1. SULFUR AND NITROGEN EMISSION TRENDS FOR THE U.S. Yu Kuwabara Submitted to Prof. Husar Sustainable Air Qualtiy 02-02-02

2. Background There are many reasons why looking at sulfur and nitrogen emission trends are important. Fossil fuels are the most significant material metabolized by industry, and sulfur and nitrogen are residues. The assessment of emission trends are done using complete end-to-end material balances.

3. Sulfur Emission Trends (coal) Sulfur emissions can be analyzed by calculating the total fuel and mineral production and the concentration of sulfur in fuels and minerals. Coal production – The production of coal began around 1870 and dramatically increased to peak around 1920. Since then it has fluctuated, but there has been major changes in where the coal was consumed. Currently, electric utilities are the main coal-consuming industry. Earlier (before 1945) coal consumption was divided up among electric utilities, railroad, heating, oven coke, among others.

4. Sulfur Emission Trends Oil production is another sector which mobilizes a lot of sulfur. One advantage of oil production in terms of sulfur production is that a fraction of the sulfur is recovered as sulfuric acid, and the recovery ratio has been increasing steadily. Another contributor to sulfur emissions is metal smelting. But as in oil production sulfuric acid can be retained and recycled in the process.

5. Nitrogen Emission Trends Although nitrogen is a constituent in the natural ecosystem, Nox produced anthropogenically is considered a “pollutant” since it can be toxic to humans and biota. The US EPA determined four emission factors by the fuel-type: coal, gasoline, natural gas, and other petroleum products. Using these emission factors, emission trends were calculated.

6. Comparison between the two trends The nitrogen oxide emissions have been increasing steadily, while currently leveling off. The sulfur emission trends have been more erratic, but appears to have leveled out. The fluctuations in emissions are most likely the product of major wars, recessions, environmental concerns among others. Figure 1: Total nitrogen oxide emission trends Figure 1: Total sulfur emission trends

7. Summary Sulfur and nitrogen oxide emissions are important data to look at because of its toxicity and abundance. Sulfur emissions have fluctuated between 8 to 16 million tons per year since 1900. Nitrogen oxide emissions have steadily increased. By looking at the data, it is easy to point where the problem is.

8. What I learned Sulfur and nitrogen oxide emissions are important to keep track of. There are many ways to stop or slow down emission standards. Emissions change dramatically as technology changes, or as the demand changes.