1. Energy Consumption and Energy/$ Since 1950, the energy consumption has increased at similar rates in all sectors Energy use/$ is the largest in the transportation and smallest in the ResComm sector The energy use/$ of the industrial sector has not changed substantially since the 50s Over the past 50 years, the the energy/$ of the entire economy has has improved by about 30%. The transition from ‘smokestack’ (industrial) to less energy-demanding ResComm economy was a major factor.

2. SOx Emission Factor (SOx/Energy) 1.Up to the 1980s, the dominant emissions-sector was the Industry, but its emissions have declined rapidly since about 1970. In fact, by 2000, ResComm emissions exceed the Industry values. Transportation is not a significant SOx emitter. 2.The SOx emissions per energy use has steadily declined by a factor 2-3 in all sectors. The sharp decline in the transportation SOx emissions in the 1950s is due to the transition from coal to diesel locomotives. 3.It is important to note that these indicators may not show the whole picture, as some of the Sox in each sector is due to material flow rather than energy use, and the energy use can be direct or indirect (electric utilities).

3. SOx Emission Trend By Industry Group and by Fuel/Material The majority of emissions come from coal use, which peaked in the 1970-90 period. Oil products, metal smelting and industrial chemicals were also major contributors, but their emissions have declined rapidly since the 1970s. Emissions by SectorRelative Emissions by Sector In fact, electric utilities, which tend to be coal- powered, account for increasing fraction of the national Sox emissions, reaching 70% in the 1990s. The total national SOx emission trend shows a see-saw pattern over the past 60 years. The peak in the 1940s was due to intense industrial and res/comm activity. The peak emission of 30 million Tons/yr of around 1970 was mainly due to electric utilities.

4. Electric Utility & Metals Smelting Looking closer at the electric utilities, we see that the vast majority of emissions from electric utilities are from the use of coal. The recent decrease in Sox emissions from this source is due mostly to switching to coal with a lower average sulfur content (western coal). Emissions from metals smelting has been drastically reduced since 1970, even more than the electric utilities. This is primarily due to increased recovery of sulfur from the smelting process. Electric UtilitiesMetals Smelting

5. The contributions of material flows from other industries are significantly smaller (~1 MT/yr) than those from energy use (~10 Mt/yr) In general, these miscellaneous industrial emissions have been non-increasing. In the industrial sector, emissions from direct energy use tend to be dominated by emissions from coal. This has decreased, in part because energy is increasingly supplied by the electric utilities The petroleum industry in particular has been successful in recovering sulfur from their material flows, and thereby reducing emissions steadily. Industrial Fuel CombustionPetroleum and Related Industries

6. Commercial-Residential In the commercial/residential sector, Sox emissions from fuel use have declined significantly, primarily due to the fact that most energy is now supplied by the electric utilities. Also, there was a switch from ‘dirty’ coal to cleaner oil. Emissions from other miscellaneous residential/commercial combustion and processes were relatively small, and have dropped to almost zero since 1980.

7. Transportation The non-road Sox emissions came historically from the use of coal in railroads, and has decreased with their fall from favor as a means of transportation. On Road TransportationNon-Road Transportation Road vehicles, contribute to Sox emissions primarily through diesel vehicles However, by the 1990s, diesel emissions have declined to level of gas fueled vehicles.

8. SOX Emission Factors for Industry Groups -With this detailed analysis, we can revisit trends in emissions factors (Sox/energy) and summarize: -The industrial and res/comm sectors both illustrate decreases in direct fuel use and an increased use of electricity. -The emissions factor for res/comm direct fuel use has decreased more significantly because it is now dominated by oil use rather than coal (as in the industrial sector). -The overall emissions factor decrease, even with electricity added in, is indicative of how the electric utilities have decreased emissions/energy by switching to lower sulfur content coal. This can also be seen in the emissions factors for fuels (left).