ECF: A High Quality, Pollution-Free Alternative to Chlorine Bleaching
by Doug Pryke
Print & Graphics Magazine*
Most people in the printing, publishing, and graphic arts industries have developed their own preferences for paper quality and characteristics. What many people may not be aware of is the process involved in producing that product and the environmental effects of those processes.
Fifteen years ago, the concept of using recycled pulp was beginning to catch on. Some people said it was simply a passing fancy, or a marketing gimmick. But, as users came to understand the importance of reusing resources, recycling became the norm. In fact, today the recycled content symbol is far from exotic - it's expected.
A new buzzwordNow everyone in the industry - the producers, distributors, and even the end users - find themselves in the midst of a new debate. The chlorine debate.
There are those who have called for a ban on chlorine and its use as an industrial feedstock. What many people don't know is that there is an alternative to chlorine bleaching in the manufacture of pulp, the raw material of paper.
ECF (Elemental Chlorine-Free) processes, based on chlorine dioxide, provide an environmentally superior product, without sacrificing product quality.
Most people would agree that there is a clear and urgent need to eliminate persistant, bio-accumulative, toxic substances from mill waste water resulting from the pulp bleaching processes. The conversion to chlorine dioxide in the first stage of chemical pulp bleaching has addressed, and virtually eliminated, these priority pollutants, including dioxin, from the bleaching process.
New science, a proven environmental track record, and strong market demand demonstrate that ECF is without rival in terms of pollution prevention, resource conservation, and product quality.
ECF basicsTo fully understand both the environmental benefits and the improvements in product quality resulting from the use of chlorine dioxide, we must first understand the fundamental chemistry behind the process.
In chemistry, a single atom can make a world of difference. The chlorine dioxide molecule consists of one chlorine atom and two oxygen atoms. As such, chlorine dioxide's chemical properties are very different from those of elemental chlorine and they yield very different results.
During the pulp bleaching process, both chlorine and chlorine dioxide can form chlorinated organics. However, whereas chlorine tends to combine with lignin - the substance that holds the wood fibers together - chlorine dioxide typically breaks apart the lignin.
Any remaining chlorinated organics formed by chlorine dioxide bleaching are water soluble and non bio-accumulative. In fact, they are similar to chemical substances occurring naturally in the environment.
Comlementing its strength is its selectivity. Chlorine dioxide attacks lignin and other substances, such as resins, while preserving the wood's cellulose fibers - those that provide the strength in the final products.
These properties have made chlorine dioxide the fastest growing and most effective bleaching agent in the manufacture of pulp, the raw material used in the production of paper and paper products.
ECF pulp quality is excellent. Studies show that ECF bleached produtcts can achieve high brightness (89-90% ISO), and high strength (burst, tear, tensile, viscosity). Other bleaching processes are less selective and have not been able to retain high strength at full brightness.
A number of recent studies have shown that other processes, including Totally Chlorine-Free (TCF), may actually reduce the fiber strength and the tear strength at full brightness by approximately 10%. A low fibre strength may limit recyclability. TCF processes have lower yield - more wood is required to make the same amount of paper - thereby increasing the strain on precious forest resources.
In addition to product qualtiy, a great deal of attention has been focused on the environmental benefits of chlorine dioxide bleaching. In fact, as a result of ECF processes, dioxin discharges from pulp and paper mills to waterways in North America decreased aby 96% from 1988 to 1994.
Signs of progressTwo measures of ECF's success - virtual elimination of dioxin and eco-system recovery - are documented by declining body burdens of dioxin in fish and the subsequent lifting of fish advisories for dioxin throughout North America, downstream of pulp and paper mills.
In the United States, 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.
U.S. fish comsumption advisories are based on factors such as contamination levels of specific target chemicals, which include, among others, dioxin, mercury, PCBs (polychlorinate biphenols), and verious pesticides. As such, advisories are one indicator of the environmental status of a particulat aquatic eco-system. Removing or partially rescinding a fish consumption advisory or ban generally signals positive change in the aqutic eco-system under study.
An analysis of the August 1995 EPA's National Listing of Fish Consumption Advisories (NLFCA) reveals that the small number of water bodies under a dioxin advisory is steadily diminishing. Since 1990, 13 states have lifted a total of 17 dioxin advisories from water bodies downstream of U.S. pulp mills.
Moreover, EPA has analyzed the remaining dioxin advisories downstream of U.S. pulp mills against its Best Available Technology (BAT) criteria, currently based on ECF proceses. The study showed that, following implementation of the proposed guidelines, all remaining dioxin advisories downstream of pulp mills would be lifted.
Product quality, combined with a strong environmental performance, has made ECF pulp one of the fastest growing segments in the North American bleached chemical pulp (BCP) market. U.S. ECF pulp production has increased by more than 1,600% since 1990. It now holds more than 30% of the U.S. BCP market. Likewise, in Canada, production of ECF pulp was expected to reach 6.6 million tons by the end of 1995, totaling 60% of all Canadian bleached chemical pulp production (see Figure 1).
Because of the rapid growth of ECF production, one group has based its guidelines for the purchase of enviornmentally preferable paper products on the merits of chlorine dioxide.
In December, the Environmental Defense Fund (EF) released a project synopsis highlighting the results of its Paper Task Force Report. Notably, the ECF report recognized that "Bleached kraft pulp mills have reduced releases of dioxin over 90% since 1988." The Task Force also identified chlorine dioxide as a pollution prevention technology and recommended its use in chemical pulp bleaching.
With results like these, superior environmental performance and product quality in nearly every world market.
*Used with permission from Print & Graphics Magazine.