United States
Environmental Protection
Agency
Atmospheric Research and
Exposure Assessment Laboratory
Research Triangle Park, NC 27711
Research and Development
EPA/600/SR-94/190 November 1994
EPA Project Summary
Development and Selection of
Ammonia Emission Factors
Rebecca Battye, William Battye, Calvin Overcash, and Stephen Fudge
This project compiles recent litera-
ture on ammonia (NH3) emission fac-
tors for application in the United States.
Most of the recent research supports
acid deposition studies in the Euro-
pean community (specifically, the Neth-
erlands, Great Britain, and Scandinavia),
but some research has been conducted
in Australia. The majority of NH3 emis-
sions in current inventories, (up to 90
percent or more of anthropogenic emis-
sions) originates from livestock wastes
with fertilizer applications providing a
significant proportion. Some invento-
ries exclude industrial emissions en-
tirely because they are insignificant
relative to agricultural sources. Global
climate change research indicates that
undisturbed soils and biomass burn-
ing may also have significant emis-
sions, up to half of the global NH3
budget. The recommended NH3 emis-
sion factors are the following: Euro-
pean factors for agricultural sources;
the Pollutant Emission Factors—Vol-
ume I (AP-42) for industrial sources;
and National Acid Precipitation Assess-
ment Program factors for combustion
sources, human breath and perspira-
tion, and publicly owned treatment
works (POTWs). New factors are devel-
oped for beet sugar production, froth
flotation in mineral processing, mineral
wool (fiberglass) production, refrigera-
tion, and selective catalytic and
noncatalytic reduction for control of ni-
trogen oxide emissions. Additional dis-
creet industrial sources of NH3 are
identified through the Toxic Release
Inventory. Five future research projects
are recommended: investigate global
climate literature on NH3 from undis-
turbed soils and biomass burning; use
animal husbandry primary references
to provide better linkage with United
States Department of Agriculture sta-
tistics; develop temporal profiles for
agricultural emissions; and conduct
additional research into emissions from
refrigeration, POTWs, and selective
catalytic and noncatalytic reduction.
This Project Summary was developed
by EPA's Atmospheric Research and
Exposure Assessment Laboratory, Re-
search Triangle Park, NC, to announce
key findings of the research project that
is fully documented in a separate report
of the same title (see Project Report
ordering information at back).
Introduction
Ammonia (NH3) emissions are impor-
tant in air quality models because NH3 is
the most important alkaline constituent in
the atmospheric boundary layer. The fate
of NH3 released from the ground into the
atmosphere is complex and varied, but
NH3 can have a significant effect on oxi-
dation rates, particularly in clouds, and
hence on deposition rates of acidic spe-
cies. The effect is predicted not only by
models for the heterogeneous chemistry
of cloud droplets but has also been con-
firmed by observation and experimenta-
tion. The long range transport of
atmospheric sulfur dioxide and nitrogen
oxide and the products of their reactions
have long been studied in relation to at-
mospheric deposition. However, much less
research has been done on the effects of
atmospheric NH3, although it is well known
that over large areas of Europe, acid pre-
cipitation is falling in which up to 70 per-
cent of the original acid is neutralized by
NH3.
The importance of NH3 in the atmo-
spheric chemistry of air quality requires
that accurate emission source inventory
data be available for chemical and trans-
port air quality modeling. Relatively little
NH3 emission data have been gathered
and little effort expended in developing
source-category specific NH3 emission fac-
tors because NH3 is generally not a regu-
lated air pollutant. Also, it is not feasible
to speciate NH3 from volatile organic com-
Printed on Recycled Paper
-------
pound (VOC) emission or particulate mat-
ter (PM) emission inventories because as
an inorganic gaseous chemical NH3 is not
included in VOC emission estimates or
PM emission estimates. Consequently,
estimated inventories of NH3 emissions
provide very crude first-order information
at this time.
This project compiled and reviewed re-
cent (after 1985) literature on sources of
NH3 emissions and emission factors. The
compilation contains the most recent re-
search in the field of NH3 emission fac-
tors. The primary focus of the project is
on emission factors as opposed to esti-
mates of total NH3 emissions. Emission
estimates are, however, made for some
categories to determine the relative im-
portance of the source category to overall
NH3 emissions and to assist in developing
priorities for the NH3 emission factor re-
search.
Procedure
The project compiled and critically evalu-
ated NH3 emission information from re-
cent literature with the objectives of 1)
evaluating the quality of available emis-
sion factors, 2) recommending adoption
of the factors where appropriate, 3) devel-
oping emission factors from data in the
literature where possible, 4) recommending
assignments of emission factors to spe-
cific U.S. Environmental Protection Agency
(U.S. EPA) source category codes, and 5)
arriving at a set of recommendations for
future research likely to provide the great-
est gain in knowledge of NH3 emission
factors.
The scope of the literature search in-
cluded peer-reviewed books and journals
and published and unpublished private and
governmental laboratory reports. The
search used computer-based library cata-
logs and personal contacts. The majority
of available relevant literature was from
North America and Europe. When the lit-
erature contained process activity data and
information on the content of NH3 in the
emissions, an emission factor was com-
puted and the scope of application (source
category codes) determined.
Emission factors from or derived from
the literature were assigned quality rating
factors that depend on the quantity and
rigor of underlying data and testing. The
quality rating system is that used by U.S.
EPA's Office of Air Quality Planning and
Standards.
Results and Discussion
Recent research on NH3 emissions as it
relates to acid deposition, is concentrated
in the European community (specifically,
in the Netherlands, Great Britain, and
Scandinavia). In addition, there has been
some research in Australia. The majority
of the NH3 emissions included in current
inventories originate from agricultural
sources. These agricultural sources are
mainly livestock wastes, with fertilizer ap-
plications also providing a significant pro-
portion. NH3 emission estimate numbers
vary widely between different studies, but
the authors of recent European invento-
ries all consider animal wastes and fertil-
izers to be responsible for 90 percent or
more of the anthropogenic NH3 emissions.
Some of the more recent inventories in
Europe even exclude contributions for in-
dustrial facilities entirely, noting that they
are insignificant relative to the agricultural
sources.
Although the European"inventories cur-
rently focus on agricultural sources, there
is evidence that additional, significant
sources of NH3 may exist. Studies in the
United Kingdom suggest that current esti-
mates of NH3 emissions are too small to
explain the concentrations of ammonium
in precipitation and that there may be other
sources of NH3 that have not been con-
sidered in budget studies. Other research,
principally in support of global climate
change research, suggests that there may
be significant NH3 emissions from undis-
turbed soils and biomass burning.
Much of the research obtained and re-
viewed by this project concerns the mea-
surement of NH3 in which results were
generally reported as experimental rather
than as emission factors. The, majority of
NH3 emission factors available in the lit-
erature are discussed relative to the de-
velopment of an emission inventory. In
the development of an emission inven-
tory, emission factors are often either de-
veloped for the experimental measurement
literature or are borrowed directly from
other bodies of work. The primary source
for the emission factors reviewed by this
project was the body of recent emission
inventory literature. The experimental mea-
surement literature was also reviewed to
provide detail on how the measurements
were made. This review contributes to un-
derstanding the uncertainty of the emis-
sion factors, addresses the extent to which
the factors presented incorporate the most
recent research, and identifies data gaps
for future emission factor development.
The most recent NH3 inventory prepared
in the United States is the Emissions In-
ventory for the National Particulate Matter
Study, which used Bureau of Economic
Activity data to project the 1985 NAPAP
inventory to the 1990 study year. There
are several recent NH3 emission invento-
ries for specific European countries, in-
cluding Great Britain, the Netherlands,
Denmark, and Germany. The most recent
European inventory was published in 1992.
Another NH3 inventory was published for
Australia in 1990.
Rough estimates of anthropogenic NH3
emissions in the United States indicate
that animal husbandry and fertilizer appli-
cation dominate emissions (approximately
80 percent) as they do in Europe. Indus-
trial emissions of NH3 and NH3 emissions
from combustion are relatively insignifi-
cant (about 1 percent). NH3 emissions from
refrigeration and POTWs may be signifi-
cant (perhaps 7 percent).
Estimates of NH3 emissions for biom-
ass burning and undisturbed soils were
not made because of the unavailability of
an emission factor for biomass burning
and activity data for undisturbed soils. Re-
cent research indicates that these two cat-
egories may contribute significantly (up to
half) of the global budget of NH3 emis-
sions.
Conclusions and
Recommendations
The NH3 emission factors recommended
for use in future U.S. inventories include
the following: European factors for agri-
cultural sources (animal husbandry and
fertilizer application); the Compilation of
Air Pollutant Emission Factors—Volume I
(AP-42) for the majority of the stationary
industrial sources; and the NAPAP factors
for the majority of the combustion sources
(including coal, oil, natural gas, and mo-
bile sources), human breath and perspira-
tion, and POTWs. New emission factors
are developed for beet sugar production,
froth flotation in mineral processing, min-
eral wool (fiberglass) production, refrig-
eration, and selective catalytic and
noncatalytic reduction for control of nitro-
gen oxide emissions. Specific industrial
sources of NH3 with no corresponding
emission factors are identified through the
Toxic Release Inventory.
Five research areas are recommended
to enhance the quality of NH3 factors ad-
dressed by this project. The five research
areas include completion of the following:
1. Investigate the recent global climate
change literature on NH3 from un-
disturbed soils. Merge the literature
on emission fluxes with new land
use and land cover data categories
to develop emission factors for bio-
genie and mobile sources catego-
ries.
2. Investigate recent literature on NH3
emissions for biomass burning. In-
tegrate the data results with infor-
-------
3.
mation in the United States on natu-
rally occurring fires to develop emis-
sion factors for the United States. 4.
Also, investigate all information on
NH3 emissions for the chemical
agents used to fight these naturally
occurring fires.
Research the primary references for
the animal husbandry emission fac- 5.
tors to provide more accurate link-
ages with the U.S. Department of
Agriculture statistics. In addition, in-
vestigate the discrepancy in the
emission factors for sheep in the
literature.
Develop temporal profiles for the
larger NH3 emission categories.
Specifically, investigate the sea-
sonal nature of the animal hus-
bandry and fertilizer application
emissions.
Conduct additional research on the
NH3 emission factors reported for
refrigeration, POTWs, and selective
catalytic and noncatalytic reduction
(for control of NOX emissions) to
improve confidence in their validity.
Refrigeration contributes a signifi-
cant portion of the NH3 inventory
(about 5 percent); however, this fac-
tor was developed based on a ma-
terial balance. POTWs also
contribute a significant amount of
NH3 (about 2 percent); additional
research is ongoing in the United
Kingdom and California that may
improve the accuracy of the emis-
sion factor.
-------
R Battye, W. Battye, C. Overcash, and S. Fudge are with EC/R Incorporated,
Durham, NO 27707.
William G. Benjeyis the EPA Project Officer (see below).
The complete report, entitled "Development and Selection of Ammonia Emis-
sion Factors, "(Order No. PB95-123915; Cost: $27.00, subject to change) will
be available only from
National Technical Information Service
5285 Port Royal Road
Springfield, VA22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at
Atmospheric Research and Exposure Assessment Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
United States
Environmental Protection Agency
Center for Environmental Research Information
Cincinnati, OH 45268
Official Business
Penalty for Private Use
$300
BULK RATE
POSTAGE & FEES PAID
EPA
PERMIT No. G-35
EPA/600/SR-94/190
------- |