North American pulp mills' discharge of dioxin (rhymes with toxin) from use of elemental chlorine in bleaching has been cut in half during the last two years, and will decline to undetectable or virtually undetectable levels in a few more years because of strict regulation in both Canada and the U.S. The decline in Europe is probably similar, although other countries' regulations are not as strict as ours are.
The other two forms of chlorine used in bleaching, chlorine dioxide and sodium hypochlorite, have not been implicated in dioxin formation. Nevertheless, pressure from consumers (who may know only that bleaching generates a pollutant, or that chlorine is somehow associated with dioxin) has already made brown (unbleached) paper popular in Sweden and California, and will probably do the same for papers made of "chlorine-free" pulp, soon to appear on the market in white or off-white papers.
The effects of these developments on permanence of paper are both bad and good. Brown paper may be environmentally friendly, but it is not posterity-friendly, because pulp must be fully bleached to be chemically stable and long-lived. On the other hand, alternate bleaching methods are now being adopted that are kinder to both the fiber and the environment, and it is high time they were given a chance to show what they can do. If reports of pilot plants, research and proposed pulp mills are any indication, they will get that chance.
A report of a Russian method for making sulfur-free and chlorine-free pulp in the December 1989 Pulp & Paper International was picked up by the March Paper Conservation News a British newsletter) and copied from there by the Canadian Bookbinders and Book Artists Guild Newsletter, so interest in the topic seems to be pretty widespread. The method, now being used in a 5-ton/day pilot plant near Leningrad, uses the following bleaching sequence: hydrogen peroxide in acid conditions, oxygen-alkali bleaching, and hydrogen peroxide in alkaline conditions. In the oxygen-akali bleaching step, the oxygen is bubbled up through a tower containing the wood chips and an alkaline liquor, which may be sodium hydroxide, sodium carbonate or ammonium hydroxide, or another alkali; they are still testing.
Elimination of sulfur will take away the usual pulp-mill smell of mercaptans and sulfur compounds, and elimination of chlorine will eliminate production of dioxins. Pulp yield is increased, capital costs are lower, and the effluent is much cleaner in general. The PPI article apparently gave no information on pulp brightness.
A Repap Enterprises pilot plant in Newcastle, New Brunswick, has been making 20 tons/day of chlorine-free hardwood pulp since February 1989. It uses the Alcell process for pulping, based on ethanol. Details of the bleaching process are not gives in the July Pulp & Paper article on Repap, but the brightness of the paper is given as 80.
Hanover Papier in Alfeld, West Germany is making papers Of "100% chlorine-free" pulp, which are dioxin-free and yellowish-white. Most of the mill's production is coated paper.
Perhaps that pulp comes from a company called Technocell in Europe, which has a pulping technology based on methanol that is competitive with Repap's Alcell process. But it may come from a source that is further along in development, because Technocell is still in the pilot plant stage.
In this country, a new company, Michigan Pulp and paper Corporation, proposes building a mill to make sulfur-free, chlorine-free market pulp. According to the June Pulp & Paper, it would use oxygen delignification and peroxide bleaching. The president and CEO is Richard Valley, former chair of the Department of Paper Science and Engineering at Western Michigan University.
The DuPont Company, a major supplier of chemicals and services to the paper industry, is working with Georgia Tech on projects concerning chlorine-free bleaching of pulp, according to the February 1989 Pulp & Paper. This is in connection with DuPont's great interest in the potential of cal pulp as an all-purpose market pulp.