Pulp lends itself to many things

Source: Metsä Fibre

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While we've known how to make pulp for over a hundred years now, its versatility keeps on surprising us.

What do shirts, speakers, toothpastes and mobile phone skins have in common? If you guessed wood, you’re right. Pulp made from Finnish wood can be used in the production of all of the above mentioned products. But what is pulp, really?

“Pulp is the tissue of wood from which lignin, or the substance that ties the wood fibres together, has been removed. It’s a composite made up of two elements – the amorphous and branched hemicellulose and the crystalline and strong cellulose,” says Raili Koponen, Development Manager at Metsä Fibre. Although Koponen has worked with pulp for her entire career, the material’s versatility still amazes her. 

“Pulp is an interesting material which can be used to make a huge variety of products.” 

It can replace plastic

The packaging industry is feverishly seeking packaging solutions to replace single-use plastics. The raw materials used in the new solutions should be renewable, and the footprint of the manufacturing process should be as small as possible. After use, the packaging should be easily recyclable, preferably biodegradable.

This type of packaging solutions are currently developed in Äänekoski, at the Metsä Group’s innovation company Metsä Spring and Valmet’s demo plant. The goal is to develop a 3D fibre product that can replace food packaging made from fossil-based raw materials, for example. One of the main raw materials of 3D fibre products is the pulp produced at the Äänekoski bioproduct mill. The products are not only recyclable, but also biodegradable.

You can wear it

Koponen takes out a strip of black cloth. It feels soft and elastic to the touch. Very similar to cotton, but cotton it is not. Instead, it is Finnish softwood.

“People will need to wear clothes in the future too. Fibres are needed, but the production volumes of cotton can’t increase,” says Koponen. If everything goes as planned, people in the future may well wear clothes manufactured from fibres made by Metsä Group. Metsä Spring and the Japanese ITOCHU Corporation have built a demo plant that produces wood-based textile fibres in Äänekoski. At the plant, pulp from the Äänekoski bioproduct mill is further processed into textile fibre through a new innovative manufacturing process. The currently on-going test runs are used to study the viability of the new manufacturing method. In the best case scenario, a significantly bigger textile fibre plant will be built in Finland in the future.

You can eat it

If you brushed your teeth this morning, chances are that you put pulp in your mouth. Or, to be precise, carboxymethylcellulose (CMC), converted from birch pulp.

CMC is produced in Äänekoski by Nouryon, an internationally operating company specialised in the manufacture of chemicals. CMC is used as a stabiliser and bulking agent in foodstuffs, for example. In terms of its appearance, it resembles potato flour or semolina. Some juice manufacturers use CMC to give their product a rich texture similar to pure juice. The next time you buy orange juice in the store, take a look at its product information to see if you can find the E number E466. It may very well be there.

New uses are being discovered all the time

You don’t need to browse the website of Chemarts – a collaboration between two Aalto University schools, The School of Chemical Engineering (CHEM) and The School of Arts, Design and Architecture (ARTS) – for long to realise that you can make just about anything out of pulp:
conductive non-woven fabrics, sheets used for sound-proofing or paint binders, to mention just a few examples. Time will tell which innovations will end up in production and all the way up to the markets.

“Everything has to start from the customer and their need. Recyclability is a value when it comes to pulp-based products, but you also need to determine the value through euros,” says Koponen.

In other words: As long as plastic is easy and cheap to use, it will be difficult for pulp-based products to push it off the market. Even so, the demand for biodegradable, bio-based and sustainably produced materials is growing continuously.

It’s bulk – in the good sense

Considering how versatile a material pulp is, it is almost surprising how easily it is dismissed sometimes. It would quite all right to make grand pianos and houses from Finnish wood, but pulp is seen as a bulk product.

“Not all trees can be grown into logs. According to the bioeconomy thinking, you want to use the entire tree, and pulp production gives pulpwood good added value. The chips generated as a by-product of sawing are also put to use in pulp production,” says Koponen.

She adds that while pulp is a bulk product, it is that in a good sense. “A kraft pulp mill is a carefully fine-tuned process which yields pulp of a consistent quality from different kinds of wood. So in our case, a bulk product is not synonymous with a low-value product. Instead, the value lies precisely in the product’s consistent quality.”

It is part of the circular economy

In a pulp mill, the bioeconomy thinking mentioned by Koponen means that applications are also found for all side streams of production. The majority of the production side streams are already in reuse.

For a long time now, the chemical industry has converted crude turpentine and crude tall oil into various varnishes, paints, inks and solvents, but they also lend themselves to other uses. In its crude form, turpentine, which has a pungent smell, is used as a raw material by the perfume industry, for example, while the tar-like tall oil yields plant sterols and stanols, which are used in the manufacturing of cholesterol-lowering products.

When the lignin removed from fibres in the cooking process is burned as black liquor in the recovery boiler, it generates bioenergy. There is enough bioenergy to be fed into the national grid as electricity and as heat to the nearby communities. For example, the electricity generation capacity of the Äänekoski bioproduct mill is equivalent to 2.5 per cent of the overall electricity production in Finland.

The bioproduct mill in Äänekoski also converts wastewater sludge into biopellets and biogas. Biopellets are used for heat production at power plants. Biogas, in turn, is suited for use as transport fuel, and Metsä Fibre´s partner Gasum is in charge of distributing it in its refuelling station network.
Veolia, on the other hand, will build a raw methanol processing plant in connection with the Äänekoski bioproduct mill. In the future, the raw methanol generated in pulp production will be refined into commercial biomethanol, which can be used as transport fuel, for example.

The Äänekoski bioproduct mill is already free of fossil fuels. According to Koponen, the mill also aims to be waste-free in the future. “Waste-free and fossil-free. That has to be the goal at the mill as well as at home.”

Just some of the products made from pulp and the side streams of pulp production are:

  • paperboard, tissue paper, printing paper and specialty paper (from pulp)
  • tableware, plastic-like products, textiles, packaging solutions, biocomposites (from pulp)
  • fertilisers and earthwork materials (from ash)
  • laundry detergents and raw materials for glass production (from Glauber’s salt)
  • adhesive products, composite plastics, transport fuels, consumer electronics (from lignin)
  • paints, car tyres, asphalt (from tall oil)
  • dyes, bulking agents of foodstuffs, sausage casing materials, surface coatings of pharmaceuticals, varnishes (from biochemicals produced in the context of the pulp process)
  • renewable electricity, district heat (from black liquor)

Source: Metsä Fibre