Volume 1, Number 3
Oct 1994

Getting Away from Chlorine Won't be Easy, but Enzymes will Help

"Chlorine-Free Paper is Clean but Unpopular," an article by Timothy Aeppel in the April 4 Wall Street Journal, sums it up pretty well. Chlorine-free paper is hard to sell in this country. Louisiana-Pacific Corp. switched to totally chlorine free (TCF) bleaching after being sued in U.S. District Court by a group of surfers and the EPA, and made to pay a $2.9 million fine. L-P lost heavily from its investment in the new bleaching process, and had to halt production at its west coast Samoa mill for about four months this past spring in order to clear out its inventory. Part of the problem is that the public now wants recycled paper instead. (Recycled paper cannot ordinarily be TCF, because there is no way to tell whether the fiber of the furnish was originally made in a TCF mill.)

TCF pulp is more expensive to produce, but L-P has been offering it at the same price as chlorine-bleached pulp in order to establish a market.

The irony of it all is that nobody really needs TCF pulp, because dioxin emissions can be reduced to undetectable levels by increasing the level of chlorine dioxide and decreasing or eliminating elemental chlorine in the bleaching process. Pulp made without chlorine gas this way is called "elemental chlorine free" or ECF.

This argument was presented to the EPA at a public hearing in February on the agency's cluster rule on air and water emission standards for the paper industry. The Alliance for Environmental Technology (AET), a trade group that was the first to use EPA's Framework for Ecological Risk Assessment, presented a report entitled "Review and Assessment of Ecological Risks of Bleaching with Chlorine Dioxide." (For more information call AET at 519/855-4979, fax 855-4313).

States have been considering bills to encourage the purchase of TCF paper (i.e., paper made from pulp that was made without chlorine or chlorine compounds--not paper that is free of chlorine). However, none of them have passed these bills, partly because the supply of TCF paper is so small, and partly because it is so expensive, as much as 58% higher than ordinary paper. The supply of ECF paper is much larger. (More information on this topic in Recycled Paper News for March and May.)

One development that will lessen papermakers' reliance on chlorine is the use of enzymes. A possible breakthrough with enzyme bleaching was reported at the annual Non Chlorine Bleaching Conference in Florida in March. A German company named Lignozym has developed a laccase enzyme that can lower the kappa number of pulp over 20 points without degrading the cellulose. (Hawley's Condensed Chemical Dictionary says that laccase is an enzyme, found in the latex of the lac tree, in potatoes, sugar beets, apples, cabbages and other plants, which oxidizes phenols to ortho- and para-quinones. By "lac" it probably meant "lacquer," because there is a lac insect and a lacquer tree but no lac tree.)

H.P. Hall was the Lignozym representative who read the paper. He said the process is carried out at 40° to 50°C, pH 4-5, and pressures from atmospheric to 10 bars. Capital cost is low, and operating costs similar to those of chlorine dioxide. More information is in the conference report, "A Bleaching Revolution is in Progress," by Neil McCubbin, Pulp & Paper Canada 95:4, 1994, p. 12, 14-16. Author McCubbin says on p. 16 that "Hall's presentation at the NCB conference was a complete surprise to most attendees.... If mill scale trials are as successful as the laboratory work described by Hall it will probably be the most significant new pulping technology of the 1990s."

The significance of all this for permanence of paper is that bleaching not only whitens paper, but it removes lignin and other impurities from the pulp before it is made into paper, thus continuing the work begun by the pulping operation. As McCubbin says, "It is becoming evident that modern pulping and bleaching processes are now so closely allied that the past practice of considering them as separate mill departments may have to be modified."

If bleaching is done carefully by methods that do not involve chlorine, permanence may not be affected; but if it is skipped altogether, in order to advertise the TCF aspects by the brown color of the paper, permanence will be jeopardized.