Class Project Report, May 2003 ME/ChE 449 Sustainable Air Quality Causality of US Sulfur Production and Emission Trends By James Agan, Kate Miller, Cat Reid, Jason Reynolds Instructor Rudolf B. Husar Washington University, St. Louis, MO

Sustainable Development (NAS) A process of reconciling society’s developmental needs with the environmental limits over the long term. It includes differing views on what should be developed, what should be sustained and over what time period. Human activities exert pressures, such as burning fossil fuels that alter the state of environment, such air quality. The impaired environmental state, elicits responses, such as regulations in a Pressure-State-Response (PSR) feedback loop system. These three classes of variables can be measured using data that are collected for administrative purposes. Combining these data with a simple but flexible scenario captures a fundamental idea of sustainable development The NAS (1999) describes SD as an uncertain and adaptive process, “in which society's discovery of where it wants to go is intertwined with how it might try to get there”. During the ‘journey’, the pathways of a transition to sustainability have to be ‘navigated’ adaptively at many scales and in many places.

Trend of Indicators SOx = Pop x GDP/P x Btu/GDP x Sox/Btu 1960s 1970s 1980s 1990s

US Population Trends In the 20th century, the US population has grown from 80 to 300 million In As the birth and migration rates are greater than the death rate, the US population will continue to increase in the future However, these rates are expected to stabilize over the next 50 years –Birth rate ~ 1.5%/year –Death rate ~ 1%/year –Migration rate ~ 0.25%/year

Regional Population Projections *Regions split according to geographic and state growth trends

National Income by Industry Group/Person The income of the res/comm sector has grown a the fastest rate, 10-fold since 1930, more than doubling since The industrial and transportation sectors have grown < 30% since the 1950s. It appears that the industrial and transportation sectors will remain fairly steady over the next 20 years, while the res/com curve will continue its rise before slowly leveling. Fraction of Total Income Trend by Ind. Group 1970 = 1

Coal Production and S Content Significant coal production is in the west with a much lower sulfur concentration, allowing for less sulfur pollution without decreasing consumption. The high concentration of sulfur is found in the eastern coal mined in the US. Sulfur in Western coal is generally < 1%

Coal Sulfur Flow in 1980 and 1998 In 1980, a major flow of sulfur in coal originated in Illinois and was transported to Florida Arrows indicate the flow of coal from the mines to the consumer By 1990, the transport of high sulfur coal from the Midwest has bee replaced by low sulfur western coal

Sulfur Transfer by Fuels and Minerals: Theory An understanding of the flow of sulfur is paramount in moving toward sustainability. Know how much is produce, how much flows to the consumer, and how much makes it to the receptors provides a way to monitor and catch the sulfur before it makes it into the atmosphere, water, soil and etc.

US Coal Production by Region Coal production in the US occurred over five major producing regions. The coal production over the eastern US has remained roughly constant throughout the century. The sharp increase since the 1980s is due to the addition of western coal.

Trend of Average Coal S Content The average sulfur content of coal from each region is quite different; Eastern coal is > 1%, western coal is ~0.5 %S. This average content has remained fairly constant for each region since it is determined by geological factors. Therefore, the dip in the national average sulfur content must be a direct result of the change in the source of sulfur, ie, more coal from the west is being used.

Flue Gas Desulfurisation (FGD) of El. Util. Coal This figure shows the impact that FGD, (scrubbers) on coal fired power plant emissions Since the 1970s when they were first used, scrubbers have steadily increased in capacity. Currently (2000), scrubbers remove about 30% of the sulfur from the flue gases. Hence, sulfur is being reduced both before (low sulfur coal) and after (scrubbing) the coal is converted to energy.

Sulfur Recovery Nature recycles the its sulfur, thus reaching a sustainable level for life. Man has not reached a sustainable level for sulfur, because the amount recovered has not been good in past years. The amounts recovered has drastically changed over the year especially in some sulfur producing processes moving us to sustainability.

Sulfur Flow Diagram (Tentative) Mineral MiningProductionConsumption AirLandWater S Stocks Exp/Imp Raw Fuel MiningRefiningCombustion Minerals Flow for Goods Metals, Frasch, Pyrites Fuels Flow for Energy Coal, Oil, Gas Exp/Imp Proc Ex/Im RawEx/Im Processed Exp/Imp Air Ex/Im Water S as PollutionS as Goods Sulfur flows into the environment through (1) direct mining + byproduct of metals; (2) energy sources, such as coal, oil and natural gas Within these sources, there is some recycling and recovery of sulfur Un-recovered sulfur is then released to the air, water, and soil environment as pollution

US Industrial Sulfur: Supply and Demand Trend US S Budget S Stocks Exp/Imp US S Supply US S Demand Source Although the US was a leading source of mined sulfur, this industry has virtually disappeared The use of recovered sulfur has negated much of the need for mined raw sulfur The stocks of sulfur have decreased from about 4 Mtons in the period to virtually zero However, the US consumption of sulfur exceeds that produced through environmental recovery, so over the past 25 years, it has imported sulfur

Total S Mobilized and Recovered Most of the S mobilization is driven by fuels, particularly coal (10-15 Mtons/yr) Mined elemental sulfur peaked around 1970 but became insignificant by 2000 Recovered sulfur, especially from petroleum refining, has increased dramatically since 1950 The overall flow of mobilized sulfur has increased steadily until about 1970 followed by a downturn Mobilized in Fuels Mobilized in Minerals Recovered from Fuels & Min.

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.

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 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).

SOx Emission Trend By Industry Group and by Fuel/Material The majority of emissions come from coal use, which peaked in the period. Oil products, metal smelting and industrial chemicals were also major contributors, but their emissions have declined rapidly since the 1970s. Emissions by Sector 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. In fact, electric utilities, which tend to be coal-powered, account for increasing fraction of the tional Sox emissions, reaching 70% in the 1990s

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

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

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.

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.

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).

SOx Emissions: Where are We Heading and What Can I Do? Relative Emissions by Sector Electric energy consumption account for 70% national Sox emissions Reducing electricity consumption is the most effective contribution to Sox pollution reduction Over much of the country, air conditioning and appliances are the main consumers of res/comm electric energy Heading Toward SustainabilitySome Regulations In place

Population - Energy/Goods Consumption– Materials Flow - Emissions E k =  c jk EM j =   b ij c jk GE i =    a i b ij c jk P Industr. Energy Transp. Energy ResCom.Engy Coal Oil GasElectric Energy SOx NOx HC PM Goods &Energy,(GE) iFuels&Mater.(FM), j Emission (EM), k Ind. Chemicals Industr. Goods Pop., P Metals Mercury a i Consump./Person b ij Fuels/Energy c jk Emission/Fuel- jjiiij Consumption of Goods and Energy:GE =  a i P Fuels and Materials Flow:FM =   a i b ij P Emission of Pollutants:EM =    a i b ij c jk P Industrial Prod. Transportation ResComercial EconMeasure(EM) The causal driver to pollutant emissions is the human population  These emissions result from energy and material processes, which are driven by economic sectors The causal factors of anthropogenic Sox emissions can be traced by this chart