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close this bookIndustrial Metabolism: Restructuring for Sustainable Development (UNU; 1994; 376 pages)
View the documentNote to the reader from the UNU
View the documentAcknowledgements
View the documentIntroduction
Open this folder and view contentsPart 1: General implications
close this folderPart 2: Case-studies
Open this folder and view contents6. Industrial metabolism at the national level: A case-study on chromium and lead pollution in Sweden, 1880-1980
Open this folder and view contents7. Industrial metabolism at the regional level: The Rhine Basin
Open this folder and view contents8. Industrial metabolism at the regional and local level: A case-study on a Swiss region
Open this folder and view contents9. A historical reconstruction of carbon monoxide and methane emissions in the United States, 1880-1980
close this folder10. Sulphur and nitrogen emission trends for the United States: An application of the materials flow approach
View the documentIntroduction
View the documentSulphur emissions
View the documentNitrogen oxides emissions
View the documentConclusion
View the documentReferences
Open this folder and view contents11. Consumptive uses and losses of toxic heavy metals in the United States, 1880-1980
View the documentAppendix
Open this folder and view contentsPart 3: Further implications
View the documentBibliography
View the documentContributors
 

Conclusion

A comparison of the sulphur and nitrogen emissions reveals significant differences:

1. National sulphur emissions have fluctuated between 8 and 16 million tons a year since the turn of the century; nitrogen oxides, on the other hand, monotonically increased until the 1970s.

2. Since the 1970s, the main source of sulphur oxides has been coal combustion in power plants, while nitrogen oxides are contributed primarily by internal combustion engines.

3. Sulphur emissions result from oxidation of the sulphur impurity contained in fossil fuels and metal ores; nitrogen oxides are formed primarily by fixation of atmospheric nitrogen at high temperatures, and to a lesser degree by oxidation of fuel-bound nitrogen.

4. The control of sulphur oxides will have to rely on the removal of sulphur from the fuel or flue gases. Nitrogen oxides controls can be accomplished by technological changes in the combustion itself.

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