oxidation of ammonia, and sulfuric acid is the oxidized form of sulfur (dissolved in water). We estimated above that 1.45 MMT S, or 4.5 MMT of sulfuric acid, were utilized in organic synthesis in 1988. This would include 2.9 MMT O. We must also allow for 3.7 MMT NaOH used in organic synthesis processes, of which 1.4 MMT was oxygen. Altogether, this adds up to 6.15 MMT O, which is somewhat more than the amount actually embodied in final products.

In principle, no additional oxygen is needed, except to combine with carbon and/or hydrogen in the feedstock to generate energy to drive the endothermic syntheses. In practice, however, very little of the oxygen embodied in caustic soda or sulfuric acid ends up in the products. Rather, it ends up as water in the neutralization reaction. Thus, to arrive at a final oxygen content of 3.9 MMT, as indicated, we must assume that at least 2 MMT have been extracted from the atmosphere in various processes. This does not include the oxygen needed to oxidize all the missing mass to its final form, however.

Adding these, we arrive at a grand total of 61 MMT of produced chemicals and 2 MMT of oxygen as inputs to organic synthesis in the United States in 1988, not including oxygen that is used for combustion purposes and finishes as carbon dioxide. The major outputs, in terms of sales, of the organic chemicals industry amounted to 39.1 MMT in 1988 (and 39.5 MMT in 1989), not including urea. The categories are listed in Table 6.

Subtracting the weight of identified products from the weight of inputs, we find that the missing mass was around 23.9 MMT, not including the mass of any oxygen combined with carbon as process wastes. The situation is summarized graphically in Figure 8. The approximate composition of the waste stream can be estimated from the composition of the inputs; however, it is clear that water, sodium sulfate, and carbon dioxide must account for most of the waste. The remainder consists of various other salts, including some NaCl, and VOCs. A more detailed breakdown would be possible if we knew the inputs more accurately.

Primary Metals Smelting and Refining35

We have conceptually divided the processes of mining, concentration (winning), reduction (smelting), and refining. There are four stages of separation or recombination. The first two, being physical in nature, are assigned to the mining sector or the quarrying sector. They were discussed above. The last two, being chemical in nature, are assigned to the primary metals sector. At each separation stage, wastes are left behind and a purified product is sent along to the next stage. In principle, the wastes can be determined by subtracting outputs from inputs.

Unfortunately, from the analytic point of view, appropriate published data are rarely available. There are significant imports and exports of concentrates and crude metals (and even some crude ores), but trade data are often given in terms of metal content rather than gross weight. Domestic data are also incom-

The National Academies of Sciences, Engineering, and Medicine
500 Fifth St. N.W. | Washington, D.C. 20001

Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement