What is Wood Pulp?
Waste paper and wood pulp are purified cellulose fibers obtained from the raw material, primarily wood, which has been mechanically and/or chemically treated to separate the ‘glue’, which is called ‘lignin’, that holds wood fibers together. Some of uses of separated fibres from wood pulp includes paper, packaging, tissues, diapers, rayon clothes, and many other products.
The principle renewable material used in the paper and pulp is the wood pulp. A third party approximates that globally, about forty percent of the industrial wood supply is used to manufacture wood pulp. New technologies of pulp production show that more than 200 million tons of wood pulp are produced per year worldwide, which proves an increasing role of pulp in the modern society.
How is Wood Pulp Made?
Wood pulp can be produced using mechanical pulping and chemical pulping processes anybody’s main.
Mechanical Pulping
During the mechanical pulping process logs are fed into grinders and the logs are crushed through physcial means using grind stones or metal disks. This takes the fibers apart while leaving majority of the lignin behind. Some of the widely used mechanical pulps are the stone groundwood pulp, the pressurized groundwood pulp, the refiner mechanical pulp, and the thermomechanical pulp.
The advantages of mechanical process include high yield with this method yielding about 90% the valuable fibers in the wood as well as its relatively cheap nature. But the pulp produced contains most of the lignin and hence the fibres do not bond closely. This translated to mean that paper derived from mechanical pulp is less stronger and tends to stain very easily. Mechanical pulp is mainly applied in production of newsprint, paperboards, tissues, and packaging materials.
Chemical Pulping
Chemical pulping: wood chips are treated with chemicals that act to soften “the glue” that holds fibers in wood, the lignin. This makes the fibre longer and removes most of the lignin as shown below Boil the mass for 30 minutes in acidified water After boiling in an acidulated water the mass looks like this; Two main chemical pulping processes exist:
Sulfite Process – It involves cooking wood chips with an acid solution containing sulfurous acid bisulfite ions or sulfite ions. The spent cooking liquid can be recovered and reprocessed and is potentially a useful feedstock for synthesizing new products.
It’s mostly used Kraft Process otherwise known as Sulfate Process because it is the dominant process in the world. The chips are then subjected to a digestion by sodium hydroxide and sodium sulfide where the lignin bonds are dissolved. The used chemicals can be both recycled/processed and used again, therefore the general impact of chemical is relatively low/ Since chemical can be recycled the impact is thus minimal.
For example, kraft and sulfite pulps cause increased strength properties and brightness stability compared to mechanical pulps. It caters for the production of quality papers, boxes, packaging and white papers. The disadvantages of this method can be summed up to reduced returns because only half of the volume of the wood is converted into usable fibers and the fact that chemical costs are an additional expense.
Bleaching of Pulp
After pulping though mechanical or chemical pulping methods, the pulp may be bleached. This serves to wash off any residual lignin and also brightens the pulp. Some of the most used bleaching materials are chlorine, chlorine dioxide, oxygen, peroxide, hypochlorite and ozone. Nonetheless, bleaching processes may generate toxic organic species; as a consequence, the industry has transition to ECF and TCF.
What is Wood Pulp Used For?
Today, wood pulp serves as the foundation for producing many essential paper and packaging grades, including:
- Writing,Priting &Offce papers
- Newsprint & magazine papers
- Toilet papers, cloths, napkins
- Corrugated boxes & cartons
- Multiwall shipping sacks
- Grocery & shopping bags
- This included cups, plates, as well as any container that the food was served in.
- Nonwoven surgical masks, medical operative gowns & wipes
Outside of paper products, wood pulp is also commonly used to produce:
- Rayon, Lyocell & other Cellulosic Textiles
- Acetate textile fibers
- Spandex fibers filament yarns
- Nitrocellulose coatings & films
- Glassine & cellophane
- Bullet case and pyrotechnic device
- Photographic films
- Hygiene products
- Artificial sponges & casings
New Technologies and Methods in Wood Pulp Manufacturing
As global demand for sustainable, compostable fibers and packaging continues to grow, innovations in wood pulp processing and applications push forward:
- Specialty pulping create higher purity cellulose for textiles and filters.
- Microfibrillated & nanocellulose offer opportunities for applications to add strength with low weight.
- The new separation technologies have the benefits of lowering energy and chemical demands.
- Pulp-molded packaging, cups, and containers are novel products as substitute for plastics and foams with a potential for growth.
- New approaches for lignin and hemicelluloses re-depositing can be effected to enhance the deposition of the above constituents in specialty papers as well as in boards.
The Future of Wood Pulp
Even if innovations can appear and new sources of textile fibers or new characteristic of paper may appear, wood pulp is expected to be the major renewable material used in paper and packaging production all over the world up to 2050 and beyond. When it is undertaken responsibly and when production is optimized, wood pulp is set to deliver on society’s demand for sustainable fiber products well into the future.