. The company has succeeded in recycling cover glass into figured glass as of 2023, but recycling it into the more versatile float glass has proven difficult.
However, this successful test has led to expectations that horizontal recycling of waste cover glass into high production output float glass will be possible.

We spoke about the current initiatives with cover glass with Yoshihiro Nagao, Group Leader of the Sustainable Management Initiatives Group, Architectural Glass Asia Pacific Company.
“The amount of solar panel cover glass produced in Japan is very small and we are not producing any at present. Most is imported from China. This is because China has a huge production volume at low prices. However, if this continues, industrial waste will continue to increase. This makes us feel that Japanese flat glass manufacturers should start talking about the issue, so we discussed the matter within the company and decided to take on a new recycling project.”

Why does glass turn into industrial waste? This is not widely known, but the reality is glass is not yet actively recycled. Glass would appear to be a material that could be dissolved and reused many times. In truth, like plastic bottles, glass bottles are legally recycled in accordance with the Containers and Packaging Recycling Law, but it is not legally mandated that glass used in buildings and automobiles—including solar cover glass—be recycled. Therefore, most glass is disposed of in landfills as industrial waste or downcycled into roadbed material for asphalt roads.

The basic glass manufacturing process uses sand as the main raw material. It’s melted at high temperatures in a furnace to produce transparent glass. Typically, in addition to sand, glass cullet produced during the manufacturing process is also used as a raw material. However, cover glass and glass dismantled from buildings often contains impurities that adversely affect glass production, reducing productivity and possible causing defects. This means using raw material cullet externally collected carries a high risk.

Glass is a delicate material, so it can’t be made into a product if it has a different composition or contains impurities. Also, the difficulty of recycling varies between figured glass and float glass. Mr. Naoya Kobayashi, manager of the same Group, provides the following context.
“The type of glass product is determined by its application, and different types of glass products are manufactured in different ways. Cover glass is often made using the figured glass manufacturing method. Cover glass contains an impurity called antimony, which has a negative impact on the float manufacturing process. Therefore, it’s difficult to recycle it into float glass.”

However, the company has been researching suitable processing methods for flat glass recycling for several years. With their recent success in recycling it as float glass, it is now possible to expand recycling to a wider range of materials.
“Currently, we are looking beyond only solar cover glass, and are conducting research and development to find ways to recycle glass from buildings and automobiles,” says Mr. Nagao.

What new issues will arise in the future of recycling of cover glass? We asked Mr. Nagao.
“It’s a question of economics. In general, people think that recycling will make glass cheaper, but in fact, it becomes more expensive. Therefore, if recycling is more expensive, customers will inevitably prefer to buy the new, cheaper products. But in the future, the price of glass will start to rise as landfills for disposal fill up and disposal costs rise. In that sense, right now we are merely postponing the problem. So rather than not do it because it’s not economically viable, we are engaging in recycling with the idea in mind that the problem won’t be solvable unless we start working on it now, for the sake of the future.”

Another complication is establishing a supply chain to recover glass, which is also an issue of economic feasibility. Further, the creation of partnerships with other companies is another issue to be addressed. Currently, Shinryo Corporation, a member of the Mitsubishi Chemical Group, is investigating the recovery of solar cover glass that has undergone heat treatment.
Mr. Nagao on this topic: “In general, people don’t know that glass can be recycled, or that it isn’t being recycled. At our company, we are hearing about advanced initiatives in Europe, so we believe that we need to use this initiative to expand public awareness toward glass recycling.”

In its medium-term management plan AGC plus-2026, the AGC Group defined three types of social value that it wants to create through its products and technologies. One of these is “Blue planet,” the Group aims at reducing the environmental impact of its products from raw material procurement to use by customers toward the realization of a sustainable global environment. The company will continue to provide value to society by accelerating the effective use of resources.

We believe that recycling glass could generate a great deal of social value. It is in line with trends like creating a circular economy. And since sand is a finite resource, promoting recycling can protect the planet’s resources. And it would also be effective from the standpoint of security. Going forward, we want to continue to promote recycling in cooperation with many people,” says Mr. Kobayashi

The AGC Group has reclarified the values that it will contribute to society, by replacing the existing "five social values" with "three social values" to be created by the Group’s products and technologies.

“Up to the time I entered my current position, I was single-minded about glass production. I didn’t think at all about what happened next. However, we’ve heard that Tokyo will run out of reclaimed land for disposal use in 20 years, and disposal is still occurring rapidly. What should we think about the current situation? Questions of economic rationalization remain, but AGC is making every effort to move closer to a circular recycling society, for the sake of our future.”