POWER April 2012 - 42

BIOMASS POWER
finalized as written, it will impact the economics
of biomass power plants in a very
positive way.
However, when analyzing the emissions
issues associated with a given plant concept,
there are also two criteria pollutants
regulated under Boiler MACT that must be
examined to determine the overall effect of
the proposed regulation.
CO and PM Limits Revised
The promulgated Boiler MACT regulation
put in place new limitations on particulate
matter (PM) and carbon monoxide (CO)
emissions. In a similar fashion to HAPs
emissions, the regulations were placed on
combustion technology rather than biomass
units as a whole. The proposed revision issued
Dec. 23, 2011, did not remove these
restrictions. However, it did modify the
original limitations in a manner more favorable
to biomass units. Table 2 provides
a summary of the values from the rule promulgated
on March 21, 2011, and Table 3 is
a summary of the revised limitations.
Comparing the emission limits found
in the March 21 promulgated rule (Table
2) and those in the Dec. 23 proposed rule
(Table 3) illustrate that, in almost all categories
of emissions, the limits were increased,
additional combustion technology
categories were added, and more testing
Table 2. Summary of PM and CO Biomass Emission Limitations (March
21, 2011 rule). Source: EPA
Combustion technology
Fluidized bed, existing
Fluidized bed, new
Stoker/other, existing
Stoker, new
Dutch oven/suspension burner, existing
Dutch oven/suspension burner, new
Fuel cells, existing
Fuel cells, new
Suspension/grate, existing
Suspension/grate, new
Particulate matter limitation
(lbm/106 Btu)
0.0390
0.0011
0.0390
0.0011
0.0390
0.0011
0.0390
0.0011
0.0390
0.0011
Carbon monoxide limitation
(ppm @ 3% O2)
430
260
490
160
470
470
690
470
3,500
1,500
Table 3. Summary of PM and CO Biomass Emission Limitations (Dec.
23, 2011 revision). Source: EPA
Filterable
particulate
matter
Combustion technology
Fluidized bed, existing
Fluidized bed, new
Wet stoker, existing
Wet stoker, new
Kiln-dried stoker, existing
Kiln-dried stoker, new
Suspension burner, existing
Suspension burner, new
Dutch oven/pile burner, existing
Dutch oven/pile burner, new
Fuel cells, existing
Fuel cells, new
Hybrid suspension grate, existing
Hybrid suspension grate, new
limitation
(lbm/106 Btu)
0.1100
0.0098
0.0290
0.0290
0.3200
0.3200
0.0510
0.0510
0.0360
0.0360
0.0330
0.0110
0.4400
0.0260
Total selected
metals
(lbm/106 Btu)
0.001200
0.000042
0.000057
0.000026
0.004000
0.004000
0.001100
0.001100
0.000240
0.000041
0.000049
0.000049
0.000490
0.000490
Carbon
monoxide
limitation
(ppm @ 3% O2)
370
230
790
590
250
250
58
58
810
810
1,500
210
3,900
1,500
Alternate
carbon
monoxide CEMS
limitation
(ppm @ 3% O2)
NA
180
410
410
NA
NA
1,400
1,400
440
440
NA
NA
730
730
Notes: CEMS = continuous emissions monitoring system, dscm = dry standard cubic meter, lbm = pound mass, ng = nanogram.
42
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options were provided.
In the category of PM emissions, the
owner/operator will now have the option
to choose a limit on either filterable PM
emissions or on total selected metals. The
list of " total selected metals " will include
arsenic, beryllium, cadmium, chromium,
lead, manganese, nickel, and selenium.
Both options will be required to show
compliance based on a three-run average.
Carbon monoxide limitations for new
fluidized bed boilers decreased slightly,
but CO limitations for stoker units increased
significantly. In addition to changing
emission limitations, the facilities
will have the option of showing compliance
with a three-run average or by using
a 10-day rolling average monitored by a
continuous emission monitoring system.
Changes to the PM and CO limitations result
in added flexibility and reduced cost.
Area Source Limits Unchanged
Another revision to Boiler MACT for facilities
categorized as Area Sources was
also released on Dec. 23, 2011. For biomass
facilities, though, the regulations
already put in place in March remained
unchanged. The only regulated emission
for Area Sources is filterable particulate
matter. All combustion technologies with
a heat input rated between 10 million Btu/
hr and 30 million Btu/hr will be required
to meet a 0.07 lbm/million Btu limitation.
Those units with a heat input rated at 30
million Btu/hr and greater will be required
to meet a filterable PM emission limitation
of 0.03 lbm/million Btu. Note that these
limitations will only apply to new biomass
facilities; existing facilities will not be affected
by this regulation.
The biomass industry is hopeful that the
new limitations proposed in the December
draft regulation will replace the current
limitations released in March last year.
Regardless, if the proposed draft regulations
are an indication of the direction the
EPA is taking toward regulating emissions
from biomass facilities, then this is a very
positive development. With the removal of
stringent HAP regulations and the changes
proposed for PM and CO limitations, the
economics of biomass facilities would
change drastically.
If adopted as final, the updated regulations-coupled
with the recent release of
MATS and, eventually, CSAPR-should
continue to make new biomass facilities
an economic power generation option for
many years to come. ■
-Brandon Bell, PE (brandon.bell@kbr
.com) is a principal mechanical engineer
with KBR Power and Industrial, Chicago.
POWER | April 2012

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POWER April 2012

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