Preliminary Characterization Study Traditional Fuels and Key Derivatives

Prepared in Support of the

Proposed Rulemaking – Identification of Nonhazardous Secondary Materials That Are Solid Waste

March 18, 2010

1 Introduction

This document summarizes the features, composition, and char acteristics of both traditional fuels used in stationary com bustion sources and their key derivatives.
Traditional fuels include fossil fuels (coal, fuel oil and natural gas) and wood

. Derivatives include:

• Coal-based derivatives: bituminous coke, coal tar oil, blast furnace gas, and coke oven gas, and

• Petroleum-based derivatives: petroleum coke, refine ry gas, and asphalts.

For each fuel, this memorandum presents the following information to the extent readily available:

1. Chemical Composition . Fuels are often described by an ultimate and/or proximate analysis. An ultimate analysis is an elemental analysis of major components, typically carbon, hydrogen, oxyge n, nitrogen and sulfur as well as
ash. 1 Meanwhile a proximate analysis determines the moisture, volatile matter, fixed carbon and ash content of the fuel. Gaseous fuels and some liquid fuels can also be described by their constituent compounds. In general, the compositional analysis is presented on a weight ba sis for liquid and solid fuels and on a volumetric basis for gaseous fuels.

2. Heating Value (Calorific Value). The heating value of a fuel is its energy value or its heat of combustion (i.e., the ener gy released when a unit mass (or volume) of the fuel is burned). The heating value of a fuel may be measured according to its higher heating value ( HHV) or its lower heating value (LHV). The HHV, or
the gross heat of combustion, is the ener gy released when the products of combustion are brought to a standard te mperature and any water produced from

1 For example a typical ultimate analysis might be: 60% carbon, 15% hydrogen, 10% oxygen, 3% nitrogen, 2% sulfur, and 10% ash. Ash, while part of the ultima te analysis, is shown separately because it represents
a fraction of the fuel that does not burn.the process is condensed. The LHV, also referred to as the net heat of combustion, treats the moisture produced from combustion as vapor. Unless specified otherwise, all heating values presented in this document are HHVs and will be presented on an as-received basis (i.e., with moisture and ash included).

3. Composition of Non-Fuel Constituents and Impurities . Non- fuel constituents include gases with no fuel value such as nitrogen, carbon dioxide and inert gases as well as moisture and ash. Impurities (i.e., contaminants) may include sulfur compounds and trace metals such as mercury, vanadium, cadmium, chromium and lead. Impurity levels are typically presented as parts per million by weight (ppm) or parts per million by volume (ppmv)

We present this information by the major fuel groupings outlined above. Section
2 describes coal and its derivatives. Pe troleum-derived fuels are detailed in Section 3, while Section 4 presents in formation on natural gas. Section 5 provides the composition and ot her characteristics of wood.

Limitations of this Analysis :

• This document presents information that is readily available from engineering reference publications and re putable online sources. A search of scientific, peerreviewed journals was not performed due to time and budget constraints.

• When possible, we present composition and heating values that are representative of the values associated with a given fu el. However, for some fuels where the available data were limited, we present data from specific samples that were readily available. These sample data may or may not be representative.

22 Coal & Derivatives

2.1 Coal
The ASTM (Method D-388) classification for coal ranks coal into four primary
classes based on its vola tile matter and fixed carbon content as well as its heating value. The four categories (highest to lowest rank) are:

I. Anthracite

II. Bituminous

III. Sub-bituminous

IV. Lignite

Each of these classes is further divided into subclasses by the ASTM classification. In general the higher rank co als have higher carbon content and lower hydrogen and oxygen content in comparison to th e lower ranked coals. Most coals burned
in combustion units are either sub-bituminous or bituminous.

Anthracite: Anthracite coal is glossy blac k, hard, and by definition has a fixed carbon content of more than 86% (dry, as h free basis) and a volatile content of less than 14% (dry, ash free basis). Heating values typi cally are on the order of 13,000 Btu/lb. Anthracite coal is primarily found in northeastern Pennsylvania, and represents less than 2% of the US coal demonstrated reserve base. 2

Bituminous : Bituminous coal in general ha s lower fixed carbon (<86%, dry, ash free) and higher volatiles than anthracite . This coal has banded layers that alternate between glossy black and dull bl ack. Heating values for bituminous coal range from 10,500 to 14,000 Btu/lb. 3 Bituminous coals are the most abundant class of coal in the US and make up 53% of the demonstrated US coal reserve. Bituminous coal is found in many states ea st of the Mississippi River, including Illinois, Kentucky, West Virginia, and Pennsylvania.

Sub-bituminous : These coals are also black in color but with less banding and a higher moisture content than bituminous coals. Heating values range from 8,500 to 11,000 Btu/lb. Although heating values are lower than for bituminous coal,
sub-bituminous varieties in the US tend to have a relatively lo wer sulfur content
than bituminous coals. Sub-bituminous co al represents approximately 37% of US coal reserves; sub-bituminous reserves ar e highest in the states of Montana and Wyoming.

Lignite: This is the lowest ranke d coal. Lignite has a brown- black color and is soft relative to the other type s of coal. Heating values may range from 4000-8000

2 http://www.eia.doe.gov/cneaf/c oal/reserves/reserves.html , Accessed Nov 2008

3 Coal’s color is indicative of its age. As coal ages in the ground, its color changes from brown to dull black to glossy black.

3Btu/lb. Lignite is found in North Dakot a, Montana and Texas and accounts for
about 9% of US coal reserves.

Table 2-1 presents composition and h eating value data from Avallone &
Baumeister for select US Coals for each of the classes described above. 4 , 5 Note that the data in Table 2-1 are sample values; prope rties may vary widely within each rank.

Chemical Composition. As indicated in Table 2-1, most ra nks of coal consist primarily of
carbon.

Non- Fuel Constituents . Moisture and ash represent the non-combustible constituents in coal. The primary components of ash are si licon dioxide, aluminum oxide, ferric oxide, and calcium oxide. (See Table 2-1)

Contaminants. One trace constituent of particular concern in coal is mercury. The mercury content of coal ranges from less than 0.1 ppm to 1.8 ppm with a median value of 0.11 ppm. 6 Approximately 80% of samples te sted below 0.25 ppm. Coal may also contain several other metals such as arsenic, chromium and manganese as shown in Table

2-1. 7

Trace Organics : Data on trace organics in U.S. coal are not readily available. One study from Spain, however, analyzed five Spanish and South African coal samples for volatile organics. 8 Of the several organics detected, only two were 40 CFR 261 Appendix VIII
hazardous constituents. Results for these tw o organics are shown in Table 2-1.

Additional information on the characterist ics of coal is available in the US Geological Survey coal quality database , which has information on over 7,000 Coal samples. 9

4 Avallone, E.A., & Baumeister, T.(eds), “Mark’s Standard Handbook for Mechanical Engineers,” 9 th
Edition, 1987, p 7-19

5 The values shown in the table only describe the specific samples shown although they were selected to be representative of the rank in general.

6 US Geological Survey, 2001 “Mer cury in Coal- Abundance, Distribu tion, and Modes of Occurrence,
USGS Fact Sheet FS-095-01

7 Davidson, R. A., “Trace Elements in Coal” 1996, Energeia, v.7, No.3, University of Kentucky, Center for Applied Research.

8 Fernandez-Martinez , G., et al, 2000, “Determination of Volatile Organic Compounds in Coal, Fly Ash, and Slag Samples by Direct Thermal Desorption/GC/MS, Analusis, v 28, pp 953-959

9 Bragg,L., et al, USGS Coal Quality (COALQUAL) Database: Version 2.0, http://energy.er.usgs.gov/products/databases/CoalQual/index.htm , accessed Nov 2008.

452.2 Fuels Derived from Coal

Bituminous Coke – Bituminous coke is
derived from the destructive distillation or pyrolysis of bituminous coal. This involves heating coal to very high temperatures (over 1000 °C) in the
absence of air in a furnace. Much of the moisture and volatile components are driven off leaving behind a product high
in carbon. While coke is the desired end product of the distillation/pyrolysis process, fuel gases, tar and oil with fuel value are also typically produced. A large fraction of bituminous coke (approximately 90%) is burned in blast furnaces for steelmaking. The remainder is largely used in foundries and for space heating.

Table 2-2 shows the typical chemical composition and heating value of bituminous coke. Unsurprisingly, the
fixed carbon and ash content are much higher than the corresponding values for coal. The heating value of bituminous coke is comparable to coal. Table 2-2 also presents composition and heating value estimat es for coke breeze, an undersized coke (particle size < 15 mm), comprising about 5% of the total bituminous coke production. Coke breeze is not suitable for firing in a bl ast furnace but is typically used for steam generation. Information on the impurities cont ained in blast furnace coke is not readily available, but such information is availabl e for coke breeze, as shown in Table 2-2. 10

10 Ocean Surveys Inc., 2005, Site Demonstration of the AQUABLOKTM Sediment Capping Technology, http://www.hsrc-ssw.o rg/6MonthAppH.pdf , accessed November 2008

6Coal Tar Oil : Coal tars are liquid products of th e carbonization process to produce coke. They may range from free-flowing, low viscosity liquids to highly viscous coal tar pitch. Table 2-3 shows an ultimate analysis of coal tar fuels CTF 50 and CTF 400. 11 , 12 The table also presents estimates of the hea ting value for CTF 50 and CTF 400, as well as
information on the non-fuel constituents and trace metals in these fuels.

Table 2-3 also presen ts viscosity values for CTF 50 and CTF 400, expressed in centistokes (cSt). For comparison, water has a viscosity of about 1 cSt at 20°C and a liquid with a viscosity of 2 cSt at
20° would have twi ce the viscosity of

water. 13

Because coal tar oil is made up of a complex mixture of more than a thousand individual compounds,
fractional distillation of coal tar oil can yield a spectrum of compounds for use in resins, polymers, motor fuel, wax and electrode compounds. 14

Coke Oven Gas: Coke oven gas is the gaseous non-condensable fraction generated from the coke production process. As the analysis (by component) in Table 2-4 shows, coke oven gas is primarily composed of hydrogen and methan e. The heating value is approximately 600
Btu/ft 3 and is about 55-60% that for natural gas (on a volume basis).

Impurities in coke oven gas may include hydrogen sulfide, ammonia, and hydrogen cyanide. 15 , 16 Table 2-4 also shows the sp ecific gravity of coke oven gas. 17

11 Perry, R.H., Green, D.W., Mahoney, J.O., “Perry’s Chemical Engineers’ Handbook, 1997, 7 th Edition,
McGraw Hill..

12 CTF stands for coal tar fuel. The designation CTF 50 and CTF 400 indicate the temperature to which the oil must be pre-heated (50 °F and 400°F, respec tively) in order to be atomized in a burner.

13 Viscosity values shown is for kinematic viscosity = dynamic viscosity/density. Note viscosity decreases with temperature for liquids.

14 Skov, E.R., et al, “Coal Tar Chemicals and Syncrude Oil Production from Low-Rank Coals using MildTemperature Pyrolysis,” Proc of AICHE Spring National Meeting, Houston, TX, April 2007. AICHE
Session 16002.

15 Kohl, A., et al, 1997 “Gas Purificatio n,” Gulf Profession al Publications.

16 Note that for many gaseous fuels, impurities su ch as ammonia, and hydrogen cyanide are mostly removed prior to being used as a fuel in a boiler

17 Specific gravity is the ratio of the density of th e substance to a reference substance. The reference substance is air for a gas and water for a liquid.

7Blast Furnace Gas: Blast furnace gas is a low quality gas that is a by-product of the blast furnace reduction process. Table 2-4 presents volumetric composition and heating value estimates for this fuel. Although the heating value is low, the amount of gas generated by blast furnaces makes it economically feasible to recover the energy. 18 The energy value is low because approximately 70% of the volume of this fuel is made up of nitrogen and carbon dioxide. Blast furnace gas may include small quantities of impurities including hydrogen cyanide. 19 Table 2-4 also shows the specific gravity of blast furnace gas. Blast furnace gas is either burnt as fuel or flared.

18 Culp, A.W., 1979, “Principles of Energy Conversion,” McGraw Hill.

19 Gupta, C.K., 2006, Chemical Metallurg y: Principles and Practice,Wiley-VCH

83 Petroleum Fuels

This section presents characterizatio n data for fuels produced by petroleum
refineries as well as their derivatives. Although transporta tion fuels (e.g., gasoline and diesel) make up most of the petroleum-based fu el sold in the U.S., this section focuses on petroleum fuels utilized by st ationary combustion sources.

3.1 Fuel Oil

The term fuel oil may refer to any product derived from petroleum that has volatility lower than that of gasoline. The ASTM D396-2(a) specifica tion divides fuel oil into several classes, from fuel oil N o.1 to fuel oil No. 6, based on boiling range, composition, and other physical properties. Fuel oils are generally classified as either distillate or residual based on whether they are vaporized in normal refining operations. Usually, fuel oils No. 1 and 2 are distillate fuels; No. 5 and No. 6 fuel oils are residual fuels, and No.4 is a blend of distillate and residual fuels. 20 Note that diesel has similar but not identical properties and sp ecifications to fuel oil No.2.

Table 3-1 provides the chemical compositi on, heating values, and typical physical properties of various classes of fuel oil such as flash point, specific gravity, API gravity, and viscosity. 21 The flash point is the temperature to which the liquid must be heated to produce vapors that flash but do not burn cont inuously. API gravity is calculated by:

5.131 60@ 5.141

− = F gravity specific Gravity API

Composition: Fuel oils are primarily composed of hydrocarbons, specifically paraffins, isoparafins, napthenes and aromatics. Table 3- 1 shows an ultimate analysis for different types of fuel oil from Perry et al.

Heating Values . Fuel oil heating values range from 18,000 to 20,000 Btu/lb or 130,000 to 150,000 Btu/gallon. As indicated in the table, re sidual fuel oils are extremely viscous and
must be heated in order to be tran sported and atomized in a burner.

20 USEPA, “AP 42: Compilation of Air Pollution Emissi ons Factors, Vol I: Stationary Point and Area Sources,” 5 th Edition, 1995, Ch.1.3 Fuel Oil Combustion. Di stillate fuels are lighter, less viscous, and have a lower boiling range when compared with residual fuels.

21 Property values from, Stultz & Kitto, eds, “Steam: It’s Generation and Use,” 40 th Edition, 1992, p 8-14.

9Moving along the scale from No. 1 fuel oil to No . 6 fuel oil, the characteristics of fuel oil changes as follows:

• The boiling point increases. For No. 1 o il, the boiling points of the different constituents range from 150-300 °C, while for No. 6 oil this range is 200-550 °C.

• The density increases (i.e., API gravity decreases)

• Viscosity increases from an average of about 1.8 centist okes (cSt) for No. 1 Oil to
90-400 cSt for No. 6 oil.

• Heating values decrease slightly.

10Impurities : As indicated in Table 3-1, the heavier fu el oils have higher levels of sulfur than the lighter fuel oils. The trace metal levels shown in the ta ble are from testing performed in 1998 for the development of th e comparable fuels specification, which was published in 1999. 22 This testing involved eleven samples for No. 2 fuel oil, one sample of #1 fuel oil, and seven samples of #6 fuel o il. Note that Perry et al. indicate that the nickel content of No. 6 Fuel Oil rang es from 10-500 ppm and that vanadium concentrations in No. 6 Fuel Oil range from 10-500 ppm.

Trace Organics : In developing the specifications fo r comparable fuels, EPA tested samples of fuel oil for most of the hazardous organics lis ted in Appendix VIII of 40 CFR Part 261. Specifications were developed fo r almost 200 individual volatile and semivolatile toxic organic com pounds (including hydrocarbons, oxygenates, nitrogenated organics, sulfonated organics, halogenated or ganics, and PCBs). Table 3-1 includes the concentrations for the Appendix VIII organics that were detected. 23

3.2 Other Petroleum Derivatives

Petroleum Coke – Petroleum coke is produced when vacuum distillation residues from the petroleum refining process are sent through a coker where
most of the volatiles are burned off. Petroleum coke may be called delayed coke or fluid coke, depending on the type of process/reactor used. Table 3- 2 provides an ultimate and proximate analysis for petroleum coke based on
data from Avallone & Baumeister and
Stultz & Kitto.

Petroleum coke is used as the primary fuel or as supplementary fuel in
fluidized bed boilers as well as a supplementary fuel in pulverized coal boilers and cyclone boilers. 24

Table 3-2 also provides a detailed ash analysis for petroleum coke. 25 As

22 See USEPA, 1999 “Final Technical Support Docu ment for Hazardous MACT Standards,” Vol. IV: Compliance with the HWC MACT Standards” Ch.17

23 Table 3-1 shows the highest level detected. Most of the compounds that EPA tested for were not detected. Comparable fuel specifications are based on either the highest detected value or the highest detection limit among all sample s. See USEPA (1999) op cit.

24 Tilman, D.A., et al, 2004, “F uels of Opportunity, Elsevier.

25 Ibid.

11indicated in the table, nickel and vanadium le vels are high similar to the residual fuel oils because heavy metals tend to concentrate in the heavier fraction of crude oil from which petroleum coke is produced.

Refinery Gas – Refinery gas is a general term describing the non-condensable fractions from various refinery processes, including at mospheric distillation, coking, reforming and cracking. These gases are sometimes ble nded together and are typically used by refineries for their energy value.

The composition of refinery gas is highly variable, although the primary constituents are C1-C4 hydrocarbons 26 (methane, ethane and propane in particular). Table 3-3- presents composition
information for two blended refinery gas samples and composition data from a 2003 lifecycle emissions study. 27 , 28

Estimated heating values for refinery gas are on the order of
1300-1500 Btu/scf. On a
volume basis this is a little h than natural gas because refinery gas contains a greater fraction of heavier gases. igher

alues Asphalts – Asphalt is made from the residue
that remains after the vacuum distillation process at petroleum refineries. It has a consistency ranging from a viscous liquid to a glassy solid. 29 Table 3-4 presents an ultimate analysis range for four asphalt samples. 30 Impurities include sulfur, vanadium and nickel and their reported concentrations are highly dependent on the source crude. Heating v for asphalt are on the order of 17,000-18,000
Btu/lb. 31

26 Hydrocarbons with one to four carbon atoms.

27 Baukal & Schwartz, 2001, “The John Zink Combustion Handbook” CRC Press

28 Delucchi, M., 2003 “A Lifecycle Emissions Model: LifeCycle Emissions from Transportation Fuels, Motor Vehicles, Transportation Modes, Electricity Us e, Heating and Cooking Fuels, and Materials., UCDITS-RR-03-17, available from http://www.repositories.cdlib.org/itsdavis

29 Speight, J.G. 2006, “The Chemistry and Technology of Petroleum,” CRC Press.

30 Wess, J., et al, 2004, “Asphalt (Bitumen), Concise International Assessment Document 59, World Health Organization”

31 Cross, R., 1919, “A Handbook of Petroleum, Aspha lt, and Natural Gas” Kansas City Testing Laboratory.

12Asphalt is primarily used as a paving and r oofing material. Asphalt is also used in asphalt-based paints, in lining irrigation canal s and water reservoirs, and in adhesives in
electrical laminates. 32 Although the use of asphalt as a fu el is not common, boilers have been designed to burn asphalt. 33

32 Wess, op cit.

33 Hunt, P.J., et al, 1999, “Boile r Designs for Asphalt Fuels,” POWER-GEN ‘99 International, New Orleans, Louisiana, November, 1999.

134 Natural Gas

Natural gas is widely used by boilers due to its low content of ash, ease of handling, and ease of combustion. In addition, na tural gas is a cleaner burning fuel than other fossil fuels. The primary constituent of natural gas is methane. Other paraffinic hydrocarbons such as ethane, propane, and butan e, as well as other diluents gases (e.g., nitrogen), may be also present. The compos ition of natural gas fiel d samples as well as pipeline gas is shown in Table 4-1.

Heating Value: The heating value of natural gas, like its composition, varies by region but usually is in the range from 950-1150 Btu per cubic feet. Diluents include carbon dioxide and nitrogen.

Impurities: Trace contaminants found in natural gas include hydrogen sulfide and other sulfur compounds. If naturally occurring le vels are high, these compounds are removed using various processes because most pipelin e specifications limit the level of sulfur

14compounds that may be cont ained in pipeline gas. 34 Other impurities may include mercury in very low levels. As Table 4-1 indicates, mercury levels are well below one part per billion (ppbv). 35 Trace levels of odorants (eg. mercaptans) are often added to pipeline gas, which allows natural gas leaks to be easily detected.

Trace organics : Only limited information on the organics content of natural gas was readily available. The one organics anal ysis identified examined volatile organics concentrations in natural gas samples from three California utility plants. 36 Only two 40 CFR 261 Appendix VIII hazardous organics were detected. (See Table 4-1).

34 Natural gas with a high level of hydrogen sulfide is called sour gas.

35 Kidnay, A.J., et al, 2006 “Fundamental s of Natural Gas Processing” CRC Press.

36 Chow, W., & Conner, K.K., 1993, “Managing Hazardou s Air Pollutants: State of the Art, CRC Press.

155 Wood

Wood is burned primarily in industrieswhere wood residues are obtained as a byproduct. 37

Table 5-1 shows the properties of wood on a dry basis and an ash analysis based on data
from Stultz & Kitto. Wood has a lower carbon content and a much higher oxygen content compared to coal.

Heating values for wood (on a dry basis) are in the range 8000-9000 Btu/lb. Wet wood can have a significantly lower heating value. As indicated in Table 5-1, the sulfur content of wood is relatively low. Trace metals in wood may include lead and cadmium.

37 USEPA, 2003, AP-42, Ch.1.6, “Wood Residue Combustion in Boilers”, http://www.epa.gov/ttn/chief/a p42/ch01/final/c01s06.pdf , accessed Nov 2008.

16References

1. Avallone, E.A., & Baumeister, T.(eds), “Mark’s Standard Handbook for Mechanical Engineers,” 9 th Edition, 1987, p 7-19.

2. Baukal & Schwartz, 2001, “The John Zink Combustion Handbook” CRC Press.
3. Bragg, L., et al, USGS Coal Quality (COALQUAL) Database: Version 2.0, http://energy.er.usgs.gov/products /databases/CoalQual/index.htm , accessed Nov 2008.

4. Chevron Products Company, 2007, “Diesel Fuels Technical Review.”
5. Chow, W., & Conner, K.K., 1993, “Managing H azardous Air Pollutants: State of the Art,

CRC Press.

6. Cross, R., 1919, “A Handbook of Petroleum, Asphalt, and Natural Gas” Kansas City Testing Laboratory.

7. Culp, A.W., 1979, “Principles of Energy Conversion,” McGraw Hill.

8. Davidson, R. A., “Trace Elements in Coal” 1996, Energeia, v.7, No.3, University of Kentucky, Center for Applied Research.

9. Delucchi, M., 2003 “A Lifecycle Emissions Model: LifeCycle Emissions from Transportation Fuels, Motor Vehicles, Transpor tation Modes, Electricity Use, Heating and Cooking Fuels, and Materials., UCD-ITS-RR-03-17, available from http://www.repositories.cdlib.org/itsdavis

. 10. Fernandez-Martinez , G., et al, 2000, “Det ermination of Volatile Organic Compounds in Coal, Fly Ash, and Slag Samples by Direct Thermal Desorption/GC/MS, Analusis, v 28, pp
953-959.

11. Gupta, C.K., 2006, Chemical Metallurgy: Principles and Practice,Wiley-VCH.

12. Hunt, P.J., et al, 1999, “Boiler Designs for Asphalt Fuels,” POWER-GEN ‘99 International New Orleans, Louisiana, November, 1999.

13. Kidnay, A.J., et al, 2006 “Fundamentals of Natural Gas Processing” CRC Press.

14. Kohl, A., et al, 1997 “Gas Purificati on,” Gulf Professional Publications.
15. Ocean Surveys Etc., 2005, Site Demonstr ation of the AQUABLOKTM Sediment Capping Technology, http://www.hsrc-ssw.org/6MonthAppH.pdf , accessed November 2008.

16. Perry, R.H., Green, D.W., Mahoney, J.O., “Perry’s Chemical Engineers’ Handbook, 1997,

7 th Edition, McGraw Hill.

17. Skov, E.R., et al, “Coal Tar Chemicals a nd Syncrude Oil Production from Low-Rank Coals using Mild-Temperature Pyrolysis,” Proc of AICHE Spring National Meeting, Houston, TX, April 2007. AICHE Session 16002.

18. Speight, J.G. 2006, “The Chemistry and Technology of Petroleum,” CRC Press.
19. Stultz & Kitto, eds, 1992 “Steam: It’s Generation and Use,” 40 th Edition.

20. Tilman, D.A., et al, 2004, “Fuels of Opportunity, Elsevier.

21. US DOE, EIA, http://www.eia.doe.gov/cneaf/coal/reserves/reserves.html , Accessed Nov
2008.

22. USDOE, EIA, http://tonto.eia.doe.gov/dnav/ng/hist/n9190us3m.htm , accessed November

2008.
23. USEPA, 2003, AP-42, Ch.1.6, “Wood Residue Combustion in Boilers”, http://www.epa.gov/ttn/chief/ap42/ch01/final/c01s06.pdf , accessed Nov 2008.

24. USEPA, “AP 42: Compilation of Air Pollution Emissions Factors, Vol I: Stationary Point and Area Sources,” 5 th Edition, 1995, Ch.1.3 Fuel Oil Combustion.
25. USEPA, 1999 “Final Technical Support Document for Hazardous MACT Standards,” Vol. IV: Compliance with the HWC MACT Standards” Ch.17.

26. US Geological Survey, 2001 “Mercury in Coal- Abundance, Distribution, and Modes of Occurrence, USGS Fact Sheet FS-095-01.

27. Wess, J., et al, 2004, “Asphalt (Bitumen), C oncise International Assessment Document 59, World Health Organization.”

17