Creation of Sea Forests

In recent years, a new environmental problem that has been identified is sea desertification, meaning that the sea becomes like a desert owing to disappearance of seaweed from the water. The environment for growth of marine life deteriorates when this happens, causing serious damage to coastal fisheries. It was found that a decline of iron, which has been carried from the forest areas to the sea in river water, is one of the causes for sea desertification. To offset a part of the decline in the supply of iron from nature, Nippon Steel has created iron supply units composed of humus, soil and steel slag, the latter being a by-product of the steelmaking process that is rich in iron. Nippon Steel is supplying this product and promoting regeneration of seaweed beds.

Blue Carbon 360°VR video

See the VR video that you can experience the UMIMORI project, which improves the coastal environment by use of steel slag products.

Message from Innovators

Development of “iron” supply unit to prevent ocean desertification

Nippon Steel promotes the “creation of marine forest” to counteract the “rocky-shore denudation,” which has been a nation-wide environmental concern in recent years.

One of the causes of the “rocky-shore” phenomenon is the decreased supply of iron hich is necessary for kelp and seaweed to grow hrough rivers as a result of deforestation and upstream development. To cope with this problem, in 2004, we developed an iron supply unit containing humic substances made of iron/ steel slag and waste wood. Since then, we have been working on creating a seaweed bed (marine forest).

Nippon Steel also opened a “Sea Laboratory” (marine environment simulator) at the Technical Development Bureau in Futtsu City, Chiba Prefecture. We are working to scientifically clarify the usefulness and safety of using steel slag to create marine forest.

Chika Kosugi Sea Laboratory (marine environment simulator)

Sea Laboratory
(marine environment simulator)

Present marine water environment

Present marine water environment

* Sea desertification: With a decline in kelp, brown seaweed, and other varieties of seaweed, the sea bed loses ability to support life.

Initiatives to improve the marine water environment by use of steel slag products

Forming iron supply units composed of steel slag with soil and humus obtained by fermenting chips of waste wood; placement on the sea floor enables artificial supply of iron.

Initiatives to improve the marine water environment by use of steel slag products

Six months after installing iron supply units, kelp grew nicely 30- meters from where the units were placed. After two years and again after three years, it was confirmed that the positive effects had continued. (Mashike Town, Hokkaido)

Test of installing converter slag reef blocks

At the Wakayama Steel Works, Nippon Steel is carrying out a test using converter slag reef blocks in a reef habitat for fish. In October 2008, 12 converter slag reef blocks (each weighing 7 tons) were sunk in the coastal area of Shimizu-ura, Kainan City in Wakayama Prefecture (Kainan City Fisheries Cooperative). Since then, we have been observing the changes in the distribution of marine life, attached sea creatures, fish, and shellfish.

The results of observations made in April 2010 showed that the converter slag reef blocks tended to have more types and quantity of seaweed and attached sea creatures than the crushed stone blocks that were used for comparison. We will continue to monitor the changes, and verify the superiority of converter slag reef blocks for use in reefs for fish habitats.

The types of sealife observed were the following.

  • Plant life:Brown seaweed, Sargassum .licinum, Hydroclathrus clathratus, Champia parvula, etc.
  • Adhering sea creatures: Sea slug, oyster, sea cucumber, common sea squirt, etc.
  • Fish and shellfish: Sea pineapple, marbled rockfish, Japanese black porgy, horse mackerel, etc.

The results of these observations have been reported to and highly evaluated by the Kainan City Fisheries Cooperative, Wakayama Prefecture Fisheries Promotion Division, and Kainan City Industry Promotion Division.

Monitoring changes

Monitoring changes

Converter slag reef blocks

Converter slag reef blocks

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