Document ID: EPA-HQ-RCRA-2008-0329-0242
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2009-01-02T05:00Z

Materials Characterization Paper

In Support of the

Advanced Notice of Proposed Rulemaking –

Identification of Nonhazardous Materials That Are Solid Waste

Coal Refuse

December 16, 2008

=================================================================

1.	Definition of Coal Refuse

This paper focuses on coal refuse that is a by-product of coal mining
(mining rejects).  Coal refuse is generally defined by a minimum ash
content combined with a maximum heating value, measured on a dry basis. 
(ARIPPA, p. 1 and EPA 2002, p. 2-2). Coal refuse mining rejects are a
low BTU-value material generated by the coal mining process.  The
material consists primarily of non-combustible rock, with some attached
carbon material that cannot be effectively separated.  Large volumes of
these materials were accumulated at mining sites from the time mining
first began in the Appalachians through the late 1970s.  Beginning in
the late 1970s, laws were enacted that, for the first time, required
stabilization and reclamation of mining sites, including coal refuse
disposal piles and fills (ARIPPA, p.1).  Current mining operations
continue to generate the material.  Mining rejects are referred to by
various names, including: “gob” (garbage of bituminous) or
“boney” in the bituminous coal mining regions of western
Pennsylvania, West Virginia and elsewhere; and “culm” in the eastern
Pennsylvania anthracite region.  Coal refuse piles also may be referred
to as slate dumps (Energy Justice 2007, p.1; WPCAMR 2001, p.2; NRC 2006,
p.16).  

2.	Annual Quantities of Coal Refuse Generated and Used

Sectors That Generate Coal Refuse:

Coal Mining Rejects are generated by NAICS industry sector 212111 -
Bituminous Coal and Lignite Surface Mining, 212112 - Bituminous Coal
Underground Mining, and 212113 - Anthracite Mining.  The U.S. Department
of Energy categorizes the locations of these industries into three
regions:  

Appalachian Region, which includes the states of Alabama, Kentucky
(eastern), Maryland, Ohio, Pennsylvania, Tennessee, Virginia, and West
Virginia; 

Interior Region, which includes the states of Arkansas, Illinois,
Indiana, Kansas, Kentucky (western), Louisiana, Mississippi, Missouri,
Oklahoma, and Texas; and 

Western Region, which includes the states of Alaska, Arizona, Colorado,
Montana, New Mexico, North Dakota, Utah, Washington, and Wyoming (USDOE
2007b, p.14).  

Quantities and Prices of Coal Refuse Generated: 

Comprehensive national data concerning current generation rates of
mining rejects were not identified in the course of this review.  In
2007, however, the amount of coal produced at U.S. coal mines reached an
all-time high of 1,145.0 million short tons; this production data
includes quantities extracted from surface and underground mines, and
normally excludes secondary materials removed at mines or associated
preparation plants (USDOE 2007a).  Thus, the amount of raw mining
product is higher than this 1,145.0 million short ton total.  The amount
of mining reject resulting from this production is uncertain, but up to
50 percent of the raw mined product may end up as refuse depending on
the rock and impurities in the coal (VCE 1996). Considering this 50
percent generation estimate with the 2007 coal production number,
results in an estimate that up to 1,145 million tons of coal reject may
have been generated in 2007 (i.e., 50 percent of raw mined product is
saleable product, while 50 percent is rejects).  As an example of
specific data from one state, fifteen million tons of mining reject are
generated annually in Virginia (VCE 1996). 

Information on the price of coal refuse is limited, but can be expected
to compare favorably with “virgin” energy sources in the
applications where it is used.

Trends in Generation of Coal Refuse:  

Generation of coal refuse correlates with the production and use of
coal.  According to the DOE’s Annual Energy Outlook 2007 with
Projections to 2030, coal production is projected to increase in coming
decades, particularly in the Powder River Basin of Wyoming.  From 2005
to 2030, production in the Powder River Basin is projected to grow by
289 million tons.  The Rocky Mountain, Central West, and East North
Central regions are projected to show the largest increases in coal
demand, by about 100 million tons each, from 2005 to 2030.  Increasing
coal use for electricity generation at existing plants and construction
of a few new coal-fired plants lead to forecasted annual production
increases that average 1.1 percent per year from 2005 to 2015.  The
forecasted growth in coal production is stronger from 2015 to 2030,
averaging 1.8 percent per year, as new coal-fired generating capacity is
added and several coal-to-liquids (CTL) plants are brought on line
(USDOE 2007b).  Overall, the generation of coal refuse will likely
increase as the demand for coal-based energy grows; however, it is
unclear how this increase will affect recapturing of existing coal
refuse from stockpiles. 

3.	Uses of Coal Refuse

Combustion Uses of Coal Refuse:  

There are 18 coal refuse plants (Fossil fuel electric power generation -
NAICS 221112), and 13 more that use it as a secondary fuel, with
bituminous coal as their primary fuel.  Fourteen of the 18 coal refuse
plants are in Pennsylvania, three are in West Virginia, and one is in
Utah.  Seventeen more plants have been proposed in Pennsylvania, West
Virginia, Kentucky, Indiana, Illinois, Colorado, and Virginia (Energy
Justice 2007, p.1).

According to the Anthracite Region Independent Power Producers
Association (ARIPPA), from 1988 to the end of 2003, coal refuse plants
in Pennsylvania used 88.5 million tons of coal refuse, mostly from
“legacy” refuse piles.  ARIPPA’s records show that the plants in
the Commonwealth burn an average of about 7.5 million tons of coal
refuse per year as fuel, mostly from “legacy” coal refuse piles
(PADEP 2004a, p.2).

The type of process used for the combustion of mining rejects is
circulating fluidized bed (CFB) combustion (also known as fluidized bed
combustor (FBC) boiler technology) (Energy Justice 2007, p.1). CFB is an
integrated technology for reducing sulfur dioxide (SO2) and NOx
emissions during the combustion of coal.  For the CFBs currently in use
in all sectors, coal is the primary fuel source, followed by biomass and
coal refuse. The heat input capacities of all industrial, commercial,
and institutional (ICI) CFB units generally range from 1.4 to 1,075
MMBtu/hr. (EPA 2004, p.2-7).

Non-Combustion Uses of Coal Refuse

Granular Base: Coarse coal refuse can be used as aggregate in granular
base applications. Burnt coal refuse (red dog) is also a suitable
granular base material.  Proper compaction of coarse coal refuse to its
maximum dry density is necessary to achieve stability within a pavement
structure. Fine coal refuse slurry has little or no load carrying
capability and is, therefore, unsuitable for use as a construction
material (TFHRC post-1994, p.1). 

Coal refuse has been successfully used in cement stabilized base
applications in Europe. The success of this material for use in this
application is reportedly dependent on proper compaction. There has been
occasional use of coal refuse in Alabama, Kentucky, Virginia, and West
Virginia as an alternative material for bases and subbases (TFHRC
post-1994, pp.1-2). 

Mine Reclamation Projects: Ash leftover from combustion in a CFB boiler
is alkaline and used for mine reclamation projects.  The ash is often
hauled back to the same gob pile site, where it can be mixed with soils
impacted by acid mine drainage around abandoned mines to neutralize
acidity and immobilize heavy metals.  The Commonwealth of Pennsylvania
has certified CFB ash for beneficial use in mining reclamation projects,
and the Department of Environmental Protection regulates and routinely
tests it (WPCAMR post-2001, p.2).  Following combustion of gob in the
CFB boiler, the solids that remain are called ash.

Quantities of Coal Refuse Stockpiled/Stored

All mining rejects are stockpiled.  Comprehensive national data
concerning the volume of legacy mining rejects was not identified during
the course of this review.  In Pennsylvania, however, historically,
(i.e., from the early 1800s to the 1970s) mine rejects were placed in
piles in the state's coal regions until laws were enacted in the late
1970s that required the coal companies to reclaim the sites that they
mined.  According to one source, upwards of 2.4 billion tons of coal
refuse had been dealt with in this manner in Pennsylvania by that time
(Energy Justice 2007, p.1).  Another source indicates that Pennsylvania
had an estimated 8,529 acres of “legacy” coal refuse piles
throughout the state as of 2003.  These piles include at least 258
million tons of coal refuse (PADEP 2004a).  In addition, according to
ARIPPA, from 1988 to the end of 2003, coal refuse plants in Pennsylvania
consumed 88.5 million tons of the material, mostly from “legacy”
refuse piles.  ARIPPA’s records show that the plants in the
Commonwealth burn an average of about 7.5 million tons of coal refuse
per year, mostly from “legacy” coal refuse piles (PADEP 2004a, p.2).

4.	Management and Combustion Processes

Types of Combustion Units: 

Circulating fluidized bed combustion units and pulverized coal power
plants are the only units that use any coal refuse.

Sourcing information: 

Sources of mining rejects include coal refuse or “gob/culm piles”.

Processing Information:  

In general, the material is hauled from mining areas (i.e., gob and culm
piles) to coal-fired power plants, crushed to a top size of
approximately five millimeters, and then burned in circulating fluidized
beds for energy.  Along with the fuel, crushed limestone is injected
into the bottom of the combustion chamber where the calcium carbonate in
the limestone is converted into calcium oxide.  The calcium oxide then
reacts with the sulfur in the coal refuse, thereby reducing the sulfur
oxide emissions.  The heavier fuel and limestone particles that cannot
be retained in the circulating fluidized bed drop to the bottom of the
chamber.  This burned fuel, known as bottom ash, is removed from the
combustion chamber.  (PADEP 2004b, Ch 1, pp. 3-4).  Ash leftover from
CFBs may be hauled back to the same gob/culm pile site, where it can be
mixed with soils around abandoned mines to neutralize acidity and
immobilize heavy metals (WPCAMR post-2001, p.2).

  

Changes in Technology to Improve Use of Coal Refuse in Combustion:  

As noted, the advent of circulated fluidized bed (CFB) combustion
boilers, along with higher fuel costs, has facilitated the combustion
uses of coal refuse.  In addition, certain technology advancements are
in use or development that may serve to further improve the application
of coal refuse in combustion:  

CSIRO-Liquatech hybrid coal and gas turbine system, developed in
Australia, harnesses existing technologies in a 1.2 megawatt hybrid coal
and gas turbine system that burns coal refuse and methane gas to
generate electricity.  The electricity can either be used to power a
mine’s operations or be returned to the grid for general consumption
(CSIRO 2002, p.1).  

Radar Acquisitions Corp. is in the process of developing an engineered
solid fuel (Re-Fuel™) for utilities.  The primary component of
Re-Fuel™ is coal refuse (gob piles and coal slurry pond material); the
secondary component is biomass (i.e. agricultural material or sawdust). 
The goal of the RPS Fuels™ technology is to convert these two
materials into a product that looks and acts like coal, but burns more
efficiently and with reduced stack emissions. (Radar, p.1).

State Status of Combustion as Beneficial Use:  

There are currently three states that have power plants that burn coal
refuse as fuel (Pennsylvania, West Virginia, and Utah).  There are
currently five additional states that are proposing to build power
plants that will burn coal refuse:  Kentucky, Indiana, Illinois,
Colorado, and Virginia.  

5.	Coal Refuse Composition and Impacts

Composition of Coal Refuse

The Btu value for this material is 6,000 to 9,500 Btu per pound (NRC,
2006).  Nationally, this material has an average of 60 percent of the
BTU value of normal coals (Energy Justice 2007, p.1). The ash contents
of coal refuse is high: according to an ARIPPA-sponsored study, twelve
Pennsylvania plants using coal refuse as a key ingredient of their fuel,
burned over 8 million tons/year of refuse coal and generated in the
process approximately 5 million tons of ash (Earthtech 2000, Vol. 1, p.
iv).

Mining rejects have a higher concentration of mercury than normal coals.
 In West Virginia and nationally, gob has 4 times more mercury than
bituminous coal.  In Pennsylvania, gob has 3.5 times more mercury than
bituminous coal.  Culm has 19 percent more mercury than anthracite coal.
 Bituminous rejects also have higher levels of sulfur.  Data on other
metals in the material is sparse, but single metals tests on
Pennsylvania culm and gob show both to have about four times more
chromium and three times more lead (Energy Justice 2007, p.1) ), and the
content of arsenic is relatively elevated as well (Coleman and Bragg,
1990, in Earthtech, 2000, Vol. 1, pp. 15-16).

Impact Information

As noted, the typical process used for the combustion of mining rejects
is circulating fluidized bed (CFB) combustion (Energy Justice 2007,
p.1). CFB is an integrated technology for reducing sulfur dioxide (SO2)
and NOx emissions during the combustion of coal. In a typical CFB
boiler, crushed coal and inert material (sand, silica, alumina, or ash)
and/or a sorbent (limestone) are maintained in a highly turbulent
suspended state by the upward flow of primary air from the windbox
located directly below the combustion floor. This fluidized state
provides a large amount of surface contact between the air and solid
particles, which promotes uniform and efficient combustion at lower
furnace temperatures than conventional coal-fired boilers. Once the hot
gases leave the combustion chamber, they pass through the convective
sections of the boiler, which are similar or identical to components
used in conventional boilers.  For the CFBs currently in use in all
sectors, coal is the primary fuel source, followed in descending order
by biomass, coal refuse, and municipal waste. The heat input capacities
of all ICI CFB units generally range from 1.4 to 1,075 MMBtu/hr (EPA
2004, pp.2-7). 

Concerning impacts related to emissions from this combustion process,
the Pennsylvania Department of Environmental Protection (PADEP) required
the owners of a Pennsylvania bituminous coal refuse fired facility to
conduct extensive air toxics emissions stack testing to support its
request to burn a 10 percent mixture of coal tar contaminated soil in
combination with normal coal refuse. The coal refuse facility shows
lower emissions for all of the toxic pollutants compared to a typical
pulverized coal combustor. The dioxin levels were approximately 4 times
lower, while most metals were about half, with the exception of mercury,
which was 10 times lower per gigawatt-hour generated (PADEP post-2004,
p.2).  Based on stack testing of two CFB combustion plants, 99.7% to
99.8% of the mercury was captured in the ash (Earthtech, 2000, Vol. 1,
p. vi). According to the same source (Earthtech, 2000, Vol.1, p. 1),
there are several reasons for the general low emission levels of trace
metals such as As, Cd, Cr, Hg, Pb, Ni and Se in the fluidized bed
combustion process. Those include the significantly lower combustion
temperatures (800-950 0C) as compared to pulverized coal combustion
boilers (1200-1540 0C), resulting in much longer circulation of the ash
particles in the boiler, and allowing for more effective fixation of
these metals; capture of ash in a baghouse rather than by electrostatic
precipitator; and the addition of limestone which enhances metal
fixation unto the ash.     

The culm (reject anthracite coal) combusting facilities represent the
majority of the coal refuse facilities in Pennsylvania and the data
submitted to the Department shows that these facilities have been
achieving a NOx emissions level of 0.15 lbs/MMBtu. In comparison, a
typical pulverized coal facility without add-on selective catalytic
reduction (SCR) controls, which is presently the majority of pulverized
units, would emit NOx in the 0.3 to 0.5 lb/MMBtu range.  This continuous
emissions monitoring (CEM) data also shows that some of the coal refuse
facilities have been achieving an SO2 emissions rate of 0.20 to 0.25
lbs/MMBtu range using limestone injection. The pulverized coal-fired
boilers typically emit in the range of 2 to 3 lbs. of SO2 per MMBtu. The
six Pennsylvania pulverized coal-fired units with SO2 scrubbing operate
in the 0.1 to 0.4 lbs. of SO2 per MMBtu range (PADEP post-2004, p.2).

Pennsylvania coal refuse burning facilities are lower emitters of both
NOx and SOx than the typical coal-fired utilities. However, it should
also be noted that an SO2 emission rate of 0.1 lbs/MMBtu is achievable
for a newly built pulverized coal-fired unit that would be required to
install an SO2 scrubber under an SO2 Best Available Control Technology
(BACT) determination. Therefore, newly constructed electric generating
combustors of either coal refuse or coal would emit at very comparable
levels, because both would be employing very similar BACT for all
pollutants. (PADEP post-2004, p.2).

Impacts related to the use of coal refuse are discussed qualitatively
below.  Note that a further discussion of the uses of coal combustion
products (CCPs) as ingredients is provided in the CCP Materials
Characterization Paper.

Other Impacts Related to Mining Rejects:  

The potential benefits of returning suitable FBC ash to abandoned or
active mine lands for use in reclamation include:

The alkaline nature and encapsulating ability of the material make it
useful for some mine reclamation applications.  In particular,
reclaiming coal refuse piles without the benefit of adding FBC ash does
less to address the often-severe water quality problems that emanate
from some of the piles.

The reclamation of abandoned mine land (AML) with FBC ash is often
privately funded, freeing up state and federal government AML resources
for other applications. 

The ash from FBC plants has chemical and physical properties that limit
the potential for the ash itself to become a source of environmental
contamination (Earthtech, 2000, Vol 1, pp. v-vi; PADEP 2004b, Ch. 1,
pp.6-7). 

Reclaiming AML with ash serves to eliminate the safety hazard of
abandoned mine highwalls and cropfalls.  

Additional Avoided Impacts:  

Use of coal refuse as a replacement for traditional primary fuels
eliminates the environmental impacts associated with extraction and
processing of the traditional fuels. Exhibit 1 lists the quantities of
emissions for mining reject combustion as reported by the Pennsylvania
DEP and the quantities of cradle-to-gate emissions and combustion
emissions for coal as reported by typical industrial boilers in the late
1990s. Note that there may be impacts associated with the previously
described processing of coal refuse in preparation for combustion not
considered here, and there may be alternative uses (e.g., aggregate,
mine reclamation) that are environmentally preferable to combustion.

Furthermore, use of coal refuse as a fuel serves the important benefit
of removing the piles of gob and culm.  The piles can be a fire hazard
and a source of surface and ground-water pollution.  

Exhibit 1:  Emissions from Combustion of Coal Refuse and Extraction and
Combustion of Traditional Coal

Pollutant	Coal Refuse	Coal

	Combustion	Combustion	Combustion plus Upstream

	---------- Lb./MMBtu ----------

Criteria Pollutants

PM2.5	-	-	-

PM10	-	0.054	0.054

PM, unspecified	-	-	0.246

NOx	0.15	0.482	0.504

VOCs	-	0.006	0.014

SOx	0.20 - 0.25	1.446	1.469

CO	-	0.068	0.085

Pb	-	8.93x10-6	9.19x10-6

Hg	-	2.05x10-6	2.14x10-6

Sources:

PADEP post-2004, p.2; Franklin Associates 1998.

Note:

“-” signifies data not available; may equal zero.

The emission information presented in this table is derived from Life
Cycle Inventory (LCI) data, as compiled by Franklin Associates.   LCI
data identifies and quantifies resource inputs, energy requirements, and
releases to the air, water, and land for each step in the manufacture of
a product or process, from the extraction of the raw materials to
ultimate disposal. The LCI can be used to identify those system
components or life cycle steps that are the main contributors to
environmental burdens such as energy use, solid waste, and atmospheric
and waterborne emissions.  Uncertainty in an LCI is due to the
cumulative effects of input uncertainties and data variability.  

There are several life cycle inventory databases available in the U.S.
and Europe.  For this paper, we applied the most readily available LCI
database that was most consistent with the materials and uses examined.
These LCI data rely on system boundaries as defined by Franklin
Associates, as described in the documentation for this database,
available at:   HYPERLINK
"http://www.pre.nl/download/manuals/DatabaseManualFranklinUS98.pdf" 
http://www.pre.nl/download/manuals/DatabaseManualFranklinUS98.pdf .  

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 This amount does not include the recovery of coal refuse, which was 0.8
million short tons in 2007.

 For example, the Ministry of Transport in the United Kingdom permits
the use of incinerated coal refuse (well-burnt, nonplastic shale) as a
granular subbase material in Ministry controlled road work (TFHRC,
post-1994, p.2).

 The Pennsylvania Department of Transportation has rejected anthracite
refuse usage as aggregate for base and subbase courses because of high
percent dissolution losses in the sodium sulfate (soundness test).  West
Virginia is evaluating the use of coal refuse as subbase material
(TFHRC, post-1994, p.2).

 CFB Ash can be used for other kinds of reclamation projects.  For
example, one project will use CFB ash injected into the partially
flooded underground voids of an abandoned mine to mitigate acid mine
drainage that currently breaks out on the surface (WPCAMR).

 See the CCP Materials Characterization Paper for further information on
CCP landfill volumes.

 Based on the sources consulted in the development of this document,
brokers or traders do not appear to be involved in sourcing the waste
products to the power plants.  It appears the utilities/power plants are
supplying themselves with the waste pile materials.

 Note that this information represents the results of preliminary
research; we have not performed an exhaustive investigation of state
activities and regulations for all states concerning coal refuse.

Coal Refuse

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