Pulp and Paper Industry

Pulp is the fibrous material found in paper. While pulp can be made from diverse materials such as cloth rags, hemp, and straw, tree pulp remains the most popular. Trees of small diameters, tree limbs or crowns, or waste from lumber manufacturing are often pulped. Recovered wastepaper has gained importance in recent years. Electronic substitution for print materials has led to some reduction in paper demand, although new product lines also emerge for pulp. For example, fluff pulp is used in baby diapers and other highly absorbent products.

During wood pulping cellulose is separated from lignin, a natural polymer, which bonds the cellulose fibers together to create structure in trees. Mechanical, chemical, or chemi-thermomechanical pulping processes are most often used. The process chosen depends on the final product or paper grade that is desired and the input material. Hardwoods may [Page 1451]be too dense for mechanical pulping. Softwoods are preferred for paper due to their long, slender fibers, which provide strength in paper products. Virgin pulp is often mixed with mill residues, such as saw chips or sawdust.

Pulp mills are often located adjacent to water bodies; their toxic by-products may bioaccumulate in nearby fish.

Pulping produces significant chemical and biological waste. Breaking down wood chips through grinding requires significant energy input. Some comes from fossil fuels, although mills can burn by-products to produce a portion of the energy required for processing. Chemicals, such as sulfite and sulfate (kraft), can dissolve lignin in heated “digesters,” but a variety of hazardous air pollutants are released. The recovery of the chemicals to be reused is usually viewed favorably, yet it generates additional emissions. Chemical pulping also produces tons of solid waste, made up of lignin and wood fibers, for every ton of pulp created.

If white paper is desired, bleaching occurs. Vents from bleaching tanks emit air pollutants. Nonchlorinated bleaching agents are available, but they are less popular. Highly toxic elemental chlorine has been phased out in most mills and replaced with chlorine dioxide, but bleaching processes still generate a large volume of liquid waste with toxic chemicals such as dioxins, furans, and chlorinated organics. Some of these pollutants pass though treatment plants and are discharged into water supplies. Mills are often located adjacent to water bodies given their high utilization of water.

There is technical capacity to build efficient mills that have no liquid discharge and recycle their chemical input, but they are expensive. Traditional mills release large quantities of by-products such as volatile organic compounds, particulate matter, and carcinogens. Bioaccumulation of absorbable organic halides often occurs in nearby fish populations. Environmental standards are often based on fish mortality during brief exposure to wastewater. Environmental advocacy groups argue that such tests are insufficient because they do not look at extended exposure over time or the potential for compounded results after mixing occurs with other toxins in the surrounding ecosystem.

The pulp industry is very capital intensive. Current economic returns are poor when compared to a decade ago. Dozens of mills in North America and Western Europe have shut down since 2000. Consolidations of plants owned by the same company, as well as merging between pulp giants, have become common. However, the world's largest pulp and paper companies are still found in the United States, Finland, and Japan.

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