United States
Environmental Protection
Agency
National Risk Management
Research Laboratory
Cincinnati, OH 45268
Research and Development
EPA/600/SR-98/070 January 1999
&EPA Project Summary
A Life-Cycle Impact Assessment
Demonstration for the GBU-24
Duane Tolle, Bruce Vigon, and David Evers
The primary goal of this project was
to develop and demonstrate a life-cycle
impact assessment (LCIA) approach us-
ing existing life-cycle inventory (LCI)
data on one of the propellants, ener-
getics, and pyrotechnic (PEP) materi-
als of interest to the U.S. Department
of Defense (DoD). Sponsorship for this
study was from the Strategic Environ-
mental Research and Development Pro-
gram (SERDP) and involved coopera-
tive efforts by the DoD, U.S. Depart-
ment of Energy (DOE), and U.S.
Environmental Protection Agency (EPA)
in a program to develop technologies
for clean production of PEP materials.
Since the PEP program framework is
strongly oriented around life-cycle as-
sessment (LCA), a baseline LCI of the
guided bomb unit-24 (GBU-24) made
with RDX explosives had been con-
ducted prior to this study and was se-
lected as a test case for this LCIA.
An LCIA methodology and modeling
approach was developed based on the
Society of Environmental Toxicology
and Chemistry's (SETAC's) Level 2/3
equivalency assessment framework and
applied to the previously collected
GBU-24 LCI data. The LCIA considered
potential impacts on human health, eco-
logical health, and resource depletion
associated with the GBU-24 life cycle.
The approach included classification,
characterization, normalization, and
valuation. Quantitative equivalency fac-
tors were obtained from the literature
or developed for 11 of 14 potentially
relevant impact categories. A regional
scaling factor approach was developed
to improve analysis of 4 of the 14 im-
pact criteria, whose sensitivity to po-
tential impacts varied on a regional ba-
sis.
The LCIA methodology based on im-
pact equivalencies described in this
study provides a much more accurate
approach to potential impact evaluation
than the "less-is-best" approach
(SETAC Level 1) using inventory data
only. The method described in this re-
port includes both regional scaling fac-
tors to improve characterization accu-
racy and geographically relevant nor-
malization factors to provide perspec-
tive. This bench-marking analysis can
be used for comparison with alterna-
tive energetics.
This project summary was develop-
ed by EPA's National Risk Management
Research Laboratory 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
Development of future weapons sys-
tems will occur with consideration of envi-
ronmental impacts during the acquisition
process. In fact, DoD policy has elevated
environmental considerations to a level of
importance equivalent to cost and perfor-
mance. In 1990, Congress established
SERDP as a multi-agency effort to sup-
port environmental Research Design and
Development (RD&D) programs. With
SERDP sponsorship, DoD, DOE, and EPA
have cooperated in a program to develop
technologies for the clean production of
PEP materials. Along with the technology
oriented effort, a parallel activity has been
to develop and demonstrate analysis meth-
ods and tools for estimating and manag-
ing the environmental aspects of PEP
materials and the associated end items.
Printed on Recycled Paper
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The framework for the activity has been
strongly oriented around LCA. Thus, a
baseline LCI of the current GBU-24 earth
penetrator bomb was conducted during
1993 and 1994 (the data basis was 1992
operations). That effort attempted to ad-
here very closely to the LCI methodology
described in SETAC and U.S. EPA tech-
nical guideline publications. Preliminary
results of that analysis have been reported
in several forums and publications.
The purpose of this LCIA demonstra-
tion is to develop and demonstrate the
LCIA methodology using the GBU-24 LCI
data collected previously. This is a baseline
or bench-marking analysis, which can be
used for future comparisons.
The GBU-24 is an earth penetrator
bomb equipped with a laser guidance
package designed to penetrate up to 6
feet of reinforced concrete. The BLU-109
bomb body is the largest physical compo-
nent and contributes the majority of the
material mass to the system. The other
components listed were not included be-
cause they are minor in comparison and
are readily reused in any event. Within
the BLU-109, the bomb case itself is the
largest source of material (approximately
70% of the total weight) and efforts are
underway to evaluate ways to reduce pol-
lution from its manufacture through recy-
cling of the steel. Approximately 27% of
the total comes from the explosive fill.
The PBXN-109 is a blend of four compo-
nents: CXM-7 explosive mix, aluminum
powder, thermoset plastic binder, and mis-
cellaneous other blending and forming
agents. About 3% of the mass is contrib-
uted by thermal insulation applied to the
bomb exterior and asphalt interior liner.
The GBU-24 life cycle includes both
commercial as well as DoD facilities. Raw
materials are obtained for the energetic
materials production from commercial com-
modity chemical producers. The synthesis
of RDX, together with the coating and
blending needed to manufacture CXM-7,
is provided by Holston Army Ammunition
Plant (HSAAP) in Kingston, TN. The CXM-
7 is then shipped to McAlester Army Am-
munition Plant (MCAAP) in McAlester, OK.
Load/assemble/pack (L/A/P) operations,
which include blending the CXM-7 with
aluminum and other additives to produce
the plastic-bonded explosive used for the
GBU-24, are performed at MCAAP. The
steel bomb bodies are also shipped to
MCAAP from a commercial producer (Na-
tional Forge).
Modeling of the GBU-specific manufac-
turing operations to obtain LCI data was
performed in considerably greater detail
than for the commercial sector activities.
This was done for several reasons, not
the least of which was the fact that the
span of control of DoD for influencing such
major industrial activities as steel and am-
monia manufacture is limited.
Once the bomb unit is manufactured it
undergoes qualification tests. Final assem-
bly of the GBU-24 with fuse, guidance
control unit, adapter group, and air-foil
group is performed on aircraft carriers.
(This analysis assumed that the Navy ver-
sion of the GBU-24 is the system of inter-
est.) Storage of the unit over the lifetime
of the weapon is included. Following re-
tirement, the item is decommissioned at
the Naval Service Warfare Center (NSWC)
using waterjet extraction of the fill and
open burning/detonation of the energetic
materials.
The LCI/LCIA included activities from
cradle (raw feedstock materials such as
ammonia) to grave (final disposition
through disposal/recycling) for PEP end-
use items. The LCI data acquired included
primary information from government con-
trolled operations for the manufacturing
and use operations and more generic in-
formation for ancillary operations. Ancil-
lary operations include feedstocks and ex-
ternal power grids.
Procedure
The LCIA included an initial scoping
process, followed by classification, char-
acterization, normalization, and valuation.
Scoping included an evaluation of the data
available from the LCI, a preliminary de-
termination of the impacts of concern,
whether additional data are needed for
evaluating specific stressors, and a deci-
sion on the level(s) of impact analysis. In
order to facilitate the scoping, stressor/
impact networks were prepared with pre-
liminary inventory data (including non-
quantitative) to determine the most appro-
priate impact categories for analysis and
to determine if the LCI data are in the
correct form for impact analysis. The ba-
sis of comparison between two systems
in an LCA framework is the functional unit
(FU). The functional unit is determined by
the quantities associated with equivalent
performance levels of the alternatives. In
both the LCI and LCIA, the basis of the
analysis was one GBU-24 bomb.
Classification was conducted after
scoping and is the process of linking or
assigning data from the LCI to individual
stressor categories within the three major
stressor categories of human health, eco-
logical health, and resource depletion.
Characterization involved the analysis
and estimation of the magnitude of the
potential for stressors associated with the
baseline GBU-24 to contribute to each of
the impact categories. The equivalency
analysis approach functions by converting
a large number of individual stressors
within a homogeneous impact category
into a single value, by comparing each
stressor with a reference material. The
procedure generally involves multiplying
the appropriate equivalency factor by the
quantity of a resource or pollutant associ-
ated with a functional unit of GBU-24 (1
bomb) and summing over all of the items
in a classification category.
For the Level 2 impact assessment (haz-
ard potential) evaluation used in this study,
a limited subset of the chemicals identi-
fied during the LCI had already been as-
signed impact equivalency units in pub-
lished documents. Examples of groups of
chemicals that have been evaluated for
impact equivalency include nutrients, glo-
bal warming gases, ozone depletion gases,
acidification potential chemicals, and pho-
tochemical oxidant precursors. Some of
the equivalency factors reported in the
literature were modified by application of
regional scaling factors.
New impact equivalency (hazard poten-
tial) units for toxicity impact criteria were
created for some chemicals identified in
the baseline LCI by adapting the hazard
ranking approach developed for the EPA
by the University of Tennessee to modify
the Level 3 Toxicity, Persistence, and Bio-
accumulation Potential Approach. This in-
cluded evaluation of impacts (e.g., toxicity
to humans, fish, or wildlife) other than the
impacts evaluated in Level 2, although a
few chemicals with multiple impacts were
evaluated by both the Level 2 and 3 ap-
proaches.
The carcinogenicity equivalency factor
is based on the weight-of-evidence. (WOE)
for carcinogenicity as described by either
the International Agency for Research on
Cancer (IARC) or the EPA. As suggested
in the University of Tennessee hazard
ranking report, a score of 1 to 5 was given
to each of the WOE groups. Because
each agency has different ranking groups,
the equivalency score is based either on
an average of the scores for each agency
or the actual score if only one agency
ranked the chemical.
Evaluation of the magnitude of resource
depletion impacts associated with the life-
cycle of the GBU-24 bomb started with
the resource use inventory information
from the LCI. Resources included in the
analysis involved minerals and fossil fu-
els. These impacts were evaluated from a
sustainability (time-metric standpoint),
which considers the time to exhaustion of
the resource. Information on the world re-
serve base and production of minerals
came from various documents by the U.S.
Geological Survey's Minerals Information
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Center on the World Wide Web. Infor-
mation for energy sources came from the
Annual Energy Review for 1994 by DOE's
Energy Information Administration. Water
Use (consumption) was not selected as
one of the primary impact categories, be-
cause it was known at the outset that
these data were not included in the inven-
tory and because water availability is not
considered to be a problem at MCAAP,
HSAAP, or NSWC.
The equivalency factors for the solid
waste disposal impact criterion under land
use are based on the estimated volume
calculated using the specific weight (in Ib/
yd3) of each type of solid waste. Since the
LCI data for solid wastes are expressed
as weight/functional units, multiplication of
the weight and inverse of the specific
weight described the landfill volume re-
quired.
Quantitative equivalency factors were
developed for 11 of the 14 impact catego-
ries. A regional scaling factor approach
was developed to improve analysis of 4 of
the 14 impact criteria, whose sensitivity to
potential impacts varies on a regional ba-
sis. Although the accuracy of the impact
scores for these four impact criteria is
improved by this process, the resulting
impact scores are still not as accurate as
the impact scores for the global criteria
that are unaffected by regional differences
in sensitivity. Since the impact category
for suspended particulates (PM10) included
only one stressor, the regional scaling
analysis was used without a need for
equivalency factors. The inventory pro-
vided by the model did not include data
for emissions associated with the ozone
depletion impact criteria, even though the
preliminary scoping analysis indicated that
inventory data for this impact category
should have been available. Land use as-
sociated with natural resource extraction
was not evaluated due to the difficulty in
determining the quantity of land used for
many of the resources identified in the
inventory.
Regional scaling factors were developed
for the following four impact criteria: sus-
pended paniculate (PM10) effects, acid
deposition, smog creation, and eutrophi-
cation. These impacts have either a re-
gional or local spatial resolution because
environmental conditions in different loca-
tions cause the same emission quantity to
have more or less impact. Some loca-
tions/regions may be highly sensitive to
one of these impacts and other locations
may be only moderately affected or may
not experience any impact at all from the
same quantity of emissions. For each one
of these four impact categories, different
levels of sensitivity throughout the U.S.
were defined and linked with scaling fac-
tors for use in refining the final impact
category scores. In some cases these scal-
ing factors were indicated on maps, based
on a composite of information, such as
sensitive receptors, emission sources, and
emission deposition rates. In all four cases
the scaling factors were averaged for each
state according to the percent of area
covered by all scaling factors for a given
impact category within that state. These
average state scaling factors were neces-
sary for allocating emissions among states
when specific facility locations were not
known or too numerous (e.g., emissions
associated with the national grid of elec-
tric power generation plants).
Normalization is recommended after
characterization and prior to valuation of
LCIA data because aggregated sums per
impact category need to be expressed in
equivalent terms before assigning valua-
tion weight factors. The normalization step
helps to put in perspective the relative
contribution that a calculated character-
ization sum for an indicator category
makes relative to an actual environmental
effect.
The normalization approach involves the
determination of factors that represent the
total, annual, geographically relevant im-
pact (expressed in Ibs/yr) for a given im-
pact category. The goal is to develop sci-
entifically defensible normalization factors,
making use of existing emissions or re-
source extraction data. Impact categories
are divided according to three spatial per-
spectives: global, regional, or local. The
global impact categories (e.g., global
warming) are assumed to be independent
of the geographic location in which emis-
sions are released or resources are ex-
tracted. The regional impact categories
(e.g., acid rain) are relevant to fairly large
areas, but are clearly not global or limited
to one site. Thus,-data selected for the
regional, normalization factors were based
on the maximum annual state total impact
(total emissions of relevant chemicals mul-
tiplied by a regional scaling factor). Local
impact categories were limited to the three
acute toxicity categories (e.g., terrestrial
[wildlife] toxicity) because the area within
which a single organism is impacted for
each of these acute toxicity categories is
very small. The total impact used for deter-
mining the local normalization factor was
considered to be the maximum annual
emission of relevant chemicals emitted
from a single facility in the United States
into the environmental medium of con-
cern.
Valuation involves assigning relative val-
ues or weights to different impacts so
they can be integrated across impact cat-
egories for use by decision makers. It
should be recognized that this is largely a
subjective process, albeit one that is in-
formed by knowledge of the nature of the
issues involved. The valuation method
used in this study is known as the Analyti-
cal Hierarchy Process (AHP). AHP is a
recognized methodology for supporting
decisions based on relative preferences
(importance) of pertinent factors. Environ-
mental preferences are expressed by the
valuation team in a pair-wise manner sup-
ported by a software package known as
Expert Choice™.
Results
Normalized Impact Criteria
Scores
Impact criteria scores (hazard potential)
were developed for the baseline GBU-24
production process using the inventory
quantities of each stressor per functional
unit. Impact criteria scores are calculated
by multiplying the inventory quantity times
the impact equivalency factor for each in-
dividual chemical and then dividing by the
total normalization factor for that impact
category.
The normalized impact scores per func-
tional unit in Table 1 indicate that the
Terrestrial Toxicity impact category shows
the greatest normalized impact score
(4.26E-06) for the baseline GBU-24 pro-
cess, when all impact categories are con-
sidered to be of equal importance (i.e.,
the valuation weights have not been ap-
plied). The relative contribution of each
normalized impact score to the total nor-
malized impact score for the baseline
GBU-24 process is shown in the third
column. This column indicates that the
Carcinogenicity and Terrestrial Toxicity
impact categories contribute, respectively,
41% and 42% of the total impact when all
normalized impact scores are considered
of equal importance.
Valuation-Weighted Impact
Scores
AHP valuation hierarchies were devel-
oped to reflect two perspectives: "policy"
and "local". The "policy" perspective em-
phasizes the global impacts of concern to
a national policy maker. The "local" per-
spective emphasizes the local impacts of
more concern to someone siting a spe-
cific facility. The valuation process as-
signed weights to global, regional, and
local, respectively, of 32%, 33%, and 35%
for the "policy" perspective, and 17%, 37%,
and 47% for the "local" perspective. Final
weights were assigned for each of the 14
impact criteria.
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Table 1. Comparison of Normalized Impact
Scores by Criteria for the Baseline
GBU-24 Production Process
Impact Category
%of
Normalized Total
Impact For All
Score Scores
Ozone Depletion
Potential NA^ 0
Global Warming 2.55E-10 0
Resource Depletion 5.79E-09 0
Acid Rain 2.83E-08 0
Smog 2.28E-07 2
Suspended (PM10)
Particulates 1.79E-07 2
Human Inhalation
Toxtcity 2.84E-07 3
Carcinogenteity 4.21 E-06 41
Solid Waste Disposal
Land Use 1.14E-07 1
Resource Extraction/
Production Land Use NA 0
Terrestrial
(Wildlife) Toxicity 4.26E-06 42
Aquatic (Fish) Toxlcity 7.06E-07 7
Eutrophteatton 1.64E-07 2
WNA « Data not avaitabte; relevant chemicals not listed
in LCI.
The weights developed by the AHP valu-
ation process were multiplied by the nor-
malized scores for each impact category,
and these weighted, normalized impact
scores were summed to get a total score
for the baseline GBU-24 production pro-
cess. The scores for each chemical or
resource contributing to a particular im-
pact category were divided by the normal-
ization factor for that impact category. This
was considered necessary before multi-
plying by the valuation weights to prevent
introduction of bias due to the large quan-
tities typically associated with resource ex-
traction and use compared to the small
quantities typically associated with emis-
sions released after emission control de-
vices.
The pie diagrams shown in Figures 1
and 2 illustrate the percentages that each
weighted, normalized impact category
score contributes to the total weighted im-
pact score, respectively, for the "policy"
and "local" valuation perspectives. These
two figures show that carcinogenicity and
terrestrial toxicity are the top contributors
to the total potential impact of the baseline
GBU process, regardless of which of the
two valuation perspectives is used. In or-
der to reduce the impact potential for the
baseline GBU process, the individual
chemical emissions contributing the most
to these two high scoring impact cate-
gories are logical choices to consider re-
ducing first.
The LCIA methodology based on im-
pact equivalencies described in this report
provides a much more accurate approach
to potential impact evaluation than the
"less-is-best" approach (SETAC Level 1)
using inventory data only. The "less-is-
best" approach ignores the substantial dif-
ferences in impact potential between dif-
ferent chemicals contributing to the same
impact category. For example, more hy-
droxide is released in wastewater per FU
than ammonia, but due to the higher
aquatic equivalency factor for ammonia,
its normalized aquatic impact potential is
greater.
The "less-is-best" approach is also in-
accurate when entire impact categories
are considered. If stressor quantities are
summed for air emissions, water emis-
sions, solid wastes, and carcinogens, the
respective totals for each of these impact
categories in Ibs per FU are 2.69E+04,
3.54E-02, 1.27E+03, and 1.14E+01. This
Level 1 approach suggests that air emis-
sions associated with the human health
inhalation toxicity impact category have a
much greater impact than water emissions
associated with aquatic toxicity, or carci-
nogenic emissions associated with carci-
nogenicity. However, valuation results for
both of the perspectives indicate that the
greatest potential impact from these three
impact categories is from carcinogenic
emissions.
The method described in this report in-
cludes both regional scaling factors to im-
prove characterization accuracy and geo-
graphically relevant normalization factors.
Although this method is expected to be
somewhat less accurate than the generic
or site-specific exposure/effect assessment
approaches using modeling, it requires
much less effort than either of these meth-
ods.
The full report was submitted in fulfill-
ment of cooperative agreement CR822956
by Battelle under sponsorship of the U.S.
Environmental Protection Agency.
AQTOX7%
ACIDDEP 0% EUTROPH 1%
/ SMOG 4%
SUSPPART 3%
INHLTOX 4%
TERRTOX
40%
AQTOX 7%
EUTROPH1%
\ SMOG 3%
SUSPPART 3%
INHLTOX 4%
^CARCINGN
' 41%
TERRTOX
40%
CARCINGN
42%
Figure 1. Impactcategorypercentagesoftotalimpactscoreweighted
by the "Policy" perspective for the baseline GBU process.
Figure 2. ImpactCategorypercentagesoftotalimpactscoreweighted
by the "Local" perspective for the baseline GBU process.
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Duane Tolle, Bruce Vigon, and David Evers are with Battelle Columbus Labora-
tories, Columbus, OH 43201-2693.
Kenneth R. Stone is the EPA Project Officer (see below).
The complete report, entitled "Life-Cycle Impact Assessment Demonstration for the
GBU-24," (Order No. PS 99-102659; Cost $29.50 subject to change) will be
available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
National Risk Management Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268
United States
Environmental Protection Agency
Center for Environmental Research Information
Cincinnati, OH 45268
Official Business
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