• the enzyme. Therefore, the current challenge is to bioengineer a strain that completely lacks the gene.

  • 16.

    This does not take into account the bark, which constitutes about 11.5 percent of the raw weight of roundwood (United States Congress, Office of Technology Assessment, 1984, table 5). We have completely omitted bark from our calculations by assuming that a cord of roughwood is equivalent to 80 cubic feet of debarked (peeled) roundwood. This suggests that about 10 MMT of bark would be produced by debarking operations, which precede pulping proper. Based on 48 percent moisture content, 10 MMT raw weight might be consistent with 5 MMT dry weight. (Bark is burned as "hog fuel.")

  • 17.

    U.S. production of sodium chlorate in just the third quarter of 1992 was 0.131 MMT, which implies an annual rate of over 0.5 MMT, twice the level of 1988. In the same quarter, apparent consumption was 0.203 MMT, of which 37 percent was imported (United States Department of Commerce, 1992). The explanation is that chlorine dioxide has been very rapidly substituting for elemental chlorine as a bleach for pulp. Most of the increase in U.S. demand since 1988 is for conversion to chlorine dioxide.

  • 18.

    U.S. production of paper products in 1988 consisted of 5.364 MMT of bleached newsprint (made from mechanical pulp), 19.59 MMT of printing and writing paper (coated and bleached), and 44.57 MMT of "other machine made paper and paperboard," of which 36.056 MMT consisted of Kraft paper and paperboard (Bureau of the Census, 1991).

  • 19.

    Data on materials handled are from Bureau of Mines (1989, Volume 1, tables 10, 11). Other data in this section on metals and minerals come from individual chapters in the same source.

  • 20.

    In the case of iron, concentrates for blast furnaces (pellets and sinter) are treated differently. Pellets are produced at the mine, whereas sinter is included in the smelting sector rather than in the mining sector. For consistency, we adopt this convention. In the case of aluminum, the concentration stage is taken to be the chemical conversion of bauxite ore into pure aluminum oxide, or alumina. This process is conventionally included in the inorganic chemical industry. Phosphate rock concentration, yielding fertilizer-grade superphosphate, is included in the fertilizer industry. Phosphorus metal and phosphoric acid from phosphorus are both also included with inorganic chemicals.

  • 21.

    Data on materials handled are from Bureau of Mines (1989, Volume 1, tables 10, 11). Other data in this section on metals and minerals come from individual chapters in this same source.

  • 22.

    The quantity of refuse produced obviously depends on the intensity of the beneficiation (washing) process. For comparison, the only coal cleaning process described in an official report of the United States Department of Energy (1980) had only a 70 percent yield in mass terms and a 90 percent yield in energy terms. Specifically, 1,428 tons of "run-of-mine" coal produced 1,000 tons of "clean" coal.

  • 23.

    All data in this section are extracted from International Energy Agency (1991, pp. 664-665).

  • 24.

    Light ends are compounds with boiling points in the range of butane (about 0 °C) and below. Methane and the light alkanes (C2-C 4) fall into this category.

  • 25.

    Benzene, ethylbenzene, toluene, and xylenes constitute, respectively, 0.1, 0.51, 0.19, and 0.88 percent of average crude oil by volume (Gaines and Wolsky, 1981). They constitute, of course, a much higher percentage of the volatiles.

  • 26.

    Unless otherwise specified, the basic data for this section are from Bureau of Mines (1989).

  • 27.

    Phosphorus pentoxide dissolved in water is phosphoric acid, the active ingredient in most phosphate fertilizers (e.g., superphosphates). It is not used, generally, in pure form.

  • 28.

    The electrolytic process for chlorine production from brine yields 1.1 units of sodium hydroxide per unit of chlorine, with inputs of 1.75 units of sodium chloride. However, some chlorine is produced from magnesium chloride, and some is regenerated from hydrochloric acid, so the ratios are not exact.

  • 29.

    Sodium chlorate used to bleach paper pulp is almost unique among chlorine chemicals. It is not manufactured from elemental chlorine but is made directly from sodium chloride (salt).

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