FAA Comments on the Environmental Protection Agency’s proposed rule to
implement the Fine Particle National Ambient Air Quality Standards

As published in 70 FR 65984 on November 1, 2005

Docket ID Number:  OAR-2003-0062

The FAA is concerned that EPA’s proposed implementation of the PM2.5
NAAQS, as it relates to the precursor pollutant ammonia, may create an
unnecessary burden upon FAA when embarking on General Conformity
applicability determinations.

The International Civil Aviation Organization (ICAO) sets the required
emission standards for aircraft engine certification.  The engine
manufacturers report emissions of CO, NOx, HC, and smoke number.  This
data is centralized and publicly reported in ICAO’s Emissions
Databank.  No dataset exists for ammonia emissions from aircraft
engines.

For the last several years, the FAA has co-funded extensive research
into aircraft engine emissions measurement campaigns specifically
designed to address PM2.5 emissions.  The recent emissions measurements
campaigns have confirmed that aircraft engines are direct sources of
PM2.5 and the precursors NOx, SOx, and VOCs.  The early measurement
campaigns included equipment to measure ammonia emissions, but none were
detected.  This is due in part to the extremely high temperatures and
pressures associated with the operation of modern aircraft engines.  

The FAA understands that ammonia emissions have been detected from
on-road engines, typically from the use of reducing agents in the
exhaust system, a technology that is not possible on an aircraft engine.
 It is important to note that the transport sector, in general,
contributes only 3 to 5 percent of total ammonia emissions.

Page 65999 of EPA’s proposed implementation of the PM2.5 NAAQS states:
 “Each State should evaluate whether reducing ammonia emissions would
lead to PM2.5 reductions in their specific PM2.5 nonattainment areas.”
 EPA further clarifies that… “States are not required to address
ammonia as a PM2.5 nonattainment plan precursor, unless the State or EPA
makes a technical demonstration that ammonia emissions from sources in
the State significantly contribute to the PM2.5 problem.”

The FAA recommends that EPA clarify to the States that the technical
demonstrations should apply only to known significant sources of
ammonia, and not as a blanket applicability to every existing source
category identified in their PM2.5 SIP.  The proposed clarification
would eliminate unnecessary inquiries from the States to the FAA and
other involved entities.  The benefits of the proposed clarification
would be a streamlined PM2.5 General Conformity discussion with States,
which minimizes delays of proposed Federal actions.

In summary, no ammonia emissions data exists for aircraft engines and
scientific data supports that aircraft engines do not emit ammonia.  The
FAA is suggesting to insert the following language into the discussion
on ammonia as a precursor to PM2.5:

“For those States that do pursue technical demonstrations for ammonia
emissions, the focus should be on known ammonia sources for which
scientifically-sound data is available.  Not every source category in a
PM2.5 SIP contributes to ammonia emissions (e.g., aircraft engines).”

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