Alcoa of Australia Residue Management
 
Overview

Residue, or tailings, remains after the component of value is extracted from an ore body in minerals processing.  As every six tonnes of bauxite makes two tonnes of alumina, and every two tonnes of alumina makes one tonne of aluminium, there is a significant generation of residue in the process of converting bauxite ore into aluminium metal. 
 
Alcoa of Australia’s residue is made up of two components of roughly equal quantity – sand and mud. Much of the sand is reused for construction of and within the residue drying areas (often called residue storage areas). The residue mud is dried in layers within our storage areas. As it dries, more mud is laid on top to form a residue stack.

Residue drying areas are ‘fields’ of what looks like mud or clay. The mud is generally not visible outside Alcoa’s operations because it’s contained within engineered embankments.  Alcoa rehabilitates the embankments which are visible to the community, and in some cases it can take many years to form an effective visual screen.

In Western Australia the low grade of the bauxite ore, compared with bauxite from other locations around the world, makes sustainable residue management an even bigger challenge here. The lower the alumina content in the ore, the larger the amount of residue produced.
 
The main challenges for Alcoa of Australia around our residue drying areas are:
 
• The size of our storage areas
• Their location in relation to neighbours
• Dust
• Visual amenity
• Community perceptions and community access to factual information about residue.
 
Alcoa of Australia has found ways that our by-products can be useful to the community.  Alcoa’s global refining research and development group, based at Kwinana in Western Australia, has designed a 'Carbon Capture' process whereby bauxite residue can be treated with waste carbon dioxide (which also locks up carbon emissions that would otherwise be released into the atmosphere).  This process neutralises the alkalinity of the residue which has opened the door for residue reuse external to Alcoa’s operations.  Research spanning over 20 years has identified a number of bauxite residue by-products. Read more.  
 
The potential for dust to be generated from the surface of the residue storage areas as they dry poses another significant challenge, and Alcoa of Australia goes beyond our environmental licence conditions in relation to dust management. Our primary form of dust control is via a comprehensive network of sprinklers over the storage areas, which keeps the surfaces moist to prevent the wind picking up fine dust particles.  Read more about our many other dust control measures.
 
Finally, there are a number of misconceptions about residue within the community which present challenges for Alcoa of Australia and highlight the importance of us making available factual information about our residue operations.  One of these misconceptions is that bauxite residue contains dangerous levels of radioactive elements. This is not true - residue does not contain levels of radioactive material that provide any cause for health concerns. Read more. 

Click through the links to the left to find out more about all of the above.


Media Statement: 7 October 2010


Alcoa’s WA Refinery Residue Areas Safe
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