Cellulose pulp, production volume

Main commercial sources of cellulose are wood and, to a lesser extent, cotton. To isolate the cellulose the feedstocks are boiled in boilers under pressure in the presence of caustic soda (soda process), mixture of sodium hydroxide with sodium sulfide (Kraft process) or sulfurous acid and salts thereof (sulfite process) as a result, lignin and hemicelluloses are removed, while cellulose is separated, washed, and dried (Sjostrom et al., 1993). Production volume of wood pulp in the world is huge and reaches 250-300 million tons per year. Production of cotton cellulose is smaller, 20-25 million tons per year. The main part of the cotton fibers is intended for textile industry, and only short fibers and wastes are used for the production of special papers, microciystalline cellulose and cellulose derivatives. 

Bleaching — When the desired quality of the final product requires bleaching of pulp recovered from wood, it is usually done by the addition of oxidizing chemicals, such as chlorine, chlorine compounds, peroxides, and hydrosulfites. The oxidizing chemicals react with the non-cellulose porticm of the pulp, rendering it soluble in water or in alkaline solutions. As a result, the bleaching step adds to the wastewater volume and pollutant loading. 

The great importance of manufactured fibers in the chemical industry and in the overall economy of the United States becomes apparent when the volume of production of these materials is considered and compared with the market value of even the least expensive of the raw materials used by them. The amounts of oil and natural gas consumed by the manufactured fiber industry represent around one percent of national annual usage. Of this amount, about one-half is used to produce raw materials from petrochemicals, with the other half used for energy to convert trees to wood pulp for cellulose-based fibers and to convert the wood pulp and petrochemical-derived raw materials to fibers. 

The amount of total biomass annually produced of which c. is the predominant part is roughly equal to all known resources of petroleum and natural gas. Thus, c. is available in abundance and reproduced constantly, in contrast to the fossil sources. Only a few sources consist of pure cellulose (called a-c.) e.g., the hairs of cotton seeds (better than 90%). The large-volume source of c. is wood (40-50%), mainly from pine trees. C. has to be separated from its by-products (- lignin, - hemicellu-lose) by a pulping process. Mechanical pulping yields a material that is used in papermaking. For chemical utilization content of more than 90% a-cellulose is necessary and can be obtained only by chemical pulping (- paper) or by the use of linters. 

The largest volume of cellulose, after partial removal of noncellulosic material, goes into paper, paperboard and nonwovens (150 x 10 mt/a). The long hairs of cotton are used in textile applications (15 X 10 mt/a). Only 7 x 10 mt/a is used in the form of high a-cellulose wood pulp or Enters for the production of regenerated fibers (-+viscose) or films (- cellophane) and for the manufacture of c. derivatives, especially esters and ethers. 

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