In Finland, forest industry sites have traditionally been located along waterways. This is partly because proximity to waterways facilitated the transport of wood raw material. Even though waterways are relatively insignificant in terms of wood logistics today, water is still an important resource for the mills.
At the pulp mill, water is needed to wash the pulp, for sorting and as a medium to facilitate the transfer of pulp and chemicals. In addition, all departments need cooling water to handle the heat load created by the process.
Modern mills use far less water
“Until the 1970s, pulp mills consumed over 100 cubic metres of water per tonne of pulp produced. The design value for the Äänekoski bioproduct mill is 15 cubic metres and for the Kemi bioproduct mill just 10 cubic metres of raw water per tonne of pulp produced,” says Kari Ala-Kaila, Director, Technology at Metsä Fibre. The design value refers to the total amount of wastewater created when the mill produces the planned amount of bioproducts.
Metsä Fibre’s water use is below the lower limit of the Best Available Technique (BAT), and the aim is to reduce it even further. One of the company’s sustainability goals is to reduce the amount of process water used per tonne of pulp produced by 35 per cent by 2030, compared to the 2018 level.
Process water is recycled several times
We aim at closed water circulation where water is recycled and reused. This reduces the need for new water and overall water consumption.
Most of the pulp mill’s washing water comes from the drying department or evaporation plant. The secondary concentrate and the filtrates from pulp washing are reused multiple times. The pulp mill’s washers operate on a countercurrent principle, which reduces the need for fresh water even further.
High utilisation reduces the need for water
Steady running of production plants is important when you want to use water more efficiently. Incorrect equipment settings or potential hardware failures lead to losses, so both the settings and the condition of equipment are monitored regularly. Planned preventive maintenance and shutdowns support good water utilisation.
Each Metsä Fibre pulp and bioproduct mill has a concrete goal for reducing water use that takes into account the mill’s age and other unique characteristics. Mill-specific solutions and good practices are compared and shared between production sites.
New solutions enhance process water recycling
The modern technology at Metsä Fibre’s production plants enables water to be purified and recycled more efficiently. For example, water consumption in bleaching has been reduced thanks to more efficient washers.
Reducing water use also requires training personnel and establishing correct operating methods for the mills. “The operators decide how much water is used in each phase of the process, so it’s important that they understand how their choices impact the overall outcome,” says Ala-Kaila.
Water usage is being optimised at every mill
Metsä Fibre aims to reduce water consumption at all its mills.
The Rauma pulp mill uses the filtrates from bleaching in consistency controls instead of fresh water. Additionally, the fresh water has been replaced with circulated water at the debarking process. These measures have reduced wastewater by 3–4 cubic metres per tonne of produced pulp.
At the Äänekoski bioproduct mill, secondary conden- sate is used instead of raw water in wood processing, and clean hot water in bleaching has been replaced with secondary condensate and recycled water from the drying department. Wastewater has been reduced by 3–4 cubic metres per tonne of produced pulp.
At the Joutseno pulp mill, the use of raw water has been reduced by closing water circulations in, for example, bleaching, screening, and debarking. This has decreased the amount of wastewater by 6–8 cubic metres per tonne of produced pulp.
The Kemi bioproduct mill has been designed to be particularly efficient with respect to water usage. In terms of water consumption, the Kemi bioproduct mill is the lowest among Metsä Fibre’s mills.
Read more about the ways we reduce our water usage.
This article was originally published in Fibre Magazine issue 2025.