United States National Risk Management

Environmental Protection Research Laboratory

Agency Cincinnati, OH 45268

Research and Development EPA/600/SR-96/094 September 1996

Life Cycle Assessment for PC

Blend 2 Aircraft Radome

Depainter

Project Summary

R. Thomas and W. E. Franklin

This project was sponsored by the

Department of Defense Strategic Environmental 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 environmental solutions that improve mission

readiness for federal activities, this report was developed to determine the

potential environmental and economic

impacts of using an alternative chemical depainter for B-52 and KC-135 aircraft radomes at the U.S. Air Force Oklahoma City Air Logistics Center. A life

cycle assessment (LCA) was conducted

to identify the performance, cost, and

environmental impacts of propylene carbonate 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 required 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 determine 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 solvent 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 inventory, (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 aircraft radomes. Significant evaporation occurs 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 propylene 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% nmethyl-pyrrolidone (NMP), 25% dibasic

ester (DBE), and 25% propylene carbonate.

PC2 is not currently in use at Tinker

Air Force Base, therefore, several assumptions were made based on limited

knowledge of how PC2 would perform

and may not fully characterize actual performance. These assumptions comprise

the baseline PC2 use scenario presented

in the LCA. To balance the lack of experience in PC2 performance a number of

alternative PC2 use and waste management scenarios were also evaluated.
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Procedure

The study used a comprehensive approach which encompassed energy requirements, solid wastes, atmospheric

emissions, and waterborne wastes associated with and resulting from the production, 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 partial impact assessment used a classification system to categorize the atmospheric

and waterborne emissions into relevant

potential impact categories of ecosystem

and human health. A mass loading characterization model was then used to compare baseline impact results to a variety

of improvement alternatives. The improvement assessment used the results of the

Life Cycle Inventory (LCI) and impact assessments 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 approximately 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 requirements, 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, requiring only 3% of the total energy, is used to

transport the chemicals and materials to

the next step in the manufacturing process. The energy of material resource is

the inherent energy of petroleum, natural

gas, and coal when used as a raw material feedstock. It accounts for 53% of the

total energy requirements.

Energy requirements are categorized

into five basic sources: natural gas, petroleum, coal, nuclear, and other (i.e., geothermal, solar, hydropower, etc.). The majority of the energy is derived from natural gas and petroleum, which account for

69% and 23% of the total respectively.

These values include the energy of material resource attributed to natural gas and

petroleum when used as raw material feedstock. 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 produced for every 10 KC-135 radomes

depainted. The production of NMP, DBE,

and PC contribute 29%, 18%, and 11%,

respectively. The blending operation contributes 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 produced.

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 categories of emissions contribute significantly

to the total emissions. Portions of these

emission categories may also be attributed to process emissions. Table 1 summarizes the atmospheric and waterborne

emissions and their sources.

Results and Discussion of LCI

Sensitivity Analysis

The results of the LCI Sensitivity Analyses 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 incineration. For the recycled system, it is assumed that a recovery rate of approximately 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 during transport of the spent PC2 to a theoretical recycling facility in Texas, distillation 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 approximately 70%. The majority of this reduction comes from decreased process

and energy of material resource requirements in the back-end steps in the production of the DBE, PC and NMP components 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 required for distillation and transport of the

spent PC2 is about 25% of the total energy for the recycling system.

The energy results are also very sensitive to any changes in the volume and

yield assumptions. An increase or decrease in the volume required causes a

proportional increase or decrease in the

energy required to produce the PC2. Similarly, an increase or decrease in yield

affects the volume required per radome.

Again, the increase/decrease in total energy requirements is approximately proportional 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 decreased by about 50% for the recycled

system compared to the baseline system.

The reduction of fuel- and process-related

solid waste associated with the production 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 atmospheric aldehydes, ammonia, carbon monoxide, fossil carbon dioxide,

hydrocarbons, hydrogen chloride, kerosene, lead, methane, nitrogen oxides, other

organics, particulate emissions, sulfur oxides

Incineration of spent PC2 carbon dioxide and nitrogen dioxide

Petroleum refining operation process aldehyde

Manufacture of ammonia as an intermediate ammonia

material and the operation to produce carbon

dioxide

Formaldehyde production and the operation to carbon monoxide

produce adipic acid

Natural gas and crude oil production and hydrocarbon

processing

Production of propylene oxide process isobutane and propylene oxide

Natural gas processing sulfur oxide

Fuel acquisition and combustion waterborne acid, ammonia, biochemical oxygen demand, chromium, chemical

oxygen demand, dissolved solids, iron, lead, metal ion, phenol, sulfuric acid, suspended

solids, zinc

Process to make benzene (an intermediate for process acid

DBE)

Manufacture of ammonia, hydrogen, carbon process ammonia

dioxide, petroleum refinery operations

Production of ammonia, methanol, and nitric process biochemical oxygen demand

acid intermediates for DBE

Petroleum refinery operations chromium, phenol, zinc, chemical oxygen demand

Production of ammonia chemical oxygen demand

Refined petroleum products and production of dissolved solids

sodium hydroxide (used in the manufacture of

DBE)

Sodium hydroxide production mercury, zinc, nickel

Refining of petroleum products process metal ion

Crude oil and natural gas production and process oil

refining of petroleum products

Benzene and sodium hydroxide production sulfide process

Processes to make ammonia and methanol, and suspended solids

refinery operations
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As with the energy results, the total

solid waste is quite sensitive to assumptions 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 components, any change in the amount of

PC2 required to depaint each radome has

a marked effect on the solid waste results. Changes in the volume required and

the yield result in fairly proportionate

changes in the PC2 production, distillation, and disposal components.

The process energy used at Tinker Air

Force Base is electricity; therefore, any

changes in the processing time (and corresponding 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 components), and other organics. The PC2 components are the assumed atmospheric

emission contributors during the PC2 use

step, and are estimated to remain unchanged with the use of recycled PC2.

The other organic emissions increase for

the recycled system because they are so

closely related to the additional transportation fuel pollutants produced to transport PC2 to Texas for recovery and back

to Tinker Air Force Base.

Increasing the yield (less PC2 required)

of PC2 required for the depainting operation resulted in decreased emissions

across the board, while decreasing the

yield (more PC2 required) resulted in increased 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 demonstrated 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 emissions 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 recycling of PC2 system results were compared to the baseline system, 20 impact categories had less potential impact, and 3 categories had inconclusive results.

• A 20% increase in the volume of PC2

resulted in no significant potential impact.

• 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 potential impact.

• An increase in the yield to 20 aircraft

radomes depainted per 110 gallons

of PC2 resulted in 23 impact categories 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 categories with less potential impact.

Improvement Analysis

The improvement alternatives have been

compared by their energy requirements,

produced emissions, and relative potential 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 analysis; 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 MEK to PC2 (no capital

expenditures will be required). Also, for

the 3 year and 5 year recycling scenarios,

the cost estimates are on a constant basis, and do not include any factor for escalation of material and disposal costs

over time. The cost estimates for the various 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 disposed 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 operation. 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 similar 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. Increasing/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 doubling/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 approximately 50%.

• Total atmospheric and waterborne

emissions show an average reduction of about 65%. However, the other

organic atmospheric emissions increase by 28%.

• Recycling PC2 results in less potential impact, except for the ecosystem

potential impact category of ozone

depletion, and the human health categories of irritant/corrosive and

allergenicity.
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• 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 ecosystem 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 reduced 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 ecosystem quality and human health is

decreased.

• Total costs show a decrease of 20%

By halving the yield from 10 to 5 radomes per 110 gallons:

Table 2. Sensitivity of PC Blend 2 Costs to Demand

Dollars/yeara

Recovery/

New PC2 DisposalbDistillation Total

Baseline (1,815 gallons/year) 31,218 7,623 - 38,841

Baseline w/recycling (3-year usage) 13,528 2,724c 19,973 36,225

Baseline w/recycling (5-year usage) 9,990 1,635d 23,968 35,592

Baseline w/+20% volume 37,462 9,148 - 46,609

Baseline w/-20% volume 24,974 6,098 - 31,073

Baseline w/+100% volume 62,436 15,246 - 77,682

Baseline w/-50% volume 15,609 3,812 - 19,421

All costs are in constant dollars. Escalation of costs is not included in these estimates. b

Disposal by incineration.

c

Represents a one-time disposal of PC Blend 2 averaged over three years.

d

Represents a one-time disposal of PC Blend 2 averaged over five years.

• Total energy requirements are reduced by only 2%.

• Total solid waste is reduced by 16%.

• Atmospheric and waterborne emissions are reduced an average of 3%.

• The overall potential impact on ecosystem 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 reduced by 48%.

• Total solid waste is reduced by 34%.

• Total atmospheric and waterborne

emissions are reduced by an average of 47%.

• The overall potential impact on ecosystem 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 radome:

• Total energy requirements are reduced by only 2%.

• Total solid waste is reduced by 16%.

• Atmospheric and waterborne emissions are reduced an average of 3%.

• The overall potential impact on ecosystem 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 radome:

• 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 ecosystem 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 individuals outside the immediate working area

as defined within the scope of this study.

The full report was submitted in fulfillment of Contract No. 68-C4-0020, WA 1-

07, to Lockheed Environmental Systems

and Technologies Company through Purchase Order No. 07PPG8 from Lockheed

to Franklin Associates, Ltd., under sponsorship of the U.S. Environmental Protection 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

EPA/600/SR-96/094

BULK RATE

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EPA

PERMIT NO. G-35