Wood pulp is a type of papermaking material that is created by processing woods. It serves as the basis for the creation of a wide range of paper-based products. Several different processes are utilized to reduce the wood into wood pulp, a form that is ideal for manufacturing different types of paper goods such as paper used in printing books, magazines, and newspapers. The resulted paper product can also be used to create other paper products, including disposable paper plates, paper towels, and other common household items.
Wood pulp has been in use for centuries, with the first recorded use of wood pulp for paper production dating back to the 2nd century in China. However, the modern wood pulp industry started in the mid-19th century when the first wood pulp mill was established in the United States. Since then, wood pulp production has grown significantly, and it’s now a global industry that contributes to various sectors of the economy.
Types of Wood Pulp
Wood pulp can be classified into different types based on the process used to obtain it. The three main types of wood pulp are chemical, mechanical, and recycled pulp.
Chemical Wood Pulp
Chemical wood pulp is produced by chemically breaking down the lignin and hemicellulose in wood chips, leaving behind cellulose fibers. The two most common chemical pulping processes used to produce chemical wood pulp are the Kraft process and the sulfite process.
- Kraft Pulp
Kraft pulp is the most widely used chemical wood pulp and accounts for around 80% of global wood pulp production. The Kraft process involves cooking wood chips under high pressure and temperature in a mixture of chemicals, which dissolves the lignin and separates the cellulose fibers.
- Sulfite Pulp
Sulfite pulp is produced by using a mixture of sulfur dioxide and water to dissolve the lignin and hemicellulose in wood chips. Unlike the Kraft process, the sulfite process results in pulp with higher brightness and strength.
Mechanical Wood Pulp
Mechanical wood pulp is produced by mechanically grinding wood chips, which separates the fibers from the wood. There are three primary types of mechanical wood pulp: groundwood pulp, refiner mechanical pulp, and thermomechanical pulp.
- Groundwood Pulp
Groundwood pulp is produced by grinding wood chips against a revolving stone or metal disk. This process results in pulp with shorter fibers and lower strength than chemical wood pulp.
- Refiner Mechanical Pulp
Refiner mechanical pulp is produced by grinding wood chips between two metal plates, which separates the fibers. This process results in pulp with longer fibers and higher strength than groundwood pulp.
- Thermomechanical Pulp
Thermomechanical pulp is produced by mechanically grinding wood chips while adding steam and pressure. This process results in pulp with longer fibers and higher strength than groundwood pulp.
Recycled Wood Pulp
Recycled wood pulp is produced from waste paper, which is deinked and processed to remove any impurities. This type of pulp is commonly used in the production of newsprint and tissue paper.
Overall, the choice of wood pulp used depends on the end-use application and the properties required for the final product.
Wood Pulp Making Process
The methods for wood pulp manufacturing can be roughly divided into two: the mechanical pulping and the chemical pulping.
The mechanical process of reducing wood into wood pulp often includes the use of grinding machinery to create fine chips that can be refined using pressure and steam. This often involves introducing the tiny chips to a steaming process that helps to soften the fibers, making the product more malleable. From there, the pressure is exerted to create thin sheets, which are then become ideal paper products.
The chemical pulping, a slightly different approach to the creation of wood pulp, focuses on using a combination of chemicals in the pulp cooking process. This process serves to separate the wood fibers while the material is cooking in the chemical bath. The products produced by this method are more durable than those produced by steaming and pressurizing, and are especially suitable for the manufacture of hardwood based products. For example, sheets made of birch and other hardwood are usually made in this particular way.
Uses of Wood Pulp
Wood pulp is an essential raw material used in various industries, primarily in the production of paper and paper-based products. However, it has numerous other applications in different sectors, including:
Paper and Packaging Industry
- Printing and Writing Paper: Wood pulp is the primary raw material used in the production of printing and writing paper, including books, newspapers, magazines, and office paper.
- Packaging Materials: Wood pulp is also used in the production of various packaging materials, such as cardboard, cartons, and boxes.
- Tissue Paper: Tissue paper, including facial tissues, toilet paper, and paper towels, is made from wood pulp.
Textile Industry
- Rayon and Cellulose Acetate: Wood pulp is used to produce rayon, a synthetic fabric widely used in the textile industry. Additionally, cellulose acetate, a type of plastic used in the production of clothing, is also made from wood pulp.
Specialty Products
- Food Additives: Wood pulp is used as a food additive, primarily as a thickener and stabilizer in processed foods such as ice cream, salad dressing, and sauces.
- Chemicals: Wood pulp is also used in the production of various chemicals, including ethanol, acetic acid, and carbon disulfide.
Energy Production
- Biomass: Wood pulp can be used as a biomass fuel in the production of energy, including electricity and heat.
Overall, the versatility of wood pulp as a raw material makes it a vital component in various industries, and its applications continue to expand as technology advances.
Current situation of wood pulp for papermaking
Since the wood pulp is basically wood that has been treated and processed in order to create a usable raw material for different types of paper goods, its range of applications is very broad. This has led to an increased demand for wood pulp over the years. In order to meet the demand, some companies are actively cultivating large areas of land and planting trees that can be harvested. In addition to the felled trees, the pulp waste generated in the manufacturing process is also often recycled to produce new wood pulp. This not only helps reduce the need to cut more trees but also prevents pulp waste from eventually entering landfills.