wood pulp

Wood pulp is a dry fiberous material prepared by chemically or mechanically separating the fibers which make up wood. Pulp can be either fluffy or formed into thick sheets. The latter form is used if the pulp must be transported from the pulp mill to a paper mill. Pulp which is shipped and sold as pulp (not processed into paper in the same facility) is referred to as market pulp. When suspended in water the fibers disperse and become more pliable. This pulp suspension can be laid down on a screen to form a sheet of paper, and this is the primary use for wood pulp. Wood pulp is the most common material used to make paper. The timber resources used to make wood pulp are referred to as pulpwood. Wood pulp comes from softwood trees such as spruce, pine, fir, larch and hemlock, and hardwoods such as eucalyptus, aspen and birch.

History

Using wood to make paper is a fairly recent innovation. In the 1800s, fiber crops such as linen fibres were the primary material source, and paper was a relatively expensive commodity. The use of wood to make pulp for paper began with the delevopment of mechanical pulping in Germany by F.G. Keller in the 1840s[]. Chemical processes quickly followed, first with J. Roth's use of sulfurous acid to treat wood, followed by B. Tilghman's US patent on the use of calcium bisulfite, Ca(HSO3)2, to pulp wood in 1867.[] Almost a decade later the first commercial sulfite pulp mill was built in Sweden. It used magnesium as the counter ion and was based on work by C.D. Eckman. By 1900 sulfite pulping had become the dominant means of producing wood pulp, surpassing mechanical pulping methods. The competing chemical pulping process, the sulfate or kraft process was developed by Carl Dahl in 1879 and the first kraft mill started (in Sweden) in 1890.[0] The invention of the recovery boiler by G.H. Tomlinson in the early 1930s [0] allowed kraft mills to recycle almost all of their pulping chemicals. This, along with the ability of the kraft process to accept a wider variety of types of wood and produce stronger fibers [3] made the kraft process the dominant pulping process starting in the 1940s.[0]

Global production of wood pulp in 2006 was 160 million tonnes (175 million tons)[4]. In the previous year, 57 million tonnes (63 million tons) of market pulp (not made into paper in the same facility) was sold, with Canada being the largest source at 21% of the total, followed by the US at 16%. Chemical pulp made up 93% of market pulp.[5]

Manufacture of wood pulp

Main article: Pulp mill

Harvesting trees

Most pulp mills use good forest management practices in harvesting trees to ensure that they have a sustainable source of raw materials. One of the major complaints about harvesting wood for pulp mills is that it reduces the biodiversity of the harvested forest. Trees raised specifically for pulp production account for 16% of world pulp production, old growth forests 9% and second- and third- and more generation forests account for the balance[6], . Reforestation is practiced in most areas, so trees are a renewable resource. The FSC (Forest Stewardship Council) certifies paper made from trees harvested according to guidelines meant to ensure good forestry practices.[7]

The number of trees consumed depends whether mechanical processes or chemical processes are used. It has been estimated that based on a mixture of softwoods and hardwoods 12 meters (40 ft) tall and 15-20 centimeters (6-8 in) in diameter, it would take an average of 24 trees to produce 0.9 tonne (1 ton) of printing and writing paper, using the kraft process (chemical pulping). Mechanical pulping is about twice as efficient in using trees since almost all of the wood is used to make fiber therefore it takes about 12 trees to make 0.9 tonne (1 ton) of mechanical pulp or newsprint. [1]

Preparation for pulping

Only the heartwood and sapwood are useful for making pulp. Bark contains relatively few useful fibers and is removed and used as fuel to provide steam for use in the pulp mill. Most pulping processes require that the wood be chipped and screened to provide uniform sized chips.

Pulping

There are a number of different processes which can be used to separate the wood fibers:

Mechanical pulp

Manufactured grindstones with embedded silicon carbide or aluminum oxide can be used to grind small wood logs called "bolts" to make "stone groundwood" pulp (SGW). If the wood is steamed prior to grinding it is known as "pressure groundwood" (PGW) pulp. Most modern mills use chips rather than logs and ridged metal discs called refiner plates instead of grindstones. If the chips are just ground up with the plates, the pulp is called "refiner mechanical" pulp (RMP) and if the chips are steamed while being refined the pulp is called "thermomechanical" pulp (TMP). Steam treatment significantly reduces the total energy needed to make the pulp and decreases the damage (cutting) to fibers. Mechanical pulps are used for products that require less strength, such as newsprint and paperboards.

Chemithermomechanical pulp

Wood chips can be pretreated with sodium carbonate, sodium hydroxide, sodium sulfite and other chemical prior to refining with equipment similar to a mechanical mill. The conditions of the chemical treatment are much less vigorous (lower temperature, shorter time, less extreme pH) than in a chemical pulping process since the goal is to make the fibers easier to refine, not to remove lignin as in a fully chemical process. Pulps made using these hybrid processes are known as chemi-thermomechanical pulps (CTMP).

Chemical pulp

Main article: Kraft process
Main article: Sulfite process
Chemical pulp is produced by combining wood chips and chemicals in large vessels known as digesters where heat and the chemicals break down the lignin, which binds the cellulose fibers together, without seriously degrading the cellulose fibres. Chemical pulp is used for materials that need to be stronger or combined with mechanical pulps to give a product different characteristics. The kraft process is the dominant chemical pulping method, with sulfite process being second.

Recycled pulp

Main article: Paper recycling
Pulp can also be made out of waste paper and paperboard. Recycled pulp is most often used to make paperboard, newsprint or sanitary paper.

Bleaching

The pulp produced up to this point in the process can be bleached to produce a white paper product. The chemicals used to bleach pulp have been a source of environmental concern, and recently the pulp industry has been using alternatives to chlorine, such as chlorine dioxide, oxygen, ozone and hydrogen peroxide.

Environmental concerns

The major environmental impacts of producing wood pulp come from its impact on forest sources and from its waste products.

Forest resources

Main article: Logging
Main article: Plantations#Forestry
The impact of logging to provide the raw material for wood pulp is an area of intense debate. Modern logging practices, using forest management seeks to provide a reliable, renewable source of raw materials for pulp mills. The practice of clear cutting is a particularly sensitive issue since it is a very visible effect of logging. Reforestation, the planting of tree seedlings on logged areas, has also been criticized for decreasing biodiversity because reforested areas are monocultures. Proponents of reforestation and plantations argue that in this respect trees are no different from any other agricultural crop. Logging of old growth forests accounts for less than 10% of wood pulp[6], but is one of the most controversial issues.

Effluents from pulp mills

Pulp mills are almost always located near large bodies of water because of they require substantial quantites of water for their processes. Delignification of chemical pulps releases considerable amounts of organic material into the environment, particularly into rivers or lakes. The wastewater effluent can also be a major source of pollution, containing lignins from the trees, high biological oxygen demand (BOD) and dissolved organic carbon (DOC), along with alcohols, chlorates, heavy metals, and chelating agents. Reducing the environmental impact of this effluent is accomplished by closing the loop and recycling the effluent (see black liquor) where possible, as well as employing less damaging agents in the pulping and bleaching processes.

Mechanical pulp is not a major cause for environmental concern since most of the organic material is retained in the pulp, and the chemicals used (hydrogen peroxide and sodium dithionite) produce benign byproducts (water and sodium sulfate (finally), respectively).

Bleaching with chlorine produces large amounts of organochlorine compounds, including dioxins[8]. Increased public awareness of enviromental issues, as evidenced by the formation of organizations like Greenpeace, influenced the pulping industry and governments to address the release of these materials into the environment[9] . The amount of dioxin has been reduced dramatically by replacing some of all of the chlorine with chlorine dioxide[10]. The use of elemental chlorine has declined significantly and as of 2005 was used to bleach 19-20% of all kraft pulp[10]. EFC (elemental chlorine-free) pulping using chlorine dioxide is now the dominant technology worldwide (with the exception of Finland and Sweden where TCF is very important), accounting for 75% of bleached kraft pulp globally[10]

Chemical pulp mills, especially kraft mills, are energy self-sufficient and very nearly closed cycle with respect to inorganic chemicals.

Alternatives

Today, some people and groups advocate using field crop fiber or agricultural residues instead of wood fiber as being more sustainable. However, wood is also a renewable resource, with about 90% of pulp coming from plantations or reforested areas.[6] Non-wood fiber sources account for about 5-10% of global pulp production, for a variety of reasons, including seasonal availability, problems with chemical recovery, brightness of the pulp etc. [12][5]

Research is under way to develop biological pulping, similar to chemical pulping but using certain species of fungi that are able to break down the unwanted lignin, but not the cellulose fibres. This could have major environmental benefits in reducing the pollution associated with chemical pulping.

References

1. ^ Biermann, Christopher J. (1993). Essentials of Pulping and Papermaking. San Diego: Academic Press, Inc.. ISBN 0-12-097360-X. 
2. ^ E. Sjöström (1993). Wood Chemistry: Fundamentals and Applications. Academic Press. 
3. ^ History of Paper. Retrieved on 2007-10-08.
4. ^ Pulp production growing in new areas (Global production). Metso Corporation (Sept. 5, 2006). Retrieved on 2007-10-13.
5. ^ Overview of the Wood Pulp Industry. Market Pulp Association (2007). Retrieved on 2007-10-13.
6. ^ Martin, Sam (2004). Paper Chase. Ecology Communications, Inc.. Retrieved on 2007-09-21.
7. ^ Certification Tracking products from the forest to the shelf. Retrieved on 2007-09-21.
8. ^ Effluents from Pulp Mills using Bleaching - PSL1. ISBN: 0-662-18734-2 DSS. Health Canada (1991). Retrieved on 2007-09-21.
9. ^ Sonnenfeld, David A. (1999). "Social Movements and Ecological Modernization: The Transformation of Pulp and Paper Manufacturing, Paper: WP00-6-Sonnenfeld". Berkeley Workshop on Environmental Politics, Berkeley,CA: Institute of International Studies (University of California, Berkeley). Retrieved on 2007-09-20. 
10. ^ ECF: The Sustainable Technology. Alliance for Environmental Technology. Retrieved on 2007-09-19.
11. ^ Frequently Asked Questions on Kraft Pulp Mills. Ensis/CSIRO (Australia) joint research [2] (March 4, 2005). Retrieved on 2007-09-21.
12. ^ Judt, Manfred (Oct-Dec 2001). "Nonwoody Plant Fibre Pulps". Inpaper International. Retrieved on 2007-10-07. 

See also

External link

The WOOD callsign may refer to:
  • WOOD-TV – an NBC-affiliated television station in Grand Rapids, Michigan
  • WOOD (AM) – an AM radio station in Grand Rapids, Michigan
  • WOOD-FM - an FM radio station in Grand Rapids, Michigan




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A pulp mill is a manufacturing facility that converts wood chips or other plant fiber source into a thick fiber board which can be shipped to a paper mill for further processing.
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paper mill is a factory devoted to making paper from wood pulp and other ingredients using a Fourdrinier Machine or similar apparatus. It is a common misconception that paper mills are sources of odors. Pulp mills, not paper mills can be a source malodorous air emissions.
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Paper is thin material used for writing upon, printing upon or packaging, produced by the amalgamation of fibres, typically vegetable fibers composed of cellulose, which are subsequently held together by hydrogen bonding.
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Paper is thin material used for writing upon, printing upon or packaging, produced by the amalgamation of fibres, typically vegetable fibers composed of cellulose, which are subsequently held together by hydrogen bonding.
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Pulpwood refers to timber grown with the principal purpose of making wood pulp for paper production. However, pulpwood is also used as the raw material for some wood products, such as oriented strand board (OSB), and there is an increasing demand for pulpwood as a source of 'green
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Softwood is a generic term used in woodworking and the lumber industries for wood from conifers (needle-bearing trees from the order Pinales). Softwood-producing trees include pine, spruce, cedar, fir, larch, douglas-fir, hemlock, cypress, redwood and yew.
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Picea
Link

Species
About 35; see text.

Spruce refers to trees of the genus Picea, a genus of about 35 species of coniferous evergreen trees in the Family Pinaceae, found in the northern temperate and boreal (taiga) regions of
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Pinus
L.

Subgenera
  • Subgenus Strobus
  • Subgenus Ducampopinus
  • Subgenus Pinus
See Pinus classification for complete taxonomy to species level.
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FIR may stand for:
  • FIR FILM IMPACT RECAP directed by trident and hosted by kathi selvakumar on rogers channel 622
  • Finite impulse response, a digital filter type.

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Larix
Miller

Species
About 12; see text

Larches are conifers in the genus Larix, in the family Pinaceae. They are native to much of the cooler temperate northern hemisphere, on lowlands in the far north, and high on mountains
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Tsuga
Carrière

Species

Tsuga canadensis  Eastern Hemlock
Tsuga caroliniana  Carolina Hemlock
Tsuga chinensis  Taiwan Hemlock
Tsuga diversifolia  Northern Japanese Hemlock

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hardwood designates wood from broad-leaved (mostly deciduous, but not necessarily, in the case of tropical trees) or angiosperm trees. Hardwood contrasts with softwood, which comes from conifer trees.
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Eucalyptus
L'Hér.

natural range


Species

About 700; see the List of Eucalyptus species

Eucalyptus
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Populus

Species

Populus adenopoda
Populus alba
Populus grandidentata
Populus sieboldii
Populus tremula
Populus tremuloides

Aspens
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Betula
L.

Species

Many species;
see text and classification

Birch is the name of any tree of the genus Betula (Bé-tu-la
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Paper is thin material used for writing upon, printing upon or packaging, produced by the amalgamation of fibres, typically vegetable fibers composed of cellulose, which are subsequently held together by hydrogen bonding.
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Synthenoids are field crops grown for their fibers, which are used to make paper[1], cloth, or rope. These crops are generally harvestable after a single growing season, as opposed to trees which are typically grown for many years before being harvested for wood pulp
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Linen is a material made from the fibers of the flax plant.'''

Flax fiber

The term "linen" refers to yarn and fabric made from flax fibers; however, today it is often used as a generic term to describe a class of woven bed, bath, table and kitchen textiles because
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The Kraft process (also known as Kraft pulping or sulfate process) produces wood pulp which is almost pure cellulose fibers by using sodium hydroxide and sodium sulfide to extract the lignin from wood chips in large pressure vessels called digesters.
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Motto
(Royal) "För Sverige - I tiden" 1
"For Sweden – With the Times" ²

Anthem
Du gamla, Du fria
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Recovery boiler is the part of Kraft process of pulping where chemicals for white liquor are recovered and reformed from black liquor. In the process lignin of the wood, bound in black liquor at this phase, is burned and heat generated.
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This page is currently protected from editing until disputes have been resolved.
Protection is not an endorsement of the current [ version] ([ protection log]).
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Us is a pronoun in the English language, the objective form of we.

US (capitalized) is an alternative of the abbreviation U.S. which generally refers to the United States of America.

US , U.S.
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A pulp mill is a manufacturing facility that converts wood chips or other plant fiber source into a thick fiber board which can be shipped to a paper mill for further processing.
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Forest management includes a range of human interventions that affect forest ecosystems. all about forestry management ,conservation forest , and forest for economicaly. timber, planting and replanting of various species, cutting roads and pathways through forests and techniques
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Biodiversity is the variation of life forms within a given ecosystem, biome or for the entire Earth. Biodiversity is often used as a measure of the health of biological systems.
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Reforestation is the restocking of existing forests and woodlands which have been depleted, with native tree stock. The term reforestation can also refer to afforestation, the process of restoring and recreating areas of woodlands or forest that once existed but were deforested or
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The Kraft process (also known as Kraft pulping or sulfate process) produces wood pulp which is almost pure cellulose fibers by using sodium hydroxide and sodium sulfide to extract the lignin from wood chips in large pressure vessels called digesters.
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Newsprint is low-cost, low-quality, non-archival paper. It is generally made by a mechanical milling process, without the chemical process that is usually used to remove lignin from the pulp.
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