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The world’s first next-generation bio-product mill developed in Äänekoski


Ääneköski bio-product mill


Metsä Fibre Oy

Project Developer

Sweco Industry Oy, Sweco Ympäristö Oy and Sweco Rakennetekniikka Oy


preliminary design, primary and implementation planning, process and plant design, structural design, project management and supervision, cost accounting and environmental impact assessment

Years from planning to execution



142,000 m² gross, 1.2 million cubic metres

Investment value

EUR 1.2 billion

Decent work and economic growth
Industry Innovation and infrastructure
Responsible consumption and production
Climate Action

Metsä Fibre’s, part of Metsä Group, bio-product mill in Äänekoski is the largest wood-processing plant in the northern hemisphere

Sweco was responsible for designing the bio-product mill.

Pulp has been produced in Äänekoski for over 80 years, and the location is ideal for the bio-product mill of Metsä Fibre, the construction of which began in 2017. Central Finland is bursting with raw wood material and the logistics are in order. The entire value chain of the mill has generated approximately 2,500 jobs in Finland, 1,500 of which are new jobs.

At best, more than 200 Sweco engineers across Finland worked on the EUR 1.2 billion project. The project’s degree of domestic origin was high – over 70 per cent. Sweco carried out the confidential preliminary evaluation phase in 2013. In 2014, Sweco conducted an environmental impact assessment.

“The environmental impact assessment included modelling the increase in traffic noise,” says Sweco’s Department Manager Leena Hannonen. “The bio-product mill operates within the emission limits set for the previous pulp mill in Äänekoski, even though the production capacity of the new mill is nearly three times higher.”

The mill was completed in good cooperation and on schedule

As the principal designer of the project, Sweco was responsible for the implementation planning of all the disciplines of engineering. “In addition to the processing units, we designed over 30 buildings and used approximately 15,000 concrete elements in this project. This shows you the scale of the commission,” explains Samu Ristolainen, Project Manager of Structural Engineering.

The design, construction and installation phases progressed simultaneously throughout the project. Sweco’s layout and mill planning included 3D modelling and an automation design system. “We also coordinated scheduling, reporting, procurement services and planning,” lists Visa Moilanen, Project Manager at Sweco.

According to Moilanen, all cooperation was characterised by a good team spirit and strong will to work together. “Together, we were able to complete the unique project on schedule and within budget.”

Optimisation of energy and water consumption

The bio-product mill produces annually approximately 1.3 million tonnes of pine and birch pulp for cardboard, soft tissue, greaseproof paper and speciality product production. In addition, the mill produces bioenergy and other bio-products, such as tall oil and turpentine. Sweco optimised the energy and water consumption of the production process together with the client and equipment suppliers.

“The mill’s self-sufficiency rate of electric power can reach up to 240 per cent,” says Sweco’s Bio-economy Expert Niko Ruokolainen. In fact, the mill increased the share of renewable energy in Finland by almost two percentage points, which supports Finland’s national renewable energy targets. The mill does not use any fossil fuels in its pulp production.

The other side streams of production are also utilised efficiently. The mill produces fossil-free producer gas from bark for its own use and processes stink gas into sulphuric acid, which is used as a processing agent in the mill. Sludge from the sewage treatment plant is used in the production of bio-pellets and, in the future, biogas. Any lime, ash or other side cuts generated by the production process can also be utilised in e.g. fertilisation and landscape development.

There is a corporate ecosystem around the bio-product mill of Ääneköski that utilises pulp and side cuts of production and uses them as raw materials in the production of a variety of bio-products. The bio-product mill allows the ecosystem to expand in the future. One of the recent additions to the area is the MI Demo pilot plant located right next to the bio-product mill. The pilot plant produces textile fibres from pulp. In addition, a 3D fibre pilot plant is currently under development in the area.

“The bio-product mill has definitely encouraged international businesses to invest in Finland,” says Sweco Industry’s Managing Director Erik Skogström. Skogström believes that the commercial potential of bio-economy is almost limitless. “Furthermore, shifting towards bio-products slows down climate change, reduces waste and prevents pollution.”

The bio-product mill does not use any fossil fuels in its pulp production.


Together, we were able complete the unique project on schedule and within budget.

The bio-product mill has encouraged international businesses to invest in Finland. The commercial potential of bio-economy is almost limitless.
– Erik Skogström, Sweco