pulp industry was the second largest user of chlorine, taking 1.5 MMT, or 14 percent, of total U.S. chlorine output (United States Bureau of Mines, 1989, p. 849). In 1988, the U.S. pulp and paper industry consumed 2.3 MMT of caustic soda, or 24 percent of production (United States Bureau of Mines, 1989, p. 849). It also consumed 0.341 MMT of sodium chloride (salt) (United States Bureau of Mines, 1989, table 18). The other chemical used in large quantities is sodium chlorate. Production of this compound in 1974 was reported to be 0.19 MMT, of which 70 percent was used for pulp bleaching (Lowenheim and Moran, 1975). U.S. production in 1988 was 0.242 MMT, and consumption was probably somewhat higher, thanks to imports. The 70 percent share attributable to pulp bleaching in 1974 is probably a minimum for 1988.17 On this basis, we estimate that 1988 consumption of sodium chlorate by the pulp sector was at least 0.2 MMT.
The chemicals described above (total weight 7 MMT) were not embodied in the final product and so must be counted as part of the production waste stream. It follows from materials-balance considerations that the annual discharges of chemical wastes from the pulp and paper industry must be roughly equal to the annual inputs, element by element. As it happens, annual "dry" wastes (e.g., sludges) were reported to be 7.7 MMT in the early 1980s (Science Applications International Corporation, 1985). This is much smaller than our estimate of 16 MMT (bone-dry) in losses from primary pulping and bleaching. However, our figures are more plausible because they include not only chemicals (7 MMT) but ash (approximately 1.5 MMT) and some fiber. They are also consistent with mass balance.
Bleaching wastes are mostly 90 percent sodium chloride, but an estimated 10 percent of the chlorine used is chemically bound to lignins and other organic materials in the pulp. This material constitutes a significant part of the process waste. Roughly 6 percent of the mass of the raw pulp is lost during bleaching. The bleaching effluent contains significant quantities of chlorinated organic compounds with very high molecular weights. In fact, 70-95 percent of spent chlorination and alkali extraction liquors have molecular weights greater than 1,000. Such compounds cannot be separated, quantified, or identified by present means. However, measurable traces of dioxins and furans are found among these wastes (Holmbom, 1991).
Kraft-process emissions of greatest environmental concern are noncondensible sulfur-containing gases (hydrogen sulfide, methyl and ethyl mercaptans, dimethyl sulfide, etc.). These are generated at the rate of about 2.5 kg/ton of pulp (International Bank for Reconstruction and Development, 1980). For sulfate pulp in toto, uncontrolled emissions of sulfur-containing gases would have been about 0.1 MMT. The EPA has estimated airborne effluents (excluding CO2) from the sector to be about 1.15 MMT (United States Environmental Protection Agency, 1991).
A partial list of chemicals used in the paper industry (as opposed to pulping) and embodied in the product includes clay (kaolin) for filling and coating, titanium dioxide for whiteness, and aluminum sulfate (alum) to improve the ink-