A sustainable circular economy needs efficient utilisation of side streams

​A comprehensive circular economy is incomplete without the bioeconomy. The bioeconomy can contribute in several ways to the circular economy, and this includes the utilisation of organic side and waste streams from forestry and the converting of these production side streams into value-adding products. Metsä Fibre has world-leading capabilities in this field.


​Global population increases and rising prosperity levels are currently responsible for an ever-increasing demand for natural resources like water, minerals, metals, energy and wood. This large-scale production and consumption of resources has led to both higher emissions of greenhouse gases, with its resultant adverse impact on climate change, and to greater resource scarcity.

To help mitigate the environmental threat for future generations, improved recycling, for example, is leading to the greater recovery and reuse of resources, which in turn leads to a more sustainable circular economy. Additionally, technological innovations are helping to both advance the production of renewable energy and to further the bio-based economy as a whole.

For its part, Metsä Fibre seeing new opportunities for green growth and driven by technological innovations and development – is continuing to set new benchmarks, particularly in the last few years, in terms of its efficient utilisation of side streams from its main raw material, wood.

In 2018, around 94% of Metsä Group’s production side streams were utilised, either as material, or in the production of renewable energy. As a Group, side streams contribute to around 5% of the entire production. These side streams that include ash, sludge and lime by-products are valuable and can be used, for example, for making fertilisers, in land construction, and for numerous chemical industry applications.

The European Commission defines the circular economy as an economic system in which “...the value of products, materials and resources is maintained in the economy for as long as possible, and the generation of waste minimised.” Likewise, it defines the bioeconomy as “the production of renewable biological resources and the conversion of these resources and waste streams into value added products, such as food, feed, bio-based products and bioenergy."

Metsä Fibre is continuing to set new benchmarks in terms of its efficient utilisation of side streams from its main raw material, wood

In recent years, the bio-based sector as a whole has seen a number of benchmark improvements implemented. These advances in bio-based innovations have helped strengthen the circularity of the bio-based sector by enabling the processing of current side streams, residues and wastes, into low and high-value by-products. Metsä Fibre has world-leading capabilities in this field, allowing it to create and to commercialise new bioproducts, as well as to utilise side streams in the production of renewable energy.

Certain high-value end-products like cellulose-based textile fibres are not classified as side streams, but rather are new products developed from the pulp itself. This is a rapidly growing area of some considerable importance to the Metsä Group as a whole, and the expertise and energies invested in it have led to the establishing and construction of a pulp-based textile fibre demo plant, the first project of the recently founded Metsä Spring innovation company.

​Bringing clarity to complexity

Begins Timo Kanerva, Environmental Director, Metsä Group, “Side streams are a complicated topic. For the general public, I think the terminology and concepts are not the easiest ones to understand. But, right from the outset, if we want to make things a little clearer, we can take the whole side stream umbrella and then we can divide it into three different sections: bioproducts, by-products and waste.”

The term ‘side stream’ is a very wide definition that basically includes everything that comes out of a mill that is not the main product (wood pulp). With the bioproduct mill concept we have learned to realise that some of these side streams, such as tall oil and turpentine, are in fact valuable products themselves and are part of the bioproduct portfolio on the global market. Other side streams are more or less valuable as products, raw materials or in renewable energy production. A very small share of the side streams is currently waste, and its share is constantly decreasing as new end uses are created.

Inclusion / exclusion

We arrive at the materials that are classified as genuine side streams and waste, substances derived from the production of wood pulp. These are by-products with lower value which are used in the fertiliser industry, for example. Ash from the power plants can be used as a fertiliser or soil improvement agent. Also lime and lime dust are derived from the chemical recycling process of the pulp mill and have some commercial value.”

In addition to those previously mentioned materials, there are other notable by-products too. Screening fibre fractions, for example, are certain parts of wood that come from the pulp mill that have been rejected, while sandy bark is from the wood yards where bark is being cleaned and contains sand and impurities within it. De-inking sludge comes from the recycling process of recovered paper. From that process, the fibre itself continues to further uses and the rest, such as kaolin and other coating materials create the de-inking sludge, which in the circular economy can today be utilised in many ways. These are by-products that are no longer defined as waste, but still remain of fairly low commercial value. That said, nearly all of them have ‘real-world uses’ and are able to increasingly contribute to the circular economy, depending on what kind of side streams they are.

“We can take the whole side-stream umbrella and then we can divide it into three different sections: bioproducts, by-products and waste.” adds Kanerva, “We are developing the utilisation of these side streams all the time and the market in this respect is very interesting. Furthermore, the value of it is growing as globally there is more interest in using recycled materials as part of circular economy. As a result, we are trying to make it more valuable and high-quality and many things are happening in that area.”


A growing market

Explains Sanna Pulkkinen, Development Manager, Metsä Group, “With regards to side streams viewed from an economic perspective, on the company level, we are looking at an overall figure in the many tens of millions of euros. This is the magnitude and value of side streams at the moment. Most of the turnover on side streams comes from biochemicals, such as tall oil and turpentine. But, if you are talking about the less valuable side streams, there is a potential for that to grow and to become a real business as well.”

Adds Kanerva, “Many of these materials such as ash and lime dust were considered waste ten years ago and were simply taken to the landfill. Now we are talking about large fractions of the material streams that are now no longer considered as waste. They are by-products and they are becoming more and more valuable raw materials, or fertilisers for agriculture to use instead of conventional fertilisers from fossil sources. It is a very big cultural change, as well as a big change in this industry. Within the next 5-10 years this area will develop much further.”

Currently, around 94% of Metsä Group’s production side streams are utilised. These side streams fall into five categories: energy utilisation, material utilisation, fertilising and soil improvement, and industrial use.

​Only 6% of production side streams are today classified as waste. The main waste fraction is green liquor sludge from pulp mills, the non-dissolvable inorganic parts of wood which are hard to utilise. The rest consists of, for example, waste pigments or hazardous waste such as certain lubricating oils, paints and laboratory chemicals. Their future utilisation remains part of the work of research and development teams.

Says Pulkkinen, “Lime mud waste is another material coming from the pulp mills. Usually it is being recycled back to the process, but some small percentages turn out as waste and are landfilled. With advances in technical development, and an increased awareness of the multiple benefits of moving towards a circular economy, waste water treatment sludges are nowadays mostly utilised as energy or biogas, so they are not going into the landfills anymore. The fact that 94% is utilised is actually a pretty good number and is a reflection of the ongoing research, development and innovation throughout Metsä Group across recent years.”

Future ambitions

State-of-the-art facilities like Metsä Fibre’s Äänekoski bioproduct mill have shown in recent years that they can improve the efficiency of biomass utilisation by increasing the usage of side streams, as well as reducing and /or recovering waste and residues. Furthermore, the most sustainable and innovative developments from the Äänekoski bioproduct mill can also be taken into use in Metsä Fibre’s other mills in the near future, a result that will lead to greater economies of scale, more optimised ‘circular’ production capabilities and higher-value end products. Taken together, the net result will be the setting of new benchmarks in terms of improved resource efficiency and minimising the amount of waste, as well as the creation of greater efficiencies with regards to material recycling and circularity. To that end, the transformation of waste and other side streams into higher added value products will produce increasing economic and resource efficiency benefits for Metsä Fibre, and Metsä Group as a complete entity, as well as for society and the environment as a whole.

The most sustainable and innovative developments from the Äänekoski bioproduct mill can also be taken into use in Metsä Fibre’s other mills in the near future. All efforts to date to improve and to advance the circular economy and bioeconomy are simply part of a longer, multi-generational change, as the complexity and research needed is an ongoing process. In the end, nobody really wants to hear the word ‘landfill’ anymore, as it suggests a process or utilisation failure. The future is clearly defined and Metsä Fibre, being a pioneer in the circular economy and the utilisation of side streams, is determined to continue its innovative development path.
To that end, further improving resource efficiency and being able to utilise all the production side streams by 2030 is one of Metsä Group’s renewed strategic sustainability objectives.

 “The ambition is to utilise all side streams. We are getting closer and closer,” concludes Kanerva.

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