Hydro has invested around $5.5 million (R$ 30 million) in the testing stage of the methodology that allows for the final disposal of tailings in areas already mined, and has received an operating license from SEMAS, The Pará State Secretariat for the Environment and Sustainability.
"Hydro is committed to driving sustainability in the aluminum industry. This challenge has driven our efforts to pursue practices that can eliminate the need for new permanent tailings storage dams in bauxite mining," says John Thuestad, Hydro's Executive Vice President for the Bauxite & Alumina business.
Hydro's project is a pioneer in the sector and has been in testing since July 2019 at the Mineração Paragominas bauxite mine in the northern state of Pará.
The methodology eliminates the need for continuous construction of new permanent tailings dams, or even the need to add layers to existing structures, by applying the methodology known as "Tailings Dry Backfill," which deposits inert dry tailings in areas already mined.
This stage of testing is being carried out with permanent monitoring and follow-up by environmental agencies and following the technical standards of Conama, the National Environmental Council.
The application of this methodology in Brazil is an important step in terms of sustainability in the industry, increasing operational safety and significantly advancing work to reduce Hydro's environmental footprint.
The testing was completed in late 2020 and the project received operational licensing approval from SEMAS, The Pará State Secretariat for the Environment and Sustainability on December 30, 2020.
About Tailings Dry Backfill
The Tailings Dry Backfill technology allows inert tailings from bauxite mining to be returned to the already open and mined areas, preceding the rehabilitation process, instead of being deposited in separate, permanent storage areas.
After drying in temporary storage for 60 days, the bauxite tailings are put back into the mined areas, which are later rehabilitated and reforested. This will further reduce the environmental footprint of bauxite mining and increase operational safety. The tailings from bauxite mining are chemically and physically similar to what was removed during the mining process. Therefore, it is returned to nature without any impact to the environment.
Before testing the method in Paragominas, Hydro carried out technical studies and detailed planning. In July 2019, after obtaining authorization from the environmental agency, Hydro began the field-testing phase. The tests have been carried out in different seasons, continuously monitored by the project's technical team and detailed reports are regularly forwarded to the environmental authorities. After one year of testing, the results are generating positive results in relation to the environment, operational safety and within forecast costs.
Rehabilitation of mined areas
Mineração Paragominas is committed to applying the best environmental practices and continuously invests in the rehabilitation of mined areas. In the recovery of these areas, the original form of the soil is reproduced, with the addition of organic matter. Then, the land is prepared to receive the seedlings that will restore the vegetation coverage.
Since the reforestation program was initiated in 2009, Mineração Paragominas has already accounted for an area of 2,300 hectares in the recovery process. On average, 200,000 seedlings of native species are produced per year in the Mineração Paragominas nursery.
To improve the rehabilitation process, Hydro is part of the Brazil-Norway Biodiversity Research Consortium (BRC), which brings together researchers from the Federal University of Pará (UFPA), the Federal Rural University of the Amazon (UFRA), the Emílio Goeldi Museum, the University of Oslo (UiO) and Hydro professionals in Brazil, seeking the best alternatives for reforestation and monitoring of mined areas.
Current dam systems at Mineração Paragominas
Mineração Paragominas has two dam systems for bauxite waste storage. Both systems use a tailings disposal methodology based on the alternate operation of their reservoirs, allowing the tailings to dry out in each reservoir by combining drainage and evaporation, which results in tailings with a minimum solid content of 60%.