The icing on the cake

Stockholm’s Environmental Masterpiece

One of the world’s largest biomass projects has recently started up right in the center of Sweden’s capital, Stockholm, helping it on its way to become Europe’s most environmentally friendly city. ANDRITZ played a major role in creating Stockholm Exergi AB´s (former Fortum Värme) showcase Värtaverket biomass CHP plant.


“To get the capacity we needed, we had to install a very large boiler. That meant height as well as width when it came to capacity."

Senior Project Manager, KVV8

The locals call it the “Wedding Cake” due to its multi-tiered form sitting quietly and unobtrusively along the cityscape of Stockholm. While certainly impressive on the outside, this terracotta clad masterpiece of design also holds something truly remarkable within – one of the world’s largest biomass boilers, which, along with some of the most modern technology available, ranks it among the most productive and efficient facilities to be found anywhere today.

And this growing city certainly needs a large, efficient, and productive boiler; Scandinavia in the winter can be a very cold place and Stockholm’s 1.5 million residents need full on, 100% reliable district heating to enable them to live and work in the city.

The new plant is fueled entirely by biomass, which comes in chip form from all over Sweden and further around the Baltic region. Mats Strömberg, Senior Project Manager for the KVV8 project says, “Not only is this one of the largest biofuel projects in the world, but we have built it in a tight space, right in the heart of the city, with a lot of the main moving parts and supply systems situated way underground.”



Carefully built around three protected ancient oak trees, the uniquely impressive design of the boiler house at the Värtaverket site has recently been shortlisted in a global prestigious design awards.

© Riku Isohella


The Värtaverket KVV8 project has become a major milestone in the Stockholm Exergi AB - Stockholm city strategy of reduced emissions – the new facility has reduced CO2 emissions by an incredible 126,000 tonnes per year and 650,000 tonnes per year including the impact from the electrical production.

With a total investment of 500 MEUR, ANDRITZ was awarded the contract for the boiler and all automation at the plant in December 2012. Bernhard Haimel, Project Manager for ANDRITZ, explains, “We were delighted and proud to win this order; there was a lot of work involved in the quotation process. Our aim was to convince that we were the right supplier for the job.

“This was a unique project in many aspects, particularly the manufacture and installation of one of the world’s biggest boilers, with a biofuel fed Circulating Fluidized Bed (CFB) and an output of 345 MWth. What was particularly difficult in this case was that we had to fit the boiler into a limited space at the same time as apply the very best technology for efficiency, including the need for fuel feeding via six spouts to ensure even distribution of the biofuels, one of the prerequisites for the lowest possible flue gas emissions.”

And the icing on the cake? “The environmental data from this plant is very, very good,” says Strömberg. “The contract we made with ANDRITZ stated that the emissions need to be much lower than government regulations, and they have achieved this and more. The success of the Värtaverket KVV8 project means we are a big step on the way to creating a fossil fuel-free city.”


Much like catching and using the steam generated from a boiling kettle, the technology at the Värtaverket site has been designed for maximum output, and to use and reuse any steam, heat or power to achieve extra efficiency wherever possible.

© Riku Isohella

A hole was blasted out of the rock to a depth of 40 meters.

© Riku Isohella