![]() During the cooking process, approximately half of the wood dissolves. Cooking the wood chips in the presence of sodium hydroxide and sulfide liquor under high pressure removes the lignin and separates the wood into cellulose fibers. Softwood’s long fibers contribute to the strength of the material it is used for. Softwood fibers are longer than hardwood fibers and thus softwood pulp is called long fiber pulp, whereas hardwood pulp is short fiber pulp. Softwood consists mostly of cellulose and lignin, and it contains less hemicellulose than hardwood. While the raw material affects significantly the properties of the end-product, the process for both hardwood and softwood is nearly identical, the only difference being the structure of the wood. The bark of the trees is used for bioenergy production at the mill. Wood is first debarked and cut into small chips for more efficient pulping. The paper pulp production process can be divided roughly into three stages: wood handling, fiber processing, and drying and packaging. Moreover, paper pulp manufactured from softwood can generate valuable by-products and production residues such as lignin, turpentine, and tall oil which can be further processed to innovative products. The paper pulp production process is more than energy self-sufficient generating wood-based bioenergy for the national electricity grids. Alternatively, it will be dried and pressed into bales ready for use as a raw material in paper mills worldwide. The paper pulp will be fed directly to paper pulper machines in integrated paper mills. The paper pulp is then ready to be used directly for natural paper manufacturing or it can be bleached for bleached white paper manufacturing. The water is then pressed out and the residue is dried. The fibers are then washed and screened to remove any remaining fiber bundles. The pulping process produces a large number of individual fibers. No matter which pulping method is used, the material must be broken down into its constituent elements in order to separate the fibers. Today, the most commonly used pulp making methods are chemical pulping, chemi-mechanical pulping, and mechanical pulping. Modern pulp production is based on the best available technologies and concepts, creating more products with less raw materials, water, energy, and environmental impact. No matter which material is used for papermaking, the first step is always to dissolve the material into pulp. Paper is actually a multi-functional biomass product, which can be made of renewable woods, grass, rags, waste paper, and other materials.
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