Hydro’s state-of-the art press filter technology is one of the highlights in The International Aluminium Institute’s (IAI) new “Sustainable Bauxite Residue Management Guidance” for best-practice sustainable bauxite residue management.

The guidelines explore the life cycle of bauxite residue and show how stakeholders can play an active role in its sustainable management.

Sustainable management of bauxite residue

Bauxite is transported to Alunorte as a slurry via a 244-kilometer-long pipeline from Hydro’s Paragominas bauxite mine. The water used to make the slurry must be largely removed before the bauxite can be processed into alumina. 

The processing of bauxite into alumina creates bauxite residue, also known as ‘red mud,’ which needs to be stored in bauxite residue storage facilities. Hydro's alumina refinery, in the northern state of Pará, uses an enhanced dry-stacking concept for managing the bauxite residue.

The state-of-the art press filter technology, built in connection with the new bauxite residue deposit DRS2, results in a bauxite residue of about 78% solid content. This is done by pressing the residue through 74 plates with filtrating fabric membranes, resulting in a more compact residue, which in turn reduces the area needed for residue storage.  

The IAI guidelines document says, “This press filter technology produces a filtered cake with lower moisture content (22%), which allows for the cake’s further mechanical compaction and storage on steeper slopes, reducing storage area requirements and its environmental footprint.” 

This new approach means that, per tonne of alumina produced, bauxite residue now occupies only one-fourth of the surface area in DRS2 than it did in Alunorte’s historical bauxite residue deposit (DRS1). In 2021, global bauxite residue generated was estimated at almost 170 million tonnes.  

Watch video to learn more about the press filter technology:

Important part of Hydro’s environmental ambitions
Hydro's long-term aspiration for the rehabilitation work is to bring back as much of the original forest structure and biodiversity as feasible.

Hydro's press filter technology is therefore a crucial component in Hydro’s environmental commitments, as it greatly reduces the area needed to deposit the bauxite residue generated from alumina and aluminium production.  

“The DRS2 and press filters are the most sustainable bauxite residue deposit technology available in the world,” says John Thuestad, Executive Vice President of Hydro Bauxite & Alumina. 

Hydro has set an ambition to achieve no net loss of biodiversity in new projects across Hydro’s business areas, and longer-term ambitions to eliminate landfilling of recoverable waste and the need for permanent storage of bauxite residue.