APPENDIX A
MERCURY CONCENTRATIONS IN FUELS
This appendix provides the basis of the assumptions in this study on the mercury
concentrations of fossil and non-fossil fuels.
FOSSIL FUELS
This section describes this study’s assumptions on mercury concentrations for coal, oil,
and natural gas and explains the methodologies used to arrive at them.
Coal
Mercury concentrations in different types of coal in different regions of the country were
calculated through the following four steps:

Collected data on mercury concentrations in different types of coal by State. The three
coal types are bituminous, subbituminous, and lignite.

Made adjustments in mercury concentrations for coals in those States, where companies
would clean them and EPA had data on their mercury concentrations prior to cleaning.

Converted data on mercury concentrations that were expressed in parts per million weight
(ppmw) to pounds of mercury per trillion Btus of heat content of each coal (lbs /TBtus).

Conducted cluster analysis to group the same types of coals with similar mercury
concentrations together to arrive at an average estimate of the mercury concentrations in
that set of coals.
These steps are described below in detail.
Compilation of State Data
EPA relied primarily on the EPA’s Report to Congress on hazardous air pollutant (HAP)
emissions (HAP Study; EPA, 1998a).1 The mercury concentrations in coal used for the purposes
of the IPM mercury emissions analyses are reported in Exhibit A1. For bituminous coals from
Illinois and Colorado, mercury concentrations pertain to as-shipped coals, which are deemed
cleaned prior to shipping.
EPA.1998a. Study of Hazardous Air Pollutant Emissions from Electric Utility Steam Generating Units – Final
Report to Congress.Volumes I and II. Office of Air Quality Planning and Standards. U.S. Environmental Protection
Agency. EPA-453/R-98-004a & -004b. February 1998.
1
A-1
Coal Cleaning
Bituminous coals from selected States are cleaned to meet customer specifications for
heating value, and ash and sulfur content. EPA estimates that the average mercury reduction due
to coal washing is 21 percent in the HAP Study. In the IPM mercury analyses, the Agency
assumed a 21 percent reduction for bituminous coals shipped from 14 States (i.e., Alabama,
Iowa, Indiana, Kansas, Kentucky, Maryland, Missouri, Ohio, Oklahoma, Pennsylvania,
Tennessee, Utah, Virginia, and West Virginia). Consistent with the HAP Study, no mercury
removal factor was applied to lignite and subbituminous coals, nor to bituminous coals shipped
from Arizona, Montana, New Mexico, and Wyoming.
Mercury Concentrations in IPM
Mercury concentrations of coal (i.e., amount of mercury per unit of heat content, which is
expressed as “lbs/TBtu”) differs by type, based on their initial mercury concentrations on a parts
per million weight (ppmw) basis and heat content.2 EPA estimated the mercury concentrations
in coals for use in IPM using the following formula:
Mercury concentration of coal in ppmw * lbs to short ton conversion factor / heat content of coal * MMBtu
to Trillion Btu conversion factor.3
The mercury concentrations reported in column 5 of Exhibit A1 pertain to the average mercury
concentrations of coal.4
There can be substantial variation in the mercury concentrations of coal from different
mines in a State and in different coal seams at the same mine. However, Exhibit A1 shows that
certain types of coals in various regions of the country do have average concentrations of
mercury that differ markedly from the average concentrations of mercury of other types of coal.
In the same coal class, there are also marked differences in average mercury concentrations
between States.
2
The different sulfur grades of coal that are used in the IPM mercury analyses include the following six sulfur
grades of bituminous coals, three sulfur grades of subbituminous coals, and two sulfur grades of lignite coals: Low
Sulfur Eastern Bituminous (BA), Low Sulfur Western Bituminous (BB), Low Medium Sulfur Bituminous (BD),
Medium Sulfur Bituminous (BE), Medium High Sulfur Bituminous (BF), and High Sulfur Bituminous (BG); Low
Sulfur Subbbituminous (SB), Low Medium Sulfur Subbituminous (SD), and Medium Sulfur Subbituminous (SE);
and Low Medium Sulfur Lignite (LD) and Medium High Sulfur Lignite (LF).
3
The details of this calculation are: (x lbs of Hg / 10 6 lbs of coal) * (2,000 lbs / ton) * (ton / y MMBtu) * (10 6
MMBtu/TBtu) where, x is the mercury concentration reported in the HAP Study and y is the heat content of coal,
derived from IPM.
4
The average mercury concentration of coal for a State indicates simple average mercury concentration of various
sulfur grades of a particular type of coal shipped from that State.
A-2
Exhibit A1
Average Mercury Concentrations in Coal by State of Origin and Coal Type
State of Origin
Alabama
Arkansas2
Arizona2
Colorado
Iowa
Illinois
Indiana
Kansas
Kentucky
Maryland
Missouri
Montana
New Mexico2
Ohio
Oklahoma
Pennsylvania
Tennessee2
Utah
Virginia
West Virginia
Wyoming2
Alaska
Montana
New Mexico
Washington
Wyoming
Colorado2
Louisiana
Montana
North Dakota
Texas
Coal Type
Bituminous
Bituminous
Bituminous
Bituminous
Bituminous
Bituminous
Bituminous
Bituminous
Bituminous
Bituminous
Bituminous
Bituminous
Bituminous
Bituminous
Bituminous
Bituminous
Bituminous
Bituminous
Bituminous
Bituminous
Bituminous
Subbituminous
Subbituminous
Subbituminous
Subbituminous
Subbituminous
Lignite
Lignite
Lignite
Lignite
Lignite
Original Average
Mercury
Concentrations
(ppmw)1
0.19
0.17
0.07
0.07
0.19
0.08
0.11
0.19
0.15
0.42
0.17
0.09
0.06
0.22
0.17
0.29
0.15
0.04
0.14
0.16
0.08
0.07
0.09
0.06
0.06
0.08
0.18
0.19
0.12
0.13
0.19
Final Average
Mercury
Concentrations
(ppmw)
0.15
0.13
0.07
0.07
0.15
0.08
0.09
0.15
0.12
0.33
0.13
0.09
0.06
0.17
0.13
0.23
0.12
0.03
0.11
0.13
0.08
0.07
0.09
0.06
0.06
0.08
0.18
0.19
0.12
0.13
0.19
Final Average
Mercury
Concentrations
(lbs of Hg per
Trillion Btu)
11.91
21.84
6.45
5.89
14.70
7.18
7.96
13.18
9.92
26.58
12.04
8.38
5.76
14.94
10.76
18.13
9.63
2.87
8.65
10.11
8.13
9.32
9.97
7.06
7.40
9.35
29.81
28.04
17.87
19.73
31.51
Notes: 1 ppmw = parts per million weight = lbs. of mercury / million lbs. of coal.
2
For Tennessee, the mercury concentration was obtained from another EPA study (EPA, 1998b), 5 as the HAP Study does not report this
information. For Arkansas, the mercury concentration of bituminous coal was assumed to be the same as that for bituminous coal from
Oklahoma. Additionally, for Arizona, New Mexico, and Wyoming, it was assumed that the mercury concentrations of bituminous coal were the
same as the mercury concentrations of subbituminous coal from those states. For lignite coal from Colorado, the average mercury concentration
of all lignite coals, as reported in the HAP Study, was used.
Source: EPA
5
EPA, Analyzing Electric Power Generation under the CAAA, March 1998.
A-3
Cluster Analysis
Mercury concentrations in coal vary widely across different types in different States. The
wide range of mercury concentrations for each grade of coal across supply regions was divided
into similar groups using “clustering” analysis for the purposes of the IPM mercury analyses.
The clustering analysis places objects into groups or clusters, such that the data in a
given cluster tend to be similar to each other, and that they are dissimilar to the data in other
clusters. In other words, the clustering analysis minimizes the variance (i.e., the square of the
average deviation of the data from their arithmetic mean) of the data within each cluster. 6 The
clustering analysis was performed to minimize the complexity involved in incorporating the wide
range of mercury concentrations of each individual sulfur grade and type of coal into the IPM
input file. The clustering analysis was performed through the following two steps:

First, the number of clusters of mercury concentrations within each sulfur grade of coal
was determined based on the range of mercury concentrations for that sulfur grade of coal
and the extent of its supply.

Second, the SAS clustering analysis program was used to group the mercury
concentrations of each sulfur grade of coal across various supply regions into a specified
number of clusters, such that the variance of mercury concentrations within each coal
cluster is minimized.
For example, mercury concentrations of Low Sulfur Western Bituminous (BB) coals
across nine supply regions are in the range of 2.61 to 8.12 lbs of Hg/TBtu. Based on the amount
of BB coal supplied and the range of its mercury concentrations, it was determined that BB coal
would be divided into two clusters. Then, using the SAS clustering analysis program, BB coals
were divided into a BB1 cluster, with mercury concentrations not exceeding 5.5 lbs of Hg/TBtu,
and into a BB2 cluster, with mercury concentrations exceeding 5.5 lbs of Hg/TBtu.
Exhibit A2 shows the clusters of various sulfur grades of coal and their mercury
concentrations that were developed and analyzed in this effort. EPA assumed in IPM that the
coals identified in the first column had the average mercury concentrations of each cluster
shown in the columns on the far right in Exhibit A2. For example, the mercury concentration
of BA coals from Alabama is estimated to be approximately 11.87 lbs of Hg/TBtu. Exhibit A2
indicates that this coal falls into the second cluster (i.e., BB2), as its mercury concentration is
greater than 10.5 lbs of Hg/TBtu. Therefore, for the purposes of calculating mercury emissions
using IPM, the average mercury concentration of the BB2 cluster (=11.87 lbs of Hg/TBtu) was
used for all BB2 coals.
6
In other words, it is a measure of dispersion of the data from their arithmetic mean.
A-4
Exhibit A2
Coal Clusters and Average Mercury Concentrations
Coal Type by Sulfur
Grade
No. of
clusters
(Lbs of Hg per Trillion Btu)
Range of mercury
Average mercury
concentration within each
concentration within each
coal cluster
cluster
Cluster Cluster Cluster Cluster Cluster Cluster
#1
#2
#3
#1
#2
#3
> 10.5
-9.62
11.87
- 10.5
Low Sulfur Eastern
Bituminous (BA)
2
Low Sulfur Western
Bituminous (BB)
2
 5.5
> 5.5
--
2.79
6.14
--
Low Medium Sulfur
Bituminous (BD)
3
 7.0
> 7.0 to
 14.0
> 14.0
5.22
9.64
17.89
Medium Sulfur
Bituminous (BE)
3
 9.0
> 9.0 to
 13.0
> 13.0
7.98
10.01
17.83
Medium High Sulfur
Bituminous (BF)
3
 13.0
> 13.0 to
 20.0
> 20.0
9.55
18.10
26.58
High Sulfur
Bituminous (BG)
3
 8.0
> 8.0 to
 14.0
> 14.0
7.43
10.38
15.91
Low Sulfur
Subbituminous (SB)
1
0
--
--
9.46
--
--
Low Medium Sulfur
Subbituminous (SD)
1
0
--
--
8.84
--
--
Medium Sulfur
Subbituminous (SE)
1
0
--
--
9.37
--
--
Low Medium Sulfur
Lignite (LD)
1
0
--
--
23.80
--
--
Medium High Sulfur
Lignite (LF)
2
 25.0
> 25.0
--
19.73
31.31
--
Notes: -- = not applicable.
A-5
Oil and Natural Gas
EPA used data from the HAP study to develop average mercury concentrations of oil and
natural gas (see Exhibit A3). The Agency estimated mercury concentrations in oil and natural
gas for use in the IPM analysis in the following manner:

Oil - The mercury concentration of 0.0092 ppmw was converted to a mercury
concentration in pounds per TBtu using the following formula:
Mercury concentration * lbs to gallon conversion factor / heat content * Btu to
Trillion Btu conversion factor
= (0.0092 lbs / 106 lbs) * (7.88 lbs / gal) * (gal / 150,000 Btu) * (1012 Btu /TBtu)
= 0.483 lbs/TBtu.

Natural gas - The mercury concentration of 0.0000024 mg/cm was converted to a
mercury concentration in pounds per TBtu using the following formula:
Mercury concentration * cubic meter (cm) to cubic feet (cft) conversion factor /
heat content * Btu to Trillion Btu conversion factor * mg to kg conversion factor
* kg to lbs conversion factor
= (2.4 * 10-6 mg/cm) * (0.027 cm/cft) * (cft/1,035 Btu) * (1012 Btu/TBtu)
* (kg/106 mg) * (2.21 lbs/kg)
= 0.000138 lbs/TBtu.
Exhibit A3
Average Mercury Concentrations in Oil and Natural Gas
Fuel Type
Oil
Natural Gas
Unit for Mercury
Concentration in
the HAP Study
Ppmw
mg/cm
Mercury
Concentration in
the HAP Study
0.0092
0.0000024
Mercury Concentration
In IPM
(lbs of Hg/TBtu)
0.483
0.00014
Notes: ppmw = parts per million weight = lbs. of mercury / million lbs. of oil.
Source: EPA
NON-FOSSIL FUELS
The non-fossil fuels covered in this study are wood waste, municipal solid waste, and
geothermal resources. The source of data on the mercury concentrations in these fuels is EPA’s
Mercury Study Report to Congress. Volume II: An Inventory of Anthropogenic Mercury
Emissions in the United States, December 1997 (Mercury Study).7 Exhibit A4 reports the
assumptions on the mercury concentrations of non-fossil fuels that EPA uses in the IPM analysis.
Details on how EPA prepared these estimates are provided below.
7
EPA. 1997. Mercury Study Report to Congress. Volume II: An Inventory of Anthropogenic Mercury missions in the
United States. Office of Air Quality Planning and Standards and Office of Research and Development. U.S.
Environmental Protection Agency. EPA-452/R-97-004. December 1997.
A-6
Exhibit A4
Average Mercury Concentrations of Non-Fossil Fuels
Fuel Type
Wood Waste
Municipal Solid Waste
Geothermal Resource
(lbs of Hg per TBtu)
Average Mercury Concentration in IPM
0.57
71.85
4.08
Wood Waste
Consistent with the Mercury Study, the mercury concentration of wood waste is assumed
to be 0.0000052 lbs per ton. Also, based on the same study, the heat content of wood waste has
been assumed to be 4,560 Btu/lb. Based on these estimates, the mercury concentration in wood
waste was calculated for use in the IPM analysis as follows:
= (5.2*10-6 lbs/ton) * (lbs/4,560 Btu) * (ton/2,000 lbs) * (1012 Btu/TBtu)
= 0.57 lbs/TBtu.
Municipal Solid Waste
Municipal Waste Combustors (MWCs) are subject to the New Source Performance
Standards for MWCs, which require MWCs to reduce mercury emissions by about 90 percent.
For the purposes of the IPM mercury analyses, EPA assumed that MWCs would achieve this
reduction by the year 2005 and mercury concentrations in the MSW are assumed to be 0.08
mg/dscm. Based on this estimate, the mercury concentration of municipal waste was calculated
for use in the IPM analysis as follows:
= (20.9/13.9) * (0.08 mg/ dscm) * (9,570 cft/MMBtu) * (cm/35.31 cft) * (106
MMBtu/TBtu) * (Metric Ton/109 mg) * (1.102 tons/Metric ton) * (2,000 lbs/ton)
= 71.85 lb/TBtu.
Geothermal
EPA estimates that the average mercury emissions factor for geothermal plants is
estimated to be 0.00012 lbs/MWh. Assuming a heat rate of 29,425 Btu/KWh, the mercury
concentration of a geothermal resource was calculated for use in the IPM analysis in the
following way:
= (0.00012 lbs/MWh) * (MW/1,000KW) * (KWh/29,425 Btu) * (1012 Btu/TBtu)
= 4.078 lbs/TBtu
A-7