Chlorine Dioxide Is Increasingly A Substitute for Chlorine In Pulp and Paper Industry
Environmental Science and Engineering*
Following the identification, in the late 1980s, of trace levels of dioxin (2,3,7,8-TCDD), an inadvertent by-product of the prevailing chemical pulp bleaching process, the pulp and paper industry moved quickly and voluntarily to implement a comprehensive, multi-faceted strategy to virtually eliminate dioxin. By applying the principles of pollution prevention-process changes, product reformulation, and raw material substitution-the industry, in a remarkably short time, has achieved success in virtually eliminating dioxin from mill waste water.
One key component of the industry's virtual elimination strategy has been the increased substitution of chlorine dioxide for chlorine in the first stage of chemical pulp bleaching, a process change that has become known as Elemental Chlorine-Free (ECF).
Now, new science, a proven environmental track record, and strong market demand together document ECF's successful application as a pollution prevention process.
ECF pulp quality is excellent. Studies show that ECF bleached products can achieve high brightness (89-90% ISO), and high strength (burst, tear, tensile, viscosity). Other bleaching processes are less selective and consequently have not been able to retain high strength at full brightness.
In addition to product quality, a great deal of attention has been focused on the environmental benefits of chlorine dioxide bleaching. As a result of ECF processes, throughout North America dioxin discharges from pulp and paper mills to waterways have decreased by 96% over the period 1988-1994.
In both Canada and the U.S., fish consumption advisories have been-and continue to be-lifted as dioxin levels in fish downstream of pulp mills decline. These indicators of progress and broader eco-system integrity document the success of the pulp and paper industry's use of chlorine dioxide.
The recovery of coastal fisheries in British Columbia are an example of the progress made by the pulp and paper industry after the implementation of chlorine dioxide. In October, 1996, together Environment Canada and Health Canada published the "Chlorinated Substances Action Plan: Progress Report." The report documented the re-opening of approximately 46 percent of coastal fisheries that had previously been closed due to dioxin contamination. Similarly, the waterbodies of the United States also showcase this broader eco-system recovery and environmental improvement. According to both EPA and state environmental and health authority data, since 1990, 13 states have lifted a total of 17 dioxin advisories from waterbodies downstream of U.S. pulp mills-a decline of more than 50 percent.
Product quality, combined with a strong environmental performance has made ECF pulp the fastest growing segment in the world bleached chemical pulp (BCP) market. In 1997, ECF manufacture is expected to reach 38 million tonnes per year, for a world market share of 50 percent. In all major pulp producing regions of the world, ECF demand is rising rapidly.
North American trends paint a very similar picture. In Canada, ECF pulp production has increased more than 900% since 1990. It now holds more than 70% of the Canadian bleached chemical pulp market. Likewise, in the U.S., production of ECF pulp is expected to reach 13 million tonnes by the end of 1997, totaling 47% of all U.S. bleached chemical pulp production
As research and technological development continues, the pulp and paper industry is moving into an era of beyond compliance. Many believe that future prospects for continued progress are bright, including a shift toward the research and development of minimum-impact mills. For bleached chemical pulp mills, development will be progressive, but emerging research suggests that ECF processes may serve as the foundation for the industry's future successes.