Table 3.2. Annual Primary Particulate Emissions from U.S. Coal- Fired Utilities Compared to Annual Particulate Emissions from All Sources conversions. Sulfate aerosols formed in the atmosphere from the chemical reaction of anthropogenic SO2 emissions account for 2-10 times the particle concentration in the atmosphere caused by anthropogenic primary particle emissions. Coal combustion accounts for almost 70% of man's global emissions of SO2. However, increasing use of SO2 emission-control devices may to some extent limit the growth of SO2 emissions in the future. Nitrate aerosols contribute less than do sulfates to total particulate loading of the atmosphere, but emission controls for N0x are less available and less efficient. Moreover, the combustion of oil and gasoline is also a large source of N0x. It is difficult to assess the contribution of coal use to climate change through increased atmospheric particle loading. The impact of coal on global particle concentration may be significant, but it appears to be of less consequence than the impact of coal use on CO2 levels. 3.1.3 CO2 Impacts The combustion of coal releases substantial amounts of carbon dioxide to the atmosphere. It has been estimated that coal combustion, averaged over the earth, releases CO2 at the rate of approximately 98.6 kg lO^/j.^ Thus, a conventional 500-MWe coal-fired power plant&0 will emit about 10? t of CO2 per year. There is at present no effective, efficient method for controlling combustion emissions of CO2 to the atmosphere. The only practical means of reducing the CO2 added to the atmosphere by coal combustion is to reduce the amount of coal burned.
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