Pulp lends itself to many things

​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

One way to use pulp is to replace plastic with it. This is exactly what Aqvacomp, for one, is doing. Located next to Metsä Fibre's Rauma mill, Aqvacomp uses pulp fibre in the production of biocomposite.

Biocomposite is a composite material in which plastic is strengthened with long-fibred softwood pulp.

The material is light and durable, and it is used in the production of parts used in musical instruments, household appliances and vehicles, among other things.

Pulp fibre may account for as much as 70% of the end product. The product looks and feels like wood, and behaves like wood with sound. In terms of its workability, however, it is faster than wood: with injection moulding, a guitar's fretboard can be finished in a minute.

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 sown from fibres made by Metsä Group. The production of textile fibres is expected to begin in the first half of 2020 at the Äänekoski demo plant of innovation company Metsä Spring and Itochu.

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 by CP Kelco, located at Äänekoski and owned by the American Huber Company.  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's 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.

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. The Äänekoski bioproduct mill alone produces so much energy that it would be sufficient to heat 100,000 single-family houses.

The mill also converts wastewater sludge into biopellets, which are used for heat production by power plants. In the future, the sludge can also be used to produce biogas for the transport industry.

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 the side streams of pulp and pulp cooking are:

  • tableware, plastic-like products, textiles, 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, the 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 heating (from black liquor)
  • product gas, bark mulch (from bark)
  • biopellets and biogas (from wood-based wastewater sludge)

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