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Inside Boliden’s deep repository for processed waste

Swedish metals mining, smelting and recycling major Boliden has been investing millions to innovate and ramp up its electronics recycling processes at the company’s plant in north-east Sweden. At the same time, it has also been busy digging a tunnel underneath the facility. Here’s why.  

This story begins 330 metres underground In a surreal place you’d rather not want to be any longer than necessary. It’s best compared to being in a stalactite cave. It’s a bit cold, humid, has a strange smell and is mostly pitch black. The only light comes from the pick-up truck that has carried us on a bumpy ride along a 3.5 km tunnel cut through solid rock.

‘Welcome to our deep repository,’ says Ulf Degerstedt, technology and business development manager at Boliden Rönnskär, a massive metal, smelting and recycling plant at Skelleftehamn, a peninsula on the Gulf of Bothnia east of Skelleftea.


Boliden’s deep facility is unique, says Degerstedt. ‘Nowhere else in the world will you find an underground repository on the same site as a smelter.’ The company’s decision to put all the waste processed from the smelter in the repository has been forced in part by environmental legislation. If waste from smelting and recycling contains more than 0.1% mercury it must be stored in a deep underground repository – similar to the treatment of nuclear waste. ‘We hired nuclear waste storage experts to learn from their know-how.’

Only a small part of Rönnskär’s waste contains mercury, explains Degerstedt. The bulk of the residue is comprised of other substances currently stored on the industrial site. ‘But these materials, too, will be transferred to the repository, along with those generated from the daily operations.’


Since there are precious metals in these residues, Boliden does its utmost to extract them first. The company has invested EUR 70 million in a leaching plant for certain materials. Leaching enables the recovery of more metal from the residue, simultaneously reducing the volume that will have to be stored in the repository. Degerstedt explains: ‘Leaching is in line with our strategy of turning as much as possible of our raw materials into products with as little waste as possible.’


The repository consists of eight storage chambers, located at the far end of the tunnel. Each is 18 metres high and up to 200 metres long. The scale is impressive. In the coming years, each chamber will be filled with waste material and then ‘safely sealed forever’. ‘In order to minimise the risk of leakage, a stabilisation plant has been built where certain waste materials are pre-treated before being placed in the repository,’ Degerstedt explains.

The first transport came through the tunnel in February 2022 and up to 30 truck loads can pass through it each day. Unsurprisingly, strict safety rules apply underground, says Boliden’s communications manager Ann Lundholm. ‘There are escape routes and safe houses with water and food for 72 hours should an accident or some other emergency situation happen.’

Read the full story in our Jan/Feb issue >>

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