United States
Environmental Protection
Agency
National Risk Management
Research Laboratory
Cincinnati, OH 45268
Research and Development
EPA/600/SR-96/094 September 1996
Project Summary
Life Cycle Assessment for PC
Blend 2 Aircraft Radome
Depainter
R. Thomas and W. E. Franklin
This project was sponsored by the
Department of Defense Strategic Envi-
ronmental Research and Development
Program (SERDP) and conducted by the
U.S. Environmental Protection Agency
National Risk Management Research
Laboratory (NRMRL). In support of
SERDP's objective to develop environ-
mental solutions that improve mission
readiness for federal activities, this re-
port was developed to determine the
potential environmental and economic
impacts of using an alternative chemi-
cal depainter for B-52 and KC-135 air-
craft radomes at the U.S. Air Force Okla-
homa City Air Logistics Center. A life
cycle assessment (LCA) was conducted
to identify the performance, cost, and
environmental impacts of propylene car-
bonate Blend 2 (PC2), a blend of three
low volatile chemicals used to depaint
the radomes. The variables analyzed in
this study were the volume of PC2 re-
quired to depaint a radome, the number
of radomes depainted per batch of PC2,
the time required to depaint a radome,
and the time required to recycle spent
PC2. An estimate of volume, number of
radomes, and time was provided by the
Air Logistics Center as the baseline
case. Increases and decreases to the
baseline case were analyzed to deter-
mine changes in environmental and cost
impacts.
This Project Summary was developed
by EPA's National Risk Management
Research Laboratory, Cincinnati, OH, 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
A Life Cycle Assessment (LCA) was
performed on a potential replacement sol-
vent blend for aircraft radome depainting
at the Oklahoma City Air Logistics Center
at Tinker Air Force Base. An LCA is a
three-step process, (1) a life cycle inven-
tory, (2) a life cycle impact assessment,
and (3) a life cycle improvement analysis.
Tinker Air Force Base currently uses
the highly volatile methyl ethyl ketone
(MEK) to depaint B-52 and KC-135 air-
craft radomes. Significant evaporation oc-
curs during each depainting, and MEK
has been targeted for elimination by EPA's
33/50 Voluntary Reduction Program. EPA
and Tinker Air Force Base are evaluating
several solvent blends containing propy-
lene carbonate (PC) as a nonvolatile, less
toxic substitute. This study focuses on
one of these blends, known as PC Blend
2 (PC2), which is composed of 50% n-
methyl-pyrrolidone (NMP), 25% dibasic
ester (DBE), and 25% propylene carbon-
ate.
PC2 is not currently in use at Tinker
Air Force Base, therefore, several as-
sumptions were made based on limited
knowledge of how PC2 would perform
and may not fully characterize actual per-
formance. These assumptions comprise
the baseline PC2 use scenario presented
in the LCA. To balance the lack of experi-
ence in PC2 performance a number of
alternative PC2 use and waste manage-
ment scenarios were also evaluated.
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Procedure
The study used a comprehensive ap-
proach which encompassed energy re-
quirements, solid wastes, atmospheric
emissions, and waterborne wastes asso-
ciated with and resulting from the produc-
tion, use, and disposal of the PC2
depainting solvent. Each key processing
step, from the extraction of raw material
to final disposition of the spent solvent,
was included in the assessment. The par-
tial impact assessment used a classifica-
tion system to categorize the atmospheric
and waterborne emissions into relevant
potential impact categories of ecosystem
and human health. A mass loading char-
acterization model was then used to com-
pare baseline impact results to a variety
of improvement alternatives. The improve-
ment assessment used the results of the
Life Cycle Inventory (LCI) and impact as-
sessments in tandem with a cost analysis
to evaluate the improvement alternatives.
To enhance the utility of the report and
its results, the study considered: (1) the
amount of PC2 required to depaint 10
KC-135 aircraft radomes (estimated at 110
gallons); (2) the amount of PC2 required
to depaint 10 B-52 radomes (estimated at
180 gallons); and (3) annual PC2 usage
at Tinker Air Force Base, based on past
MEK depaint usage (estimated at 1,820
gallons of PC2).
Baseline Results and
Discussion
Energy
The energy contributions of each major
component included in the LCI are briefly
discussed below. The total energy for
depainting 10 KC-135 radomes is approxi-
mately 43 million British thermal units (Btu).
Raw materials acquisition and chemical
processing associated with the production
of NMP, DBE, and PC account for 56%,
23%, and 16% of the total energy require-
ments, respectively. Blending, usage, and
disposal of PC2 account for the remaining
5% of the total energy requirements.
Energy categories in an LCI consist of
process, transportation, and energy of
material resource. Process energy is used
to manufacture the PC2 and uses 44% of
the total energy required for production of
the solvent. Transportation energy, requir-
ing only 3% of the total energy, is used to
transport the chemicals and materials to
the next step in the manufacturing pro-
cess. The energy of material resource is
the inherent energy of petroleum, natural
gas, and coal when used as a raw mate-
rial feedstock. It accounts for 53% of the
total energy requirements.
Energy requirements are categorized
into five basic sources: natural gas, petro-
leum, coal, nuclear, and other (i.e., geo-
thermal, solar, hydropower, etc.). The ma-
jority of the energy is derived from natu-
ral gas and petroleum, which account for
69% and 23% of the total respectively.
These values include the energy of mate-
rial resource attributed to natural gas and
petroleum when used as raw material feed-
stock. The remaining 8% of the energy
requirements for the production and use
of PC2 are met by nuclear, coal, and
other sources.
Solid Waste
Over the entire life cycle about 80
pounds of industrial solid waste is pro-
duced for every 10 KC-135 radomes
depainted. The production of NMP, DBE,
and PC contribute 29%, 18%, and 11%,
respectively. The blending operation con-
tributes about 11% of the total solid waste.
The PC2 use component includes solid
waste from electricity for the depainting
operation and represents 32%. The PC2
disposal component contributes less than
1% to the total industrial solid waste pro-
duced.
Fuel-related solid waste resulting from
the combustion of fuels make the greatest
contribution representing 94% of the total
industrial solid wastes produced. Process
solid wastes comprise the remaining 6%
of total process waste.
Atmospheric and Waterborne
Emissions
Both process- and fuel-related catego-
ries of emissions contribute significantly
to the total emissions. Portions of these
emission categories may also be attrib-
uted to process emissions. Table 1 sum-
marizes the atmospheric and waterborne
emissions and their sources.
Results and Discussion of LCI
Sensitivity Analysis
The results of the LCI Sensitivity Analy-
ses include all energy use and emissions
associated with raw material acquisition,
chemical processes for producing the
chemical components of PC2 (DBE, NMP,
PC), PC2 blending, and PC2 use and
disposal for depainting radomes at Tinker
Air Force Base. For the baseline, disposal
of spent PC2 is accomplished by incinera-
tion. For the recycled system, it is as-
sumed that a recovery rate of approxi-
mately 85% can be achieved. The 15%
lost during the recycling process could be
attributed to adherence of the PC2 to
waste paint chips, absorption of the PC2
in the cloth filter, or some step in the
distillation process. The amount lost is
assumed to be ultimately incinerated as
hazardous waste. Virgin PC, DBE, and
NMP must be used to replenish the 15%
lost each time the PC2 is recycled, as
well as the 0.5% evaporative loss assumed
to occur during PC2 use. The recycling
system results also include the energy
requirements and emissions produced dur-
ing transport of the spent PC2 to a theo-
retical recycling facility in Texas, distilla-
tion of the solvent blend, re-blending of
the PC2 components, and transportation
of the recycled PC2 back to Tinker Air
Force Base.
Energy
By recycling the spent PC2, the total
energy requirements are reduced by ap-
proximately 70%. The majority of this re-
duction comes from decreased process
and energy of material resource require-
ments in the back-end steps in the pro-
duction of the DBE, PC and NMP compo-
nents of PC2. The energy necessary to
produce PC2 is spent to make up for the
15% recycling loss, the 0.5% evaporative
emissions, and the PC2 blending process.
The energy required for disposal of waste
is also drastically reduced to about 15%
of the baseline amount. The energy re-
quired for distillation and transport of the
spent PC2 is about 25% of the total en-
ergy for the recycling system.
The energy results are also very sensi-
tive to any changes in the volume and
yield assumptions. An increase or de-
crease in the volume required causes a
proportional increase or decrease in the
energy required to produce the PC2. Simi-
larly, an increase or decrease in yield
affects the volume required per radome.
Again, the increase/decrease in total en-
ergy requirements is approximately pro-
portional to the volume change.
Changes in the time required for
depainting do not have as great an effect
on the energy results. This is because
varying the time affects only the PC2 use
component, which is estimated to be about
3% of the total energy in the baseline.
Solid Waste
Total solid waste generation is de-
creased by about 50% for the recycled
system compared to the baseline system.
The reduction of fuel- and process-related
solid waste associated with the produc-
tion of the PC2 components is primarily
responsible for this reduction. However, a
small increase in fuel-related solid waste
results from the recycling process and
transportation to and from the recycling
facility.
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Table 1. Summary of Sources of Atmospheric and Waterborne Emissions
Source
Emission
Fuel acquisition and combustion
Incineration of spent PC2
Petroleum refining operation
Manufacture of ammonia as an intermediate
material and the operation to produce carbon
dioxide
Formaldehyde production and the operation to
produce adipic acid
Natural gas and crude oil production and
processing
Production ofpropylene oxide
Natural gas processing
Fuel acquisition and combustion
Process to make benzene (an intermediate for
DBE)
Manufacture of ammonia, hydrogen, carbon
dioxide, petroleum refinery operations
Production of ammonia, methanol, and nitric
acid intermediates for DBE
Petroleum refinery operations
Production of ammonia
Refined petroleum products and production of
sodium hydroxide (used in the manufacture of
DBE)
Sodium hydroxide production
Refining of petroleum products
Crude oil and natural gas production and
refining of petroleum products
Benzene and sodium hydroxide production
Processes to make ammonia and methanol, and
refinery operations
atmospheric aldehydes, ammonia, carbon monoxide, fossil carbon dioxide,
hydrocarbons, hydrogen chloride, kerosene, lead, methane, nitrogen oxides, other
organics, particulate emissions, sulfur oxides
carbon dioxide and nitrogen dioxide
process aldehyde
ammonia
carbon monoxide
hydrocarbon
process isobutane and propylene oxide
sulfur oxide
waterborne acid, ammonia, biochemical oxygen demand, chromium, chemical
oxygen demand, dissolved solids, iron, lead, metal ion, phenol, sulfuricacid, suspended
solids, zinc
process acid
process ammonia
process biochemical oxygen demand
chromium, phenol, zinc, chemical oxygen demand
chemical oxygen demand
dissolved solids
mercury, zinc, nickel
process metal ion
process oil
sulfide process
suspended solids
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As with the energy results, the total
solid waste is quite sensitive to assump-
tions made regarding the volume of PC2
required to depaint each radome. Because
over 60% of the solid waste is due to the
production and blending of the PC2 com-
ponents, any change in the amount of
PC2 required to depaint each radome has
a marked effect on the solid waste re-
sults. Changes in the volume required and
the yield result in fairly proportionate
changes in the PC2 production, distilla-
tion, and disposal components.
The process energy used at Tinker Air
Force Base is electricity; therefore, any
changes in the processing time (and cor-
responding electricity requirements) result
in substantial changes in electricity-related
fuel pollutants. The dramatic changes in
solid waste resulting from variations in
process time are due in large part to solid
waste from electricity generating plants
(e.g., ash from coal).
Atmospheric and Waterborne
Emissions
All but four emission categories show a
dramatic reduction in emission levels for
the recycled system. The exceptions are
the atmospheric emissions: DBE, NMP,
and PC (the PC Blend 2 chemical compo-
nents), and other organics. The PC2 com-
ponents are the assumed atmospheric
emission contributors during the PC2 use
step, and are estimated to remain un-
changed with the use of recycled PC2.
The other organic emissions increase for
the recycled system because they are so
closely related to the additional transpor-
tation fuel pollutants produced to trans-
port PC2 to Texas for recovery and back
to Tinker Air Force Base.
Increasing the yield (less PC2 required)
of PC2 required for the depainting opera-
tion resulted in decreased emissions
across the board, while decreasing the
yield (more PC2 required) resulted in in-
creased emissions. Again, most of the
changes observed are fairly proportionate
to the change in PC2 required, although
some categories are less sensitive to the
PC2 requirements.
A baseline depainting time of two hours
was assumed. For the analyses included
in this study, the depainting time was
halved and doubled. The comparison dem-
onstrated that decreasing the time to one
hour resulted in decreased emissions in
almost every category, while increasing
the time resulted in increased emissions.
The differences seen are fairly small for
most emission categories; however, sulfur
oxides, particulates, sulfuric acid, iron,
kerosene, and airborne lead emissions
change to a greater degree. This seems
to be a reflection of their close tie to
electricity consumption at Tinker Air Force
Base.
Partial Impact Results and
Discussion
The partial impact assessment results
for the atmospheric and waterborne emis-
sions from the use of PC2 aircraft radome
depainting solvent are discussed briefly
below. In the discussion, it is important to
note that "less potential impact" means
that, for a particular impact category, the
alternative system had no emissions that
were considered higher than the baseline
system, while at least one emission was
higher for the other system.
• When the 100% closed loop recy-
cling of PC2 system results were com-
pared to the baseline system, 20 im-
pact categories had less potential im-
pact, and 3 categories had inconclu-
sive results.
• A 20% increase in the volume of PC2
resulted in no significant potential im-
pact.
• A 20% decrease in the volume of
PC2 resulted in 23 impact categories
with less potential impact.
• A decrease in the yield to five aircraft
radomes depainted per 110 gallons
of PC2 resulted in no significant po-
tential impact.
• An increase in the yield to 20 aircraft
radomes depainted per 110 gallons
of PC2 resulted in 23 impact catego-
ries with less potential impact.
• An increase in depaint time to 4 hours
per radome resulted in no significant
potential impact.
• A decrease in depaint time to 1 hour
per radome resulted in 23 impact cat-
egories with less potential impact.
Improvement Analysis
The improvement alternatives have been
compared by their energy requirements,
produced emissions, and relative poten-
tial impact. An economic evaluation is also
provided to estimate the cost to supply
the new solvent (PC2), and the cost of
disposal or recovery of the used solvent
for each of the improvement alternatives.
This analysis is not a life cycle cost analy-
sis; instead, it analyzes the cost to Tinker
Air Force Base for various improvement
alternatives. The analysis assumes no new
capital equipment requirements for the
change-over from MEKto PC2 (no capital
expenditures will be required). Also, for
the 3 year and 5 year recycling scenarios,
the cost estimates are on a constant ba-
sis, and do not include any factor for es-
calation of material and disposal costs
over time. The cost estimates for the vari-
ous PC2 use/disposal alternatives are
summarized in Table 2.
In the baseline scenario, it is assumed
that new PC2 would be purchased each
year, and the spent solvent would be dis-
posed of at the Coffeyville, KS hazardous
waste incinerator. The total supply and
disposal cost is estimated at $38,841 per
year.
The first recycling scenario assumes a
3 year PC2 usage and recycling program,
which would be followed by incineration of
used solvent. For this scenario, new PC2
must be purchased the first year of opera-
tion. In subsequent years, 85% of the new
supply would be composed of recycled
PC2, and 15% would be new PC2 makeup.
The average 3 year cost is estimated at
$36,225, which is approximately $2,800
per year less than the baseline scenario.
The second recycling scenario is simi-
lar to the first, except it is based on a 5
year PC2 usage and recycling program.
For this scenario, the average annual cost
is estimated at $35,952 or $3,359 per
year less than the baseline scenario.
The relative increases/decreases in the
usage constraints are fairly proportionate
to their resulting change in costs. Increas-
ing/decreasing the volume required by 20%
results in an increased/decreased cost of
approximately 20%. Halving and doubling
the yield of PC2 has the effect of dou-
bling/halving the total costs, respectively.
Conclusions
The following represents a summary of
the conclusions reached for the life cycle
inventory, partial impact assessment, and
improvement analysis of the PC2 radome
depainting solvent. All changes are stated
as results of each alternative scenario as
compared to the baseline scenario.
For the Recycling Scenario:
• Total energy requirements decrease
by about 70%.
• Total solid waste is reduced by ap-
proximately 50%.
• Total atmospheric and waterborne
emissions show an average reduc-
tion of about 65%. However, the other
organic atmospheric emissions in-
crease by 28%.
• Recycling PC2 results in less poten-
tial impact, except for the ecosystem
potential impact category of ozone
depletion, and the human health cat-
egories of irritant/corrosive and
allergenicity.
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Table 2. Sensitivity of PC Blend 2 Costs to Demand
New PC2
Disposal1
Dollars/year1
Recovery/
Distillation
All costs are in constant dollars. Escalation of costs is not included in these estimates.
"Disposal by incineration.
cRepresents a one-time disposal of PC Blend 2 averaged over three years.
"Represents a one-time disposal of PC Blend 2 averaged over five years.
Total
Baseline (1,815 gallons/year)
Baseline w/recycling (3-year usage)
Baseline w/recycling (5-year usage)
Baseline w/+20% volume
Baseline w/-20% volume
Baseline w/+100% volume
Baseline w/-50% volume
31,218
13,528
9,990
37,462
24,974
62,436
15,609
7,623
2,724C
1,635"
9,148
6,098
15,246
3,812
.
19,973
23,968
-
-
-
-
38,841
36,225
35,592
46,609
31,073
77,682
19,421
• Total costs for the 3 year recycling
program show an average of a 7%
reduction in costs.
• Total costs for the 5 year recycling
program show an average of a 9%
reduction in costs.
By increasing the PC2 volume required
per radome by 20%:
• Total energy requirements increase
about 19%.
• Total solid waste increases about
14%.
• Total atmospheric and waterborne
emissions show an average increase
of about 19%.
• The overall potential impact on eco-
system quality and human health is
increased.
• Total costs show an increase of 20%.
By decreasing the PC2 volume required
per radome by 20%:
• Total energy requirements are re-
duced by about 19%.
• Total solid waste decreases about
14%.
• Total atmospheric and waterborne
emissions show an average decrease
of about 19%.
• The overall potential impact on eco-
system quality and human health is
decreased.
• Total costs show a decrease of 20%
By halving the yield from 10 to 5 ra-
domes per 110 gallons:
• Total energy requirements are re-
duced by only 2%.
• Total solid waste is reduced by 16%.
• Atmospheric and waterborne emis-
sions are reduced an average of 3%.
• The overall potential impact on eco-
system quality and human health is
decreased.
• Total costs were not calculated for
this scenario due to relatively small
differences.
By doubling the yield from 10 to 20
radomes per 110 gallons:
• Total energy requirements are re-
duced by 48%.
• Total solid waste is reduced by 34%.
• Total atmospheric and waterborne
emissions are reduced by an aver-
age of 47%.
• The overall potential impact on eco-
system quality and human health is
decreased.
• Total costs are reduced by 50%.
By halving the time required for
depainting from two to one hour per ra-
dome:
• Total energy requirements are re-
duced by only 2%.
• Total solid waste is reduced by 16%.
• Atmospheric and waterborne emis-
sions are reduced an average of 3%.
• The overall potential impact on eco-
system quality and human health is
decreased.
• Total costs were not calculated for
this scenario due to relatively small
differences.
By doubling the time required for
depainting from two to four hours per ra-
dome:
• Total energy requirements show an
increase of 4%.
• Total solid waste shows an increase
of 32%.
• Total atmospheric and waterborne
emissions increase by an average of
5%.
• The overall potential impact on eco-
system quality and human health is
increased.
• Total costs were not calculated for
this scenario due to relatively small
differences.
Based on an estimate of air emissions
with a process screening model, direct
emission of PC2 solvent vapors from
Tinker Air Force Base does not result in
significant known health problems to indi-
viduals outside the immediate working area
as defined within the scope of this study.
The full report was submitted in fulfill-
ment of Contract No. 68-C4-0020, WA 1-
07, to Lockheed Environmental Systems
and Technologies Company through Pur-
chase Order No. 07PPG8 from Lockheed
to Franklin Associates, Ltd., under spon-
sorship of the U.S. Environmental Protec-
tion Agency.
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R. Thomas is with Lockheed-Martin Environmental, Las Vegas, NV 89119.
W. E. Franklin is with Franklin Associates, Prarie Village, KS 66208.
Kenneth R. Stone and Johnny Springer, Jr., are the EPA Project Officers (see
below).
The complete report, entitled "Life Cycle Assessment for PC Blend 2 Aircraft
Radome Depainter," (Order No. PB96-207386 Cost: $38.00, 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 Officers 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
Penalty for Private Use $300
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