Discovering "New Value" from Discarded Roof Tiles that had been Regarded as a "Nuisance"ECO SYSTEM Inc


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Kanazawa Castle Park (left) and Hibiya Park (right) where the road is paved with products made from discarded roof tiles

Product Name = "K-Ground Series," "Kawara Chip," and "Kawarakabe" made from Discarded Roof Tiles

For Suppressing the Heat Island Effect and Reducing the Risk of Urban Flooding

Roof tiles (“Kawara”) are commonly used in Japanese architecture. A large amount of roof tiles are discarded at the time of building demolition and re-roofing. Since they are heavy and difficult to process or recycle, they used to be considered a "nuisance" at construction and demolition sites.

To effectively use such discarded roof tiles, ECO SYSTEM Inc. has developed the “K-Ground Series.” ECO SYSTEM makes use of discarded roof tiles as aggregate for road and other pavement materials by crushing and processing them into gravel or other sand products. K-Ground Series products have excellent water retention and heat insulation. Compared to asphalt, the surface temperature of roads paved with K-Ground Series products is 10°C lower in the summer, which means that they can be a promising solution for suppressing the Heat Island Effect. Another advantage of K-Ground Series products is that the property of permeability can be added. With this property, they can contribute to reducing the risk of "urban flooding" caused by sudden torrential rains that occur more frequently in recent years.

In addition to the K-Ground Series, the company has commercialized "Kawara Chip," roof tiles crushed to gravel size for being used as a gardening material, etc., and "Kawarakabe," a highly moisture-absorbing and desorbing wall material made from roof tiles crushed to sand-size particles. A great deal of new value is being created from discarded roof tiles that had once been regarded as a "nuisance."

Successfully Added Diverse Features by Effectively Taking Advantage of Porosity

The company’s products have various features, which are enabled because the roof tiles are porous. Since the products are porous, which means that they have large surface areas with lots of space, they are expected to retain water continuously when it rains, while also being less likely to heat up. Urban flooding in recent years is often caused by heavy rain quickly traveling through gutters and concentrating in rivers. The K-Ground Series can be an effective countermeasure against such disasters because roads paved with K-Ground Series can absorb the rainwater, reducing rainwater inflow into rivers and returning it to the ground. This mechanism also contributes to the natural recycling system.

Generally, porous materials are not suitable for pavement aggregates due to their low strength. However, the company promoted research and development of the K-Ground Series and other products around 1998, when society's environmental awareness was not so high, with a passion for doing business that contributes to ecology. The company has continuously improved its products through joint research with the local Kanazawa Institute of Technology and the Japan Advanced Institute of Science and Technology, and dozens of other companies.

Scaling Out Know-how Regarding Discarded Roof Tile Recycling, Taking Into Consideration Overseas Expansion

The company is also developing the "mobile concrete plant," which produces paving materials at the sites where they are needed.

The company’s products have been used in the Kanazawa Castle Park, Hibiya Park, and other places. The company is also receiving requests for construction from all over Japan, and the requested construction area totals about 5,000 to 20,000 square meters per year. The products have been getting favorable reviews from users, and many users have become repeat customers. However, there is one concern that discarded roof tiles are heavy, so transportation costs are high. To address this issue, the company is promoting franchising by expanding its roof tile recycling know-how to companies across Japan. The company is also successful with recycling "bricks," which have properties similar to roof tiles. Further, it is also developing the "mobile concrete plant," which can produce paving materials in various locations. With advantages such as its "recycling know-how" and "mobile concrete plant," the company intends to expand its business into countries with a roof tile culture, and even into countries with a brick culture, where the market potential is even greater.

In addition to the products and know-how the company offers, the story of "having created new value out of a nuisance" can also have the potential to help many companies make breakthroughs.

Coverage date October 19, 2020

Company Overview


The company was established in 1994. It promotes the discarded roof tile recycling business with partner companies. Currently, it offers pavement materials with water permeability, water retention, and heat insulation properties in 33 prefectures in Japan.

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