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ArcelorMittal's converter slag for the offshore wind and marine renewable energy sector

From 5 to 7 June 2019, By-Products Sales (part of ArcelorMittal European Purchasing Organization) participated to Seanergy, the international forum dedicated to Offshore Wind and Marine Renewable Energy. They presented the advantages of using converter slag (a by-product of steel making) to create the ballasts used to stabilise gravity-based foundations or floating windmills and its positive impact on sea life expansion.

The different usages of slag for marine applications

Converter slag, a by-product of steel making can be used for different types of applications:

Floating structure stabilisation

Converter slag can be used to reinforce the anchors of floating structures, such as floating windmills, wave energy production systems, etc.

Ballasts for gravity-based foundations in offshore wind farms

Thanks to its density, slag is also an excellent ballast material for structures built in the sea, such as gravity-based foundations used to support tube and wind turbines.

Scour protection

To avoid accelerated erosion in the area around structures (e.g. gravity-based foundations and piles), slag can be used to protect the area and to create scour protection.

Ecological mooring

Anchoring and mooring can progressively damage seabed. Ecological mooring (or eco-mooring) has been developed to prevent this phenomenon with anchors made of mesh boxes and filled with converter slag. This type of anchors prevents the destruction of the ecosystem, contributes to ecological restoration and to marine habitats protection.

Cable stabilisation

Converter slag can be packaged in steel boxes or steel bags to stabilise the cables used for the electricity, internet and phone networks.

This method brings several advantages:

  • it allows maintenance and facilitates a rapid intervention on the cables if necessary
  • the boxes can be filled in the steelworks area and directly loaded on vessels in the port area
  • slag ballast is compatible with electricity transmission

Impact on marine habitats

Already used in agriculture, slag is being studied to evaluate its impact on marine flora and fauna. The first ecological evaluation in France is led by ArcelorMittal in partnership with ECOCEAN. Slag provides interesting components to boost the marine flora and fauna, to renew ecosystems and to multiply fish hatcheries.

The aim of this evaluation is to:

  • Study the technical feasibility of this solution
  • Demonstrate its ecological efficiency
  • Get the approval of French authorities to deploy the solution

During this evaluation, several criteria will be closely monitored:

  • Water quality
  • Flora and fauna survey
  • Census of juvenile fish

The project has been presented by ECOCEAN to the Occitanie Region and has been validated. It will start beginning of 2021 and will last 2 years. Its results will be shared with several authorities in charge of sea protection.

Webpage of ECOCEAN

Advantages of slag ballast

The use of slag as ballast material has a positive impact on the development of marine renewable energies and offshore projects.

Many advantages arise from this innovative solution:

  • Value-driving solution for the local economy
  • Additional innovative activity for seaports
  • Creation of new solutions boosting biodiversity
  • Application of the circular economy in local projects: 100% of the ballast is processed with recycled material and reusable at 100% at the end of life of the offshore project (land use)
  • Ballast free of CO2
  • No natural stones extraction from quarries
  • Ecological mooring
  • Attractive sales price