. "Use of Materials Balances to Estimate Aggregate Waste Generation in the United States." Measures of Environmental Performance and Ecosystem Condition. Washington, DC: The National Academies Press, 1999.
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and, thanks to the large amount unaccounted for, could have been as much as 1.9 MMT, of which as much as 1.45 MMT could have been in the form of sulfuric acid (Bureau of Mines, 1989). This would correspond to about 4.5 MMT of the acid. In the case of chlorine (see above), we saw that about 6.6 MMT were used within the chemical industry to make organic chemicals or final products. As regards caustic soda, it appears that 4.2 MMT were used for acid neutralization within the chemical industry. In addition, small amounts of fluorine (0.18 MMT), bromine (0.1 MMT), and phosphorus pentoxide (0.075 MMT) were used.33
Uncertainties in sulfuric-acid and caustic-soda requirements can be reduced, based on the knowledge that all acids and alkalis must be neutralized. Moreover, apart from small amounts of hydrochloric, nitric, and hydrofluoric acid, sulfuric acid is the dominant source of acidity (H+), while caustic soda and ammonium hydroxide are essentially the only sources of balancing hydroxyls (OH). However, ammonium sulfate is virtually all recovered in fertilizer, and both N and S have already been accounted for. Thus, virtually all other sodium and sulfur inputs must end up in waste streams (largely as sodium sulfate), because they are not embodied in products. The basic neutralization reaction is
2NaOH + H2SO4 →Na2SO4 + 2H2O.
The molecular weight of sulfuric acid is 98 g mole whereas the molecular weight of caustic soda is 40 g mole. Because the reaction requires two moles of caustic soda per mole of sulfuric acid, it would consume 1.22 mass units of sulfuric acid per unit of caustic soda. Thus, if 4.2 MMT of caustic soda was neutralized in the organic sector, we would have needed 5.15 MMT of sulfuric acid.34
Based on the above analysis, we argue that, in the synthetic organic chemicals sector, the ratio of sulfuric acid to caustic soda, in mass units, must be close to 1.22. Because the maximum amount of sulfuric acid available for organic synthesis processes, including acid unaccounted for, was 4.5 MMT, we conclude that not much more than 3.7 MMT of caustic soda could have been used in the same processes. (The remainder of the caustic, about 0.5 MMT, must have been used in the inorganic chemical sector.)
Adding these (Figure 8), we arrive at a grand total of 61 MMT of produced chemical inputs to organic synthesis in 1988. Oxygen is needed for a number of downstream oxidation processes, such as production of ethylene and propylene oxides; ethanol, isopropanol, and butanol; phthalic anhydride; terephthalic acid; and oxy-chlorination of ethylene to EDC.
A survey of the major products of the synthetic organic sector reveals that the oxygen content of final product chemicals averages close to 10 percent, which would amount to a total of about 4 MMT oxygen (O). We can account for 1.85 MMT O embodied in the input methanol. There is also some oxygen in cellulose and fatty acids. Some oxygen is carried into the reactions by the oxidizing agents nitric and sulfuric acid (HNO3 and H2SO4). But nitric acid is itself produced by