Press ReleasesNippon Paper Industries develops an environmentally friendly new offshore engineering material by using marine sediments and paper sludge ashRestoring tidal flat environments through effective reuse of waste

Nippon Paper Industries Co., Ltd.

Nippon Paper Industries Co., Ltd. (President: Yoshio Haga) is pleased to announce that it has succeeded in developing a new offshore engineering material jointly with Kumamoto University and Fukuoka Construction K.K. The new material is made by granulating mix of dredged marine sediments and paper sludge ash1). An experiment conducted near the Kumamoto Port demonstrated that biodiversity of a tidal flat was restored when this new material was used for seawall. The Company will continue to work on this new offshore engineering material with the aim of finding commercial application.

Shortage of disposal sites of dredged marine sediments has been a problem, while the accumulation of sludge in enclosed coastal seas is emerging as an environmental issue.

Dredging works are being undertaken at ports and harbors in Japan for widening and deepening waterways. The work is conducted as a response to the increasing size of ships and demand for more advanced port functions, as well as needs for maintaining existing port functions. For these reasons, the works will continue in the future. Dredging works generate as much as 20 million cubic meters of dredged marine sediments every year. Because dredged marine sediments is soft, viscous soil in many cases, it is disposed of by using it to reclaimed land from the sea. However, a shortage of disposal sites has been a problem and effective use of dredged marine sediments has become an urgent issue. On the other hand, enclosed coastal areas such as inland seas and inner bays are facing biotic changes, declining marine life diversity and population under specific environments, and other significant issues. These problems are caused by reduced natural purification capabilities linked to an increase in artificial coastlines and tidal flat landfill, for example. They are also caused by worsening (conversion to sludge) of bottom sediment environment, which has taken place because marine sediment accumulated over many years has turned into soil or has been in an anaerobic state.

Success in developing a new material by making use of the property of paper sludge ash generated from paper mills. Restoration of biodiversity confirmed in an experiment at Kumamoto Port.

We focused on the property of paper sludge ash from paper mills, which is highly absorbent and consolidates in reaction with water, and developed the new material jointly with Fukuoka Construction K.K. by mixing and granulating paper sludge ash from our Yatsushiro Mill with dredged marine sediments, which features high moisture content. We also used this new material for the Ecosystem terrace revetment 2) to recovery of tidal flats and shoreline3) - a project undertaken by a research group from Center for Marine Environment Studies of Kumamoto University and led by Professor Kiyoshi Takikawa. Use of the material resulted in a large number of young shells of Japanese littleneck and other marine creatures, proving that use of the new material helps restore biodiversity. The new material brings two benefits. The first is that waste such as dredged marine sediments and soil accumulated in the sea floor can be utilized. The second is that tidal flat beaches (places of biodiversity) can be restored.

We will continue developing applications for the new material so that it can be used not only for restoring the tidal flat environment but as a versatile offshore engineering material with a wide variety of purposes such as Sand Compaction Pile (SCP) method4).

  1. *1Paper sludge generated in paper milling processes is burned in a boiler to collect the heat as biomass energy. The remaining ash is called paper sludge ash. It is normally used as a material for cement.
  2. *2A revetment developed by Kumamoto University in consideration of marine environments and hydrophilic functions, as well as the disaster prevention capability of the dike.
  3. *3The boundary between the land and sea, which is submerged at high tide.
  4. *4A method in which sand piles are constructed in the ground to stabilize soft ground