Agriculture and Environment: Wood Pulp
Environmental Impacts of Production: Pollution from Processing Mills
No attempt will be made to address the full range of environmental impacts of pulp mills.
Much is already known about this form f industrial pollution. However, since pulp processing mills are increasingly part of pulp plantations, it is important that their most significant impacts are mentioned here.
Pulp mills produce effluents that are high in solids, nitrogen, phosphorous, and organic compounds. In Europe the effluent released from pulp and paper mills has seen a reduction in its biochemical oxygen demand (BOD, a measure of pollution) by more than 70% since 1990.
In Europe some 95% of pulp and paper mill effluents receive primary and secondary wastewater treatment (Confederation of European Paper Industries 2000). While there are improved methods for treating effluents, they have not been uniformly adopted or enforced through government regulations throughout the world.
In addition to organic matter and other natural substances in the effluent, in many places high quantities of chlorine are used to bleach pulp to a uniform colour as well as to improve binding, printability, and reproduction capacity; increase strength; and reduce yellowing over time. There is currently a shift away from chlorine gas in favour of other bleaching techniques such as chlorine dioxide and ozone, but this is not true everywhere.
Air pollution has also been a problem of paper mills. The use of lower-quality fuel sources in the past caused major emissions from pulp mills, including carbon dioxide, sulphur dioxide, nitrogen oxides, and particulate matter. Sulphur emissions also occur as a result of the pulping process itself.
Sulphur dioxide has bee reduced by switching from heavy fuel oil to sulphur-free and low-sulphur fuels, replacing fuel oil with natural gas, or controlling the production process more carefully. In addition, the use of natural gas produces less carbon dioxide than the fuel sources used previously (Confederation of European Paper Industries 2000).
The amount of water used in pulp and paper mills varies depending on the quality of the paper or paperboard produced as well as the size of the paper machine. In Western Europe the paper industry uses, on average, about 35 cubic meters of water per metric ton of pulp produced. However, the amount of water used can exceed 100 cubic meters per metric ton for high-quality grades of paper (Confederation of European Paper Industries 2000).
