SULFUR AND NITROGEN EMISSION TRENDS FOR THE U.S. by Rudolph B. Husar Summary Report by Sarah Lahr ME 449 Sustainable Air Quality 2/4/02

Introduction n The burning of fossil fuels is the most significant contributor of sulfur and nitrogen compounds to the air and in turn land and water n Coal and oil products combustion and metal smelting cause the majority of sulfur and nitrogen emission to enter the atmosphere n Various fuels have been the primary fuel used over the years including: wood ( ), coal ( , ), natural gas and petroleum (after 1960).

Sulfur Emissions from Coal Production n Coal is mined in 3 regions in the U.S. –Appalachian - varying range of sulfur (1-4%) –Midwest - high-sulfur percentage (2-4%) –West - cleaner, low-sulfur percentage (<1%) n The use of Western coal has increased dramatically in the past 30 years because of its low-sulfur content Over the past 40 years, the use of coal has been determined by the electric utilities

Sulfur Emissions from Other Sources n Oil Production –During the process of crude oil refining, some of the sulfur can be recovered as sulfuric acid n More than 50% of the sulfur is now recovered in this form n Copper and Zinc Smelting –Sulfuric acid can also be removed from smelter gases using converters n 50-70% of the sulfur can be removed using tightly hooded converters (further removal requires scrubbing) –Since 1980, more than 50% of the sulfur from metal smelting was recycled

Nitrogen Oxide Emissions n Despite nitrogen’s natural presence, it is a pollutant and hazardous to humans when in the following forms: NO, NO 2, N 2 O n In 1980, the NO x emission came from the transportation sector (internal combustion engines), power plants and industrial sources (boilers) n High temperature combustion of fossil fuels leads to nitrogen emissions (metal-processing plants and open-air biomass are insignificant)

Comparing Sulfur and Nitrogen Emissions n Emissions have fluctuated from 8-16 million tons per year n Main source: Coal combustion in power plants n Results from oxidation of sulfur impurities in fossil fuels and metal ores n Removal must occur in the fuel or in the fuel gases n Nitrogen oxides monotonically increased until 1970 n Main Source: Internal combustion engines n Results primarily from fixation of atmospheric nitrogen at high temperature n Removal can occur with further technological advances in combustion Sulfur Nitrogen

What I learned This article made me think about the various kinds of fuel that the U.S. has used since the 19th century and how history affected what was being used. I learned a lot about coal production and the differences between the coal in different parts of the country. I also found the problem-solving to limit the amount of emission to be interesting, especially the section on nitrogen emissions.