The story of paper
Paper has a long history stretching back to ancient Egypt in the third millennium BC.
The word ‘paper’ is derived from papyrus, a plant that was once abundant in Egypt and which was used to produce a thick, paper-like material by the ancient Egyptians, Greeks and Romans.
Paper as we know it traces its roots back to China at the beginning of the first millennium AD. Traditional Chinese records give the credit for its development to one T’sai Lun (about 105AD). He was subsequently deified as the god of papermakers!
Paper making was regarded as a craft and was produced by a small amount of artisan paper crafters until the 19th century when paper production was industrialised. Although paper was originally only intended for writing and printing, today it is used in many different forms.
How paper is made
There are 3 main stages in paper and paper based packaging production, namely;
- Growing and harvesting of raw material
The main source of wood fibre used in the manufacture of paper and paper based packaging comes from trees grown in plantations. Either hardwood (Gum Trees) or softwood (Pine Trees) is harvested for conversion into a number of varying grades of paper. Another source of wood fibre is the wood chips and off-cuts from sawmills followed by the recovery of all types of paper from recycling.
In addition to wood fibre, several chemicals and water are used to convert the raw material into paper. The bulk of the chemicals and virtually all the water is recovered and re-used in the process.
The first step in pulping is to remove the bark from the trees as the bark cannot be used to produce wood fibres. The bark is not discarded but used as fuel to create steam. The steam is used to generate electricity and when released from the turbine, it is used either as heat during the pulping process or in the paper mill for drying the paper.
Pulping is the process of separating the wood fibres that make up wood logs or wood chips, creating a pulp. There are 2 types of pulping processes:
- Mechanical pulping separates the raw wood fibres by grinding the wood logs or chips, no chemicals are used.
- Chemical pulping is done by cooking wood chips at high temperatures and pressures in a chemical solution, separating the raw wood fibres.
Unprocessed wood pulp is brown in colour and is bleached to produce white paper. Chlorine dioxide, oxygen, ozone and hydrogen dioxide are used in a variety of combinations or stages to bleach the pulp.
The final stage of pulping is refining. The pulp passes through machines with rotating discs that effectively intertwine the fibres allowing strong bonds to form.
Paper is now made using a paper/board/tissue machine, which forms a continuous, uniform sheet of paper/board/tissue.
At the front end of the machine the pulp consists of about 1% wood fibre and 99% water. The pulp is deposited onto a forming screen and the water is extracted, the fibres begin to bond and a mat is formed. The mat, now about 80% water, passes through a series of pressure rollers, gradually reducing the water content to about 65%. The mat then passes over a series of steam heated drying cylinders to remove all the water. In the final step, the paper/board/tissue is wound into a large reel.
The environment and recycling
Trees indigenous to the region where the plantations are farmed are not used for paper manufacture. The co-existence of the planted trees and indigenous trees is taken into account during the planning phase of a new plantation.
Due to its adverse effect on the environment, elemental chlorine is no longer used in South Africa to bleach paper.
Paper is an organic material, meaning that as it decomposes it releases gases like carbon dioxide and methane. Both these gasses contribute significantly to the green-house effect. By recycling paper we retain the carbon content in a solid form, thus impeding the eventual release of these gasses into the atmosphere.
Recycling programmes encourage the public to collect as much waste paper as they possibly can from sources within their neighbourhoods. The collectors take their accumulated used paper to recycling centres where they receive payment according to the weight of the paper they deliver. Paper recycling bins are also available at points throughout towns and cities.
At central processing plants the recycled paper is sorted, compressed into bales and taken to paper mills where it is re-pulped and converted into new paper for packaging, writing paper and tissue paper.
It is difficult to recycle paper once it has reached the Municipal Dump Site, so the recycling process has to start in our homes, school, offices, supermarkets and factories.
For more in-depth information on how paper is made and paper recycling, go to www.thepaperstory.co.za