Gerdau operates a steel mill in Whitby, Ontario, where recycled scrap metal is processed in an Electric Arc Furnace (EAF) to produce long steel products. As part of its integrated operations, the facility includes an onsite shredder that processes oversized scrap into three primary streams:
- Ferrous metal (melted in the EAF),
- Non-ferrous material (for external sales), and
- Shredder residue (non-recyclable waste).
The shredder residue is managed onsite in specially designed berms or cells on-site, in accordance with Environmental Compliance Approval (ECA) No. A390510 issued by the Ministry of the Environment, Conservation and Parks (MECP).
To mitigate environmental risks, these storage cells are constructed with:
- An engineered liner system consisting of a geosynthetic clay liner, overlain with a geomembrane
- A leachate collection system, using perforated pipes embedded in drainage aggregate, to direct leachate to pump stations and treatment ponds.
In 2013, the ECA was amended to allow the use of steel slag aggregate – a by-product of the steelmaking process – in place of conventional clear stone in the leachate collection system. This innovative approach:
- Enables beneficial reuse of EAF steel slag,
- Avoids use of virgin aggregate and their associated costs,
- Promotes the circular economy by linking steel production with by-product management practices onsite.
Since 2013, over 100,000 tonnes of EAF steel slag have been used in the construction of shredder residue cells at the Gerdau Whitby Mill, highlighting the company’s commitment to sustainable and resource-efficient operations.
Constructed shredder residue cell floor prior to placement of shredder residue with EAF Steel Slag used in both the drainage and protective layers of the leachate collection system
Shredder residue cell floor showing use of EAF steel slag (foreground); previously constructed storage cells containing shredder residue (background)