Costs and Benefits of Various Pollution Prevention Technologies in Kraft Pulp Industry

K raft pulp is manufactured in the United States from nearly all commercially availble wood species. About 55 million tons per year are manufactured, 30 million of which are bleached and used mostly for printing and office papers and tissue products. Some kraft pulp is exported, and significant quantities are imported, mostly from Canada and South America. Pulps manufact'xed by sulfite, mechanical, and deinking processes are being used to a modest but increasing extent to replace bleached kraft pulp in certain markets. The manufaqure of bleached kraft pulp is a major but not dominant source of water pollution in the pulp and paper industry. With respect to pollution prevention measures, bleached kraft mills in the United States range from the best in the world to about average, compared with the other pulp producing countries. The characteristics of mill effluent discharged in this country are probably somewhat better than average, since 97 percent of our bleached kraft mills have secondary effluent treatment. In other pulp producing countries, from 50 to 100 percent of mills have secondary treatment. This paper discusses only the manufacture .of paper grade bleached kraft pulp, for market or for on-site use in an integrated paper mill. The International System of units (SI, Systeme International) is used throughout, unless otherwise noted. Environmentalists have focused their attention on the kraft pulp bleaching processes because so many of the most widely known, persistent pollutants discharged by the pulp and paper industry originate in that part of pulp manufacture. But the prebleaching pulping processes are also significant, andmany measures that reduce or prevent the formation of pollutants in the bleach plant are implemented upstream in the pulping operations.