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Production of pulp

Pulp production is essentially the cooking of wood chips in a chemical solution in order to break loose the fibers. The resulting pulp can be used as a raw material for making paper, board and many other products. Creating just the right kind of raw material for a specific end-product requires profound knowledge and expertise in fibers.

The type of raw material significantly affects the properties of paper and board. Softwood (e.g. pine and spruce) and hardwood (e.g. eucalyptus and birch) give different characteristics for pulp.

From how far is the wood is coming from? In 2015, according to EPIS LCI averages, in Nordic countries 3/4 of the spruce and pine came in by truck from an average distance of 106 km. Some wood was brought in by rail and 1% by floating. In Brazil, 87% of the eucalyptus wood is brought in from a radius of 187 km, also sea barges are used to transport the wood to the pulp mills.

 

Significant production of energy and other bioproducts 

Wood is used very efficiently, with a significant part of the raw material extracted as pulp fiber. The rest is used as a bioenergy source for generating heat and electricity and to make other bioproducts. Softwood pulp production generates tall oil and turpentine for the chemical industry's specialty products and biofuels. Modern pulp mills generate more bioenergy than they use. The excess energy is sold.

 

Environmental impacts are minimized

Recovery of cooking chemicals takes place in the recovery boiler, where the chemicals are regenerated for re-use by causticizing. Gradual enclosure of water cycles and better internal cleaning of the process have reduced the volume of effluent, with a consequent reduction in adverse impacts on waterways. Effluent is treated biologically prior to discharging into water. Fuel gases are scrubbed, and malodorous gases originating in the process are recovered and burned.

 

2015 data Northern bleached softwood kraft Bleached eucalyptus kraft pulp
Countries Finland and Sweden Brazil and Uruguay
TOTAL SUBSTANCES IN PROCESS WATER
Chemical Oxygen Demand, kg/ton

13,8

7,3
Nitrogen, kg/ton 0,16 0,10
Phosphorus, kg/ton 0,02 0,04
EMISSIONS TO AIR
Dust, kg/ton 0,35 0,36
Fossil CO2, kg/ton 67 155

EPIS has contributed to the international life cycle inventory databases, the European Commission Life Cycle Data Network and Ecoinvent, by collecting environmental data from its member company pulp mills.

Main applications

Pulp is used in a vast number of different end-uses, but the main applications areas are tissue, board, printing and specialty paper manufacturing as well as in textiles.

Board products

Board manufacturers are often integrated, i.e. they have their own pulp mills, but market pulp is also used. Board products including bleached chemical pulps are used as packaging materials and storing liquids and many types of dry materials.  

Important characteristics of the pulp include strong fibers with good surface and optical properties, cleanliness and brightness. 

Tissue products

Tissue production covers a wide variety of products such as soft toilet paper, kitchen towels, napkins, hankies, facial tissue and more.

Both softwood and hardwood pulps are used; the softness in a tissue product comes from the hardwood content of eucalyptus and birch pulp. They give the product both strength and softness. Absorption, wet and dry strength are other important properties in tissue products.

Printing products

Printing is traditionally divided in two main segments, fine papers and magazines.

Pulp gives the printing papers a good balance of optical and strength properties, bulk and printability depending on the end use.

Magazine paper producers buy their softwood pulp to increase the wet and dry strength of the paper.

Speciality paper

The specialty paper area covers a huge range of papers such as filter papers, label papers, release liners, d├ęcor paper, medical paper, wallpaper, packaging papers etc. The end use requirements vary widely depending on the application.

Dissolving pulp for textiles, apparel and other products

The main market for dissolving pulp is the textile industry, for example, in the manufacture of viscose. Wood fibers have been used in clothing manufacture since the 1920s. Today, 4-5 percent of the world's textile fibers are based on cellulose from wood, corresponding to approximately four million tons of pulp, with the amount increasing.

The end products include for example

  • clothing, fabrics, yarn
  • non-wovens for hygiene products
  • fibrous sausage casings
  • cellophane, sponges and other products.
  • Nano-cellulose and nanocrystals

Nanocellulose and nanocrystals are in development phase and finding applications as

  • Alternative to metallic materials
  • Bioplastics
  • Medications and cosmetics
  • Drilling fluids
  • Cellulose foams
  • Flexible and LCD screens
  • Anti-coking agents and texture stabilizer

Microfibrillated cellulose (MFS) is a renewable and biodegradable raw material finding applications such as packaging, barrier films, specialty papers or coatings and adhesives. 

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Cellulose is more than a collection of naturally occurring fibers. Fibril and chemical properties can be tailored, and new materials can be constructed with predefined structural engineering leading to new material design.  With all that, nonrenewable fossil materials can be replaced with renewable materials for a more sustainable world.

A single tree

What you get from a single tree?

Enough raw materials for

30000 sheets of A4-paper or
7000 milk cartons or
1100 toilet paper rolls

And by-products and residues for

Renewable diesel.
Biochemicals
And renewable energy production.

Pulp vocabulary

BLACK LIQUOR:

a substance resulting from the wood cooking process, mainly composed of organic and inorganic materials and remaining dissolved wood (lignin)

LIGNIN: 

residues of dissolved wood

CAUSTICIZING:

a process that recovers the main chemical used in the wood cooking process, lye (sodium hydroxide). This is done by adding lime to the black liquor.

WHITE LIQUOR:

solution used in cooking wood, responsible for separating the cellulose fibers from the lignin.

SCRUBBER:

Scrubber systems are a diverse group of air pollution control devices that can be used to remove particulates and/or gases from industrial exhaust streams.