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The development of "near-natural rivers," which began in 1990 with the aim of preserving the environment of rivers and their surrounding areas and restoring ecosystems, has finally begun in earnest following the enactment of the revised River Act in 1997 and other related measures. Along with this, there has been a shift away from traditional concrete revetments and river improvements toward construction methods that utilize vegetation and natural materials. Ahead of this trend, Senior Managing Director Toshiaki Sato and Nippon Naturock have been engaged in the development and promotion of porous civil engineering materials utilizing lava since the mid-1980s. While products in the civil engineering field centered on keywords such as "natural plant growth" and "natural ecosystems" are no longer unique, the company has pioneered this market. Furthermore, the company is now poised to enter a new business phase under the vision of "Environmental Civil Engineering Renewa
l."

Product development inspired by the natural environment.

The company's first product, the "Naturock Porous Environmental Block"—a composite of concrete and lava rock—was first used in June 1985. The location was not a river, but the Sunazuri Slope at the sixth station of Mount Fuji.

"From 1980 to 1985, there was a series of rockfall accidents on the Mount Fuji hiking trails, and Yamanashi Prefecture was planning to proceed with retaining wall construction to prevent rockfalls while consulting with the then-Environment Agency and the Agency for Cultural Affairs. "However, while retaining walls made of conventional concrete blocks could prevent accidents, there was a risk they would mar the beautiful scenery of Mount Fuji. That's when I received an inquiry," recalls Toshiaki Sato, the inventor of Naturock and Managing Director of Japan Naturock. At the time, Mr. Sato was employed by Fuji Special Concrete Industries (Nishikatsura Town, Yamanashi Prefecture), a concrete products manufacturer where he remains an executive to this day.

The inquiry came in the spring of 1985. The construction had to be completed by July, when the mountain reopens to the public, and traditional stone masonry methods using materials like dry-laid stones would never have been fast enough. So, Mr. Sato proposed a method using materials that embedded lava from the foot of Mount Fuji into the surface of concrete blocks. About four years before this proposal came up, Mr. Sato had already been working on developing materials that embedded lava into concrete blocks and had successfully commercialized them.

"I was born and raised in Fujiyoshida City at the foot of Mount Fuji, and I always felt that the rivers around Mount Fuji, which were being lined with concrete every year, clashed with the surrounding landscape. That's why I was working on developing a new concrete product that would preserve the natural environment and beautiful scenery," says Sato, explaining the impetus behind the development of Naturock.

The idea of using lava was inspired by the Aokigahara Forest at the base of Mount Fuji. The fact that the area is covered in porous lava, which has excellent moisture absorption and retention properties, is a key factor in creating an environment where diverse flora, fauna, and microorganisms thrive. The greatest appeal of lava is not just its appearance, but its ability to create an environment conducive to plant growth.

A material shaped by the forces of nature.

Following the retaining wall construction at the sixth station of Mount Fuji, Naturock—made from natural stone quarried at the foot of the mountain—was adopted for retaining wall work along the Oshino Cycling Road on the shores of Lake Yamanaka in Yamanashi Prefecture. Although natural stone was used to address concerns about the strength of the lava, this decision expanded the range of Naturock products and laid the groundwork for its nationwide rollout. "While we do have a strong preference for lava, we realized that by using local stone that blends into the local landscape, we could popularize Naturock nationwide," says Mr. Sato.

However, since transporting concrete products over long distances incurs high shipping costs, it is common for local companies to supply concrete products specific to their region. The company's Naturock products were also limited to areas within Yamanashi Prefecture, such as the shores of Lake Motosu and Lake Kawaguchi. Therefore, in December 1987, the company established Nippon Naturock as an independent entity separate from Fuji Special Concrete, and simultaneously began recruiting concrete manufacturers and other partners for nationwide technical collaborations. Currently, the number of partner companies ranges from Hokkaido to Okinawa, totaling 20, and the company has also signed a contract with Miyakejima Village.

In 1994, the company moved its headquarters to Tokyo. With increased opportunities to meet directly with local government officials in charge of river projects, the number of installations in the Tokyo metropolitan area grew rapidly, not only for natural stone blocks but also for lava blocks.

NatuRock Environmental Blocks.

Two years after relocating to Tokyo, while walking around the city, he noticed the bleak riverbanks of the urban rivers flowing through the city. Renovating the vertical concrete retaining walls common in urban areas is difficult due to constraints on land space, the impact on residents during construction, and cost issues. This led to the development of "NatuRock Biopode," which has since become the company's flagship product. It consists of a concrete board approximately 2 cm thick with porous natural stones, such as lava, randomly embedded within it. The spaces between the stones are filled with sand and gravel to ensure the concrete surface does not remain exposed. By attaching this to a wall surface, it creates an environment conducive to the natural growth of moss and small gravel without the need to demolish existing riverbanks. The standard type (2 cm thick × 30 cm wide × 110 cm long) weighs 22 kg, making it relatively easy to transport. It can be used not onl
y for riverbanks but also for road retaining walls and pier walls. It represents a new concept of "covering" inorganic structures with natural materials.

[Strictly speaking, simply covering a riverbank does not immediately lead to the restoration of the ecosystem. I believe it would be more accurate to say that it provides a habitat where organisms can thrive even on vertical surfaces. Not limited to Pio Board, the fundamental concept of Naturock is that it is not a product that controls natural processes, but rather a material that is controlled by natural processes.]

A product line of "covering" solutions designed to improve urban environments.

Thanks to this product expansion, sales have grown from an initial 80 million yen to approximately 800 million yen. And the product developed by taking the "covering" theme even further is "Naturock Piofilm." This consists of an ultra-lightweight, ultra-thin special film, or a board substrate of about 5 mm embedded with a porous base material, and does not use concrete. It is even lighter than Pioboard, and the film-type version can cover curved surfaces. "I have been developing concrete-based composite materials for a long time, and I have a strong personal commitment to concrete products. However, if existing structures or concrete blocks already possess sufficient strength, there is no need to deliberately seek strength in the material used to cover the walls," says Sato, pointing to the "Hino no Furuayase No. 99" project (Wako City, Saitama Prefecture) one year after Pio-Port installation. From a business perspective, as long as concrete materials are used
, concrete manufacturers will always be competitors. However, with Biofilm, it becomes possible to supply not only the clients, developers, and general contractors—who have been the main customers for Naturock products to date—but also concrete product manufacturers. He reports that there are already inquiries from major concrete manufacturers.

In any case, Mr. Sato predicts that the concept of "covering" will have a significant impact on the civil engineering industry. "In urban spaces, it is often difficult to remove existing inorganic structures such as riverbanks, walls and fences along roads, and utility poles. Rather than that, I believe that 'environmental civil engineering renovation'—reforming the surfaces of these structures with porous materials and adding appropriate greenery—is a practical approach to improving urban landscapes and the environment."

Factors contributing to the company's growth include technologies that utilize natural materials and the development of a diverse product lineup tailored to specific locations. However, what truly sets the company apart is its firm commitment to a concrete vision—or philosophy—as a practical approach.