around 74.9 MMT in 1988. Adding 5 MMT of fillers and other chemicals14 and subtracting 4.9 MMT for internal recycling implies that domestic output of paper and paper products that year was 75.1 MMT.

United Nations data for pulp are subdivided by pulping process (United Nations Statistical Office, 1988). Mechanically produced pulp (5.39 MMT) was virtually entirely used for newsprint, of which domestic production was 5.36 MMT. The other pulp types were, in decreasing order of quantity, sulfate or Kraft pulp (43.53 MMT), semichemical pulp (3.95 MMT), and sulfite pulp (1.415 MMT). Dissolving-grade pulp for chemical use (e.g., in rayon manufacturing) amounted to 1.24 MMT. Again, there is a discrepancy between U.N. and U.S. statistics.

The 142.6 MMT of pulping feeds contained around 21 MMT, or 15 percent, moisture. The 57.9 MMT of pulp output included only 5.8 MMT, or 10 percent, moisture. Overall, then, the apparent mass disappearance between pulpwood and pulp in 1988 was 92.2 MMT, of which 15.2 MMT (21 - 5.8) was presumably water. This would have left 77 MMT bone-dry weight of waste, including ash and chemicals. The bone-dry organic wastes (70 MMT) consisted of lignin, hemicelluloses, and resins. Small amounts of lignin were recovered for use as lignosulfonates; virtually none of the hemicelluloses were recovered for chemical use.15

Most of the waste organic material was burned on site to recover energy and chemicals. We do not have data for 1988, but in 1991, the American Forest and Paper Association (AFPA) estimated that 75.3 MMT of the dry waste organic material content of "black liquor" was used as fuel.16 The energy recycling figure in 1988 was presumably about 2.5 MMT smaller, or 72.8 MMT, based on relative pulp production levels. The AFPA numbers are as close to ours as can reasonably be expected, given the approximations made in our calculation.

All of the pulping processes except the mechanical ones use chemical reagents, notably sodium hydroxide or sulfurous acid, to dissolve the lignin and separate it from the cellulose fibers in the wood. In principle, these chemical reagents are mostly recovered and recycled internally. In practice, of course, recovery is incomplete and some makeup chemicals are required. In fact, makeup requirements and imputed overall losses and wastes are quite considerable.

The sodium sulfate consumed by the U.S. pulp and paper sector in 1988 was 0.48 MMT (Bureau of Mines, 1989, tables 3-5, 12). Similarly, soda ash consumed by the sector was 0.11 MMT. The total elemental sulfur actually consumed was 0.008 MMT. Consumption of lime by the sector was 1.14 MMT. The industry consumed 0.856 MMT of sulfuric acid. Most of these chemicals appear to have been used in pulping.

Other chemical inputs to the pulp and paper industry were used primarily in bleaching. Most virgin chemical pulps for paper are bleached. In 1988, the primary bleaching agents were elemental chlorine (Cl2), caustic soda, and chlorine dioxide. The latter is manufactured in-house from sodium chlorate, because chlorine dioxide is explosive and too dangerous to ship. In 1988, the paper and



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