Allocation as incentive or impediment for zinc recycling from hazardous waste

Linked Sessions:

Poster Number:  16 

Main Presenter:    Sabina Grund 

Co-Authors:   Eric van Genderen                                               

Zinc is a base metal. It is mined, produced, used, and recycled in many counties around the world. About 60% of the world’s primary and secondary zinc production is used to protect steel from corrosion (galvanizing), thus ensuring long-term durability of infrastructure like bridges, buildings, transmission towers, wind, and solar power generation. Prolonging the life of steel structures already saves valuable resources and avoids greenhouse gas emissions, it contributes to the principles of the circular economy and to the United Nations Sustainable Development goal “Responsible Consumption and Production” (12).
After a long service life, galvanized steel scrap is recycled in the steel industry. Remelted in electric arc furnaces (EAF), the steel becomes available as raw material again with a much lower carbon footprint than primary steel’s. In the EAF process, zinc evaporates, oxidizes, and leaves the furnace as so-called EAF dust. EAF dust is a hazardous waste with no use as such. It is either landfilled or enriched until the zinc concentration is increased from 15 – 30 % up to more than 50% in a product which depending on the enrichment technology used is called crude zinc oxide or Waelz oxide. This product easily replaces primary raw material from mined zinc ore. Current enrichment processes are pyrometallurgical techniques and require carbon as a reductant. Consequently, EAF dust has a higher carbon footprint than primary zinc ore concentrate. Innovative processes are under development but need time for refinement and upscaling. Despite the manyfold positive impacts of these secondary raw
materials in primary zinc production and on zinc circularity, zinc recycling from its main product is incentivised or at risk of being discouraged depending on the allocation of GHG emissions in steel recycling and EAF dust enrichment.
Using the example of primary zinc production with integrated zinc recycling from galvanized steel, the importance of a responsible choice of an allocation from the spectrum allowed in ISO and other norms is illustrated. Establishing clear and harmonized guidance for allocation methodologies is obvious but remains challenging at the same time.

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