Insufficient freeboard prompted production embargo
On February 24, 2018, the environmental agency in the state of Pará (SEMAS – the Secretariat of Environment and Sustainability of Pará) notified Alunorte to comply within 48 hours with the 1-meter required freeboard in the containment basins for rainwater that is drained from the bauxite residue deposits.
Alunorte is to have a 1-metre distance between the top of the water containment basin and the water level as a safety precaution. When Alunorte did not meet SEMAS deadline for the required freeboard by February 26, SEMAS demanded that Alunorte reduce production at the refinery by 50%. Alunorte managed to restore the required freeboard on February 27.
Embargo against use of new bauxite residue deposit (DRS2)
Alunorte has two bauxite residue deposit areas – the current DRS1 and the new DRS2.
DRS1 is approaching its end of life, and studies and tests on how to best rehabilitate the deposit have started. The area will be covered with soil and replanted with local plant species. DRS1 makes use of a technology called drum filters to handle the bauxite residue.
In 2014, Alunorte made a 1 billion BRL investment decision to build a new state of the art bauxite residue deposit area, DRS2, which makes use of an industry-leading technology for handling bauxite residue. This method of disposal is the industry Best Available Technology.
- An enhanced dry-stacking concept makes it possible to store four to five times more residue in a given disposal area.
- The residue can be stacked at a steeper slope, at around 20 degrees.
- Press filters can reduce the residue moisture content to 22%, down from 36% achieved with the drum filters technology.
The use of press filters lowers the environmental footprint, improves the geotechnical safety of the deposit, reduces the amount of caustic associated with the residue, and reduces the amount of CO2 emissions due to the transportation of the residue.
Alunorte’s plan was to start using the press filters for the commissioning phase of DRS2 and to scale down the use of drum filters for DRS1.However, this plan was put on hold in February 2018 when the regional court in Pará issued a ruling that Alunorte should halt the use of DRS2, and that a new license could not be issued until the integrity of DRS2 had been fully verified.
IBAMA, the federal environmental agency, also put in place an embargo in March on the use of DRS2, but lifted this embargo on October 25. By the end of October 2018, both IBAMA and SEMAS, the environmental authority in the state of Para, granted Alunorte permission to use the press filters for the residue for DRS1.
The embargo from the federal court on the use of DRS2 is now lifted. The embargoes were lifted in September 2019, ending a 19-month embargo period restricting activities at the plant.