###### **Utility MACT for Coal- and Oil-Fired Electric Utility Boilers**

Recommendations by:

Clean Air Task Force, Environmental Defense, National Environmental
Trust, National Wildlife Federation, Natural Resources Defense Council

Submitted September 9, 2002 (revised September 20, 2002)

######## MERCURY MACT FOR COAL-FIRED ELECTRIC GENERATING UNITS

#### 

#### [Subcategories]{.underline}

***Recommendation:*** Three "boiler type" subcategories are recommended:
fluidized bed combustors, conventional boilers, and coal gasification.

**Rationale:** Based on the information provided to the Utility Working
Group there appears justification for treating conventional boilers
differently than fluidized bed combustors and coal gasification units
because they are uniquely different systems.

Other subcategories are not appropriate, especially subcategorizing by
fuel type, because fuel type does not represent a "class, type or size"
distinction, as defined under Section 112 of the Clean Air Act.

### B. Emission standards

# a. New sources

***Recommendation:*** We recommend that for new sources, the MACT for
mercury should reflect the best performing unit in each boiler type
subcategory, except for coal gasification units. For these units, given
that cost-effective technology is commercially available and has been
demonstrated in industrial applications, a 95% control level or greater
for these units is appropriate.

# b. Existing sources

***Recommendation:*** We recommend an output based emission rate
standard, calculated using the following input based rates for each of
the proposed boiler type subcategories and the boilers' specific heat
rates efficiencies:

+-----------------------------------------+----------------------------+
| FBC boilers                             | 0.19 lbs/TBtu              |
|                                         |                            |
| (averaged over 4 units---the 5^th^ unit |                            |
| appears to be an outlier and thus       |                            |
| should not be included)                 |                            |
+-----------------------------------------+----------------------------+
| Conventional boilers                    | 0.21 lbs/TBtu              |
|                                         |                            |
| (averaged over 7 units)                 |                            |
+-----------------------------------------+----------------------------+
| Coal gasification                       | .27 lbs/TBtu (95% control) |
|                                         |                            |
| (beyond-the-floor)                      |                            |
+-----------------------------------------+----------------------------+

### *Rationale for emissions standards for FBC and coal gasification units:* For fluidized bed combustors, four of the five "MACT-floor" units measured mercury emissions ranging from 0.08 to 0.46 lbs/TBtu; the fifth unit measured emissions at 3.97 lbs/TBtu (it was equipped with a CS-ESP whereas all the other units had baghouses installed.). Setting a standard at 0.95 lbs/TBtu (the average over the five FBC units measured) would not have the desired effect that a MACT standard should have: It would allow more mercury to be emitted than is currently measured at existing units. For this reason, a standard more stringent than the 0.95 lbs/TBtu would be appropriate. Averaging the emissions over the top four units would be one possibility, which would result in a MACT floor of 0.19 lbs/TBtu, or 92% reduction.

For coal gasification units, demonstrated cost-effective technology is
commercially available that would allow these units to get significant
mercury reductions. Carbon filter beds for metals cleanup from syngas
have already been demonstrated on industrial gasification units. In
addition, the U.S. Department of Energy has already completed an
engineering analysis for installation of a carbon filter bed at Tampa
Electric's Polk Station that would achieve a 99% mercury removal at a
very reasonable cost. A 95% beyond the floor control level for coal
gasification units is appropriate given the likely ease with which units
can meet this level. New integrated gasification combined cycle units
are being proposed and far more are likely in the future. Thus, without
a mercury emission standard, this will be a source category of
increasing concern with respect to mercury emissions.

#### [D. Format of Standard]{.underline}

### a. Input versus output

***Recommendation:*** We recommend an output-based standard (lbs/MWh)
using net generation as reported to EIA Form 767.

**Rationale:** An output-based standard rewards efficiency and provides
utilities with compliance flexibility by adding efficiency to the mix of
ways to meet an emission limit. Given that current boilers operate, on
average, at 30% efficiency significant gains can be made if the Agency
takes steps to promote increased efficiency through establishment of
output based emissions standards. For example, analyses completed by DOE
found plants that raised their heat rates from 30% to 36% increased
their efficiency by 20%. An output based standard also most closely
reflects the spirit of Sec. 112, where it was Congress' intent to
establish a toxics regulatory program that encouraged investment in
compliance methods in addition to stack controls, including process
changes, work practice standards, etc., to meet a new emission limit.

### b. Percent reduction versus emission rate versus both

***Recommendation:*** We recommend the use of an output-based emission
rate that would apply to each category/subcategory of units.

**Rationale:** We believe that output-based standards promote
efficiency, as described above. In addition, setting an output-based
emission rate takes into consideration already installed equipment that
captures mercury; and lends itself to more reliable and less burdensome
compliance monitoring than what would be required through alternate
approaches like percent removal (which would require a combination of
coal sampling and stack testing, raising verification/accuracy issues).

Not only would compliance monitoring be more difficult under a percent
reduction standard, it would also be more burdensome to industry,
thereby potentially discouraging coal blending or switching as a control
option. This is a crucial consideration given that historically power
producers have relied heavily on fuel switching as a cost effective
regulatory compliance strategy.

[c. Alternate EITHER/OR standard:]{.underline}

**Recommendation:** We recommend against an either/or approach (i.e.,
the facility chooses whether to meet an emission rate or a percent
reduction requirement). .

***Rationale:*** Our analysis of the ICR data shows that the percent
reduction approach is always less stringent than the emission rate
approach (this holds true for nearly every power plant) for bituminous
and subbituminous coals. For lignite coals, under the top 12% scenario
there are a few power plants where the emission rate (4.01 lb./Tbtu) is
less stringent than a percent reduction scenario (70%). This is because
they already are achieving an emission rate lower than 4.01 lb/Tbtu. In
these instances, the plants would actually be allowed to emit more than
they are emitting now.

If EPA is inclined to promulgate an either/or standard, it should
consider appropriately stringent targets to avoid this effect.

##### [E. Averaging period]{.underline}

***Recommendation:*** We recommend using a 30-day averaging period to
take into account variability that has been measured in stack tests.

**Rationale:** A 30-day averaging period addresses the inherent
variability found in mercury flue gas. EPRI's April 14, 2002
presentation on the initial results of its SCEM data showed that as
averaging times increased (from hourly to daily and then over several
days), variability decreased. The 30-day averaging period will provide
facilities an even longer timeframe over which to meet the emission
rate.

**F. Compliance monitoring method(s)**

***Recommendation:*** We recommend the use of continuous emissions
monitors (CEMs) for mercury.

**Rationale:** It is the most accurate method for measuring stack
emissions, and given the variability that has been observed through
short term stack tests, and the verification/accuracy issues observed
while using combined coal sampling and stack testing (to measure %
reduction), CEM's are the best tool.

Several mercury CEMs already are commercially available. A project
underway at EPRI uses a mercury CEM that takes measurements at 2.5
minute intervals. While there are some technical issues that need to be
worked out (specifically the issue re: frequent oversight to ensure that
the equipment is functioning properly) the compliance deadline of
December 2007 gives manufacturers ample time to perfect the technology
and to develop several CEM options for the industry.

######## MACT FOR NON-MERCURY HAZARDOUS AIR POLLUTANTS FOR COAL- AND OIL-FIRED ELECTRIC GENERATING UNITS.

**[A. Emission Standards]{.underline}**

We firmly believe that EPA has a clear statutory duty to set emission
standards for all of the non-mercury HAPs emitted from coal- and
oil-fired power plants.

***Recommendation***: If the Agency finds that the data are inadequate
for the purpose of fulfilling its statutory duty of setting standards
for all of the non-mercury HAPs, we recommend that EPA immediately
initiate efforts to gather additional data, using its authority under
section 114 of the Act or through other means (e.g., state emissions
tests data), in order to meet its legal requirement.

***Rationale**:* EPA's December 20, 2000 Notice of Regulatory Finding,
65 Fed. Reg. 79825 (Dec. 20, 2000), had the legal effect of listing
coal- and oil-fired electric steam generating units as a source category
under section 112(c). See *UARG v. EPA*, No. 01-1074, (D.C. Cir. July
26, 2001)(order dismissing industry's challenge to the Notice of
Regulatory Finding, on the grounds that "judicial review of the listing
of a source category under section 112(c) of the Act is not available
until after emission standards are issued.") The listing of these
electric generating units had the legal effect of triggering the
requirement in section 112(c)(5) of the Act that "emissions standards
under \[section 112(d)\] for the category or subcategory shall be
promulgated . . . " Section 112(d) requires that regulation of all HAPs
is required for each listed category or subcategory of major sources.
The D.C. Circuit further held, in *National Lime Ass'n v. EPA*, 233 F.3d
625, 634 (D.C. Cir. 2000), that section 112(d) defines a "clear
statutory obligation" on the part of EPA, "to set emission standards"
for all the HAPs listed in the statute at section 112(b), for the
enumerated major source categories.

## **[B. MACT Floor for Existing Sources]{.underline}**

Currently, we do not have recommendations for specific MACT floor levels
for pollutants other than non-mercury metals emitted by coal-fired
electric generating units. Similarly, we do not have recommendations for
MACT floor levels for pollutants other than nickel emitted by oil-fired
electric generating units.

**Recommendation:** We believe that the available stack test data are
sufficient to support a floor for 'non-mercury HAP metals' emitted by
coal fired units and recommend that the Agency use these data to set
emission standards for all of the non-mercury HAP metals.

A floor for the non-mercury HAP metals emitted by coal-fired units is
represented by the average of the best performing 12 percent of the 30
power plants tested. Based on these data we recommend a MACT floor in
the form of an output-based emission rate that would reflect a 99
percent removal for all metals (or each non-mercury HAP metals groups.
See section D.b. below for a discussion of an alternate surrogate
approach). Alternatively, an emission rate could also be set for each
individual metal based on measured stack test data. The table below
lists the input-based emission rates that represent the average of the
best performing 12 percent for the tested units from which an
output-based standard can be calculated.

  ----------------------------------- -----------------------------------
  **Metal**                           **Emission Rate (lb/Trillion Btu)**

  Antimony                            0.15

  Arsenic                             0.24

  Barium                              1.34

  Beryllium                           0.01

  Cadmium                             0.16

  Chromium                            0.91

  Cobalt                              0.19

  Copper                              1.3

  Lead Compounds                      0.34

  Manganese                           2.38

  Molybdenum                          0.61

  Nickel                              1.34

  Selenium                            0.19

  Vanadium                            0.58
  ----------------------------------- -----------------------------------

**For oil fired units,** set a MACT floor for nickel emitted by those
units.

About 90 facilities burn 100% oil. With 12 data points, we have data for
about 13% of the facilities. The top 12% of the facilities for which we
have data would result in a standard derived from the top 2
facilities**.** Thus, the standard would be based on the average of the
top 2 facilities (1.60 and 50.50 lbs/trillion Btu). The MACT standard
would be 26.05 lbs/tBtu.

If EPA determines that the emissions data from the top performing
facility should not be used to calculate the floor because it is a pilot
test, the standard would be the average of top second and third
performers (50.50 and 238.00 lbs/tBtu). The MACT standard would be 144
lbs/tBtu.

**[C. MACT Floor for New Sources]{.underline}**

**Recommendation**: For new sources, the MACT floor for the non-mercury
HAPs should reflect the best performing unit.

**[D. Format of the Standard]{.underline}**

[a. Input v. output]{.underline}

**Recommendation**: We prefer an output-based standard and recommend
exploring the feasibility of establishing such a standard for the
non-mercury HAPs (or groups of non-mercury HAPs). We further recommend
the use of a nickel output-based standard for oil-fired units.

***Rationale:*** An output-based standard rewards efficiency which in
the case of electric generating units, can play a significant role in
determining a unit's emissions in relation to its electricity
generation. Improving efficiency should be a compliance option, much
like burning alternate fuels or installing control devices. Only through
issuance of an output-based standard will this more likely be the case.

[b. Alternate Surrogate Standard]{.underline}

We understand that in previous rulemakings the Agency has chosen to
group pollutants and establish surrogate measures as an alternate
approach to setting individual emission rates. A surrogate approach to
regulating non-mercury HAPs could also be acceptable, but only if it can
be shown that the surrogate measure reflects the actual emissions of the
represented pollutants, and the surrogate emission rate represents the
calculated floor. In addition, any surrogate would, at a minimum have to
have substantially the same properties as the grouped pollutants and be
controlled by the same mechanism or measures. Controls could include
feed rate or type of coal as well as control technologies.

**Recommendation**: If a surrogate approach is taken we recommend that
the non-mercury HAP metals be grouped into two categories for the
purpose of setting a MACT floor: a 'low-volatility HAP metals' category
and also a 'semi-volatile HAP metals' category. The 'low-volatility HAP
metals' group includes antimony, barium, beryllium, chromium, cobalt,
copper, manganese, molybdenum, nickel, vanadium. The 'semi-volatile HAP
metals' group includes lead compounds, cadmium, arsenic and selenium.

In theory, other groupings of non-Hg HAPs make sense, based on the
similar properties within the group. These groupings could include 'Acid
Gases', 'Radionuclides,' 'Organics other than dioxins/furans,' and
'Dioxins/Furans.' For acid gases, we believe that additional data must
currently be available. For example, there are emission factors for HCl
and HF that are used to calculate acid gas emissions for the purpose of
reporting to the Toxics Release Inventory. These emission factors
required the development of an underlying dataset that could be made
available to EPA. We urge EPA to take all necessary steps required for
the control of acid gas emissions.

[c. Alternate Emission Rate/ Percent Reduction Standard]{.underline}

An 'either/or' standard may be appropriate if appropriately stringent
targets are set. The concerns noted above relating to the either/or form
of the mercury standard would also pertain to the non-Hg HAPs (or its
surrogates).

[d. Averaging Period]{.underline}

**Recommendation:** We recommend a 30-day averaging period for the
non-mercury HAPs emitted by coal-fired units, to be consistent with the
averaging period for mercury.

**For oil-fired units,** each unit would be required to meet the floor
over a quarterly averaging period.

**Rationale for oil-fired units:** There is high variability in the data
set from the small number of data points and seasonal variation in oil
use. Providing facilities a long compliance period allows them
flexibility in dealing with variability and in finding cost effective
ways to comply with the standard. Although utilities may prefer an
annual averaging period, such a long time period is not necessary as
long as facilities have the ability to burn less oil as a compliance
option. This approach, unlike a tonnage cap, does not rely on historical
data on oil use to establish a standard, which may not be indicative of
future use.

**[E. Compliance Monitoring Method]{.underline}**

**Recommendation**: In the case of individual emission standards for the
non-mercury HAPs emitted by coal-fired units, we recommend that EPA
devise a monitoring system of sufficient frequency to ensure compliance
with the standard.

If a surrogate approach is taken, we recommend continuous emission
monitoring of the surrogate pollutant (e.g., SO2 for the acid gases). In
addition, to ensure that the surrogate reflects each individual HAP
emission rate (or percent reduction, depending on the format of the
standard), a periodic compliance test should be required (at least
semi-annually) during which each pollutant should be measured as well as
the surrogate so there are data for a direct comparison.

## **For oil-fired units:** 

a\. where no particulate controls are in place: (1) analyze monthly
composite sample of oil; (2) determine annual weighted average based on
rolling12 months; and (3) weight average by amount of oil used each
month.

b\. where particulate controls are in place: In addition to the oil
sampling, (1) do annual testing of control device to determine metal
removal efficiency, and (2) apply that efficiency factor to the metal
emission rate as determined.