PLANNING FOR NEW PROCESSES: ENVIRONMENTAL ASPECTS 1001
The following procedure will be used for permitting of
energy recovery facilities that utilize LFG:
If the LFG Is Pretreated (i.e., if the constituents other
than methane are removed from the gas), then permit as
a combustion source with no further emission testing or
ambient modeling necessary to satisfy toxic concerns. The
permit should address traditional combustion contaminants
such as NO x and CO. However, the permit application for
this type of option must include a detailed description of
the method(s) to be used for gas pretreatment. LFG can
contain up to 50%, by volume, CO 2 (35–45%) and air
toxics (1–2%). The pretreatment employed must remove
these compounds before the LFG can be permitted for just
the traditional combustion contaminants. Note that gas
pretreatment will minimize toxic products of incomplete
combustion and minimize system corrosion.
If the LFG Is Not Pretreated, then permit as a combus-
tion source and use the total concentration of NMOC emit-
ted to address toxic issues. Note that if the gas is burned,
either by a flare or energy recovery process, generally the
air toxics will be destroyed. It will be easier and more effi-
cient to regulate the NMOC (or total VOCs) than trying to
identify and regulate all contaminants of LFG emissions,
since they can vary greatly depending on the waste dis-
posed at the landfill. The permit should address traditional
combustion contaminants such as NO x and CO. The EPA
proposed standard of 20 ppmvd NMOC should be used as
BACT for the control of untreated LFG used as a combus-
tion source. Periodic stack testing of the emissions is rec-
ommended at the discretion of the permit writer.
With regard to compliance with Part 231, the LFG
facility may need to obtain NO x and CO offsets at the
ratio applicable to its location (i.e., 1.3 or 1.15 to 1). This
requirement may change if the EPA decides that LFG-type
facilities are eligible for a pollution prevention exclusion.
The permit reviewer will need to exercise judgment to
determine if the LFG facility is required to obtain these
offsets. As stated above, an LFG facility can be used for
energy recovery. While a combustion turbine or internal
combustion engine is not normally considered add-on pol-
lution control devises, they do serve the same function as a
flare, namely to reduce VOC emissions at the landfill with
the incidental benefit of producing useful energy (energy
that would otherwise be produced using higher polluting
fossil fuels). For an LFG facility the reviewer should pro-
ceed as follows:- Verify that the NO x increase has been minimized
to the extent practicable; - Confirm (through modeling or other appropriate
means) that the actual significant increase in NO x
emissions will not violate the applicable NAAQS,
PSD increment or adversely impact any air qual-
ity related value; - Apply all otherwise applicable SIP and minor source
and permitting requirements and ensure that NO x
offsets are provided in an area in which nonattain-
ment review applies to NO x emissions increases.
Coordination within the DepartmentThe use of LFG will require coordination of efforts
between the Divisions of Air Resources (DAR) and Solid
and Hazardous Materials (DSHM). If a landfill meets the
criteria cited above and the emissions from the site must
be controlled, the proposed plan for this control should
be submitted to both Divisions. DSHM should focus their
review of the proposal, based on the requirements of Part
360-2.16. DAR should focus their review on evaluating and
permitting the combustion sources that utilize the LFG, as
outlined in the previous section. Both Divisions must keep
in mind that LFG can be a valuable resource for energy
generation and that using this resource will conserve the
use of other fossil fuels and permit the re-use of material
otherwise considered waste. Further, the respective project
managers handling a particular facility’s permit applica-
tion should maintain communication to ensure that there
are no unnecessary delays on developing a permit for an
LFG facility.APPENDIX A OF AIRGUIDE 41NSPS for Municipal Solid Waste LandfillsIn accordance with the Clean Air Act, the U.S. Environmental
Protection Agency (EPA) has proposed New Source
Performance Standards (NSPS) under 40 CFR 60 Subpart
WWW for municipal solid waste landfills. These proposed
NSPS will affect landfills that began construction or modi-
fication after the standard was proposed (5/30/91) or exist-
ing landfills that have accepted waste since November 8,- It must be noted that this proposed rule is currently
being developed. This proposed rule would require landfills
to install active gas collection and control systems if they
exceed both of the following criteria:
- design capacity in excess of 2.500,000 Mg
(2,700,000 tons); and - NMOC emission rate in excess of 50 Mg per year
(50.05 tpy).
Landfills closed prior to November 8, 1987 or having design
capacities less than 2.5 million metric tons will be exempt
once this rule is finalized.
The NMOC emission rate is determined by the following
equation:M NMOC = 2 L 0 R (1e– kt^ ) C NMOC (3.595 10 – 9 ) where,
M NMOC = mass emission rate for NMOC, Mg/yr
L 0 = refuse methane generation potential, m^3 /Mg
refuse (default value = 170 m^3 /Mg)
R = average annual acceptance rate, Mg/yr
k = methane generation rate constant, 1/yr
(default value = 0.05/yr)
t = age of the land fill in yearsC016_007_r03.indd 1001C016_007_r03.indd 1001 11/18/2005 11:01:30 AM11/18/2005 11:01:30 AM