Page 20 from: Recycling International January/February issue 2023

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RECYCLING TO THE MAX
Since there are precious metals in
these residues, Boliden does its
utmost to extract them first. The com-
pany has invested EUR 70 million in a
leaching plant for certain materials.
Leaching enables the recovery of
more metal from the residue, simulta-
neously 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.’

SAFETY FIRST
The repository consists of eight stor-
age chambers, located at the far end
of the tunnel. Each is 18 metres high
and up to 240 metres long. The scale
is impressive. In the coming years,
each chamber will be filled with waste
material and then ‘safely sealed forev-
er’. ‘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.

TWO MILLION MOBILE PHONES
Integrated into its Rönnskär smelting plant at Skelleftehamn is Boliden’s e-scrap processing
facility with the capacity to handle 120 000 tonnes of electronics per year, equivalent to more
than two million mobiles phones per day. Typically, some 90 000 tonnes of e-scrap, predomi-
nantly circuit boards, are processed each year.
Boliden’s recycling process is based on so-called Kaldo technology which was introduced ini-
tially into the steel industry in the 1940s and has since been further developed by Boliden for
smelting e-scrap.
The Kaldo furnace is described as ‘a slightly leaning cylinder’ which rotates during the smelt-
ing process. Material is fed in and tapped out through the mouth of the furnace. In total
some 25% of the copper, 30% of the gold, 25% of the silver and 80% of the zinc produced at
Rönnskär comes from recycled material.
The facility minimises its emissions and generates district heating from this electronic materi-
al.
Before the e-scrap arrives at Rönnskär by train or truck from southern Sweden, it is disman-
tled with much of the plastic, iron and aluminium removed. A large amount of mobile phones
is supplied by Kuusakoski Recycling Sweden – their story is on the next two pages.

This story begins 330 metres under-
ground in a surreal place you’d rather
not want to be any longer than neces-
sary. 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.

DRIVEN BY LEGISLATION
Boliden’s deep facility is unique, says
Degerstedt. ‘Nowhere else in the
world will you find a deep under-
ground 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 legis-
lation. 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 cur-
rently stored on the industrial site.
‘But these materials, too, will be trans-
ferred to the repository, along with
those generated from the daily opera-
tions.’ Ulf Degerstedt.

A U T H O R Martijn Reintjes

Inside Boliden’s deep repository for processed waste

‘Safely sealed forever’
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.

Boliden cut a 3.5 km long tunnel through solid rock.

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