Pulp and paper mills
Pulp and paper mills are industrial facilities where raw materials, primarily wood, cotton, hemp, and flax, are processed to manufacture paper. This involves breaking down vegetable matter into a liquid slurry, removing excess liquid, and forming the remaining fibers into a mat. While these mills play a significant role in the global economy, their operations can lead to serious environmental challenges, such as the generation of noxious odors, toxic solid wastes, and polluted effluents. A widely used method, the kraft process, involves chemical treatments to separate cellulose fibers from lignin, but it can produce harmful compounds known as adsorbable organic halogens (AOX), which are linked to various health risks, including cancer.
Environmental standards have been established in several countries to regulate AOX emissions, with some experts advocating for zero emissions. Efforts to mitigate environmental impacts include exploring alternatives such as closed-loop systems and oxygen-based bleaching processes, which are less harmful than traditional methods. Beyond chemical pollution, pulp and paper mills also contribute to deforestation and habitat destruction, raising concerns about biodiversity loss and the well-being of local communities. Overall, while pulp and paper mills are essential for paper production, they pose significant environmental and health challenges that require ongoing management and innovation.
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Pulp and paper mills
DEFINITION: Operations where raw materials are processed for the manufacture of paper
The chemicals used in the primary industrial processes in pulp and paper mills present multiple environmental problems, including noxious odors, potentially toxic solid wastes, and polluted effluents.
The pulp and paper industries constitute an important segment of the world’s economy. In the manufacture of paper, vegetable matter is reduced to a liquid slurry, excess liquid is removed from this pulp, and the remaining fibers are formed into a mat. Materials used to produce paper include wood, cotton, hemp, and flax, depending on the desired product, but all require similar processing involving large amounts of water. Most kinds of paper contain at least a portion of wood, and if wood is used, the cellulose fibers in the wood that can be formed into paper must be separated from the lignin that surrounds them. Once the fibers are successfully separated, the resulting pulp mat may require bleaching to produce a paper that is sufficiently white for commercial use.
All the processes involved in the manufacturing of pulp and paper present potential environmental hazards, but the kraft process—the process used to reduce wood fibers to pulp—may present the greatest dangers. Prior to the invention of the kraft process, pulp mills used mechanical methods to crush plant matter and used rags to separate the unwanted material from the fibers necessary to make paper. The from such mills was often dirty and thus posed some hazards to the environment, but because the processes used were mechanical rather than chemical, no new chemical compounds were formed.
AOX Compounds
In contrast with mechanical methods, the kraft process uses chemicals to break down the lignins in wood. Industry experts report that more than 70 percent of the world’s pulp is produced using the kraft process. Well into the late twentieth century, many pulp and paper mills discharged untreated wastewaters from the pulping and bleaching processes directly into rivers and lakes. While the kraft process has allowed production of paper from woods once considerable unsuitable for paper, the resulting pulp is generally more difficult to bleach than pulps produced using other methods. The preferred bleaching agent has been chlorine dioxide, an acid that reacts easily with the residual lignin compounds in the pulp to form chlorinated compounds. Scientists refer to such compounds as adsorbable organic halogens (AOX), while the general public more commonly knows them as organochlorines and dioxins.
Researchers have shown that many of these compounds have mutagenic and carcinogenic properties; that is, excessive may lead to birth defects, reproductive difficulties, and some forms of cancer. AOX compounds pose special threats because many accumulate in the fatty tissues of animals rather than passing through the body, and therefore they tend to become concentrated as they move up the (a process known as biomagnification). Residents of the Great Lakes region of the United States, particularly children and women of childbearing age, have been advised to limit their consumption of lake trout, a fish that is known to have high concentrations of AOX in its fat.
Because of the environmental dangers associated with organochlorines, many countries, including the United States, have implemented AOX emissions standards. Some experts believe that the only acceptable standard would be zero of AOX emissions. While some pulp and paper manufacturers have argued that achieving zero emissions would be prohibitively expensive, particularly if they are forced to modify existing mills, others have explored alternative manufacturing techniques, such as the use of closed-loop mills. In a closed-loop facility, no liquid leaves the factory. Effluents are treated on-site and cycled back through the system. Another option is conversion to oxygen bleaching, or totally chlorine-free (TCF) bleaching. Mills in European countries that converted to TCF bleaching found that their operating costs were actually lower than with previously used chlorine processes. In addition to posing less of a threat to the environment, oxygen-based bleaching compounds are less corrosive. This means that the equipment within a mill lasts significantly longer before requiring replacement.
Other Environmental Harms
In addition to the well-publicized hazards of AOX, pulp and paper mills present a number of other environmental problems. People living near pulp mills often complain about noxious odors. Strong odors are often a of the chemical digesting process used in pulping wood, but to date researchers have been unable to find any harmful effects of these odors other than psychological discomfort and, thus, lowered quality of life for those exposed. The solid wastes produced by mills may also have negative impacts on the environment. The exact composition of these wastes may be difficult to determine, particularly when mills use recycled materials. Most pulp and paper mills routinely use the waste and liquids from the digester as boiler fuel for steam turbines to generate electricity. This reduces the volume of potential but cannot completely eliminate it. The industry attempts to recycle as much of the solid waste from mills as possible, but optimum efficiency has yet to be achieved in this area.
The world’s ever-growing appetite for paper means that hundreds of thousands of hectares of forest are harvested annually to be processed into pulp. In addition to the obvious environmental harms of deforestation, possible erosion, and destruction of unique ecosystems and wildlife habitat, harvesting exposes timber industry workers and the general public to dust, debris, and exhaust fumes from logging equipment.
Bibliography
Allott, Joseph, Felix Grunewald, and Ludwig Luyeye. "Responding to Productivity Improvement Challenges in Pulp and Paper." McKinsey & Company, 16 May 2023, www.mckinsey.com/industries/packaging-and-paper/our-insights/responding-to-productivity-improvement-challenges-in-pulp-and-paper. Accessed 22 July 2024.
Clay, Jason. “Wood Pulp.” In World Agriculture and the Environment: A Commodity-by-Commodity Guide to Impacts and Practices. Washington, D.C.: Island Press, 2004.
Henttonen, Ville. "How European Pulp and Paper Mills Adapted to the New Energy Transition Reality." Fastmarkets, 11 May 2023, www.fastmarkets.com/insights/how-european-pulp-and-paper-mills-adapted-to-energy-transition/. Accessed 22 July 2024.
Miller, G. Tyler, Jr., and Scott Spoolman. Living in the Environment: Principles, Connections, and Solutions. 16th ed. Belmont, Calif.: Brooks/Cole, 2009.
Rodd, Tony, and Jennifer Stackhouse. Trees: A Visual Guide. Berkeley: University of California Press, 2008.
Wright, David A., and Pamela Welbourn. Environmental Toxicology. New York: Cambridge University Press, 2002.