Aluminium is a vital, versatile metal. But while it’s easily recyclable, we need to produce more to meet global demand.
To make aluminium, bauxite is refined into alumina and then processed into aluminium. The alumina refining process produces a residue slurry, often called “red mud”, which plants can’t grow in when it’s untreated.
And there’s a lot of it. Globally, around 4 billion tonnes of red mud sit in ponds or dams, with more added every year.
Globally, around 4 billion tonnes of bauxite waste, known as 'red mud', sits in containment ponds or dams, with more added every year.
Usually, red mud is rehabilitated with traditional engineering methods like containment ponds and liners, topped with a metre or so of topsoil. These require careful maintenance to help plants establish in the shallow soil of the capping layer.
Rehabilitating red mud is a huge, ongoing challenge for the mining industry – one we’re still working on after decades of research.
But we’re making progress. Seawater is sometimes used to treat red mud before it’s stored, neutralising its alkalinity, but increasing its salinity. And we’ve been working to rehabilitate some remote sites like Mt Rosser in Jamaica, and Gove in the Northern Territory, Australia with a topsoil-free solution.
A new eco-engineering solution we’re working on with researchers from The University of Queensland (UQ) in Australia processes red mud into a soil-like material that can be replanted faster and with less impact on the environment than other methods.
And field trials have shown it’s possible to rehabilitate extremely alkaline or saline bauxite residues this way within 2–3 years.
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