How is paper made?
The technology for paper manufacturing has evolved significantly in recent years, but the major production steps remain the same. To manufacture paper, the paper industry requires cellulose fibers.
Wood, the raw material
Cellulose fibers are primarily obtained from by-products of forestry (sawdust, wood chips, etc.) as well as from recycled papers and cardboard. Additives may be added to the cellulose to improve the characteristics of the paper.
The cellulose fibers, which are held together by lignin, need to be separated to produce pulp from wood. This separation can be done by grinding the wood on millstones or by chemical treatment in large autoclaves. Mechanical pulp is used to produce newsprint, while the chemical pulp is used to manufacture high-strength papers such as grocery bags.
To produce pulp from recovered cardboard, they need to be shredded and suspended in water. After being agitated, cleaned, and de-inked, they become recycled pulp. This type of pulp is generally used to produce cardboard or papers for domestic or industrial use.
The pulp is subjected to chemical treatments to obtain whiter papers that remove more lignin. Although this bleaching process is now better controlled, it remains expensive and environmentally harmful.
Paper sheet formation
The pulp needs to be drained of a large amount of water it contains. The pulp is sprayed onto a moving mesh screen to achieve drainage and then pressed between rollers. The sheet that comes out is then dried (using steam, infrared, air cushions, or microwaves).
Paper mills produce different types of paper. Depending on the desired finish, the sheet may be smoothed and/or coated with clays, pigments, and/or dyes to improve its properties, particularly for printing. Finally, the sheet is rolled into a reel before being cut into sheets or smaller reels, ready for delivery.
While the papermaking process has become more sustainable over time, environmental considerations remain. For example, water usage is a significant factor in paper production, and efforts are being made to implement water recycling systems to reduce water consumption. Energy consumption and emissions are also concerns.
Paper mills are adopting renewable energy sources and improving production processes to reduce their environmental impact.
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