Metsä Fibre works continuously for the environment

Environmental impact monitoring is an important part of the activities of Metsä Fibre’s mills. Work is carried out in close cooperation with expert companies and authorities.
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  • Sustainability, 2023

The water swirls brightly around the stones as Antti Leppänen, a fish biologist, steps into the waves of Kapeenkoski rapids in Central Finland, bordering the municipalities of Äänekoski and Laukaa. He is wearing fishing waders and carrying a device resembling a large rucksack, which is used to create an electric field in the water. The electricity briefly stuns fish swimming nearby so that they can be weighed and measured before being released back.

The fish are caught as part of monitoring carried out by Leppänen’s employer, KVVY Tutkimus Oy, in cooperation with Metsä Fibre, along the Äänekoski–Vaajakoski waterway.

“In addition to test fishing operations, we interview holders of fishing permits, determine the contaminant concentrations in fish and study changes in pelagic fish using sonar detection. By combining several methods, we aim to form as accurate a picture as possible of the condition of fish along the waterway,” Leppänen explains.


First pulp mill began operations in the area in 1938

Upstream from Kapeenkoski rapids is a longish flow-through lake called Kuhnamo. This area around Äänekoski, which links Kuhnamo and Keitele, is where the forest industry began to develop in 1896. A sawmill, groundwood mill and paperboard mill were built first. The first pulp mill began operations in 1938.

The mill brought prosperity to the region, but its environmental impacts were intolerable by modern standards. The waste liquor produced in the digester was released untreated straight into the waterway below.

When waterway impacts began to be surveyed along the Äänekoski–Vaajakoski route in 1975, the waters were found to be in a disastrous condition.

“Quite frankly, the rapids were like sewers back then,” says Leppänen.

The stink from the waterway was such that people crossing Kuusaa bridge used to roll up their car windows. The fish population also suffered. From the mid-1950s, trout caught in the Kuusaankoski rapids tasted of the pulp mill’s wastewater, and sports fishing in the rapids had to be discontinued.

Rising environmental awareness in the 1980s

Wood trucks carry a steady stream of logs to the Äänekoski mill area, covering nearly 200 hectares. At the centre of the industrial ecosystem rises Metsä Fibre’s bioproduct mill, with an annual capacity of 1.3 million tonnes of softwood and birch pulp. The mill is also producing many other bioproducts, such as biochemicals and bioenergy.

Although the scale of industrial operations has multiplied since the 1930s, the times when you had to hold your nose crossing Kuusaa bridge are long gone. Nowadays, Kuusaankoski rapids are a popular recreational spot and one of the few breeding sites for the endangered brown trout.

Anna Riikka Nickull, Metsä Group’s Environmental Manager, says the turn for the better happened in the early 1980s, when Metsä-Botnia, now known as Metsä Fibre, decided to build a new and larger pulp mill in Äänekoski.

“The Supreme Administrative Court set unprecedentedly tight emissions limits for the pulp mill. An activated sludge plant was built for the mill, and it contributed to rapidly cleaning the wastewater.”

In the 40 years since, technology has progressed by leaps and bounds. The current bioproduct mill operates within the same wastewater permit limits, despite production volumes that are nearly three times greater.


Results are reported to environmental authorities

The wastewater is sent to a multistage biological wastewater treatment plant with an aeration basin, where microbes break down its oxygen-consuming matter into carbon dioxide and water. If required, a final chemical treatment can be included in the tertiary phase. The biosludge is pressed into biopellets suitable for use as fuel, for example for industrial heating boilers. The sludge is also made into biogas for vehicle fuel.

“The mill conducts numerous analyses of the wastewater and the treatment plant to monitor their use and load. Some of the samples are analysed by an outside laboratory.”

Metsä Fibre reports the results to the environmental authorities. When the bioproduct mill was started up, monitoring of the downstream waterway was increased. Separate surveys are conducted to determine the impacts on the thickness of ice and movement of migratory fish.

The mill conducts numerous analyses of wastewater and the treatment plant to monitor use and load.

Thousands of waterway analyses annually

Metsä Fibre’s Joutseno pulp mill is in Lappeenranta on the shores of Lake Saimaa. The mill has an annual capacity of 690,000 tonnes of softwood pulp, used as raw material for various paper and paperboard grades.

In Joutseno, Metsä Fibre has been cooperating with Saimaan Vesi- ja Ympäristötutkimus Oy, a research provider, since the 1980s.

“We analyse Metsä Fibre’s wastewater, groundwater and other waters that end up in waterbodies in their production areas. We also handle updates to the monitoring programmes in cooper¬ation with Metsä Fibre and the authorities,” says Mikael Kraft, a limnologist at Saimaan Vesi- ja Ympäristötutkimus.

The waters of the southern end of Lake Saimaa are monitored by Metsä Fibre and seven other parties. Water samples are taken eight times a year, and the number of analyses based on them runs into the thousands.

The quality of water in Joutseno has remained stable since the introduction of biological treatment plants. Since the volume and quality of wastewater have a direct impact on the quality of water and the living organisms in Lake Saimaa, they also contribute to the quality of water.

“The measures adopted in wastewater treatment have been the right kind. This does not rule out additional investments that could improve the situation further,” says Kraft.

It is important for us to remain clearly below the permit limits.

Air quality index available to all

A modest-looking measurement booth stands by Äänekoski bioproduct mill, its probes sticking out into the sky like antennae. They collect data on emissions, which are monitored daily at the mill and regularly reported to the environmental authorities. The Finnish Meteorological Institute oversees air quality monitoring.

The devices inside the booth continuously collect data on the particulate concentration, sulphur dioxide, nitrogen oxides and total reduced sulphur (TRS) in the atmosphere. The mill’s environmental permit sets limits on all of them. The weather station in the building helps determine the source of concentrations observed by the measuring devices.

“Nitrogen oxides also originate from traffic, which is typically the main source in urban settings, whereas TRS and sulphur dioxide are usually of industrial origin,” says Mika Vestenius, Research Scientist at the Meteorological Institute.

The data is public, meaning that anyone can go to the Institute’s website and follow the air quality index calculated from the measurements and results.

At Äänekoski bioproduct mill, the recovery boiler plays a key role in the management of air emissions. An appropriately dimensioned air system supports efficient combustion and the management of nitrogen oxides. Particulate emissions have been curbed with effective electrostatic filters, and sulphur emissions have been minimised with appropriate fuel choices.

No fossil fuels are used in the bioproduct mill’s processes. Instead, all the energy needed is produced from the side streams of wood processing. The sulphuric acid plant represents new technology. It collects and treats the TRS generated in the process, converting it into sulphuric acid for the mill’s own needs.

“By closing chemical cycles, we have successfully minimised the emissions from operations and reduced the volume of chemicals transported from outside the mill,” says Nickull.

“The permit conditions determine the upper limit of loads that the environment can cope with without being adversely impacted. It is important for us to remain clearly below the permit limits.”

Anyone can follow the air quality index calculated from the measurements and results.

All employees conduct proactive environmental work

Tiia Finér, Development Manager at Joutseno pulp mill, logs into the system that the mill’s employees use to record environmental observations, potential risks and deviations posing an environmental risk.

“A chemicals container in a risky location is an example of such an environmental observation. The observation enables us to react before any accident occurs,” says Finér.

The system records not only deviations but also positive environmental observations. Tried and tested practices can be of use to other mills.

Making observations about the environment is part of every employee’s tasks. Mill employees compare observations, in their morning meetings for example, and if necessary decide who will follow up the matter.

“The system motivates our employees to observe their environment and pay attention to environmental matters.”

Regular training for employees ensures that environmental matters remain part of daily routines.

Proactive environmental and safety work includes rescue plans. Everyone must know how to act if something unexpected happens. The mills organise regular emergency drills in cooperation with the local authorities, rescue services and other key stakeholders.

Environmental matters ever more significant

In Finland, the forest industry’s long-term environmental work has resulted in considerable emissions reductions despite higher production.

According to the Finnish Forest Industries Federation, the pulp and paper industry has reduced wastewater emissions by 50 per cent, fossil CO2 by 71 per cent, particulates by 87 per cent and TRS by 97 per cent in proportion to production compared with 1990 levels.

Sustainability and responsibility are an integral part of all Metsä Group’s operations, and its strategic 2030 sustainability objectives are paving the way towards a climate neutral society. The company’s sustainability goals include fossil-free mills by 2030. By 2030 it aims to reduce the volume of spent process water by a quarter per tonne compared with 2018.

Nickull has been following developments in the field for 25 years. She believes that environmental efficiency will be increasingly important in the future.

“Environmental requirements have increased. This can be seen most clearly in the EU’s ongoing legislative initiatives, which also influence national legislation and permit processes. Sustainability is becoming more crucial than ever.”

This article was originally published in Fibre Magazine issue 2022–2023.

Watch video

Watch Anna Riikka Nickull’s video interview


Biofuels account for 97 per cent of the fuels used in Metsä Fibre’s production. The goal is for all mills to be 100 percent fossil-free by 2030.


Metsä Fibre uses 85 per cent of the solid production side streams as bioenergy or products. The goal is to make 100 per cent use of side streams by 2030.

25 m3/t

Metsä Fibre’s use of process water is already below the BAT (Best Available Technique) lower limit of 25 cubic metres per tonne.

In this article


Antti Leppänen
A fish biologist, who works at KVVY Tutkimus Oy, a provider of laboratory, research, design and expert services. He carries out fishery observations along the Äänekoski–Vaajakoski waterway.


Anna Riikka Nickull
Environmental Manager, Metsä Group’s technology department, environmental team. Responsible for official procedures at Metsä Fibre’s production units and support for environmental management.


Mikael Kraft
Limnologist and waterway expert at Saimaan Vesi- ja Ympäristötutkimus Oy. His duties include water system, fish fauna, algae and other biological investigations, water system projects and expert statements.


Mika Vestenius
Research Scientist at the Meteorological Institute, who specialises in PAH measurements, laboratory analyses of atmospheric pollutants, and air quality measurements and calibration.


Tiia Finér
Development Manager at Metsä Fibre’s Joutseno pulp mill, who also supervises the mill’s development team and laboratory. As local environmental manager, she is in charge of the mill’s cooperation with the authorities.