Board
on
Agriculture
and
Natural
Resources,
HA394
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Constitution
Avenue,
NW
Washington,
DC
20418
Telephone
(
202)
334
3062
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(
202)
334
1978
national­
academies.
org
The
Scientific
Basis
for
Estimating
Air
Emissions
from
Animal
Feeding
Operations
A
New
Interim
Report
from
the
Committee
on
Animal
Nutrition,
Board
on
Agriculture
and
Natural
Resources,
and
Board
on
Environmental
Studies
and
Toxicology
Concern
with
possible
environmental
and
health
effects
of
air
emissions
generated
from
animal
feeding
operations
(
AFOs)
has
grown
with
the
increasing
size,
geographic
concentration,
and
suburbanization
of
these
operations
in
what
was
formerly
rural,
sparsely
populated
agricultural
land.
In
response
to
this
concern,
the
Office
Air
Quality
Planning
and
Standards
Division
(
OAQPS)
of
the
U.
S.
Environmental
Protection
Agency
(
EPA)
asked
the
National
Research
Council
(
NRC)
to
review
the
scientific
basis
for
estimating
emissions
from
individual
AFOs.
Because
the
issues
regarding
emissions
from
AFOs
are
much
broader
than
the
interests
of
any
one
federal
agency
are,
the
U.
S.
Department
of
Agriculture
(
USDA)
joined
EPA
in
the
request
for
this
study.

The
NRC
convened
a
study
panel
of
experts
chosen
for
their
expertise
and
knowledge
in
a
range
of
disciplinary
backgrounds,
including
epidemiology
and
biostatistics,
environmental
engineering,
atmospheric
and
tropospheric
chemistry,
biogeochemistry,
environmental
sciences,
agricultural
law,
animal
nutrition,
agricultural
engineering,
soils
and
physical
chemistry,
microbiology,
agricultural
and
resource
economics,
emission
measurement
and
characterization,
and
biological
engineering.
For
the
interim
report,
the
committee:

 
Identified
the
scientific
criteria
needed
to
ensure
that
estimates
of
air
emission
rates
are
accurate,
the
basis
for
these
criteria
in
the
scientific
literature,
and
uncertainties
associated
with
them,
 
Assessed
emission­
estimating
approaches
in
a
recent
EPA
report
Air
Emissions
from
Animal
Feeding
Operations,
and
 
Identified
economic
criteria
needed
to
assess
emission
mitigation
techniques
and
best
management
practices.

Following
its
analysis,
the
study
panel
concludes
that
estimates
of
air
emissions
are
needed
from
individual
AFOs
in
order
to
understand
health
and
environmental
impacts
on
a
variety
of
spatial
scales.
However,
direct
measurement
of
emissions
from
all
AFOs
is
likely
infeasible.
Characterizing
AFOs
in
terms
of
their
components
(
e.
g.,
model
farms)
may
be
a
plausible
approach
for
developing
estimates
of
air
emissions
from
individual
farms
or
regions
as
long
as
the
components
or
factors
chosen
to
characterize
the
feeding
operation
are
appropriate.
Depending
on
the
character
of
the
AFO,
these
factors
may
include
animal
types,
nutrient
inputs,
manure
handling
practices,
output
of
animal
products,
management
of
feeding
operations,
confinement
conditions,
physical
characteristics
of
the
site,
and
climate
and
weather
conditions.

The
study
committee
additionally
finds
the
model
farm
construct
as
described
by
EPA
is
inadequate
to
estimate
air
emissions
from
individual
AFOs
because
of
the
way
in
which
it
characterizes
feeding
operations
combined
with
weaknesses
in
the
data
needed
to
implement
it.
The
committee
proposes
a
process­
based
model
farm
approach
that
incorporates
"
mass
balance"
constraints
for
some
of
the
emitted
substances
of
concern,
in
conjunction
with
estimated
emission
factors
for
other
substances,
may
be
a
an
alternative
to
the
model
farm
construct
defined
by
EPA.

This
interim
report
provides
the
committee's
findings
to
date
on
assessment
of
the
scientific
issues
involved
in
estimating
air
emissions
from
individual
AFOs
as
related
to
current
animal
production
systems
and
practices
in
the
United
States.
The
committee's
final
report
will
include
an
additional
assessment
within
eight
broad
categories:
industry
size
and
structure,
emission
measurement
methodology,
mitigation
technology
and
best
management
plans,
short­
and
long­
term
research
priorities,
alternative
approaches
for
estimating
emissions,
human
health
and
environmental
impacts,
economic
analyses,
and
other
potential
air
emissions
of
concern.
The
final
report
is
anticipated
to
be
issued
at
the
end
of
this
year.

A
prepublication
copy
of
the
interim
report,
The
Scientific
Basis
for
Estimating
Air
Emissions
from
Animal
Feeding
Operations
will
be
available
to
the
public
on
June
4,
2002
at
1:
00
PM
Pacific
Time.
The
National
Academy
Press
(
http://
www.
nap.
edu/
catalog/
10391.
html)
will
publish
the
interim
report
