Safe and sound underground

Watch our film about the unique underground repository at Boliden Rönnskär

The underground repository is unique. Nowhere else in the world is there an underground repository on the same site as a smelter. With our values as a basis, Boliden made the decision to place all process waste from the smelter in the repository. The installation will begin operation during 2021.

Environmental legislation focuses on mercury; if waste contains more than 0.1%, it must be stored in a deep underground repository. However, only a small part of Rönnskär's waste contains mercury – instead the majority is comprised of residues containing other substances, which is currently stored on the industrial site. Even these will be transferred to the repository, along with those generated from the daily operations.

Recovering metals from residues
Since there are precious metals in the residues – surely it would be wasteful not to try to extract them first? Boliden has therefore decided to invest MSEK 750 in a leaching plant for certain residual materials. Leaching enables the recovery of more metal from residues, simultaneously reducing the amount that will need to be stored in the repository. Leaching is in addition in line with Boliden's strategy of turning as much as possible of its raw materials into products with as little waste as possible.

Meanwhile, work on the underground repository continues. A ramp down to the repository level is complete as well as a connection ramp. In the repository eight caverns are being formed. During fall 2021 a stabilization plant will be erected, where certain waste will be pre-treated before placed in the repository. Stabilisation will minimize the risk of leakage.

The underground repository is a long-term sustainable solution for managing Rönnskär's residual process waste. When a rock cavern is full, it will be sealed forever.

Watch the animation of the deep underground repository.