Pulp (paper)
Strips of bark or bast material were woven together, beaten into rough sheets, dried, and polished by hand.
[3][4] Pulp used in modern and traditional papermaking is distinguished by the maceration process which produces a finer, more regular slurry of cellulose fibers which are pulled out of solution by a screen and dried to form sheets or rolls.
[5][6][7] By the 6th century, the mulberry tree was domesticated by farmers in China specifically for the purpose of producing pulp to be used in the papermaking process.
In addition to mulberry, pulp was also made from bamboo, hibiscus bark, blue sandalwood, straw, and cotton.
[7] Papermaking using pulp made from hemp and linen fibers from tattered clothing, fishing nets and fabric bags spread to Europe in the 13th century, with an ever-increasing use of rags being central to the manufacture and affordability of rag paper, a factor in the development of printing.
[1][9][10] While some of the earliest examples of paper made from wood pulp include works published by Jacob Christian Schäffer in 1765 and Matthias Koops in 1800,[1][11] large-scale wood paper production began in the 1840s with unique, simultaneous developments in mechanical pulping made by Friedrich Gottlob Keller in Germany[12] and by Charles Fenerty in Nova Scotia.
The wood fiber sources required for pulping are "45% sawmill residue, 21% logs and chips, and 34% recycled paper" (Canada, 2014).
[18] Some of the most commonly used trees for paper making include softwoods such as spruce, pine, fir, larch and hemlock, and hardwoods such as eucalyptus, aspen and birch.
Pulp can be manufactured using mechanical, semi-chemical or fully chemical methods (kraft and sulfite processes).
Wood and other plant materials used to make pulp contain three main components (apart from water): cellulose fibers (desired for papermaking), lignin (a three-dimensional polymer that binds the cellulose fibres together) and hemicelluloses (shorter branched carbohydrate polymers).
Most pulp mills use good forest management practices in harvesting trees to ensure that they have a sustainable source of raw materials citation required.
The FSC (Forest Stewardship Council), SFI (Sustainable Forestry Initiative), PEFC (Programme for the Endorsement of Forest Certification), and other bodies certify paper made from trees harvested according to guidelines meant to ensure good forestry practices.
It has been estimated that based on a mixture of softwoods and hardwoods 12 metres (40 ft) tall and 15–20 centimetres (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).
Bark contains relatively few useful fibers and is removed and used as fuel to provide steam for use in the pulp mill.
Most modern mills use chips rather than logs and ridged metal discs called refiner plates instead of grindstones.
Steam treatment significantly reduces the total energy needed to make the pulp and decreases the damage (cutting) to fibres.
A mechanical force is applied to the wood chips in a crushing or grinding action which generates heat and water vapour and softens the lignin thus separating the individual fibres.
Many newsprint, toilet paper and facial tissue grades commonly contain 100 percent deinked pulp and in many other grades, such as lightweight coated for offset and printing and writing papers for office and home use, DIP makes up a substantial proportion of the furnish.
Organosolv pulping uses organic solvents at temperatures above 140 °C to break down lignin and hemicellulose into soluble fragments.
Steam exploded fibre is a pulping and extraction technique that has been applied to wood and other fibrous organic material.
Pulp made from non-wood plant sources or recycled textiles is manufactured today largely as a speciality product for fine-printing and art purposes.
[33] Hemp paper is a possible replacement, but processing infrastructure, storage costs and the low usability percentage of the plant means it is not a ready substitute.
[citation needed] However, wood is also a renewable resource, with about 90 percent of pulp coming from plantations or reforested areas.
[37] Important quality parameters for pulp not directly related to the fibres are brightness, dirt levels, viscosity and ash content.
The impact of logging to provide the raw material for wood pulp is an area of intense debate.
Modern logging practices, using forest management seek to provide a reliable, renewable source of raw materials for pulp mills.
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).
[38][39] Many mills have adopted alternatives to chlorinated bleaching agents thereby reducing emissions of organochlorine pollution.
Important quality parameters are wood furnish, brightness, viscosity, extractives, dirt count and strength.
The price had dropped due to falling demand when newspapers reduced their size, in part, as a result of the recession.
