December 2001
EPA-744-R-01-004a
Desktop Computer
Displays:
A Life-Cycle
Assessment
VOLUME 1
Maria Leet Socolof
Jonathan G. Overly
Lori E. Kincaid
Jack R. Geibig
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This document was produced by the University of Tennessee Center for Clean
Products and Clean Technologies under grant #82537401
from EPA's Design for the Environment Branch, Economics,
Exposure, & Technology Division, Office of Pollution
Prevention and Toxics.
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EXECUTIVE SUMMARY
EXECUTIVE SUMMARY
This report presents the results of a voluntary, cooperative project among the Design for
the Environment (DfE) Program in the Economics, Exposure, and Technology Division of the
U.S. Environmental Protection Agency's (EPA) Office of Pollution Prevention and Toxics, the
University of Tennessee (UT) Center for Clean Products and Clean Technologies, the electronics
industry, and other interested parties to develop a model and assess the life-cycle environmental
impacts of flat panel display (FPD) and cathode ray tube (CRT) technologies that can be used for
desktop computer displays. The DfE Computer Display Project (CDP) report provides a baseline
analysis and the opportunity to use the model as a stepping stone for further analyses and
improvement assessments for these technologies.
The DfE CDP uses life-cycle assessment (LCA) as an environmental evaluation tool that
looks at the full life cycle of the product from materials acquisition to manufacturing, use, and
final disposition. As defined by the Society of Environmental Toxicology and Chemistry, there
are four major components of an LCA study: goal definition and scoping, life-cycle inventory,
impact assessment, and improvement assessment. The more recent International Standards
Organizations definition of LCA includes the same first three components, but replaces the
improvement assessment component of LCA with a life-cycle interpretation component. LCAs
are generally global and non-site specific in scope.
The DfE CDP analysis also incorporates some elements of the Cleaner Technologies
Substitutes Assessment (CTSA) methodology (Kincaid et al, 1996), which was developed under
the DfE Program to help businesses make environmentally informed choices and design for the
environment. The CTSA process involves comparative evaluations of the relative human and
ecological risk, energy and natural resource use, performance, and cost of substitute technologies,
processes, products, or materials.
This project focuses on the LCA, while including some CTSA-related analyses. It
performs the broad analysis of the LCA, which also incorporates many of the CTSA components
(e.g., risk, energy impacts, natural resource use) into the impact assessment. The analysis also
assesses more specific impacts for selected materials and acknowledges product cost and
performance, typical of a CTSA. As only selected materials are qualitatively evaluated for the
CTSA, this project is an LCA with a streamlined CTSA component.
LCAs evaluate the environmental impacts from each of the following major life-cycle
stages: raw materials extraction/acquisition; materials processing; product manufacture; product
use, maintenance, and repair; and final disposition/end-of-life. The inputs (e.g., resources and
energy) and outputs (e.g., products, emissions, and waste) within each life-cycle stage, as well as
the interaction between each stage (e.g., transportation) are evaluated to determine the
environmental impacts.
In this study and project report, the goal and scope of the CDP are the subject of
Chapter 1. The life-cycle inventory (LCI), which involves the quantification of raw material and
fuel inputs, and solid, liquid, and gaseous emissions and effluents, is the subject of Chapter 2.
The life-cycle impact assessment (LCIA) involves the translation of the environmental burdens
identified in the LCI into environmental impacts and is the subject of Chapter 3. The
improvement assessment or life-cycle interpretation is left to the electronics industry given the
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EXECUTIVE SUMMARY
results of this study. The report also includes a qualitative risk screening of selected materials to
represent the CTSA component of the report in Chapter 4. The summary and conclusions are
presented in Chapter 5.
I. GOAL DEFINITION AND SCOPE
Purpose and Need
The purpose of this study is two-fold: (1) to establish a scientific baseline that evaluates
the life-cycle environmental impacts of active matrix liquid crystal display (LCD) and cathode
ray tube (CRT) technologies for desktop computers, by combining LCA and CTSA
methodologies; and (2) to develop a model that can be used with updated data for future life-
cycle analyses. This study is designed to provide the electronics industry with information
needed to improve the environmental attributes of desktop computer displays. The evaluation
considers impacts related to material consumption, energy, air resources, water resources,
landfills, human toxicity, and ecological toxicity. It is intended to provide valuable data not
previously published, and an opportunity to use the model developed for this project in future
improvement evaluations that consider life-cycle impacts. It will also provide the industry and
consumers with valuable information to make environmentally informed decisions regarding
display technologies, and enable them to consider the relative environmental merits of a
technology along with its performance and cost. While there has been some work done on the
life-cycle environmental impacts of either CRTs or LCDs, there has not been a quantitative LCA
of both CRTs and LCDs.
At present, computer displays using CRTs dominate worldwide markets. The LCD, first
used predominately in notebook computers, is now moving into the desktop computer market.
CRTs use larger amounts of energy to operate than LCDs, and are associated with disposal
concerns due to leaded glass in the displays. LCDs may consume more energy during
manufacturing and contain small amounts of mercury. Given the expected market growth of
LCDs for computer displays, the various environmental concerns throughout the life cycle of the
computer displays, and the fact that the relative life-cycle environmental impacts of LCDs and
CRTs have not been scientifically established to date, there is a need for an environmental life-
cycle assessment of both of these types of desktop computer display technologies.
Targeted Audience and Use of the Study
The electronics industry is expected to be one of the primary users of the study results.
The study is intended to provide industry with an analysis that evaluates the life-cycle
environmental impacts of selected computer display technologies. Another result of the study is
an accounting of the relative environmental impacts of various components of the computer
displays, thus identifying opportunities for product improvements to reduce potential adverse
environmental impacts and costs. Since this study incorporates a more detailed health effects
component than in traditional LCAs, the electronics industry can use the tools and data to
evaluate the health, environmental, and energy implications of the technologies. With this
evaluation, the U.S. electronics industry may be more prepared to meet the demands of extended
product responsibility that are growing in popularity in the global marketplace, and better able to
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EXECUTIVE SUMMARY
meet competitive challenges in the world market. In addition, the results and model in this study
will provide a baseline LCA upon which alternative technologies can be evaluated. This will
allow for more expedited display-related LCA studies, which are growing in popularity by
industry and may be demanded by original equipment manufacturers (OEMs) or international
organizations.
EPA and interested members of the public can also benefit from the results of the project.
The project has provided a forum for industry and public stakeholders to work cooperatively, and
the results can be used by stakeholders as a scientific reference for the evaluated display
technologies. The results of the project could also be of value to other industries involved in
designing environmental improvements into the life cycle of consumer products.
Product System
The product system being analyzed in this study is a standard desktop computer display
that functions as a graphical interface between computer processing units and users. Besides the
CRT display, several FPD technologies were considered for inclusion in this study. Among the
FPD technologies that exist, the amorphous silicon (a:Si) thin-film transistor- (TFT) active
matrix LCD technology meets the requirements of the functional unit within the parameters of
this analysis and is assessed in this study.
The product system is the computer display itself and does not include the central
processing unit (CPU) of the computer that sends signals to operate the display. It is assumed
that the LCDs operate with an analog interface, and therefore are compatible with current CRT
CPUs as plug-and-play alternatives.
In an LCA, product systems are evaluated on a functionally equivalent basis. The
functional unit is used as the basis for the inventory and impact assessment to provide a reference
to which the inputs and outputs are related. For this project, the functional unit is one desktop
computer display over its lifespan, which meets the functional unit specifications presented in
Table ES-1. The CRT technology is the current industry standard for this product system.
Table ES-1. Functional unit specifications
Specification
display size a
diagonal viewing area a
viewing area dimensions
resolution
brightness
contrast ratio
color
Measure
17" (CRT); 15" (LCD)
15.9" (CRT); 15" (LCD)
12.8" x 9.5" (122 in2) (CRT); 12" x 9"
(108 in2) (LCD)
1024x768 color pixels
200 cd/m2
100:1
262,000 colors
a An LCD is manufactured such that its nearest equivalent to the 17" CRT display is the 15" LCD. This is because
the viewing area of a 17" CRT is about 15.9 inches and the viewing area of a 15" LCD is 15 inches. LCDs are not
manufactured to be exactly equivalent to the viewing area of the CRT.
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EXECUTIVE SUMMARY
Assessment Boundaries
In a comprehensive cradle-to-grave analysis, the display system includes five life-cycle
stages: (1) raw materials extraction/acquisition; (2) materials processing; (3) product
manufacture; (4) product use, maintenance and repair; and (5) final disposition/end-of-life. Also
included are the activities that are required to affect movement between the stages (e.g.,
transportation).
The geographic boundaries of this assessment depend on the life-cycle stage. This LCA
focuses on the U.S. display market; therefore, the geographic boundary for the use and
disposition stages of displays is limited to the United States. The geographic boundaries for raw
material extraction, material processing, and product manufacture are worldwide (although actual
product manufacturing data were only collected from the United States, Japan, and Korea,
described in Chapter 2 of the report). While the geographic boundaries show where impacts
might occur for various life-cycle stages, traditional LCAs do not provide an actual spatial
relationship of impacts. That is, particular impacts cannot be attributed to a specific location.
Rather, impacts are generally presented on a global or regional scale.
Considering the temporal boundaries, this study addresses impacts from the life cycle of a
desktop computer display manufactured using 1997-2000 technology. The use and disposition
stages cover a period that represents the life of a display. The lifespan, labeled as the "effective"
life, is defined as the period of time the display is in use by primary, secondary, or even tertiary
users before reaching its final disposition. The effective life, used as the baseline scenario, is
estimated based on past and current use patterns of displays and represents a realistic estimate of
the lifespan. As the effective life is subject to many variables, including fluctuating market
trends, an alternative lifespan is presented in a sensitivity analysis. The alternative lifespan, or
"manufactured" life, defined as the designed durability of a display (e.g., the time a display or
key display component will operate before failing), is approximated based on the manufacturer's
estimated durability of the display.
Impacts from the infrastructure needed to support the manufacturing facilities (e.g.,
maintenance of manufacturing plants) are beyond the scope of this study. However, maintenance
of clean rooms used in the manufacturing of LCDs (and other components), which require
substantial amounts of energy, are considered part of the manufacturing process.
Impacts from the transportation and distribution of materials, products, and wastes
throughout the life-cycle of a display were originally included in the scope of the CDP LCA.
However, only a small part of the overall transport in the life of a monitor was either reported in
primary data collected for this project or available in secondary data. Inconsistencies between
primary and secondary transportation data sources and the overall poor quality of transport data
prevented an accurate assessment of the transportation inventory and impacts. Therefore,
transportation impacts were excluded from the analysis. Section 2.6 describes transport data
limitations and uncertainties in detail.
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EXECUTIVE SUMMARY
II. LIFE-CYCLE INVENTORY (LCI)
General Methodology
An LCI is the identification and quantification of the material and resource inputs and
emission and product outputs from the unit processes in the life cycle of a product system. For
the DfE CDP, LCI inputs include materials used in the computer display product itself, ancillary
materials used in processing and manufacturing the displays, and energy and other resources
consumed in the manufacturing, use, or final disposition of the displays. Outputs include
products, air emissions, water effluents, and releases to land. Figures ES-1 and ES-2 show the
unit processes that are included in the scope of this project for the CRT and LCD life cycles,
respectively.
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EXECUTIVE SUMMARY
CRADLE-TO-GATE STAGES
(Upstream and Manufacturing)
Japanese electric grid
[linked to manufacturing processes (*) below; upstream processes have imbedded
electricity generation inventory data]
USE STAGE
END-OF-LIFE STAGE
U.S. electric grid
(linked to use & EOL processes below; fuel processes
and secondary EOL processes have imbedded
electricity generation inventory data)
Notes'.
LPG = liquified petroleum gas
HIPS = high impact polystyrene
ABS = acrylonitrile butadiene styrene
PC = polycarbonate
* Manufacturing stage processes
Key:
primary
data
secondary
data
Figure ES-1. CRT linked processes
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EXECUTIVE SUMMARY
CRADLE-TO-GATE STAGES
(Upstream and Manufacturing)
Japanese electric grid
[linked to manufacturing processes (*) below; upstream processes have imbedded
electricity generation inventory data]
polarizer mfg*
*
PET mfg
steel mfg
aluminum
mfg
Notes:
PMMA = poly(methyl methyacrylate)
PC = polycarbonate
PET = polyethylene terphthalate
LPG = liquified petroleum gas
* Manufacturing stage processes
USE STAGE
END-OF-LIFE STAGE
U.S. electric grid
(linked to use & EOL processes below; fuel
processes and secondary EOL processes have
imbedded electricity generation inventory data)
patterning
color filters on
glass*
printed wiring
board mfg*
Key:
primary
data
secondary
data
Figure ES-2. LCD linked processes
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EXECUTIVE SUMMARY
Data were also collected on the final disposition of emissions outputs, such as whether
outputs are released directly to the environment, recycled, treated, and/or disposed. This
information helps determine which impacts will be calculated for a particular inventory item.
Methods for calculating impacts are discussed in Chapter 3, Life-cycle Impact Assessment.
Given the enormous amount of data involved in inventorying all of the inputs and outputs
for a product system, decision rules, based on the mass, environmental, energy, and functional
significance, were used to determine which materials or unit processes to include in the LCI.
Decision rules are designed to make data collection manageable while still representative of the
product system and its impacts. Data were collected from both primary and secondary sources.
Table ES-2 lists the types of data (primary or secondary) used for each life-cycle stage in the
CDP LCI. In general, greater emphasis was placed on collecting data and/or developing models
for the product manufacturing, use, and end-of-life life-cycle stages.
Table ES-2. Data types by life-cycle stage
Life-cycle stage
Upstream
(materials extraction and processing)
Product and component manufacturing
Use
Final disposition
(recycling and/or disposal)
Packaging, transportation, distribution
Data types
Secondary data.
Primary data, except secondary data used for frit.
Modeled using secondary data; maintenance and
included in the analysis.
Modeled using secondary data plus primary data
recycling facilities.
repair are not
from CRT
Not included.
In the CDP LCI, data were allocated to the functional unit (i.e., a desktop computer
display over its lifetime) as appropriate. The data that were collected for this study were either
obtained from questionnaires developed for this project (i.e., primary data) or from existing
databases (i.e., secondary data). LCI data were imported into a Life-Cycle Design Software Tool
developed by the UT Center for Clean Products and Clean Technologies with funding from the
EPA Office of Research and Development and Saturn Corporation. The UT Life-Cycle Design
Software Tool organizes data in such a way that each process inventory is independent.
Customized "profiles" (e.g., the manufacture of a CRT or the whole life-cycle of an LCD) can be
developed by linking processes.
LCI data quality was evaluated based on the following data quality indicators (DQIs): (1)
the source type (i.e., primary or secondary data sources); (2) the method in which the data were
obtained (i.e., measured, calculated, estimated); and (3) the time period for which the data are
representative. Any proprietary information required for the assessment was aggregated to
protect confidentiality.
A critical review process was maintained in the CDP LCA to help ensure that appropriate
methods were employed and study goals were met. A project Core Group and Technical Work
Group, both consisting of representatives from industry, academia, and government, including
EPA's DfE Work Group, provided critical reviews of the assessment. The Core Group served as
the project steering committee and was responsible for approving all major scoping assumptions
and decisions. The Technical Work Group and EPA's DfE Work Group provided technical
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EXECUTIVE SUMMARY
guidance and were given the opportunity to review all major project deliverables, including the
final LCA report.
Upstream Life-cycle Stage Methodology
The materials extraction and processing inventories for key materials were obtained from
a secondary LCI database developed by Ecobilan (1999). The U.S. electric grid inventory was
developed from secondary sources by UT. The U.S. electric grid inventory was then modified,
based on the distribution of fuels used in Japan, to develop the Japanese electric grid, which was
used where manufacturing occurs in Asia. Electricity consumed in the life-cycles of the monitors
was linked to the inventory of inputs and outputs from the U.S. or Japanese electric grid
inventories, as appropriate.
Manufacturing Stage Methodology
The inventories for the product manufacturing life-cycle stage were developed from
primary data collected from manufacturers in Asia and the United States. The manufacturing
processes included in the study, as well as the number of data sets for each process and the
country of origin of the data, are presented in Table ES-3. A total of 27 product manufacturing
questionnaires were collected for 11 different processes. Allocation of data to the functional unit
was conducted as necessary. Processes for which we collected more than one company's data
were averaged together.
The quality of the manufacturing stage data can be evaluated against two factors: (1) the
date of the data; and (2) the type of data (i.e., measured, calculated or estimated). The data
collection phase of this project began in 1997 and extended through 2000. Some processes are
more sensitive to production dates than others. Most processes included in this analysis are
mature technologies and are not expected to differ significantly between the years 1997 and
2000. However, an exception is LCD panel/module manufacturing, which is an evolving and
rapidly advancing process and has seen changes between these years. For the LCD panel and
module manufacturing process, most data were from 1998 and 1999.
Data quality indicators were developed based on whether data were measured, calculated,
or estimated, as reported in company data questionnaires. The weighted average of data
collected and their associated DQIs are as follows: for the CRT, 43% of the data were measured,
34% calculated, 13% estimated, and 10% were not classified. For the LCD, a similar distribution
shows 33% measured, 30% calculated, 23% estimated, and 14% not classified.
Product Use Life-cycle Stage Methodology
The baseline analysis in this project employs an effective life use stage scenario (the
actual amount of time a monitor is used, by one or multiple users, before it is disposed of,
recycled, or re-manufactured). A manufactured life scenario (the amount of time either an entire
monitor or a single component will last before reaching a point where the equipment no longer
functions, independent of user choice) is evaluated in a sensitivity analysis.
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EXECUTIVE SUMMARY
Table ES-3. Location of companies and number of process data sets
Process
CRT monitor assembly
CRT (tube) manufacturing
CRT leaded glass manufacturing
CRT frit manufacturing
LCD monitor assembly
LCD panel and module manufacturing a
LCD - glass manufacturing
LCD - color filter patterning on front glass
LCD - liquid crystal manufacturing
LCD - polarizer manufacturing
LCD - backlight unit assembly
LCD - backlight light guide manufacturing
LCD - cold cathode fluorescent lamp (CCFL) manufacturing
PWB manufacturing (for CRT and LCD monitors)
Country of origin of data
(# of data sets)
Japan (2), U.S. (1)
Japan (2), U.S. (1)
Japan (1), U.S. (2)
generic secondary data from the U.S.
Japan (2)
Japan (5), Korea (2)
Japan and U.S. (1) b
Japan (1)
Japan (2)
Japan (1)
Japan (3)
Japan (1)
Japan (1)
generic secondary data from the U.S.
a The LCD panel consists of two glass panels patterned with transistors and color filters, liquid crystals inserted
between the panels, and associated row and column drivers. The LCD module consists of the panel, backlight unit,
and associated electronic boards for the entire panel, and the backlight.
The average of three data sets for CRT leaded glass manufacturing was modified to remove lead from the
inventory.
To develop the use stage inventory, energy use rates [e.g., kilowatts (kW)] were
combined with the time a desktop monitor is on during its lifespan (hours/life) to calculate the
total quantity of electrical energy consumed during the use life-cycle stage [e.g., kilowatthours
(kWh)/life]. This was then combined with the electric grid inventory of inputs and outputs per
kWh to make up the use stage inventory per monitor. The effective life scenario models the
actual quantity of hours that an average monitor spends in each of the two primary power
consumption modes (full-on and a lower power state) during its lifetime. Assumptions used to
calculate the kilowatthours per effective life are detailed in Section 2.4. The total electricity
consumption for each monitor was calculated to be 634 kWh/effective life (2,282 MJ/effective
life) for the CRT and 237 kWh/effective life (853 MJ/effective life) for the LCD.
End-of-life (EOL) Methodology
For the EOL analysis, a monitor is assumed to have reached EOL status when:
• it has served its useful life;
• is no longer functional; and/or
• is rendered unusable due to technological obsolescence.
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EXECUTIVE SUMMARY
The major EOL dispositions considered in this analysis are as follows:
• recycling - including disassembly and materials recovery;
• landfilling - including hazardous [Resource Conservation and Recovery Act (RCRA),
Subtitle C] and non-hazardous (RCRA, Subtitle D) landfills;
• remanufacturing - including refurbishing or reconditioning (to make usable again); and
• incineration - waste to energy incineration.
The functional unit in this analysis is one monitor; therefore, the different EOL
dispositions were allocated as a probability of one monitor going to a certain EOL disposition.
Data were somewhat scarce on the percent of monitors going to each disposition, especially for
LCD monitors, which have not as yet reached EOL. After literature research and consultation
with the project's Technical Work Group, as well as various other industry experts, project
partners chose best estimates of disposition distributions (Table ES-4).
Table ES-4. Distribution of EOL disposition assumptions for the CRT and LCD
Disposition
Incineration
Recycling
Remanufacturing
Hazardous waste landfill
Solid waste landfill
CRT
15%
11%
3%
46%
25%
LCD
15%
15%
15%
5%
50%
Sources: NSC, 1999; EPA, 1998; CIA, 1997; EIA, 1999; Vorhees, 2000; TORNRC, 2001
Primary data were collected for CRT recycling from three companies. The data from
these companies represent facility operations ranging from October 1999 to February 2000. In
the absence of actual data for LCD recycling, data on a CRT shredding-and-materials-recovery
process was used to model LCD recycling.
Hazardous/solid waste landfilling and incineration were developed from secondary data
obtained from Ecobilan. Although data specific to landfilling and incineration operations for
monitors alone were not available, existing inventories were available for landfilling and
incinerating the following major monitor materials (by weight): steel, glass, plastic, and
aluminum. These inventories were combined, based on the approximate proportion of each
material in a CRT and an LCD, to create individual processes for landfilling and for incineration
(for each monitor type). The majority of the assembled monitors by weight is accounted for in
the overall incineration and landfilling processes.
Remanufacturing data were excluded from the assessment because no single set of
operations could be identified to adequately represent remanufacturing activities that could be
incorporated in our model.
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EXECUTIVE SUMMARY
LCI Limitations and Uncertainties
Several factors contribute to the overall quality of data for each life-cycle stage. For
example, the manufacturing stage includes several different processes that were collected from
several different companies. The quality of one data set from one company may be very different
from that of another company. Relative data quality estimates have been made for each life-cycle
stage, including electricity generation, which is included in the results of more than one life-cycle
stage (Table ES-7). The table also lists the major limitations associated with each life-cycle
stage.
Table ES-7. Relative data quality and major limitations
Life-cycle stage
Upstream
Manufacturing
Use
EOL
Electricity generation
Relative data quality
Moderate
Moderate to high
Moderate to high
Low to moderate
High
Major limitations
Used only secondary data, which has undetermined
quality and not originally collected for the purpose of
the CDP.
A few data points remain in question.
Assumptions regarding use patterns were made.
Used only secondary data for incineration and
landfilling processes; no data available for
remanufacturing process.
Used secondary data, however it was collected and
modeled for the CDP, resulting in a higher quality
rating despite use of secondary data.
Although the manufacturing stage was rated in Table ES-7 as having moderate to high
data quality, some of the few data points that remained in question had large effects on the results
and are therefore described below. Of the data collected from manufacturers, several attempts
were made to verify or eliminate outliers in the data; however, uncertainty in some data remained
due to large data ranges and outliers. Specific data with the greatest uncertainty include: (1) LCD
glass manufacturing data; (2) CRT and LCD glass manufacturing energy inputs; (3) the
distribution and amount of fuel/electricity inputs for LCD module manufacturing; and (4) the use
of a large amount of liquified natural gas (LNG) as an "ancillary material" in LCD module
manufacturing and not as a fuel.
Uncertainties in the LCD glass manufacturing data stem from the fact that no LCD glass
manufacturers were willing to supply inventory data. Therefore, the LCD glass manufacturing
inventory was derived from the CRT glass manufacturing data modified to exclude leaded
compounds from the inventory. Thus, the baseline analysis in this study assumes the energy use
per kilogram of CRT glass and LCD glass are equivalent, which is uncertain. In addition to the
uncertainty in the difference between energy used to manufacture CRT glass and LCD glass, the
energy reported to produce a kilogram of CRT glass varied greatly between the three data sets
received for this project, with the highest total energy value being about 150 times that of the
smallest value. Due to this large discrepancy and because there were not enough data sets to
evaluate the data for outliers, the glass energy data were evaluated in a sensitivity analysis. The
high glass energy use values were mostly a function of liquefied petroleum gas (LPG) used as a
fuel.
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EXECUTIVE SUMMARY
Other data for which large ranges were reported, and which could be important to the
results, are energy data from LCD panel/module manufacturing. Energy data provided by six
LCD panel/module manufacturers were highly variable in both the distribution of energy sources
and the total energy required to produce one LCD panel. The percent of energy from electricity
ranged from approximately 3% to 87%, and the total energy per panel ranged from 440 MJ to
7,000 MJ. The average energy use per panel was approximately 2,270 MJ, and the standard
deviation was about 2,910 MJ.
Given the wide variability in the data and large standard deviation, CDP researchers
evaluated these data for outliers. One data set was found to be a minor outlier and another was
found to be a major outlier. These outliers were excluded from the averages used in the baseline
analysis, but included in the averages used in a sensitivity analysis (see Section 2.7.3.3).
Finally, a large amount of LNG (194 kg, on average) was reported to be used as an
ancillary material (not a fuel) in LCD panel/module manufacturing. CDP researchers confirmed
this application of LNG and the amount with the company providing the data, but it is still
uncertain due to problems in communication (e.g., the language barrier). This data point
remained in the inventory data set for LCD manufacturing, and was assumed to indeed be an
ancillary material, and not a fuel. Keeping the LNG ancillary material in the inventory will not
affect the energy impact results, since LNG used as an ancillary material is only linked to the
production of that material, and not to the use of it as a fuel.
Baseline LCI Results
Tables ES-5 and ES-6 present the total quantity of inputs and outputs for each life-cycle
stage of the CRT and LCD based on input and output types.
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Table ES-5. CRT inventory by life-cycle stage
Inventory type
Upstream
Mfg
Use
EOL
Total
Units a
Inputs
Primary materials
Ancillary materials
Water
Fuels
Electricity
Total energy
1.58e+01
2.11e+00
5.54e+02
8.00e+00
7.32e+01
3.66e+02
4.21e+02
3.54e+00
1.14e+04
4.28e+02
1.29e+02
1.83e+04
2.19e+02
3.47e+00
1.14e+03
0
2.29e+03
2.29e+03
-3.32e+00
1.07e+01
-2.73e+01
-2.95e+00
2.29e-01
-1.28e+02
6.53e+02
1.98e+01
1.31e+04
4.33e+02
2.49e+03
2.08e+04
kg
kg
kg (or L)
kg
MJb
MJb
Outputs
Air pollutants
Wastewater
Water pollutants
Hazardous waste
Solid waste
Radioactive waste
Radioactivity
3.00e+01
1.70e+01
8.12e-01
4.89e+02
9.55e+00
4.39e-04
3.80e+07
1.83e+02
1.51e+03
2.01e+01
1.13e+02
8.12e+01
1.80e-04
3.78e+06
4.49e+02
0
7.02e-02
0
8.33e+01
2.28e-03
4.80e+07
2.47e+00
-3.65e+00
-6.18e-02
8.28e+00
-1.66e+00
2.29e-07
4.80e+03
6.64e+02
1.52e+03
2.09e+01
9.46e+00
1.72e+02
2.90e-03
8.98e+07
kg
kg (or L)
kg
kg
kg
kg
Bq
Per functional unit (i.e., one CRT monitor over its effective life).
b3.6MJ=lkWh
Table ES-6. LCD inventory by life-cycle stage
Inventory type
Upstream
Mfg
Use
EOL
Total
Units a
Inputs
Primary materials
Ancillary materials
Water
Fuels
Electricity
Total energy
2.35e+02
1.06e+00
2.63e+02
1.47e+01
3.46e+01
6.33e+02
4.92e+01
2.04e+02
2.15e+03
2.58e+01
3.16e+02
1.44e+03
8.01e+01
1.29e+00
4.25e+02
0
8.53e+02
8.53e+02
-2.19e+00
2.11e+00
-1.80e+01
-1.95e+00
1.62e-01
-8.44e+01
3.62e+02
2.08e+02
2.82e+03
3.86e+01
1.20e+03
2.84e+03
kg
kg
kg
kg(orL)
MJb
MJb
Outputs
Air pollutants
Wastewater
Water pollutants
Hazardous waste
Solid waste
Radioactive waste
Radioactivity
1.12e+02
8.57e+00
4.60e-01
6.72e-03
1.31e+01
2.21e+01
1.20e+07
6.48e+01
3.12e+03
1.23e+00
4.64e+00
1.26e+01
3.14e+03
1.02e+07
1.68e+02
0
2.62e-02
0
3.11e+01
3.11e+01
1.79e+07
1.30e+00
-2.41e+00
-4.09e-02
1.64e+00
-4.42e+00
-5.23e+00
3.40e+03
3.46e+02
3.13e+03
1.68e+00
6.29e+00
5.23e+01
3.19e+03
4.01e+07
kg
kg
kg(orL)
kg
kg
kg
Bq
Per functional unit (i.e., one LCD monitor over its effective life).
b3.6MJ=lkWh
ES-14
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EXECUTIVE SUMMARY
The total inventory results for life-cycle inputs reveal that more primary materials,1 water,
fuels, electricity, and total energy (i.e., fuel energy plus electricity) are used throughout the CRT
life-cycle, while more ancillary materials are used throughout the LCD life-cycle. For the life-
cycle outputs, the CRT releases more air emissions; water pollutants; hazardous, solid, and
radioactive waste; and radioactivity than the LCD. The LCD releases more total wastewater than
the CRT. Complete inventory tables for each input and output type by life-cycle stage for the
CRT and LCD are provided in Appendix J.
For the CRT (Table ES-5), of the inputs measured in mass, the water inputs in the
manufacturing life-cycle stage constitute the majority of the inputs for the entire life cycle.
Water inputs from the LPG production process constitute almost 80% of the water inputs for all
life-cycle stages. In this inventory, the LPG is used in large quantities as a fuel in CRT glass
manufacturing. When considering which life-cycle stage contributes most to an inventory
category, the manufacturing stage has the largest inventory by mass for primary materials,
ancillary materials, water inputs, and fuel inputs. This is also due to the production of LPG as
needed for CRT glass production. Fuel inputs are dominated by the manufacturing stage and
electricity inputs are dominated by the use stage. The total energy (which is calculated by
converting the mass of the fuel into units of energy and combining the fuel energy with the
electrical energy) is dominated by the manufacturing life-cycle stage, again mostly due to the
large LPG fuel energy used in CRT glass production.
CRT outputs measured in mass include air emissions, wastewater, water pollutants, and
hazardous, solid, and radioactive waste. Wastewater, by mass (or volume), constitutes the
greatest output; however, total wastewater volume is not used to calculate water-related impacts.
Instead, individual water pollutants are used to calculate water-related impacts. Of the remaining
outputs measured in mass, which are used to calculate impacts (i.e., air emissions, and hazardous,
solid and radioactive waste), air emissions are the greatest contributor to outputs in mass. Note
that radioactivity is measured in Bequerels (Bq) and cannot be compared on the same scale.
Considering each CRT inventory type and their contributions by life-cycle stage, the mass
of wastewater and water pollutants are greatest in the manufacturing life-cycle stage (again due to
LPG consumption). The outputs of air emissions, hazardous waste, solid waste, radioactive
waste, and radioactivity all have the greatest contribution from the use stage.
For the CRT outputs, all the totals represented in Table ES-5 include outputs to all
dispositions. For example, water outputs sent offsite to treatment as well as those directly
discharged to surface waters are all included. Similarly, hazardous, solid and radioactive waste
outputs may be landfilled, treated, or recycled. The inventory shows these as totals; however,
when impacts are calculated, the dispositions dictate which inventory items will be used to
calculate impacts (Chapter 3).
For the LCD (Table ES-6), of the inputs measured in mass, the water inputs constitute the
majority of the inputs for the entire life cycle, and most of the water inputs are in the
manufacturing life-cycle stage. When considering which life-cycle stage contributes most to an
inventory category, the manufacturing stage has the largest inventory by mass for ancillary
materials, fuels, and water inputs. Primary material inputs are dominated by the upstream stages,
Note that the total mass of primary materials includes the inputs to each process, which may duplicate
materials used in processes subsequent to other processes. For example, the primary materials used in steel
production are added to the steel used as a primary material for monitor assembly.
ES-15
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EXECUTIVE SUMMARY
while electricity inputs are dominated by the use stage. The total energy is dominated by the
manufacturing life-cycle stage. Note that LPG production from glass manufacturing does not
dominate much of the LCD inventory as it did for the CRT, because of the smaller amount of
glass used in the LCD compared to the CRT.
Of the LCD outputs measured in mass (air emissions, wastewater, water pollutants and
hazardous, solid, and radioactive waste), wastewater constitutes the greatest output; however,
total wastewater volume alone is not used to calculate impacts. Of the remaining outputs
measured in mass, which are used to calculate impacts (i.e., air emissions, water pollutants, and
hazardous, solid and radioactive waste), air emissions are the greatest contributor to the outputs.
Note again, as mentioned for the CRT, that radioactivity is measured in Bequerels (Bq) and
cannot be compared on the same scale.
Considering each LCD output type and their contributions by life-cycle stage, the mass of
water pollutants is greatest in the manufacturing life-cycle stage, due to the fuel production
processes that support fuel consumption in the manufacturing processes being included in the
manufacturing life-cycle stage. Wastewater and hazardous waste outputs are greatest in the
manufacturing stage; air emissions, solid waste, radioactive waste, and radioactivity have the
greatest contribution from the use stage. As with the CRT, all the output totals represented in
Table ES-6 include outputs to all dispositions.
III. LIFE-CYCLE IMPACT ASSESSMENT (LCIA)
LCIA Methodology
LCIA involves the translation of the environmental burdens identified in the LCI into
environmental impacts. LCIA does not seek to determine actual impacts, but rather to link the
data gathered from the LCI to impact categories and to quantify the relative magnitude of
contribution to the impact category (Fava et al, 1993; Barnthouse et al, 1997). Further, impacts
in different impact categories are generally calculated based on differing scales and therefore
cannot be directly compared.
Within LCA, the LCI is a well established methodology; however, LCIA methods are less
well defined and continue to evolve (Barnthouse et al., 1997; Fava et al., 1993). For toxicity
impacts in particular, there are some methods being applied in practice (e.g., toxicity potentials,
critical volume, and direct valuation) (Guinee et a/., 1996; ILSI, 1996; Curran, 1996), while
others are in development. However, there is currently no general consensus among the LCA
community as to one method over another.
The UT LCIA methodology employed in this study calculates life-cycle impact category
indicators for a number of traditional impact categories, such as global warming, stratospheric
ozone depletion, photochemical smog, and energy consumption. Furthermore, the method
calculates relative category indicators for potential chronic human health, aquatic ecotoxicity,
and terrestrial ecotoxicity impacts in order to address project partner's interest in human and
ecological toxicity and to fill a common gap in LCIAs.
LCIAs generally classify the consumption and loading data from the inventory stage into
various impact categories (know as "classification"). "Characterization" methods are then used
to quantify the magnitude of the contribution that loading or consumption could have in
producing the associated impact. The impact categories included in the CDP LCIA are as
ES-16
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EXECUTIVE SUMMARY
follows: renewable resource use, nonrenewable materials use/depletion, energy use, solid waste
landfill use, hazardous waste landfill use, radioactive waste landfill use, global warming,
stratospheric ozone depletion, photochemical smog, acidification, air quality (particulate matter
loading), water eutrophication (nutrient enrichment), water quality (biological oxygen demand
[BOD] and total suspended solids [TSS]), radioactivity, chronic human health effects
(occupational and public), aesthetic impacts (odor), aquatic ecotoxicity, and terrestrial
ecotoxicity.
Classification of an inventory item into impact categories depends on whether the
inventory item is an input or output, what the disposition of the output is, and in some cases the
material properties of the inventory item. Outputs with direct release dispositions are classified
into impact categories for which impacts will be calculated in the characterization phase of the
LCIA. Outputs sent to treatment or recycle/reuse are considered inputs to treatment or
recycle/reuse processes and impacts are not calculated until direct releases from these processes
occur. Once impact categories for each inventory item are classified, life-cycle impact category
indicators are quantitatively estimated through the characterization step.
The characterization step of LCIA includes the conversion and aggregation of LCI results
to common units within an impact category. Different assessment tools are used to quantify the
magnitude of potential impacts, depending on the impact category. Three types of approaches
are used in the characterization method for the CDP:
• Loading - An impact score is based on the inventory amount (e.g., resource use).
• Equivalency - An impact score is based on the inventory amount weighed by a certain
effect, equivalent to a reference chemical [e.g., global warming impacts relative to carbon
dioxide (CO2)].
Full equivalency - all substances are addressed in a unified, technical model.
Partial equivalency - a subset of substances can be converted into equivalency
factors.
• Scoring of inherent properties - An impact score is based on the inventory amount
weighed by a score representing a certain effect for a specific material (e.g., toxicity
impacts are weighed using a toxicity scoring method).
The scoring of inherent properties method is employed for the human and ecological
toxicity impact categories, based on the CHEMS-1 method described by Swanson et al. (1997).
The scoring method provides a hazard value (HV) for each potentially toxic material, which is
then multiplied by the inventory amount to calculate the toxicity impact score.
Using the various approaches, the UT LCIA method calculates impact scores for each
inventory item for each applicable impact category. Impact scores are therefore based on either a
direct measure of the inventory amount or some modification (e.g., equivalency or scoring) of
that amount based on the potential effect the inventory item may have on a particular impact
category. The specific calculation methods for each impact category are detailed in Chapter 3.
Impact scores are then aggregated within each impact category to calculate the various life-cycle
impact category indicators.
ES-17
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EXECUTIVE SUMMARY
General LCIA Methodology Limitations and Uncertainties
The purpose of an LCIA is to evaluate the relative potential impacts of a product system
for various impact categories. There is no intent to measure the actual impacts or provide spatial
or temporal relationships linking the inventory to specific impacts. The LCIA is intended to
provide a screening-level evaluation of impacts. In addition to lacking temporal or spatial
relationships and providing only relative impacts, LCA is also limited by the availability and
quality of the inventory data. Data collection can be very time consuming and expensive.
Confidentiality issues may also inhibit the availability of primary data.
Uncertainties are inherent in each parameter used to calculate impacts. For example,
toxicity data require extrapolations from animals to humans and from high to low doses (for
chronic effects) and can have a high degree of uncertainty.
Uncertainties also are inherent in chemical ranking and scoring systems, such as the
scoring of inherent properties approach used for human health and ecotoxicity effects. In
particular, systems that do not consider the fate and transport of chemicals in the environment
can contribute to misclassifications of chemicals with respect to risk. Also, uncertainty is
introduced where it was assumed that all chronic endpoints are equivalent, which is likely not the
case. The human health and ecotoxicity impact characterization methods presented here are
screening tools that cannot substitute for more detailed risk characterization methods. However,
it should be noted that in LCA, chemical toxicity is often not considered at all. This
methodology is an attempt to consider chemical toxicity where it is often ignored.
Uncertainty in the inventory data depends on the responses to the data collection
questionnaires and other limitations identified during inventory data collection. These
uncertainties are carried into impact assessment. In this LCA, there was uncertainty in the
inventory data, which included but was not limited to the following:
• missing individual inventory items,
• missing processes or sets of data,
• measurement uncertainty,
• estimation uncertainty,
• allocation uncertainty/working with aggregated data, and
• unspeciated chemical data.
The goal definition and scoping process helped reduce the uncertainty from missing data,
although it is certain that some missing data still exist. As far as possible, the remaining
uncertainties were reduced primarily through quality assurance/quality control measures (e.g.,
performing systematic double-checks of all calculations on manipulated data).
Baseline LCIA Results
Table ES-8 presents the baseline CRT and LCD LCIA indicator results for each impact
category. Appendix M presents complete LCIA results by material, process, and life-cycle stage.
The indicator results presented in Table ES-8 are the result of the characterization step of LCIA
methodology where LCI results are converted to common units and aggregated within an impact
ES-18
-------
EXECUTIVE SUMMARY
category. Note that the impact category indicator results are in a number of different units and
therefore can not be summed or compared across impact categories.
As shown in the table, under the baseline conditions the CRT indicators are greater than
the LCD indicators in the following categories: renewable resource use, nonrenewable resource
use, energy use, solid waste landfill use, hazardous waste landfill use, radioactive waste landfill
use, global warming, ozone depletion, photochemical smog, acidification, air particulates,
biological oxygen demand (BOD), total suspended solids (TSS), radioactivity, chronic public
health effects, chronic occupational health effects, aesthetics, and terrestrial toxicity. The LCD
indicators are greater than the CRT indicators in the following categories: water eutrophication
and aquatic toxicity. In addition, as noted in Table ES-8, if phased-out substances are removed
from the CRT and LCD inventories, the LCD ozone depletion indicator would exceed that of the
CRT. Details of each impact category and major contributors to the impacts in those categories
are presented in Chapter 3.
Summary of Top Contributors by Impact Category
Tables ES-9 and ES-10 summarize the top contributors to CRT and LCD life-cycle
impacts by impact category. As shown in Table ES-9, CRT impacts are largely driven by two
factors: (1) the large amount of LPG fuel used in CRT glass/frit manufacturing, and (2) the
relatively large amount of electricity consumed during the use stage. The LPG production
process yields the CRT's top contributor in eight of 20 impact categories. Most of this LPG is
used as a fuel source in CRT glass manufacturing in the glass/frit process group, which, in turn,
produces the top contributor to two of 20 impact categories. Thus, LPG used in the glass/frit
process group (primarily CRT glass manufacturing) is ultimately the key driver for CRT impacts
in ten categories. Similarly, outputs from electricity generation during the use stage result in the
Table ES-8. Baseline life-cycle impact category indicators"
Impact category
Renewable resource use
Nonrenewable resource use
Energy use
Solid waste landfill use
Hazardous waste landfill use
Radioactive waste landfill use
Global warming
Ozone depletion
Photochemical smog
Acidification
Air particulates
Water eutrophication
Water quality, BOD
Water quality, TSS
Radioactivity
Units per monitor
kg
kg
MJ
m3
m3
m3
kg-CO2 equivalents
kg-CFC- 1 1 equivalents
kg-ethene equivalents
kg-SO2 equivalents
kg
kg-phosphate equivalents
kg
kg
Bq
CRT
1.31E+04
6.68E+02
2.08E+04
1.67E-01
1.68E-02
1.81E-04
6.95E+02
2.05E-05b'c
1.71E-01
5.25E+00
3.01E-01
4.82E-02
1.95E-01
8.74E-01
3.85E+07d
LCD
2.80E+03
3.64E+02
2.84E+03
5.43E-02
3.61E-03
9.22E-05
5.93E+02
1.37E-05b
1.41E-01
2.96E+00
1.15E-01
4.96E-02
2.83E-02
6.15E-02
1.22E+07d
ES-19
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EXECUTIVE SUMMARY
Table ES-8. Baseline life-cycle impact category indicators"
Impact category
Chronic health effects, occupational
Chronic health effects, public
Aesthetics (odor)
Aquatic toxicity
Terrestrial toxicity
Units per monitor
tox-kg
tox-kg
m3
tox-kg
tox-kg
CRT
9.34E+02
1.98E+03
7.58E+06
2.25E-01
1.97E+03
LCD
6.96E+02
9.02E+02
5.04E+06
5.19E+00
8.94E+02
a Bold indicates the larger value within an impact category when comparing the CRT and LCD.
Several of the substances included in this category were phased out of production by January 1, 1996. Excluding
phased out substances decreases the CRT ozone depletion indicator to 1.09E-05 kg CFC-11 equivalents per monitor
and the LCD ozone depletion indicator to 1.18E-05 kg CFC-11 equivalents per monitor. These ozone depletion
indicators are probably more representative of the CDP temporal boundaries and current operating practices. See
section 3.3.6 for details.
0 Although the CRT indicator appears larger than the LCD indicator, uncertainties in the inventory make it difficult
to determine which monitor has the greater value. Therefore, this value is not shown in bold.
Radioactivity impacts are being driven by radioactive releases from nuclear fuel reprocessing in France, which are
included in the electricity data in some of the upstream, materials processing data sets. See section 3.3.12 for details.
top contributor to seven CRT impact categories. Note that in 14 of the 20 impact categories, the
top contributor to CRT impacts is responsible for more than 50% of impacts.
LCD impacts are not as dominated by a few data points, but a few processes (LCD
monitor/module manufacturing and electricity generation in the use stage) are responsible for a
large percent of the impacts. As shown in Table ES-10, both of these processes result in the top
contributors to six LCD impact categories each. In addition, the process to produce LNG used as
an ancillary material in LCD monitor/module manufacturing is the top contributor to an
additional impact category (photochemical smog). Note that in 11 of the 20 impact categories,
the top contributor to LCD impacts is responsible for more than 50% of impacts.
As a number of the impact results for both monitor types, and for the CRT in particular,
are being driven by a few data points with relatively high uncertainty, sensitivity analyses of the
baseline results were also conducted.
Table ES-9. Summary of top contributors to CRT impacts by impact category
Impact category
Renewable resource
use
Nonrenewable
resource use
Energy use
Solid waste landfill
use
Top contributors
Life-cycle
stage
Manufacturing
Manufacturing
Manufacturing
Use
Process group
LPG production
LPG production
CRT glass/frit mfg.
U.S. electric grid
Material
water
Petroleum (in ground)
Liquefied petroleum
gas
Coal waste
Contribution
to impact
score
79%
56%
72%
38%
ES-20
-------
EXECUTIVE SUMMARY
Table ES-9. Summary of top contributors to CRT impacts by impact category
Impact category
Hazardous waste
landfill use
Radioactive waste
landfill use
Global warming
Ozone depletion
Photochemical smog
Acidification
Air particulates
Water eutrophication
Water quality, BOD
Water quality, TSS
Radioactivity
Chronic health effects,
occupational
Chronic health effects,
public
Aesthetics (odor)
Aquatic toxicity
Terrestrial toxicity
Top contributors
Life-cycle
stage
End-of-life
Use
Use
Use
Manufacturing
Use
Manufacturing
Manufacturing
Manufacturing
Manufacturing
Materials
Processing
Manufacturing
Use
Manufacturing
Manufacturing
Use
Process group
CRT landfilling
U.S. electric grid
U.S. electric grid
U.S. electric grid
LPG production
U.S. electric grid
LPG production
LPG production
LPG production
LPG production
Steel production, cold-
rolled, semi-finished
CRT glass/frit
manufacturing
U.S. electric grid
LPG production
CRT tube
manufacturing
U.S. electric grid
Material
EOL CRT monitor,
landfilled
Low-level radioactive
waste
Carbon dioxide
Bromomethane
Hydrocarbons,
unspeciated
Sulfur dioxide
PM
COD
BOD
Suspended solids
Plutonium-241
(isotope)
Liquefied petroleum
gas
Sulfur dioxide
Hydrogen sulfide
Phosphorus
(yellow or white)
Sulfur dioxide
Contribution
to impact
score
91%
61%
64%
49%
36%
47%
43%
72%
96%
97%
62%
78%
83%
94%
26%
83%
Table ES-10. Summary of top contributors to LCD impacts by impact category
Impact category
Renewable resource
use
Nonrenewable resource
use
Energy use
Solid waste landfill use
Hazardous waste
landfill use
Radioactive waste
landfill use
Top contributors
Life-cycle stage
Manufacturing
Materials
processing
Use
Use
End-of-life
Use
Process group
LCD monitor/module mfg.
Natural gas production
LCD monitor use
U.S. electric grid
LCD landfilling
U.S. electric grid
Material
Water
Natural gas
(in ground)
Electricity
Coal waste
EOL LCD
monitor,
landfilled
Low-level
radioactive waste
Contribution
to impact
score
38%
65%
30%
44%
97%
44%
ES-21
-------
EXECUTIVE SUMMARY
Table ES-10. Summary of top contributors to LCD impacts by impact category
Impact category
Global warming
Ozone depletion
Photochemical smog
Acidification
Air particulates
Water eutrophication
Water quality, BOD
Water quality, TSS
Radioactivity
Chronic health effects,
occupational
Chronic health effects,
public
Aesthetics (odor)
Aquatic toxicity
Terrestrial toxicity
Top contributors
Life-cycle stage
Manufacturing
Manufacturing
Materials
processing
Use
Materials
processing
Manufacturing
Manufacturing
Manufacturing
Materials
processing
Manufacturing
Use
Manufacturing
Manufacturing
Use
Process group
LCD monitor/module mfg.
LCD panel components
manufacturing
Natural gas production
U.S. electric grid
Steel production, cold-
rolled, semi-finished
LCD monitor/module mfg.
LCD monitor/module mfg.
LPG production
Steel production, cold-
rolled, semi-finished
LCD monitor/module mfg.
U.S. electric grid
LPG production
LCD monitor/module mfg.
U.S. electric grid
Material
Sulfur
hexafluoride
HCFC-225cb
Nonmethane
hydrocarbons,
unspeciated
Sulfur dioxide
PM
Nitrogen
BOD
Suspended solids
Plutonium-241
(isotope)
Liquefied natural
gas
Sulfur dioxide
Hydrogen sulfide
Phosphorus
(yellow or white)
Sulfur dioxide
Contribution
to impact
score
29%
34%
45%
31%
45%
67%
61%
66%
96%
58%
68%
94%
98%
68%
Sensitivity Analyses
Due to assumptions and uncertainties in this LCA, as in any LCA, the following
sensitivity analyses of the baseline results were conducted: use stage manufactured life scenario,
modified glass energy assumptions, modified LCD module manufacturing energy assumptions,
and modified LCD EOL distribution assumptions. The sensitivity analyses were chosen because
they evaluated data with either the greatest uncertainties or with large uncertainty and major
contributors to the inventory results. Table ES-11 shows the different sensitivity analyses or
scenarios that are considered in the impact assessment results.
ES-22
-------
EXECUTIVE SUMMARY
Table ES-11. List of sensitivity analysis scenarios
Monitor
type
Sensitivity analysis scenario
Baseline analyses (for reference)
CRT
LCD
Effective life scenario with average glass energv inputs (all glass manufacturing energv data used)
Effective life scenario with average glass energv inputs (all glass manufacturing energv data used)
and outliers in the LCD module manufacturing energy data removed
Sensitivity analyses
CRT
LCD
CRT
LCD
LCD
LCD
Manufactured life scenario same as baseline except lifespan is based on manufactured life instead of
effective life, which results in some revised functional equivalency calculations
Manufactured life scenario same as baseline except lifespan is based on manufactured life, which
results in some revised functional equivalency calculations
Modified slass energy scenario same as baseline except comparativelv high glass manufacturing
energy inputs are removed
Modified glass energy scenario same as baseline except comparatively high glass manufacturing
energy inputs are removed
Modified LCD module energy scenario same as baseline except LCD monitor/ module manufacturing
energy outliers are included in the average
Modified LCD EOL scenario same as baseline except LCD EOL dispositions are modified
Based on the sensitivity analyses, it appears that CRT life-cycle impacts are highly
sensitive to the glass energy data, and less sensitive to the lifespan assumptions (lifespan
assumptions greatly affect the magnitude of CRT life-cycle impacts, but they do not greatly affect
the distribution of impacts among life-cycle stages). LCD impacts are less sensitive to the glass
energy data and in fact are not greatly affected by any of the sensitivity analysis scenarios, except
the longer lifespan under the manufactured life scenario.
Sensitivity results are also useful to interested members of the public who may be
evaluating the relative impacts of different monitor types and are interested in whether the CRT
or LCD has greater life-cycle impacts in any given impact category. Table ES-12 presents the
monitor type with greatest impacts by impact category and by scenario. This information helps
us determine whether major assumptions (e.g., the monitor lifespan and LCD EOL distribution
assumptions) or uncertain data (e.g., glass energy data and LCD monitor manufacturing energy)
are driving results. As shown in the table, the modified glass energy scenario is the only scenario
that significantly changes from the baseline. Under this scenario, life-cycle impact results in
seven categories reverse direction from the baseline assessment, such that the LCD has greater
impacts than the CRT. Therefore, under this scenario, a total of nine out of 20 categories are
greater for the LCD than the CRT, compared to two out of 20 categories under the baseline
scenario. The only other scenario that affects these results is the manufactured life scenario,
when impacts in the water eutrophication category are greater for the CRT than the LCD.
ES-23
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EXECUTIVE SUMMARY
Table ES-12. Summary of CRT and LCD LCIA results
Impact category
Renewable resource use
Nonrenewable resource use
Energy use
Solid waste landfill use
Hazardous waste landfill use
Radioactive waste landfill use
Global warming
Ozone depletion
Photochemical smog
Acidification
Air particulates
Water eutrophication
Water quality, BOD
Water quality, TSS
Radioactivity
Chronic health effects, occupational
Chronic health effects, public
Aesthetics (odor)
Aquatic toxicity
Terrestrial toxicity
Monitor type with greatest impacts by scenario
Baseline
CRT
CRT
CRT
CRT
CRT
CRT
CRT
b
CRT
CRT
CRT
LCD
CRT
CRT
CRT
CRT
CRT
CRT
LCD
CRT
Manu-
factured
life
CRT
CRT
CRT
CRT
CRT
CRT
CRT
b
CRT
CRT
CRT
CRT
CRT
CRT
CRT
CRT
CRT
CRT
LCD
CRT
Modified
glass energy
CRT
LCD
CRT
CRT
CRT
CRT
LCD
b
LCD
CRT
CRT
LCD
LCD
LCD
CRT
LCD
CRT
LCD
LCD
CRT
Modified
LCD module
energy
CRT
CRT
CRT
CRT
CRT
CRT
CRT
b
CRT
CRT
CRT
LCD
CRT
CRT
CRT
CRT
CRT
CRT
LCD
CRT
Modified
LCD EOL
distribution"
CRT
CRT
CRT
CRT
CRT
CRT
CRT
b
CRT
CRT
CRT
LCD
CRT
CRT
CRT
CRT
CRT
CRT
LCD
CRT
a Based on a qualitative evaluation, not quantitative results.
b CRT impacts are greater than LCD impacts in this category when all data are included in the inventories, including
data for substances that have been phased out. However, LCD impacts are greater than CRT impacts when phased
out substances are removed from the inventories (see Section 3.3.6).
IV. QUALITATIVE RISK SCREENING OF SELECTED CHEMICALS
The scope of the DfE CDP included a streamlined Cleaner Technologies Substitutes
Assessment (CTSA) component to perform a qualitative risk screening of specific materials or
processes. Traditionally, the DfE Program has conducted CTSAs that perform detailed risk
characterizations of alternative chemical processes. The streamlined CTSA for the CDP takes a
more detailed look than the LCA at the toxic effects of chemicals used in a process, without
conducting a complete risk characterization typical of past CTSAs.
Within the human and environmental health effects impact categories of the LCIA, the
input and output amounts are used as surrogates for exposure. The additional CTSA-related
analyses are intended to better understand the potential exposures to those materials, during any
processes that use those materials, in order to try to better understand potential chemical risks.
Lead, mercury, and liquid crystals were selected by the CDP Core Group for further
analysis. These materials were selected for their known or suspected toxicity to humans and the
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EXECUTIVE SUMMARY
environment, or because they are of particular interest to industry or the U.S. EPA. The analysis
of each material summarized or evaluated the following key areas:
• Use of the materials in computer displays;
• Life-cycle inputs and outputs of the materials from computer displays;
• Life-cycle impacts associated with the material inputs and outputs;
• Potential exposures to the material including occupational, public, and ecological
exposures;
• Potential human health effects;
• U.S. environmental regulations for the material; and
• Alternatives to reduce the use of the material in computer displays.
The following are the conclusions drawn from the analyses of lead, mercury, and liquid crystal
use in the life cycle of both CRTs and LCDs.
Lead
Lead is found in glass components of CRTs, as well as in electronics components (printed
wiring boards and their components) of both CRTs and LCDs. It is also a top priority toxic
material at the U.S. EPA and the subject of electronics industry efforts to reduce or eliminate its
use. The following conclusions were drawn from a focused look at lead's role in the life cycle of
the computer display, and its effects on human health and the environment:
• Due to the much greater quantity of lead in the CRT than the LCD, lead-based life-cycle
impacts from the CRT ranged from moderately to significantly greater than those from
the LCD in every category, with the exception of solid waste landfill use. The most
significant difference was in non-renewable resource consumption, where the CRT
consumed over 40 thousand times the mass of non-renewable resources attributable to
lead over the course of its life cycle than those consumed by the LCD. Other categories
where CRTs had notably greater differences in impacts occurred in hazardous waste
landfill use, chronic public health effects, and terrestrial toxicity.
• Contributions of lead-based impacts are small relative to the total life-cycle impacts from
other materials in the CRT (e.g., glass, copper wire), with the greatest impacts from lead-
based CRT outputs occurring in the categories of non-renewable resources, aquatic
toxicity, and chronic public health effects (ranging from 0.1 to 0.2% of the overall impact
scores in each category).
• For workers, inhalation is the most likely route of exposure to lead which may result in
health concerns. General population exposure to lead is most likely to come from
incidental ingestion of lead in the soil, or ingestion of lead brought into the household on
workers clothing or on shoes. Studies have discovered potentially high concentrations of
lead in households within close proximity to certain facilities that use lead.
• Significant worker exposures to lead have been documented by existing studies of several
processes which contribute to the life-cycle of the computer displays (e.g., lead smelting).
These exposures have been as high as 90 times the OSHA recommended safety levels for
exposure to workers at lead smelters. The resulting occupational chronic health effects to
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EXECUTIVE SUMMARY
workers from lead exposure likely have been underestimated by the CDP LCIA
methodology, which uses material inputs, and not outputs, as surrogates for exposure.
• Lead and lead compounds pose serious chronic health hazards to humans who may
become over-exposed either in the workplace, or through the ambient environment. Lead
exposure is associated with a range of adverse human health effects, including effects on
the nervous system, reproductive and developmental problems, and cancer. Lead persists
in the environment, but is relatively immobile in water under most surface and
groundwater conditions.
• Alternatives are being developed, such as lead-free solders and glass components, that
will potentially minimize the future lead content in both CRTs and LCDs.
Mercury
Mercury is contained within the fluorescent tubes that provide the source of light in the
LCD. Mercury is also emitted from some fuel combustion processes, such as coal-fired
electricity generation processes, which contribute to the life-cycle impacts of both CRTs and
LCDs. EPA's concern with mercury and the potential for exposure during manufacturing and
end-of-life processes warranted a more detailed analysis of mercury in the CDP. The following
conclusions were drawn from a focused look at mercury's role in the life cycle of the computer
display, and its effects on human health and the environment:
• The mercury emitted from the generation of power consumed by the CRT (7.75 mg)
exceeds the entire amount of mercury emissions from the LCD, including both the
mercury used in LCD backlights (3.99 mg) and the mercury emissions from electricity
generation (3.22 mg). Although this was not expected because mercury is used
intentionally in an LCD, but not in a CRT, the results are not surprising since mercury
emissions from coal-fired power plants are known to be one of the largest anthropogenic
sources of mercury in the United States. Because the CRT consumes significantly more
electricity in the use stage than the LCD, its use stage emissions of mercury are
proportionately higher than those of the LCD.
• Contributions from mercury-based impacts are not significant relative to the total life-
cycle impacts from other materials (e.g., glass, copper wire) in the CRT or LCD, with the
greatest impacts from mercury-based outputs occurring in the aquatic toxicity category
(0.4% for CRTs, 0.01% for LCDs).
• Possible pathways of worker exposure during backlight fabrication include inhalation of
mercury vapors, and dermal exposure or ingestion of mercury on skin. The most likely
pathway for general population exposure is inhalation of mercury released into the air.
• Exposure data relevant to the manufacturing of mercury backlights were not available,
therefore specific conclusions about the potential magnitude of worker exposures could
not be made. Occupational chronic health effects to workers from mercury exposures
calculated during the impact assessment (3.99e-06 tox-kg for LCD, none for CRT) likely
have been underestimated by the CDP LCIA methodology, which uses material inputs as
surrogates for exposure.
• Mercury and mercury compounds pose serious chronic health hazards to humans who are
exposed. EPA has determined that mercury chloride and methyl mercury are possible
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EXECUTIVE SUMMARY
human carcinogens. Mercury poses serious chronic health hazards to humans, affecting
the nervous system, brain, and kidneys.
• Alternative backlights have been developed that not only eliminate mercury from the
light, but also improve on many of the optical characteristics of the displays. Current
development is focused on improving the energy efficiency of the alternative lights.
Liquid Crystals
Liquid crystals (LCs) are organic compounds responsible for generating the image in an
LCD. LCs are not present in CRTs. The toxicity of the LCs in LCDs has been alluded to in the
literature, yet there is very little known about the toxicity of these materials. By including LCs in
a more detailed analysis, this section attempted to better characterize any potential hazard and/or
potential exposure of LCs from the manufacturing, use, and disposal of LCD monitors. The
following conclusions were drawn from a focused look at LC's role in the life cycle of the
computer display, and its effects on human health and the environment.
• LCs are combined into mixtures of as many as 20 or more compounds selected from
hundreds of potential liquid crystal compounds. Because of the possible variations in
mixtures and the sheer number of compounds available, a select number of liquid crystals
were used to assess potential human health hazards.
• LCs do not appear to contribute significantly to any of the impact categories defined for
this study. The total score for LCD occupational impacts based on potential worker
exposure to LCs of 4.18 tox-grams, calculated using default toxicity values, represents
less than 0.01% of the total overall chronic occupational health effects impact score of
898 tox-kg for the functional unit of one LCD.
• Impacts were not calculated for LC releases in the CDP LCIA because data regarding LC
outputs were not available to the project. LCs are not used to fabricate CRTs and so
have no environmental impacts in the CRT life cycle.
• Occupational exposures to LCs during the fabrication of the LCD panels are not expected
to be significant. The enclosed nature of the chamber in which the LCDs are assembled,
combined with the equipment (e.g., gloves, aprons) worn by workers in a clean room
environment, are both expected to act to minimize exposures. Other occupational
exposures may exist that have not been identified.
• Toxicological testing by a manufacturer of LC substances and mixtures showed that
95.6% (562 of 588) of the liquid crystals tested displayed no acute toxic potential to
humans. Twenty-five of the remaining twenty-six chemicals had the potential to exhibit
harmful effects to humans, while the remaining crystal was classified as toxic (EU
classification) and thus was discontinued. An EPA review of toxicity data for the
confidential LC compounds was unable to identify any relevant toxicity information.
Insufficient toxicity data exist to assess the toxicity of specific LC compounds.
• Testing for mutagenic and carcinogenic effects by the supplier showed that 99.9% (614
out of 615) of the liquid crystal compounds tested displayed no mutagenic effects. The
remaining chemical that showed mutagenic potential was excluded from further
development. Additionally, mutagenicity testing often LC substances using mammalian
cells showed no suspicion of mutagenic potential.
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EXECUTIVE SUMMARY
V. SUMMARY AND CONCLUSIONS
The purpose of the CDP, as stated in Chapter 1, is to provide a scientific baseline of life-
cycle environmental impacts of CRTs and LCDs, and to develop a life-cycle model for future
analyses. The primary targeted audience is the electronics industry, for whom results may
provide insight into improvement opportunities in the life cycle of CRTs and/or LCDs. In
addition, the general public may also find results useful when considering environmental impacts
of each display type. This report, however, does not include direct comparative assertions or
improvement assessments based on the results. Alternatively, results and conclusions are
described in terms of the overall LCI versus the LCIA, and details of the impact assessment,
including the additional assessments of lead, mercury and liquid crystals, and the sensitivity
analyses. Major uncertainties, cost and performance considerations, suggestions for
improvement opportunities, and suggestions for further research are also provided.
LCI vs. LCIA
Inventory data provide information on how much material is being consumed in the life
cycle (i.e., inputs) and how much material is generated/released (i.e., outputs). The LCI alone,
however, does not always translate directly into impact categories that may be of interest.
Impacts are sometimes driven by materials other than the top inventory contributors. For
example, the top air emission for LCDs is carbon dioxide, however the greatest global warming
impact score is from SF6 in the LCD monitor/module manufacturing process.
Some impact categories associated with ancillary materials and water pollutant inventory
types had different outcomes in the LCI versus the LCIA. For example, the three impact
categories affected by the ancillary materials inventory had greater impacts for the CRT (Table
ES-8), although the ancillary material inventory had greater amounts of inputs for the LCD (see
Tables ES-5 and ES-6). In this case, both primary and ancillary materials contribute to the
impact categories, contributing to the differing results.
In addition, the LCD had greater inventory amounts of wastewater outputs than the CRT;
however, the impacts related to water releases are in some cases greater for the CRT than the
LCD. In the LCIA, the LCD has greater impacts for water eutrophication and aquatic toxicity,
but not for the two water quality categories (BOD and TSS), chronic health effects to the public,
nor terrestrial toxicity, all of which include water emissions in calculating the impact score.
These results show that the inventory results may not directly translate into impact results.
CRT and LCD Baseline LCIA Results
The LCIA results showed that the CRT has greater total life-cycle impact indicators than
the LCD in most of the impact categories (see Table ES-8). In the baseline scenario, the CRT
has greater impacts than the LCD in all but two impact categories (eutrophication and aquatic
toxicity). However, note that for the ozone depletion category, the LCIs for both the CRT and
LCD contain data for substances that were phased out of production by 1996 due to their ozone
depletion potential. Whether these emissions still occur in countries that were signatories to the
Montreal Protocol and its Amendments and Adjustments (such as the United States and Japan) is
not known, but considered to be unlikely. When phased-out substances are included in the
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EXECUTIVE SUMMARY
inventory, the CRT has greater ozone depletion impacts than the LCD. However, if phased-out
substances are removed from the inventories, the results are switched, with the LCD having
greater impacts.
When considering which life-cycle stage has greater impacts, the LCIA results showed
that the manufacturing life-cycle stage dominates impacts for most impact categories for both the
CRT and LCD. Table ES-13 lists the number of impact categories with the greatest impacts by
life-cycle stage.
A more detailed evaluation of lead, mercury and liquid crystals was completed in
Chapter 4. As expected, the CRT, which has lead in the glass, frit, and printed wiring boards
(PWBs), had greater impacts from lead than did the LCD, which only has lead in the PWBs.
Regarding mercury, there were greater inventories of mercury in the CRT life cycle than in the
LCD life cycle, despite the fact that only the LCD has mercury directly in the product. The
greater amount of mercury in the CRT life cycle is from the release of mercury and mercury
compounds from the generation of electricity. The CRT consumes significantly more electricity
in the use stage than the LCD. Liquid crystals are only found in LCDs, and therefore, there are
no associated impacts for the CRT. Little conclusive information was available on the liquid
crystal materials. A detailed literature search was conducted, however very little data were
available on the toxicity of these materials. Based on the limited toxicity data obtained, liquid
crystals currently do not appear to be a significant human health or environmental hazard in the
LCD life cycle. However, there were insufficient toxicity data available to make a definitive
conclusion about LC toxicity.
Table ES-13. Number of impact categories in each life-cycle stage with greatest impacts
among life-cycle stages (baseline scenario)
Monitor type
CRT
LCD
# of impact categories with greatest impacts among life-cycle stages
Upstream
3
3
Manufacturing
9
11
Use
6
4
EOL
2
2
CRT Results
For the CRT, many of the impacts were driven by a single material in the inventory. As
shown in Table ES-9, in 14 of the 20 impact categories, the top individual contributor to the
impacts was responsible for greater than 50 percent of the impacts. This shows that the CRT
data are highly sensitive to a few data points. Major conclusions from the CRT LCIA are as
follows:
• Energy used in glass manufacturing and associated production of LPG are driving the
baseline CRT results (they dominate ten impact categories, including overall life-cycle
energy use).
• The large amounts of fuel used as energy sources are driving occupational health effects.
Occupational impacts are calculated from inventory input amounts, and therefore there
may or may not actually be exposure to these fuels (e.g., they may be contained);
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EXECUTIVE SUMMARY
however, the results illustrate the potential for health effects, especially under spill or
upset conditions.
• The generation of electricity for the use stage dominates seven impact categories.
• Air emissions of sulfur dioxide from electricity generation (for the use life-cycle stage)
drive chronic public health effects, acidification, and terrestrial toxicity impacts. This
may be a concern, for example, in areas in nonattainment of regulated levels of sulfur
dioxide in the United States.
The use of LPG fuel in glass manufacturing dominated ten impact categories: two
directly from the LPG used in glass/frit manufacturing (energy use impacts and chronic
occupational health effects) and eight from LPG production (renewable resource use,
nonrenewable resource use, photochemical smog, air particulates, water eutrophication, BOD
water quality, TSS water quality, and aesthetics). In addition, impacts from the generation of
electricity during the use stage dominated seven impact categories: solid waste landfill use,
radioactive waste landfill use, global warming, ozone depletion, acidification, chronic public
health, and terrestrial toxicity. The CRT tube manufacturing process, which represents the most
functionally and physically (by mass) significant component of the CRT monitor, only dominated
one impact category (aquatic toxicity). Twenty-six percent of the aquatic toxicity score was from
phosphorus outputs from tube manufacturing, while most of the rest were from the materials
processing life-cycle stage. The remaining two impact categories (hazardous waste landfill use
and radioactivity) had greatest impacts from the landfilling of the assumed hazardous proportion
of CRT monitors, and the release of Plutonium-241 in steel production, respectively (Table
ES-9). The radioactivity impacts are driven by the radionuclide Pu-241, due to the electric grid
inventory included in the steel production secondary data set, which includes nuclear fuel
reprocessing.
The large amount of LPG reported for glass manufacturing was originally questioned
during the data collection and verification stage of this project. While no compelling reason
could justify removing the LPG data in the baseline case, a sensitivity analysis was conducted in
which the glass energy data were modified. Other sensitivity analyses were also conducted (i.e.,
manufactured life, modified LCD monitor manufacturing energy, and modified LCD EOL
distributions). However, the only scenario that substantially altered results was the modified
glass energy scenario (see Table ES-12). It is likely that the actual energy inputs to the glass
manufacturing process is somewhere between the baseline and modified glass scenarios. More
information is needed on energy used in glass manufacturing, which is driving CRT baseline
results.
The additional analyses for the CRT of lead and mercury also revealed that the use of lead
could present health risks, but the CDP method for calculating occupational impacts uses only
process inputs (not outputs) and may not adequately represent occupational exposures and risks.
Further refinement of the occupational impact analysis may be warranted.
Although there is no mercury in the CRT monitor, mercury emissions from electricity
generation in the CRT life cycle were greater (in mass) than the mercury used in the LCD.
Therefore, to reduce mercury emissions from the CRT life cycle, efforts to reduce electricity
consumption could be taken. Additionally, changes to the electric grid could also reduce
mercury emissions from the CRT life-cycle.
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EXECUTIVE SUMMARY
LCD Results
The LCD impact results were less sensitive to an individual input or output than the CRT
results, although in 11 of the 20 impact categories an individual input was still responsible for
greater than 50% of the total impacts. In general, the LCD results are less uncertain than the
CRT results. This is because most of the CRT results are being driven by either glass input data
or data from secondary sources, while LCD impacts are being driven more by data from primary
sources. Some results to note are as follows:
• The LCD monitor/module manufacturing process group had greatest impacts in six
impact categories (Table 3-58).
• Although the top contributor to the energy impact category was electricity consumed in
the use stage (30%), the overall energy impacts were greater from the manufacturing
stage than the use stage.
• In the glass energy sensitivity scenario, the use stage had greatest energy impacts,
although only by a small margin over the manufacturing stage (see Figure 3-26).
• Sulfur dioxide [emitted from electricity generation in the use stage, and constituting only
0.37% of the air emission inventory (see Table 2-49)] dominates the acidification, chronic
public health, and terrestrial toxicity impact categories (Table 3-58). The high public
health and terrestrial toxicity scores are due to its low non-cancer toxicity value and
resulting high hazard value (HV).
• Sulfur hexafluoride (SF6) from LCD monitor/module manufacturing was the single
greatest contributor to the global warming impact score; however, carbon dioxide from
the use stage and the materials processing stage also contributed significantly to the
global warming impacts (Table 3-25).
• The glass energy inputs did not directly dominate any impact categories, as they did for
the CRT (due to the smaller mass of glass in the LCD); however, LPG production
(required for the glass energy fuel) dominated two categories: TSS water quality and
aesthetics (Table 3-58).
• LNG as an ancillary inventory material was questionably very large and had greatest
impacts in two categories: nonrenewable resource use and photochemical smog (Table 3-
58; shown there as "Natural Gas Production" due to that process being used as a surrogate
for LNG production).
The additional analyses of lead, mercury, and liquid crystals showed that the LCIA alone
is not adequate enough to determine all the potential impacts within the life-cycle of the LCD
monitors. Further, the LCIA method in this LCA used only process inputs as surrogates for
occupational exposure. If the occupational impacts methodology were refined, outputs into the
occupational environment should also be considered.
For mercury, which is found in the backlights of the LCD monitors, there is nearly the
same amount of mercury by mass emitted to the air during electricity generation as there is
mercury used to make the backlight unit. The mass of mercury input for backlights is only about
20% greater than the mercury air emissions from electricity generation (across all life-cycle
stages).
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EXECUTIVE SUMMARY
Liquid crystals were also identified by the CDP Core Group as a material for which
additional information would be reviewed. The LCIA did not find the liquid crystals to be
significant contributors to any impact categories; however, this could partially be due to the lack
of information on them. The additional analysis revealed limited information; however,
qualitatively, it did not show significant potential risk.
CRT vs. LCD Sensitivity Analysis Results
The only sensitivity analysis to show significant difference in the results was the modified
glass energy scenario. In comparing the CRT and LCD, the CRT baseline scenario had greater
impacts than the LCD in all but two impact categories (eutrophication and aquatic toxicity) and
possibly three (ozone depletion). In the modified glass energy scenario, nine of the 20 categories
had greater impacts from the LCD life-cycle than the CRT. Energy use remained greater for the
CRT; however, nonrenewable resource use, global warming, photochemical smog,
eutrophication, BOD and TSS water quality, chronic occupational health effects, and aesthetics
all reversed such that the LCD had greater impacts than the CRT (Table ES-12). As stated
above, it is believed that a more true representation of the monitor life cycles lies somewhere
between the baseline and modified glass energy scenario. Further work is recommended in
clarifying and refining glass energy input information.
Uncertainties
As with any LCA, it is not uncommon for there to be uncertainty associated with such a
large data collection effort. The limitations and uncertainties associated with this LCA and
LCAs in general have been discussed elsewhere in the executive summary. Two of the largest
sources of uncertainty in this LCA that have a significant effect on the results are as follows:
• CRT and LCD glass manufacturing energy inputs (from primary data): The larger
amount of glass used in CRTs than LCDs results in the CRT having greater associated
uncertainty than the LCD results.
• Secondary data for upstream and fuel production processes: When any one material is
used in the life-cycle of either monitor in large quantities, the impacts associated with the
inputs and outputs from the production of that material may become significant. For
example, LPG and LNG production were both used in significant enough amounts to
influence some impact categories. Therefore, the uncertainty in the secondary data
becomes important. This highlights the need for a consistent, national (or international)
LCI database that is updated regularly.
Other uncertainties associated with individual data points had less effect on the overall
results than the uncertainties mentioned above. For manufacturers interested in conducting
improvement assessments, closer review of such uncertainties may be warranted.
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EXECUTIVE SUMMARY
Another point that should be recognized in the overall LCA of CRTs and LCDs is that
CRTs are a more mature technology than LCDs. Changes in LCD manufacturing processes have
likely occurred during the development and publication of this report. Therefore, conclusions
must be carefully drawn when evaluating the mature CRT compared to the newer LCD
technology.
Cost and Performance Considerations
The focus of this study has been on the environmental effects associated with CRTs and
LCDs. The environmental attributes or burdens of a product are not expected to be considered
alone when evaluating the marketability and commercial success of a product. The cost and
performance of each monitor type are obviously critical components to a company's or
consumer's decisions of whether to produce or purchase a product. The report briefly addresses
direct retail costs of the monitors and electricity costs associated with the monitors; however, a
complete cost analysis, including all direct costs (e.g., material costs) and indirect costs (e.g.,
environmental costs to society) is beyond the scope of this report.
The average retail price of 1997-2000 model year monitors, collected from the
manufacturers who supplied data for this project, is $541 for the CRT and $1,450 for the LCD.
From these data, the LCD is approximately 2.7 times more costly. More recent data show that
prices have come down, and the difference in prices between the CRT and LCD has also been
reduced.
The costs from the use stage can be represented by the use stage electricity costs. Based
on the average cost of residential and commercial electricity in the United States, and the amount
of energy consumed per functional unit in the use stage (baseline scenario), the electricity costs
to consumers over the life of the monitors during the use stage are $48 for the CRT and $18 for
the LCD. In addition, the upstream and manufacturing costs of electricity in the baseline
scenario for the CRT are approximately $1.3/functional unit and $1.5/functional unit,
respectively; for the LCD they are $0.10/functional unit and $3.4/functional unit, respectively.
The LCA is defined such that the monitor assessments are performed on a functionally
equivalent basis. To the extent possible, data were collected on functionally equivalent monitors.
When companies were approached to participate in the study, they were informed of the
performance specification parameters within which the study boundaries were defined.
Therefore, it is assumed that they meet the specifications as presented in Table ES-1, and that
they perform relatively equivalently. From the primary data, the reported brightness of the CRT
was less than the LCD, otherwise, they are functionally similar.
Improvement Assessment Opportunities and Targeted Audience Uses of Report
To meet the primary objective of providing the display industry with data to perform
improvement assessments, the industry should look at the manufacturing life-cycle stage, while
recognizing the influences of the other stages. CRT improvement opportunities could include
improved energy efficiency during glass manufacturing and display use, as well as reductions in
lead content. LCD improvement opportunities could also include improved energy efficiency,
especially during manufacturing. Certain materials, such as SF6 and its contribution to global
warming, may also be of concern and an area to focus on in future improvement assessments.
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EXECUTIVE SUMMARY
In addition, any improvement assessment should consider how changes in one life-cycle
stage will affect impacts in other stages. For example, in Chapter 4 we saw that the mercury
inputs and outputs from the intentional use of mercury in an LCD backlight are less (by mass)
than the mercury emissions from the CRT use stage, due to the relative energy usage by the CRT
and the emissions of mercury from electricity generation. In this example, we can see that on a
pure mass basis, a product's energy efficiency is a key consideration and any changes in
manufacturing should consider if it will affect changes in use.
Another objective of this study was to provide an LCA model for future analyses.
Companies or individuals who have more current data for the CRT or LCD can apply them to the
model presented here. For example, changes in an individual process can be identified and
incorporated into the model. The other processes that are not expected to change significantly
can be left unchanged, and only limited data would need to be altered. This would reduce the
time and resources that would normally be required for a complete analysis.
Finally, those interested in comparing the results of the two monitors can apply their own
set of importance weights to each impact category to determine their individual decision. For
example, if energy impacts are much more important than aesthetics to a particular person, they
can weigh energy more heavily in concluding which monitor may have fewer environmental
impacts, while keeping in mind the data limitations and uncertainties, as well as cost and
performance considerations.
Suggestions for Future Research
Areas where future research could be conducted to refine and/or continue the use of the
results in this study are as follows:
• gather more information on energy use in glass manufacturing;
• develop consistent materials and fuel processing data in a national (or international) LCI
database that is updated regularly;
• refine and/or update some of the LCD manufacturing data (e.g., LNG data);
• collect more complete EOL data (e.g., remanufacturing data, and primary data for
incineration and landfilling) to determine better representation of the EOL impacts;
• conduct more research on the EOL options for LCDs;
• collect more detailed data on landfilling and other treatment processes, such as water
treatment where no impacts were calculated;
• update manufacturing data to meet more recent monitor model years;
• conduct a more focused analysis on selected areas for detailed improvement assessments;
and
• evaluate process changes or other alternatives against an "average 1997-2000 model year"
to evaluate impacts of changes or improvements over time.
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REFERENCES
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TORNRC (The Oak Ridge National Recycle Center). 2001. Personal communication with D.
McFarland and A. Bradley, TORNRC, and R. Dhingra, University of Tennessee, Center
for Clean Products and Clean Technologies. April.
Vorhees, G. 2000. Personal communication with G. Vorhees, Envirocycle, and M. L. Socolof,
University of Tennessee, Center for Clean Products and Clean Technologies. July.
ES-36
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1.1 BACKGROUND
Chapter 1
GOAL DEFINITION AND SCOPE
1.1 BACKGROUND
This report presents the results of a voluntary, cooperative project among the Design for
the Environment (DfE) Program in the U.S. Environmental Protection Agency's (EPA) Office of
Pollution Prevention and Toxics, the University of Tennessee (UT) Center for Clean Products
and Clean Technologies, the electronics industry, and other interested parties to develop a model
and assess the life-cycle environmental impacts of flat panel display (FPD) and cathode ray tube
(CRT) technologies that can be used for desktop computers. The DfE Computer Display Project
(CDP) analysis provides a baseline report and the opportunity to use the model as a stepping
stone for further analyses and improvement assessments for these technologies.
EPA's Office of Pollution Prevention and Toxics established the DfE Program in 1992 to
encourage businesses to incorporate environmental concerns into their business decisions. DfE
industry projects are cooperative, joint efforts with trade associations, businesses, public-interest
groups, and academia to assist businesses in specific industries to identify and evaluate more
environmentally sound products, processes, and technologies. The DfE CDP partnership consists
of members of electronic industry trade associations, computer monitor and component
manufacturers, suppliers to the electronics industry, academic institutions, EPA, and a public
interest group. The direction and focus of this project was chosen by the project partners.
The DfE CDP uses life-cycle assessment (LCA) as an environmental evaluation tool,
which is increasingly being used by industry. LCA can be used to evaluate the environmental
effects of a product, process, or activity. An LCA looks at the full life cycle of the product from
materials acquisition to manufacturing, use, and final disposition. It is a comprehensive method
for evaluating the full environmental consequences of a product system. There are four major
components of an LCA study: goal definition and scoping, life-cycle inventory, impact
assessment, and improvement assessment. LCAs are generally global and non-site specific.
Under the DfE Program, the Cleaner Technologies Substitutes Assessment (CTSA)
methodology (Kincaid et al, 1996) was developed to generate information needed by businesses
to make environmentally informed choices and to design for the environment. The CTSA
process involves comparative evaluations of substitute technologies, processes, products, or
materials. Impact areas that are evaluated include human and ecological risk, energy and natural
resource use, performance, and cost.
Both evaluation tools have similar objectives; however, their applications generally
differ. A CTSA is more site specific and evaluates actual (predicted) impacts. For example,
techniques such as health risk assessment are incorporated into a CTSA. An LCA is more global
and generic in nature and generally would not incorporate site-specific parameters when
evaluating impacts. The LCA may also use surrogate measures to represent impacts instead of
predicting or measuring actual impacts.
This project focuses on the LCA, while including some CTSA-related analyses. It
performs the broad analysis of the LCA, which also incorporates many of the CTSA components
(e.g., risk, energy impacts, natural resource use) into the impact assessment. The analysis also
l-l
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1.1 BACKGROUND
assesses more specific impacts for selected materials and acknowledges product cost and
performance, typical of a CTSA. Because both methodologies require intensive data gathering
efforts and can be extensive undertakings, the scope must be carefully and clearly defined. As
only selected materials are evaluated for the CTSA, this project could be considered an LCA with
a streamlined CTSA component.
Life-cycle assessment (LCA) is a comprehensive method for evaluating the full
environmental consequences of a product system. Another related assessment strategy is life-
cycle design, which is a systems-oriented approach for designing more ecologically and
economically sustainable product systems. It integrates environmental requirements into the
earliest stages of design so total impacts caused by product systems can be reduced.
Environmental, performance, cost, cultural, and legal requirements are balanced (Curran, 1996).
Environmental impacts and health risks caused by product development are intended to be
reduced. This is very similar to design for environment (DfE) programs where environmental
issues are incorporated into a product system design process. DfE and life-cycle design have
similar objectives, although their origins differ. DfE was developed as an off-shoot of design for
X, where X could be any number of criteria (e.g., manufacturability, testability, reliability,
recyclability). In DfE, Xis environmental protection and sustainability.
The EPA DfE Program, whereof is also environmental protection and sustainability,
promotes risk reduction, pollution prevention, energy efficiency, and other resource conservation
measures through process choices at a facility level. EPA's DfE CTSA process also includes an
analysis of performance and cost. Typically, EPA's DfE Program focuses less on the entire life
cycle and more on evaluating technology or material substitutes to reduce environmental impacts.
This project combines the DfE Program's CTSA process (Kincaid et al, 1996) and the LCA
process, and thus resembles a life-cycle design approach.
LCAs evaluate the environmental impacts from each of the following major life-cycle
stages:
• Raw materials extraction/acquisition;
• Materials processing;
• Product manufacture;
• Product use, maintenance, and repair; and
• Final disposition/end-of-life.
Figure 1-1 briefly describes each of these stages for a computer display product system. The
inputs (e.g., resources and energy) and outputs (e.g., product and waste) within each life-cycle
stage, as well as the interaction between each stage (e.g., transportation) are evaluated to
determine the environmental impacts.
As defined by the Society of Environmental Toxicology and Chemistry (SETAC), the
four major components of an LCA are: (1) goal definition and scoping; (2) inventory analysis;
(3) impact assessment; and (4) improvement assessment. More recently, the international
standard, ISO 14040: Environmental Management—Lifecycle Assessment—Principles and
Framework, has defined the four major components of an LCA as: (1) goal and scope; (2)
inventory analysis; (3) impact assessment; and (4) interpretation of results. The SETAC and
International Standards Organization (ISO) framework are essentially synonymous with respect
to the first three components, but differ somewhat with respect to the fourth component,
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1.1 BACKGROUND
improvement assessment or life cycle interpretation. Improvement assessment is the systematic
evaluation of opportunities for reducing the environmental impacts of a product, process, or
activity. Interpretation is the phase of LCA in which the findings from the inventory analyses
and the impact assessment are combined together, consistent with the defined goal and scope in
order to reach conclusions and recommendations. In this study and project report, the goal and
scope are the subject of Chapter 1. The inventory analysis and impact assessment are the
subjects of Chapters 2 and 3 respectively; and the improvement assessment or life-cycle
interpretation are left to the electronics industry given the results of this study. The life-cycle
inventory and impact assessment strategies are briefly described below.
INPUTS
LIFE-CYCLE STAGES
OUTPUTS
Materials
Energy
Resources
RAW MATERIALS EXTRACTION/ACQUISITION
Activities related to the acquisition of natural resources, including mining
non-renewable material, harvesting biomass, and transporting raw
materials to processing facilities.
MATERIALS PROCESSING
Processing natural resources by reaction, separation, purification, and
alteration steps in preparation for the manufacturing stage; and
transporting processed materials to product manufacturing facilities.
PRODUCT MANUFACTURE
Processing materials and assembling component parts to make a
computer display.
PRODUCT USE, MAINTENANCE, AND REPAIR
Displays are transported to and used by customers. Maintenance and
repair may be conducted either at the customer's location or taken back
to a service center or manufacturing facility.
FINAL DISPOSITION
At the end of its useful life, the display is retired. If reuse and recycle of
usable parts is feasible, the product can be transported to an appropriate
facility and disassembled. Parts and materials that are not recoverable
are then transported to appropriate facilities and treated (if required
or necessary) and/or disposed of.
Wastes
Products
Boundary
Figure 1-1. Life-cycle stages of a computer display
The life-cycle inventory (LCI) involves the quantification of raw material and fuel inputs,
and solid, liquid, and gaseous emissions and effluents. Traditional LCIs quantify pollutant
categories (e.g., volatile organic compounds [VOCs]) rather than particular chemicals. This
project also includes a more detailed evaluation of a few specific chemicals found in computer
displays (lead, mercury, and liquid crystals) to enable a more thorough evaluation of risk from
chemical exposure. The approach to the LCI in this study involves defining product components,
developing a bill of materials (BOM), and collecting inventory data on each life-cycle stage for
computer displays. Details of the LCI data gathering activities are provided in Chapter 2.
1-3
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1.2 INTRODUCTION
The life-cycle impact assessment (LCIA) involves the translation of the environmental
burdens identified in the LCI into environmental impacts. LCIA is typically a semi-quantitative
process involving characterization of burdens and assessment of their effects on human and
ecological health, as well as other effects such as smog formation and global warming. Details of
the LCIA methodology and results are presented in Chapter 3. This project has furthered the
development of LCIA methodology by including health effect concerns into the LCIA. This
study also qualitatively assesses exposure and chemical risk of selected chemicals in the life
cycles of the computer displays (Chapter 4).
1.2 INTRODUCTION
Goal and scope definition is the first phase of LCA and is important to the CTSA as well.
This phase is important because it determines why the LCA or CTSA is being conducted and its
intended use, as well as the system and data categories to be studied.
This chapter presents the goal and scope of the DfE CDP, including its purpose and goals,
previous research and market trends, descriptions of the product systems being evaluated, and the
boundaries used in this study. It incorporates scoping as it is recommended in both the LCA
(e.g., Curran, 1996; Fava et al, 1991; ISO, 1996) and CTSA processes (Kincaid et al, 1996).
1.2.1 Purpose
The purpose of this study is two-fold: (1) to establish a scientific baseline that evaluates
the life-cycle environmental impacts of flat panel displays (FPDs) and cathode ray tubes (CRTs)
for desktop computers, by combining LCA and CTSA methodologies; and (2) to develop a
model that can be used with updated data for future analyses. This study evaluates the newer
active matrix liquid crystal display (LCD) and the more traditional CRT technologies. The
evaluation considers impacts related to material consumption, energy, air resources, water
resources, landfills, human toxicity, and ecological toxicity. This study is designed to provide
the electronics industry with information needed to improve the environmental attributes of
desktop computer displays. It is intended to provide valuable data not previously published, and
an opportunity to use the model developed for this project in future improvement evaluations that
consider life-cycle impacts. It will also provide the industry and consumers with valuable
information to make environmentally informed decisions regarding display technologies, and
enable them to consider the relative environmental merits of a technology along with its
performance and cost.
1.2.2 Previous Research
While there has been some work done on the life-cycle environmental impacts of either
CRTs or LCDs, there has not been a quantitative LCA addressing both CRTs and LCDs. For
example, Microelectronics and Computer Technology Corporation (MCC) published an
Electronics Industry Environmental Roadmap (1994) that qualitatively discussed environmental
issues and priority needs for reducing impacts from computer CRTs and FPDs, but this project
did not, nor was it intended to, focus on all aspects of the displays' life cycles.
1-4
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1.2 INTRODUCTION
Some of the environmental impacts of CRTs (e.g., energy use, disposal of lead, and other
end-of-life issues such as recycling) have been identified but not quantified in previous work,
such as that done by EPA's Common Sense Initiative Computer and Electronics Subcommittee.
Atlantic Consulting completed a draft LCA of the personal computer (including a 15" monitor)
for the European Union's (EU) Eco-Label program (Atlantic Consulting and IPU, 1998).
Further, the New Jersey Institute of Technology conducted an LCA of television CRTs, which
have the same technology as the computer monitor CRT.
Studies on the environmental impacts of FPDs are much less prevalent. A University of
Michigan master's thesis (Koch, 1996) evaluated the environmental performance of an LCD
manufacturer. The thesis did not quantitatively assess environmental impacts from all life-cycle
stages, as would be done in an LCA. The EU Eco-Label Program also evaluated a portable
computer with a 13.3" LCD screen (Orango AB and Atlantic Consulting, 1999). The scope was
limited to energy consumption for the impact assessment, and it provided some inventories for
raw materials production. Human and ecological toxicity were excluded from the scope of the
portable computer analysis.
1.2.3 Market Trends
At present, computer displays using CRTs dominate worldwide markets. They provide a
rich, high-resolution display well suited to a wide range of user requirements. However, CRT
displays are bulky, use larger amounts of energy to operate than LCDs, and are associated with
disposal concerns due to the presence of lead in the glass. Color CRT monitors contain lead to
help shield the users from x-rays (x-ray attenuation) and can, under some circumstances, be
classified as a hazardous waste when disposed of. Newer technologies, collectively referred to as
FPDs, have captured significant market segments. FPDs exhibit desirable qualities such as
reduced size and weight and greater portability. Environmentally, they are expected to consume
less energy during use and do not use leaded glass. However, they may consume more energy
during manufacturing, contain small amounts of mercury, are more costly, and in the past have
had lower resolution and image quality than the CRT. The LCD, first used predominately in
notebook computers, is now moving into the desktop computer market. The 1998 worldwide
market for desktop computer monitors was 90 million units. The 1998 actual and 2001 projected
markets for desktop computer CRTs and LCDs are presented in Table 1-1. Market projections
anticipate that LCDs will capture sizable market share for desktop computer displays.
Table 1-1. Desktop display markets - actual for 1998 and projected for 2001
Technology
CRT
Worldwide
North America
LCD
Worldwide
North America
Number of displays (thousands of units)
1998
88,600
33,801
1,300
229
2001
119,100
42,609
14,300
3,787
Sources: DisplaySearch, 2001.
1-5
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1.2 INTRODUCTION
1.2.4 Need for the Project
Given the expected market growth of LCDs for computer displays, the various
environmental concerns throughout the life cycle of the computer displays, and the fact that the
relative life-cycle environmental impacts of LCDs and CRTs have not been scientifically
established to date, there is a need for a quantitative environmental life-cycle analysis of desktop
computer display technologies. Manufacturers can use these results or the model developed here
to identify areas for improvement concerning the environmental burdens. Further, as companies
or consumers are considering investing in certain displays, they can refer to the results of this
study to assist them in making environmentally informed decisions.
1.2.5 Targeted Audience and Use of the Study
The electronics industry is expected to be one of the primary users of the study results.
The study is intended to provide industry with an analysis that evaluates the life-cycle
environmental impacts of selected computer display technologies. Scientific verification of the
relative environmental impacts will allow industry to consider environmental concerns, along
with traditionally evaluated parameters of cost and performance, and to potentially redirect
efforts towards products and processes that reduce releases of toxic chemicals and reduce risks to
health and the environment. Given the results, the industry can then perform an improvement
assessment of the display technologies. This also allows the electronics industry to make
environmentally informed choices about display technologies when assessing and implementing
improvements such as changes in product, process, and activity design; raw material use;
industrial processing; consumer use; and waste management.
Another result of the study is an accounting of the relative environmental impacts of
various components of the computer displays, thus identifying opportunities for product
improvements to reduce potential adverse environmental impacts and costs. Identification of
impacts from the computer display technologies can also encourage industry to implement
pollution prevention options, such as development and demonstration projects, and technical
assistance and training. Since this study incorporates a more detailed health effects component
than in traditional LCAs, the electronics industry can use the tools and data to evaluate the
health, environmental, and energy implications of the technologies. With this evaluation, the
U.S. electronics industry may be more prepared to meet the demands of extended product
responsibility that are growing in popularity in the global marketplace, and better able to meet
competitive challenges in the world market. In addition, the results and model in this study will
provide a baseline LCA upon which alternative technologies can be evaluated. This will allow
for more expedited display-related LCA studies, which are growing in popularity by industry and
may be demanded by original equipment manufacturers (OEMs) or international organizations.
EPA and interested members of the public can also benefit from the results of the project.
The project has provided a forum for industry and public stakeholders to work cooperatively, and
the results can be used by stakeholders as a scientific reference for the evaluated display
technologies. The results of the project could also be of value to other industries involved in
designing environmental improvements into the life cycle of consumer products.
1-6
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1.3 PRODUCT SYSTEM
1.3 PRODUCT SYSTEM
1.3.1 Functional Unit
The product system being analyzed in this study is a standard desktop computer display
that functions as a graphical interface between computer processing units and users. The desktop
market was chosen to evaluate CRTs and FPDs because it represents a large market for CRTs
and an anticipated large market for some FPDs. Also, there are a limited number of technologies
that meet desktop specifications. Therefore, focusing on the desktop market will affect a
significant number of products, while keeping the scope of this project manageable.
The product system is the computer display itself and does not include the central
processing unit (CPU) of the computer that sends signals to operate the display. It is assumed
that the LCDs operate with an analog interface, and therefore are compatible with current CRT
CPUs as plug-and-play alternatives.
In an LCA, product systems are evaluated on a functionally equivalent basis. The
functional unit is used as the basis for the inventory and impact assessment to provide a reference
to which the inputs and outputs are related. For this project, the functional unit is one desktop
computer display over its lifespan. Data collected in this project have been normalized to a
display that meets the functional unit specifications, which are presented in Table 1-2. These
product performance specifications are assumed to meet the requirements of the system
functional unit in the predictable future (i.e., computer technology as predicted through the year
2001). The CRT technology is the current industry standard for this product system.
Table 1-2. Functional unit specifications
Specification
display size a
diagonal viewing area a
viewing area dimensions
resolution
brightness
contrast ratio
color
Measure
17" (CRT); 15" (LCD)
15.9" (CRT); 15" (LCD)
12.8" x 9.5" (122 in2) (CRT); 12" x 9"
(108 in2) (LCD)
1024x768 color pixels
200 cd/m2
100:1
262,000 colors
a An LCD is manufactured such that its nearest equivalent to the 17" CRT display is the 15" LCD. This is because
the viewing area of a 17" CRT is about 15.9 inches and the viewing area of a 15" LCD is 15 inches. LCDs are not
manufactured to be exactly equivalent to the viewing area of the CRT.
Besides the CRT display, several FPD technologies were considered for inclusion in this
study. Among the FPD technologies that exist, the amorphous silicon (a: Si) thin-film transistor-
(TFT) active matrix LCD technology meets the requirements of the functional unit within the
parameters of this analysis and is assessed in this study. Section 1.3.3.1 describes the LCD
technology further, and Appendix A briefly describes several FPD technologies and explains why
the non-LCD technologies are not considered for standard desktop computer uses as defined for
this study. The following subsections briefly describe both CRT and LCD technologies.
1-7
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1.3 PRODUCT SYSTEM
1.3.2 Cathode Ray Tube
1.3.2.1 CRT technology
CRT monitors are a mature technology and are the current industry standard for desktop
computer displays. The technology is the same as that for a television. CRT displays use high
voltages to accelerate electrons toward a luminescent material (phosphor) that is deposited on a
faceplate. The phosphor converts the kinetic energy of the electrons into light. In color CRTs,
the phosphors are patterned in dots or stripes of red, green, and blue phosphors. The electrons
are emitted from three cathodes in an electron gun assembly and pass through an apertured metal
"shadow mask" during their passage to the phosphor. Electrons from each cathode that are
directed at the wrong color phosphor are absorbed by the shadow mask. Pictures are created by
first focusing the electron beams into tiny spots, which are moved by deflecting the electron
beams electromagnetically with the "yoke." This system is extremely efficient in that it only
requires three video drivers and connections instead of the 2000 or so in the most common FPD
(MCC, 1994).
The high voltages used to accelerate the electrons must be insulated from the external
surfaces of the tube and the CRT must have excellent electrical insulating properties. The
decelerating electrons produce x-rays and the CRT must also be a good x-ray absorber. Leaded
glass surrounds the cathode ray tube to absorb the x-rays.
The major parts of the CRT display are the faceplate (glass panel), shadow mask (also
referred to as the aperture mask), a leaded glass funnel, and the electron gun with the deflection
yoke. Various connectors, wiring, an implosion band, printed wiring boards (PWBs), and the
casing comprise most of the rest of the display. Table 1-3 presents a more comprehensive list of
the CRT components and a list of the component materials identified from disassembling a
monitor, and additional research to identify the material makeup of some components (MCC,
1998).
1-8
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1.3 PRODUCT SYSTEM
Table 1-3. Preliminary list of CRT display components and materials
Tube
Faceplate assembly
Frit (lead solder glass)
Conductively
Implosion band
Component parts
Phosphor-coated faceplate
Internal electron shield *
Shadow mask assembly
Glass funnel
Conductive coating
Frit
Binder
Neck glass
Deflection yoke
Base & top neck, rings
Brass ring, brackets
Rubber gaskets
Screws, washers
Neck clamp
Insulating rings
Neck PWB
Glass panel (faceplate)
Phosphors
Photoresist
Black matrix coating (grille
dag)
Lacquer coating
Aluminum coating
Mask
Supports
— -»
-—>
____K
*•
*•
*•
K
K
K
^_
^
K
K
^
^_
K
K
^
^
K
K
^
^
>
Materials
Glass (1-2.5% PbO alkali/alkaline earth
aluminosilicate)
ZnS, Y2O2S (powders): Sn, Si, K, Cd
Polyvinyl alcohol
Aquadag**
Mixture of alcohol and plastics
Al
Al
Steel, Ni
CrNiFeandNiFe
Lead oxide, zinc borate (-70% PbO)
Leaded glass (-24% PbO)
Aquadag** (may also add iron oxide)
PbO, zinc oxide, boron oxide
Nitrocellulose binder, amyl acetate
Leaded glass (30% PbO alkali/alkaline earth silicate)
Cu, ferrite
Polystyrene
Brass
Rubber
Zn-plated steel
Steel
Polysulphone
Misc. electronics and resin board
Steel
1-9
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1.3 PRODUCT SYSTEM
Table 1-3. Preliminary list of CRT display components and materials
Component parts
Materials
Electron gun
Electrostatic field shaping electrodes
Cathodes
Glass pillars
Wire heater (filament heater)
Glass stem
Springs and washers
Gunmount (glass)
300/400 series steels (Fe, Ni, Cr)
Ni (coated with mixtures of Ba, Sr, CaCOS)
Borosilicate glass
Tungsten, aluminum oxide
Leaded glass (29% PbO alkali aluminosilicate)
Steel
Potassium aluminosilicate sintering
Powerboard
Main CRT PWB (includes power supply PWB, etc.)
Flyback transformer
Misc. electronics and resin board
Misc.: e.g., potting material (epoxy), steel, Cu
Casing
(chassis and base)
Polystyrene
Other misc.
parts
Brackets
Brackets
XY controls
Connectors
Screws
Brackets, anode connection
Shields (right, left, top, back)
Rubber feet
Anode cap
Insulator pad
Brass
Polystyrene
Polycarbonate
Al
Zn-plated steel
Silicone rubber
Rubber
Polyester
1-10
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1.3 PRODUCT SYSTEM
1.3.2.2 CRT manufacturing
The manufacturing process of the CRT (Figure 1-2) involves first preparing the glass
panel and shadow mask. The shadow mask is a steel panel with a mask pattern applied through
photolithography. The color phosphors and a black matrix coating (aquadag) are applied to the
faceplate, also using photolithography, which involves several steps and several chemicals that
etch the material into specific patterns. A lacquer coating is applied to the phosphor-coated glass
to smooth and seal the inside surface of the screen, and an aluminum coating is added to enhance
brightness and as a conductor to allow the use of voltages over 12 kilovolts without charging of
the phosphor screen. An electron shield (typically aluminum) is attached to the shadow mask
assembly to prevent stray electrons from reaching outside the screen area (EPA, 1995; MCC,
1994). This then comprises the faceplate assembly. The two major remaining parts are the
funnel and electron gun.
1-11
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1.3 PRODUCT SYSTEM
repeat 4 times
for different layers
color filter
formation
(photolithography)!
repeat 8 times
H
for different layers
TFT formation
(photolithography) |
(includes electrode
formation)
electrode
formation (ITO)
(photolithography)
apply polyimide
orientation film
(cyrstal alignmnent
layer) - application
and rubbing
1
1
k>
^
apply seal and
cure
k.
insert spacers
k>
inspect
-J
clean cirucit
boards
^
functional test
of glass panel
^
laminate front
and rear
polarizers
^
seal (UVor
oven cured)
^
insert liquid
crystal
^
merge plates
(apply UV cured
adhesive)
atta
colum
driv
i
ch
ers
k
manufacture driver
tabs (1C chips) and
driver input PWBs
test/operate
attach
backlight
assembly
i
k
k-
manufacture 1
backlight 1
assembly 1
(including PWB) 1
attach
controller PWB
1
L
manufacture
controller PWB
^
attach
PWB
t
manufacture
adjustment
PWB
k-
attach power
assembly
t
manufacture
power supply
PWB (and other
assembly parts)
k-
attach
base/stand
assembly
• Shadowed boxes represent processes with additional subprocess steps.
h
Bold outlined boxes represent processes shown in subsequent figures.
Figure 1-2. Traditional twisted nematic AMLCD manufacturing process
1-12
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1.3 PRODUCT SYSTEM
The leaded-glass funnel is washed and coated with a black coating (aquadag), which is a
good electrical conductor and a non-reflective surface. The funnel and faceplate assembly are
joined using frit (solder glass) that is approximately 70% lead oxide. The electron gun is an
assembly of glass and several metal parts that are heated to embed the metal in the glass. The
electron gun is then fused to the funnel neck. Finishing steps are conducted to complete the
manufacturing of the CRT (or "tube") (e.g., attaching a metal implosion band for implosion
protection and safety) and then the entire monitor is assembled with other necessary parts (e.g.,
the main and neck PWBs, power cord, casing).
1.3.3 Liquid Crystal Display
LCDs are used for various applications, with their largest market currently in notebook
computers. LCDs have been gaining a presence in the desktop computer display market and are
expected to continue to do so. Compared to the CRT, the LCD provides a more compact display,
as well as being of higher contrast, sunlight readable, more reliable, and more durable (i.e.,
requiring much less maintenance) (Koch and Keoleian, 1995). In general, the major functional
disadvantages have been that the resolution and quality of the image have not matched that of
CRTs. However, emerging technologies are expected to meet user requirements.
The two most common types of LCDs are passive matrix (PMLCD) and active matrix
(AMLCD). Brief descriptions of these and other LCD technologies are presented in Appendix A,
Table A-l. In 1998, AMLCDs constituted approximately 81% and PMLCDs 19% of computer
monitor LCD production (MCC, 1998). PMLCDs are used primarily for low-end products (e.g.,
cannot perform video applications); AMLCDs are used for high-end multimedia products and
better meet the specifications for standard desktop computers. PMLCDs are forecasted to decline
to less than one percent of the LCD desktop display market by 2002 (Young, 1998). Therefore,
this project's focus is on AMLCDs.
1.3.3.1 LCD technology
In general, an LCD is comprised of two glass plates surrounding a liquid crystal material
that filters external light. LCDs control the color and brightness of each pixel (picture element)
individually, rather than from one source, such as the electron gun in the CRT.
The most common type of AMLCD, and the one that meets the functional unit
specifications of this project, is the a: Si TFT AMLCD (see Appendix A, Table A-l for
descriptions of various types of AMLCDs). AMLCDs consist of driver tabs along the columns
and rows of the display glass and transparent parallel electrical lines across the glass arranged to
form a matrix. Each intersection of the matrix forms a pixel. The TFT AMLCD has a transistor
at each pixel which functions as an electronic switch to activate an individual pixel. This active
addressing technique allows for high contrast between the on and off states of a pixel.
Operation of the AMLCD is determined by how the liquid crystals are aligned when
activated by an electrical current. Traditional AMLCDs use a twisted nematic (TN) operating
principle of the liquid crystal, which is evaluated in this study. The orientation of the liquid
crystal molecules either allows or does not allow light from a backlight source to pass through the
display cell. When no electrical current is present, the liquid crystals align themselves parallel to
a polyimide orientation film (alignment layer) on the glass. When a current is applied, the liquid
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1.3 PRODUCT SYSTEM
crystals turn perpendicular to the glass. The combination of the alignment layer, electrical charge,
and polarizers that are laminated to the glass panels affect an on or off state of the LCD cell (see
Appendix B for further explanation; also see Castellano [1992] and OTA [1995]). The backlight
supplies the light source for the display and generally has four cold cathode fluorescent tubes that
contain small amounts of mercury vapor. Because the LCD technology essentially regulates
passage of a backlight through the display, LCDs are considered non-emitting display
technologies. CRTs, on the other hand, are emitting displays which emit electrons to illuminate
appropriate phosphors.
There is a variation of the a: Si TFT AMLCD technology called in-plane switching (IPS).
Compared to the traditional TN mode, IPS TFT allows for a wider viewing angle that is
comparable to the CRT. The traditional TN mechanism vertically twists the liquid crystals by
sending voltage through the display from electrodes that are on both the front and rear glass
panels. IPS mode twists the liquid crystals horizontally in response to a voltage applied by
electrodes on the rear glass only. The TN TFT uses indium-tin oxide (ITO) as the transparent
electrode on the front and rear glass panels. For the IPS TFT, no ITO is needed on the front glass
and the electrode on the rear glass is made of any of a number of other materials (e.g., Mo, Ta,
Al/Cr, MoW). Therefore, no ITO is used for the IPS mode. However, the IPS TFT display
demands an increase in the number of backlights to meet the brightness requirements for desktop
applications (DisplaySearch, 1998). Although this technology may be produced for displays that
meet this study's functional unit, the manufacturers of 15" AMLCDs that supplied data for this
study provided data only for traditional a:Si TFT AMLCDs. IPS was forecasted to have a 35%
market share of LCD desktop monitors in 2000 (Young, 1998) and therefore, studying IPS
technology may be an area for future research.
Based on the disassembly of an LCD monitor conducted by MCC, a summary of the
materials that are in an AMLCD are presented in Table 1-4 (MCC, 1998). The major components
of the AMLCD are the glass panel (which includes the transistors, electrodes, liquid crystals,
orientation film, polarizers, and row and column drivers), the backlight assembly (including the
cold cathode fluorescent tube, light guide, and associated electronics), other electronics (main
LCD controller), and the stand and cover. The remaining components and materials are listed in
Table 1-4. In this report we will also refer to the LCD "module" as a component. This is
comprised of the LCD panel, backlight unit, and main LCD controller. Module manufacturing as
a process modeled in this study includes the major process in LCD manufacturing, which is panel
manufacturing described below.
1-14
-------
1.3 PRODUCT SYSTEM
Table 1-4. LCD components and materials
LCD component parts
LCD assembly
Controller
(PWB)
Power supply
assembly
LCD glass panel
assembly
Plastic frame
Gaskets
Screws
Metal clip
Brightness enhancer
Cable assembly
AMLCD cell
Row/column driver tabs
Row/column driver PWBs
Connection flex
Glass
Thin film transistor (TFT)
Electrode
Polarizers
Orientation film (alignment layer)
Liquid crystals
Color filters
*•
*•
*•
*•
*•
*•
*•
^_
^
-
Misc. wires & connectors
^
.>
Housing
Screws
Insulator
Power switch
Power cord recepticle
Heat sink
Power supply PWB
K
Materials
Soda lime or borosilicate
Misc. (e.g., Si, Mo, Al, etc) *
Indium-tin oxide (ITO)
Iodine, cellulose triacetate-acrylic,
etc.
Polyimide
e.g., phenylcyclohexanes biphenyls
Resins
1C chip on polyimide
Misc. (Si, Cu, etc.)
Cu on film of polyimide
Polycarbonate, glass filled
Silicone rubber
Steel (Fe)
BeCu
Polyester
Misc. (Cu, plastic, etc.)
Misc. (Si, Cu, etc.)
Steel (Fe)
Polyester
ABS/Cu
Aluminum
Misc. (Si, Cu, etc.)
1-15
-------
1.3 PRODUCT SYSTEM
Table 1-4. LCD components and materials
LCD component parts
Backlight
assembly
Metal plate
Screws
Brass threaded stand off
Gasket
Nylon strain relief
Nylon clamp
Clear protector
Opaque diffuser
White reflector
Light pipe
Corner tape
Light assembly
Rear plate assembly
Backlight PWB
>•
>•
>•
>•
^
^
^
^
^
^
^
Cold cathode tube
Shock cushion
Cable assembly
Rear plate
Screws
Hold-down plate
Cable clamp
Plastic tube
Flat cable toroid
Caution label
^.
>•
>•
>•
>•
^.
^
^
^
>•
>•
Materials
Steel (Fe)
Brass
Foam rubber
Nylon
Plexiglas
Polyester
Polycarbonate
Aluminized mylar
Glass, phosphor, Hg
Silicone rubber
Insulated Cu
Steel (Fe)
Nylon
Polycarbonate
Hi-mu ferric
Paper
Misc. (Si, Cu, etc.)
1-16
-------
1.3 PRODUCT SYSTEM
Table 1-4. LCD components and materials
LCD component parts
Materials
Rear cover
assembly
Screws
Metal plate
BeCu fingers
Cloth mesh
Insulator
Rear cover
BeCu
Polyester
Plastic (ABS)
Base/stand
assembly
Brackets & washers
Axle & spring
Base weight
C-clip
Swivel bearing 1
Swivel bearing 2
Covers
Upright
Bushing
Rubber feet
Steel (Fe)
Stainless steel
Polyoxymethylene (acetal)
Plastic (ABS)
unsaturated polyester, glass filled
Nylon
Silicone rubber
Other misc.
parts
Screws
Power supply cover
Front bezel
Knob
Power switch
LED light pipe
Adjustment PWB
Cable clamp
Insulator
Steel (Fe)
ABS
Polycarbonate
Misc. (Si, Cu, etc.)
Nylon
Polyester
Source: MCC, 1998.
* Example of TFT materials: gate metal (Al or Cr), S;O2, SiN, a-Si/SiNx, a-Si, drain metal
1-17
-------
1.3 PRODUCT SYSTEM
1.3.3.2 LCD manufacturing
LCD technology uses a glass substrate (e.g., soda lime or borosilicate glass). Once the
glass is acquired, it must be cleaned, which is a critical step in reliable manufacturing. The
manufacturing techniques of the LCD are similar to the production of semiconductor chips,
which require energy intensive "clean rooms" for manufacturing. A conductor or semiconductor
is deposited on the glass substrate. Most FPDs require a transparent conductor (electrode) such
as ITO, which is usually deposited by a sputtering method. TFT devices in AMLCDs use
semiconducting materials (e.g., silicon, cadmium selenide) for transistors at each pixel. These
semiconducting materials can be prepared by vacuum evaporation, using either electron beam
evaporation, sputtering, or chemical vapor deposition. Electrode patterns are then formed by a
photolithographic process that begins with the coating of photoresist on the ITO or metal-coated
substrate.
The photoresist (photosensitive organic polymer) is then "developed" using liquid
organic chemicals. This is similar to the manufacture of silicon integrated circuits (ICs). The
ITO or metal is then etched to form electrodes. FPD manufacturing employs etchants (e.g.,
H3PO4/HNO3, HF/HC1, HC1O4, CF4/SF6) that differ from those used in silicon 1C manufacturing.
LCDs use alignment layers and iodine/dye based polarizers. AMLCDs use amorphous silicon,
silicon nitride, various oxides and metals. The silicon 1C manufacturing process of plasma-
enhanced chemical vapor deposition (PECVD) is used for some of these layers, as are more
conventional vacuum deposition techniques. Finally, various organic liquids (the liquid crystals)
are injected between the top and bottom substrate of LCDs (MCC, 1993).
The general process flow of AMLCD manufacturing is presented in Figure 1-3. The
photolithographic subprocess steps for the front and rear glass panels are presented in Figures 1-4
and 1-5. Various processes include sputtering, PECVD, photolithography, wet etching, reactive
ion etching (RIE), in-process testing, liquid crystal processing, and lamination among others.
The manufacturing process of IPS differs from traditional TN in that there are fewer
photolithography steps required since no ITO is patterned onto the front or rear glass plates.
Once the photolithographic processes are completed, the polyamide orientation film is
applied and rubbed on the glass. The front and rear glass substrates are merged and the liquid
crystals are inserted. Polarizers are laminated to the front and rear panels, completing the
"AMLCD cell" of the LCD glass panel assembly (see Table 1-4). The electronic components
that operate the AMLCD cell (i.e., the column and row driver tabs and wiring boards) are then
attached to the glass. This completes the LCD glass panel assembly. The other major
components of the LCD are then assembled. Adding the controller PWB and the backlight
assembly make up what may also be called the "LCD module." Finally, the power supply
assembly and the plastic cover and stand are added to make an assembled monitor.
In total, there are six PWBs needed for the LCD: controller, row driver, column driver,
backlight, power supply, and adjustment knob PWB. The major ones by size and function are
the larger controller and backlight PWBs, and the smaller column and row PWBs. These are
compared to the two major PWBs in the CRT: the main and neck PWBs (see Table 1-3).
1-18
-------
1.3 PRODUCT SYSTEM
repeat 4 times
for different layers
color filter
formation
(photolithography)!
repeat 8 times
H
for different layers
TFT formation
(photolithography) |
(includes electrode
formation)
electrode
formation (ITO)
(photolithography)
apply polyimide
orientation film
(cyrstal alignmnent
layer) - application
and rubbing
1
1
k.
^
apply seal and
cure
^
insert spacers
k.
inspect
^
clean cirucit
boards
^
functional test
of glass panel
^
laminate front
and rear
polarizers
^
seal (UV or
oven cured)
--
insert liquid
crystal
^
merge plates
(apply UV cured
adhesive)
attc
colum
driv
A
ch
ers
L
manufacture driver
tabs (1C chips) and
driver input PWBs
test/operate
attach
assembly
t
manufacture
backlight
assembly
(including PWB)
k-
attach
controller PWB
t
manufacture
controller PWB
k-
attach
adjustment
PWB
i
L
k-
manufacture 1
adjustment 1
PWB I
attach power
supply
assembly
I
k
k-
attach
base/stand
assembly
manufacture 1
power supply 1
PWB (and other 1
assembly parts) 1
• Shadowed boxes represent processes with additional subprocess steps.
• Bold outlined boxes represent processes shown in subsequent figures.
Figure 1-3. Traditional twisted nematic AMLCD manufacturing process
1-19
-------
1.3 PRODUCT SYSTEM
COl
^
— w
.OR FILTER FORMATION
Apply
color filters -
(1 ) black matrix (sputter)
(2) red (spin coat)
(3) green (spin coat)
(4) blue (spin coat)
^
— w
resist coat
(polyimide)
^
for e
^
expose
^
develop
(tetramethyl
ammonium
hydroxide
[TMAH])
^
clean/dry
clean and dry
^
^
wet etch
(1) halogen
plasma/solvent
(2) solvent
(3) solvent
(4) solvent
strip
photoresist
(1)TMAH
(2) N-methyl-2-
pyrrolidone (NMP)
(3) TMAH
(4) TMAH
^
ELECTRODE FORMATION
expose
^
develop
(TMAH)
^
clean/dry
^
wet etch
(HBr, HBr+CI2,
CH4+H2, HCI, or
HF 0.5% soln.)
to alignment layer application
(refer back to Fig. 1-4)
Figure 1-4. Front glass AMLCD manufacturing (photolithography)
1-20
-------
1.3 PRODUCT SYSTEM
repeat 8 times
for each layer
THIN-FILM TRANSISTOR (TFT) FORMATION - PHOTOLITHOGRAPHY
thin film deposition:
gate metal (Mo/AI/Cr, etc.)
(sputter/PECVD);
SiO2 (APCVD);
SiNx(PECVD);
n+a:Si(PECVD);
a:si/SiNx (PECVD)
SiNx(PECVD);
source/drain (sputter);
ITO (sputter)
etch back
clean
resist coat
(polyimide)
soft bake
expose
develop
(TMAH)
resist
etch deposited
materials:
gate metal;
Si materials;
source/drain;
ITO
(RIE or wet etch)
clean/remove
resist deposits
dehydration bake
clean
(UV ozone)
to alignment layer application
(refer back to Fig. 1-4) -
Figure 1-5. Rear glass AMLCD manufacturing (photolithography)
1-21
-------
1.3 PRODUCT SYSTEM
1.4 ASSESSMENT BOUNDARIES
1.4.1 Life-Cycle Stages and Unit Processes
In a comprehensive cradle-to-grave analysis, the display system includes five life-cycle
stages: (1) raw materials acquisition; (2) materials processing; (3) product manufacture; (4)
product use, maintenance and repair; and (5) final disposition/end-of-life. Also included are the
activities that are required to affect movement between the stages (e.g., transportation). The
major processes within the life cycles of CRTs and LCDs, which are modeled in this study, are
depicted in Figures 1-6 and 1-7, respectively. Details on collecting data for these processes are
presented in Chapter 2.
1.4.2 Spatial and Temporal Boundaries
The geographic boundaries of this assessment are shown in Table 1-5. This LCA will
focus on the U.S. display market; therefore, the geographic boundary for the use and disposition
stages of displays is limited to the United States. Raw materials acquisition and material
processing for materials used in the manufacture of computer displays are done throughout the
world. Product manufacturing is done predominately in Asia, although there are foreign-owned
desktop display manufacturers operating plants in the United States and other countries.
Therefore, for purposes of this study, the geographic boundaries for raw material extraction,
material processing, and product manufacture are worldwide.
Table 1-5. Geographic coverage for each life-cycle stage
Life-cycle stage
Raw materials acquisition
Material processing
Product manufacture
Use
Disposition
Geographic coverage
worldwidea
worldwide3
worldwide3
United States
United States
a In this study, worldwide boundaries were considered; however,
the actual geographic locations for LCI data are presented in
Chapter 2 (Sections 2.2 and 2.3).
While the geographic boundaries show where impacts might occur for various life-cycle
stages, traditional LCAs do not provide an actual spatial relationship of impacts. That is,
particular impacts cannot be attributed to a specific location. Rather, impacts are generally
presented on a global or regional scale.
1-22
-------
1.4 ASSESSMENT BOUNDARIES
RAW MATERIALS
ACQUISITION
Acquisition of raw
materials for major
materials manufactured
(combined with aterials
processing stage)
Materials/Energy/Resources*
MATERIALS
PROCESSING
PRODUCT
MANUFACTURING
PRODUCT USE
Use
(effective and
manufactured lives)
DISPOSITION
Products/Waste (emissions, effluents, solid waste)
Note: Arrows indicate flows between life-cycle stages. The arrows also represent transportation of materials required to get from one process to another.
* Electricity generation and fuel production (fuel oils, natural gas, and LPG) processes are not shown but were attached to those processes that consume energy resourcesthroughout the life-cycle
Figure 1-6. CRT Life-Cycle
1-23
-------
1.4 ASSESSMENT BOUNDARIES
Materials/Energy/Resources*
RAW MATERIALS
ACQUISITION
Acquisition of raw
materials for major
materials manufactured
(combined with aterials
processing stage)
MATERIALS
PROCESSING
I
PRODUCT
MANUFACTURING
CCFL (lamp)
Light guide
Backlight unit
Polarizer
Liquid crystals
LCD glass
Color filter
patterning (on front
glass)
LCD panel &
module
Printed wiring
boards
Monitor assembly
PRODUCT USE
Use
(effective and
manufactured lives)
DISPOSITION
Products/Waste (emissions, effluents, solid waste)
Note: Arrows indicate flows between life-cycle stages. The arrows also represent transportation of materials required to get from one process to another.
* Electricity generation and fuel production (fuel oils, natural gas, and LPG) processes are not shown but were attached to those processes that consume energy resourcesthroughout the life-cycle
Figure 1-7. LCD Life-Cycle
1-24
-------
1.4 ASSESSMENT BOUNDARIES
This study addresses impacts from the life cycle of a desktop computer display
manufactured using 1997-2000 technology. The use and disposition stages cover a period that
represents the life of a display. Two lifespans are considered: (1) the "effective" life, defined as
the period of time the display is in use by primary, secondary, or even tertiary users before
reaching its final disposition; and (2) the "manufactured" life, defined as the designed durability
of a display. The effective life is estimated based on past and current use patterns of displays and
represents a realistic estimate of the lifespan. Because the effective life is subject to many
variables, including fluctuating market trends, it is also necessary to evaluate the displays over
their manufactured life. The manufactured life is estimated based on the manufacturer's
estimated durability of the display. Because of quickly changing technologies in this industry,
the effective life has been shorter than the manufactured life. The effective life, which is
currently the more realistic scenario is used as the primary scenario in the final results presented
in this study. However, the manufactured life is presented as an alternative scenario.
It is assumed that parameters that may change with time, such as available landfill space,
will remain constant throughout the lifespan of the product system. If the lifespan is relatively
short (i.e., within a time frame where significant changes in landfill space would not occur), the
preceding assumption is reasonable. If resources become more scarce within the lifespan, this
assumption could underestimate the impacts.
1.4.3 General Exclusions
Impacts from the infrastructure needed to support the manufacturing facilities (e.g.,
maintenance of manufacturing plants) are beyond the scope of this study. However, maintenance
of clean rooms used in the manufacturing of LCDs (and other components), which require
substantial amounts of energy, are considered part of the manufacturing process.
1-25
-------
REFERENCES
REFERENCES
Atlantic Consulting and IPU. 1998. LCA Study of the Product Group Personal Computers in the
EU Ecolabel Scheme. LCA Study Version 1.11. January.
Castellano, J. 1992. Handbook of Display Technology. Stanford Resources, Inc., San Jose, CA.
Curran, M.A. 1996. Environmental Life-Cycle Assessment. McGraw-Hill, New York, NY.
DisplaySearch. 2001. Personal communications with R. Young, Display Search, and J.G.
Overly, University of Tennessee, Center for Clean Products and Clean Technologies.
July.
DisplaySearch. 1998. DisplaySearch FPD Equipment and Materials Analysis and Forecast.
Austin, TX.
EPA (Environmental Protection Agency). 1995. EPA Office of Compliance Sector Notebook
Project - Profile of the Electronics and Computer Industry. EPA310-R-95-002. Office
of Enforcement and Compliance Assurance. Washington, DC. September.
Fava, J., R. Denison, R. Jones, B. Curran, M. Vigon, B. Selke, S. & J.A. Barnum. 1991.
Technical Framework for Life-Cycle Assessment. Society of Environmental Toxicology
and Chemistry & SETAC Foundation for Environmental Education, Inc. Washington,
DC.
FRC (Fuji Chimera Research). 1996. "The Future of Liquid Crystal and Related Display
Materials." Originally published in Japan by FRC and translated by InterLingua
Linguistic Services, Inc. Redondo Beach, CA. 1997.
ISO (International Standards Organization). 1996. ISO 14040, Environmental Management -
Life-cycle Assessment Principles and Framework. TC2071 SC 5N 77. International
Standards Organization, Paris.
Kincaid, L. et al. 1996. Cleaner Technologies Substitutes Assessment - A Methodology &
Resource Guide. U.S. Environmental Protection Agency, Office of Pollution Prevention
and Toxics. EPA 744-R-95-002. Washington, DC.
Koch, J. 1996. Evaluating Environmental Performance: A Case Study in the Flat Panel Display
Industry. University of Michigan, Natural Resources and Environment, Ann Arbor, MI.
April.
Koch, J. and G. Keoleian. 1995. "Evaluating Environmental Performance: A Case Study in the
Flat-Panel Display Industry." Proceedings of IEEE International Symposium on
Electronics and Environment, Orlando, May 1-3, pp. 158-165.
1-26
-------
REFERENCES
MCC (Microelectronics and Computer Technology Corporation). 1993. Environmental
Consciousness: A Strategic Competitiveness Issue for the Electronics and Computer
Industry. Austin, TX.
MCC. 1994. Environmental Industry Environmental Roadmap. Austin, TX.
MCC. 1998. Computer Display Industry and Technology Profile. EPA 744-R-98-005.
December.
NEC Corporation. 1998. "The LC Monitor Market as Predicted by a Monitor Manufacturer."
NEC Home Electronics, Inc. In Flat Panel Display 1998 Yearbook. Nikkei
Microdevices. Originally published by Nikkei Business Publicationa and translated by
InterLingua Linguistic Services, Inc., Redondo Beach, CA. 1997.
OTA (Office of Technology Assessment). 1995. Flat Panel Displays in Perspective. OTA-
ITC-631. U.S. Government Printing Office, Washington, DC. September.
Orango A.B. and Atlantic Consulting. 1999. "EU Eco-Label for Portable Computers-Suggested
Criteria." Version 1.12. Gotebprg, Sweden. May 19, 1999.
SRI (Stanford Resources, Inc.). 1998. Web site available at:
http://www.stanford.resources.com/sr/main/homepage. April.
Young, R. 1998. Personal communications with R.Young, DisplaySearch, and M.L. Socolof,
University of Tennessee Center for Clean Products and Clean Technologies, June.
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2. LIFE-CYCLE INVENTORY
Chapter 2
LIFE-CYCLE INVENTORY
A life-cycle inventory (LCI) is the identification and quantification of the material and
resource inputs and emission and product outputs from the unit processes in the life cycle of a
product system (Figure 2-1). For the Design for the Environment (DfE) Computer Display
Project (CDP), LCI inputs include materials used in the computer display product itself, ancillary
materials used in processing and manufacturing of the displays, and energy and other resources
consumed in the manufacturing, use, or final disposition of the displays. Outputs include
primary products, co-products, air emissions, water effluents, and releases to land. Specific unit
processes for CRTs and LCDs are represented by the boxes in Figures 1-6 and 1-7, and each unit
process has inputs and outputs particular to that process. Figures 2-2 and 2-3 also show each unit
process for both the CRT and LCD life cycles, and graphically displays how they are linked to
subsequent processes. This figure will be referred to throughout this chapter in the discussion of
each life-cycle stage.
INPUTS:
Display materials
Ancillary materials'
Energy/resources •
OUTPUTS:
Unit Process
• Air emissions
• Water effluent
•^•Releases to land
Primary products
^•Co-products
Figure 2-1. Unit process inventory conceptual diagram
This chapter describes the methods for collecting LCI data in the DfE CDP, and presents
LCI results. Section 2.1 describes the general methodology for LCI data collection, while
Sections 2.2 through 2.6 present the specific methodologies, data sources, data quality,
limitations and uncertainties for each life-cycle stage. Section 2.7 then concludes with the
combined LCI data for each monitor type.
More specifically, Section 2.2 presents the LCI methodology for the materials extraction
and materials processing (i.e., "upstream") life-cycle stages, including electricity generation.
Electricity is used in several processes throughout each monitor's life-cycle, and the electricity
generating process is linked to the processes that use electricity. As a consequence, the inventory
results from electricity generation are reported as part of the associated life-cycle stage for the
process to which it is linked. For example, electricity used in manufacturing a product
component is included in the manufacturing stage inventory, while electricity used during the use
stage is included in the use stage inventory.
2-1
-------
2. LIFE-CYCLE INVENTORY
CRADLE-TO-GATE STAGES
(Upstream and Manufacturing)
Japanese electric grid
[linked to manufacturing processes (*) below; upstream processes have imbedded
electricity generation inventory data]
Notes:
LPG = liquified petroleum gas
HIPS = high impact polystyrene
ABS = acrylonitrile butadiene styrene
PC = polycarbonate
* Manufacturing stage processes
USE STAGE
END-OF-LIFE STAGE
U.S. electric grid
(linked to use & EOL processes below; fuel processes
and secondary EOL processes have imbedded
electricity generation inventory data)
s »
landfilling of a
CRT
Key:
primary
data
secondary
data
Figure 2-2. CRT linked processes
2-2
-------
2. LIFE-CYCLE INVENTORY
CRADLE-TO-GATE STAGES
(Upstream and Manufacturing)
Japanese electric grid
[linked to manufacturing processes (*) below; upstream processes have imbedded
electricity generation inventory data]
Notes:
PMMA = poly(methyl methyacrylate)
PC = polycarbonate
PET = polyethylene terphthalate
LPG = liquified petroleum gas
* Manufacturing stage processes
liquid crystal
mfg*
polarizer mfg*
4
PET mfg
USE STAGE
END-OF-LIFE STAGE
U.S. electric grid
(linked to use & EOL processes below; fuel
processes and secondary EOL processes have
imbedded electricity generation inventory data)
patterning
color filters on
glass*
printed wiring
board mfg*
Key:
primary
data
secondary
data
Figure 2-3. LCD linked processes
2-3
-------
2.1 GENERAL METHODOLOGY
Section 2.3 presents the LCI methods for the product manufacturing life-cycle inventory,
which was developed from primary data collected through questionnaires designed and sent to
manufacturers for this study. Sections 2.4 and 2.5 present the methods for developing the use
and end-of-life (EOL) life-cycle stage inventories, respectively. Transportation is another
important aspect of a product life-cycle that can cause environmental impacts. Information
related to the transport of materials, products, and wastes is presented in Section 2.6. As the final
section of Chapter 2, Section 2.7, summarizes and discusses the entire inventory data over the
life-cycles of the CRT and LCD computer monitors. Sensitivity analyses are also discussed in
Section 2.7.
2.1 GENERAL METHODOLOGY
This section describes the data categories evaluated in the CDP LCI, the decision rules
used to determine which materials extraction and materials processing life-cycle stages (e.g.,
"upstream" processes) to evaluate in the study, and data collection methods. It also describes
procedures for allocating inputs and outputs from a process to the product of interest (e.g., a
display or display component) when the process is used in the manufacture, recycle, or disposal
of more than one product type at the same facility. Finally, it describes the data management and
analysis software used for the project and methods for maintaining overall data quality and
critical review.
2.1.1 Data Categories
Table 2-1 describes the data categories for which inventory data were collected, including
material inputs, energy inputs, natural resource inputs, emission outputs, and product outputs.
Inventory data were normalized to mass per functional unit (in the case of material and resource
inputs and emission or material outputs), megajoules (MJ) per functional unit (in the case of
energy inputs), or the number of components per functional unit (in the case of display
components). As discussed in Section 1.3, the functional unit is one desktop computer display
over its lifespan.
Data that reflected production for one year of continuous processes were scaled to one
functional unit. Thus, excessive material or energy associated with startups, shutdowns, and
changeovers were assumed to be distributed over time. Consequently, any environmental and
exposure modeling associated with the impact assessment reflects continuous emissions such that
equilibrium concentrations may be assumed. If the reporting year was less than one year for any
inventory item, the analysis was adjusted as appropriate.
2-4
-------
2.1 GENERAL METHODOLOGY
Table 2-1. LCI data categories
Data Category
Description
Material inputs (kg per functional unit)
Primary materials
Ancillary (process)
materials
Actual materials that make up the final product for a particular process. These can be
individual materials or a combination of materials that comprise a component part.
Materials that are used in the processing of a product for a particular process. Process
materials from monitor manufacturing could include, for example, etchants used during
photolithography which are washed away and not part of the final product, but are
necessary to manufacture the product.
Energy inputs (MJ per functional unit)
Process energy
Precombustion energy
Transportation energy
Energy consumed by any process in the life-cycle.
The energy expended to extract, process, refine, and deliver a usable fuel for combustion.
Energy consumed in the transportation of the materials or products in the life cycle.
Natural resource inputs (kg per functional unit)
Non-renewable
resources
Renewable resources
(e.g., water)
Materials extracted from the ground that are non-renewable, or stock, resources (e.g.,
coal).
Water or other renewable, or flow, resources (e.g., limestone) are included in the analysis.
Renewable resource data values are presented in mass of water consumed for a particular
process.
Emissions outputs (kg per functional unit)
Air
Water
Solid wastes
Mass of a product or material that is considered a pollutant within each life-cycle stage.
Air outputs represent actual gaseous or particulate releases to the environment from a
point or diffuse source, after passing through emission control devices, if applicable.
Mass of a product or material that is considered a pollutant within each life-cycle stage.
Water outputs represent actual discharges to either surface or groundwater from point or
diffuse sources, after passing through any water treatment devices.
Mass of a product or material that is deposited in a landfill or deep well.
Represents actual disposal of either solids or liquids that are deposited either before or
after treatment (e.g., incineration, composting), recovery, or recycling processes.
Products (kg of material or number of components per functional unit)
Primary products
Co-products
Material or component outputs from a process that are received as input by a subsequent
unit process within the display life cycle.
Material outputs from a process that can be used, either with or without further
processing, that are not used as part of the final functional unit product.
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Data were also collected on the final disposition of emissions outputs, such as whether
outputs are recycled, treated, and/or disposed. This information helps determine what impacts
will be calculated for a particular inventory item. Methods for calculating impacts are discussed
in Chapter 3, Life-Cycle Impact Assessment. The dispositions used for this project are as
follows:
• air,
• surface water,
landfill,
• land (other than landfill),
• treatment,
• recycling/reuse, and
• deep well injection.
Given the enormous amount of data involved in inventorying all of the inputs and outputs
for a product system, life-cycle assessment (LCA) practitioners typically employ decision rules to
make the data collection manageable and representative of the product system and its impacts.
Section 2.1.2 discusses the decision rules used in the CDP LCI.
2.1.2 Decision Rules
In an LCA, the materials extraction and materials processing life-cycle stages (referred to
as "upstream" life-cycle stages) include processes for extracting raw materials from the earth and
processing those raw materials into the materials used in the manufacture of the product of
interest. Examples of upstream processes include the mining of iron ore and its processing with
other materials into steel sheet or the extraction of petroleum from underground reserves and its
conversion into plastic pellets. A continuing challenge for LCA practitioners is to collect all the
appropriate data for a product system, including data for these upstream processes as well as data
for product manufacturing, use, and disposal processes. In this project, decision rules as to what
inventories should be included as upstream processes in the overall modeled life-cycle are based
on the materials used to manufacture the computer monitors. Also, which component parts to
include in the model depends on these decision rules. In considering upstream materials, a
combination of several factors, including availability of existing data were considered. For
considering which component manufacturing processes to include, the decision rules, plus
manufacturers willingness to participate, factored into our overall scope of what was included in
the analysis.
To help determine which upstream processes to include in the CDP LCI, first the bill of
materials (BOM) of the component parts and the materials that make up those parts (Tables 1-3
and 1-4) was reviewed. The quantities of those materials identified by MCC can be found in
Industry Profile Document (MCC, 1998). Using the MCC BOM allowed work to begin on
selecting and collecting upstream data before the actual BOM from the manufacturing stage was
obtained from the project's primary data collection effort. Final decisions on which upstream
processes to include were based on the BOM developed from data collected from manufacturers.
Tables 2-2 and 2-3 list the BOMs of the primary material inputs from the manufacturing of the
CRT and LCD, respectively. The mass quantities given in the tables are the primary material
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inputs to the manufacturing process and would be equivalent to the amount of material in the
final product plus excess or waste materials. While this is not exactly equivalent to the mass of
each material that makes up a finished product, it does represent the mass of primary materials
used to manufacture the finished product at participating facilities. Details of how these data
were obtained are presented in Section 2.3, which describes the manufacturing stage inventory.
Table 2-2. Bill of primary material inputs for a 17" CRT monitor
Material/Component
Sub-component
Lead oxide glass
Steel
Plastics
Lead
Polycarbonate (PC)
Styrene-butadiene co-polymer
Polyethylene ether (PEE)
Acrylonitrile-butadiene-styrene (ABS)
High-impact polystyrene (HIPS)
Triphenyl phosphate
Tricresyl phosphate
Phosphate ester
Printed wiring boards (PWB) and components
Cables/wires
Aluminum (heat sink)
Nickel alloy (invar)
CRT shield assembly
Ferrite
Deflection yoke assembly
Demagnetic coil
Video cable assembly
Power cord assembly
Electron gun
CRT magnet assembly
Audio cable assembly
Frit
Solder
Phosphors
Aquadag
Other (misc.)
TOTAL
Mass (kg) a
9.76
5.16
3.04
0.85
0.45
0.27
0.27
0.24
0.17
0.15
0.13
0.11
0.11
0.10
0.08
0.07
0.07
0.03
0.02
0.02
0.06
21.16
0.45
0.92
0.83
0.74
0.32
0.15
0.05
0.02
0.01
weight % of total inputs a
46.1%
24.4%
14.4%
4.00%
2.13%
1.29%
1.29%
1.14%
0.80%
0.71%
0.60%
0.54%
0.54%
0.47%
0.36%
0.34%
0.32%
0.13%
0.08%
0.07%
0.30%
100%
2.1%
4.36%
3.91%
3.47%
1.52%
0.71%
0.25%
0.11%
0.04%
a Based on the primary material inputs to the manufacturing process,
materials.
including material in the final product plus excess or waste
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Table 2-3. Bill of primary material inputs for a 15" LCD monitor
Material/Component
Steel
Plastics
Subcomponent
Polycarbonate (PC)
Poly(methyl methacrylate) (PMMA)
Styrene-butadiene copolymer
Polyethylene ether (PEE)
Triphenyl phosphate
Polyethylene terephthalate (PET)
Glass
Printed wiring boards (PWB) and components
Cables/wires
Aluminum (heat sink, transistor)
Solder (60% tin, 40% lead)
Color filter pigment
Polyvinyl alcohol (PVA) (for polarizer)
Liquid crystals, for 15" LCD, unspecified b
Backlight lamp (cold cathode fluorescent lamp, CCFL)
| Mercury
Transistor metals, other (e.g., Mo, Ti, MoW)
Indium tin oxide (ITO) (electrode)
Polyimide alignment layer
Other (e.g., adhesives, spacers, misc.)
TOTAL
Mass (kg) a
2.53
1.78
0.59
0.37
0.23
0.13
0.04
0.04
0.01
0.0023
0.0019
0.0019
0.0005
0.0005
0.0031
5.73
0.52
0.45
0.36
0.30
0.09
0.06
3.99E-06
weight % of total inputs a
44.12%
30.98%
10.31%
6.52%
4.08%
2.34%
0.66%
0.65%
0.15%
0.04%
0.03%
0.03%
0.01%
0.01%
0.05%
100%
9.00%
7.80%
6.31%
5.23%
1.61%
1.03%
0.0001%
a Based on the primary material inputs to the manufacturing process, including material in the final product plus excess or waste
materials.
b This does not include all liquid crystals, as those specified as individual chemicals are in very small amounts and included in the
"other" category.
The decision rule process begins by assessing the materials and components in Tables 2-2
and 2-3 for the following attributes:
1. The mass (M) contribution of each component and material in the display. The mass is
important in order to account for the majority of materials and components that make up a
display, but also because the more significant the material or component by mass, the
more materials and resources may be required to manufacture the material or component
and thus it may have a significant environmental impact.
2. Materials that are of known or suspected environmental (Env) significance (e.g., toxic).
As this is an environmental life-cycle assessment, consideration of materials or
components that are known to or are suspected to exhibit an environmental hazard are
also included to the extent feasible.
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2.1 GENERAL METHODOLOGY
3. Materials that are known or suspected to have a large energy (E) contribution to the
systems energy requirements. Energy impacts are of great interest to the use and
manufacture of display monitors and, therefore, priorities were given to including
materials or components that are known to or suspected to consume large amounts of
energy.
4. Materials or components that are functionally (F) significant to the display.
"Functionally significant" is defined as important to the technically successful operation
of the display. For example, the liquid crystals in an AMLCD would be "functionally
significant" while screws, gaskets, or the plastic cover would not be.
5. Materials or components that are physically (P) unique in the CRT as compared to the
LCD and vice versa. The physical uniqueness of a material or component could be
identified by chemical makeup or by size. An example of the latter would be if the
plastic casing for the CRT and LCDs were made of the same material, but the CRT casing
had substantially more material by weight.
The priority scheme depicted in Figure 2-4 provides guidelines for applying the CDP
decision rules. Material or component inputs that account for more than five percent of the total
mass of a display technology were given top priority for data collection, as were those of known
or suspected environmental or energy significance and those that are functionally significant or
physically unique. Of less emphasis in trying to obtain data, but still included if possible, were
materials or components that are functionally significant but physically similar to those in the
other technologies, and those that were between 1 and 5% of the total mass of the display.
Recognizing the limitations of project resources, materials or components that account for less
than one percent of total mass or are not otherwise significant or unique were excluded a priori.
Based on this hierarchy and on review of the preliminary BOMs, Tables 2-4 and 2-5
present how components were rated based on the priority scheme, and which ones were included
in the analysis. If a material or component was included in the analysis as a separate process, it is
listed in the last column of Tables 2-4 and 2-5 by what life-cycle stage that process is in (i.e.,
upstream or manufacturing process). If a material or component was only included as part of
another process, and not as a separate process in the profile, the process in which that material or
component is found is provided in the last column.
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2.1 GENERAL METHODOLOGY
MATERIAL/COMPONENT INPUTS:
- >5% of total mass
environmental concern
- energy concern
functionally significant
- physically unique
- 1-5% of total mass
L- <1% of total mass,,
k- not otherwise
significant /Excluded from
unique*
analysis
Figure 2-4. Decision rule guidelines
*e.g., materials are excluded if they are not of known environmental significance (for example, toxic) or are not
physically unique.
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2.1 GENERAL METHODOLOGY
Table 2-4. Decision rule priorities and scope of analysis for the primary material inputs
of the 17" CRT monitor
Material/Component
Sub-component
Lead oxide glass
Steel
Plastics
Lead
Polycarbonate (PC)
Styrene-butadiene co-polymer
Polyethylene ether (PEE)
Acrylonitrile-butadiene-styrene (ABS)
High-impact polystyrene (HIPS)
Triphenyl phosphate
Tricresyl phosphate
Phosphate ester
Printed wiring boards (PWB) and components
Cables/wires
Aluminum (heat sink)
Nickel alloy (invar)
CRT shield assembly
Ferrite
Deflection yoke assembly
Demagnetic coil
Video cable assembly
Power cord assembly
Electron gun
CRT magnet assembly
Audio cable assembly
Frit
Solder
Phosphors
Aquadag
Other (misc.)
Decision rule
M, F, P, E, Env
P, Env
M
—
M
M
M
M
none
none
P
P
M, E, Env
none
M (<5%), E
M (<5%), P
none
P
F,P
F,P
none
none
F, P
P
none
F, P, E, Env
Env
F, P
F, P
Included in analysis as:
manufacturing process
upstream process
upstream process
upstream process
upstream process
part of monitor assy, process
upstream process
upstream process
part of monitor assy, process
part of monitor assy, process
part of monitor assy, process
manufacturing process
part of monitor assy, process
upstream process
upstream process
part of monitor assy, process
upstream process
part of monitor assy, process
part of monitor assy, process
part of monitor assy, process
part of monitor assy, process
part of tube mfg. process
part of monitor assy, process
part of monitor assy, process
manufacturing process
part of monitor assy, process
part of tube mfg. process
part of tube mfg. process
miscellaneous
M = mass is greater than 1% of the total display weight; Env = environmental/toxic concern; E = energy concern;
F = functional (technological) importance; P = physically unique.
Note: The CRT processes included in the CDP LCA were presented in Figures 1-6 and 2-2.
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Table 2-5. Decision rule priorities and scope of analysis for the primary material inputs
of the 15" LCD monitor
Material/Component
Steel
Plastics
Sub-component
Polycarbonate (PC)
Poly(methyl methacrylate) (PMMA)
Styrene-butadiene co-polymer
Polyethylene ether (PEE)
Triphenyl phosphate
Polyethylene terephthalate (PET)
Glass
Printed wiring boards (PWB) and components
Cables/wires
Aluminum (heat sink, transistor)
Solder (60% tin, 40% lead)
Color filter pigment
Polyvinyl alcohol (PVA) (for polarizer)
Liquid crystals, for 15" LCD
Backlight lamp (cold cathode fluorescent lamp)
Mercury
Transistor metals, other (e.g., Mo, Ti, MoW)
Indium tin oxide (ITO) (electrode)
Polyimide alignment layer
Other (e.g., adhesives, spacers, misc.)
Decision rule
M
—
M
M, P
M
M
M (<5%)
M (<5%), P
M
M, E, Env
M (<5%), E
Env
P
none
F, P, Env
F, P, Env
Env
F,P
F,P
F,P
Included in analysis as:
upstream process
upstream process
upstream process
upstream process
part of monitor assy, process
part of monitor assy, process
upstream process
manufacturing process
manufacturing process
part of monitor assy, process
upstream process
part of monitor assy. & module mfg.
processes
part of color filter patterning
part of polarizer mfg. process
manufacturing process
manufacturing process
part of backlight lamp process
part of module mfg. process
part of module mfg. process
part of module mfg. process
miscellaneous
M = mass is greater than 1% of the total display weight; Env = environmental/toxic concern; E = energy concern;
F = functional (technological) importance; P = physically unique.
Note: The LCD processes included in the CDP LCA were presented in Figures 1-7 and 2-3.
2.1.3 Data Collection and Data Sources
Data were collected from both primary and secondary sources. Primary data are directly
accessible, plant-specific, measured, modeled, or estimated data generated for the particular
project at hand. Secondary data are from literature sources or other LCAs, but are specific to
either a product, material, or process used in the manufacture of the product of interest.
Table 2-6 lists the types of data (primary or secondary) used for each life-cycle stage in
the CDP LCI. In general, greater emphasis was placed on collecting data and/or developing
models for product manufacturing, use, and end-of-life. Primary data were collected from
product and component manufacturers (in the U.S., Japan, and Korea), and CRT recyclers who
voluntarily agreed to participate in the project. When proprietary data were involved, the
University of Tennessee (UT) Center for Clean Products and Clean Technologies entered into
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confidentiality agreements with the affected company. In addition, to both protect confidentiality
and better represent the various manufacturing processes, data for particular processes that were
collected from more than one company, where possible, and aggregated. Attempts were made to
get at least two companies to contribute data for each particular process in the manufacturing
life-cycle stage, which resulted in some process datasets being the aggregate of multiple (2-7)
companies data. However, this was not feasible in every case and some datasets were simply the
data of one company. Details of the data aggregation methods are provided in Section 2.3.
Data for the use stage were modeled specifically for this project by UT researchers, but
were based on secondary data (i.e., secondary data were built upon to create the data used in the
inventory for the use life-cycle stage). Data associated with the electricity generation were also
based on secondary data, but modeled for this project. Transportation information (e.g.,
transportation mode and distances) were collected from the manufacturers that provided primary
data. These data were linked to secondary data inventories of fuel inputs and emissions outputs
for various types of transport vessels. Transportation data cover movement of materials and
components both into and out of a facility, but do not include transportation of packaging or
distribution of the finished display to the consumer. Finally, secondary data were used for
upstream processes. More details on each of these data collection efforts are provided in
subsequent sections of this chapter.
Table 2-6. Data types by life-cycle stage
Life-cycle stage
Upstream
(materials extraction and processing)
Product and component manufacturing
Use
Final disposition
(recycling and/or disposal)
Packaging, transportation, distribution
Data types
Secondary data.
Primary data, except secondary data used for frit.
Modeled using secondary data; maintenance and repair are not
included in the analysis.
Modeled using secondary data plus primary data from CRT
recycling facilities.
Primary data from product and component manufacturers for
transport mode and distance; secondary data for fuel inputs and
emissions outputs for the transport vessel. Packaging and
distribution not included.
In some instances, neither primary nor secondary data were available. For example,
CRTs are a much more mature technology than the LCD, and end-of-life (EOL) data are much
less prevalent for the LCD than for the CRT. Where primary and secondary data are lacking,
various assumptions and modeling serve as defaults.
2.1.4 Allocation Procedures
An allocation procedure is required when a process within a system shares a common
management structure, or where multiple products or co-products are produced. In the CDP LCI
allocation procedures are used when processes or services associated with the functional unit
(e.g., a desktop computer display over its lifetime) are used in more than one product line at the
same facility (e.g., notebook computers, televisions). For example, transistors are used in LCD
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2.1 GENERAL METHODOLOGY
desktop computer displays, but also in other LCD technologies, such as notebook computer
displays. If a facility uses a single process to manufacture transistors for both desktop and
notebook computer display, inputs and outputs are allocated among the product lines to avoid
over-estimating the environmental burdens associated with the product under evaluation.
The International Standards Organization (ISO, 1996) recommends that wherever
possible, allocation should be avoided or minimized. This may be achieved by sub-dividing the
unit process into two or more sub-processes, some of which can be excluded from the system
under study. In the example above, if a manufacturer of transistors supplied only desktop
computer LCD manufacturers, no allocation would be necessary from that manufacturer.
However, it is more likely that the transistor manufacturer would have a larger customer base,
including manufacturers of various products other than liquid crystal desktop computer displays.
This requires allocation of flows from the manufacturing of transistors for several products to
those associated only with desktop computer displays. As suggested by ISO, if sub-processes
within the transistor facility can be identified that distinguish between transistors manufactured
for LCDs and for other products, the latter sub-processes can be eliminated from the analysis,
thus reducing allocation procedures.
In this study allocation procedures are used as follows:
• Inventory data for utilities and services common to several processes are allocated to
reflect the relative use of the service. For example, fuel inputs and emission outputs from
electric utility generation are allocated to a display or display component according to the
actual or estimated electricity consumed during the manufacture, use, or final disposition
of the product. Similarly, fuel inputs and emission outputs from commercial transport of
a display component to a display assembler are allocated to the display component
according to the mass of the component, the distance traveled, and the fraction of the
transport vehicle's capacity occupied by the number of components shipped.
• Where a unit process produces co-products, the burdens associated with the unit process
are allocated to the co-product on a mass basis. In the transistor example above, burdens
are allocated according to the total mass of transistors used in desktop displays and the
mass used in notebook computers. Total mass can be calculated from sales records which
document the number of transistors delivered to different customers and measured mass
of a set number of transistors.
Allocation is also necessary when a single process produces both energy and products. In this
case, the inputs are partitioned among the energy and products, as appropriate, to avoid allocating
inapplicable chemical burdens to energy production. However, this scenario was not
encountered in the CDP LCI.
2.1.5 Data Management and Analysis Software
The data that were collected for this study were either obtained from questionnaires
developed for this project, from existing databases, or from primary or secondary data collected
by the UT Center for Clean Products and Clean Technologies. All these data were transferred to
spreadsheets, which were then imported into a Life-Cycle Design Software Tool developed by
the Center for Clean Products and Clean Technologies with funding from the EPA Office of
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2.1 GENERAL METHODOLOGY
Research and Development and Saturn Corporation. The software tool was developed to store
and organize life-cycle inventory data and to calculate life-cycle impacts for a product profile.
Written using Microsoft FoxPro programming software, the tool is designed to allow flexibility
in conducting life-cycle design and life-cycle assessment functions. It provides the means to
organize inventory data, investigate alternative scenarios, evaluate impacts, and assess data
quality.
The UT Life-Cycle Design Software Tool organizes data in such a way that each process
inventory is independent. Customized "profiles" (e.g., the manufacture of a CRT or the whole
life-cycle of an LCD) can be developed by linking processes together. The tool has the flexibility
to modify or replace any particular process within a profile to evaluate potential alternatives. The
data provided in this study may serve as a baseline to compare alternatives or modifications to
particular processes. The models developed for the life-cycles of the CRT and LCD in this study
can remain useful as many of the individual processes in the CRT and LCD life-cycles will likely
remain constant (e.g., steel manufacturing, plastics manufacturing). Changes to specific
processes can be made to conduct analyses of current or emerging process or technology changes.
Relatively quick life-cycle analyses can be conducted on future product or process
improvements, given the baseline data already available through this study.
2.1.6 Data Quality
LCI data quality can be evaluated based on the following data quality indicators (DQIs):
(1) the source type (i.e., primary or secondary data sources); (2) the method in which the data
were obtained (i.e., measured, calculated, estimated); and (3) the time period for which the data
are representative. LCI DQIs are discussed further in Life-Cycle Assessment Data Quality: A
Conceptual Framework (SETAC, 1994). CDP data quality for each life-cycle stage is discussed
in detail in Sections 2.3 through 2.6 and summarized below.
For the primary data collected in this project, participating companies reported the
method in which the data were obtained and the time period for which the data are representative.
Data from the 1997-2000 time period were sought, with the most recent data preferred.
Similarly, the time period of secondary data and method in which the data were originally
obtained was also recorded, where available. Secondary data cover a broader time period, with
data for most materials from the 1997 to 1998 time period, and data for most fuels from the 1983
to 1993 time period.
Anomalies and missing data are common hurdles in any data collecting exercise.
Anomalies are extreme values within a given data set. Any anomaly identified during the course
of this project that is germane to project results was highlighted for the project team and
investigated to determine its source (e.g., mis-reported values). If the anomaly could be traced to
an event inherently related to the process, it was left in the data set. If, however, the anomaly
could not be accounted for, it was removed from the data set. Specific anomalies highlighted by
the project team are discussed in Section 2.7, Summary of Life-Cycle Inventory Results.
We attempted to account for missing data by replacing it hierarchically. That is, if
specific primary data were missing, secondary data were used. Where neither primary nor
secondary data were available, such as data on the percent of LCD desktop displays recycled or
remanufactured, assumptions were made and a sensitivity analysis was performed. In the cases
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2.1 GENERAL METHODOLOGY
where no data were found or reasonable assumptions could not be made, these deficiencies are
reported.
Any proprietary information required for the assessment was subject to confidentiality
agreements between the Center for Clean Products and Clean Technologies and the participating
company. Proprietary data are presented as aggregated data to avoid revealing the source.
Further, any averaged process data obtained from fewer than three companies are also aggregated
to avoid revealing individual inventory items from individual companies.
2.1.7 Critical Review
Critical review is a technique to verify whether an LCA has met the requirements of the
study for methodology, data, and reporting, as defined in the goal definition and scoping phase.
A critical review process was maintained in the CDP LCA to help ensure that the following
criteria were met:
• the methods used to carry out assessments are consistent with the EPA, SETAC, and ISO
assessment guidelines;
• the methods used to carry out assessments are scientifically and technically valid within
the LCA framework;
• the data used are appropriate and reasonable in relation to the goals of the study;
• the interpretations reflect the limitations identified and the goals of the study; and
• the study results are transparent and consistent.
A project Core Group and Technical Work Group, both consisting of representatives
from industry, academia, and government, and EPA's DfE Work Group provided critical reviews
of the assessment. Members of these groups are listed in Appendix C, Critical Review. The Core
Group served as the project steering committee and was responsible for approving all major
scoping assumptions and decisions. The Technical Work Group and the DfE Work Group
provided technical guidance and reviews of all major project deliverables including the final
LCA report.
In addition to the critical review process, primary data collected were double-checked
with the original source to ensure that their data are presented accurately. Additional details on
the data verification process for primary data are presented in Sections 2.3 and 2.5.
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2.2 MATERIALS EXTRACTION & MATERIALS PROCESSING
2.2 MATERIALS EXTRACTION AND MATERIALS PROCESSING (UPSTREAM
LIFE-CYCLE STAGES)
2.2.1 Methodology
The inventories included in the materials extraction and materials processing (upstream)
life-cycle stages are those of the major primary materials found in the CRT or LCD monitor, as
well as major ancillary materials required to manufacture the monitors. Inventories for electricity
generation and fuels, which may be used in several life-cycle stages (e.g., to manufacture the
products or to use the products), are also presented.
The inventories for extraction and processing of major materials were obtained from
existing LCI databases. Electricity generation inventories were developed for this project from
secondary sources that describe the distribution of fuels for different electric grids and the fuel
inputs and emission outputs associated with different fuel types. The methodologies for
developing these inventories are summarized below.
2.2.1.1 Upstream materials processes
Materials for which upstream processes were included in the CRT and LCD life-cycles
were selected based on the decision rules described in Section 2.1.2, as well as the availability of
secondary data for those materials. An attempt was made to include materials with a mass
greater than or equal to one percent of the overall inputs to the product manufacture, or materials
that may contribute to a large amount of energy use or have environmental concern. Tables 2-4
and 2-5 in Section 2.1.2 listed the decision criteria for primary materials/components that are
included either as separate processes or as part of another process. The upstream materials
processes for which inventory data were obtained for this project are presented in Table 2-7.
To determine which source or sources of secondary data to use, nine LCI databases were
evaluated against 11 selection criteria in a technical memorandum presented to the project review
teams (see Appendix D). Based on this analysis the project team chose the Environmental
Information and Management Explorer (EIME) database and the Database for Environmental
Analysis and Management (DEAM), two life-cycle inventory databases developed by the
Ecobilan (Ecobalance) Group (Ecobilan, 1999). EIME was developed by Ecobilan specifically
for electronics and the electronics industry and covers many of the materials specific to the CDP,
while the DEAM database includes materials not covered by EIME. Combined, these databases
contain detailed inventories of materials extraction and processing activities for most of the
materials of interest in this project.
In the Ecobilan inventory for a particular material, the functional unit is a set mass of the
material. Inputs and outputs are therefore given in terms of mass or other appropriate unit per
unit mass of material. These data were imported into the UT Life-Cycle Design Software Tool
discussed in Section 2.1.5, where they were linked to the mass of material used in the
manufacture of a display monitor to develop inventories specific to the CDP. The associated
amounts of each material were presented in Tables 2-2 and 2-3 in Section 2.1.2. How these
materials are linked to other processes in the CRT and LCD profiles are shown in Figures 2-2
and 2-3 at the beginning of this chapter.
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2.2 MATERIALS EXTRACTION & MATERIALS PROCESSING
The materials inventories from Ecobilan also contain data for electricity generation, as
appropriate, and in some cases, for transportation. Electricity generation and transportation data
that were included in the Ecobilan inventories could not be separated from the inventory data for
materials extraction and conversion processes. Therefore, when electricity generation and
transport data were included in the Ecobilan inventories, the electricity and transport data
collected specifically for this project were not used with the upstream process data.
Table 2-7. Materials having upstream processes included in
the CDP LCA
Material
CRT
LCD
METALS
aluminum
ferrite
lead
nickel alloy (invar)
steel
/
/
/
/
/
/
/
POLYMERS
acrylonitrile-butadiene styrene (ABS)
high impact polystyrene (HIPS)
polycarbonate (PC)
polyethylene terphthalate (PET)
poly(methyl methacrylate) (PMMA)
styrene-butadiene co-polymer
/
/
/
/
/
/
/
/
ANCILLARY MATERIALS
natural gas (used to represent LNG)
/
2.2.1.2 Electric grids
Electricity is used in several processes throughout the life-cycle of the CRT and LCD
monitors, and in some instances in large amounts. Therefore, the inventory for electricity
generation is included in the scope of this project.
As described in Chapter 1, Section 1.4.2, the geographic boundaries of this project are
worldwide for upstream and product manufacturing processes and limited to the United States
for the use and end-of-life stages. In addition, most CRT and LCD manufacturing is done in Asia
and most product manufacturing data collected in this study were from the United States or
Japan, except for two LCD manufacturing data sets collected from Korean manufacturers.
Therefore, the inventory associated with electricity generation during manufacturing was based
on either the Japanese or U.S. electric grids, depending on the particular process or component
being manufactured. Where data were obtained from more than one country for the same
process, only one electric grid inventory could be used for a single process. In these cases, the
Japanese electric grid was used since the majority of manufacturing data are from Japanese
companies. The inventory for electricity generated during use and EOL processing was based on
the U.S. electric grid.
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2.2 MATERIALS EXTRACTION & MATERIALS PROCESSING
The methodology and results for the electricity generation inventories are detailed in
Appendix E, which presents the electric grid technical memorandum prepared for this project.
The inventories were developed by first compiling U.S. inventory data for each of the major
generation categories or fuel types, including electricity generated from coal, gas, petroleum, and
nuclear fuels. These inventories were then combined with data on net electricity generation by
fuel type in the U.S. and Japanese electric grids (Table 2-8) to develop the country-wide electric
generation inventories. The inputs and outputs for the electricity generation inventories are
presented in terms of mass or radioactivity per kWh of electricity generated. Inventories were
not included for hydroelectric and renewable energy generation categories due to the scarcity of
data on inputs and outputs for these categories. In addition, renewables account for only a small
fraction of total U.S. electricity generation.
Table 2-8. Net electricity generation by fuel type
Fuel
Coal
Gas
Petroleum
Nuclear
Hydro
Other
Net electricity generation
United States (percent)
57
9
3
20
11
<1
Japan (percent)
18
20
21
31
9
1
Sources: U.S.: EIA, 1999a; Japan: EIA, 1997; FEPC, 1996.
Note that the Japanese grid inventory is based on the same fuel-specific inventories
developed for the U.S. grid, but uses the average distribution of fuels for the Japanese grid (EIA,
1997, FEPC, 1996). This introduces some uncertainty into the Japanese electric grid since
Japanese technologies, efficiencies, and pollution control techniques are likely to differ
somewhat from their U.S. counterparts. However, the U.S. fuel-specific inventories were used to
conserve project resources, rather than expending considerable effort on collecting inventory data
from Japanese utilities.
The electricity generation inventories presented in Appendix E are shown as separate
process inventories. However, in the overall analysis, they are linked to the manufacturing, use
and EOL life-cycle stages, as appropriate. That is, where electricity is used in a process in any of
those life-cycle stages, the inputs and outputs from generating the amount of electricity needed is
allocated to that process. Note that the U.S. and Japanese electricity generation inventories
developed for this project are not linked to the upstream life-cycle stages for materials used to
manufacture CRT and LCD desktop computer displays. Electricity generation data were already
included in the upstream material inventories received from Ecobilan.
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2.2 MATERIALS EXTRACTION & MATERIALS PROCESSING
2.2.1.3 Fuels
Several fuels are used in manufacturing and end-of-life processes during the life-cycle of the
CRT and LCD monitors, and in some instances in large amounts.1 Therefore, fuel production
inventories are included in the scope of this project. These inventories are included in the life-
cycle stage in which the fuels are actually consumed (e.g., product manufacturing or end-of-life)
instead of in the upstream (materials processing) life-cycle stage. The following fuel inventories
are included in both the CRT and LCD LCIs:
• natural gas (also used to represent LNG),
• liquified petroleum gas (LPG),
fuel oil #2 (distillate),
• fuel oil #6 (residual), and
• fuel oil #4 (average of residual and distillate).
Fuel inventories were obtained from Ecobilan. In the Ecobilan inventories, the functional
unit is a set mass of the material, with inputs and outputs given in terms of mass or other
appropriate unit per mass of material (product) produced. These data were imported into the UT
Life-Cycle Design software tool where they were linked to the mass of fuel used in different
processes in the life-cycle of a display. How the fuel processes are linked to other processes in
the CRT and LCD profiles was shown in Figures 2-2 and 2-3.
2.2.2 Data Sources and Data Quality
2.2.2.1 Upstream material and fuel processes
Table 2-9 summarizes data source and data quality information for the data received from
Ecobilan, which are all secondary data for the purposes of the CDP. In addition to information
about CDP data quality indicators (e.g., original source of data, year of data, method in which
data were obtained, and geographic boundaries), the table lists whether or not electricity
generation or transport data were included in the inventories. This information is important
because: (1) electricity generation and transportation data are not from the same sources and
therefore are not necessarily consistent among data sets; and (2) transportation data are not
included in several of the upstream processes, and are thus a data gap for those processes.
As revealed in Table 2-9, the Ecobilan data were derived from various sources, including
European data sources and U.S. data sources. In addition, the temporal boundaries of the data
vary, with some data being as recent as 1998 but others being from as early as 1975. Electricity
generation data are included in all of the inventories, but transportation data are only included in
six of 16 data sets. All of these factors create some inconsistencies among the data sets and
reduce the data quality when used for the purposes of the CDP. However, this is a common
difficulty with LCA, which often uses data from secondary sources for upstream processes to
avoid the tremendous amount of time and resources required to collect all the needed data.
Fuels are also used in the materials processing life-cycle stage, but fuel production processes should
already be accounted for in the materials inventories obtained from Ecobilan.
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2.2 MATERIALS EXTRACTION & MATERIALS PROCESSING
Table 2-9. Data sources and data quality for the Ecobilan inventories
Material
Electricity
generation
included?
Transport
included?
Year of
data
Original source b
METALS
aluminum
ferrite
lead
nickel-alloy (invar) c
steel
Y
Y
Y
Y
Y
-
-
-
Y (nickel)
-
-
-
Unknown
1991 (nickel)
1975-1990 d
ETH
not provided
ETH
ETH
FOEFL, others d
POLYMERS
acrylonitrile-butadiene styrene (ABS)
high impact polystyrene (HIPS)
polycarbonate (PC)
polyethylene terphthalate (PET)
poly(methyl methacrylate) (PMMA)
styrene-butadiene co-polymer f
Y
Y
Y
Y
Y
Y
Ye
Ye
Ye
Ye
Ye
Ye
1997
1997
1997
1998
1997
1997
Boustead
Boustead
Boustead
Boustead
Boustead
Boustead
FUELS
natural gas
liquified petroleum gas (LPG)
fuel oil #2
fuel oil #6
fuel oil #4 g
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
1987-98
1983-93
1983-93
1983-93
1983-93
six sources cited
seven sources cited
seven sources cited
seven sources cited
seven sources cited
Y: yes, included in inventory.
— : not included in inventory.
a In general, the Ecobilan inventories provide descriptions of data quality but often do not report how data were collected (e.g.,
measured, estimated, etc.). Therefore, information on the data collection method is not presented here.
b Sources: ETH (EidgenOssische Technische Hochschule): Data from the ETH (Swiss Federal Institute of Technology)
(Ecobilan, 1999). FOEFL (Swiss Federal Office of Environment, Forests and Landscape): Data from the Eco-inventory of
Packaging published by the Swiss FOEFL; FOEFL is also known as BUWAL, the acronym in German (Ecobilan, 1999).
Boustead: LCI database developed by Boustead Consulting (Ecobilan, 1999).
In general, the geographic boundaries for different sources are as follows: (1) ETH and FOEFL data are from Europe; (2)
Boustead data are from Europe and/or the United States; and (3) miscellaneous sources may be European or U.S. data.
c The invar inventory is a combination of 36% of the nickel inventory and 64% of the ferrite inventory.
d The steel inventory was originally provided by Ecobilan without detailed documentation; however, DEAM data that were
received later have inventories for several steel production processes. The sources listed here are for the DEAM data.
6 Boustead addresses transportation; however, the extent to which it is included in a particular process inventory is uncertain.
f The styrene-butadiene process is the 50/50 average of the styrene and butadiene processes.
g The fuel oil #4 process is the 50/50 average of the fuel oil #2 and fuel oil #6 processes.
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2.2 MATERIALS EXTRACTION & MATERIALS PROCESSING
2.2.2.2 Electric grids
Several sources of data were consulted to generate the fuel-specific inventories that were
used to create the overall electricity generation inventories. Table 2-10 summarizes the data
sources and some of the data quality indicators for these inventories. Appendix E discusses the
data sources and data quality in detail.
As shown in Table 2-10, the electricity generation data were obtained primarily from
secondary sources and include data from the mid-1990s as well as data from an unknown time
frame. Most are based on measured data collected by the original source, although some are
estimated or the data collection method is unknown. Finally, most of the fuel-specific
inventories are based on U.S. data, indicating these data are probably less representative and thus
of lower quality when applied to the Japanese electric grid.
Table 2-10. Data sources and data quality indicators for the
electric generation inventories
Type of data
Net electricity
generation by fuel
Primary inputs
(Fuel)
Ancillary inputs
Air emissions
Water releases
Radioactive air and
water releases
Solid wastes
Source
U.S. Energy Information
Administration (EIA)
EIA
EIA, California Energy
Commission, utility contacts
Primarily AP-42 plus other
sources b
Oak Ridge National
Laboratory (ORNL) c
ORNLd
ORNLe
Year of publication
1997
1997
Varies
Varies, but mostly
AP-42 data from 1995
1994
1995
1994
Data collection
method
Measured
Measured
Varies a
Varies a
Unknown
Measured
Unknown
Geographic
boundaries
U.S. and
Japan
U.S.
U.S.
U.S.
U.S.
U.S.
U.S.
a Includes emission factors from measured and estimated data, plus data where data collection methods were not reported.
b AP-42 is the U.S. EPA's compilation of Air Pollutant Emissions Factors (EPA, 1996).
c Coal-fired water release data from ORNL report addressing the externalities of coal fuel cycles (ORNL, 1994).
d From ORNL report addressing the externalities of nuclear fuel cycles (ORNL, 1995).
6 Coal-fired solid waste data from ORNL report addressing the externalities of coal fuel cycles (ORNL, 1994); radioactive solid
waste data from ORNL report addressing the externalities of nuclear fuel cycles (ORNL, 1995).
2.2.3 Limitations And Uncertainties
The limitations and uncertainties associated with the upstream materials, fuels, and
electricity generation inventories are primarily due to the fact that these inventories were derived
from secondary sources and thus are not tailored to the specific goals and boundaries of the CDP.
Because the data are based on a limited number of facilities and have different geographic and
temporal boundaries, they are not necessarily representative of current industry practices or of
industry practices in the geographic and temporal boundaries defined for the CDP (see
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2.2 MATERIALS EXTRACTION & MATERIALS PROCESSING
Section 1.4). These are common limitations and uncertainties of LCA, which strives to evaluate
the life-cycle environmental impacts of entire product systems and is therefore limited by
resource constraints which do not allow the collection of original, measured data for every unit
process within a product life cycle. Despite these limitations and uncertainties inherent in LCA
methodology itself, LCA remains useful and, indeed is increasingly used by industry,
governments, and other stakeholders as part of a comprehensive decision-making process or to
understand broad or general environmental trade-offs.
2.2.3.1 Upstream material and fuel processes
Because they are derived from secondary sources, the upstream materials and fuels
inventories used in the CDP do not precisely meet the geographic and temporal boundaries
outlined for the CDP. Some data are from Europe, some from the United States, and some a
combination of both. The manufacturing data for this project were collected from companies in
the United States, Japan, and Korea (see Section 2.3), and the available upstream data may not
represent the exact location or type of processing represented in the upstream data inventories.
This is a limitation to using secondary data; however, the upstream data are only one portion of
the overall inventory of the product systems being evaluated, and the project partners chose to
focus on collecting primary data for the product manufacturing life-cycle stage, since those data
had not been previously compiled.
Another limitation of the upstream inventory data is the lack of transportation data for
some processes. These data become particularly important when, for example, raw materials are
uncommon and must be transported long distances for processing or when the particular transport
mode used for a particular material tends to have high environmental impacts. However, the
original data sources used in the Ecobilan inventories (see Table 2-9) are among the most used
LCI databases in the world (Ecobilan, 1999), which suggests the lack of transportation data for
upstream processes is not unique to the CDP LCI, but a common limitation of other LCIs as well.
2.2.3.2 Electricity generation data
The limitations to the electricity generation inventory data are provided in Appendix E,
Section 6. As another limitation, the Japanese grid was chosen when manufacturing data were
from more than one country. Appendix E also describes how the U.S. fuel-specific inventories
are applied to the Japanese grid, although technologies, efficiencies, etc. used in Japan are likely
to differ from those in the United States. Furthermore, U.S. fuel-specific inventories were
derived from secondary sources which did not necessarily meet our temporal boundaries, but did
meet geographic boundaries for the U.S. inventory.
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2.3 PRODUCT MANUFACTURING
2.3 PRODUCT MANUFACTURING
2.3.1 Methodology
2.3.1.1 Identification of processes and manufacturers
Through literature research and contacts with industry experts, the manufacturing
processes and the component parts of a CRT and an LCD computer monitor were identified. The
major manufacturing processes and components, in terms of resources used, and potential
importance to environmental impacts, were selected for inclusion in our primary data collection
effort.
Once the components and processes were chosen, companies who might supply
manufacturing data for the project needed to be identified. In order to identify those
manufacturers, the DfE project's Core and Technical Work Groups were consulted. These
groups consist of parties interested in the project results and willing to provide technical
assistance throughout the project, including identifying contacts in manufacturing facilities.
Manufacturing of CRTs, LCDs, and their component parts is done all over the world. Some
manufacturers are in the United States; however, most manufacturers of desktop computer
monitors and their components are in Asia. Where available, U.S. industry partners provided
contacts at U.S. as well as some Japanese manufacturing facilities and questionnaires were sent
to those contacts.
To assist in the collection of data in Asia, UT subcontracted with the Asian Technology
Information Program (ATIP) to identify company contacts, and to distribute and collect
questionnaires from Asian manufacturers. ATIP acted as a liaison between UT and Japanese and
Korean companies that participated in the study.
Participation in the study was completely voluntary. Companies were provided with the
goals of the study and the potential benefits of their participation. Once a company chose to
participate, they were sent data collection questionnaires to complete information about their
manufacturing process and to provide their inventory of process inputs and outputs. A copy of
the manufacturing data collection questionnaire that was developed for and used in this study is
provided in Appendix F.
The manufacturing processes for which primary data were collected are listed below. In
parenthesis are the number of individual data sets collected for each process:
CRT monitor:
• CRT monitor assembly (3)
• CRT (tube) manufacturing (3)
• CRT leaded glass manufacturing (3)
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2.3 PRODUCT MANUFACTURING
LCD monitor:
• LCD monitor assembly (2)
• LCD panel and module manufacturing (7)
• LCD glass manufacturing (I)2
• color filter patterning on front glass (1)
• liquid crystal manufacturing (2)
• polarizer manufacturing (1)
• backlight unit assembly (3)
• backlight light guide manufacturing (1)
• cold cathode fluorescent lamp (CCFL) manufacturing (1)
How these processes are linked to one another in the CRT and LCD life-cycles is presented in
Figures 2-2 and 2-3, respectively. The companies that provided data for the foregoing processes
are listed in Table 2-11.
Table 2-11. Companies that provided primary manufacturing data
for the CRT and/or LCD
Company
American Video Glass Company
T. Chatani and Co., Ltd.
Chisso Corporation
Eizo Nanao Corporation
Harison Electric Co., Ltd.
Hoshiden and Philips Display
Corporation
Hyundai Electronics Industries Co.,
Ltd.
liyama Electric Co., Ltd.
Matsushita Electric Industrial Co.,
Ltd.
Merck Japan Ltd.
Mitsubishi Electronic Co., Ltd.
Technology
CRT
LCD
LCD
CRT, LCD
LCD
LCD
LCD
CRT, LCD
LCD
LCD
LCD
Company
Nippon Denyo Co., Ltd.
Nippon Electric Glass Co., Ltd.
Polaroid Corporation
Samsung Electronics
Sharp Corporation
Sony Corporation (Japan)
Sony Electronics Inc. (U.S.)
Stanley Electric Co., Ltd.
Techneglas
Toppan Printing Co., Ltd.
Toshiba Display Technology Co., Ltd.
Technology
LCD
CRT
LCD
LCD
LCD
CRT
CRT
LCD
CRT
LCD
CRT, LCD
Another process that was included in the CRT manufacturing stage data was frit
manufacturing. We were not able to obtain primary data for this process; therefore, secondary
data were collected from EPA documentation and personal contacts (see Appendix G). An
inventory for printed wiring boards (PWBs) was also developed and included in the
manufacturing stage analysis. The PWB inventory is based on manufacturing of the electronic
boards, and does not include the components on the PWBs. The PWB data were obtained from
an industry representative who was able to provide general data not necessarily from one facility,
but from a combination of facilities, based on his experience (Sharp, 2000). More details about
PWB data collection are provided in Appendix G.
LCD glass manufacturing data were derived from the three sets of CRT leaded glass manufacturing data
(modified to remove lead from the inventory).
2^25
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2.3 PRODUCT MANUFACTURING
The manufacture of some components were not included in the scope of this study
because they were either deemed to be of less significance to the overall product inventories, or
data could not be obtained. However, all components were included as part of the final
assembled monitor even when individual manufacturing inventories were not. For the CRT, the
manufacture of the electron gun, deflection yoke, and phosphors were not included as separate
processes, and for the LCD, the transistor metals/materials, spacers, drivers/driver ICs, and color
filters were not included.
2.3.1.2 Data collection questionnaires
Data collection questionnaires were developed by the UT research team and approved by
the Technical Work Group to most efficiently collect inventory data needed for the LCA.
Appendix F provides a copy of the questionnaire given to product and component manufacturers.
The data that were collected include brief process descriptions; primary and ancillary material
inputs; utility inputs (e.g., electricity, fuels, water); air, water and waste outputs; product outputs;
and associated transportation. Quantities of inputs and outputs provided by companies were
converted to mass per unit of product. Transport of materials to and products or wastes from the
manufacturing facility were also reported. Details of the transportation analysis for this project
are presented in Section 2.6.
A total of 27 product manufacturing questionnaires were collected for 11 different
processes. The corresponding countries and the number of data sets from each country are listed
in Table 2-12.
Table 2-12. Location of companies and number of process data sets
Process
CRT monitor assembly
CRT (tube) manufacturing
CRT leaded glass manufacturing
CRT frit manufacturing
LCD monitor assembly
LCD panel and module manufacturing
LCD - glass manufacturing
LCD - color filter patterning on front glass
LCD - liquid crystal manufacturing
LCD - polarizer manufacturing
LCD - backlight unit assembly
LCD - backlight light guide manufacturing
LCD - cold cathode fluorescent lamp (CCFL) manufacturing
PWB manufacturing (for CRT and LCD monitors)
Country of origin of data
(# of data sets)
Japan (2), U.S. (1)
Japan (2), U.S. (1)
Japan (1), U.S. (2)
generic secondary data from the U.S.
Japan (2)
Japan (5), Korea (2)
Japan and U.S. (1)*
Japan (1)
Japan (2)
Japan (1)
Japan (3)
Japan (1)
Japan (1)
generic secondary data from the U.S.
! Average of three data sets for CRT leaded glass manufacturing modified to remove lead from the inventory.
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2.3 PRODUCT MANUFACTURING
2.3.1.3 Allocation
Data provided by manufacturers may need to be allocated to the products of interest (i.e.,
17" CRT or 15" LCD) in three situations:
• data are provided for more than the defined functional unit;
• data are provided on a rate basis instead of per functional unit (product); and
• data are provided for monitors/components of more than one size (i.e., not only 17" CRTs
or 15" LCDs).
In some cases, allocation was not required, as the inventory data collected were for one unit of
the product, defined as the functional unit. The three cases where allocation was necessary are
briefly described below.
In the first case, simple scaling was required when data were provided for all 17" CRT or
15" LCD monitors produced at a plant, as opposed to only one monitor. This simply requires
dividing the inventory mass by the number of monitors produced.
In the second case, data were provided over a certain amount of time. The inventory data
were then scaled to represent the functional unit. For example, if it was reported that x kilograms
of a material are used per year to produce one 17" or 15" monitor, and y number of products are
produced per year, then the amount of that material per functional unit is x/y.
In the third situation, allocation was also necessary for a company that manufactured
more than just the product or component of interest for this study. For example, a monitor
manufacturer may assemble various sized monitors, in addition to 15" LCDs or 17" CRTs.
Therefore it was necessary to allocate the process inventory to only our product of interest. We
used the difference in mass between the product of interest and other co-products and the
difference in the number of each product produced to allocate the inventory to the functional unit.
2.3.1.4 Aggregating manufacturing data
After one set of data from one company is allocated to one monitor, processes for which
we collected more than one company's data were averaged together. Once the inventory data for
a process were averaged, the electricity consumption from that process was linked to the
appropriate electric grid inventory (i.e., Japanese or U.S.). All the manufacturing processes were
linked to the Japanese grid, with the exception of frit and PWB manufacturing, both of which
were based on data collected in the United States. Where process data were represented by
companies in more than one country, the countries in which the majority of facilities were
located was used for the basis of which electric grid to use. An exception is the polarizer data,
which was from the United States, but the manufacturing was only a pilot plant and not
producing a product in the open market. Therefore, it was assumed that polarizer manufacturing,
as with most other LCD components, was done in Japan. Once each manufacturing process
inventory for each monitor type was complete (i.e., an averaged inventory with an associated
electric grid), each was aggregated with the rest of the manufacturing stage processes to comprise
the inventory for the manufacturing stage for a monitor. This manufacturing stage inventory was
then combined with the other life-cycle stages to represent the full LCI for each monitor type.
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2.3 PRODUCT MANUFACTURING
2.3.2 Data Sources and Data Quality
While manufacturers worldwide were offered the opportunity to participate in this
project, only manufacturing data from Japan, Korea, and the United States were collected. The
quality of the data can be evaluated against two factors: (1) the date of the data; and (2) the type
of data (i.e., measured, calculated or estimated). An understanding of how data were collected
and data verification steps should also be considered when evaluating the data quality. The data
collection phase of this project began in 1997 and extended through 2000. Some processes are
more sensitive to production dates than others. Most processes included in this analysis are
mature technologies and are not expected to differ significantly between the years 1997 and
2000. However, an exception is LCD panel manufacturing, which is an evolving and rapidly
advancing process and has seen changes between these years. The countries and dates from
which data for each process were obtained are presented in Table 2-13. For the LCD panel and
module manufacturing process, most data were from 1998 and 1999.
In the data collection questionnaires, companies identified whether the quantity of each
inventory item was a measured, calculated, or estimated value. These identifiers were referred to
as the "data quality indicator" (DQI) in the manufacturing questionnaire. The breakdown of
DQIs for the inventory items in the CRT and LCD processes are presented in Tables 2-14 and 2-
15, respectively. The last line in each table shows overall averages weighted by the number of
inventory items in each data set. For the CRT, 43% of the data were measured, 34% calculated,
13% estimated, and 10% were not classified. For the LCD, a similar distribution shows 33%
measured, 30% calculated, 23% estimated, and 14% not classified.
Table 2-13. Applicable years of primary data sets
Process
CRT monitor assembly
CRT (tube) manufacturing
CRT leaded glass manufacturing
LCD monitor assembly
LCD panel and module manufacturing
LCD - color filter patterning on front glass
LCD - glass manufacturing*
LCD - liquid crystal manufacturing
LCD - polarizer manufacturing
LCD - backlight unit assembly
LCD - backlight light guide manufacturing
LCD - cold cathode fluorescent lamp (CCFL)
manufacturing
# of data sets
o
J
•-)
J
3
2
7
1
1
2
1
3
1
1
Dates of inventory for each data set
1997, 1998-9, 1999
1997, 1998, 1998
1998, 2000, 2000
1998, 1999
1997-8, 1998, 1998, 1998-9, 1999, 1999,
1999-2000
1998
1998-2000
1998, 1998
1997
1998, 1999, 1999
1999
1998-9
! Primary data, but developed from the CRT glass manufacturing data.
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2.3 PRODUCT MANUFACTURING
Data quality can also be reviewed in terms of data collection methods. Much effort was
given to collecting primary data from manufacturers in this study. Questionnaires were sent out
and follow-up communication was conducted to verify data gaps or discrepancies. Twelve
companies were visited directly to clarify data and telephone or electronic communication
followed-up those and the remaining companies that were providing data for the study. Where
data could not be confirmed, additional literature research and discussions with other industry
experts were conducted.
Table 2-14. Data quality indicator percentages for the CRT processes
Process
CRT monitor assembly
Data set 1 (22 inventory items)
Data set 2 (1 1 inventory items)
Data set 3 (33 inventory items)
total inventory items = 66
CRT (tube) manufacturing
Data set 1 (69 inventory items)
Data set 2 (5 1 inventory items)
Data set 3 (83 inventory items)
total inventory items = 203
CRT leaded glass manufacturing
Data set 1 (43 inventory items)
Data set 2 (45 inventory items)
Data set 3 (2 inventory items)
total inventory items = 90
Overall weighted average for CRT
(359 items)
% of inventory items that are:
Measured
9%
9%
3%
wt. avg = 6%
91%
45%
21%
wt. avg = 51%
9%
91%
100%
wt. avg = 52%
43%
Calculated
64%
83%
0%
wt. avg = 35%
1%
55%
78%
wt. avg = 46%
3%
7%
0%
wt. avg = 5%
34%
Estimated
27%
0%
0%
wt. avg = 9%
4%
0%
1%
wt. avg = 2%
86%
0%
0%
wt. avg = 41%
13%
Not reported
0%
9%
97%
wt. avg = 50%
3%
0%
0%
wt. avg = 1%
2%
2%
0%
wt. avg = 2%
10%
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2.3 PRODUCT MANUFACTURING
Table 2-15. Data quality indicator percentages for the LCD processes
Process
LCD monitor assembly
Data set 1 (36 inventory items)
Data set 2 (10 inventory items)
total inventory items = 46
LCD panel and module manufacturing
Data set 1 (71 inventory items)
Data set 2 (39 inventory items)
Data set 3 (45 inventory items)
Data set 4 (139 inventory items)
Data set 5 (53 inventory items)
Data set 6 (86 inventory items)
Data set 7 (32 inventory items)
total inventory items = 465
LCD - glass manufacturing*
(83 inventory items)
LCD - color filter patterning on front glass
(29 inventory items)
LCD - liquid crystal manufacturing
Data set 1 (41 inventory items)
Data set 2 (6 inventory items)
total inventory items = 47
LCD - polarizer manufacturing
(30 inventory items)
LCD - backlight unit assembly
Data set 1 (20 inventory items)
Data set 2 (12 inventory items)
Data set 3 (12 inventory items)
total inventory items = 44
LCD - backlight light guide manufacturing
(5 inventory items)
LCD - cold cathode fluorescent lamp (CCFL)
manufacturing (36 inventory items)
Overall average for LCD (785 items)
% of inventory items that are:
Measured
5%
10%
wt. avg = 6%
80%
0%
40%
55%
43%
0%
0%
wt. avg = 3 7%
0%
97%
22%
0%
wt. avg = 19%
57%
0%
50%
0%
wt. avg = 14%
40%
58%
33%
Calculated
78%
80%
wt. avg = 78%
17%
100%
32%
38%
0%
0%
0%
wt. avg = 26%
0%
0%
64%
0%
wt. avg = 56%
17%
90%
0%
92%
wt. avg = 66%
40%
39%
30%
Estimated
17%
10%
wt. avg = 16%
0%
0%
17%
0%
36%
24%
97%
wt. avg = 17%
100%
3%
7%
0%
wt. avg = 6%
20%
0%
8%
8%
wt. avg = 4%
20%
0%
23%
Not reported
0%
0%
wt. avg = 0%
3%
0%
11%
7%
21%
76%
3%
wt. avg = 20%
0%
0%
7%
100%
wt. avg = 19%
6%
10%
42%
0%
wt. avg = 1 6%
0%
3%
14%
! Data based on CRT leaded glass manufacturing data.
2-30
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2.3 PRODUCT MANUFACTURING
2.3.3 Limitations and Uncertainties
The limitations and uncertainties associated with the manufacturing stage are related to
the following categories:
• the product system boundaries (scope),
• the data collection process, and
• the data.
Specific limitations/uncertainties for each of these categories are briefly described below.
2.3.3.1 Product system boundary uncertainties
The scope of the analysis included the major monitor components; however, it excluded
certain components, such as column and row driver ICs for the LCD and the electron gun for the
CRT. The components that were thought to possibly have an effect on the inventory were the
column and row drivers, as 1C manufacturing is known to be energy intensive and use various
process chemicals. Based on some back-of-the-envelope calculations, the exclusion of the
manufacturing of the column and row driver ICs is not expected to have a large impact on the
inventory or impact results due to the small size of the drivers. Therefore, it is assumed that the
exclusion of the column and row drivers will not have a significant impact on the study results.
The scope of the analysis in this study was also dependent on whether companies were
willing to provide data. LCD glass manufacturing data from a primary source are not included in
the inventory because no companies were willing to supply the data. For example, one
manufacturer chose not to provide data because LCD glass manufacturing technology is still
developing and is expected to improve from current low yields and high waste generation.
However, because glass is an important component by weight of the LCD, we chose to modify
the CRT glass manufacturing data to represent LCD glass manufacturing.
Both CRT and LCD glass are considered to be "specialty glasses" in the glass industry
and a limited number of companies produce these products. Consequently, there are limited
public data available on the production of these glasses. (One major difference between the CRT
glass and the LCD glass is that CRT glass contains lead oxide while LCD glass does not.)
Therefore, the primary data collected for this study for CRT glass manufacturing was modified
by removing inputs and outputs containing lead, and used to represent LCD glass manufacturing.
The remaining inputs and outputs were assumed to be the same per kilogram of glass produced.
Further research was conducted to confirm whether this was a valid assumption for the energy
used in production. Consultation with experts in the field revealed differing estimates between
energy used to produce a kilogram of CRT glass and a kilogram of LCD glass. Estimates ranged
from an equal amount of energy per kilogram for CRT and LCD glass production, to twice as
much energy per kilogram of LCD glass compared to CRT glass. With an assumption of equal
or greater energy use for the LCD (call that quantity of energy X), the proportion of that energy
(X) that is electrical energy and fuel energy was assumed to be the same as that given in the
primary data for CRT glass production (if the portion of energy X for the CRT was 30%
electrical and 70% fuel energy, those same proportions were used for the LCD's breakdown of
energy X).
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2.3 PRODUCT MANUFACTURING
Uncertainty in the differences between energy used for CRT versus LCD glass production
are related to production yield and melting point. The melting point of LCD glass is greater than
that of CRT glass; however, the difference in the production yield is uncertain compared to the
difference in melting point. The production yield for CRT and LCD depends on whether one
considers the surface area or the volume of the glass. LCD glass is a flat glass product and
excess glass is cut off the ends to obtain the final product. CRT glass manufacturing drops
molten glass into a mold and glass is not cut off of a flat piece of glass as in LCD production, but
excess glass may be produced during the molding process. Another factor in the difference in
energy used for CRT and LCD glass is that the LCD glass must meet high specification standards
for use as a substrate for the transistors to be patterned on the glass. Additional finishing steps
are required and the process is conducted in clean rooms (described in Section 1.3.3.2, LCD
manufacturing). The assumption that the same amount of energy is used for CRT glass and LCD
glass production takes into account each of these factors. The baseline analysis in this study
assumes the energy use per kilogram of LCD glass is equivalent to that of CRT glass. The
uncertainty associated with the glass manufacturing data is a limitation to the manufacturing
inventory data set. Additional limitations from the glass manufacturing data are discussed below
with other "data uncertainties" in Section 2.3.3.3.
2.3.3.2 Data collection process uncertainties
Limitations and uncertainties related to the data collection process include the fact that
companies were self-selected, which could lead to selection bias (e.g., those companies that are
more advanced in terms of environmental protection might be more willing to supply data than
those that are less progressive). Also, the data were supplied by companies whose vested interest
is to have their product look more desirable, which could result in biased data being provided.
However, multiple sets of data were obtained for this project, where possible, so that average
processes could be developed in an attempt to avoid biased data. The peer review process and
employment of the Core and Technical Work Groups as reviewers in this project is intended to
help reduce or identify any such bias. Further, several companies were visited and contacted for
verification of data.
Other data collection-process limitations resulted from the difficulty in obtaining and
verifying data over long distances (i.e., Japan and Korea to United States) as well as from the
language barrier. The use of ATIP as the Asian Liaison aided in reducing this limitation;
however, there were still language barriers that had to be overcome with ATIP, as well as
through direct communication with several companies.
2.3.3.3 Data uncertainties
Additional limitations to the manufacturing stage inventory are related to the data
themselves. Several attempts were made to verify or eliminate outliers in the data; however,
uncertainty in some data remained due to large data ranges and outliers. Specific data with the
greatest uncertainty include: (1) CRT glass manufacturing energy inputs (mentioned above in
Section 2.3.3.1); (2) the distribution of fuel/electricity inputs for LCD module manufacturing;
and (3) the use of a large amount of liquified natural gas (LNG) as an "ancillary material" and not
a fuel.
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2.3 PRODUCT MANUFACTURING
In addition to the uncertainty in the difference between energy used to manufacture CRT
glass and LCD glass, the energy reported to produce a kilogram of CRT glass varied greatly
between the data sets. Consultation with experts in the glass industry confirmed that the average
energy consumption derived from the primary data sets, although it appeared to be high, could be
possible. The total energy inputs per kilogram of glass from the primary data sets used in the
analysis, ranged over a factor of approximately 150 (i.e., the largest total energy value in the data
was about 150 times that of the smallest value). Due to this large discrepancy, the glass energy
data is the subject of sensitivity analyses in this study. The high energy use values were mostly a
function of liquified petroleum gas (LPG) used as a fuel.
Other data for which large ranges were found, and which could be important to the
results, are the energy use from LCD panel/module manufacturing. Energy data were provided
by six of the seven companies supplying LCD panel/module data. The percent of energy from
electricity ranged from approximately 3% to 87%. Three of the companies had the electrical
energy component contributing greater than 50% of the total energy use, and the other three
companies listed other fuels [e.g., LPG, LNG] as contributing greater than 50% to the total
energy use. Another large discrepancy was the total energy use for panel/module manufacturing.
Four of the six companies had energy use per panel between approximately 440 MJ/panel and
940 MJ/panel, while the two remaining companies had approximately 4,100 and 7,000 MJ/panel.
The average per panel was approximately 2,270 MJ/panel and the standard deviation was about
2,910 MJ/panel.
Given the wide variability in the data and large standard deviation, CDP researchers
evaluated the data for outliers by breaking the total energy data points into quartile ranges.
Minor outliers are then those within a certain range of multipliers beyond the middle 50% of the
distribution. That is, the interquartile range (IQR) (i.e., the range of values representing the
middle 50%) multiplied by 1.5 is the lower bound of the minor outlier and the IQR multiplied by
three is the upper bound. Anything beyond the IQR times three is a major outlier. Using this
approach, one data set was found to be a minor outlier and another was found to be a major
outlier. These outliers were excluded from the averages used in the baseline analysis, but
included in the averages used in a sensitivity analysis (see Section 2.7.3.3).
Finally, the average amount of LNG used as an ancillary material (not a fuel) in LCD
panel/module manufacturing was reported as 194 kg per functional unit. This data point
remained in the inventory data set for LCD manufacturing, and was assumed to indeed be an
ancillary material, and not a fuel. LNG was also reported as a fuel as a separate input
(approximately 3.22 kg/functional unit). Keeping the LNG ancillary material in the inventory
will not affect the energy impact results, since LNG used as an ancillary material is only linked to
the production of that material, and not to the use of it as a fuel. It will, however, affect upstream
impacts from the production of the material. Note that the natural gas process was used as a
surrogate for the production of LNG, as inventory data was not available for the latter.
2-33
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2.4 PRODUCT USE
2.4 PRODUCT USE
2.4.1 Methodology
The methods for developing the use stage inventory are presented in Appendix H and
summarized here. CRTs and LCDs use different mechanisms to produce images on screen,
which result in different energy use rates. These energy use rates (e.g., kW) can be combined
with the time a desktop monitor is on during its lifespan (hours/life) to calculate the total quantity
of electrical energy consumed during the use life-cycle stage (e.g., kWh/life). In this project, two
lifespan scenarios are considered:
• Effective life - the actual amount of time a monitor is used, by one or multiple users,
before it is disposed of, recycled, or re-manufactured. Reuse of a monitor by a
subsequent user is considered part of its effective life. Recycling, on the other hand, is
the reuse of parts or materials that require additional processing after disassembly, and it
is not considered part of the use stage.
• Manufactured life - the amount of time either an entire monitor or a single component
will last before reaching a point where the equipment no longer functions, independent of
user choices.
These two scenarios are considered in this project in order to account for potential
differences between how consumers currently use the equipment and how consumers could use
the equipment. Currently, consumers often replace monitors before they physically break down.
This behavior results in a lifespan that is not solely dependent on the monitor technology itself.
The manufactured life, on the other hand, is based on the technology and represents how
consumers could potentially use the equipment. If the lifespans are significantly different, the
difference could have a large impact on how the use stage compares to the other life-cycle stages
in this study. The baseline analyses in this project use the effective life scenario and the
manufactured life will be part of the sensitivity analyses.
2.4.1.1 Energy use rate
Most desktop monitors manufactured today are built to use several different power
consumption modes during normal operation. There are often up to four different power
consumption modes that can be used by a monitor in going from a state of active use to a state of
almost complete shut-down. These four modes, from greatest power consumption to least, are
typically entitled "full-on" or active use, "standby," "suspend," and "active-off." For this report,
manufacturers' data on these power modes were collected from company contacts and Internet
sites for 35 different 17" CRT monitors and 12 different 15" LCD monitors. The complete list of
these data is presented in Appendix H, Attachment A, Table Al.
For the purposes of this study, the power consumption modes have been categorized into
two modes: "full-on" and "low." The "low" power mode is an average of the three low power
modes typically provided by the manufacturers (i.e., standby, suspend, and active-off). These
three categories were averaged to create one "low" power consumption mode because hours per
use data (needed for calculations in this study) are only available for a "full-on" and a reduced
power mode. The low mode value for the CRT is the average of the three modal averages of
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2.4 PRODUCT USE
standby, suspend, and active-off. For the LCD, data on only two low-power modes (standby and
active-off) were provided by manufacturers (see Appendix H, Attachment A, Table A2), and
therefore, the low mode value is an average of those two modal averages. Table 2-16 presents
the average values for full-on and low power modes that were used for subsequent calculations in
this analysis.
Table 2-16. Average energy use rates a
Monitor type
17" CRT
15" LCD
Full-on power mode
[kilowatts (std. dev.)]
0.113 (0.015 SD)
0.040 (0.007 SD)
Low power mode b
[kilowatts (std. dev.)]
0.013 (0.005 SD)
0.006 (0.003 SD)
a See Appendix H, Attachment A, Table Al for source data.
b An average of company-reported values for standby, suspend and active-off (see Appendix H, Attachment A, Table Al).
Note: 1 kW = 1000 Watts = 1000 J/sec.
2.4.1.2 Effective life (baseline lifespan calculation)
The effective life scenario attempts to model the actual quantity of hours that an average
monitor spends in each of the two primary power consumption modes (full-on and a lower power
state) during its lifetime. The effective life of an average monitor is based on the following
information:
• the proportion of computers that are used in an office environment versus a home
environment, to account for different use rates in these two basic user environments;
• the amount of time in a year a typical monitor spends in full-on power mode and in a
lower power-consuming mode for both office and home environments; and
• the number of years a typical monitor is used during its lifespan for both office and home
environments, not including years in storage before a monitor is replaced or discarded (as
it is not consuming power during storage).
Under the effective life scenario, we assume there is no difference in the amount of time a
CRT or LCD monitor is operating. That is, the hours per life for the effective life calculation is
not technology-dependent. Therefore, the same set of hours-per-life values are used to calculate
the kWhs used per effective lifetime for a CRT and an LCD. The remainder of this section
discusses the data and methods used to calculate the hours-per-life values used in the effective
life scenario. More details are also provided in Appendix H.
Percentages of Office- and Home-Environment Users
Home and office users of computer equipment do not follow the same use patterns. Thus,
data are needed on the percent of users in each environment to determine the use pattern of an
"average" computer monitor. It is assumed that 65% of computers are in office environments
and 35% in home environments, based on data available through the Computer Industry Almanac
(CIA, 1997) and the Energy Information Administration (EIA, 1999b) (see Appendix H, Section
2.2.2.1 for more details).
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2.4 PRODUCT USE
Note that an "office" environment may be a school, hospital, or other commercial
environment, and the computers they use may follow widely varying degrees of use. For
example, computers (and thus monitors) in a school may only be used a few hours in a day, while
hospitals might operate theirs nearly constantly. For this study, it is assumed that on average,
typical office use patterns (to be presented below, and in Appendix H, Section 2.2.2.2) are
representative of all non-home environment users.
Operating Pattern (average hours in use per year)
In order to determine the amount of electricity consumed during a monitor's effective life,
we need to know the use operating patterns for both the office and home environments. The
"operating pattern" is defined here as the number of hours per year spent in each power mode.
The average number of hours per mode per year will be the weighted average of the two user
environments (i.e., 65% office, 35% home).
A literature search for computer monitor operating patterns was conducted for both office
and home environments and a summary of literature reviewed is presented in Appendix H,
Attachment A, Table A3. Based on the literature (Nordman et al, 1996, Fanara, 1999, EIA,
1999b) and other assumptions presented in Appendix H, Section 2.2.2.2, we assume the number
of hours per year that office and home monitors are used in each mode are as follows:
Office:
Full-on power mode: 1,095 hrs/yr
Low power mode: 2,263 hrs/yr
Total: 3,358 hrs/yr
• Home:
Full-on power mode: 522 hrs/hr
Low power mode: 793 hrs/yr
Total: 1,315 hrs/yr
Average Years Per Life
The number of years per life, multiplied by the operating patterns in hours per year (listed
above), will result in the hours per effective life. A monitor may be reused in multiple "lives"
before reaching its end-of-life. The end-of-life is defined as the point at which the monitor is no
longer used for its intended purpose in the physical form in which it was originally manufactured.
End-of-life options include indefinite storage (in which case it is not reused after storage),
de-manufacturing, recycling, or disposal. A monitor may be stored before being reused;
however, this storage time will not affect our use calculations since no electricity is required to
operate the monitor during this storage. After its first life as used by the original owner, a
monitor might be used by different people and with different PC systems in subsequent lives.
For data on the number of years of use that are in a monitor's lifetime, several sources of
information were reviewed (see Appendix H). Based on a recent study by the National Safety
Council (NSC, 1999), we assumed that a monitor is used for 4 years in its first life and 2.5 years
for its second or subsequent lives. The operating patterns (in hours/year) presented above are
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2.4 PRODUCT USE
assumed to be the same for all of the 6.5 years of the total effective life. However, in the lives
subsequent to the first life, the hours per year values are reduced by the fraction of monitors
assumed to be reused. Matthews et al. (1997) estimated that 45% of PCs are reused after a first
life; thus, the effective life operating pattern values in years of life after the first life are 45% of
the values in the first life.
Lifespan estimates from the National Safety Council (NSC, 1999) were specific to CRT
monitors; however, they were not specific to LCD desktop monitors. The NSC data did contain
estimates of a "Notebook PC," which were two to three years for the first life and one to two
years for the remaining lives; however, we expect that desktop LCD monitors will more closely
mirror the lifetime estimates of a desktop CRT monitor than that of a notebook PC.
Consequently, it was assumed that LCD desktop monitors also spend four years in their first life
and 2.5 years in their subsequent lives. Additionally, the NSC document did not attempt to
separate those computer systems or monitors that are used in an office versus a home
environment. Thus, it was assumed that the same years per life are realized for office and home
environments.
Effective Life Estimates (hours per life)
The data presented above are summarized in Table 2-17 and used to estimate the total
hours per effective life. The values for hours per year per power mode are assumed to be the
operating pattern throughout the first life (first four years). In the remaining lives, the annual
operating hours decrease to 45% of the hours in operation during each year in the first life, with
the remaining lives lasting a total of 2.5 years. Table 2-17 also presents the total hours per
effective life per mode, based on percentage in office and home environments. These values are
in bold in Table 2-17 (4,586 and 8,961 hrs per effective life) and will be multiplied by the energy
use rates per mode (presented in Table 2-16), to calculate the total energy consumption per
effective life for each monitor type.
Table 2-17. Effective life values
User
environment
Office
(65%)
Home
(35%)
Weighted
average c
Power
mode
Full-on
Low
Full-on
Low
Full-on
Low
First life
(4 years)
Operating
pattern (hr/yr)
1,095
2,263
523
793
—
—
Total
(hr/4 yrs)
4,380
9,052
2,092
3,172
—
—
Remaining lives
(2.5 years)
Operating
pattern (hr/yr) a
493
1,018
235
357
—
—
Total
(hrs/2.5 yrs)
1,233
2,545
588
893
—
—
Model totals b
(hr/effective life)
5,613
11,597
2,680
4,065
4,586
8,961
a The remaining lives operating pattern is 45% of first life operating pattern, based on 45% of monitors that are reused
(Matthews et al., 1997).
b Modal totals calculated as [(Total for first 4 years) + (Total for remaining 2.5 years)].
c The weighted averages shown for full-on and low power modes are based on the assumption that 65% of users operate in an
office environment and 35% operate in a home environment.
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2.4 PRODUCT USE
Effective Life Total Energy Consumption (kWh/life)
In order to calculate the total kWhs consumed, first, the energy use rates (kW) were
multiplied by the lifespans (hours per life) for each mode and each monitor type. They were then
summed for the two power modes to obtain a total kWh/life for each monitor type (Table 2-18).
Table 2-18. Effective life electricity consumption
Monitor
type
17" CRT
15" LCD
Power
mode
Full-on
Low
Total
Full-on
Low
Total
Energy use rate
(kW)
0.113
0.013
0.040
0.006
— -
EL calculated lifespan
(hours/life)
4,586
8,961
13,547
4,586
8,961
13,547
EL energy consumption
(kWh/life)
518
116
634
183
54
237
2.4.1.3 Manufactured life (alternative lifespan calculation)
Due to the uncertainty and assumptions associated with the effective life scenario, an
alternative scenario is also considered. The manufactured life is defined here as the length of
time a monitor is designed to operate effectively for the user. It is the number of hours a monitor
would function as manufactured, and is independent of user choices or actions. One way to
estimate this manufactured life is to use the mean-time-before-failure (MTBF) specification of a
monitor or its components. The CRT MTBF specification dictates the amount of time the
display must operate before it reaches its brightness "half-life," or the ability to produce 50% of
its initial, maximum brightness. The MTBF value, generally provided in total hours per life of a
monitor, is what most final manufacturers or assemblers of personal computer (PC) equipment,
including monitor assemblers, typically specify for a component. To meet the specification,
suppliers typically calculate the MTBF (a military-based specification) based on component data.
Suppliers' test results are usually called the "calculated" MTBF. The MTBF value also depends
on which combination of power modes are used during testing, which is referred to as the "duty
cycle" and each supplier may use a different duty cycle to test their component.
Additionally, monitor assemblers will often perform their own testing, typically entitled
"demonstrated" MTBF. The testing includes sequences where the monitor is "stressed" by
quickly switching back and forth from an all black picture to an all white one, or quickly
switching individual pixels either on and off or through multiple colors or black and white.
Manufacturers typically find that their demonstrated MTBF is on the order of twice as long as the
calculated MTBF (McConnaughey, 1999; Douglas, 1999). However, it should be noted that the
demonstrated MTBF is not a real-time testing method, as the testing data is used in a complex
equation to calculate that "demonstrated" value.
From review of the information obtained on CRT-based monitors (see Appendix H,
Attachment A, Table A2), it appears that the CRT (the tube) itself is the limiting component, or
the component that 99% of the time determines whether the entire monitor has reached its
end-of-life. Thus, from the limited information that was obtained on CRTs, and the limited
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2.4 PRODUCT USE
confidence that can be instilled in those data, an average of the two ranges obtained on the
estimated lifetime of CRTs (10,000 and 15,000 hours) was used as the CRT manufactured
lifetime (12,500 hours) (Goldwassar, 1999; Douglas, 1999).
For active matrix LCDs, the components that have the greatest potential to fail first are
the display panel itself (including the liquid crystals and thin-film transistors), backlights, driver
integrated circuit (1C) tabs, and other smaller components. The backlights and driver 1C tabs can
be field-replaced, thus their failure does not necessarily represent the end of the monitor's life.
However, failure of the liquid crystals or transistors, which would require replacement of the
display panel itself, would most likely mean that the monitor cannot be cost-effectively repaired.
The MTBFs of all these components appear to have a broad range. For example, different
backlight manufacturers reported from as few as 15,000 hours to as many as 50,000 hours
(Douglas, 1999; Tsuda, 1999; VP150, 1999). However, it appears that those components that are
not field-replaceable (e.g., the LCD panel) have MTBFs in the range of 40,000 to 50,000 hours
(Tsuda, 1999; Young, 1999). Thus in this study, the amount of time an LCD monitor would
operate during its manufactured life is assumed to be the average of the two non field-replaceable
values, or 45,000 hours. In order for a monitor to operate for 45,000 hours, any major
field-replaceable parts that have MTBFs less than 45,000 hours will need to be accounted for in
this LCA project. For example, assuming the backlights last on average 32,500 hours (the
average of the values obtained for backlights), more than one (approximately 1.4, on average)
would be needed for every panel during its lifetime. Therefore, in the final CDP LCA, the
manufacturing of extra backlights would need to be included in the inventory.
Little information is available on the duty cycles that component manufacturers use to test
components. Thus, it is assumed that the average duty cycle used in testing components is 50%
of the time tested in full-on mode and 50% in a lower power mode. Table 2-19 shows the values
that are used in this study for the hours per manufactured life for the CRT and LCD. Some
sensitivity analyses were done and presented in Socolof et al (2000).
Table 2-19. Manufactured life values
Monitor
type
17" CRT
15" LCD
Total hours
(hours/life)
12,500
45,000
Mode
Full-on
Low
Full-on
Low
Duty cycle
(% time spent in each mode during testing)
50%
50%
50%
50%
Hours per mode
(hours/life)
6,250
6,250
22,500
22,500
To calculate the manufactured life electricity consumption (kWh/life), the energy use rate
(kW) is multiplied by the lifespan (hours/life) for each monitor in each power mode (Table 2-20).
The LCD manufactured life (45,000 hours) is 3.6 times greater than the CRT manufactured life
(12,500 hours). In an LCA, comparisons are made based on functional equivalency. Therefore,
if one monitor will operate for a longer period of time than another, impacts should be based on
an equivalent use. Therefore, based on equivalent use periods, 3.6 CRTs would need to be
manufactured for every LCD. This will be incorporated into the profile analysis for the
comparative manufactured life LCA.
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2.4 PRODUCT USE
Table 2-20. Manufactured life electricity consumption
Monitor
type
17" CRT
15" LCD
Power
mode
Full-on
Low
Total
Full-on
Low
Total
Energy use rate
(kW)
0.113
0.013
—
0.040
0.006
ML calculated lifespan
(hours/life)
6,250
6,250
12,500
22,500
22,500
45,000
ML energy consumption
(kWh/life)
706
81
787
900
135
1,035
2.4.1.4 Effective life versus manufactured life
For the CRT monitor, the effective life total hours are 13,547 versus the manufactured
life total of 12,500. While this suggests that a CRT can be used longer than is physically
possible, it simply reveals our low confidence in these numbers and some of their supporting
values, with less confidence in the manufactured life data than the effective life estimates. A
more complete discussion of the data quality is presented in Section 2.4.2 and Appendix H.
Assumptions were required several times that could bias these numbers in either
direction; however, it is thought that the manufactured life estimate is most likely low based on
the other estimates for the overall CRT monitor (see Appendix H, Attachment A, Table A2).
However, there was no sound basis for assuming a lower value and thus the above hours per life
values were used. It should also be stated that while these numbers are different, they are within
an 8% error range of one another, and can be taken to be a near 1:1 ratio, indicating a similar
potential lifespan.
For LCDs, the comparison across lifespan scenarios is more consistent with what one
would expect, with the manufactured life value of 45,000 hours per life being much greater than
the effective life value of 13,547 hours per life. The effective life value reflects the assumption
that a user's use habits are not technology-dependent, and would seem to reveal that LCDs are
not being used as long as they can physically be (less than a third as long).
The difference between the effective and manufactured lives are important when
evaluating all the life-cycle stages for a particular monitor type. If the manufactured life is
significantly greater than the effective life, the use stage will have greater impacts, as compared
to other life-cycle stages. Therefore, it is important to focus on the lifetime scenario that is most
realistic, while still recognizing the potential impacts from another feasible lifespan scenario.
In this project, we will use the effective life as the primary basis for the use stage
inventory due to the fact that the effective life data are attempting to obtain a more realistic value
for electricity consumed per lifetime, and that we currently have greater confidence in those data
versus the manufactured life data. The manufactured life data will be used in one sense as a
sensitivity analysis and to discuss potential differences in the use stage impacts based on this
alternative lifetime scenario.
2-40
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2.4 PRODUCT USE
2.4.2 Data Sources and Data Quality
Source and quality information for the use stage data are detailed in Appendix H,
Table 11. We assigned four categories of data quality ratings: excellent, average, poor, and
unknown. In general, data assigned higher quality ratings were directly measured and represent
1998 data. As data required more calculation or estimation, or were found from a previous year,
the data quality rating was reduced.
The overall level of use stage data quality is between average and excellent (Appendix H,
Table 11). However, a distinct difference can be seen in the average data quality ratings given to
manufactured life data (average) and the effective life data (excellent). This implies that greater
confidence can be placed in the effective life data than in the manufactured life data.
Additionally, the energy use rate data appears to be of average quality.
2.4.3 Limitations and Uncertainties
Details of the limitations and uncertainties associated with the energy use rate, the
effective life, and the manufactured life estimates are presented in Appendix H, Section 5.
2-41
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2.5 END-OF-LIFE
2.5 END-OF-LIFE
2.5.1 Methodology
A Technical Memorandum, attached as Appendix I, was prepared for this project that
provides background on the EOL issues for the CRT and LCD. It also provides details on the
methodology used in this project for the EOL life-cycle inventory. This section summarizes the
salient points from that memorandum needed to understand the EOL methodology and results.
For the EOL analysis, a monitor is assumed to have reached EOL status when:
• it has served its useful life;
• is no longer functional; and/or
• is rendered unusable due to technological obsolescence.
Each of these situations is addressed by either the manufactured or effective lives (defined in
Section 2.4).
2.5.1.1 EOL disposition options
The major EOL dispositions considered in this analysis are as follows:
• recycling - including disassembly and materials recovery;
• landfilling - including hazardous (Subtitle C) and non-hazardous (Subtitle D) landfills;
• remanufacturing - including refurbishing or reconditioning (to make usable again); and
• incineration - waste to energy incineration.
See Appendix I for further descriptions of these dispositions. Note that reuse is considered part
of the use stage and not included as an EOL disposition.
The functional unit in this analysis is one monitor; therefore, the different EOL
dispositions were allocated as a probability of one monitor going to a certain EOL disposition.
Data were somewhat scarce on the percent of monitors going to each disposition, especially for
the LCD monitors. After literature research and consultation with the project's Technical Work
Group, as well as various other industry experts, project partners chose best estimates of
disposition distributions. Table 2-21 presents the assumptions used for the EOL life-cycle stage
dispositions for the CRT and LCD, respectively. An explanation of the assumptions and the
sources of the data are presented in Appendix I.
The values in Table 2-21 have been used in the baseline scenarios for the CRT and LCD
LCIs. To address the uncertainty in the LCD estimates, a sensitivity analysis was conducted
(which is discussed in Section 2.7.3).
2-42
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2.5 END-OF-LIFE
Table 2-21. Distribution of EOL disposition assumptions for the CRT and LCD
Disposition
Incineration
Recycling
Remanufacturing
Hazardous waste landfill
Solid waste landfill
CRT
15%
11%
3%
46%
25%
LCD
15%
15%
15%
5%
50%
Sources: NSC, 1999; EPA, 1998; Vorhees, 2000; CIA, 1997; EIA, 1999b
2.5.1.2 Data collection
Inventory data were needed for each of the EOL dispositions to be included in the life-
cycle profiles. Primary data were collected for CRT recycling from three companies.
Hazardous/solid waste landfilling and incineration were developed from secondary data obtained
from Ecobilan. In attempts made to obtain remanufacturing data, it was found that
remanufacturing processes span a wide range of activities, from as little as replacing button tops
to as extensive as testing and replacing PWBs or transformers. Given the broad range of
possibilities, no single set of operations could be identified to adequately represent
remanufacturing activities that could be incorporated in our model. Remanufacturing data were,
therefore, excluded from the assessment.
Recycling
Companies willing to provide CRT recycling data were given EOL questionnaires, which
are similar to the manufacturing questionnaires, but modified as appropriate for the EOL life-
cycle stage (see Appendix I). The questionnaires were used as a guide for collecting inventory
data. The companies agreed to provide inventory data through personal meetings and telephone
conversations rather than completing the detailed questionnaire. As a result, the most critical
data were identified by the research team to prioritize data needs, and all the details in the
questionnaire may not have been provided.
The three companies contacted were: (1) DMC Recycling; (2) A & B Recycling; and (3)
The Oak Ridge National Recycle Center (TORNRC). DMC shreds the complete monitor up and
separates the recovered materials into three major material streams: ferrous, silica-based, and
copper-based. The ferrous metals are sent to steel mills for recycling, while the other streams are
sent to lead and copper smelters, respectively. A & B Recycling performs a partial disassembly
of the casing and other materials outside the CRT. These materials (namely, HIPS, steel,
aluminum, and copper wiring) are sent for recycling, while the CRT itself is shipped to
Envirocycle (a CRT recycler in Pennsylvania), where the glass is recovered and sent for recycling
back into CRT glass, and the other materials are also recovered for recycling. TORNRC
conducts complete monitor disassembly (which includes the CRT recycling process similar to the
one performed at Envirocycle), and recovers the individual materials for subsequent recycling.
None of the recycling companies contacted have yet encountered end-of-life LCDs in any
appreciable quantities that would justify the development of a separate recycling process for
them. Whatever sporadic quantities of LCDs that they do receive (mainly notebook computer
2^43
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2.5 END-OF-LIFE
displays) are either sent for refurbishing/resale or are processed along with other electronic
equipment, by recovering different materials from them, such as metals, glass, plastics, etc. In
the absence of actual data for LCD recycling, the shredding-and-materials-recovery process
followed by DMC Recycling for CRTs was assumed to be suitable for recovering materials from
LCDs as well, and was therefore used to model LCD recycling.
Landfilling and Incineration
Generic secondary data were used for the incineration and landfilling processes because
when monitors are disposed of, they are combined with multiple waste streams, and data for
monitors alone are not readily available. Although data specific to landfilling and incineration
operations for monitors alone were not available, DEAM inventories from Ecobilan were
available for landfilling and incinerating the following major monitor materials (by weight):
steel, glass, plastic, and aluminum. These inventories were combined, based on the approximate
proportion of each material in a CRT and an LCD, to create individual processes for landfilling
and for incineration (for each monitor type). The proportions of these materials in a CRT and an
LCD, presented in Table 2-22, are estimates of the final assembled monitor based on the
manufacturing inventory data. Note that these proportions are slightly different from the
proportion of total inputs per functional unit presented in Section 2.1.2, Tables 2-2 and 2-3
because materials efficiency during production is not accounted for here (in Table 2-22). The
majority of the assembled monitors by weight is accounted for in the overall incineration and
landfilling processes, as seen in the totals in Table 2-22.
It should be noted that some of the DEAM inventories associated with incineration or
landfilling are for generic materials (i.e., glass, plastic), and may not accurately represent the
makeup of the material used in the monitors. For example, the glass is not leaded glass, and the
plastics may not represent the exact breakdown of plastics in the monitors being modeled in this
study (see Section 2.5.3, Limitations and Uncertainties for further discussion).
Table 2-22. Percent contribution of major materials in the final
product
Material
Glass
Steel
Plastic
Aluminum
Total
CRT
43% (9.48 kg)
30% (6.61 kg)
17% (3. 75 kg)
2% (0.44 1kg)
92% (22.043 kg)
LCD
9% (0.585 kg)
47% (3.055 kg)
40% (2.60 kg)
1% (0.065 kg)
97% (6.5 kg)
2.5.1.3 Assumptions
The assumptions used in the EOL life-cycle stage include the percentage breakdown of
each EOL disposition option (see Table 2-21), the breakdown of materials for the incineration
and landfilling inventories (Table 2-22), as well as those listed in Section 2.2 of Appendix I.
2-44
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2.5 END-OF-LIFE
2.5.2 Data Sources and Data Quality
Primary CRT recycling data collected were collected from three companies: A & B
Recycling, DMC Recycling, and TORNRC. Efforts were made to collect all data in the
questionnaires; however, priority was given to obtaining the inventory data. The companies,
preferring to provide data over the phone or during personal meetings, were able to provide the
inventory data required for the analyses in this study.
Specific DQIs, such as those reported for the manufacturing data (see Section 2.3.2,
Tables 2-14 and 2-15), were not obtained. The data from these companies represent facility
operations ranging from October 1999 to February 2000. Also, while the data obtained are from
three recycling facilities that may have different operations, the averaged inventory data are
intended to be representative of various recycling activities in the industry.
Data for the EOL life-cycle stage are a combination of primary data, for which we do not
have specific DQI, and secondary data, with limited data quality information. The overall data
quality for this life-cycle stage may therefore be limited, and in relative terms, is lower quality
than the manufacturing stage data.
Sources of data for EOL distribution assumptions include the National Safety Council
(NSC, 1999), EPA (1998), CIA (1997), EIA (1999b) and Vorhees (2000). These are discussed in
Appendix I.
2.5.3 Limitations and Uncertainties
Assumptions of the disposition percentages for CRTs and LCDs may not be truly
representative of actual dispositions. Recycling technologies are not yet standardized for the
sorting, separation, and processing of different types of CRT glass, metals, and plastics. The
methods currently employed by a few large-volume recyclers who have been in the CRT
recycling business for some years were used in this study and represent "state-of-the-art" in the
CRT recycling industry. The LCD recycling process used was based on a CRT recycling process
employed by one of the recycling companies contacted, as it was considered general enough to be
applicable to LCDs. In the future, when greater numbers of LCDs begin to arrive at recycling
facilities, more standardized processes for handling LCDs specifically might be developed.
Limitations for the incineration and landfilling inventories are that incineration and
landfilling of the materials were for generic materials and not specific to actually incinerating or
landfilling a CRT or LCD monitor. For the CRT, the glass incineration portion of the monitor is
for generic, non-leaded glass. The plastics are also generic plastics (mainly those used for
packaging that ultimately end up in municipal solid waste, such as HOPE, LDPE, and PET) and
may not account for the flame retardants that might be in the plastics, for example. Also, only a
few of the major materials by weight are included in the modeled CRT and LCD that are
incinerated (listed in Table 2-22).
2-45
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2.6 TRANSPORTATION
2.6 TRANSPORTATION
2.6.1 Methodology
Transportation of materials, products, and wastes throughout a product's life-cycle has
environmental impacts and should be included in a comprehensive LCA. However, complete
transportation data for all life-cycle stages is often difficult to obtain. Only six of the 16
upstream data sets used for this study explicitly stated that transportation was included. An
additional six upstream processes are assumed to have considered transportation (Table 2-9). In
the manufacturing stage, transportation data were collected in the questionnaires that were
distributed to manufacturers. Some transportation data were provided by manufacturers on
materials received by their facility and products and wastes shipped from their facility. Data
were not obtained on transportation during the use stage because distributing questionnaires and
collecting primary data for the use stage were not within the boundaries and scope of the LCA.
Consequently, individual consumer transport to pick up purchased monitors and to send to a
secondary user or to a recycling/disposal facility were not accounted for. Similarly, EOL data,
either from CRT recyclers, or secondary data for incineration and recycling did not include
transportation data. Therefore, the transportation data collected in this study may only represent
a small portion of the overall transport in the life of a monitor.
The manufacturing data collection questionnaires (Appendix F) provided space for
companies to identify transportation information for each material input, product output, or waste
output. The questionnaire asked for the distance traveled, mode of transport (i.e., vehicle type),
number of trips per year, and percent capacity of the vehicle containing a particular material of
interest. Given this information, the project researchers calculated the total distance traveled for
a transportation mode per functional unit.
In order to determine the environmental effects of transport, the total distance traveled
must be linked to an inventory associated with a transport mode on a per-distance-traveled basis.
Ecobilan 's DEAM data provided inventories for several vehicles either on a per-distance-
traveled basis or a per mass-load, per-distance-traveled basis. Given the maximum load of the
vehicle, the latter figures can also be used with the transportation data collected in the
manufacturing questionnaires to estimate the total distance traveled per mode per functional unit.
2.6.2 Questionnaire Results
In many cases, companies completing the questionnaires provided partial transportation
data. For the CRT processes, manufacturers supplied adequate transportation data for 66% of the
materials that are expected to have transportation data. For the LCD processes, 73% of the
materials had adequate transportation data to determine the total distance traveled per mode per
functional unit. Of the transportation data that were provided, Table 2-23 lists the distribution of
transport modes for the CRT and LCD manufacturers. To complete the LCI, transport data from
the questionnaires would have to be linked to vehicle inventories, which were available through
the DEAM data. However, the vehicle inventories were not linked to the questionnaire data
because the questionnaire asked for percent capacity, but did not couple that with the load
capacity of the vehicle. As a result, the data were inconsistent and could not accurately be used
in the overall product LCI.
2-46
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2.6 TRANSPORTATION
Table 2-23. Distribution of transport modes and total distances per mode
Transport mode
Large diesel truck
Small diesel or gas truck
Ocean
Rail
Air
Total
CRT
Distribution
of modes
61%
21%
16%
2%
0%
100%
Approx. normalized a
distance traveled per
functional unit
3km
<1 km
37km
<1 km
0
40km
LCD
Distribution
of modes
58%
35%
3%
2%
2%
100%
Approx. normalized*
distance traveled per
functional unit
3km
<1 km
<1 km
<1 km
52km
56km
a Normalized by the percent capacity of a vehicle carrying the material of interest.
Note: 1 km = 0.6215 miles.
In order to use the vehicle inventory data, it would have to be assumed that the load
capacity assumed by manufacturers when providing the percent capacity was consistent with that
in the DEAM vehicle inventory data. However, conducting a review of the DEAM data versus
the questionnaire data showed that this was not consistent. The greatest difference (based on
relatively crude averages of all the transport data provided) appeared to be for the ocean
transport, where the discrepancy was on the order of tens of millions of times different. The
other modes appeared to be between 22,000 to 660,000 times. These huge discrepancies puts the
linked transportation data into question, making it unreliable for use in this study. When the
transportation impacts were run in the analysis, and these factors applied, the transportation
impacts appeared to be small compared to the other life-cycle stages, but no real reliable
information can be gleaned from these data. Further work is needed in this area to understand
the true transportation impacts. For this report, the transportation-related inventories are not
included.
Transportation data that can be used from the questionnaires include the modes of
transport used and the total distances traveled per functional unit (by mode). These are presented
in Table 2-23. The "normalized" distance is the total distance traveled for each material
multiplied by the percent capacity of the vehicle that was carrying the particular material of
interest. This was done to allocate a portion of the vehicle (and thus a portion of the associated
inputs and outputs for transport in a particular vehicle) to the transport of the material of interest.
It should be noted that these percent capacities were assumptions made by the manufacturers who
completed the questionnaires and the percent capacity assumptions could have been
inconsistently interpreted. Not only are the distances modified to represent only the product of
interest, they are scaled to represent one functional unit (i.e., the material, product, or waste
associated with one monitor). Thus, the total normalized distance for the CRT is 40 kilometers
(km) per functional unit and 56 km per functional unit for the LCD. These numbers are
normalized with the intention of linking them to the individual vehicle inventories, but as stated
above, this has not been done due to data inconsistencies.
The most frequently used mode of transport for both the CRT and LCD is the large diesel
truck, followed by the small gas or diesel truck. However, the largest normalized distance
traveled for the CRT is via ocean transport and for the LCD is via air transport. Worth noting
again is that these distances were calculated by normalizing the capacity of the vehicle, as
assumed by the manufacturer. Although the transport data represent transport of several
2-47
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2.6 TRANSPORTATION
materials, products, and wastes into and out of manufacturing facilities, the majority of the
distances traveled are from the transport of the final assembled monitors. Of all the reported
transportation for the manufacturing stage, the distance traveled of a final assembled CRT
monitor via the ocean represents 80% of the total distance traveled. For the LCD, 90% of all
reported kilometers traveled are for transport of the final assembled LCD monitor via airplane.
Transport of the final assembled CRT monitor for all transport modes is 86% of all kilometers
traveled per functional unit. Similarly, for the final assembled LCD monitor, approximately 92%
of all manufacturing transportation reported is for the final assembled monitor.
2.6.3 Data Sources and Data Quality
Primary data were derived from manufacturing questionnaires and inventory data for
transport vehicles were available through DEAM data. However, inconsistencies between the
data made it impossible to accurately apply the DEAM inventories to the questionnaire data.
Therefore, the data quality is very low and complete transportation inventory data are excluded
from the analysis results.
2.6.4 Limitations and Uncertainties
Inconsistencies between data collected in questionnaires and DEAM data made it
impossible to use the transportation inventory data as part of the overall life-cycle. From rough
estimates based on data received, it is possible that the transportation impacts are not driving
overall life-cycle impacts, however, this would need to be investigated further to confirm such a
conclusion.
2-48
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2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
2.7.1 Baseline LCI
This section presents the baseline inventory data for the life-cycles of the CRT and LCD
monitors. The baseline scenario meets the following conditions:
• uses the effective life use stage scenario;
• uses the average value of all the energy inputs from the primary data for glass
manufacturing;
• assumes LCD glass manufacturing processes use the same amounts of energy as CRT
glass manufacturing per kilogram of glass produced;
• excludes two outliers from the average of the energy inputs in the LCD panel/module
manufacturing inventory;
• excludes transportation in the manufacturing stage, but includes any transportation
embedded in upstream data sets; and,
• includes the manufacturing process of materials used as fuels (e.g., natural gas, fuel oils)
in the life-cycle stage in which they are consumed instead of in the materials processing
stage. In cases where materials normally considered to be fuels are used as ancillary
materials their manufacturing processes are included with other upstream processes.
Inventory data presented here are used to calculate impacts in the impact assessment (Chapter 3),
which translates inventory items into impacts. Note that only limited conclusions can be made
based on the inventory alone.
Table 2-24 presents the total quantity of inputs and outputs for the entire life-cycles of the
CRT and LCD based on input and output types. Definitions of the input and output types were
presented in Table 2-1 in Section 2.1.1. Graphs depicting selected input and output types,
derived from the values in Table 2-24, are in Figures 2-5, 2-6, and 2-7. Complete inventory
tables for each input and output type by life-cycle stage for the CRT and LCD are provided in
Appendix J. The inventories presented in Appendix J list each individual input or output
alphabetically for a particular input or output type. The individual inputs or outputs may be the
sum of that material for several processes.
The total inventory results for life-cycle inputs reveal that more primary materials,3 water,
fuels, electricity, and total energy (i.e., fuel energy plus electricity) are used throughout the CRT
life-cycle while more ancillary materials are used throughout the LCD life-cycle. For the life-
cycle outputs, the CRT releases more air emissions; water pollutants; hazardous, solid, and
radioactive waste; and radioactivity than the LCD. The LCD releases more total wastewater than
the CRT. The data that comprise the inventory totals presented in Table 2-24 are listed in
Appendix J and broken down by life-cycle stage. Further details on the inventory are provided
for each monitor type below.
Note that the total mass of primary materials includes the inputs to each process, which may duplicate
materials used in processes subsequent to other processes. For example, the primary materials used in steel
production are added to the steel used as a primary material for monitor assembly.
2^49
-------
2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
Table 2-24. Total life-cycle inventory summary - baseline analysis
Inputs
Primary materials
Ancillary materials
Water
Fuels
Electricity
Total energy
CRT
6.53e+02
1.98e+01
1.31e+04
4.33e+02
2.49e+03
2.08e+04
LCD
3.63e+02
2.08e+02
2.82e+03
3.86e+01
1.20e+03
2.84e+03
Units
kg/functional unit
kg/functional unit
kg (or L)/functional unit
kg/functional unit
MJ*/functional unit
MJ*/functional unit
Outputs
Air pollutants
Wastewater
Water pollutants
Hazardous waste
Solid waste
Radioactive waste
Radioactivity
6.64e+02
1.52E+03
2.09E+01
9.46e+00
1.72e+02
2.90e-03
8.98e+07
3.46e+02
3.13e+03
1.68e+00
6.29e+00
5.23e+01
1.48e-03
4.01e+07
kg/functional unit
kg (or L)/fiinctional unit
kg/functional unit
kg/functional unit
kg/functional unit
kg/functional unit
Bq/functional unit
*3.6MJ=lkWh
Note: Bold indicates the larger value when comparing the CRT and LCD.
15000-,
3 10000-
«
c
= 5000 -
o
c
•3 n
653
0) °^~
"*
Material Inputs
• Primary materials nAncillary materials n Water • Fuels
13,100
20
2,820
433 363 208 | 1 39
1 '
CRT LCD
figure 2-5. Mass-based life-cycle inputs
2-50
-------
2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
^ 25000 -,
f 20000 -
| 15000 -
tj 10000 -
| 5000 -
i 0
_L
2,490
Energy Inputs
20,800
D Electricity n Total energy
1,200 2'840
CRT LCD
Figure 2-6. Energy-based life-cycle inputs
Material Outputs
D Air pollutants n Water pollutants Q Hazardous waste n Solid waste • Radioactive waste
(functional unit
N> -t*. O5 00
O O O O
3 O O O O
2 ^
664
346
172
1 21 9.5 0.0029 1 1.7 6.3 52 0.0015
CRT LCD
Figure 2-7. Mass-based life-cycle outputs
(excluding total wastewater)
2-51
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2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
2.7.1.1 CRT inventory results
The total CRT inventory presented in Table 2-24 and Figures 2-5, 2-6, and 2-7 show the
inventory from all life-cycle stages combined. The totals by life-cycle stage are presented in Table
2-25, Figures 2-8, 2-9, and 2-10.
Table 2-25. CRT inventory by life-cycle stage
Inventory type
Upstream
Mfg
Use
EOL
Total
Units a
Inputs
Primary materials
Ancillary materials
Water
Fuels
Electricity
Total energy
1.58e+01
2.11e+00
5.54e+02
??
7.32e+01
3.66e+02
4.21e+02
3.54e+00
1.14e+04
??
1.29e+02
1.83e+04
2.19e+02
3.47e+00
1.14e+03
??
2.29e+03
2.29e+03
-3.32e+00
1.07e+01
-2.73e+01
??
2.29e-01
-1.28e+02
6.53e+02
1.98e+01
1.31e+04
O.OOe+00
2.49e+03
2.08e+04
kg
kg
kg (or L)
kg
MJ
MJ
Outputs
Air pollutants
Wastewater
Water pollutants
Hazardous waste
Solid waste
Radioactive waste
Radioactivity
3.00e+01
1.70e+01
8.12e-01
??
9.55e+00
4.39e-04
3.80e+07
1.83e+02
1.51e+03
2.01e+01
??
8.12e+01
1.80e-04
3.78e+06
4.49e+02
0
7.02e-02
0
8.33e+01
2.28e-03
4.80e+07
2.47e+00
-3.65e+00
-6.18e-02
??
-1.66e+00
2.29e-07
4.80e+03
6.64e+02
1.52e+03
2.09e+01
9.46e+00
1.72e+02
2.90e-03
8.98e+07
kg
kg (or L)
kg
kg
kg
kg
Bq
a Per functional unit (i.e., one CRT monitor over its effective life).
2-52
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2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
CRT Material
Inputs
n Primary materials nAncillary materials o Water n Fuels
15000-1
§ 10000-
15
o 5000 •
4J
o
c n
=
•* -5000 •
1
16 21554 8 421 4
1,4C
0
1,140
428 219 3 5 Q „ _27
1 -3.3 -3.U'
Upstream Mfg Use EOL
Life-cycle stage
Figure 2-8. CRT Mass-based material inputs by life-cycle stage
« 20000 -,
= 15000 -
= 10000 -
3
*i—
T
5000 -
0
-5000 -I
CRT Energy Inputs
18,300
Electricity n Total energy*
73 366 129
2,290 2,290 -128
023
I I I
Upstream Mfg Use EOL
Life-cycle stage
'Total energy is the sum of electricity and fuel energy
Figure 2-9. CRT Energy-based inputs by life-cycle stage
CRT Outputs
I Air pollutants n Water pollutants Q Hazardous w aste Q Solid w aste Q Radioactive w aste
449
2.3E-07
3.070 2.3E-03 2.5,^,8.3-1.7
Mfg Use
Life-cycle stage
EOL
Figure 2-10. CRT mass-based outputs by life-cycle stage
2-53
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2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
Considering inputs, Figure 2-8 shows that of the inputs measured in mass, the water inputs
in the manufacturing life-cycle stage constitute the majority of the inputs by mass for the entire life
cycle. Water inputs from the LPG production process constitute almost 80% of the water inputs for
all life-cycle stages. In this inventory, the LPG is used in large quantities as a fuel in CRT glass
manufacturing. When considering which life-cycle stage contributes most to an inventory category,
the manufacturing stage has the largest inventory by mass for primary materials, ancillary materials,
water inputs, and fuel inputs. This is also due to the production of LPG as needed for CRT glass
production. Fuel inputs are dominated by the manufacturing stage and electricity inputs are
dominated by the use stage. The total energy (which is calculated by converting the mass of the fuel
into units of energy and combining the fuel energy with the electrical energy4) is dominated by the
manufacturing life-cycle stage, again mostly due to the large LPG fuel energy used in CRT glass
production (Figure 2-9).
Outputs measured in mass include air emissions, waste water, water pollutants and hazardous,
solid, and radioactive waste. Wastewater, by mass (or volume), constitutes the greatest output;
however, wastewater alone will not be used to calculate water-related impacts. Water pollutants are
also used to calculate water-related impacts. Of the remaining outputs measured in mass (i.e., air
emissions, and hazardous, solid and radioactive waste), which are shown on Figure 2-10, air
emissions are the greatest contributor to outputs in mass. Note that radioactivity is measured in
Bequerels (Bq) and cannot be compared on the same scale.
Considering each inventory type and their contributions by life-cycle stage, the mass of
wastewater and water pollutants are greatest in the manufacturing life-cycle stage (again due to LPG
consumption). The outputs of air emissions, hazardous waste, solid waste, radioactive waste, and
radioactivity all have the greatest contribution from the use stage.
For the outputs, all the totals represented in Table 2-25 include outputs to all dispositions.
For example, water outputs sent offsite to treatment as well as those directly discharged to surface
waters are all included. Similarly, hazardous, solid and radioactive waste outputs may be landfilled,
treated or recycled. The inventory shows these as totals; however, when impacts are calculated, the
dispositions dictate which inventory items will be used to calculate impacts (Chapter 3).
The tables and figures discussed above show the total inventories for particular input or
output types by life-cycle stage. Tables in Appendix J list each material that contributes to those
totals. Figures 2-11 through 2-23 show the total contribution by life-cycle stage, based on the entire
input/output type-specific tables in Appendix J. Summary tables for the CRT (Tables 2-26 through
2-34), developed from the Tables in Appendix J, show the top contributing inventory items to each
input or output type. Note that Table 2-28 includes input/output types that are classified together as
utilities: water, fuel, electricity and total energy.
Conversions and calculations of energy impacts are described in the LCIA methodology discussion in
Chapter 3.
2-54
-------
2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
±: SOD-,
c
3 400-
ra
300-
tj 200-
,= 100-
16
Upstream
CRT - Primary Materials
421
219
37
Mfg Use
Life-cycle stage
EOL
Figure 2-11. CRT primary material inputs by life-cycle stage
« 12 1
= 10-
g 8-
.2 6-
*J
O 4-
.5 2-I
"s* o
2.1
CRT - Ancillary Materials
3.5
3.5
Upstream
Mfg Use
Life-cycle stage
11
EOL
Figure 2-12. CRT ancillary material inputs by life-cycle stage
^ 500
§ 400
1 300-
° 200 -
1 100 ^
£ o
O)
•* -100-1
CRT - Fuels
8.0
4/:o
0 -3.0
1 In^trpam Mfri 1 IQP FOI
Life-cycle stage
Figure 2-13. CRT fuel inputs by life-cycle stage
2-55
-------
2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
CRT -Water Inputs
^ 15000
'E
.f 10000
n
£
.2 5000
"o
i o
M—
•* -5000
11,400
554
1
Upstream M1g
1,140
i
Use
-27
i
EOL
Life-cycle stage
Figure 2-14. CRT water inputs by life-cycle stage
CRT - Electricity
1= 2500 -,
— 2000-
= 1500-
•5 1000-
§ 500-
M-
~~) 0 - •
5
73 129
l
Upstream M1g
1
2,290
Use
0.23
EOL
Life-cycle stage
Figure 2-15. CRT electricity inputs by life-cycle stage
CRT - Total Energy
,_, 20000-
= 15000-
c 10000-
o
o 5000 -
1 o-
S -5000-
18,300
366
Upstream M1g
2,290
I
Use
-128
EOL
Life-cycle stage
Figure 2-16. CRT energy inputs by life-cycle stage
2-56
-------
2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
CRT - Air Pollutants
(all direct to atmosphere)
'E 500 -I
— 400-
fl!
C 300 -
O
••X 200-
u
C 100-
Hr n
••••, u -
O)
183
30
1 '
•* Upstream Mfg
449
2.5
1 '
Use EOL
Life -cycle stage
Figure 2-1 7. CRT air outputs by life-cycle stage
C
m 15001
c
.0 1000-
o .-s
c c 500 -
£ 3 17 0
RT- Wastewater
• To surface w ater Q To treatment
1,410
95 00
1
5 '
^> -500 -I Upstream Mfg. Use
Life -cycle stage
Figure 2-18. CRT wastewater outputs by
-3.7 0
EOL
life -cycle stage
CRT-Water Pollutants
] To surface n To treatment
'E 25i
3 20 -
1 15-
.0 10-
"3 5 -
3n
u
rr» -5 -
2.00E+01
8.12E-01QOOE+00
7 09F 09 7.02E-06
9.13E-02 O.OOE+070°2E~02 -6.18E-02
1 1.^ _ ±.-_ — ... K M£~. 1 l_ _ 1 — *^\l
Upstream Mfg Use EOL
Life-cycle stage
Figure 2-19. CRT waste pollutant outputs by life-cycle stage
2-57
-------
2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
CRT - Hazardous Waste
I To landfill QTo treatment nTo recycling/reuse
7.2
15 6 -
.1 4-
O)
2 -
0
0.05 0 0
Upstream
000
1.09
Use
EOL
Life-cycle stage
Figure 2-20. CRT hazardous waste outputs by life-cycle stage
CRT - Solid Waste
iTo landfill rjTo treatment BTo recycling/reuse
•£ 100 n
3
g 50 -
O
I '
M—
O) -50-I
74.0
83.3
5.98 3.57
4.2E-03
3.72 3.41
o.o o.o
6.83
Upstream Mfg Use
Life-cycle stage
Figure 2-21. CRT solid waste outputs by life-cycle stage
CRT - Radioactive Waste
(all to landfill)
§ 2.50E-03-,
•5 2.00E-03 -
g 1.50E-03-
;p 1.00E-03-
C 5.00E-04-
5 O.OOE+00
•a
2.28E-03
1.80E-04
2.29E-07
Upstream
Mfg Use
Life-cycle stage
EOL
Figure 2-22. CRT radioactive waste outputs by life-cycle stage
2-58
-------
2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
-^
| 6.00B-07 -I 3
15 4.00B-07 -
£
.O 2.00B-07 -
.U
o
S: -2.00B-07-
CT
m
CRT - Radioactivity
D To landfill n To treatment n To surface water n To air
7,900,000 47,600,000
n 144 000 3,750,000
.«»• o-^'0™ „
4,760
436,000 41
0 00
Upstream Mfg Use EOL
Life -cycle stage
Figure 2-23. CRT radioactivity outputs by life-cycle stage
CRT Primary Inputs
Beginning with the primary data inputs, Figure 2-11 shows that most primary materials
are from the manufacturing and use life-cycle stages. To better understand what some of the top
contributing materials are to those life-cycle stage totals, Table 2-26 shows the top 99% of the
materials contributing to the total CRT primary input inventory. As shown in Table 2-26, the
largest material contributor is petroleum, which is about 54% of all the primary CRT inputs. The
petroleum is mostly (>98%) from the LPG production process, which relates back to the LPG
needed as a fuel in glass production. The other major contributor to primary material inputs is
coal (-27%) which is used to produce electricity consumed in the use stage. More detail on the
processes that contribute greatest within the manufacturing stage will be presented below after
brief discussions of the life-cycle stage breakdowns for each inventory type. For the complete
list of primary materials in the CRT inventory, the total mass, and the mass contribution of each
life-cycle stage, see Appendix J-l, Table J-l.
CRT Ancillary Inputs
Observing Figure 2-12, the mass of ancillary CRT inputs in the EOL life-cycle stage was
greatest (11 kg/functional unit). The upstream stages had the lowest mass of ancillary inputs
compared to the other life-cycle stages. To better understand the materials contributing to those
totals, Table 2-27 shows that clay is the greatest contributor by mass at 41% of the total CRT
ancillary inputs. Clay is used predominately during EOL incineration and landfilling. See Table
J-2 in Appendix J for the complete list of ancillary materials in the CRT inventory.
2-59
-------
2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
Table 2-26. Top 99% of CRT nrimarv materials in
Material
Petroleum (in ground)
Coal, average (in ground)
Assembled CRT monitor
Natural gas
Cathode ray tube (CRT)
CRT glass, unspecified
Iron (Fe, ore)
Steel
Natural gas (in ground)
Sand
Recycled CRT Glass
Bauxite (A12O3, ore)
Iron scrap
Polycarbonate resin
PWB-laminate
Printed wiring board (PWB)
Styrene-butadiene copolymers
PPE
Upstream
1.32E+00
3.57E+00
0
0
0
0
6.90E+00
2.48E-06
8.41E-01
0
0
1.37E+00
9.46E-01
0
0
0
0
0
Mfg
3.72E+02
5.15E+00
0
1.47E+00
1.07E+01
9.76E+00
0
5.16E+00
3.27E+00
2.40E+00
2.06E+00
0
0
9.23E-01
8.47E-01
8.47E-01
8.27E-01
7.35E-01
Use
3.80E+00
1.79E+02
2.20E+01
1.40E+01
0
0
0
0
0
0
0
0
0
0
0
0
0
0
puts (kg/functional unit)
EOL
-1.52E+00
1.79E-02
0
-8.88E-02
0
0
0
0
-1.64E+00
0
0
0
0
0
0
0
0
0
Total
3.75E+02
1.88E+02
2.20E+01
1.54E+01
1.07E+01
9.76E+00
6.90E+00
5.16E+00
2.47E+00
2.40E+00
2.06E+00
1.37E+00
9.46E-01
9.23E-01
8.47E-01
8.47E-01
8.27E-01
7.35E-01
% of total
54.17%
27.15%
3.38%
2.36%
1.64%
1.50%
1.06%
0.79%
0.38%
0.37%
0.32%
0.21%
0.14%
0.14%
0.13%
0.13%
0.13%
0.11%
See Appendix J for complete inventory table.
Table 2-27. Top 99% of CRT ancillary materials inputs (kg/functional unit)
Material
Clay (in ground)
Sand (in ground)
Limestone
Limestone (CaCO3, in ground)
Lime
Sodium chloride (NaCl, in ground or in
sea)
Sulfuric acid
Hydrochloric acid
Sodium hydroxide
Pyrite (FeS2, ore)
Nitric acid
Ferric chloride
Calcium Chloride
Calcium hydroxide
Hydrofluoric acid
Hydrogen peroxide
Ammonium hydroxide
Pumice
Ammonium chloride
Upstream
4.49e-03
5.85e-02
0
8.60e-01
0
7.61e-01
0
0
0
1.94e-01
0
0
0
0
0
0
0
0
0
Mfg
0
2.74e-02
6.91e-02
1.08e+00
3.04e-02
1.26e-02
2.38e-01
2.36e-01
1.98e-01
0
1.44e-01
1.37e-01
1.27e-01
9.54e-02
8.65e-02
8.45e-02
7.90e-02
7.86e-02
7.76e-02
Use
0
0
2.41e+00
0
1.06e+00
0
0
0
0
0
0
0
0
0
0
0
0
0
0
EOL
8.19e+00
2.71e+00
2.41e-04
-2.39e-01
1.06e-04
-3.07e-05
0
0
0
0
0
0
0
0
0
0
0
0
0
Total
8.19e+00
2.80e+00
2.48e+00
1.70e+00
1.09e+00
7.73e-01
2.38e-01
2.36e-01
1.98e-01
1.94e-01
1.44e-01
1.37e-01
1.27e-01
9.54e-02
8.65e-02
8.45e-02
7.90e-02
7.86e-02
7.76e-02
% of total
41.35%
14.13%
12.51%
8.58%
5.49%
3.90%
1.20%
1.19%
1.00%
0.98%
0.73%
0.69%
0.64%
0.48%
0.44%
0.43%
0.40%
0.40%
0.39%
2-60
-------
2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
Table 2-27. Top 99% of CRT ancillary materials inputs (kg/functional unit)
Material
Alkali cleaning agent
Iron (Fe, ore)
Potassium peroxymonosulfate
Sulfuric acid, aluminum salt
Alkali soda (to neutralize acid waste
water)
Polyethylene glycol
Bauxite (A12O3, ore)
Nitrogen
PWB-solder mask solids
Potassium hydroxide
Lubricant (unspecified)
Chlorine
Zinc (Zn, ore)
Aluminum Oxide
Oil (in ground)
Sodium Carbonate
Tin (Sn, ore)
Upstream
0
7.23e-02
0
0
0
0
1.10e-03
0
0
0
4.11e-02
0
3.79e-02
0
0
0
2.43e-02
Mfg
7.72e-02
0
7.06e-02
6.75e-02
5.45e-02
5.04e-02
4.47e-02
4.57e-02
4.37e-02
4.27e-02
0
4.03e-02
0
3.37e-02
0
3.22e-02
0
Use
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
EOL
0
3.41e-03
0
0
0
0
-1.14e-04
0
0
0
0
0
0
0
3.35e-02
0
0
Total
7.72e-02
7.57e-02
7.06e-02
6.75e-02
5.45e-02
5.04e-02
4.57e-02
4.57e-02
4.37e-02
4.27e-02
4.11e-02
4.03e-02
3.79e-02
3.37e-02
3.35e-02
3.22e-02
2.43e-02
% of total
0.39%
0.38%
0.36%
0.34%
0.28%
0.25%
0.23%
0.23%
0.22%
0.22%
0.21%
0.20%
0.19%
0.17%
0.17%
0.16%
0.12%
See Appendix J for complete inventory table.
CRT Utility Inputs
Utility inputs in the CRT life-cycle are presented in the inventory in Table 2-28 and
include fuel (kg/functional unit), electricity (MJ/functional unit), and water (kg or L/functional
unit) inputs. Figures 2-13, 2-14, and 2-15 show the total fuels, water, and electricity inputs,
respectively. The fuel and electricity inputs have also been combined into a total energy input
category, shown in Figure 2-16. This is also considered one of the impact categories of the LCIA
that will be presented in Chapter 3. Therefore, more details on how it is calculated are available
in Chapter 3. Briefly, the mass of the fuels are converted to units of energy and added to the
electrical energy quantities (in units of MJ).
2-61
-------
2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
Table 2-28. CRT utility inputs
Material Upstream
Mfg
Use
EOL
Total % of total
Fuels (kg/functional unit):
LPG
Natural gas (in ground)
Coal, average (in ground)
Petroleum (in ground)
Fuel oil #6
Fuel Oil #2
Natural gas
Coal, lignite (in ground)
LNG
Uranium (U, ore)
Fuel oil #4
Total fuels
0
2.76E+00
2.25E+00
2.02E+00
0
0
0
9.73E-01
0
1.21E-04
0
8.00E+00
3.51E+02
4.56E+01
1.36E+01
9.71E+00
3.68E+00
1.16E+00
2.44E+00
0
3.35E-01
2.29E-04
1.37E-01
4.28E+02
0
0
0
0
0
0
0
0
0
0
0
0
3.03E-03
-2.09E-01
-1.16E-02
-5.77E-02
0
0
-1.30E+00
0
0
-1.99E-07
-1.38E+00
-2.95E+00
3.51E+02
4.82E+01
1.58E+01
1.17E+01
3.68E+00
1.16E+00
1.14E+00
9.73E-01
3.35E-01
3.49E-04
-1.24E+00
4.33E+02
81.10%
11.14%
3.66%
2.70%
0.85%
0.27%
0.26%
0.22%
0.08%
<0.01%
-0.29%
100.00%
Electricity (MJ/functional unit):
Electricity
7.32E+01
1.29E+02
2.29E+03
2.29E-01
2.49E+03
Water (kg or L/functional unit):
Water
Total energy (fuels and electricity.
Energy
5.54E+02
1.14E+04
1.14E+03
-2.73E+01
1.31E+04
MJ/functional unit):
3.66E+02
1.83E+04
2.29E+03
-1.28E+02
2.08E+04
Table 2-28 shows that LPG used in the manufacturing stage dominates the fuel inputs.
LPG from the manufacturing stage is equal to about 81% of all the fuel inputs in the CRT life-
cycle. More detail into the process-specific contributions within the manufacturing stage will be
presented below at the end of this section. Electricity inputs, however, are dominated by the use
stage (-92% of all electricity throughout the CRT life-cycle). When fuel energy and electrical
energy are combined into a total energy input value, the overall energy from manufacturing
greatly exceeds that from the use stage (18,300 MJ/functional unit versus 2,290 MJ/functional
unit). This is depicted in Figure 2-16.
The other utility listed in Table 2-28 is water. Nearly 87% of the water inputs in the CRT
life-cycle are from the manufacturing processes; and nearly 80% are from LPG production alone.
The life-cycle stage contributing the next most is the use stage at 8.7%. This is from the water
used to generate electricity used during the use stage. The upstream stages only contribute about
4% to the total water inputs for the CRT life-cycle. Table J-3 in Appendix J provides the
complete list of inventory items for the CRT.
CRT Air Outputs
Air emissions from the CRT life cycle are dominated from the use stage as seen in
Figure 2-17. This indicates that most air emissions by mass are from the generation of electricity
used by consumers of the monitors. Nearly 68% of the total life-cycle air emissions by mass (or
450 kg/functional unit) are from the use stage. Carbon dioxide (CO2) alone constitutes 445
2-62
-------
2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
kg/functional unit (or about 66% of all air emissions by mass in the life-cycle and nearly 99% of
the use stage air emissions). Table 2-29 reveals the individual contribution of CO2 and other
inventory items that contribute to the top 99.99% of air emissions. (See Appendix J for complete
inventory table.) These are organized from the air emissions that are the largest contributors to
those that are the smaller contributors. Table J-4 in Appendix J shows the contribution of every
air emission in the inventory, organized alphabetically. The next largest air emissions, by life-
cycle stage, are emitted during the manufacturing stage, which contribute about 28% to the total
life-cycle air emissions. Almost 85% of that is air emissions from the LPG production process.
All the air emissions in the CRT inventory are designated as direct emissions to the ambient
environment.5
Table 2-29. Top 99.99% of CRT air pollutant emissions (kg/functional unit)
Material
Carbon dioxide
Sulfur dioxide
Nitrogen oxides
Methane
Sulfur oxides
Carbon monoxide
PM
Nonmethane hydrocarbons, remaining
unspeciated
Hydrocarbons, remaining unspeciated
Hydrochloric acid
Other organic s
PM-10
Nitrogen dioxide
Upstream
2.92e+01
3.37e-01
6.99e-03
6.40e-02
5.71e-03
4.18e-02
1.28e-01
9.97e-02
1.28e-02
2.39e-03
5.60e-04
0
5.76e-02
Mfg
1.79e+02
1.26e-01
6.95e-01
9.08e-01
8.20e-01
4.58e-01
1.31e-01
1.10e-01
1.58e-01
1.12e-02
7.83e-02
3.15e-03
0
Use
4.45e+02
2.49e+00
1.18e+00
6.45e-01
0
8.09e-02
0
0
0
1.08e-01
0
5.78e-02
0
EOL
2.59e+00
8.30e-04
-1.90e-02
-4.30e-02
-2.97e-02
-4.17e-03
-1.88e-02
-1.91e-03
-6.12e-04
-1.04e-03
-3.65e-03
4.78e-06
1.85e-03
Total
6.55e+02
2.96e+00
1.86e+00
1.57e+00
7.96e-01
5.76e-01
2.40e-01
2.08e-01
1.70e-01
1.20e-01
7.52e-02
6.09e-02
5.95e-02
% of total
98.68%
0.45%
0.28%
0.24%
0.12%
0.09%
0.04%
0.03%
0.03%
0.02%
0.01%
0.01%
0.01%
CRT Water Outputs
The volume (or mass) of wastewater released throughout the CRT life-cycle is
approximately 1,520 L (kg) per functional unit. Approximately 6% of that is sent to treatment as
opposed to direct discharge to surface water (Figure 2-18). The mass of chemical pollutants
within the wastewater streams was calculated separately. The total mass of these water
pollutants released, presented by life-cycle stage, is shown in Figure 2-19. The manufacturing
life-cycle stage contributes the greatest mass of water pollutants with approximately 20 kg per
functional unit. This is about 96% of all the water pollutants for the entire life-cycle. The
upstream stages have the second greatest mass of water pollutants at nearly 1 kg/functional unit
(just under 4%). The use and EOL stages are small contributors, with the EOL being negative
due to recovery processes within the EOL stage. Table 2-30 shows the major contributors to the
Note that some companies may not have reported inventory items associated with all output dispositions,
as only some dispositions are used for impact calculations. For example, outputs that are treated or recycled and not
directly released to the environment are not used in calculating impacts and may not have been reported. This could
be applicable to all output inventories.
2-63
-------
2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
water pollutant quantities, and reveals that sodium ion, chloride ions and dissolved solids
contribute nearly 85% of all the water pollutants to the entire life-cycle. Greater than 95% of the
sodium ion outputs are from LPG production and greater than 78% of the chloride ions are from
LPG production. As with other input/output types, LPG production used in glass manufacturing
has a large impact on the CRT inventory. For the complete inventory, listing water pollutants
alphabetically and subtotaled for each life-cycle stage, see Appendix J, Table J-5. Further details
on the manufacturing stage will be provided later.
Table 2-30. Top 99.9% of CRT water pollutant outputs (kg/functional unit)
Material
Sodium (+1)
Chloride ions
Dissolved solids
COD
Suspended solids
BOD
Waste oil
Dissolved solids
Sulfate ion (-4)
Sulfate ion (-4)
Ammonia ions
Metals, remaining
unspeciated
COD
Oil & grease
Nitrogen
Calcium (+2)
Carbonate ion
Phenol
Fluoride
Salts (unspecified)
Suspended solids
Fluorides (F-)
Disposition
surface water
surface water
surface water
surface water
surface water
surface water
surface water
treatment
treatment
surface water
surface water
surface water
treatment
surface water
surface water
surface water
surface water
surface water
surface water
surface water
treatment
surface water
Upstream
2.90e-01
4.29e-01
5.30e-03
l.OOe-02
7.72e-03
3.93e-04
3.65e-03
0
0
3.75e-02
3.54e-06
6.74e-04
0
0
4.46e-05
4.96e-03
4.83e-03
6.25e-05
1.89e-05
1.71e-03
0
9.63e-05
Mfg.
7.04e+00
6.48e+00
3.62e+00
1.60e+00
8.69e-01
1.95e-01
l.Ole-01
8.01e-02
1.09e-03
9.61e-04
2.76e-02
9.75e-03
8.33e-03
7.46e-03
7.18e-03
0
0
3.63e-03
3.45e-03
1.62e-03
1.29e-03
2.97e-03
Use
0
0
0
0
0
0
0
0
6.84e-02
0
0
0
0
0
0
0
0
0
0
0
1.78e-03
0
EOL
-3.08e-02
-2.39e-02
-8.77e-05
-3.94e-03
-2.11e-03
-4.65e-04
-3.13e-04
0
6.84e-06
-1.85e-06
-6.63e-05
-3.42e-05
0
0
0
0
0
-9.41e-06
0
-4.21e-06
1.78e-07
-7.72e-06
Total
7.30e+00
6.88e+00
3.62e+00
1.61e+00
8.74e-01
1.95e-01
1.04e-01
8.01e-02
6.95e-02
3.84e-02
2.75e-02
1.04e-02
8.33e-03
7.46e-03
7.23e-03
4.96e-03
4.83e-03
3.68e-03
3.47e-03
3.33e-03
3.07e-03
3.06e-03
% of total
34.94%
32.95%
17.36%
7.71%
4.19%
0.93%
0.50%
0.38%
0.33%
0.18%
0.13%
0.05%
0.04%
0.04%
0.03%
0.02%
0.02%
0.02%
0.02%
0.02%
0.01%
0.01%
CRT Hazardous Waste Outputs
The total mass of hazardous waste generated throughout the life-cycle of the CRT (Figure
2-20) is mostly from the amount of the monitor that is assumed to be placed in a hazardous waste
landfill (Table 2-31). This 7.2 kg is based on the proportion of monitors assumed to be
hazardous waste as determined in Section 2.5 (EOL) and is approximately 87% of the hazardous
waste generated in the EOL stage. Compared to the total mass of hazardous wastes produced
throughout the CRT life-cycle, the EOL stage contributes about 88%. The disposition of the
waste will be used to determine how impacts are calculated in Chapter 3. Figure 2-20 shows
what portion of hazardous wastes are reported as being landfilled, recycled/reused, or treated.
The amount of hazardous waste from the upstream and manufacturing stages are negligible, by
2-64
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2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
comparison. Table 2-31 and Table J-6 in Appendix J list the hazardous wastes and where each
hazardous waste is disposed.
Table 2-31. Top 99.9% of CRT hazardous waste outputs (kg/functional unit)
Material
EOL CRT monitor, landfilled
Hazardous waste
CRT glass, cullet
CRT glass, funnel
Transformer
PWB-waste cupric etchant
Printed wiring board (PWB)
General hazardous waste
PWB-solder dross
General hazardous waste
PWB-decontaminating debris
PWB-route dust
PWB-lead contaminated waste
oil
Chrome liquid waste (D007
waste)
Cinders from CRT glass mfg
(70% PbO)
Unspecified sludge
Unspecified sludge
CRT glass funnel EP dust (Pb)
(D008 waste)
Waste acid (mostly 3% HC1
solution)
Frit
Slag and ash
Broken CRT glass
Hydrofluoric acid
Disposition
landfill
landfill
R/R
R/R
R/R
R/R
R/R
treatment
R/R
landfill
treatment
R/R
treatment
R/R
landfill
R/R
landfill
R/R
R/R
landfill
landfill
landfill
landfill
Upstream
0
3.85E-04
0
0
0
0
0
0
0
4.85E-02
0
0
0
0
0
0
0
0
0
0
0
0
0
Mfg
0
6.15E-01
0
0
0
2.25E-01
0
1.24E-01
6.70E-02
0
1.55E-02
1.20E-02
1.16E-02
9.80E-03
8.26E-03
5.56E-03
5.22E-03
5.01E-03
3.93E-03
2.99E-03
2.47E-03
1.88E-03
1.78E-03
Use
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
EOL
7.20E+00
-1.50E-03
4.84E-01
2.29E-01
2.28E-01
0
1.46E-01
0
0
-9.61E-05
0
0
0
0
0
0
0
0
0
0
0
0
0
Total
7.20E+00
6.14E-01
4.84E-01
2.29E-01
2.28E-01
2.25E-01
1.46E-01
1.24E-01
6.70E-02
4.84E-02
1.55E-02
1.20E-02
1.16E-02
9.80E-03
8.26E-03
5.56E-03
5.22E-03
5.01E-03
3.93E-03
2.99E-03
2.47E-03
1.88E-03
1.78E-03
% of total
76.1%
6.49%
5.12%
2.42%
2.41%
2.38%
1.54%
1.31%
0.71%
0.51%
0.16%
0.13%
0.12%
0.10%
0.09%
0.06%
0.06%
0.05%
0.04%
0.03%
0.03%
0.02%
0.02%
R/R: recycling/reuse.
See Appendix J for complete inventory table.
CRT Solid Waste Outputs
Figure 2-21 shows that both the manufacturing and use stages contribute significant
amounts of solid waste by mass to the CRT life-cycle. The majority of the solid waste is
landfilled. In terms of mass, the greatest contributor to the solid waste outputs for the CRT life-
cycle is coal waste that is a result of generating electricity (Table 2-32). Therefore, coal waste is
predominately in the use stage, which uses the most electricity, but also in the manufacturing
stage, and to a much lesser degree in the EOL stage. Note that the electricity generation
processes that support the secondary data used were derived from a different source (i.e.,
Ecobilan) and do not include coal waste as an output; however, the equally large amount of solid
waste generated from those processes is listed as "slag and ash" in the upstream and
manufacturing inventories. Overall, the top 80% of solid waste generated in the CRT life-cycle
is from coal waste, slag and ash, dust/sludge, and fly/bottom ash. Note that different inventories
2-65
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2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
used in this project have varying nomenclature and some of these solid wastes may indeed
overlap. Note also that the mass of a CRT monitor that is assumed to be landfilled at the EOL
(3.9 kg/functional unit) is only approximately 2% of the total mass of solid waste in the CRT
life-cycle. See Appendix J, Table J-7 for the complete CRT solid waste inventory.
Table 2-32. To
Material
Coal waste
Slag and ash
Dust/sludge
Fly /bottom ash
Unspecified solid waste
EOL CRT Monitor, landfilled
Unspecified solid waste
Unspecified solid waste
Unspecified waste
EOL CRT Monitor, incinerated
Iron scrap
EOL CRT Monitor, recycled
Broken CRT glass
Mixed industrial (waste)
Slag and ash
EOL CRT Monitor,
remanufactured
Mining waste
Mineral waste
Carbon Steel Scrap
flame retardant high-impact
polystyrene (HIPS)
Waste water treatment (WWT)
sludge
Ferric chloride
CRT glass, faceplate
p 99% of CRT solid waste out
Disposition
landfill
landfill
landfill
landfill
landfill
landfill
treatment
recycle/reuse
landfill
treatment
recycle/reuse
recycle/reuse
recycle/reuse
landfill
recycle/reuse
recycle/reuse
landfill
landfill
recycle/reuse
recycle/reuse
recycle/reuse
recycle/reuse
recycle/reuse
Upstream
0
9.65E-02
0
0
4.94E+00
0
0
3.07E+00
0
0
3.43E-01
0
0
4.87E-02
0
0
4.48E-01
4.42E-01
0
0
0
0
0
Mfg
1.46E+00
6.66E+01
5.64E-01
3.65E-01
0
0
3.66E+00
4.33E-01
3.38E+00
0
0
0
1.08E+00
l.OOE+00
6.85E-01
0
0
2.61E-03
0
0
3.72E-01
3.69E-01
0
>uts (kg/functional unit)
Use
5.09E+01
0
1.97E+01
1.27E+01
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
EOL
5.09E-03
-1.49E+01
1.97E-03
1.27E-03
-7.86E-01
3.91E+00
0
0
-1.49E-02
3.31E+00
2.50E+00
2.42E+00
0
-5.12E-04
-3.01E-03
6.60E-01
-1.90E-06
-6.76E-06
4.10E-01
4.03E-01
0
0
3.54E-01
Total
5.23E+01
5.18E+01
2.02E+01
1.31E+01
4.15E+00
3.91E+00
3.66E+00
3.50E+00
3.36E+00
3.31E+00
2.85E+00
2.42E+00
1.08E+00
1.05E+00
6.82E-01
6.60E-01
4.48E-01
4.44E-01
4.10E-01
4.03E-01
3.72E-01
3.69E-01
3.54E-01
%of
total
30.37%
30.06%
11.75%
7.59%
2.41%
2.27%
2.12%
2.03%
1.95%
1.92%
1.65%
1.40%
0.62%
0.61%
0.40%
0.38%
0.26%
0.26%
0.24%
0.23%
0.22%
0.21%
0.21%
CRT Radioactive Waste Outputs
Radioactive waste outputs in the CRT inventory are found only in the electricity
generation and cold-rolled steel production process. Therefore, radioactive wastes will be found
wherever electricity is used in a process in the CRT life-cycle. Only very small amounts
(approximately 0.003 kg/functional unit) of radioactive waste are generated over the entire life-
cycle of the CRT (Figure 2-22 and Table 2-33). As expected, the majority of this is linked to the
use stage, where most electricity is used in the CRT life-cycle. Low-level radioactive waste
(79%) and depleted uranium (20%) are most of the waste, with very small amounts of highly
radioactive waste and some unspecified radioactive waste in the inventory. The inventory of
radioactive waste outputs is small, and therefore, Table 2-33 lists all material outputs associated
with radioactive waste, in descending order of quantity. Table J-8 in Appendix J lists these in
alphabetical order.
2-66
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2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
Table 2-33. CRT radioactive waste outputs (kg/functional unit)
Material
Low-level radioactive waste
Uranium, depleted
Radioactive waste (unspecified)
Highly radioactive waste (Class C)
Total radioactive wastes
Disposition
landfill
landfill
landfill
landfill
Upstream
4.11E-04
0
1.88E-05
8.65E-06
4.39E-04
Mfg
1.38E-04
4.15E-05
0
0
1.80E-04
Use
1.76E-03
5.27E-04
0
0
2.28E-03
EOL
1.76E-07
5.27E-08
0
0
2.29E-07
Total
2.31E-03
5.69E-04
1.88E-05
8.65E-06
2.90E-03
%of
total
79.5%
19.6%
0.6%
0.3%
100.0%
CRT Radioactivity Outputs
Radioactivity is also inventoried in this project as isotopes that are released to the
environment. Radioactivity is measured in Bequerels and may be released to air, water, or land.
The quantity of radioactivity for each life-cycle stage and different dispositions is presented in
Figure 2-23. Table 2-34 shows the top 99.9% of the radioactivity outputs.
Table 2-34. Top 99.9% of CRT radioactivity outputs (Bq/functional unit)
Material
Molybdenum-99 (isotope)
Plutonium-241 (isotope)
Xenon- 133 (isotope)
Tritium-3 (isotope)
Plutonium-240 (isotope)
Cesium- 135 (isotope)
Radon-222 (isotope)
Plutonium-239 (isotope)
Xenon- 133 (isotope)
Tritium-3 (isotope)
Xenon- 133M (isotope)
Krypton-85 (isotope)
Disposition
treatment
landfill
air
treatment
landfill
landfill
air
landfill
treatment
air
air
air
Upstream
0
3.74e+07
2.43e+03
0
1.62e+05
1.46e+05
1.37e+05
1.14e+05
0
3.47e+02
0
1.73e+02
Mfg
3.72e+06
0
6.28e+03
2.20e+04
0
0
0
0
3.48e+03
2.95e+03
1.99e+04
2.08e+03
Use
4.73e+07
0
3.12e+05
2.80e+05
0
0
0
0
4.43e+04
3.74e+04
2.07e+04
2.65e+04
EOL
4.73e+03
0
3.12e+01
2.80e+01
0
0
0
0
4.43e+00
3.75e+00
2.07e+00
2.65e+00
Total
5.10e+07
3.74e+07
3.21e+05
3.02e+05
1.62e+05
1.46e+05
1.37e+05
1.14e+05
4.78e+04
4.07e+04
4.06e+04
2.87e+04
%of
total
56.75%
41.67%
0.36%
0.34%
0.18%
0.16%
0.15%
0.13%
0.05%
0.05%
0.05%
0.03%
See Appendix J for complete inventory table.
Radioactivity outputs are related to the generation of electricity and therefore the greatest
quantity of radioactivity is from the use stage, as expected. Table J-9 in Appendix J lists the
complete inventory.
CRT Manufacturing Stage
The inventory tables that show the specific materials (i.e., those in Appendix J and Tables
2-26 through 2-34) are the sums of the materials from one or more processes within a life-cycle
stage. To burrow down deeper into the data, the manufacturing stage inventory data are broken
down by process or group of processes. Groups of processes were combined when fewer than
three companies provided data for a process or when confidentiality agreements precluded
presenting individual process data. The manufacturing process groups are presented in Table
2-67
-------
2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
2-35. Also for confidentiality purposes, upstream and EOL data (derived from Ecobilan 's data)
were not broken down by process. Burrowing further into the contributing processes or process
groups is necessary for future manufacturing improvement assessments. Burrowing further into
process-specific data at the use stage is not necessary because electricity generation is the only
process in the use stage.
Table 2-35. CRT process groups
Process group
Monitor assembly
Tube
Glass/frit
PWB
Japanese grid
U.S. grid
Fuels
Process(es) included
monitor assembly
CRT (tube) manufacturing
CRT glass manufacturing, frit manufacturing
PWB manufacturing
electricity generation - Japanese electric grid
electricity generation - U.S. electric grid
production of fuel oils #2, #4 and #6, LPG, and natural gas
Tables 2-36 through 2-44 list the specific inventories for each process group in the
manufacturing stage for each input and output type. Figures 2-24 through 2-34 graph the total
inventories for each process group for each input and output type. It should be noted that the
input/output type that had the greatest contribution in the manufacturing stage compared to other
stages was fuel inputs, which also translated into total energy inputs being greatest in the
manufacturing stage. Nonetheless, for purposes of showing more detail in the manufacturing
stage and allowing for improvement assessments for manufacturers, the individual material
contributions for each manufacturing process group are presented below.
Of the total 421 kg of primary materials per functional unit in the manufacturing stage,
fuels production contributes the greatest (374 kg/functional unit), followed by monitor assembly
(20.1 kg/functional unit), and then tube manufacturing (11.9 kg/functional unit) (Figure 2-24).
The specific material contributions are presented in Table 2-36. Only small amounts of ancillary
materials are used in the CRT life cycle and the manufacturing stage only contributed a small
percentage of the overall ancillary materials in the life-cycle. However, within the manufacturing
life-cycle stage, fuels production and PWB manufacturing had the greatest amount of ancillary
materials (1.16 kg/functional unit each) (Figure 2-25).
2-68
-------
2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
Table 2-36. CRT manufacturing stage primary material inputs
Material
Process group
Monitor assembly
ABS resin
Aluminum (elemental)
Audio cable assembly
Cables/wires
Cables/wires
Cathode ray tube (CRT)
Connector
CRT magnet assembly
CRT shield assembly - ASTM A366/CC#2
Deflection Yoke assembly
Demagnetic coil - PU coated paper
Ferrite
Phosphate ester
Polycarbonate resin
Polystyrene (PS, high impact)
Power cord assembly
PPE
Printed wiring board (PWB)
Solder, unspecified
Steel
Styrene-butadiene copolymers
Tricresyl phosphate
Triphenyl phosphate
Video cable assembly
Total
Tube
Amyl acetate (mixed isomers)
Aquadag
Blue Phosphor (ZnS)
Blue Phosphor (ZnS.Ag.Al)
CRT glass, unspecified
Electron gun
Frit
Green Phosphor (ZnS)
Green Phosphor (ZnS.Cu.Al)
Nickel Alloy (invar)
Red Phosphor (Y2O2S)
Red Phosphor (Y2O2S.Eu)
Steel
Total
Quantity (kg/
(functional unit)
4.24e-01
3.60e-01
9.45e-02
6.12e-02
3.33e-01
1.07e+01
5.67e-02
7.56e-02
2.42e-01
1.51e-01
1.26e-01
1.70e-01
8.31e-03
9.23e-01
1.51e-01
1.13e-01
7.35e-01
8.47e-01
2.67e-02
3.45e+00
8.27e-01
2.30e-02
5.29e-02
1.13e-01
2.01e+01
1.20e-03
2.06e-02
3.84e-03
1.67e-03
9.76e+00
l.Ole-01
6.67e-02
3.34e-03
1.34e-03
2.72e-01
4.65e-03
1.33e-03
1.71e+00
1.19e+01
% of process
group total
2.11%
1.79%
0.47%
0.31%
1.66%
53.30%
0.28%
0.38%
1.21%
0.75%
0.63%
0.85%
0.04%
4.60%
0.75%
0.57%
3.66%
4.22%
0.13%
17.21%
4.13%
0.11%
0.26%
0.57%
100.00%
0.01%
0.17%
0.03%
0.01%
81.70%
0.84%
0.56%
0.03%
0.01%
2.28%
0.04%
0.01%
14.30%
100.00%
% of grand total
4.76%
2.84%
2-69
-------
2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
Table 2-36. CRT manufacturing stage primary material inputs
Material
Process group
Glass/frit
Barium Carbonate
Glass, unspecified
Lead
Potassium Carbonate
Recycled CRT Glass
Sand
Sodium Carbonate
Strontium Carbonate
Zircon Sand
Borax
Lead
Silica
Total
PWB
PWB-laminate
Solder (63% tin; 37% lead)
Total
Japanese grid
Coal, average (in ground)
Natural gas
Petroleum (in ground)
Uranium, yellowcake
Total
U.S. grid
Coal, average (in ground)
Natural gas
Petroleum (in ground)
Uranium, yellowcake
Total
Fuels
Petroleum (in ground)
Natural gas (in ground)
Total
Grand Total
Quantity (kg/
(functional unit)
2.97e-01
4.91e-02
4.47e-01
3.78e-01
2.06e+00
2.40e+00
4.88e-01
3.31e-01
5.43e-02
8.00e-03
4.67e-02
5.33e-03
6.56e+00
8.47e-01
5.08e-02
8.98e-01
2.28e+00
1.25e+00
1.29e+00
3.04e-04
4.82e+00
2.86e+00
2.23e-01
6.07e-02
7.74e-05
3.15e+00
3.70e+02
3.27e+00
3.74e+02
4.21e+02
% of process
group total
4.52%
0.75%
6.82%
5.76%
31.37%
36.57%
7.43%
5.05%
0.83%
0.12%
0.71%
0.08%
100.00%
94.35%
5.66%
100.00%
47.41%
25.89%
26.69%
0.01%
100.00%
90.97%
7.10%
1.93%
<0.01%
100.01%
99.12%
0.88%
100.00%
% of grand total
1.56%
0.21%
1.14%
0.75%
88.74%
100.00%
2-70
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2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
Table 2-37. CRT manufacturing stage ancillary material in
Material
Process group
Monitor assemblv
2,2,4-trimethylpentane
Cyclohexane
Fluorocarbon resin
Isopropyl alcohol
Surfactant, unspecified
Synthetic resin, unspecified
Total
Tube
Acetone
Acrylic Polymer, unspecified
Alkali cleaning agent
Alkali soda (to neutralize acid waste water)
Ammonia
Ammonium bifluoride
Ammonium Bichromate
Ammonium fluoride
Ammonium hydroxide
Ammonium Oxalate
Ammonium Oxalate Monohydrate
Boric acid
Calcium Chloride
Calcium hydroxide
Chlorine
Chromium (VI)
Dimethyl Formamide
Ferric chloride
HV Carbon (paste)
Hydrochloric acid
Hydrofluoric acid
Hydrogen peroxide
Isopentylacetate
Muratic Acid (drum)
Nitric acid
Nitrogen
Oxalic acid
Oxygen (Liquid)
Periodic Acid
Polyvinyl alcohol
Polyvinyl Pyrrolidone (PVP)
Sodium Bichromate
Sodium Bichromate Bihydrate (VI)
Quantity (kg/
(functional unit)
1.50e-04
1.88e-04
3.75e-05
1.94e-02
1.42e-04
8.53e-04
2.08e-02
3.17e-04
9.13e-03
7.72e-02
5.45e-02
1.19e-04
2.04e-03
3.50e-05
8.91e-04
1.41e-03
8.92e-05
3.16e-04
4.73e-03
1.27e-01
9.54e-02
4.03e-02
7.63e-05
4.36e-05
1.37e-01
1.14e-05
4.39e-02
7.39e-03
5.34e-02
1.74e-03
1.87e-03
8.17e-03
4.57e-02
5.35e-05
7.57e-03
2.26e-04
8.11e-03
2.41e-02
1.05e-04
3.10e-05
% of process
group total
0.72%
0.90%
0.18%
93.40%
0.68%
4.10%
4.79%
0.04%
1.02%
8.61%
6.08%
0.01%
0.23%
<0.01%
0.10%
0.16%
0.01%
0.04%
0.53%
14.18%
10.64%
4.50%
0.01%
<0.01%
15.32%
<0.01%
4.89%
0.82%
5.96%
0.19%
0.21%
0.91%
5.10%
0.01%
0.84%
0.03%
0.90%
2.69%
0.01%
<0.01%
puts
% of grand total
0.59%
2-71
-------
2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
Table 2-37. CRT manufacturing stage ancillary material in
Material
Process group
Sodium hydroxide
Sodium Hypochlorite
Sodium Metabisulfite
Sodium Persulfate
Sulfuric acid
Sulfuric acid, aluminum salt
Toluene
unspecified CRT process material
Xylene (mixed isomers)
Total
Glass/frit
Aluminum Oxide
Cerium Oxide
Chromium Oxide
Hydrofluoric acid
Pumice
Total
PWB
Ammonium chloride
Ammonium hydroxide
Formaldehyde
Glycol ethers
Hydrochloric acid
Hydrogen peroxide
Nitric acid
Polyethylene glycol
Potassium hydroxide
Potassium permanganate
Potassium peroxymonosulfate
PWB-solder mask solids
Sodium Carbonate
Sodium hydroxide
Sulfuric acid
Total
Japanese grid
Lime
Limestone
Total
U.S. grid
Lime
Limestone
Quantity (kg/
(functional unit)
3.52e-03
9.25e-05
4.67e-03
3.54e-04
5.58e-02
6.75e-02
4.80e-03
5.77e-03
4.80e-04
8.97e-01
3.37e-02
3.28e-03
5.62e-05
7.91e-02
7.86e-02
1.95e-01
7.76e-02
7.76e-02
6.60e-03
2.35e-02
1.92e-01
3.10e-02
1.36e-01
5.04e-02
4.27e-02
1.16e-03
7.06e-02
4.37e-02
3.22e-02
1.94e-01
1.83e-01
1.16e+00
1.35e-02
3.06e-02
4.41e-02
1.69e-02
3.85e-02
% of process
group total
0.39%
0.01%
0.52%
0.04%
6.23%
7.53%
0.54%
0.64%
0.05%
100.00%
17.30%
1.68%
0.03%
40.61%
40.37%
100.00%
6.68%
6.68%
0.57%
2.03%
16.51%
2.67%
11.70%
4.34%
3.68%
0.10%
6.08%
3.76%
2.77%
16.71%
15.72%
100.00%
30.57%
69.43%
100.00%
30.52%
69.48%
puts
% of grand total
25.36%
5.51%
32.84%
1.25%
2-72
-------
2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
Table 2-37. CRT manufacturing stage ancillary material in
Material
Process group
Total
Fuels
Bauxite (A12O3, ore)
Limestone (CaCOS, in ground)
Sand (in ground)
Sodium chloride (NaCl, in ground or in sea)
Total
Grand Total
Quantity (kg/
(functional unit)
5.53e-02
4.47e-02
1.08e+00
2.74e-02
1.26e-02
1.16e+00
3.54e+00
% of process
group total
100.00%
3.85%
92.71%
2.36%
1.08%
100.00%
puts
% of grand total
1.57%
32.89%
100.00%
2-73
-------
2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
Table 2-38. CRT manufacturing stage utility inputs
Material
Process group
Fuels (kg/functional unit):
Monitor assembly
Fuel oil #4
Tube
Fuel oil #6
LNG
Natural gas
Total
Glass/frit
Fuel oil #2
Liquified petroleum gas (LPG)
Natural gas
Total
PWB
Natural sas
Fuels
Coal, average (in ground)
Natural gas (in ground)
Petroleum (in ground)
Uranium (U, ore)
Total
Grand Total
Electricity (MJ/functional unit):
Monitor assembly
Tube
Glass/frit
PWB
Total
Water (kg or L/functional unit):
Monitor assembly
Tube
Glass/frit
PWB
Japanese grid
U.S. grid
Fuels
Total
Quantity
??
3.68e+00
3.35e-01
8.37e-01
4.86e+00
1.16e+00
3.51e+02
1.21e+00
3.53e+02
??
1.36e+01
4.56e+01
9.71e+00
2.29e-04
6.89e+01
4.27e+02
1.33e+01
3.19e+01
7.40e+01
l.OOe+01
1.29e+02
3.51e+01
8.11e+02
0
4.22e+01
4.43e+01
1.82e+01
1.05e+04
1.14e+04
% of process
group total
75.86%
6.91%
17.23%
100.00%
0.33%
99.33%
0.34%
100.00%
19.71%
66.20%
14.08%
<0.01%
100.01%
% of grand total
ERR
1.14%
82.72%
ERR
16.14%
100.00%
10.27%
24.68%
57.27%
7.77%
100.00%
0.31%
7.09%
0.00%
0.37%
0.39%
0.16%
91.69%
100.00%
Total energy (fuels and electricity, MJ/functional unit):
Monitor assembly
Tube
1.90e+01
2.37e+02
0.10%
1.29%
2-74
-------
2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
Table 2-38. CRT manufacturing stage utility inputs
Material
Process group
Glass/frit
PWB
Fuels
Total
Quantity
1.52e+04
2.74e+01
2.79e+03
1.83e+04
% of process
group total
% of grand total
83.23%
0.15%
15.22%
100.00%
2-75
-------
2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
Table 2-39. CRT manufacturing stage air emissions
Material
Process group
Tube
Carbon monoxide
Dimethyl Formamide
Nitrogen oxides
Nonmethane hydrocarbons, remaining unspeciated
Sulfur oxides
Toluene
Xylene (mixed isomers)
Total
Glass/frit
Barium
Carbon dioxide
Carbon monoxide
Chromium
Cobalt
Copper
Fluorides (F-)
Lead
Manganese
Nickel
Nitrogen oxides
PM
Sulfur oxides
Zinc (elemental)
Total
PWB
Formaldehyde
Japanese grid
1,1,1 -Trichloroethane
1 ,2-Dichloroethane
2,3,7,8-TCDD
2,3,7,8-TCDF
2,4-Dinitrotoluene
2-Chloroacetophenone
2-Methylnaphthalene
5-Methyl chrysene
Acenaphthene
Acenaphthylene
Acetaldehyde
Acetophenone
Acrolein
Anthracene
Quantity (kg/
(functional unit)
1.70E-02
3.49E-05
2.17E-03
1.59E-04
9.96E-03
3.84E-03
3.84E-04
3.35E-02
9.33E-10
2.85E+00
1.64E-04
1.39E-07
1.43E-10
6.33E-10
2.93E-05
3.22E-07
4.67E-10
5.33E-10
4.47E-02
1.10E-04
5.08E-05
4.67E-09
2.90E+00
3.88E-05
6.46E-08
4.57E-08
1.68E-14
5.84E-14
3.19E-10
8.00E-09
2.38E-10
2.51E-11
4.32E-09
3.29E-10
6.52E-07
1.71E-08
3.31E-07
4.55E-10
% of process group
total
50.61%
0.10%
6.48%
0.47%
29.73%
11.46%
1.15%
100.00%
<0.01%
98.45%
0.01%
<0.01%
<0.01%
<0.01%
<0.01%
<0.01%
<0.01%
<0.01%
1.54%
<0.01%
<0.01%
<0.01%
1.57%
<0.01%
<0.01%
<0.01%
<0.01%
<0.01%
<0.01%
<0.01%
<0.01%
<0.01%
<0.01%
<0.01%
<0.01%
<0.01%
<0.01%
% of grand total
0.02%
1.59%
0.00%
2-76
-------
2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
Table 2-39. CRT manufacturing stage air emissions
Material
Process group
Antimony
Arsenic
Barium
Benzene
Benzo[a]anthracene
Benzo |a]pyrene
Benzo [b,j ,k]fluoranthene
Benzo [g,h,i]perylene
Benzyl chloride
Beryllium
Biphenyl
Bromoform
Bromomethane
Cadmium
Carbon dioxide
Carbon disulfide
Carbon monoxide
Chloride ions
Chlorobenzene
Chloroform
Chromium (III)
Chromium (VI)
Chrysene
Cobalt
Copper
Cumene hydroperoxide
Cyanide (-1)
Di(2-ethylhexyl)phthalate
Dibenzo |a,h| anthracene
Dichloromethane
Dimethyl sulfate
Dioxins, remaining unspeciated
Ethyl Chloride
Ethylbenzene
Ethylene dibromide
Fluoranthene
Fluorene
Fluorides (F-)
Formaldehyde
Furans, remainins unspeciated
Quantity (kg/
(functional unit)
9.50E-07
7.01E-07
5.18E-07
1.52E-06
8.00E-10
4.35E-11
3.89E-10
4.30E-10
8.00E-07
3.23E-08
1.94E-09
4.46E-08
1.83E-07
1.41E-07
1.54E+01
1.49E-07
2.80E-03
6.14E-05
2.51E-08
6.74E-08
5.52E-07
1.34E-07
5.35E-10
1.18E-06
3.18E-07
6.06E-09
2.86E-06
8.34E-08
2.96E-10
3.31E-07
5.49E-08
7.46E-13
4.80E-08
1.19E-07
1.37E-09
1.75E-09
1.83E-09
6.60E-06
1.02E-05
1.19E-12
% of process group
total
0.01%
<0.01%
<0.01%
<0.01%
<0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
99.14%
0.01%
0.02%
O.01%
O.01%
O.01%
0.01%
0.01%
0.01%
0.01%
O.01%
O.01%
O.01%
O.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
% of grand total
2-77
-------
2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
Table 2-39. CRT manufacturing stage air emissions
Material
Process group
Hexane
Hydrochloric acid
Hydrofluoric acid
Indeno( 1 ,2,3 -cd)pyrene
Isophorone
Lead (Pb, ore)
Magnesium
Manganese (Mn, ore)
Mercury
Methane
Methyl chloride
Methyl ethyl ketone
Methyl hydrazine
Methyl methacrylate
Methyl tert-butyl ether
Molybdenum
Naphthalene
Nickel
Nitrogen oxides
Nitrous oxide
o-xylene
Phenanthrene
Phenol
PM-10
Propionaldehyde
Pyrene
Selenium
Styrene
Sulfur dioxide
Tetrachloroethylene
TOCs, remaining unspeciated
Toluene
Vanadium
Vinyl acetate
Xylene (mixed isomers)
Zinc (elemental)
Total
U.S. grid
1,1,1 -Trichloroethane
1 ,2-Dichloroethane
2,3,7,8-TCDD
Quantity (kg/
(functional unit)
7.66E-08
1.37E-03
1.71E-04
4.48E-10
6.63E-07
4.41E-07
1.26E-05
1.09E-06
1.18E-07
8.13E-05
6.06E-07
4.46E-07
1.94E-07
2.29E-08
3.99E-08
1.55E-07
2.21E-07
1.47E-05
4.07E-02
1.12E-04
1.93E-08
5.21E-09
1.83E-08
2.00E-03
4.34E-07
1.26E-09
1.61E-06
2.86E-08
8.62E-02
4.92E-08
1.97E-04
1.43E-06
5.71E-06
8.67E-09
4.23E-08
5.15E-06
1.55E-K)!
3.06E-08
5.73E-08
2.05E-14
% of process group
total
0.01%
<0.01%
<0.01%
<0.01%
<0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.26%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.56%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
100.00%
0.01%
0.01%
0.01%
% of grand total
8.50%
2-78
-------
2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
Table 2-39. CRT manufacturing stage air emissions
Material
Process group
2,3,7,8-TCDF
2,4-Dinitrotoluene
2-Chloroacetophenone
2-Methylnaphthalene
5-Methyl chrysene
Acenaphthene
Acenaphthylene
Acetaldehyde
Acetophenone
Acrolein
Anthracene
Antimony
Arsenic
Barium
Benzene
Benzo[a]anthracene
Benzo |a]pyrene
Benzo [b,j ,klfluoranthene
Benzo [g,h,i]perylene
Benzyl chloride
Beryllium
Biphenyl
Bromoform
Bromometliane
Cadmium
Carbon dioxide
Carbon disulfide
Carbon monoxide
Chloride ions
Chlorobenzene
Chloroform
Chromium (III)
Chromium (VI)
Chrysene
Cobalt
Copper
Cumene
Cyanide (-1)
Di(2-ethylhexyl)phthalate
Dibenzo [a,h] anthracene
Dichloromethane
Quantity (kg/
(functional unit)
7.30E-14
4.01E-10
l.OOE-08
4.26E-11
3.15E-11
9.06E-10
3.60E-10
8.16E-07
2.15E-08
4.15E-07
3.11E-10
6.96E-08
5.99E-07
3.28E-08
1.86E-06
1.48E-10
5.44E-11
1.70E-10
5.75E-11
l.OOE-06
3.05E-08
2.43E-09
5.58E-08
2.29E-07
7.69E-08
7.10E+00
1.86E-07
1.29E-03
2.90E-06
3.15E-08
8.45E-08
3.88E-07
1.15E-07
1.63E-10
1.94E-07
1.59E-08
7.59E-09
3.58E-06
1.04E-07
1.40E-11
4.15E-07
% of process group
total
0.01%
<0.01%
<0.01%
<0.01%
<0.01%
<0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
98.98%
O.01%
0.02%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
% of grand total
2-79
-------
2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
Table 2-39. CRT manufacturing stage air emissions
Material
Process group
Dimethyl sulfate
Dioxins, remaining unspeciated
Ethyl Chloride
Ethylbenzene
Ethylene dibromide
Fluoranthene
Fluorene
Fluoride
Formaldehyde
Furans, remaining unspeciated
Hexane
Hydrochloric acid
Hydrofluoric acid
Indeno( 1 ,2,3 -cd)pyrene
Isophorone
Lead
Magnesium
Manganese
Mercury
Methane
Methyl chloride
Methyl ethyl ketone
Methyl hydrazine
Methyl methacrylate
Methyl tert-butyl ether
Molybdenum
Naphthalene
Nickel
Nitrogen oxides
Nitrous oxide
o-xylene
Phenanthrene
Phenol
Phosphorus (yellow or white)
PM-10
Propionaldehyde
Pyrene
Selenium
Styrene
Sulfur dioxide
Tetrachloroethvlene
Quantity (kg/
(functional unit)
6.87E-08
9.33E-13
6.01E-08
1.35E-07
1.72E-09
1.07E-09
1.34E-09
3.12E-07
1.35E-06
1.49E-12
9.59E-08
1.72E-03
2.15E-04
1.05E-10
8.30E-07
2.04E-07
1.57E-05
7.28E-07
1.20E-07
1.03E-02
7.59E-07
5.58E-07
2.43E-07
2.86E-08
5.01E-08
9.32E-09
2.92E-08
1.09E-06
1.88E-02
5.42E-05
9.11E-10
4.00E-09
2.29E-08
7.91E-08
9.22E-04
5.44E-07
5.32E-10
1.87E-06
3.58E-08
3.98E-02
6.16E-08
% of process group
total
0.01%
<0.01%
<0.01%
<0.01%
<0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.02%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.14%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.26%
O.01%
O.01%
O.01%
O.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.56%
0.01%
% of grand total
2-80
-------
2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
Table 2-39. CRT manufacturing stage air emissions
Material
Process group
TOCs, remaining unspeciated
Toluene
Vanadium
Vinyl acetate
Xylene (mixed isomers)
Zinc (elemental)
Total
Fuels
1,1,1 -Trichloroethane
1 ,2-Dichloroethane
1 ,4-Dichlorobenzene
2,4-Dinitrotoluene
2-Chloroacetophenone
2-Methylnaphthalene
3 -Methy Icholanthrene
5-Methyl chrysene
Acenaphthene
Acenaphthylene
Acetaldehyde
Acetophenone
Acrolein
Aldehydes
Aluminum (elemental)
Ammonia
Anthracene
Antimony
Aromatic hydrocarbons
Arsenic
Barium
Benzene
Benzo [alanthracene
Benzo |a]pyrene
Benzo [b,j ,k]fluoranthene
Benzo [blfluoranthene
Benzo |g,h,ilperylene
Benzo |Y|fluoranthene
Benzyl chloride
Beryllium
Biphenyl
Bromoform
Bromomethane
Quantity (kg/
(functional unit)
9.19E-05
4.06E-07
2.81E-07
1.09E-08
5.30E-08
2.43E-07
7.17E400
1.36E-07
2.71E-07
3.06E-07
1.90E-09
4.75E-08
6.11E-09
4.59E-10
1.49E-10
5.31E-09
2.17E-09
3.86E-06
1.02E-07
1.97E-06
1.52E-03
1.98E-05
2.35E-03
2.12E-09
6.36E-07
5.29E-08
1.41E-05
3.33E-07
1.57E-02
1.27E-09
6.94E-10
7.46E-10
5.07E-10
5.63E-10
5.07E-10
4.75E-06
1.42E-06
1.15E-08
2.64E-07
1.08E-06
% of process group
total
0.01%
<0.01%
<0.01%
<0.01%
<0.01%
0.01%
100.00%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
% of grand total
3.93%
2-81
-------
2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
Table 2-39. CRT manufacturing stage air emissions
Material
Process group
Butane
Cadmium
Calcium
Carbon dioxide
Carbon disulfide
Carbon monoxide
Chloride ions
Chlorine
Chlorobenzene
Chloroform
Chromium (III)
Chromium (VI)
Chrysene
Cobalt
Copper
Cumene
Cyanide (-1)
Di(2-ethylhexyl)phthalate
Dibenzo [a,h] anthracene
Dichloromethane
Dimethyl sulfate
Dimethylbenzanthracene
Dioxins, remaining unspeciated
Ethane
Ethyl Chloride
Ethylbenzene
Ethylene dibromide
Fluoranthene
Fluorene
Fluorides (F-)
Formaldehyde
Furans, remaining unspeciated
Halogenated hydrocarbons (unspecified)
HALON-1301
Hexane
Hydrocarbons, remaining unspeciated
Hydrochloric acid
Hydrofluoric acid
Hydrogen sulfide
Indeno( 1,2,3 -cd)py rene
Iron
Quantity (kg/
(functional unit)
5.35E-04
8.20E-07
1.72E-05
1.54E+02
8.81E-07
4.36E-01
3.39E-05
5.84E-09
1.49E-07
4.00E-07
2.13E-05
2.13E-05
1.22E-09
2.54E-06
1.57E-06
3.59E-08
1.69E-05
4.95E-07
3.61E-10
1.97E-06
3.25E-07
3.82E-09
1.10E-10
7.90E-04
2.85E-07
6.44E-07
8.14E-09
5.74E-09
7.03E-09
3.84E-06
1.19E-03
5.11E-10
2.94E-13
5.11E-10
4.59E-04
1.58E-01
8.14E-03
1.02E-03
3.11E-03
9.43E-10
3.83E-05
% of process group
total
0.01%
<0.01%
<0.01%
97.92%
<0.01%
0.28%
0.01%
0.01%
0.01%
O.01%
O.01%
O.01%
O.01%
0.01%
0.01%
0.01%
O.01%
O.01%
O.01%
O.01%
0.01%
0.01%
0.01%
0.01%
O.01%
O.01%
O.01%
O.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.10%
0.01%
0.01%
0.01%
0.01%
0.01%
% of grand total
2-82
-------
2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
Table 2-39. CRT manufacturing stage air emissions
Material
Process group
Isophorone
Lead
Magnesium
Manganese
Mercury
Metals, remaining unspeciated
Methane
Methyl chloride
Methyl ethyl ketone
Methyl hydrazine
Methyl methacrylate
Methyl tert-butyl ether
Molybdenum
Naphthalene
Nickel
Nitrogen oxides
Nitrous oxide
Nonmethane hydrocarbons, remaining unspeciated
n-Propane
Other organics
o-xylene
Pentane
Phenanthrene
Phenol
Phosphorus (yellow or white)
PM
PM-10
Polycyclic aromatic hydrocarbons
Propionaldehyde
Pyrene
Selenium
Silicon
Sodium
Styrene
Sulfur oxides
Tetrachloroethylene
Toluene
Vanadium
Quantity (kg/
(functional unit)
3.93E-06
1.25E-05
7.46E-05
2.26E-05
8.81E-07
3.16E-07
8.98E-01
3.59E-06
2.64E-06
1.15E-06
1.36E-07
2.37E-07
1.97E-06
3.54E-07
1.24E-04
5.88E-01
1.64E-02
1.10E-01
1.69E-06
7.83E-02
1.11E-06
6.62E-04
2.30E-08
1.08E-07
1.25E-05
1.31E-01
2.28E-04
5.87E-11
2.58E-06
3.65E-09
9.47E-06
1.72E-05
1.02E-04
1.69E-07
8.10E-01
2.92E-07
3.81E-06
2.68E-04
% of process group
total
0.01%
<0.01%
<0.01%
<0.01%
<0.01%
0.01%
0.57%
0.01%
0.01%
O.01%
O.01%
O.01%
O.01%
0.01%
0.01%
0.37%
0.01%
0.07%
O.01%
0.05%
0.01%
0.01%
0.01%
0.01%
O.01%
0.08%
O.01%
O.01%
0.01%
O.01%
O.01%
O.01%
O.01%
0.01%
0.52%
0.01%
O.01%
O.01%
% of grand total
2-83
-------
2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
Table 2-39. CRT manufacturing stage air emissions
Material
Process group
Vinyl acetate
Zinc (elemental)
Total
Grand Total
Quantity (kg/
(functional unit)
5.15E-08
1.02E-05
1.57E+02
1.83E-KJ2
% of process group
total
0.01%
O.01%
100.00%
% of grand total
85.96%
100.00%
2-84
-------
2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
Table 2-40. CRT manufacturing stage water outputs (wastewaters and pollutants)
Material
Process group
Disposition
Quantity (kg/
functional unit)
% of process group
total
% of grand
total
WASTEWATER STREAMS
Tube
Wastewater stream
Wastewater stream
Total
Glass/frit
Wastewater stream
PWB
Wastewater stream
Fuels
Wastewater stream
Grand Total
treatment
surface water
surface water
treatment
surface water
5.26e+01
4.81e+02
5.33e+02
3.62e+01
4.22e+01
8.94e+02
1.51e+03
9.87%
90.13%
100.00%
35.42%
2.40%
2.80%
59.38%
100.00%
WASTEWATER POLLUTANTS
Tube
BOD
Chromium ore
Chromium ore
COD
COD
Copper
Cyanide (-1)
Dissolved solids
Fluoride
Fluoride
Iron
Lead
Lead
Manganese
Molybdenum
Nickel
Nitrogen
Oil & grease
Phosphate as P2O5
Phosphorus (yellow or white)
Suspended solids
Suspended solids
Zinc (elemental)
Zinc (elemental)
Total
Glass/frit
BOD
surface water
surface water
treatment
surface water
treatment
surface water
surface water
treatment
surface water
treatment
surface water
surface water
treatment
surface water
surface water
surface water
surface water
surface water
surface water
surface water
surface water
treatment
surface water
treatment
surface water
6.39e-03
1.02e-05
1.03e-06
7.22e-03
8.33e-03
1.80e-06
6.06e-07
8.01e-02
3.45e-03
3.51e-04
1.65e-04
3.01e-06
1.03e-06
3.60e-06
1.20e-07
7.93e-05
7.18e-03
2.41e-04
1.21e-06
5.05e-05
4.63e-03
1.28e-03
1.39e-05
1.03e-06
1.20e-01
8.20e-06
5.34%
<0.01%
<0.01%
6.04%
6.97%
0.01%
0.01%
67.03%
2.89%
0.29%
0.14%
O.01%
0.01%
0.01%
0.01%
0.07%
6.01%
0.20%
O.01%
0.04%
3.87%
1.07%
0.01%
0.01%
100.00%
0.01%
2.51%
2-85
-------
2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
Table 2-40. CRT manufacturing stage water outputs (wastewaters and pollutants)
Material
Process group
Chloride ions
Chromium
COD
Dissolved solids
Fluorides (F-)
Iron
Lead
Nickel
Nitrates/nitrites
Oil & grease
Suspended solids
Total
PWB
Copper (+1 & +2)
Lead cmpds
Total
Japanese grid
Sulfate ion (-4)
Suspended solids
Total
U.S. grid
Sulfate ion (-4)
Suspended solids
Total
Fuels
Acids (H+)
Adsorbable organic halides
Aluminum (+3)
Ammonia ions
Aromatic hydrocarbons
Barium cmpds
BOD
Cadmium cmpds
Chloride ions
Chromium (III)
Chromium (VI)
COD
Copper (+1 & +2)
Cyanide (-1)
Dissolved organics
Dissolved solids
Fluorides (F-)
Disposition
surface water
surface water
surface water
surface water
surface water
surface water
surface water
surface water
surface water
surface water
surface water
treatment
treatment
surface water
surface water
treatment
treatment
surface water
surface water
surface water
surface water
surface water
surface water
surface water
surface water
surface water
surface water
surface water
surface water
surface water
surface water
surface water
surface water
surface water
Quantity (kg/
functional unit)
l.Ole+00
8.20e-08
8.20e-06
3.62e+00
2.93e-03
2.77e-03
4.34e-05
8.20e-08
3.95e-06
7.22e-03
7.23e-03
4.65e+00
9.71e-05
1.62e-05
1.13e-04
8.72e-04
2.27e-05
8.94e-04
1.09e-03
2.84e-05
1.12e-03
2.50e-09
2.27e-15
8.62e-10
l.Ole-07
5.33e-13
1.71e-12
1.21e-06
1.78e-15
3.56e-05
3.31e-10
3.31e-10
9.80e-06
3.55e-14
2.49e-15
6.62e-09
2.21e-07
1.80e-08
% of process group
total
21.73%
<0.01%
<0.01%
77.84%
0.06%
0.06%
0.01%
0.01%
0.01%
0.16%
0.16%
100.00%
85.71%
14.29%
100.00%
97.46%
2.54%
100.00%
97.46%
2.54%
100.00%
0.01%
0.01%
0.01%
0.10%
O.01%
O.01%
1.22%
0.01%
36.07%
0.01%
0.01%
9.92%
O.01%
O.01%
O.01%
0.22%
0.02%
% of grand
total
97.45%
0.00%
0.02%
0.02%
2-86
-------
2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
Table 2-40. CRT manufacturing stage water outputs (wastewaters and pollutants)
Material
Process group
Halogenated matter (organic)
Hydrocarbons, remaining unspeciated
Iron (+2 & +3)
Lead cmpds
Mercury compounds
Metals, remaining unspeciated
Nickel cmpds
Nitrate
Other nitrogen
Phenol
Phosphates
Polycyclic aromatic hydrocarbons
Salts (unspecified)
Sodium (+1)
Sulfate ion (-4)
Sulfide
Suspended solids
TOCs
Toluene
Waste oil
Zinc (+2)
Total
Grand Total
Disposition
surface water
surface water
surface water
surface water
surface water
surface water
surface water
surface water
surface water
surface water
surface water
surface water
surface water
surface water
surface water
surface water
surface water
surface water
surface water
surface water
surface water
Quantity (kg/
functional unit)
7.11e-16
2.61e-09
3.79e-ll
7.11e-15
8.17e-18
6.27e-08
3.55e-15
4.53e-09
9.59e-14
2.21e-08
2.02e-ll
8.53e-15
9.83e-09
4.59e-05
4.26e-09
1.38e-09
5.19e-06
5.33e-12
7.82e-14
6.26e-07
1.58e-10
9.88e-05
4.77e+00
% of process group
total
0.01%
<0.01%
<0.01%
<0.01%
<0.01%
0.06%
0.01%
0.01%
0.01%
0.02%
O.01%
O.01%
O.01%
46.44%
0.01%
0.01%
5.26%
O.01%
O.01%
0.63%
0.01%
100.00%
% of grand
total
0.00%
100.00%
2-87
-------
2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
Table 2-41. CRT manufacturing stage hazardous waste outputs (kg/functional unit)
Material
Process group
Tube
Frit
Lead sulfate cake
Silica coat waste
Slag and ash
Slurry scrap (chromium-based)
Spent solvent, unspecified
Unspecified sludge
Unspecified sludge
Waste oxygenated solvents
Waste water treatment (WWT) filters
Total
Glass/frit
Barium debris (D008 waste)
Broken CRT glass
Chrome debris (D007 waste)
Chrome liquid waste (D007 waste)
cinders from CRT glass mfg (70% PbO)
CRT glass faceplate EP dust (Pb) (D008
waste)
CRT glass funnel EP dust (Pb) (D008
waste)
Hazardous sludge (Pb) (D008)
Hydrofluoric acid
Lead contaminated grit (D008 waste)
Lead debris (D008 waste)
sludge from CRT glass mfg (1% PbO)
Waste acid (mostly 3% HC1 solution)
Waste Batch (Ba, Pb) (D008 waste)
Waste finishing sludge (Pb) (D008
waste)
Total
PWB
General Hazardous Waste
PWB -Decontaminating debris
PWB -Lead contaminated waste oil
PWB-Route dust
PWB-Solder dross
PWB-Waste cupric etchant
Total
Fuels
Hazardous waste
Disposition
landfill
landfill
treatment
landfill
landfill
treatment
landfill
recycling/reuse
treatment
landfill
landfill
landfill
treatment
recycling/reuse
landfill
landfill
recycling/reuse
landfill
landfill
landfill
landfill
landfill
recycling/reuse
landfill
landfill
treatment
treatment
treatment
recycling/reuse
recycling/reuse
recycling/reuse
landfill
Quantity (kg/
functional unit)
2.99e-03
2.67e-05
2.86e-04
2.47e-03
8.62e-04
2.75e-04
5.22e-03
5.56e-03
9.48e-05
3.40e-04
1.81e-02
2.14e-04
1.88e-03
1.47e-04
9.80e-03
8.26e-03
1.03e-03
5.01e-03
1.52e-03
1.78e-03
3.46e-05
2.14e-04
8.77e-04
3.93e-03
1.41e-03
2.56e-04
3.64e-02
1.24e-01
1.55e-02
1.16e-02
1.20e-02
6.70e-02
2.25e-01
4.55e-01
6.15e-01
% of process
group total
15.58%
0.14%
1.49%
12.90%
4.50%
1.43%
27.26%
29.03%
0.49%
1.78%
100.00%
0.59%
5.17%
0.41%
26.95%
22.71%
2.83%
13.78%
4.17%
4.89%
0.10%
0.59%
2.41%
10.81%
3.89%
0.70%
100.00%
27.26%
3.41%
2.56%
2.64%
14.72%
49.42%
100.00%
% of grand
total
1.61%
3.23%
40.49%
54.67%
2-88
-------
2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
Table 2-41. CRT manufacturing stage hazardous waste outputs (kg/functional unit)
Material
Process group
Grand Total
Disposition
Quantity (kg/
functional unit)
1.12e+00
% of process
group total
% of grand
total
100.00%
2-89
-------
2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
Table 2-42. CRT manufacturing stage solid waste outputs (kg/functional unit)
Material
Process group
Monitor Assembly
Broken CRT glass
Cables/wires
Printed wiring board (PWB)
Waste plastics from CRT monitor
Total
Tube
Broken CRT glass
Ferric chloride
Sludge (aquadag)
Sludge (phosphor)
Spent solvents
(toluene,xylene,dimethyl
formamide,isopropyl alcohol)
Unspecified sludge
Waste alkali (cleaning caustic and
alkali soda effluent)
Waste metals, unspecified
Waste oil
Waste oil
Waste Plastic (packing material)
Waste Plastic (styrene foam)
Waste water treatment (WWT) sludge
Waste water treatment (WWT) sludge
Wastepaper
Wood, average
Total
Glass/frit
abrasive sludge
acid absorbent
blasting media
Cobalt nitrate
CRT glass, faceplate
Diesel fuel
Dust
Nickel nitrate
Oily rags & filter media
Oily rags & filter media
parts cleaner solvent
Plating process sludge
Potassium Carbonate
sludge (calcium fluoride, CaF2)
Disposition
recycling/reuse
recycling/reuse
recycling/reuse
recycling/reuse
recycling/reuse
recycling/reuse
landfill
landfill
recycling/reuse
recycling/reuse
recycling/reuse
recycling/reuse
recycling/reuse
treatment
treatment
recycling/reuse
landfill
recycling/reuse
recycling/reuse
landfill
recycling/reuse
landfill
landfill
treatment
landfill
treatment
treatment
treatment
landfill
recycling/reuse
recycling/reuse
landfill
landfill
recycling/reuse
Quantity(kg/
functional unit)
3.82e-01
8.86e-03
3.70e-02
8.09e-02
5.09e-01
6.94e-01
3.69e-01
2.22e-03
4.31e-03
4.17e-02
1.26e-01
2.12e-02
8.79e-02
1.43e-03
2.55e-03
3.01e-02
3.77e-03
8.43e-02
3.72e-01
8.34e-03
4.94e-03
1.85e+00
4.21e-02
8.13e-05
3.66e-04
6.10e-05
2.43e-02
4.07e-05
3.43e-03
6.10e-05
3.25e-04
4.07e-05
8.13e-05
3.28e-04
3.30e-03
1.75e-02
% of process group
total
75.07%
1.74%
7.28%
15.91%
100.00%
37.43%
19.93%
0.12%
0.23%
2.25%
6.78%
1.15%
4.74%
0.08%
0.14%
1.63%
0.20%
4.55%
20.06%
0.45%
0.27%
100.00%
11.34%
0.02%
0.10%
0.02%
6.54%
0.01%
0.92%
0.02%
0.09%
0.01%
0.02%
0.09%
0.89%
4.72%
% of grand
total
0.63%
2.28%
2-90
-------
2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
Table 2-42. CRT manufacturing stage solid waste outputs (kg/functional unit)
Material
Process group
Sodium Carbonate
Unspecified sludge
Waste alkali, unspecified
Waste oil
Waste refractory
Waste water treatment (WWT) sludge
PM
Total
PWB
PWB-Drill dust
Unspecified solid waste
Unspecified solid waste
Total
Japanese grid
Coal waste
Dust/sludge
Fly/bottom ash
Total
U.S. grid
Coal waste
Dust/sludge
Fly/bottom ash
Total
Fuels
Aluminum scrap
Aluminum scrap, Wabash 319
Bauxite residues
FGD sludge
Mineral waste
Mixed industrial (waste)
Non toxic chemical waste
(unspecified)
Slag and ash
Slag and ash
Unspecified solid waste (incinerated)
Unspecified waste
Total
Grand Total
Disposition
landfill
landfill
treatment
treatment
landfill
landfill
landfill
landfill
recycling/reuse
treatment
landfill
landfill
landfill
landfill
landfill
landfill
recycling/reuse
recycling/reuse
landfill
landfill
landfill
landfill
landfill
landfill
recycling/reuse
treatment
landfill
Quantity(kg/
functional unit)
3.29e-03
7.69e-03
4.21e-05
6.54e-03
2.44e-03
2.59e-01
5.33e-04
3.72e-01
1.49e-02
4.33e-01
3.66e+00
4.11e+00
6.48e-01
2.50e-01
1.62e-01
1.06e+00
8.12e-01
3.14e-01
2.03e-01
1.33e+00
1.82e-04
5.08e-07
1.21e-02
2.14e-01
2.61e-03
l.OOe+00
6.11e-04
6.66e+01
6.85e-01
1.33e-02
3.38e+00
7.19e+01
8.12e+01
% of process group
total
0.89%
2.07%
0.01%
1.76%
0.66%
69.68%
0.14%
100.00%
0.36%
10.53%
89.11%
100.00%
61.12%
23.59%
15.28%
100.00%
61.10%
23.63%
15.27%
100.00%
<0.01%
<0.01%
0.02%
0.30%
0.01%
1.39%
0.01%
92.62%
0.95%
0.02%
4.70%
100.04%
% of grand
total
0.46%
5.06%
1.31%
1.64%
88.62%
100.00%
2-91
-------
2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
Table 2-43. CRT manufacturing stage radioactive waste outputs
Material
Process group
Japanese grid
Low-level radioactive waste
Uranium, depleted
Total
U.S. grid
Low-level radioactive waste
Uranium, depleted
Total
Grand Total
Disposition
landfill
landfill
landfill
landfill
Quantity (kg/
functional unit)
1.10e-04
3.31e-05
1.43e-04
2.80e-05
8.41e-06
3.65e-05
1.80e-04
% of process
group total
76.93%
23.07%
100.00%
76.93%
23.07%
100.00%
% of grand total
79.72%
20.28%
100.00%
2-92
-------
2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
Table 2-44. CRT manufacturing stage radioactivity outputs
Material
Process group
Japanese grid
Antimony- 124 (isotope)
Antimony- 125 (isotope)
Argon-41 (isotope)
Barium-140 (isotope)
Bromine-89 (isotope)
Bromine-90 (isotope)
Cesium- 134 (isotope)
Cesium- 134 (isotope)
Cesium- 137 (isotope)
Cesium- 137 (isotope)
Chromium-51 (isotope)
Chromium-51 (isotope)
Cobalt-57 (isotope)
Cobalt-57 (isotope)
Cobalt-58 (isotope)
Cobalt-58 (isotope)
Cobalt-60 (isotope)
Cobalt-80 (isotope)
Iodine-131 (isotope)
Iodine-131 (isotope)
Iodine- 132 (isotope)
Iodine- 132 (isotope)
Iodine-133 (isotope)
Iodine-133 (isotope)
Iodine- 134 (isotope)
Iodine-135 (isotope)
Iodine-135 (isotope)
Iron-55 (isotope)
Iron-59 (isotope)
Krypton-85 (isotope)
Krypton-85M (isotope)
Krypton-85M (isotope)
Krypton-87 (isotope)
Krypton-88 (isotope)
Lanthanum- 140 (isotope)
Manganese-54 (isotope)
Manganese-54 (isotope)
Molybdenum-99 (isotope)
Niobium-95 (isotope)
Niobium-95 (isotope)
Rubidium-88 (isotope)
Disposition
treatment
treatment
air
treatment
air
air
air
treatment
air
treatment
air
treatment
air
treatment
air
treatment
air
treatment
air
treatment
air
treatment
air
treatment
air
air
treatment
treatment
treatment
air
air
treatment
air
air
treatment
air
treatment
treatment
air
treatment
air
Quantity (Bq/
functional unit)
4.95e-01
1.97e+00
l.OOe+03
3.67e-02
1.16e-04
4.72e-05
3.18e-03
1.32e+00
2.40e-02
1.99e+00
6.29e-02
2.39e+00
1.69e-04
5.78e-02
2.16e-03
2.35e+01
1.62e-02
6.17e+00
7.58e-02
1.10e+00
1.54e-02
4.17e-01
7.03e+01
4.72e-01
7.98e-02
4.01e-03
3.38e-01
5.62e+00
2.886-01
1.66e+03
8.06e+01
1.49e+00
3.006+01
1.41e+02
3.93e-02
8.92e-04
1.57e+00
2.97e+06
3.54e-05
4.05e-01
3.29e-01
% of process group
total
<0.01%
<0.01%
0.03%
<0.01%
<0.01%
<0.01%
<0.01%
<0.01%
<0.01%
<0.01%
<0.01%
<0.01%
<0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.06%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
98.42%
0.01%
0.01%
0.01%
% of grand
total
2-93
-------
2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
Table 2-44. CRT manufacturing stage radioactivity outputs
Material
Process group
Ruthenium- 103 (isotope)
Silver-llOM (isotope)
Silver-llOM (isotope)
Sodium-24 (isotope)
Strontium-89 (isotope)
Strontium-90 (isotope)
Strontium-95 (isotope)
Sulfur- 136 (isotope)
Technetium-99M (isotope)
Technetium-99M (isotope)
Tin-113 (isotope)
Tritium-3 (isotope)
Tritium-3 (isotope)
Xenon-13 1M (isotope)
Xenon-13 1M (isotope)
Xenon- 13 3 (isotope)
Xenon- 13 3 (isotope)
Xenon-133M (isotope)
Xenon-133M (isotope)
Xenon-13 5 (isotope)
Xenon-13 5 (isotope)
Xenon-135M (isotope)
Xenon-13 8 (isotope)
Zinc-85 (isotope)
Zirconium-95 (isotope)
Total
U.S. grid
Antimony- 124 (isotope)
Antimony-125 (isotope)
Argon-41 (isotope)
Barium- 140 (isotope)
Bromine-89 (isotope)
Bromine-90 (isotope)
Cesium- 134 (isotope)
Cesium- 134 (isotope)
Cesium- 136 (isotope)
Cesium- 137 (isotope)
Cesium-137 (isotope)
Chromium-51 (isotope)
Chromium-51 (isotope)
Cobalt-57 (isotope)
Cobalt-57 (isotope)
Disposition
treatment
air
treatment
treatment
treatment
treatment
treatment
treatment
air
treatment
treatment
air
treatment
air
treatment
air
treatment
air
treatment
air
treatment
air
air
treatment
air
treatment
treatment
air
treatment
air
air
air
treatment
treatment
air
treatment
air
treatment
air
treatment
Quantity (Bq/
functional unit)
4.95e-02
1.06e-06
5.78e-01
8.80e-02
9.51e-02
2.24e-02
2.46e-01
5.30e-02
4.75e-06
3.45e-02
5.46e-02
2.35e+03
1.76e+04
1.36e+02
1.81e+01
1.30e+03
2.78e+03
1.96e+04
2.28e+01
7.39e+02
2.07e+01
1.41e+01
4.68e+01
2.65e-02
9.16e-05
3.01e+06
1.26e-01
5.02e-01
2.55e+02
9.33e-03
2.95e-05
1.20e-05
8.09e-04
3.37e-01
1.44e-02
6.11e-03
5.06e-01
1.60e-02
6.07e-01
4.30e-05
1.47e-02
% of process group
total
0.01%
<0.01%
<0.01%
<0.01%
<0.01%
<0.01%
<0.01%
<0.01%
0.01%
0.01%
0.01%
0.08%
0.58%
0.01%
0.01%
0.04%
0.09%
0.65%
O.01%
0.02%
0.01%
0.01%
0.01%
0.01%
O.01%
100.00%
0.01%
0.01%
0.03%
O.01%
0.01%
O.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
% of grand
total
79.70%
2-94
-------
2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
Table 2-44. CRT manufacturing stage radioactivity outputs
Material
Process group
Cobalt-58 (isotope)
Cobalt-58 (isotope)
Cobalt-60 (isotope)
Cobalt-80 (isotope)
Iodine-131 (isotope)
Iodine-131 (isotope)
Iodine- 132 (isotope)
Iodine- 132 (isotope)
Iodine- 133 (isotope)
Iodine-133 (isotope)
Iodine- 134 (isotope)
Iodine- 135 (isotope)
Iodine-135 (isotope)
Iron-55 (isotope)
Iron-59 (isotope)
Krypton-85 (isotope)
Krypton-85M (isotope)
Krypton-85M (isotope)
Krypton-87 (isotope)
Krypton-88 (isotope)
Lanthanum- 140 (isotope)
Manganese-54 (isotope)
Manganese-54 (isotope)
Molybdenum-99 (isotope)
Niobium-95 (isotope)
Niobium-95 (isotope)
Rubidium-88 (isotope)
Ruthenium- 103 (isotope)
Silver- 110M (isotope)
Silver- 110M (isotope)
Sodium-24 (isotope)
Strontium-89 (isotope)
Strontium-90 (isotope)
Strontium-95 (isotope)
Sulfur- 136 (isotope)
Technetium-99M (isotope)
Technetium-99M (isotope)
Tin-113 (isotope)
Tritium-3 (isotope)
Tritium-3 (isotope)
Xenon-13 1M (isotope)
Xenon-13 1M (isotope)
Disposition
air
treatment
air
treatment
air
treatment
air
treatment
air
treatment
air
air
treatment
treatment
treatment
air
air
treatment
air
air
treatment
air
treatment
treatment
air
treatment
air
treatment
air
treatment
treatment
treatment
treatment
treatment
treatment
air
treatment
treatment
air
treatment
air
treatment
Quantity (Bq/
functional unit)
5.49e+01
5.98e+00
4.13e-03
1.57e+00
1.93e-02
2.80e-01
3.92e-03
1.06e-01
1.79e+01
1.20e-01
2.03e-02
1.02e-03
8.60e-02
1.43e+00
7.34e-02
4.23e+02
2.05e+01
3.78e-01
7.62e+00
3.58e+01
9.99e-03
2.27e-04
4.00e-01
7.55e+05
9.01e-06
1.036-01
8.37e-02
1.26e-02
2.69e-07
1.476-01
2.24e-02
2.42e-02
5.69e-03
6.27e-02
1.35e-02
1.21e-06
8.77e-03
1.39e-02
5.98e+02
4.47e+03
3.45e+01
4.60e+00
% of process group
total
0.01%
O.01%
O.01%
O.01%
O.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.06%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
98.41%
O.01%
O.01%
O.01%
O.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.08%
0.58%
0.01%
O.01%
% of grand
total
2-95
-------
2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
Table 2-44. CRT manufacturing stage radioactivity outputs
Material
Process group
Xenon- 13 3 (isotope)
Xenon- 13 3 (isotope)
Xenon-133M (isotope)
Xenon-133M (isotope)
Xenon- 13 5 (isotope)
Xenon-135M (isotope)
Xenon-138 (isotope)
Zinc-85 (isotope)
Zirconium-95 (isotope)
Total
Fuels
Radioactive substance (unspecified)
Radioactive substance (unspecified)
Total
Grand Total
Disposition
air
treatment
air
treatment
treatment
air
air
treatment
air
air
surface water
Quantity (Bq/
functional unit)
4.98e+03
7.07e+02
3.31e+02
5.79e+00
5.27e+00
3.59e+00
1.19e+01
6.75e-03
2.33e-05
7.67e+05
9.19e+02
8.52e+00
9.27e+02
3.78e+06
% of process group
total
0.65%
0.09%
0.04%
<0.01%
<0.01%
<0.01%
<0.01%
<0.01%
<0.01%
100.00%
99.08%
0.92%
100.00%
% of grand
total
20.27%
0.02%
100.00%
2-96
-------
2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
~ 400
5 350
To 300'
c 250
0 200
0 150-
= 100-
sg 50-
^ 0-
CRT Manufacturing - Primary Materials Inputs
374
20-1 11.9 7.0 0.9 4.8 3.1
Monitor Tube Glass/frit PWB Japanese US grid Fuels
assembly grid
CRT mfg process groups
Figure 2-24. CRT manufacturing primary inputs
CRT Manufacturing -Ancillary Materials Inputs
.*;
3
~n
o
O) 0
0.02
nqn
0.19
1.16
0.04 0.06
1.16
Monitor
asserrbly
Tube
Glass/frit
FWB
Japanese
grid
US grid
CRT mfg process groups
Figure 2-25. CRT manufacturing ancillary inputs
Fuels
CRT Manufacturing - Fuel Inputs
+; 400 -I
'c 350 -
— 300-
c 250
.9. 200 -
O 150
D 100
O) 50
-^ 0
0.1 4.9
ooo
68.9
0.4 0.0 0.0 I I
Monitor
assembly
Tube
Glass/frit
PWB
Japanese
grid
US grid
CRT mfg process groups
Figure 2-26. CRT manufacturing fuel inputs
Fuels
2-97
-------
2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
80
.° 40-
+*
o
20-1
0
13
Monitor
asserrbly
CRT Manufacturing - Electricity Inputs
74
32
10
0
0
Tube
Glass/frit
FWB
Japanese
grid
US grid
CRT mfg process groups
Figure 2-27. CRT manufacturing electricity inputs
Fuels
+J
'E
3
"5
o
o
c
J^
O)
J*:
CRT Manufacturing - Water Inputs
12000 -I
10000 -
8000-
6000-
4000-
2000-
0-
81 1
35 0 42 44 18
0,500
Monitor Tube Glass/frit FWB Japanese US grid Fuels
asserrbly grid
CRT mfg process groups
Figure 2-28. CRT manufacturing water inputs
:H 16000-,
| 14000-
— 12000-
c 10000-
.2 8000
o 6000 -
5 4000
^ 2000
^ 0
CRT Manufacturing -Total Energy
15,200
19 237
2,790
2/00 I
Monitor
assembly
Tube
Glass/frit
FWB
Japanese
grid
US grid
CRT mfg process groups
Figure 2-29. CRT manufacturing energy inputs
Fuels
2-98
-------
2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
.•H 200 -I
| 15°-
.° -mo-
ts
| 50-
*-
°> n
jtf U H
CRT Manufacturing -Air Emissions
157
0 0.03 2.9 3.9E-05 16 7-2
Monitor Tube Glass/frit FWB Japanese US grid Fuels
assembly grid
CRT mfg process groups
Figure 2-30. CRT manufacturing air emissions
.•£ 1000 -I
3
ona
800-
GOO-
'S 400 -
I 200-
kg
CRT Manufacturing -Waste water Outputs
533
894
36
42
0
Monitor
assembly
Tube
Glass/frit
FWB
Japanese
grid
US grid
Fuels
CRT mfg process groups
Figure 2-31. CRT manufacturing waste water outputs
.*; 5n
c
- 4-
I
"o
c
5 H
* o
CRT Manufacturing - Water Pollutant Outputs
4.7EtOO
O.OEtOO 1 -2E-01
1.1E-04 8.9E-04 1.1E-03 9.9E-05
Monitor
assembly
Tube
Glass/frit
FWB
Japanese
grid
US grid
CRT mfg process groups
Figure 2-32. CRT manufacturing water pollutant outputs
Fuels
2-99
-------
2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
.•s 0-8 -i
— 0.6-
g 0.5-
.2 0.4
O 0.3
| 0.2
*: 0.1
& 0.0
CRT Manufacturing - Hazardous Waste Outputs
4
O.OEtOO 1.9E-02 3.6E-02
.6E-0
e
1
O.OEtOO O.OEtOO
.2E-0
1
Monitor
assembly
Tube
Japanese
grid
US grid
Glass/frit FWB
CRT mfg process groups
Figure 2-33. CRT manufacturing hazardous waste outputs
Fuels
+- 80-,
'= 70-
f 60-
g 50-
.9. 40-
O 30-
| 20-
0
CRT Manufacturing - Solid Waste Outputs
71.9
0.5
1.9
0.4
41
1.1
1.3
Monitor
assembly
Tube
Glass/frit
FWB
Japanese
grid
US grid
CRT mfg process groups
Figure 2-34. CRT manufacturing solid waste outputs
Fuels
Among the utility inputs, both fuels and electricity were greatest in the glass/frit
manufacturing processes (Figures 2-26 and 2-27). The fuels, especially, are dominated by the
glass/frit process group, representing 83% of the mass of all the fuels in the manufacturing life-
cycle stage. It is LPG in this inventory that clearly dominates the fuel inputs at about 351
kg/functional unit (99% of the glass/frit fuel inputs) (Table 2-38). Water inputs are greatest in
the fuel production processes, contributing 1,050 kg (or liter)/functional unit (Figure 2-28).
Total energy use from manufacturing is shown in Figure 2-29. The glass/frit manufacturing
process group contributes the greatest to the total energy impacts in the manufacturing stage. A
sensitivity analysis will be conducted on the glass data and more details are provided in
Section 2.7.3.
For outputs from the manufacturing stage, the mass of air emissions are dominated by
fuel production (Figure 2-30). Individual material (pollutant) contributions for each process
group are presented in Table 2-39. Wastewater outputs (i.e., the volume or mass of wastewater
released) are also greatest from the fuel production processes (Figure 2-31; Table 2-40);
2-100
-------
2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
however, the mass of chemical pollutants in the wastewater is greatest from the glass/frit
manufacturing process group (4.65 kg/functional unit) out of the total manufacturing stage mass
of pollutants, which is 4.77 kg/functional unit (Figure 2-32; Table 2-40).
Hazardous wastes from the CRT manufacturing stage were a small portion of the overall
hazardous wastes generated by mass. Nonetheless, for purposes of future manufacturing stage
improvement assessments, Table 2-41 presents the individual material contributions for each
manufacturing process group; and Figure 2-33 shows that fuels production contributes the most
(0.62 kg/functional unit) hazardous waste to the manufacturing stage. Manufacturing solid
wastes are not as small a portion of the total mass of solid wastes throughout the CRT life-cycle
(42%) as hazardous wastes are, as was depicted in Figure 2-21. Fuels production is the greatest
contributor to manufacturing-generated solid wastes (71.9 kg/functional unit), followed by PWB
manufacturing (4.1 kg/functional unit) (Figure 2-34 and Table 2-43).
Radioactive waste and radioactivity are directly related to the electricity generation
process and therefore, only the Japanese and U.S. electric grid processes generate these outputs
(some small radioactivity outputs are generated by fuels production processes) in the
manufacturing stage. (These outputs also occur in upstream processes that have an electric grid
included in the inventory.) Tables 2-44 and 2-45 show that more radioactive wastes and
radioactivity are from the Japanese grid. This is a result of more manuf acturing processes as
modeled in this project being in Japan.
2.7.1.2 LCD inventory results
The LCD inventory is presented similar to the CRT inventory above. The total LCD
inventory presented in Table 2-24 and Figures 2-5, 2-6, and 2-7 shows the inventory from all
life-cycle stages combined. The totals by life-cycle stage are presented in Table 2-45, Figure 2-
35, Figure 2-36, and Figure 2-37.
Table 2-45. LCD inventory by life-cycle stage
Inventory type
Upstream
Mfg
Use
EOL
Total
Units*
Inputs
Primary materials
Ancillary materials
Water
Fuels
Electricity
Total energy
2.35e+02
1.06e+00
2.63e+02
??
3.46e+01
6.33e+02
4.92e+01
2.04e+02
2.15e+03
??
3.16e+02
1.44e+03
S.Ole+Ol
1.29e+00
4.25e+02
??
8.53e+02
8.53e+02
-2.19e+00
2.11e+00
-l.SOe+Ol
??
1.62e-01
-8.446+01
3.62e+02
2.08e+02
2.82e+03
O.OOe+00
1.20e+03
2.84e+03
kg
kg
kg
kg(orL)
MJ
MJ
Outputs
Air pollutants
Wastewater
Water pollutants
Hazardous waste
Solid waste
Radioactive waste
Radioactivity
1.12e+02
8.57e+00
4.60e-01
6.72e-03
1.31e+01
2.21e+01
1.20e+07
6.48e+01
3.12e+03
1.23e+00
4.64e+00
1.26e+01
3.14e+03
1.02e+07
1.68e+02
0
2.62e-02
0
3.11e+01
3.116+01
1.79e+07
1.30e+00
-2.41e+00
-4.09e-02
1.64e+00
-4.42e+00
-5.23e+00
3.40e+03
3.46e+02
3.13e+03
1.68e+00
6.29e+00
5.23e+01
3.19e+03
4.01e+07
kg
kg
kg(orL)
kg
kg
kg
Bq
*Per functional unit (i.e., one LCD monitor over its effective life)
2-101
-------
2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
LCD Materials Inputs
n Primary materials nAncillary materials n Fuels n Water
.- 2500 -,
| 2000 -
TO 1500 -
0 1000 -
tj 500-
§ 0
0) -500 -
^
2,150
263 204
0-3C ZOO
., ., 14.7 49.7 25.?
[ 11'1 1 1 c 1
n 425
80-1 o.orn 8-9 Z1
-2.0
Upstream Mfg Use EOL -18.0
Life-cycle stage
Figure 2-35. LCD mass-based material inputs by life-cycle stage
.•s 2000-,
c
_f 1500-
| 1000-1
'•§ 500 -
c
5 o
-500 -
34.6
Upstream
LCD Energy Inputs
H Bectricity n Total energy
1,440
316
853 853
Mfg Use
Life-cycle stage
0.2
EOL -84.4
Figure 2-36. LCD energy-based inputs by life-cycle stage
LCD Inventory Outputs
n Air pollutants n Water pollutants n Hazardous w aste n Solid w aste • Radioactive w aste
5> -50-1
168
Upstream
Mfg Use
Life-cycle stage
Figure 2-37. LCD mass-based material outputs by life-cycle stage
2-102
-------
2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
Considering inputs, Figure 2-35 shows that of the inputs measured in mass, the water
inputs constitute the majority of the inputs by mass for the entire life cycle, and most of the
water inputs are in the manufacturing life-cycle stage. Details on each inventory type are
provided below. When considering which life-cycle stage contributes most to an inventory
category, the manufacturing stage has the largest inventory by mass for ancillary materials, fuels,
and water inputs. Primary material inputs are dominated by the upstream stages while electricity
inputs are dominated by the use stage. The total energy is dominated by the manufacturing life-
cycle stage (Figure 2-36). Note that LPG production from glass manufacturing does not
dominate much of the LCD inventory as it did for the CRT because of the smaller amount of
glass used in the LCD compared to the CRT.
Of the outputs measured in mass (air emissions, wastewater, water pollutants and
hazardous, solid, and radioactive waste), wastewater constitutes the greatest output (Table 2-46);
however, wastewater alone is not used to calculate impacts. Instead, water pollutants are used to
calculate impacts and therefore listed separately in the inventory. Of the remaining outputs
measured in mass (i.e., air emissions, water pollutants and hazardous, solid and radioactive
waste), which are shown in Figure 2-37, air emissions are the greatest contributor to the outputs.
Note again, as mentioned for the CRT, that radioactivity is measured in Bequerels (Bq) and
cannot be compared on the same scale.
Considering each output type and their contributions by life-cycle stage, the mass of
water pollutants is greatest in the manufacturing life-cycle stage, due to the fuel production
processes that support fuel consumption in the manufacturing processes being included in the
manufacturing life-cycle stage. Wastewater and hazardous waste outputs are greatest in the
manufacturing stage; air emissions, solid waste, radioactive waste, and radioactivity have the
greatest contribution from the use stage. As with the CRT, all the output totals represented in
Table 2-45 include outputs to all dispositions.
The tables and figures discussed above show the total inventories for particular input or
output types by life-cycle stage. Tables in Appendix J list each material that contributes to those
totals. Figures 2-38 through 2-50 show the total contribution by life-cycle stage, based on the
entire input/output type-specific tables in Appendix J. Summary tables for the LCD (Tables 2-
46 through 2-54), developed from the Tables in Appendix J, show the top contributing inventory
items to each input or output type. Note that Table 2-48 includes input/output types that are
classified together as utilities: water, fuel, electricity and total energy.
LCD Primary Inputs
Figure 2-38 shows that most LCD primary materials by mass are from the upstream life-
cycle stages. The top 99.9% of the materials contributing to the total LCD primary input
inventory are shown in Table 2-46. The largest material contributors are natural gas, coal and
petroleum (a combined 89% of all the primary LCD inputs), which are used to generate
electricity consumed throughout the life-cycle of the monitor. Most of the electricity consumed
in the LCD life-cycle is in the manufacturing and use stages, as was seen in Figure 2-36.
However, most of the natural gas primary material reported in the materials processing stage
(229 kg/functional unit) is not used to generate electricity, but is an ancillary material in the LCD
monitor/module manufacturing process. More detail on the processes that contribute greatest
within the manufacturing stage will be presented after brief discussions of the life-cycle stage
breakdowns for each inventory type. For the complete list of primary materials in the LCD
2-103
-------
2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
inventory, the total mass, and the mass contribution of each life-cycle stage, see Appendix J,
Table J-10.
250 -,
c 200 -
re 150-
c
.2. 100-1
c 50-1
,E
o
o.
235
LCD - Primary Materials
80
50
-2.2
-50-1 Upstream Mfg Use EOL
Life-cycle stage
Figure 2-38. LCD primary material inputs by life-cycle stage
1 250
.f 200-
re
= 150-^
O
'•5 100-1
5 50-
1" o
1.1
LCD -Ancillary Materials
204
1.3
2.1
Upstream
Mlg Use
Life-cycle stage
EOL
Figure 2-39. LCD ancillary material inputs by life-cycle stage
2-104
-------
2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
/functional unit
-^ -^ NJ NJ GO
D Gn o Gn o Gn o
O) "
* -5\
15
LCD - Fuels
26
Upstream Mlg
Li
Figure 2-40. LCD
0.0 -2.0
i i [ | i
Use EOL
fe -cycle stage
fuel inputs by life-cycle stage
J/functional unit
W J^ CD 00 O
= 88888
LCD - Electricity
853
316
34.6 0.2
1 1 1 1
Upstream Mfg Use EOL
Life -cycle stage
Figure 2-41. LCD electricity inputs by life-cycle stage
^ 2000
i 1500
c 1000
O
tj 500
I o
-500-I
LCD -Total Energy
633
1,440
853
-84
Upstream Mlg Use EOL
Life-cycle stage
Figure 2-42. LCD energy inputs by life-cycle stage
2-105
-------
2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
re
2500-I
2000-
1500-
1000-
500-
-500-1
LCD-Water Inputs
263
1 1
Z, IOU
425
1 -'°
i i i i
1 ln«;trpam Mfn 1 I«:P FDI
Life-cycle stage
Figure 2-43. LCD water inputs by life-cycle stage
C 200 n
75
c
.2 100-
+J
o
LCD-Air Pollutants
To treatment
D To air
0.0
112
1.4E-04
65
0.0
1 00
o.o 13
Upstream Mfg Use
Life-cycle stage
Figure 2-44. LCD air outputs by life-cycle stage
EOL
~ 3000 i
= 2500-
g 2000 -
.2 1500-
1 1000-
,= 500-
"~T 0 •
0) -500 -
LC
8.6 0
ID - Wastewater Outputs
2,524
D To surf ace water
n To treatment
597
1 o o -Z4 o
1 1 1 1
1 l^«*^.««« RA£n 1 l«« ^/"\l
Upstream
Mfg Use
Life-cycle stage
EOL
Figure 2-45. LCD wastewater outputs by life-cycle stage
2-106
-------
2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
LCD -Water Pollutants
'E
f 1 -
re
c
.2 1 -
o
i o-
^>
•* -1 -i
0.46
0.00
i
Upstream
1.11
°'13 0.00 0.03
i i
Mfg Use
Life-cycle stage
• To surface w ater
n To treatment
.0.04 4.97E-06
EOL
i
Figure 2-46. LCD water pollutant outputs by life-cycle stage
= 4n
15 3 •
§ 2-
2
LCD - Hazardous Waste
iTo landfill rjTo recycling/reuse rjTo treatment nTo land (other)
o
o o o o
o o o o
0)
0
0
00
CO
CO
o o o o o
o o o o o
CD
o o o
o o o
Upstream
Mfg Use
Life-cycle stage
EOL
Rgure 2-47. LCD hazardous waste outputs by life-cycle stage
2-107
-------
2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
Functional unit
->• NJ CO -ts.
D O O O O
O)
* -10 J
LCD -Sohd Waste DTo landfill
nTo recycling/reuse
31.1 nTo treatment
10.2
/M 59
2.9 46E.04 44 2.3 J.025 0.030 0.3 _g g 1.95
Upstream Mfg Use EOT
Life-cycle stage
Figure 2-48. LCD solid waste outputs by life-cycle stage
c 1.E-03-,
— 8.E-04-
ra
g 6.E-04-
+= 4.E-04-
§ 2.E-04-
•~ n F+nn -
LCD - Radioactive Waste
(all to landfill)
8.5E-04
4.9E-04
1.4E-04
I I
1.6E-07
1 1 1 1
Upstream Mfg Use EOL
Life-cycle stage
Figure 2-49. LCD radioactive waste outputs by life-cycle stage
*- 2.E+07 -i
i 2.E+07 •
"to
= 1.E+07-
o
o 5.E+06 -
£
LCD - Radioactivity £
LU
|^ CO
°, °
O) LU
OOO O QO O O
LULULLJ LU LLJLLJ LU LU
Oi-OO O T-CN O O
OCOM- o T-CN o o
O T— ^- O ^-(J) O O
D To landfill
n To treatment
n To surface w ater
n To air
"^ o CO CN •<-
0 0 0 0 0
+ + + ' +
UJ LU LU ^ LU
CO o Is- S- CO
CD 0 CO . 0)
^ 0 CO V CN
m -5.E+06-I Upstream Mlg Use EOL
Life-cycle stage
Figure 2-50. LCD radioactivity outputs by life-cycle stage
2-108
-------
2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
Table 2-46. Top 99.9% of LCD
Material
Natural gas (in ground)
Coal, average (in ground)
Petroleum (in ground)
Natural gas
Assembled LCD monitor
Iron (Fe, ore)
Steel
Assembled 15" LCD backlight unit
LCD module
Polycarbonate resin
Bauxite (A12O3, ore)
Iron scrap
LCD glass
Poly(methyl methacrylate)
15" LCD light guide
PWB -laminate
Printed wiring board (PWB)
Styrene-butadiene copolymers
PPE
Cables/wires
LCD front glass (with color filters)
Aluminum (elemental)
Sand
Recycled LCD glass
Upstream
2.29E+02
1.72E+00
7.09E-01
0
0
3.26E+00
0
0
0
0
0
4.63E-01
0
0
0
0
0
0
0
0
0
0
0
0
primary material inputs (kg/functional unit)
Mfg
5.16E+00
8.03E+00
2.23E+01
4.22E+00
0
0
2.53E+00
1.48E+00
1.18E+00
5.16E-01
5.09E-01
0
4.52E-01
3.83E-01
3.74E-01
3.74E-01
3.74E-01
3.62E-01
3.00E-01
2.34E-01
1.78E-01
1.34E-01
1.11E-01
9.54E-02
Use
0
6.69E+01
1.42E+00
5.22E+00
6.50E+00
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
EOL
-1.08E+00
1.27E-02
-l.OOE+00
-5.75E-02
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Total
2.33E+02
7.67E+01
2.34E+01
9.39E+00
6.50E+00
3.26E+00
2.53E+00
1.48E+00
1.18E+00
5.16E-01
5.09E-01
4.63E-01
4.52E-01
3.83E-01
3.74E-01
3.74E-01
3.74E-01
3.62E-01
3.00E-01
2.34E-01
1.78E-01
1.34E-01
1.11E-01
9.54E-02
% of total
64.25%
21.15%
6.45%
2.59%
1.79%
0.90%
0.70%
0.41%
0.33%
0.14%
0.14%
0.13%
0.12%
0.11%
0.10%
0.10%
0.10%
0.10%
0.08%
0.06%
0.05%
0.04%
0.03%
0.03%
LCD Ancillary Inputs
As presented in Figure 2-39, the greatest mass of ancillary LCD inputs is in the
manufacturing life-cycle stage at approximately 204 kg/functional unit. Table 2-47 shows that
liquified natural gas (LNG) contributes about 93% to this total. It is in the LCD module/monitor
manufacturing process where this large amount of LNG was reported as an ancillary material (to
be discussed below). Note that this is separate from LNG reported as a fuel, and LNG as an
ancillary material is not used to calculate energy impacts in the LCIA. Following LNG is
nitrogen at about 3% and clay at less than 1% of the total ancillary materials by mass. Excluding
LNG from the inventory, nitrogen constitutes about 50% and clay 14% of the total ancillary
materials in the LCD life-cycle. The contributions from the manufacturing stage will be
discussed in further detail below. See Table J-l 1 in Appendix J for the complete list of ancillary
materials in the LCD inventory.
2-109
-------
2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
Table 2-47. Top 99% of LCD ancillary material inputs (kg/functional unit)
Material
LNG
Nitrogen
Clay (in ground)
Limestone
Sand (in ground)
Sodium hydroxide
Hydrogen
Lime
Sodium chloride (NaCl, in ground or sea)
Limestone (CaCO3, in ground)
Isopropyl alcohol
Sulfuric acid
Upstream
0
0
1.30e-03
0
9.55e-03
0
0
0
4.37e-01
5.07e-01
0
0
Mfg
1.94e+02
6.02e+00
0
l.OSe-01
1.32e-03
4.45e-01
4.44e-01
4.74e-02
6.08e-04
5.49e-02
3.49e-01
3.25e-01
Use
0
0
0
8.99e-01
0
0
0
3.95e-01
0
0
0
0
EOL
0
0
1.69e+00
1.71e-04
5.60e-01
0
0
7.49e-05
1.08e-05
-1.55e-01
0
0
Total
1.94e+02
6.02e+00
1.69e+00
l.Ole+00
5.71e-01
4.45e-01
4.44e-01
4.42e-01
4.38e-01
4.06e-01
3.49e-01
3.25e-01
% of total
93.19%
2.89%
0.81%
0.48%
0.27%
0.21%
0.21%
0.21%
0.21%
0.20%
0.17%
0.16%
LCD Utility Inputs
Utility inputs in the LCD life-cycle are presented in Table 2-48 and include fuel
(kg/functional unit), electricity (MJ/functional unit), water inputs (kg or L/functional unit), and
total energy (MJ/functional unit; a combination of fuel and electricity inputs). Table 2-48 and
Figure 2-40 show that most fuels (26 kg/functional unit) are used in the manufacturing stage.
This represents 67% of the total fuels. LPG (16.8 kg/functional unit) dominates the total fuel
inputs at 44% of all the fuels in the LCD life-cycle. More detail as to the breakdown by process
within the manufacturing stage will be presented below after each input/output type is discussed.
Electricity inputs are dominated by the use stage (853 MJ/functional unit), followed by
the manufacturing stage (316 MJ/functional unit) (see Figure 2-41). When fuel energy and
electrical energy are combined into a total energy input value, the overall energy from
manufacturing exceeds that from the use stage (1,440 MJ/functional unit versus 853
MJ/functional unit). This is also depicted in Figure 2-42.
The other utility considered in Table 2-48 is water (Figure 2-43). Approximately 76%
(2,150 L/functional unit) of the water inputs in the LCD life-cycle are from the manufacturing
processes. The life-cycle stage contributing the next most to water inputs is the use stage at 15%
(425 L/functional unit). The upstream contributes about 9% (263 L/functional unit). Table J-12
in Appendix J provides the complete list of inventory items for the LCD.
2-110
-------
2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
Table 2-48. LCD utility inputs
Material
Upstream
Mfg
Use
EOL
Total
% of total
Fuels (kg/functional unit):
LPG
Natural gas (in ground)
LNG
Coal, average (in ground)
Petroleum (in ground)
Kerosene
Coal, lignite (in ground)
Natural gas
Steam
Fuel oil #6
Fuel oil #2
Uranium (U, ore)
Fuel oil #4
Total fuels
0
1.03E+01
0
2.49E+00
1.52E+00
0
4.10E-01
0
0
0
0
7.86E-05
0
1.47E+01
1.68E+01
2.41E+00
3.22E+00
6.86E-01
4.84E-01
4.65E-01
0
1.16E+00
1.45E-01
1.25E-01
5.42E-02
1.15E-05
2.11E-01
2.58e+01
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1.38E-03
-1.38E-01
0
-7.66e-03
-3.81e-02
0
0
-8.61E-01
0
0
0
0
-9.09e-01
-1.95E+00
1.68E+01
1.26E+01
3.22E+00
3.17E+00
1.96e+00
4.65e-01
4.10e-01
S.Ole-Ol
1.456-01
1.25e-01
5.42e-02
9.01e-05
-6.996-01
3.86e+01
43.63%
32.66%
8.34%
8.21%
5.08%
1.21%
1.06%
0.78%
0.37%
0.33%
0.14%
<0.01%
-1.81%
100.00%
Electricity (MJ/functional unit):
Electricity
3.46e+01
3.16e+02
8.53e+02
1.62e-01
1.20e+03
Water (kg or L/functional unit):
Water
Total energy (fuels and electricity,
Energy
2.63E+02
2.15E+03
4.25E+02
-1.80E+01
2.82e+03
MJ/functional unit):
6.33E+02
1.44E+03
8.53E+02
-8.44E+01
2.84E+03
LCD Air Outputs
Air emissions from the LCD life-cycle are greatest (by mass) in the use stage as seen in
Figure 2-44. This indicates that most air emissions by mass are from the generation of electricity
used by consumers of the monitors. Forty-nine percent of the total life-cycle air emissions by
mass (or about 168 kg/functional unit) are from the use stage. Carbon dioxide (CO2) emissions
from the use stage alone constitute about 166 kg/functional unit, or almost 48% of all air
emissions by mass in the life-cycle and nearly 99% of the use stage air emissions. The
remaining air emissions that contribute to the top 99.99% of air emissions are presented in Table
2-49 and the complete list of air emissions are presented alphabetically in Table J-13 in
Appendix J. The appendix also provides life-cycle stage subtotals. The next largest air
emissions, by life-cycle stage, are emitted during the upstream stages, which contribute about
32% to the total life-cycle air emissions. All the air emissions in the inventory except for
ethylacetate and methyl ethyl ketone from the manufacturing stage (a combined 1.36 x 10"4
kg/functional unit) were reported as being emitted directly to the air (see Appendix J, Table J-
13). Only those materials directly released to the air are used to calculate impacts. This will be
discussed further in Chapter 3.
2-111
-------
2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
Table 2-49. Top 99.99% of LCD air emissions (kg/functional unit)
Material
Carbon dioxide
Methane
Nitrogen oxides
Sulfur dioxide
Tetramethyl ammonium
Other organics
Carbon monoxide
Nitrogen fluoride
Nonmethane hydrocarbons
Hydrochloric acid
Benzene
PM
Ammonia
Phosphine
Hydrofluoric acid
Sulfur oxides
Unspecified LCD process
Cr-etchant, unspecified
Nitrogen dioxide
PM-10
Isopropyl alcohol
Hydrocarbons, remaining
Al-etchant unspecified
Disposition
Air
Air
Air
Air
Air
Air
Air
Air
Air
Air
Air
Air
Air
Air
Air
Air
Air
Air
Air
Air
Air
Air
Air
Upstream
1.07e+02
3.54e+00
6.56e-01
4.63e-02
0
4.45e-01
3.74e-01
0
2.07e-01
1.50e-03
8.85e-02
9.16e-02
1.12e-02
0
2.27e-04
2.57e-02
0
0
3.08e-02
3.45e-07
0
9.30e-03
0
Mfg
6.22e+01
1.22e-01
7.62e-01
2.95e-01
6.43e-01
1.35e-02
3.85e-02
2.45e-01
8.87e-03
6.58e-02
2.70e-03
6.99e-03
6.26e-02
6.26e-02
5.27e-02
4.07e-02
4.49e-02
4.12e-02
0
6.85e-03
1.78e-02
7.75e-03
1.37e-02
Use
1.66e+02
2.41e-01
4.39e-01
9.30e-01
0
0
3.02e-02
0
0
4.02e-02
4.36e-05
0
0
0
5.02e-03
0
0
0
0
2.16e-02
0
0
0
EOL
1.39e+00
-2.82e-02
-1.36e-02
2.96e-04
0
-2.41e-03
-3.45e-03
0
-1.26e-03
-6.88e-04
-4.82e-04
-1.246-02
-6.95e-05
0
-1.476-04
-1.93e-02
0
0
4.46e-04
3.43e-06
0
-6.51e-04
0
Total
3.36e+02
3.87e+00
1.84e+00
1.27e+00
6.43e-01
4.56e-01
4.39e-01
2.45e-01
2.15e-01
1.076-01
9.07e-02
8.62e-02
7.37e-02
6.26e-02
5.78e-02
4.71e-02
4.49e-02
4.12e-02
3.12e-02
2.84e-02
1.78e-02
1.64e-02
1.37e-02
% of total
97.18%
1.12%
0.53%
0.37%
0.19%
0.13%
0.13%
0.07%
0.06%
0.03%
0.03%
0.02%
0.02%
0.02%
0.02%
0.01%
0.01%
0.01%
<0.01%
<0.01%
<0.01%
<0.01%
<0.01%
LCD Water Outputs
The volume (or mass) of wastewater released throughout the LCD life-cycle is
approximately 3,128 L (kg) per functional unit. Approximately 19% of that is sent to treatment
as opposed to direct discharge to surface water (81%; Figure 2-45). The mass of chemical
pollutants within the wastewater streams were calculated separately from the total wastewater
volume. The total mass of water pollutants released, presented by life-cycle stage are shown in
Figure 2-46. Of the small amount of water pollutants released, the manufacturing life-cycle
stage contributes the greatest with approximately 1.23 kg per functional unit. This is about 73%
of all the water pollutants for the entire life-cycle. The upstream stages have the second greatest
mass of water pollutants at nearly 0.46 kg/functional unit (27%). The use and EOL stages are
small contributors, with the EOL being negative due to recovery processes within the EOL stage.
To see the top 99% contributors to the water pollutant quantities, Table 2-50 reveals that
chloride and sodium ions contribute nearly 61% to all the water pollutants in the life-cycle,
mostly from the manufacturing and upstream stages. For the complete inventory, listing water
pollutants alphabetically and by life-cycle stage, see Appendix J, Table J-14. Further details on
the manufacturing stage will be provided later.
2-112
-------
2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
Table 2-50. To
) 99% of LCD water pollutant outputs (kg/functional unit)
Material
Chloride ions
Sodium (+1)
Dissolved solids
COD
Nitrogen
Suspended solids
BOD
COD
BOD
Sulfate ion (-4)
Sulfate ion (-4)
Fluorides (F-)
Nitrogen
Phosphorus (yellow or white)
Waste oil
Suspended solids
Phosphorus (yellow or white)
Colon bacillus (bacteria in
large intestine)
Oil & grease
Disposition
surface water
surface water
surface water
surface water
surface water
surface water
treatment
treatment
surface water
surface water
treatment
surface water
treatment
treatment
surface water
treatment
surface water
surface water
treatment
Upstream
2.33e-01
1.73e-01
3.21e-03
7.67e-03
1.44e-05
4.98e-03
0
0
7.72e-04
2.40e-02
0
5.14e-05
0
0
1.75e-03
0
1.92e-06
0
0
Mfg
3.12e-01
3.41e-01
1.756-01
8.20e-02
7.98e-02
5.80e-02
5.74e-02
3.90e-02
2.79e-02
2.94e-03
1.32e-04
1.29e-02
1.26e-02
6.91e-03
4.87e-03
5.60e-03
4.33e-03
3.89e-03
3.61e-03
Use
0
0
0
0
0
0
0
0
0
0
2.55e-02
0
0
0
0
6.65e-04
0
0
0
EOL
-1.58e-02
-2.03e-02
-5.69e-05
-2.69e-03
0
-1.44e-03
0
0
-3.18e-04
-1.20e-06
4.84e-06
-5.01e-06
0
0
-2.06e-04
1.26e-07
0
0
0
Total
5.29e-01
4.94e-01
1.786-01
8.70e-02
7.98e-02
6.15e-02
5.74e-02
3.90e-02
2.83e-02
2.69e-02
2.57e-02
1.30e-02
1.26e-02
6.91e-03
6.41e-03
6.26e-03
4.33e-03
3.89e-03
3.61e-03
% of total
31.53%
29.42%
10.63%
5.18%
4.76%
3.66%
3.42%
2.33%
1.69%
1.60%
1.53%
0.77%
0.75%
0.41%
0.38%
0.37%
0.26%
0.23%
0.21%
LCD Hazardous Waste Outputs
The total mass of hazardous waste generated throughout the life-cycle of the LCD is
about 6.29 kg/functional unit. Figure 2-47 shows that this is mostly from the manufacturing
stage, which contributes 4.64 kg/functional unit, or almost 74%. The EOL stage hazardous
waste outputs equal 1.64 kg/functional unit, or 26%. The disposition of the waste will be used to
determine how impacts are calculated in Chapter 3. Only hazardous wastes sent to landfills are
directly calculated as impacts, which will be presented and discussed in Chapter 3. Figure 2-47
shows what portion of hazardous wastes are landfilled, recycled/reused, treated or otherwise
land-applied. Nearly all of the hazardous waste in the manufacturing stage (-99%) is
recycled/reused or treated. Less than 1% of the hazardous waste from the manufacturing stage is
landfilled. Nearly all the hazardous waste from the EOL stage is landfilled. Table 2-51 shows
the top contributors to the LCD life-cycle. Note that multiple entries of a material are due to
different dispositions for that material. See Table J-15 in Appendix J for the complete
alphabetical inventory of hazardous waste outputs. Additional detail on the manufacturing stage
are presented below.
2-113
-------
2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
Table 2-51. Top 99% of LCD hazardous waste outputs (kg/functional unit)
Material
Isopropyl alcohol
EOL LCD Monitor, landfilled
Waste acid (mainly HF)
Thinner, unspecified
Remover, unspecified
Sodium sulfate
Isopropyl alcohol
Tetramethyl ammonium
hydroxide
Waste acid (mainly HF)
PWB-Waste cupric etchant
Remover, unspecified
Hazardous waste, unspecified
Rinse, unspecified
Spent solvent (non-halogenated)
Hazardous waste, unspecified
Waste acids, unspecified
Unspecified sludge
PWB-Solder dross
Acetone
Waste solvent (photoresist)
Waste solvent (photoresist)
Spent solvent (with halogenated
materials)
Phosphoric acid
Disposition
treatment
landfill
recycling/reuse
treatment
treatment
recycling/reuse
recycling/reuse
recycling/reuse
treatment
recycling/reuse
recycling/reuse
treatment
recycling/reuse
treatment
landfill
recycling/reuse
land (other than
landfill)
recycling/reuse
treatment
treatment
recycling/reuse
treatment
landfill
Upstream
0
0
0
0
0
0
0
0
0
0
0
0
0
0
6.72E-03
0
0
0
0
0
0
0
0
Mfg
1.91E+00
0
5.69E-01
5.40E-01
3.03E-01
2.44E-01
1.69E-01
1.42E-01
1.36E-01
9.93E-02
8.84E-02
6.16E-02
4.67E-02
4.66E-02
2.97E-02
3.24E-02
3.09E-02
2.96E-02
2.77E-02
2.17E-02
2.05E-02
1.55E-02
1.44E-02
Use
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
EOL
0
1.64E+00
0
0
0
0
0
0
0
0
0
0
0
0
-1.05E-03
0
0
0
0
0
0
0
0
Total
1.91E+00
1.64E+00
5.69E-01
5.40E-01
3.03E-01
2.44E-01
1.69E-01
1.42E-01
1.36E-01
9.93E-02
8.84E-02
6.16E-02
4.67E-02
4.66E-02
3.54E-02
3.24E-02
3.09E-02
2.96E-02
2.77E-02
2.17E-02
2.05E-02
1.55E-02
1.44E-02
%of
total
30.41%
26.13%
9.04%
8.57%
4.81%
3.89%
2.69%
2.26%
2.15%
1.58%
1.40%
0.98%
0.74%
0.74%
0.56%
0.52%
0.49%
0.47%
0.44%
0.35%
0.33%
0.25%
0.23%
LCD Solid Waste Outputs
Figure 2-48 shows that the use stage contributes the most amount (31 kg/functional unit)
of solid waste by mass to the LCD life-cycle, and 100% of that waste is landfilled. The
manufacturing stage contributes 12.6 kg/functional unit. In terms of mass, the greatest material
contributors to the solid waste outputs for the LCD life-cycle are coal waste (-41%), followed by
dust/sludge (16%). Most of this is from the generation of electricity in the use stage (Table 2-
52). Note also that the mass of an LCD monitor that is assumed to be landfilled (0.89
kg/functional unit) is 1.7% of the total mass of solid waste in the LCD life-cycle. See Appendix
J, Table J-16 for the complete LCD solid waste inventory. The manufacturing stage breakdown
will be discussed at the end of this section.
2-114
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2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
Table 2-52. Top 99% of LCD solid waste outputs (kg/functional unit)
Material
Coal waste
Dust/sludge
Fly /bottom ash
Unspecified solid waste
Slag and ash
Unspecified solid waste
Unspecified solid waste
Iron scrap
EOL LCD Monitor,
incinerated
EOL LCD Monitor, recycled
EOL LCD Monitor,
remanufactured
EOL LCD Monitor, landfilled
Unspecified sludge
Waste LCD glass
Unspecified waste
CARBON STEEL SCRAP
Waste plastic from LCD
modules
Polycarbonate
Waste alkali, unspecified
Waste acid (containing F and
detergents)
Waste LCD glass
Mineral waste
Mining waste
Slag and ash
Waste acids, unspecified
Mixed industrial (waste)
Waste alkali (color filter
developer, unspecified)
Disposition
landfill
landfill
landfill
landfill
recycle/reuse
recycle/reuse
treatment
recycle/reuse
treatment
recycle/reuse
recycle/reuse
landfill
recycle/reuse
recycle/reuse
recycle/reuse
recycle/reuse
treatment
recycle/reuse
recycle/reuse
landfill
landfill
landfill
landfill
landfill
treatment
landfill
recycle/reuse
Upstream
0
0
0
2.40E+00
8.02E+00
1.50E+00
0
1.67E-01
0
0
0
0
0
0
4.05E-01
0
0
0
0
0
0
2.20E-01
1.41E-01
8.19E-02
0
4.34E-02
0
Mfg
2.28E+00
8.80E-01
5.70E-01
0
3.40E+00
2.11E-01
1.63E+00
0
0
0
0
0
8.46E-01
7.20E-01
1.72E-01
0
4.03E-01
0
3.23E-01
2.70E-01
2.63E-01
1.26E-04
0
3.49E-02
1.05E-01
4.83E-02
8.91E-02
Use
1.90E+01
7.34E+00
4.75E+00
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
EOL
3.60E-03
1.39E-03
9.01E-04
-5.10E-01
-9.67E+00
0
0
1.10E+00
9.75E-01
9.75E-01
9.75E-01
8.94E-01
0
0
-9.83E-03
4.58E-01
0
3.90E-01
0
0
0
-4.46E-06
-1.23E-06
-1.99E-03
0
-1.35E-03
0
Total
2.13E+01
8.23E+00
5.32E+00
1.89E+00
1.75E+00
1.71E+00
1.63E+00
1.27E+00
9.75E-01
9.75E-01
9.75E-01
8.94E-01
8.46E-01
7.20E-01
5.67E-01
4.58E-01
4.03E-01
3.90E-01
3.23E-01
2.70E-01
2.63E-01
2.21E-01
1.41E-01
1.15E-01
1.05E-01
9.04E-02
8.91E-02
%of
total
40.64%
15.72%
10.16%
3.62%
3.35%
3.27%
3.11%
2.42%
1.86%
1.86%
1.86%
1.71%
1.62%
1.38%
1.08%
0.88%
0.77%
0.75%
0.62%
0.52%
0.50%
0.42%
0.27%
0.22%
0.20%
0.17%
0.17%
LCD Radioactive Waste Outputs
Radioactive waste outputs in the LCD inventory are limited to the electricity generation
and steel production processes, with steel production processes accounting for only about 9% of
the total. Therefore, radioactive wastes will be found wherever electricity is used in a process in
the LCD life-cycle. Only very small amounts (approximately 0.0015 kg/functional unit) of
radioactive waste are generated over the entire life-cycle of the LCD (Figure 2-49 and Table 2-
53). As expected, the majority of this is linked to the use stage, where most electricity is used in
the LCD life-cycle, followed by the manufacturing stage. Low-level radioactive waste (78%)
and depleted uranium (21%) are most of the waste, with negligible amounts of highly radioactive
waste and unspecified radioactive waste. The inventory of radioactive waste outputs is small,
2-115
-------
2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
and therefore, Table 2-53 lists all material outputs associated with radioactive waste, in
descending order of quantity. Table J-17 in Appendix J lists these in alphabetical order.
Table 2-53. LCD radioactive waste outputs (kg/functional unit)
Material
Low-level radioactive waste
Uranium, depleted
Radioactive waste (unspecified)
Highly radioactive waste (Class C)
Total radioactive wastes
Disposition
landfill
landfill
landfill
landfill
Upstream
1.28E-04
0
5.77E-06
2.72E-06
1.37E-04
Mfg
3.74E-04
1.12E-04
0
0
4.87E-04
Use
6.56E-04
1.97E-04
0
0
8.52E-04
EOL
1.24E-07
3.73E-08
0
0
1.62E-07
Total
1.16E-03
3.09E-04
5.77E-06
2.72E-06
1.48E-03
%of
total
78.49%
20.93%
0.39%
0.18%
100.00%
LCD Radioactivity Outputs
Radioactivity is also inventoried in this project as isotopes that are released to the
environment. Radioactivity is measured in Bequerels and may be released to air, water, or land,
or may also be treated. The quantity of radioactivity for each life-cycle stage and different
dispositions are presented in Figure 2-50. Table 2-54 shows the top contributors to the total
radioactivity outputs. Radioactivity outputs are associated with the generation of electricity and,
therefore, the greatest quantity of radioactivity is from the use stage. Appendix J, Table J-18
lists the complete inventory.
Table 2-54. Top 99.9% of LCD radioactivity outputs (Bq/functional unit)
Material
Molybdenum-99 (isotope)
Plutonium-241 (isotope)
Tritium-3 (isotope)
Xenon- 13 3 (isotope)
Xenon-133M (isotope)
Plutonium-240 (isotope)
Cesium-135 (isotope)
Radon-222 (isotope)
Plutonium-239 (isotope)
Xenon- 13 3 (isotope)
Tritium-3 (isotope)
Krypton-85 (isotope)
Disposition
treatment
landfill
treatment
air
air
landfill
landfill
air
landfill
treatment
air
air
Upstream
0
1.18e+07
0
7.63e+02
0
5.08e+04
4.59e+04
4.30e+04
3.57e+04
0
1.09e+02
5.45e+01
Mfg.
l.Ole+07
0
5.96e+04
4.98e+03
6.59e+04
0
0
0
0
9.43e+03
7.98e+03
5.64e+03
Use
1.76e+07
0
1.04e+05
1.16e+05
7.73e+03
0
0
0
0
1.65e+04
1.40e+04
9.88e+03
EOL
3.35e+03
0
1.98e+01
2.21e+01
1.47e+00
0
0
0
0
3.13e+00
2.65e+00
1.88e+00
Total
2.77e+07
1. 18e+07
1.64e+05
1.22e+05
7.36e+04
5.08e+04
4.59e+04
4.30e+04
3.57e+04
2.60e+04
2.21e+04
1.56e+04
% of total
69.09%
29.33%
0.41%
0.30%
0.18%
0.13%
0.11%
0.11%
0.09%
0.06%
0.05%
0.04%
2-116
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2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
LCD Manufacturing Stage
The inventory tables that show the specific materials in each inventory (i.e., those in
Appendix J and Tables 2-46 through 2-54) are the sums of the materials from one or more
processes within a life-cycle stage. To burrow down deeper into the data, the manufacturing
stage inventory data are broken down by process or group of processes. Similar to the CRT
analysis, groups of processes were combined where fewer than three companies provided data
for a process or where confidentiality agreements precluded presenting individual process data
(Table 2-55). Burrowing further into the contributing processes or process groups is necessary
for future manufacturing improvement assessments.
Table 2-55. LCD process groups
Process group
Monitor/module
Panel components
LCD glass
Backlight
PWB
Japanese grid
U.S. grid
Fuels
Process(es) included
panel/module manufacturing, monitor assembly
polarizer manufacturing, patterning color filters on glass, liquid crystal manufacturing
LCD glass manufacturing
backlight unit assembly, backlight light guide, cold cathode fluorescent lamp manufacturing
PWB manufacturing
electricity generation - Japanese electric grid
electricity generation - U.S. electric grid
production of fuel oils #2, #4 and #6, LPG, and natural gas
Tables 2-56 through 2-64 list the specific inventories for each process group in the
manufacturing stage for each input and output type. Figures 2-51 through 2-61 graph the total
inventories for each process group for each input and output type. As revealed in Table 2-45,
ancillary material inputs, fuels, water and total energy inputs all were greatest in the
manufacturing stage. Similarly, wastewater, water pollutant and hazardous waste outputs were
also greatest in the manufacturing stage. Similar to the discussion for CRTs, the manufacturing
stage inventories by process group, for all input and output types, are presented here to reveal
more specifics about the inventory and to allow manufacturers to conduct improvement
assessments.
2-117
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2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
Table 2-56. LCD manufacturing stage primary material inputs
Material
Process Group
Module/Monitor
1,4-butanolide
1 -methyl-2-pyrrolidinone
2-(2-butoxyethoxy)-ethanol acetate
AINd
Aluminum (elemental)
Assembled 15" LCD backlight unit
Cables/wires
Glycol ethers
Indium tin oxide
LCD front glass (with color filters)
LCD glass
LCD material (confidential)
LCD module
LCD spacers, unspecified
Liquid crystals, for 15" LCD
Mild fiber
Molybdenum
MoW
Polarizer
Polycarbonate resin
Polyimide alignment layer, unspecified
PPE
Printed wiring board (PWB)
Solder (60% tin, 40% lead)
Steel
Styrene-butadiene copolymers
Titanium
Triallyl isocyanurate
Triphenyl phosphate
Unspecified LCD material
Total
Panel Components
3,4,5-trifluorobromobenzene
3 ,4-difluorobromobenzene
4-4(-propylcyclohexyl)cyclohexanone
4-bromophenol
4-ethylphenol
4-pentylphenol
4-propionylphenol
LCD glass
Pigment color resist, unspecified
Quantity (kg/
functional unit)
4.06e-04
4.06e-04
8.08e-06
2.97e-05
l.Ole-01
1.48e+00
2.30e-01
4.06e-04
5.26e-04
1.78e-01
2.16e-01
3.11e-04
l.lSe+00
1.69e-05
1.24e-03
7.34e-07
1.78e-04
9.09e-04
4.07e-02
4.01e-01
4.86e-04
3.00e-01
3.74e-01
3.81e-02
2.50e+00
3.62e-01
1.33e-04
1.54e-05
9.25e-02
1.19e-04
7.50e+00
2.64e-04
3.65e-04
2.18e-04
3.27e-04
7.00e-05
3.42e-04
1.94e-04
2.36e-01
3.72e-02
% of process
group total
0.01%
0.04%
<0.01%
<0.01%
1.34%
19.67%
3.07%
0.01%
0.01%
2.38%
2.88%
<0.01%
15.78%
0.01%
0.02%
0.01%
O.01%
0.01%
0.54%
5.35%
0.01%
4.00%
4.98%
0.51%
33.38%
4.82%
O.01%
0.01%
1.23%
0.01%
100.00%
0.08%
0.04%
0.07%
0.10%
0.02%
0.11%
0.06%
74.75%
11.80%
% of grand total
15.26%
2-118
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2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
Table 2-56. LCD manufacturing stage primary material inputs
Material
Process Group
Polyester adhesive
Polyethylene terephthalate
Polyvinyl alcohol
Total
Glass mfg
Barium Carbonate
Glass, unspecified
Potassium Carbonate
Recycled LCD glass
Sand
Sodium Carbonate
Strontium Carbonate
Zircon Sand
Total
Backlight
15" LCD light guide
Aluminum (elemental)
Argon
Backlight lamp (CCFL)
Cables/wires
Glass, unspecified
Mercury
Metals, remaining unspeciated
Neon
Poly(methyl methacrylate)
Polycarbonate resin
Polyethylene terephthalate
Rubber, unspecified
Steel
Total
PWB
PWB-laminate
Solder (63% tin; 37% lead)
Total
Japanese Grid
Coal, average (in ground)
Natural gas
Petroleum (in ground)
Uranium, yellowcake
Total
U.S. Grid
Coal, average (in ground)
Quantity (kg/
functional unit)
6.25e-04
3.14e-02
8.61e-03
3.16e-01
1.37e-02
2.28e-03
1.75e-02
9.54e-02
l.lle-01
2.26e-02
1.53e-02
2.51e-03
2.81e-01
3.74e-01
3.35e-02
3.53e-05
1.94e-03
3.43e-03
4.14e-02
3.99e-06
6.81e-04
6.31e-05
3.83e-01
1.14e-01
2.74e-02
6.01e-04
2.52e-02
1.01e-H)0
3.74e-01
2.24e-02
3.96e-01
7.69e+00
4.20e+00
4.33e+00
1.02e-03
1.62e+01
3.47e-01
% of process
group total
0.20%
9.96%
2.73%
100.00%
4.90%
0.23%
6.24%
34.00%
39.64%
8.05%
5.47%
0.90%
99.42%
37.18%
3.35%
0.01%
0.19%
0.34%
4.11%
<0.01%
0.07%
0.01%
38.12%
11.38%
2.72%
0.06%
2.50%
100.04%
94.35%
5.66%
100.00%
47.41%
25.89%
26.69%
0.01%
100.00%
90.97%
% of grand total
0.64%
0.57%
2.04%
0.81%
32.96%
2-119
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2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
Table 2-56. LCD manufacturing stage primary material inputs
Material
Process Group
Natural gas
Petroleum (in ground)
Uranium, yellowcake
Total
Fuel Production
Natural gas (in ground)
Petroleum (in ground)
Total
Grand Total
Quantity (kg/
functional unit)
2.71e-02
7.36e-03
9.39e-06
3.82e-01
5.16e+00
1.79e+01
2.31e+01
4.92e+01
% of process
group total
7.10%
1.93%
<0.01%
100.01%
22.33%
77.67%
100.00%
% of grand total
0.78%
46.94%
100.00%
2-120
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2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
Table 2-57. LCD manufacturing stage ancillary material inputs
Material
Process Group
Module/Monitor
1,4-butanolide
1 -Methoxy-2-propanol
2-(2-butoxyethoxy)-ethanol
2,2,4-trimethylpentane
2-ethoxyl ethylacetate
Acetic acid
Acetone
Al-etchant, unspecified
Aluminum sulfate
Ammonia
Ammonium bifluoride
Ammonium fluoride
Ammonium hydroxide
Argon
Calcium hydroxide
Carbon dioxide
Chlorine
Cleaner, unspecified
Cresol-formaldehyde resin
Cr-etchant, unspecified
Cyclohexane
Dimethylsulfoxide
Ethanol
Ethanol amine
Ferric chloride
Fluorocarbon resin
Flux, unspecified
Glycol ethers
Helium
Hexamethyldisilizane
Hydrochloric acid
Hydrofluoric acid
Hydrogen
Hydrogen peroxide
Isopropyl alcohol
ITO etchant, unspecified
Krypton
LNG
Methyl ethyl ketone
Monosilane
N-Butvlacetate
Quantity(kg/
functional unit)
4.04e-05
1.10e-02
3.04e-02
1.52e-05
1.78e-03
6.40e-03
1.03e-02
5.88e-03
1.056-01
1.55e-02
2.36e-03
1.14e-02
5.15e-06
7.87e-03
1.396-01
3.74e-05
1.55e-02
1.47e-04
8.29e-04
1.77e-02
2.03e-05
6.63e-02
1.35e-02
7.85e-02
8.92e-03
3.38e-06
7.35e-05
2.12e-02
6.18e-04
2.58e-04
4.31e-02
4.21e-02
4.44e-01
1.47e-04
3.49e-01
2.94e-03
2.58e-05
1.94e+02
7.35e-06
1.12e-03
3.83e-02
% of process
group total
6.91%
100.00%
0.02%
<0.01%
0.01%
0.01%
0.01%
0.01%
0.05%
0.01%
O.01%
0.01%
0.01%
0.01%
0.07%
0.01%
0.01%
O.01%
O.01%
0.01%
0.01%
0.03%
0.01%
0.04%
O.01%
O.01%
O.01%
0.01%
0.01%
0.01%
0.02%
0.02%
0.22%
O.01%
0.17%
0.01%
0.01%
95.80%
O.01%
O.01%
0.02%
% of grand total
2-121
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2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
Table 2-57. LCD manufacturing stage ancillary material inputs
Material
Process Group
Nitric acid
Nitrogen
Nitrogen fluoride
Nitrous oxide
Oxygen
Perfluoromethane
Phosphine
Phosphoric acid
Photoresist, unspecified
Polyaluminum chloride
Polyethylene mono(nonylphenyl) ether glycol
Polyimide, unspecified
Propylene glycol
Propylene glycol monomethyl ether acetate
Rinse, unspecified
Sodium dihydrogen phosphate dihydrate
Sodium hydroxide
Solder, unspecified
Sulfur hexafluoride
Sulfuric acid
Surfactant, unspecified
Synthetic resin, unspecified
Tetramethyl ammonium hydroxide
Unspecified LCD process material
Water
Xylene (mixed isomers)
Total
Panel Components
Acetone
Borax
Carbon dioxide
Cyclohexane
Developing solution, unspecified
Diluent, unspecified
Ethanol
Ethylacetate
Exfoliation liquid, unspecified
HCFC-225ca
HCFC-225cb
Heptane
Hydrochloric acid
Hydrogen
Quantity(kg/
functional unit)
1.24e-02
5.90e+00
1.08e-01
1.36e-03
7.75e-03
1.29e-03
2.69e-02
3.95e-02
1.38e-02
6.40e-03
3.40e-04
2.94e-05
4.46e-03
1.56e-02
5.27e-02
4.06e-06
3.59e-01
7.35e-05
1.62e-02
2.29e-01
1.09e-04
6.57e-04
1.29e-01
2.58e-02
6.88e-02
1.57e-03
2.03e+02
1.03e-02
9.13e-05
4.82e-03
3.89e-03
4.00e-02
8.27e-03
1.17e-02
9.68e-04
1.43e-02
1.37e-04
1.37e-04
1.03e-02
1.74e-03
3.14e-06
% of process
group total
0.01%
2.91%
0.05%
<0.01%
<0.01%
<0.01%
0.01%
0.02%
0.01%
<0.01%
<0.01%
<0.01%
<0.01%
0.01%
0.03%
<0.01%
0.18%
<0.01%
0.01%
0.11%
<0.01%
<0.01%
0.06%
0.01%
0.03%
<0.01%
206.91%
3.19%
0.01%
1.50%
1.21%
12.45%
2.57%
3.65%
0.30%
4.44%
0.04%
0.04%
3.19%
0.54%
0.01%
% of grand total
99.48%
2-122
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2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
Table 2-57. LCD manufacturing stage ancillary material inputs
Material
Process Group
Methyl ethyl ketone
Nitric acid second cerium ammonium
Nitrogen
Orthoboric acid
Perchloric acid
Photoresist, unspecified
Polyethylene terephthalate
Sulfuric acid
Tetrahydrofuran
Toluene
Total
LCD Glass
Aluminum Oxide
Cerium Oxide
Chromium Oxide
Hydrofluoric acid
Pumice
Total
Backlight
Diethyl ether
Ethanol
Process material for backlight assembly
Unspecified ancillary material
Total
PWB
Ammonium chloride
Ammonium hydroxide
Formaldehyde
Glycol ethers
Hydrochloric acid
Hydrogen peroxide
Nitric acid
Polyethylene glycol
Potassium hydroxide
Potassium permanganate
Potassium peroxymonosulfate
PWB -solder mask solids
Sodium Carbonate
Sodium hydroxide
Sulfuric acid
Total
Japanese Grid
Quantity(kg/
functional unit)
4.84e-04
1.13e-02
1.17e-01
7.30e-04
3.82e-03
2.94e-03
3.20e-02
1.58e-02
3.82e-03
2.75e-02
3.22e-01
1.56e-03
1.52e-04
2.60e-06
3.66e-03
3.64e-03
9.02e-03
9.28e-05
4.63e-05
7.03e-05
4.19e-04
6.28e-04
3.42e-02
3.42e-02
2.91e-03
1.04e-02
8.46e-02
1.37e-02
5.99e-02
2.23e-02
1.88e-02
5.14e-04
3.12e-02
1.93e-02
1.42e-02
8.56e-02
8.05e-02
5.12e-01
% of process
group total
0.15%
3.51%
36.27%
0.23%
1.19%
0.91%
9.93%
4.91%
1.19%
8.56%
99.99%
17.30%
1.68%
0.03%
40.61%
40.37%
100.00%
14.78%
7.36%
11.19%
66.67%
100.00%
6.68%
3.42%
0.57%
2.03%
16.51%
2.67%
11.70%
4.34%
3.68%
0.10%
6.08%
3.76%
2.77%
16.71%
15.72%
96.74%
% of grand total
0.16%
0.00%
0.00%
0.25%
2-123
-------
2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
Table 2-57. LCD manufacturing stage ancillary material inputs
Material
Process Group
Lime
Limestone
Total
U.S. Grid
Lime
Limestone
Total
Fuel Production
Bauxite (A12O3, ore)
Limestone (CaCO3, in ground)
Sand (in ground)
Sodium chloride (NaCl, in ground or in sea)
Total
Grand Total
Quantity(kg/
functional unit)
4.53e-02
1.03e-01
1.48e-01
2.05e-03
4.66e-03
6.71e-03
2.16e-03
5.49e-02
1.32e-03
6.08e-04
5.90e-02
2.04e+02
% of process
group total
30.57%
69.43%
100.00%
30.52%
69.48%
100.00%
3.66%
93.07%
2.24%
1.03%
100.00%
% of grand total
0.07%
0.00%
0.03%
100.00%
2-124
-------
2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
Table 2-58. LCD manufacturing stage utility inputs
Material
Process group
Fuels (kg/functional unit):
Monitor/Module
Fuel oil #4
Kerosene
LNG
Liquified petroleum gas (LPG)
Natural gas
Total
Panel Components
Kerosene
Natural gas
Steam ( 100 psig)
Fuel oil #2
Fuel oil #6
Natural gas
Total
LCD glass
Fuel oil #2
Liquified petroleum gas (LPG)
Natural gas
Total
Backlight
LNG
Natural gas
Total
PWB
Natural gas
Fuels
Coal, average (in ground)
Natural gas (in ground)
Petroleum (in ground)
Uranium (U, ore)
Total
Grand Total
Electricity (MJ/functional unit):
Monitor/Module
Panel Components
LCD glass
Backlight
PWB
Total
Quantity
2.11e-01
2.98e-01
3.22e+00
5.83e-01
8.48e-01
5.16e-H)0
1.68e-01
1.18e-07
1.45e-01
4.07e-04
1.25e-01
8.64e-02
5.25e-01
5.38e-02
1.626+01
5.63e-02
1.64e+01
4.17e-06
4.17e-06
8.33e-06
??
6.86e-01
2.41e+00
4.84e-01
1.15e-05
3.58e+00
2.56e+01
2.59e+02
4.64e+01
2.20e+00
4.46e+00
4.43e+00
3.16e+02
% of process
group total
4.09%
5.77%
62.40%
11.30%
16.44%
95.91%
31.97%
0.01%
27.56%
0.08%
23.91%
16.47%
68.03%
0.33%
99.33%
0.34%
100.00%
50.00%
50.00%
200.00%
19.19%
67.27%
13.54%
0.01%
100.00%
% of grand total
20.13%
2.05%
63.87%
0.00%
ERR
13.96%
100.00%
81.80%
14.70%
0.70%
1.41%
1.40%
100.00%
2-125
-------
2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
Table 2-58. LCD manufacturing stage utility inputs
Material
Process group
Water (kg or L/functional unit):
Monitor/Module
Panel Components
LCD glass
Backlight
PWB
Japanese electric grid
U.S. electric grid
Fuels
Total
Quantity
1.08e+03
2.08e+02
1.62e+00
1.92e+02
1.86e+01
1.49e+02
2.20e+00
5.07e+02
2.15e+03
% of process
group total
% of grand total
49.96%
9.66%
0.08%
8.91%
0.86%
6.91%
0.10%
23.53%
100.00%
Total energy (fuels and electricity, MJ/functional unit):
Monitor/Module
Panel Components
LCD glass
Backlight
PWB
Fuels
Total
5.08e+02
6.29e+01
7.05e+02
4.46e+00
1.216+01
1.45e+02
1.44e+03
35.36%
4.38%
49.03%
0.31%
0.84%
10.09%
100.00%
2-126
-------
2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
Table 2-59. LCD manufacturing stage air outputs
Material
Process Group
Module/Monitor
Acetic acid
Acetone
Al-etchant, unspecified
Ammonia
Argon
Carbon dioxide
Cr-etchant, unspecified
Cyclohexane
Diethylene glycol
Hexamethyldisilizane
Hydrochloric acid
Hydrofluoric acid
Hydrogen
Isopropyl alcohol
ITO etchant, unspecified
Monosilane
N-bromoacetamide
Nitric acid
Nitrogen fluoride
Nitrogen oxides
Phosphine
Phosphoric acid
PM
Polyimide, unspecified
Sulfur hexafluoride
Sulfur oxides
Tetramethyl ammonium hydroxide
Unspecified LCD process material
Total
Panel Components
Carbon dioxide
Ethylacetate
HCFC-225ca
HCFC-225cb
Heptane
Hydrochloric acid
Methyl ethyl ketone
Nitrogen oxides
Nonmethane hydrocarbons, remaining unspeciated
PM
Toluene
Quantity (kg/
functional unit)
1.36e-03
1.86e-04
1.37e-02
6.23e-02
5.80e-03
2.16e-03
4.12e-02
4.85e-05
9.69e-05
1.37e-06
6.06e-02
5.21e-02
1.33e-04
1.78e-02
6.86e-03
1.54e-03
9.18e-03
2.69e-04
2.45e-01
5.48e-01
6.26e-02
4.85e-05
l.lOe-05
1.40e-04
7.30e-03
1.12e-03
6.43e-01
4.49e-02
1.83e+00
4.82e-03
2.44e-06
1.40e-04
1.40e-04
7.77e-05
7.32e-06
1.35e-04
4.11e-04
7.77e-05
2.74e-05
5.44e-05
% of process
group total
0.07%
0.02%
0.75%
3.41%
0.32%
0.12%
2.25%
0.01%
0.01%
<0.01%
3.31%
2.85%
0.01%
0.97%
0.38%
0.08%
0.50%
0.01%
13.43%
30.00%
3.43%
0.01%
0.01%
0.01%
0.40%
0.06%
35.16%
2.46%
100.00%
81.79%
O.01%
2.37%
2.37%
1.32%
0.12%
2.29%
6.98%
1.32%
0.47%
0.92%
% of grand
total
2.82%
2-127
-------
2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
Table 2-59. LCD manufacturing stage air outputs
Material
Process Group
Total
LCD Glass
Carbon dioxide
Carbon monoxide
Chromium
Nitrogen oxides
PM
Sulfur oxides
Total
Backlight
Diethyl ether
Ethanol
Nitrogen oxides
Process material for backlight assembly
Total
PWB
Formaldehyde
Japanese Grid
1,1,1 -Trichloroethane
1 ,2-Dichloroethane
2,3,7,8-TCDD
2,3,7,8-TCDF
2,4-Dinitrotoluene
2-Chloroacetophenone
2-Methylnaphthalene
5-Methyl chrysene
Acenaphthene
Acenaphthylene
Acetaldehyde
Acetophenone
Acrolein
Anthracene
Antimony
Arsenic
Barium
Benzene
Benzo [a] anthracene
Benzo |a]pyrene
Benzo [b,j,k]fluoranthene
Benzo |g,h,ilperylene
Benzyl chloride
Beryllium
Quantity (kg/
functional unit)
5.89e-03
1.30e-01
2.07e-07
6.40e-09
2.04e-03
5.06e-06
2.36e-06
1.32e-01
9.26e-05
4.63e-05
2.95e-02
7.03e-05
2.97e-02
1.71e-05
2.17e-07
1.54e-07
5.65e-14
1.96e-13
1.07e-09
2.69e-08
S.OOe-10
8.466-11
1.45e-08
l.lle-09
2.19e-06
5.77e-08
l.lle-06
1.53e-09
3.20e-06
2.36e-06
1.74e-06
5.13e-06
2.69e-09
1.46e-10
1.31e-09
1.45e-09
2.69e-06
1.09e-07
% of process
group total
100.00%
98.45%
0.01%
0.01%
1.55%
O.01%
O.01%
100.03%
0.31%
0.16%
99.29%
0.24%
100.00%
0.01%
0.01%
O.01%
O.01%
O.01%
O.01%
0.01%
0.01%
0.01%
0.01%
O.01%
O.01%
O.01%
O.01%
0.01%
0.01%
0.01%
O.01%
O.01%
O.01%
O.01%
0.01%
0.01%
0.01%
% of grand
total
0.01%
0.20%
0.05%
0.00%
2-128
-------
2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
Table 2-59. LCD manufacturing stage air outputs
Material
Process Group
Biphenyl
Bromoform
Bromomethane
Cadmium
Carbon dioxide
Carbon disulfide
Carbon monoxide
Chloride ions
Chlorobenzene
Chloroform
Chromium (III)
Chromium (VI)
Chrysene
Cobalt
Copper
Cumene hydroperoxide
Cyanide (-1)
Di(2-ethylhexyl)phthalate
Dibenzo [a,h] anthracene
Dichloromethane
Dimethyl sulfate
Dioxins, remaining unspeciated
Ethyl Chloride
Ethylbenzene
Ethylene dibromide
Fluoranthene
Fluorene
Fluorides (F-)
Formaldehyde
Furans, remaining unspeciated
Hexane
Hydrochloric acid
Hydrofluoric acid
Indeno( 1 ,2,3 -cd)pyrene
Isophorone
Lead (Pb, ore)
Magnesium
Manganese (Mn, ore)
Mercury
Methane
Methyl chloride
Quantity (kg/
functional unit)
6.53e-09
1.50e-07
6.15e-07
4.74e-07
5.18e+01
5.00e-07
9.43e-03
2.07e-04
8.46e-08
2.27e-07
1.86e-06
4.51e-07
1. 80e-09
3.98e-06
1.07e-06
2.04e-08
9.61e-06
2.81e-07
9.95e-10
l.lle-06
1.85e-07
2.51e-12
1.61e-07
3.99e-07
4.61e-09
5.88e-09
6.15e-09
2.22e-05
3.43e-05
4.00e-12
2.58e-07
4.61e-03
5.77e-04
1.51e-09
2.23e-06
1.48e-06
4.23e-05
3.67e-06
3.97e-07
2.73e-04
2.04e-06
% of process
group total
0.01%
<0.01%
<0.01%
<0.01%
99.14%
<0.01%
0.02%
0.01%
0.01%
O.01%
O.01%
O.01%
O.01%
0.01%
0.01%
0.01%
O.01%
O.01%
O.01%
O.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
% of grand
total
2-129
-------
2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
Table 2-59. LCD manufacturing stage air outputs
Material
Process Group
Methyl ethyl ketone
Methyl hydrazine
Methyl methacrylate
Methyl tert-butyl ether
Molybdenum
Naphthalene
Nickel
Nitrogen oxides
Nitrous oxide
o-xylene
Phenanthrene
Phenol
PM-10
Propionaldehyde
Pyrene
Selenium
Styrene
Sulfur dioxide
Tetrachloroethylene
TOCs, remaining unspeciated
Toluene
Vanadium
Vinyl acetate
Xylene (mixed isomers)
Zinc (elemental)
Total
U.S. Grid
1,1,1 -Trichloroethane
1 ,2-Dichloroethane
2,3,7,8-TCDD
2,3,7,8-TCDF
2,4-Dinitrotoluene
2-Chloroacetophenone
2-Methylnaphthalene
5-Methyl chrysene
Acenaphthene
Acenaphthylene
Acetaldehyde
Acetophenone
Quantity (kg/
functional unit)
1.50e-06
6.54e-07
7.69e-08
1.34e-07
5.20e-07
7.44e-07
4.95e-05
1.37e-01
3.76e-04
6.49e-08
1.75e-08
6.15e-08
6.72e-03
1.46e-06
4.24e-09
5.40e-06
9.61e-08
2.90e-01
1.65e-07
6.63e-04
4.81e-06
1.92e-05
2.92e-08
1.42e-07
1.73e-05
5.22e+01
3.71e-09
6.95e-09
2.48e-15
8.86e-15
4.86e-ll
1.22e-09
5.16e-12
3.82e-12
1.10e-10
4.37e-ll
9.90e-08
2.60e-09
% of process
group total
0.01%
<0.01%
<0.01%
<0.01%
<0.01%
<0.01%
<0.01%
0.26%
<0.01%
<0.01%
<0.01%
<0.01%
0.01%
<0.01%
0.01%
0.01%
0.01%
0.56%
O.01%
O.01%
O.01%
0.01%
0.01%
0.01%
0.01%
100.84%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
% of grand
total
80.58%
2-130
-------
2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
Table 2-59. LCD manufacturing stage air outputs
Material
Process Group
Acrolein
Anthracene
Antimony
Arsenic
Barium
Benzene
Benzo[a]anthracene
Benzo[a]pyrene
Benzo [b j ,k]fluoranthene
Benzo [g,h,i]perylene
Benzyl chloride
Beryllium
Biphenyl
Bromoform
Bromomethane
Cadmium
Carbon dioxide
Carbon disulfide
Carbon monoxide
Chloride ions
Chlorobenzene
Chloroform
Chromium (III)
Chromium (VI)
Chrysene
Cobalt
Copper
Cumene
Cyanide (-1)
Di(2-ethylhexyl)phthalate
Dibenzo [a,h] anthracene
Dichloromethane
Dimethyl sulfate
Dioxins, remaining unspeciated
Ethyl Chloride
Ethylbenzene
Ethylene dibromide
Fluoranthene
Fluorene
Quantity (kg/
functional unit)
5.04e-08
3.77e-ll
8.45e-09
7.26e-08
3.98e-09
2.26e-07
1.80e-ll
6.60e-12
2.06e-ll
6.98e-12
1.22e-07
3.69e-09
2.95e-10
6.77e-09
2.78e-08
9.33e-09
8.61e-01
2.26e-08
1.57e-04
3.52e-07
3.82e-09
1.02e-08
4.71e-08
1.40e-08
1.986-11
2.35e-08
1.93e-09
9.20e-10
4.34e-07
1.27e-08
1.69e-12
5.04e-08
8.33e-09
1.13e-13
7.29e-09
1.64e-08
2.08e-10
1.30e-10
1.63e-10
% of process
group total
0.01%
<0.01%
<0.01%
<0.01%
<0.01%
<0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
98.98%
O.01%
0.02%
O.01%
O.01%
0.01%
0.01%
0.01%
0.01%
O.01%
O.01%
O.01%
O.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
% of grand
total
2-131
-------
2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
Table 2-59. LCD manufacturing stage air outputs
Material
Process Group
Fluoride
Formaldehyde
Furans, remaining unspeciated
Hexane
Hydrochloric acid
Hydrofluoric acid
Indeno( 1 ,2,3 -cd)pyrene
Isophorone
Lead
Magnesium
Manganese
Mercury
Methane
Methyl chloride
Methyl ethyl ketone
Methyl hydrazine
Methyl methacrylate
Methyl tert-butyl ether
Molybdenum
Naphthalene
Nickel
Nitrogen oxides
Nitrous oxide
o-xylene
Phenanthrene
Phenol
Phosphorus (yellow or white)
PM-10
Propionaldehyde
Pyrene
Selenium
Styrene
Sulfur dioxide
Tetrachloroethylene
TOCs, remaining unspeciated
Toluene
Vanadium
Vinyl acetate
Xylene (mixed isomers)
Quantity (kg/
functional unit)
3.78e-08
1.64e-07
1.80e-13
1.16e-08
2.08e-04
2.60e-05
1.28e-ll
l.Ole-07
2.47e-08
1.91e-06
8.83e-08
1.45e-08
1.25e-03
9.20e-08
6.77e-08
2.95e-08
3.47e-09
6.08e-09
1.13e-09
3.54e-09
1.33e-07
2.28e-03
6.58e-06
1.10e-10
4.85e-10
2.78e-09
9.59e-09
1.12e-04
6.60e-08
6.456-11
2.26e-07
4.34e-09
4.83e-03
7.47e-09
1.12e-05
4.92e-08
3.41e-08
1.32e-09
6.42e-09
% of process
group total
0.01%
<0.01%
<0.01%
<0.01%
0.02%
<0.01%
<0.01%
<0.01%
0.01%
0.01%
0.01%
0.01%
0.14%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.26%
0.01%
0.01%
0.01%
O.01%
O.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.56%
O.01%
O.01%
O.01%
O.01%
0.01%
0.01%
% of grand
total
2-132
-------
2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
Table 2-59. LCD manufacturing stage air outputs
Material
Process Group
Zinc (elemental)
Total
Fuel Production
1,1,1 -Trichloroethane
1 ,2-Dichloroethane
1 ,4-Dichlorobenzene
2,4-Dinitrotoluene
2-Chloroacetophenone
3 -Methy Icholanthrene
5-Methyl chrysene
Acenaphthene
Acenaphthylene
Acetaldehyde
Acetophenone
Acrolein
Aldehydes
Aluminum (elemental)
Ammonia
Anthracene
Antimony
Aromatic hydrocarbons
Arsenic
Barium
Benzene
Benzo [a] anthracene
Benzo[a]pyrene
Benzo [b,j ,k]fluoranthene
Benzo [b]fluoranthene
Benzo [g,h,i]perylene
Benzo [kjfluoranthene
Benzyl chloride
Beryllium
Biphenyl
Bromoform
Bromomethane
Butane
Cadmium
Calcium
Carbon dioxide
Quantity (kg/
functional unit)
2.95e-08
8.70e-01
6.91e-09
1.38e-08
1.89e-08
9.68e-ll
2.42e-09
2.84e-ll
7.60e-12
2.77e-10
1.16e-10
1.97e-07
5.18e-09
l.OOe-07
8.98e-05
9.59e-07
3.53e-04
1.15e-10
1.15e-10
2.55e-09
7.13e-07
1.77e-08
2.70e-03
6.97e-ll
3.846-11
3.80e-ll
3.096-11
3.21e-ll
3.096-11
2.42e-07
7.31e-08
5.88e-10
1.35e-08
5.53e-08
3.31e-05
4.18e-08
8.31e-07
9.44e+00
% of process
group total
0.01%
100.83%
0.01%
0.01%
0.01%
0.01%
O.01%
O.01%
O.01%
O.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.03%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
97.19%
% of grand
total
1.34%
2-133
-------
2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
Table 2-59. LCD manufacturing stage air outputs
Material
Process Group
Carbon disulfide
Carbon monoxide
Chloride ions
Chlorine
Chlorobenzene
Chloroform
Chromium (III)
Chromium (VI)
Chrysene
Cobalt
Copper
Cumene
Cyanide (-1)
Di(2-ethylhexyl)phthalate
Dibenzo [a,h] anthracene
Dichloromethane
Dimethyl sulfate
Dimethylbenzanthracene
Dioxins, remaining unspeciated
Ethane
Ethyl Chloride
Ethylbenzene
Ethylene dibromide
Fluoranthene
Fluorene
Fluorides (F-)
Formaldehyde
Furans, remaining unspeciated
Halogenated hydrocarbons (unspecified)
HALON-1301
Hexane
Hydrocarbons, remaining unspeciated
Hydrochloric acid
Hydrofluoric acid
Hydrogen sulfide
Indeno( 1 ,2,3 -cd)pyrene
Iron
Isophorone
Lead
Quantity (kg/
functional unit)
4.49e-08
2.89e-02
1.75e-06
l.Ole-09
7.60e-09
2.04e-08
1.05e-06
1.05e-06
6.70e-ll
1.27e-07
7.98e-08
1.83e-09
8.64e-07
2.52e-08
2.18e-ll
l.OOe-07
1.66e-08
2.36e-10
5.60e-12
4.88e-05
1.45e-08
3.28e-08
4.15e-10
3.01e-10
3.66e-10
1.98e-07
5.78e-05
2.60e-ll
1.42e-14
2.47e-ll
2.84e-05
7.75e-03
4.15e-04
5.18e-05
1.51e-04
5.31e-ll
1.85e-06
2.00e-07
6.39e-07
% of process
group total
0.01%
0.30%
<0.01%
<0.01%
<0.01%
<0.01%
<0.01%
<0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.08%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
% of grand
total
2-134
-------
2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
Table 2-59. LCD manufacturing stage air outputs
Material
Process Group
Magnesium
Manganese
Mercury
Metals, remaining unspeciated
Methane
Methyl chloride
Methyl ethyl ketone
Methyl hydrazine
Methyl methacrylate
Methyl tert-butyl ether
Molybdenum
Naphthalene
Nickel
Nitrogen oxides
Nitrous oxide
Nonmethane hydrocarbons, remaining unspeciated
n-Propane
Other organics
o-xylene
Pentane
Phenanthrene
Phenol
Phosphorus (yellow or white)
PM
PM-10
Polycyclic aromatic hydrocarbons
Propionaldehyde
Pyrene
Selenium
Silicon
Sodium
Styrene
Sulfur oxides
Tetrachloroethylene
Toluene
Vanadium
Vinyl acetate
Zinc (elemental)
Total
Quantity (kg/
functional unit)
3.80e-06
1.15e-06
4.55e-08
1.60e-08
1.20e-01
1.83e-07
1.35e-07
5.88e-08
6.91e-09
1.21e-08
9.92e-08
1.98e-08
6.06e-06
4.27e-02
8.13e-04
8.79e-03
8.67e-08
1.35e-02
1.59e-07
4.10e-05
1.22e-09
5.53e-09
6.10e-07
6.95e-03
l.lle-05
2.84e-12
1.31e-07
2.00e-10
4.81e-07
8.31e-07
4.92e-06
8.64e-09
3.96e-02
1.49e-08
2.63e-07
1.30e-05
2.63e-09
6.04e-07
9.72e+00
% of process
group total
0.01%
<0.01%
<0.01%
<0.01%
1.24%
0.01%
0.01%
0.01%
0.01%
O.01%
O.01%
O.01%
O.01%
0.44%
0.01%
0.09%
0.01%
0.14%
O.01%
O.01%
O.01%
0.01%
0.01%
0.07%
0.01%
O.01%
O.01%
O.01%
O.01%
0.01%
0.01%
0.01%
0.41%
O.01%
O.01%
O.01%
O.01%
0.01%
101.01%
% of grand
total
15.00%
2-135
-------
2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
Table 2-59. LCD manufacturing stage air outputs
Material
Process Group
Grand Total
Quantity (kg/
functional unit)
6.48e-K)l
% of process
group total
% of grand
total
100.00%
2-136
-------
2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
Table 2-60. LCD manufacturing stage water outputs
Material
Process Group
WASTEWATER STREAMS
Module/monitor
Panel components
LCD glass
Backlight
PWB
Fuels
Total
WATER POLLUTANTS
Module/monitor
1,1,1 -Trichloroethane
Antimony
Arsenic
BOD
BOD
Boron
Cadmium
Chromium
Chromium (VI)
COD
COD
Colon bacillus (bacteria in large intestine)
Copper
Cyanide (-1)
Cyanide (-1)
Dissolved solids
Fluorides (F-)
Fluorides (F-)
Hexane
Iron
Lead
Manganese
Mercury
Nickel
Nitrogen
Nitrogen
Oil & grease
Oil & grease
Organic phosphorus, unspecified
Phenol
Phosphorus (yellow or white)
Phosphorus (yellow or white)
Disposition
both
both
surface water
both
treatment
surface water
surface water
surface water
surface water
surface water
treatment
surface water
surface water
surface water
surface water
surface water
treatment
surface water
surface water
surface water
treatment
surface water
surface water
treatment
surface water
surface water
surface water
surface water
surface water
surface water
surface water
treatment
surface water
treatment
surface water
surface water
surface water
treatment
Quantity (kg/
functional unit)
2.87e+03
3.53e-01
1.67e+00
1.92e+02
1.86e+01
4.33e+01
3.12e+03
2.29e-08
1.14e-07
1.14e-07
1.74e-02
5.05e-02
4.58e-06
1.14e-07
8.84e-06
2.29e-07
2.68e-03
3.90e-02
3.89e-03
9.18e-07
3.66e-06
6.67e-07
7.55e-03
1.28e-02
2.40e-04
5.88e-04
2.63e-06
6.17e-06
2.29e-07
9.69e-08
2.29e-07
7.93e-02
1.16e-02
2.02e-04
3.53e-03
2.29e-07
2.29e-07
4.31e-03
6.91e-03
% of process
group total
<0.01%
0.01%
0.01%
6.69%
19.41%
O.01%
O.01%
O.01%
O.01%
1.03%
14.99%
1.50%
O.01%
O.01%
O.01%
2.90%
4.91%
0.09%
0.23%
0.01%
O.01%
O.01%
O.01%
O.01%
30.45%
4.45%
0.08%
1.35%
0.01%
O.01%
1.65%
2.65%
% of grand total
91.80%
0.01%
0.05%
6.15%
0.60%
1.39%
100.00%
2-137
-------
2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
Table 2-60. LCD manufacturing stage water outputs
Material
Process Group
Polychlorinated biphenyls
Suspended solids
Suspended solids
Tetrachloroethylene
Tin
Trichloroethylene
Zinc (elemental)
Total
Panel components
BOD
BOD
Borax
COD
Hydrochloric acid
Nitrogen
Orthoboric acid
Phosphorus (yellow or white)
Suspended solids
Total
LCD glass
BOD
Chloride ions
Chromium
COD
Dissolved solids
Fluorides (F-)
Iron
Lead
Nickel
Nitrate
Oil & grease
Suspended solids
Total
Backlight
BOD
Iron
Lead
Mercury
Nickel
Nitrogen
Oil & grease
Suspended solids
Disposition
surface water
surface water
treatment
surface water
surface water
surface water
surface water
surface water
treatment
treatment
surface water
treatment
surface water
treatment
surface water
surface water
surface water
surface water
surface water
surface water
surface water
surface water
surface water
surface water
surface water
surface water
surface water
surface water
treatment
treatment
treatment
treatment
treatment
treatment
treatment
treatment
Quantity (kg/
functional unit)
1.14e-08
1.55e-02
4.26e-03
2.29e-08
4.58e-07
2.29e-08
2.63e-06
2.60e-01
1.34e-03
3.89e-03
1.31e-06
2.21e-03
3.29e-06
5.71e-04
1.31e-06
2.48e-05
6.46e-04
8.69e-03
3.80e-07
4.68e-02
3.80e-09
3.80e-07
1.68e-01
1.36e-04
1.28e-04
2.01e-06
3.80e-09
1.83e-07
3.34e-04
3.35e-04
2.15e-01
3.00e-03
8.33e-05
8.33e-07
8.33e-08
3.33e-06
l.OOe-03
8.33e-05
1.33e-03
% of process
group total
0.01%
5.96%
1.64%
<0.01%
<0.01%
<0.01%
<0.01%
100.21%
15.44%
44.73%
0.02%
25.45%
0.04%
6.58%
0.02%
0.29%
7.43%
100.00%
0.01%
21.73%
0.01%
0.01%
77.84%
0.06%
0.06%
O.01%
0.01%
0.01%
0.16%
0.16%
100.00%
54.50%
1.51%
0.02%
O.01%
0.06%
18.17%
1.51%
24.22%
% of grand total
21.11%
0.70%
17.46%
2-138
-------
2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
Table 2-60. LCD manufacturing stage water outputs
Material
Process Group
Total
PWB
Copper (+1 & +2)
Lead cmpds
Total
Japanese grid
Sulfate ion (-4)
Suspended solids
Total
U.S. grid
Sulfate ion (-4)
Suspended solids
Total
Fuels
Acids (H+)
Adsorbable organic halides
Aluminum (+3)
Ammonia ions
Aromatic hydrocarbons
Barium cmpds
BOD
Cadmium cmpds
Chloride ions
Chromium (III)
Chromium (VI)
COD
Copper (+1 & +2)
Cyanide (-1)
Dissolved organics
Dissolved solids
Fluorides (F-)
Halogenated matter (organic)
Hydrocarbons, remaining unspeciated
Iron (+2 & +3)
Lead cmpds
Mercury compounds
Metals, remaining unspeciated
Nickel cmpds
Nitrate
Other nitrogen
Phenol
Phosphates
Disposition
treatment
treatment
surface water
surface water
treatment
treatment
surface water
surface water
surface water
surface water
surface water
surface water
surface water
surface water
surface water
surface water
surface water
surface water
surface water
surface water
surface water
surface water
surface water
surface water
surface water
surface water
surface water
surface water
surface water
surface water
surface water
surface water
surface water
surface water
Quantity (kg/
functional unit)
5.50e-03
4.28e-05
7.14e-06
5.00e-05
2.93e-03
7.63e-05
3.01e-03
1.32e-04
3.45e-06
1.36e-04
1.76e-08
1.82e-ll
6.88e-06
1.33e-03
4.25e-09
1.36e-08
9.12e-03
1.42e-ll
2.65e-01
3.49e-09
3.49e-09
7.71e-02
2.84e-10
1.99e-ll
4.67e-08
2.01e-05
1.76e-06
5.67e-12
1.70e-05
1.73e-08
5.676-11
6.52e-14
4.72e-04
2.84e-ll
2.97e-06
7.66e-10
1.75e-04
2.83e-08
% of process
group total
100.00%
85.71%
14.29%
100.00%
97.46%
2.54%
100.00%
97.46%
2.54%
100.00%
0.01%
0.01%
0.01%
0.18%
O.01%
O.01%
1.23%
0.01%
35.77%
0.01%
O.01%
10.42%
O.01%
O.01%
0.01%
0.01%
0.01%
0.01%
O.01%
O.01%
O.01%
O.01%
0.06%
0.01%
0.01%
0.01%
0.02%
O.01%
% of grand total
0.45%
0.00%
0.24%
0.01%
2-139
-------
2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
Table 2-60. LCD manufacturing stage water outputs
Material
Process Group
Polycyclic aromatic hydrocarbons
Salts (unspecified)
Sodium (+1)
Sulfate ion (-4)
Sulfide
Suspended solids
TOCs
Toluene
Waste oil
Zinc (+2)
Total
Grand Total
Disposition
surface water
surface water
surface water
surface water
surface water
surface water
surface water
surface water
surface water
surface water
Quantity (kg/
functional unit)
6.81e-ll
7.84e-05
3.41e-01
4.36e-06
9.86e-09
4.14e-02
4.25e-08
6.24e-10
4.87e-03
1.40e-09
7.40e-01
1.23e-H)0
% of process
group total
0.01%
0.01%
46.05%
<0.01%
<0.01%
5.59%
0.01%
0.01%
0.66%
O.01%
100.27%
% of grand total
60.02%
100.00%
2-140
-------
2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
Table 2-61. LCD manufacturing stage hazardous waste outputs
Material
Process Group
Monitor/module
Mercury
Waste metals, unspecified
Waste acids, unspecified
Waste acid (mainly HF)
Waste acid (mainly HF)
Unspecified sludge
Thinner, unspecified
Tetramethyl ammonium hydroxide
Sodium sulfate
Rinse, unspecified
Remover, unspecified
Remover, unspecified
Phosphoric acid
Nitric acid
Isopropyl alcohol
Isopropyl alcohol
Ferric chloride
Acetone
Acetic acid
Total
Panel components
Spent solvents (F003 waste)
Flammable liquids (F003 waste)
Acid waste (D002 waste)
Spent solvent (with halogenated
materials)
Spent solvent (non-halogenated)
HCFC-225cb
HCFC-225ca
Waste solvent (photoresist)
Waste solvent (photoresist)
Waste acid (chrome mixed acid)
Total
LCD glass
Waste Batch (Ba, Pb) (D008 waste)
Waste acid (mostly 3% HC1 solution)
Hydrofluoric acid
Chrome liquid waste (D007 waste)
Chrome debris (D007 waste)
Barium debris (D008 waste)
Total
Disposition
recycling/reuse
recycling/reuse
recycling/reuse
recycling/reuse
treatment
land (other than landfill)
treatment
recycling/reuse
recycling/reuse
recycling/reuse
recycling/reuse
treatment
landfill
landfill
recycling/reuse
treatment
recycling/reuse
treatment
landfill
treatment
treatment
treatment
treatment
treatment
recycling/reuse
recycling/reuse
recycling/reuse
treatment
recycling/reuse
landfill
recycling/reuse
landfill
recycling/reuse
treatment
landfill
Quantity (kg/
functional unit)
2.00e-06
1.17e-03
3.24e-02
5.69e-01
1.36e-01
3.09e-02
5.40e-01
1.426-01
2.44e-01
4.67e-02
8.84e-02
3.03e-01
1.44e-02
3.43e-04
1.69e-01
1.91e+00
1.37e-02
2.77e-02
4.46e-03
4.28e+00
2.74e-04
9.13e-04
1.19e-03
1.55e-02
4.66e-02
3.11e-05
3.11e-05
2.05e-02
2.17e-02
7.18e-03
1.14e-01
6.55e-05
1.82e-04
8.24e-05
4.54e-04
6.83e-06
9.91e-06
8.01e-04
% of process
group total
<0.01%
0.03%
0.76%
13.30%
3.17%
0.72%
12.62%
3.33%
5.72%
1.09%
2.07%
7.08%
0.34%
0.01%
3.95%
44.75%
0.32%
0.65%
0.10%
100.00%
0.24%
0.80%
1.04%
13.63%
40.89%
0.03%
0.03%
18.00%
19.05%
6.29%
100.00%
8.18%
22.74%
10.29%
56.70%
0.85%
1.24%
100.00%
% of grand
total
92.11%
2.46%
0.02%
2-141
-------
2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
Table 2-61. LCD manufacturing stage hazardous waste outputs
Material
Process Group
Backlight
Hazardous waste, unspecified
Hazardous waste, unspecified
Waste glass, with mercury
Waste CCFL, with mercury
Waste CCFL, with lead
Silver
Chromium
Total
PWB
PWB- Waste cupric etchant
PWB-Solder dross
PWB-Route dust
PWB-Lead contaminated waste oil
PWB-Decontaminating debris
Hazardous waste, unspecified
Total
Fuels
Hazardous waste, unspecified
Grand Total
Disposition
recycling/reuse
treatment
landfill
treatment
treatment
landfill
landfill
recycling/reuse
recycling/reuse
recycling/reuse
treatment
treatment
treatment
landfill
Quantity (kg/
functional unit)
1.42e-02
6.80e-03
1.05e-10
8.17e-10
8.17e-08
2.72e-09
1.52e-06
2.11e-02
9.93e-02
2.96e-02
5.31e-03
5.14e-03
6.85e-03
5.48e-02
2.01e-01
2.97e-02
4.64e+00
% of process
group total
67.68%
32.31%
<0.01%
<0.01%
0.01%
0.01%
0.01%
100.00%
49.42%
14.72%
2.64%
2.56%
3.41%
27.26%
100.00%
% of grand
total
0.45%
4.33%
0.64%
100.00%
2-142
-------
2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
Table 2-62. LCD manufacturing stage solid waste outputs
Material
Process Group
Monitor/module
Isopropyl alcohol
LCD panel waste
Printed wiring board (PWB)
Remover, unspecified
Unspecified sludge
Unspecified sludge
Unspecified solid waste
Waste acid (containing F and detergents)
Waste acids, unspecified
Waste alkali, unspecified
Waste LCD glass
Waste LCD glass
Waste metals, unspecified
Waste oil
Waste plastic from LCD modules
Waste plastic from LCD modules
Waste plastics from LCD monitor
Total
Panel components
Isopropyl alcohol
Polyester resin
Unspecified solid waste
Used silica gel
Waste alkali (color filter developer,
unspecified)
Waste LCD glass
Total
LCD glass
abrasive sludge
acid absorbent
blasting media
Cinders from LCD glass mfg
Cobalt nitrate
Diesel fuel
Dust
LCD glass EP dust
LCD glass EP dust
LCD glass, unspecified
Nickel nitrate
Oily rags & filter media
Oily rags & filter media
Disposition
treatment
landfill
landfill
treatment
recycling/reuse
treatment
recycling/reuse
landfill
treatment
recycling/reuse
landfill
recycling/reuse
recycling/reuse
treatment
recycling/reuse
treatment
landfill
recycling/reuse
recycling/reuse
treatment
landfill
recycling/reuse
landfill
recycling/reuse
landfill
landfill
landfill
treatment
treatment
treatment
landfill
recycling/reuse
landfill
treatment
landfill
recycling/reuse
Quantity (kg/
functional unit)
1.03e-02
2.43e-02
7.50e-03
3.09e-02
8.46e-01
5.73e-02
2.02e-02
2.70e-01
l.OSe-Ol
3.23e-01
2.06e-01
7.20e-01
2.93e-03
1.61e-02
7.40e-02
4.03e-01
4.05e-02
3.16e+00
2.53e-02
3.20e-02
1.10e-02
6.22e-04
8.91e-02
5.74e-02
2.15e-01
1.95e-03
3.77e-06
1.70e-05
3.83e-04
2.83e-06
1.88e-06
1.59e-04
4.77e-05
2.32e-04
1.13e-03
2.83e-06
1.51e-05
1.88e-06
% of process
group total
0.33%
0.77%
0.24%
0.98%
26.79%
1.82%
0.64%
8.56%
3.32%
10.24%
6.52%
22.80%
0.09%
0.51%
2.35%
12.77%
1.28%
100.00%
11.75%
14.84%
5.09%
0.29%
41.37%
26.66%
100.00%
32.61%
0.06%
0.28%
6.40%
0.05%
0.03%
2.65%
0.80%
3.88%
18.83%
0.05%
0.25%
0.03%
% of grand total
25.07%
1.71%
2-143
-------
2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
Table 2-62. LCD manufacturing stage solid waste outputs
Material
Process Group
parts cleaner solvent
Plating process sludge
Potassium Carbonate
sludge (calcium fluoride, CaF2)
Sludge from LCD glass mfg
Sodium Carbonate
Unspecified sludge
Waste alkali, unspecified
Waste LCD glass
Waste oil
Waste refractory
Total
Backlight
Broken CCFL
Cardboard
Polyethylene, foamed
Polyethylene/polypropylene waste
Unspecified nonhazardous waste
Waste backlight casing (PC)
Waste backlight light guide (PMMA)
Total
PWB
PWB-Drill dust
Unspecified solid waste
Unspecified solid waste
Total
Japanese grid
Coal waste
Dust/sludge
Fly/bottom ash
Total
U.S. grid
Coal waste
Dust/sludge
Fly/bottom ash
Total
Fuels
Aluminum scrap
Aluminum scrap, Wabash 319
Bauxite residues
FGD sludge
Mineral waste
Disposition
recycling/reuse
landfill
landfill
recycling/reuse
landfill
landfill
landfill
treatment
landfill
treatment
landfill
landfill
treatment
treatment
treatment
recycling/reuse
landfill
landfill
landfill
recycling/reuse
treatment
landfill
landfill
landfill
landfill
landfill
landfill
recycling/reuse
recycling/reuse
landfill
landfill
landfill
Quantity (kg/
functional unit)
3.77e-06
1.52e-05
1.53e-04
8.13e-04
4.06e-05
1.53e-04
3.56e-04
1.95e-06
8.70e-05
3.03e-04
1.13e-04
5.98e-03
2.69e-07
1.82e-05
9.99e-04
2.72e-03
1.26e-04
1.46e-05
1.52e-03
5.40e-03
6.59e-03
1.91e-01
1.62e+00
1.81e+00
2.18e+00
8.42e-01
5.45e-01
3.57e+00
9.85e-02
3.81e-02
2.46e-02
1.61e-01
8.77e-06
2.37e-08
5.87e-04
1.09e-02
1.26e-04
% of process
group total
0.06%
0.25%
2.55%
13.59%
0.68%
2.55%
5.95%
0.03%
1.45%
5.07%
1.89%
100.00%
0.01%
0.34%
18.50%
50.45%
2.32%
0.27%
28.12%
100.00%
0.36%
10.53%
89.11%
100.00%
61.12%
23.59%
15.28%
100.00%
61.10%
23.63%
15.27%
100.00%
0.01%
0.01%
0.02%
0.30%
O.01%
% of grand total
0.05%
0.04%
14.40%
28.34%
1.28%
2-144
-------
2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
Table 2-62. LCD manufacturing stage solid waste outputs
Material
Process Group
Mixed industrial (waste)
Non toxic chemical waste (unspecified)
Slag and ash
Slag and ash
Unspecified solid waste (incinerated)
Unspecified waste
Total
Grand Total
Disposition
landfill
landfill
landfill
recycling/reuse
treatment
landfill
Quantity (kg/
functional unit)
4.83e-02
2.95e-05
3.40e+00
3.49e-02
6.44e-04
1.72e-01
3.66e+00
1.26e+01
% of process
group total
1.32%
<0.01%
92.69%
0.95%
0.02%
4.70%
100.00%
% of grand total
29.10%
100.00%
Table 2-63. LCD manufacturing stage radioactive waste outputs
Material
Process Group
Japanese grid
Low-level radioactive waste
Uranium, depleted
Total
U.S. grid
Low-level radioactive waste
Uranium, depleted
Total
Grand Total
Disposition
landfill
landfill
landfill
landfill
Quantity (kg/
functional unit)
3.71e-04
l.lle-04
4.82e-04
3.40e-06
1.02e-06
4.42e-06
4.87e-04
% of process
group total
76.93%
23.07%
100.00%
76.93%
23.07%
100.00%
% of grand total
99.09%
0.91%
100.00%
2-145
-------
2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
Table 2-64. LCD manufacturing stage radioactivity outputs
Material
Process Group
Japanese grid
Antimony- 124 (isotope)
Antimony- 125 (isotope)
Argon-41 (isotope)
Barium-140 (isotope)
Bromine-89 (isotope)
Bromine-90 (isotope)
Cesium- 134 (isotope)
Cesium- 134 (isotope)
Cesium- 137 (isotope)
Cesium- 137 (isotope)
Chromium-51 (isotope)
Chromium-51 (isotope)
Cobalt-57 (isotope)
Cobalt-57 (isotope)
Cobalt-58 (isotope)
Cobalt-58 (isotope)
Cobalt-60 (isotope)
Cobalt-80 (isotope)
Iodine-131 (isotope)
Iodine-131 (isotope)
Iodine- 132 (isotope)
Iodine- 132 (isotope)
Iodine-133 (isotope)
Iodine-133 (isotope)
Iodine- 134 (isotope)
Iodine- 135 (isotope)
Iodine-135 (isotope)
Iron-55 (isotope)
Iron-59 (isotope)
Krypton-85 (isotope)
Krypton-85M (isotope)
Krypton-85M (isotope)
Krypton-87 (isotope)
Krypton-88 (isotope)
Lanthanum- 140 (isotope)
Manganese-54 (isotope)
Manganese-54 (isotope)
Molybdenum-99 (isotope)
Niobium-95 (isotope)
Niobium-95 (isotope)
Rubidium-88 (isotope)
Disposition
treatment
treatment
air
treatment
air
air
air
treatment
air
treatment
air
treatment
air
treatment
air
treatment
air
treatment
air
treatment
air
treatment
air
treatment
air
air
treatment
treatment
treatment
air
air
treatment
air
air
treatment
air
treatment
treatment
air
treatment
air
Quantity (Bq/
functional unit)
1.67e+00
6.63e+00
3.37e+03
1.23e-01
3.90e-04
1.59e-04
1.07e-02
4.45e+00
8.08e-02
6.69e+00
2.11e-01
8.02e+00
5.68e-04
1.94e-01
7.26e-03
7.90e+01
5.46e-02
2.07e+01
2.55e-01
3.70e+00
5.18e-02
1.40e+00
2.37e+02
1.59e+00
2.686-01
1.35e-02
1.14e+00
1.89e+01
9.70e-01
5.59e+03
2.71e+02
5.00e+00
l.Ole+02
4.73e+02
1.326-01
3.00e-03
5.29e+00
9.98e+06
1.19e-04
1.36e+00
l.lle+00
% of process
group total
<0.01%
<0.01%
0.03%
<0.01%
0.01%
0.01%
O.01%
O.01%
O.01%
O.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.06%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
98.42%
O.01%
O.01%
O.01%
% of grand total
2-146
-------
2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
Table 2-64. LCD manufacturing stage radioactivity outputs
Material
Process Group
Ruthenium- 103 (isotope)
Silver-llOM (isotope)
Silver-llOM (isotope)
Sodium-24 (isotope)
Strontium-89 (isotope)
Strontium-90 (isotope)
Strontium-95 (isotope)
Sulfur- 136 (isotope)
Technetium-99M (isotope)
Technetium-99M (isotope)
Tin-113 (isotope)
Tritium-3 (isotope)
Tritium-3 (isotope)
Xenon-13 1M (isotope)
Xenon-13 1M (isotope)
Xenon- 13 3 (isotope)
Xenon- 13 3 (isotope)
Xenon-133M (isotope)
Xenon-133M (isotope)
Xenon- 13 5 (isotope)
Xenon- 13 5 (isotope)
Xenon-135M (isotope)
Xenon- 13 8 (isotope)
Zinc-85 (isotope)
Zirconium-95 (isotope)
Total
U.S. grid
Antimony- 124 (isotope)
Antimony- 125 (isotope)
Argon-41 (isotope)
Barium-140 (isotope)
Bromine-89 (isotope)
Bromine-90 (isotope)
Cesium- 134 (isotope)
Cesium- 134 (isotope)
Cesium- 136 (isotope)
Cesium- 137 (isotope)
Cesium-137 (isotope)
Chromium-51 (isotope)
Chromium-51 (isotope)
Cobalt-57 (isotope)
Cobalt-57 (isotope)
Disposition
treatment
air
treatment
treatment
treatment
treatment
treatment
treatment
air
treatment
treatment
air
treatment
air
treatment
air
treatment
air
treatment
air
treatment
air
air
treatment
air
treatment
treatment
air
treatment
air
air
air
treatment
treatment
air
treatment
air
treatment
air
treatment
Quantity (Bq/
functional unit)
1.67e-01
3.56e-06
1.94e+00
2.96e-01
3.20e-01
7.52e-02
8.29e-01
1.78e-01
1.60e-05
1.16e-01
1.84e-01
7.90e+03
5.91e+04
4.56e+02
6.08e+01
4.37e+03
9.34e+03
6.58e+04
7.65e+01
2.48e+03
6.97e+01
4.74e+01
1.57e+02
8.92e-02
3.08e-04
l.Ole+07
1.53e-02
6.09e-02
3.09e+01
1.13e-03
3.58e-06
1.45e-06
9.82e-05
4.09e-02
1.75e-03
7.41e-04
6.13e-02
1.94e-03
7.36e-02
5.21e-06
1.78e-03
% of process
group total
0.01%
<0.01%
<0.01%
<0.01%
<0.01%
<0.01%
<0.01%
<0.01%
<0.01%
<0.01%
<0.01%
0.08%
0.58%
<0.01%
0.01%
0.04%
0.09%
0.65%
O.01%
0.02%
0.01%
0.01%
0.01%
0.01%
O.01%
100.00%
0.01%
0.01%
0.03%
O.01%
O.01%
O.01%
O.01%
O.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
% of grand total
99.09%
2-147
-------
2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
Table 2-64. LCD manufacturing stage radioactivity outputs
Material
Process Group
Cobalt-58 (isotope)
Cobalt-58 (isotope)
Cobalt-60 (isotope)
Cobalt-80 (isotope)
Iodine-131 (isotope)
Iodine-131 (isotope)
Iodine- 132 (isotope)
Iodine- 132 (isotope)
Iodine-133 (isotope)
Iodine-133 (isotope)
Iodine- 134 (isotope)
Iodine-135 (isotope)
Iodine-135 (isotope)
Iron-55 (isotope)
Iron-59 (isotope)
Krypton-85 (isotope)
Krypton-85M (isotope)
Krypton-85M (isotope)
Krypton-87 (isotope)
Krypton-88 (isotope)
Lanthanum- 140 (isotope)
Manganese-54 (isotope)
Manganese-54 (isotope)
Molybdenum-99 (isotope)
Niobium-95 (isotope)
Niobium-95 (isotope)
Rubidium-88 (isotope)
Ruthenium- 103 (isotope)
Silver- 110M (isotope)
Silver- 110M (isotope)
Sodium-24 (isotope)
Strontium-89 (isotope)
Strontium-90 (isotope)
Strontium-95 (isotope)
Sulfur- 136 (isotope)
Technetium-99M (isotope)
Technetium-99M (isotope)
Tin-113 (isotope)
Tritium-3 (isotope)
Tritium-3 (isotope)
Xenon-13 1M (isotope)
Xenon-13 1M (isotope)
Disposition
air
treatment
air
treatment
air
treatment
air
treatment
air
treatment
air
air
treatment
treatment
treatment
air
air
treatment
air
air
treatment
air
treatment
treatment
air
treatment
air
treatment
air
treatment
treatment
treatment
treatment
treatment
treatment
air
treatment
treatment
air
treatment
air
treatment
Quantity (Bq/
functional unit)
6.65e+00
7.25e-01
5.01e-04
1.90e-01
2.34e-03
3.39e-02
4.75e-04
1.28e-02
2.17e+00
1.45e-02
2.46e-03
1.24e-04
1.04e-02
1.73e-01
8.90e-03
5.13e+01
2.48e+00
4.58e-02
9.25e-01
4.34e+00
1.21e-03
2.75e-05
4.85e-02
9.15e+04
1.09e-06
1.25e-02
1.02e-02
1.53e-03
3.26e-08
1.78e-02
2.72e-03
2.93e-03
6.90e-04
7.60e-03
1.64e-03
1.47e-07
1.06e-03
1.68e-03
7.25e+01
5.42e+02
4.18e+00
5.58e-01
% of process
group total
0.01%
<0.01%
<0.01%
<0.01%
<0.01%
<0.01%
<0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.06%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
98.41%
O.01%
O.01%
O.01%
O.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.01%
0.08%
0.58%
0.01%
O.01%
% of grand total
2-148
-------
2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
Table 2-64. LCD manufacturing stage radioactivity outputs
Material
Process Group
Xenon- 13 3 (isotope)
Xenon- 13 3 (isotope)
Xenon-133M (isotope)
Xenon-133M (isotope)
Xenon- 13 5 (isotope)
Xenon- 13 5 (isotope)
Xenon-135M (isotope)
Xenon- 13 8 (isotope)
Zinc-85 (isotope)
Zirconium-95 (isotope)
Total
Fuels
Radioactive substance (unspecified)
Radioactive substance (unspecified)
Total
Grand Total
Disposition
air
treatment
air
treatment
air
treatment
air
air
treatment
air
air
surface water
Quantity (Bq/
functional unit)
6.04e+02
8.57e+01
4.01e+01
7.02e-01
2.28e+01
6.39e-01
4.35e-01
1.44e+00
8.18e-04
2.82e-06
9.30e+04
4.44e+01
4.116-01
4.48e+01
1.02e+07
% of process
group total
0.65%
0.09%
0.04%
<0.01%
0.02%
0.01%
0.01%
0.01%
0.01%
O.01%
100.00%
99.08%
0.92%
100.00%
% of grand total
0.91%
0.00%
100.00%
2-149
-------
2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
LCD manufacturing - primary material
~ 25-,
f 20-
TO
§ 15'
£ in- 7.50
0 101
,= 5 • 0.32 0.28 0.40
Bl t 1 8 1
II !| | I *
8
LCD mfg. process group
Figure 2-51. LCD manufacturing primary
inputs
16.2
0.38
23.1
Q) "D (/)
$ -o '°> 1
a'§> S
ra
— j
material inputs
LCD manufacturing
±j 250 -, 203
"re 150 -
o IOC-
'S 50 • 0.322
^3 v ' '
*™ ° "5 ^
_§^ "c ^ "oj ^
i i | §.
E
o
o
Figure 2-52
0.009
LCD glass
LCD
- ancillary material inputs
0.001 0.512 0.148 0.007
•£ m
m
Q
O
_i
8.3E-06 3-58
0.17 0.00 0.00 | 1
I I
^ CD 0 "D (/)
D) § S '£. "0
= n_ ¥ "0 ^ =!
1 a'& S
m ro
LCD mfg. process group
Figure 2-53. LCD manufacturing fuel inputs
2-150
-------
2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
LCD
.•H 300 -, 259
C
3
1 200-
0
C 100-
£
^ n
46.4
I I
t 0 m
£3 c
'c "° 0
-------
2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
LCD manufacturing - air emissions
x 60 1
§ 50 -
TO 40 -
5 30 -
c 20 -
1 10-
* 0 -I
52.2
0.03
1-8 5.9E-03 0.13 1.7E-05
0.87
t ^ CO ~D (/)
I! i! I f ! B ! 1
Q- p- O 00 jo
8 ~" LCD mfg. process group
Figure 2-59. LCD manufacturing water pollutant outputs
2-152
-------
2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
LCD
+- 5 1
1 4-
c 3 -
O
t> 2-
B)
•* o -
4
manufacturing - hazardous waste outputs
.3E+00
1.1E-01
^ — -2
1= "a "aj a)
0 ° C £
2 E £ |
8
Figure
8.0E-04
ra
D)
Q
O
2-60. LCD
2.1E-02
D)
O
ra
CD
LCD mfg.
2.0E-01 o.OE+00 O.OE+00
CD 0) T3
§ W '1=
Q. c ^ ™
ra
process group
3.0E-02
CO
-------
2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
Of the total 49 kg of primary materials per functional unit in the manufacturing stage, the
fuels production contributes the greatest (23.1 kg/functional unit), followed by the Japanese
electric grid (16.2 kg/functional unit) (Figure 2-51 and Table 2-56). Nearly all (203 out of 204
kg/functional unit) of the ancillary materials used during manufacturing are from the
monitor/module process group (Figure 2-52 and Table 2-57). Liquified natural gas (LNG)
constitutes about 96% (194 kg/functional unit) of the total ancillary materials in the
monitor/module process group. As stated earlier, this is not used to calculate energy impacts.
Of the utility inputs, electricity and water inputs were greatest in the monitor/module
manufacturing processes; fuels were greatest in the LCD glass manufacturing process group
(Figures 2-53, 2-54, and 2-55). Sixty-three percent of the fuel inputs are from the LCD glass
manufacturing process group. Within that group, the use of LPG clearly dominates at about 16.2
kg/functional unit (over 99% of the LCD glass fuel inputs) (Table 2-58).6 The monitor/module
manufacturing fuel inputs are about 20% of the total manufacturing fuel inputs (5.2 kg/functional
unit). About 259 MJ/functional unit of electricity in the LCD manufacturing stage are from the
monitor/module processes7, or 82% of all manufacturing electricity (Figure 2-54). The total
energy, which converts fuel mass into energy and adds that to the electrical energy, is greatest in
the LCD glass manufacturing processes and contributes 705 MJ/functional unit to the 1,440
MJ/functional unit in the manufacturing stage (Figure 2-56). Water inputs are most significant
in the monitor/module manufacturing process, contributing 1,080 kg (or liter)/functional unit
(Figure 2-55), which is 50% of all the manufacturing water inputs. The fuels production and
panel components process groups contribute about 24% and 10% to the water manufacturing
inputs, respectively.
For outputs from the manufacturing stage, the mass of air emissions are dominated by the
generation of electricity (Figure 2-57). Individual material (pollutant) contributions for each
process group are presented in Table 2-59. Wastewater outputs (i.e., the volume or mass of
wastewater released) are greatest for the monitor/module manufacturing processes (92%)
(Figure 2-58), but only 21% of the chemical pollutants in the wastewater streams come from
those processes (Figure 2-59). Table 2-60 shows the individual contributions from each
material.
Hazardous wastes from the LCD manufacturing stage dominated over other life-cycle
stages, and within the manufacturing stage, the monitor/module processes had the greatest
hazardous waste outputs by mass (4.3 kg/functional unit) (Figure 2-60). The greatest
contributors by mass are isopropyl alcohol (a total of 2.1 kg/functional unit, or 49% of all wastes
from the monitor/module manufacturing processes) (Table 2-61). These wastes, however, are
recycled and although they are a large portion of the inventory, they will not affect the impact
assessment (to be presented in Chapter 3) as they are not directly released to the environment.
Solid wastes generated during the manufacturing stage were only about 21% of the
overall solid wastes generated throughout the LCD life-cycle, as was shown earlier in
Note: An industry participant questioned the large fuel contribution reported here; however, further
discussions with industry supported that no valid reason could justify removing these data. Glass energy inputs are
evaluated in a sensitivity analysis (see Section 2.7.3 and 3.4).
7 This amount of electricity is consistent with the industry participant that expressed doubt in the large fuel
energy contribution and subsequent overall energy use amount in module manufacturing.
2-154
-------
2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
Figure 2-48. Within the manufacturing stage, the fuels production, Japanese grid and
monitor/module manufacturing process groups are all major contributors to the solid waste
outputs (Figure 2-61). The individual material contributions are provided in Table 2-62.
Radioactive waste and radioactivity are directly related to the electricity generation
process and therefore, only the Japanese and U.S. electric grid processes generate these outputs
in the manufacturing stage. Tables 2-63 and 2-64 show that more radioactive wastes and
radioactivity are from the Japanese electric grid. This is a result of more manufacturing
processes being in Japan, as modeled in this project, as well as the greater fraction of nuclear
power in the Japanese electric grid.
2.7.2 Relative Data Quality
Sections 2.2 through 2.6 (and associated appendices) discuss the data quality and data
limitations for each life-cycle stage. Several factors contribute to the overall quality for an entire
life-cycle stage. For example, the manufacturing stage includes several different processes that
were collected from several different companies. The quality of one data set from one company
may be very different from that of another company. Relative data quality estimates have been
made for each life-cycle stage, including electricity generation, which is included in more than
one life-cycle stage (Table 2-65). In addition, transportation data quality is listed in Table 2-65,
although it has been excluded from the analysis due to the very low data quality.
Table 2-65. Relative data quality
Life-cycle stage
Upstream
Manufacturing
Use
EOL
Electricity generation
Transportation
Relative data quality
Moderate
Moderate to high
Moderate to high
Low to moderate
High
Very low
2.7.3 Sensitivity Analyses
The inventory results presented above in Section 2.7.1 are the "baseline" results in this
study. The baseline scenario includes the parameters/assumptions presented in the
methodologies for the effective life scenario. However, due to assumptions and uncertainties in
this LCA, as in any LCA, sensitivity analyses on the baseline results have been conducted. Four
areas have been identified where sensitivity analyses were most warranted:
• use stage lifespan assumptions;
• glass manufacturing energy inputs;
• LCD monitor/module manufacturing energy inputs, and
• LCD EOL disposition assumptions.
Selected sensitivity analyses were chosen based on the data with either the greatest uncertainties
or with a large uncertainty and a major contributor to the inventory results. The matrix in Table
2-155
-------
2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
2-66 shows the different sensitivity analyses or scenarios that are considered in the impact
assessment results. Discussions of the sensitivity analyses for manufactured life (use stage),
glass manufacturing energy inputs, LCD monitor manufacturing energy inputs, and LCD EOL
inventories follow in this section. Complete inventories of each sensitivity analysis scenario are
not presented; however, the effects determined in the LCIA results of the sensitivity analyses are
shown in Chapter 3 (see Section 3.4).
Table 2-66. List of sensitivity analysis scenarios
Monitor
type
Sensitivity analysis scenario
Baseline analyses (for reference)
CRT
LCD
Effective life scenario with average glass energy inputs (all glass manufacturing energy data used)
Effective life scenario with average glass energy inputs (all glass manufacturing energy data used)
and outliers in the LCD module manufacturing energy data removed
Sensitivity analyses
CRT
LCD
CRT
LCD
LCD
LCD
Manufactured life scenario same as baseline except lifespan is based on manufactured life instead of
effective life, which results in some revised functional equivalency calculations (see Section 2.7.3. 1
below)
Manufactured life scenario same as baseline except lifespan is based on manufactured life, which
results in some revised functional equivalency calculations (see Section 2.7.3. 1 below)
Modified glass energy scenario same as baseline except comparatively high glass manufacturing
energy inputs are removed
Modified glass energy scenario same as baseline except comparatively high glass manufacturing
energy inputs are removed
Modified LCD module energy scenario same as baseline except LCD monitor/ module
manufacturing energy outliers are included in the average
Modifed LCD EOL scenario same as baseline except LCD EOL dispositions are modified
2.7.3.1 Manufactured life scenario
To address uncertainties in the use stage lifespan assumptions, we applied the
manufacturing life scenario to the CRT and LCD life-cycle profiles. (See Section 2.4 for a
discussion of the product use stage and the differences in the "effective life" versus
"manufactured life" life span assumptions.) Recall that the LCD manufactured life (45,000
hours) is 3.6 times greater than the CRT manufactured life (12,500 hours). In an LCA,
comparisons are made based on functional equivalency. Therefore, if one monitor will operate
for a longer period of time than another, impacts should be based on an equivalent use. Thus,
based on equivalent use periods, under the manufactured life scenario 3.6 CRTs would need to
be manufactured for every LCD. This was incorporated into the profile analysis for the
comparative manufactured life LCA. Similarly, on average, 1.4 LCD backlights (which can be
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2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
cost-effectively replaced) will be needed during the manufactured lifetime of an LCD monitor.
This was also incorporated into the profile. Thus, the following modifications were made:
change the CRT electricity input in the use stage from 635 kWh (2,286 MJ) to 788 kWh
(2,837 MJ);8
• change the LCD electricity input in the use stage from 237 kWh (853 MJ) to 1,035 kWh
(3,726 MJ);
• increase the manufacturing of CRTs by a factor of 3.6 to account for the functional
equivalency of CRTs and LCDs. This was done by increasing the functional unit (22 kg
CRT monitor) by a factor of 3.6, which equates to manufacturing 3.6 times more CRTs
than in the baseline case; and
• increase the manufacturing of the LCD backlight lamp by a factor of 1.4 to account for
the functional equivalency of LCDs and CRTs. This was done by increasing the
backlight lamp mass (0.0023 kg), which is an input to the backlight unit assembly
process, by a factor of 1.4.
Note that functional equivalency modification requires that the manufactured life scenario results
be used only when comparing the CRT and LCD. These results cannot be accurately used to
compare EL to ML for CRT or LCD. LCIA results of the sensitivity analysis are presented in
Chapter 3.
2.7.3.2 Modified glass energy scenario
In the second case, the energy input values for CRT glass manufacturing (and
consequently LCD glass manufacturing) were considered uncertain due to the large discrepancy
in fuel and electricity values among the individual data sets. The baseline case uses the average
of the data supplied and confirmed by the companies who supplied the data. However, because
one set of data was significantly higher, that one set of data was removed from the profile for the
sensitivity analysis. (A statistical evaluation of the glass manufacturing data for outliers could
not be conducted because there were not enough data sets.)
In the baseline scenario, the averaged primary data from manufacturers of total energy to
produce a kilogram of CRT or LCD glass was 1,560 MJ (433 kWh) of energy, with only 0.3% of
that as electrical energy. The sensitivity analysis scenario assumes 16.3 MJ (4.5 kWh) per
kilogram of glass produced, with approximately 30% as electrical energy. The majority of the
fuel energy in the baseline scenario was from LPG. The energy consumption values can be
compared to estimates for the entire glass industry, which includes the more prevalent general
flat glass, as well as speciality glasses, such as CRT and LCD glass. In a report of the Glass
Technology Roadmap Workshop (Energetics Inc. 1997), it was estimated that in practice, about
1.1 MJ of energy are required to melt a kilogram of glass; and electrical energy contributes
approximately 13% of the total process energy requirements from glass production, as reported
in 1994. Although this does not translate into energy requirements for CRT or LCD glass, it
suggests the baseline data collected for this analysis may be inflated. Therefore, the sensitivity
This represents the electricity use for a 12,500 hour life span. This figure is then multiplied by a factor of
3.6 in the functional equivalency calculations (see third bullet, below).
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2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
analysis uses revised energy input values for glass production, but it is also not known whether
these values represent the true energy requirements for CRT and LCD glass production. The
sensitivity analysis is considered a lower bound of energy requirements for monitor glass
production.
2.7.3.3 Modified LCD module energy scenario
LCD monitor/module manufacturing energy was another area of relatively large
uncertainty and variability in the inventory data. The CDP received seven sets of LCD
monitor/module manufacturing data from five companies in Japan and two in Korea. Of these,
the manufacturing energy data from one company in Korea was incomplete and could not be
used. For the remaining six data sets, total energy inputs ranged from 330 MJ to 7,310 MJ, with
a mean and standard deviation of 2,269 MJ and 2,906 MJ, respectively. Given the wide
variability in the data and large standard deviation, CDP researchers evaluated the data for
outliers by breaking the total energy data points into quartile ranges. Minor outliers are then
those within a certain range of multipliers beyond the middle 50 percent of the distribution. That
is, the interquartile range (IQR) (i.e., the range of values representing the middle 50 percent)
multiplied by 1.5 is the lower bound of the minor outlier and the IQR times three is the upper
bound of the minor outlier. Anything beyond IQR times three is a major outlier. Using this
approach, one data set was found to be a minor outlier and another was found to be a major
outlier. These outliers were excluded from the averages used in the baseline analysis, but
included in the averages used in the LCD monitor/module manufacturing energy sensitivity
analysis.
Table 2-67 summarizes the energy inputs for the LCD monitor/module manufacturing
process group under the baseline and modified LCD module energy scenarios. Note that total
energy inputs are approximately 4.5 times lower under the baseline scenario. However, because
of the different types of energy (fuel and electricity) employed by different manufacturers, the
mean electric energy is higher for the baseline than the modified energy scenario.
2.7.3.4 LCD End-of-life dispositions
Finally, because very few desktop LCDs have reached their end of life, and usually only
if they have been damaged in some way, very little is known about the percentage of LCDs that
are remanufactured, recycled, landfilled or incinerated. In the baseline scenario, it was assumed
that a certain proportion of monitors go to each EOL disposition. As the functional unit in this
study is one monitor, we used those proportions to represent the probability that one monitor
would go to the respective disposition. To address uncertainties in the allocation of disposition
percentages, a sensitivity analysis was conducted with a different set of final disposition
numbers. Details and assumptions for the sensitivity analysis are provided in Appendix I. Table
2-68 presents the distribution of LCD EOL dispositions assumed under the baseline and modifed
EOL dispositions scenarios. LCIA results for the sensitivity analysis are presented in
Section 3.4.
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2.7 SUMMARY OF LIFE-CYCLE INVENTORY RESULTS
Table 2-67. Energy inputs to the LCD monitor/module manufacturing process group
under the baseline and modified energy scenarios
Total energy
(MJper
monitor)
Electric energy
(MJ per
monitor)
Fuel energy
(MJ per
monitor)
% electric
energy
% fuel energy
Baseline (excludes two outlier data sets from the means used in the inventory)
Range
Mean
Standard
deviation
333 to 934
508
284
199 to 359
259
68
48 to 695
249
300
25 to 88
60
27
12 to 75
40
27
Modified Energy (includes two outlier data sets in the means used in the inventory)
Range
Mean
Standard
deviation
333 to 7,317
2,274
2,906
125 to 359
222
79
48 to 7, 146
2052
2,956
2 to 88
10
36
12 to 98
90
36
Table 2-68. Distribution of LCD EOL dispositions in the baseline and
modified EOL scenarios
Disposition
Incineration
Recycling
Remanufacturing
Hazardous waste landfill
Solid waste landfill
Baseline
15%
15%
15%
5%
50%
Modified
15%
0%
40%
5%
40%
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REFERENCES
REFERENCES
Bocko, P. 2000. Personal communication with P. Bocko, Corning Incorporated and M.L.
Socolof, University of Tennessee Center for Clean Products and Clean Technologies.
Octobers.
CIA (Computer Industry Almanac, Inc.). 1997. Computer Industry Almanac. Arlington
Heights, IL.
Douglas, D. 1999. Personal communication with D. Douglas and E. Korman, Dell, and J.G.
Overly, University of Tennessee Center for Clean Products and Clean Technologies.
March.
Ecobilan. 1999. DEAM, life-cycle inventory database developed by the Ecobilan Group,
copyright 1999.
El A (Energy Information Administration). 1997. Country Energy Data Report for 1997. Web
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EIA. 1999a. Electric Power Monthly, February 1999 (With Data for November 1998).
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EIA. 1999b. "1997 Residential Energy Consumption Survey," Housing Characteristics report.
Web site available at http://www.eia.doe.gov/emeu/consumption/reports.html (under
'Residential Households').
Energetics, Incorporated. 1997. Report of the Glass Technology Roadmap Workshop, April 24-
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Incorporated, Fort Motor Company, Pilkington Libbey-Owens-Ford, Praxair, Inc., and
Techneglas, Incorporated. Columbia, Maryland.
EPA (Environmental Protection Agency). 1996. Compilation of Air Pollutant Emission Factors
(AP-42), Fifth Edition, Volume I. AP-42. January.
EPA. 1998. "Characterization of Municipal Solid Waste in the United States: 1997 Update."
Report No. EPA530-R-98-007.
Fanara, A. 1999. Personal communication with A. Fanara, U.S. Environmental Protection
Agency (EPA) Energy Star Program, and J.G. Overly, University of Tennessee Center
for Clean Products and Clean Technologies. July.
FEPC (Federation of Electric Power Companies). 1996. "Electricity Review Japan: The FEPC."
Web site available at http://www.fepc or jp/erj/data 03.html (1996 data).
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Monitors." Web site available at
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ISO (International Standards Organization). 1996. ISO 14040, Environmental Management -
Life-cycle Assessment Principles and Framework. TC 2071 SC 5N 77. International
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Lapp, J.C. 2000. Personal communication with J.C. Lapp, Corning Incorporated, and M.L.
Socolof, University of Tennessee, Center for Clean Products and Clean Technologies.
October 11 and October 23.
Matthews, H. S., et al. 1991. "Disposition and End-of-Life Options for Personal Computers."
Green Design Initiative Technical Report #97-10. Carnegie Mellon University,
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McConnaughey, M. 1999. Personal communication with M. McConnaughey, ViewSonic, and
J.G. Overly, University of Tennessee, Center for Clean Products and Clean Technologies.
March.
MCC (Microelectronics and Computer Technology Corporation). 1998. Computer Display
Industry and Technology Profile. EPA 744-R-98-005. December.
Nordman, B., M. A. Piette and K. Kinney. 1996. "Measured Energy Savings and Performance
of Power-Managed Personal Computers and Monitors." Presented at the American
Council for an Energy Efficient Economy Summer Study, Pacific Grove, CA.
LBL-38057, UC-1600. August.
NSC (National Safety Council). 1999. Electronic Product Recovery and Recycling Baseline
Report: Recycling of Selected Electronic Products in the United States. Washington,
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ORNL (Oak Ridge National Laboratory). 1994. Report 3: Estimating Externalities of Coal
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ORNL. 1995. ReportS: Estimating Externalities of Nuclear Fuel Cycles. Oak Ridge, TN.
April.
SET AC (Society of Environmental Toxicology and Chemistry). 1994. Life-Cycle Assessment
Data Quality: A Conceptual Framework. SET AC and SET AC Foundation for
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Sharp, J. 2000. Personal communication with J. Sharp, Teredyne Corp., J.G. Overly,
University of Tennessee, Center for Clean Products and Clean Technologies, and M.L.
Socolof, University of Tennessee, Center for Clean Products and Clean Technologies.
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Environment Computer Display Project." International Symposium on Electronics and
the Environment, The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Computer Society Conference Record, May 8-10, San Francisco, CA.
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McFarland and A. Bradley, TORNRC, and R. Dhingra, University of Tennessee, Center
for Clean Products and Clean Technologies. April.
Tsuda, D. 1999. Personal communication with D. Tsuda, Environmental Technologies and
Strategies Department, Apple Computer, Inc., and M.L. Socolof, University of
Tennessee, Center for Clean Products and Clean Technologies. July.
Vorhees, G. 2000. Personal communication with G. Vorhees, Envirocycle, and M.L. Socolof,
University of Tennessee, Center for Clean Products and Clean Technologies. July.
Young, R. 1999. Personal communication with R. Young, Display Search, and M.L. Socolof,
University of Tennessee, Center for Clean Products and Clean Technologies. August.
VP150. 1998. Viewsonic VP150 17" monitor specifications sheet.
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University of Tennessee, Center for Clean Products and Clean Technologies. October 27.
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3.1 METHODOLOGY
Chapter 3
LIFE-CYCLE IMPACT ASSESSMENT
Within LCA, the LCI is a well established methodology; however, LCIA methods are
less well defined and continue to evolve (Barnthouse et a/., 1997; Fava et a/., 1993). For toxicity
impacts in particular, there are some methods being applied in practice (e.g., toxicity potentials,
critical volume, and direct valuation) (Guinee etal., 1996; ILSI, 1996; Curran, 1996), while
others are in development. However, there is currently no general consensus among the LCA
community as to one method over another. LCIA sophistication has also been discussed in
efforts to determine the appropriate level of analytical sophistication for various types of
decision making requirements (Bare etal., 1999) or one that adequately addresses toxicity
impacts.
Section 3.1 of this chapter presents the University of Tennessee (UT) LCIA
methodology, which takes a more detailed approach to chemical toxicity impacts than some
methods currently being used. Section 3.1 also discusses data sources, data quality, and the
limitations and uncertainties in the LCIA methodology. The UT methodology calculates life-
cycle impact category indicators for a number of impact categories, including several traditional
LCA impact categories (e.g., global warming, stratospheric ozone depletion, photochemical
smog, and energy consumption). Furthermore, the method calculates relative category indicators
for potential chronic human health, aquatic ecotoxicity, and terrestrial ecotoxicity impacts in
order to address interest in human and ecological toxicity and to fill a common gap in LCIAs.
Work conducted for Saturn Corporation and the EPA Office of Research and Development by
the UT Center for Clean Products and Clean Technologies has provided the basis for much of
this methodology (Swanson, 2001).
Section 3.2 of this chapter describes the data management and analysis software used to
calculate LCIA results. Section 3.3 presents the baseline LCIA results for both the CRT and the
LCD. Baseline results are presented by impact category and include a discussion of the specific
limitations and uncertainties in each category. Section 3.4 presents sensitivity analyses of the
baseline results.
3.1 METHODOLOGY
In its simplest form, LCIA is the evaluation of potential impacts to any system as a result
of some action. LCIAs generally classify the consumption and loading data from the inventory
stage to various impact categories. Characterization methods are then used to quantify the
magnitude of the contribution that loading or consumption could have in producing the
associated impact. LCIA does not seek to determine actual impacts, but rather to link the data
gathered from the LCI to impact categories and to quantify the relative magnitude of
contribution to the impact category (Fava et a/., 1993; Barnthouse et a/., 1997). Further, impacts
in different impact categories are generally calculated based on differing scales and therefore
cannot be directly compared.
Conceptually, there are three major phases of LCIA, as defined by the Society of
Environmental Toxicology and Chemistry (SETAC) (Fava et a/., 1993):
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3.1 METHODOLOGY
• Classification - The process of assignment and initial aggregation of data from inventory
studies to impact categories (e.g., greenhouse gases or ozone depletion compounds).
• Characterization - The analysis and estimation of the magnitudes of potential impacts
for each impact category, derived through application of specific impact assessment
tools. In the CDP, "impact scores" are calculated for inventory items that have been
classified into various impact categories and then aggregated into life-cycle impact
category indicators.
• Valuation - The assignment of relative values or weights to different impacts and their
integration across impact categories to allow decision makers to assimilate and consider
the full range of relevant impact scores across impact categories.
The international standard for life cycle impact assessment, ISO 14042, considers
classification and characterization to be mandatory elements of LCIA. Valuation or weighting is
an optional element to be included depending on the goals and scope of the study. The CDP
addresses the first two LCIA steps and leaves the valuation step to industry or others. In
addition, further qualitative risk screening of selected materials is conducted beyond the
traditional LCIA "characterization" phase in Chapter 4. The methodologies for life-cycle impact
classification and characterization are described in Sections 3.1.1 and 3.1.2, respectively.
Sections 3.1.3 and 3.1.4 address data sources and data quality, and limitations and uncertainties
associated with the LCIA methodology.
3.1.1 Classification
In the first step of classification, impact categories of interest are identified in the scoping
phase of the LCA. The categories to be included in the CDP LCIA are listed below:
• Natural Resource Impacts
renewable resource use
nonrenewable materials use/depletion
energy use
solid waste landfill use
hazardous waste landfill use
radioactive waste landfill use
• Abiotic Ecosystem Impacts
global warming
stratospheric ozone depletion
photochemical smog
acidification
air quality (particulate matter loading)
water eutrophication (nutrient enrichment)
water quality (biological oxygen demand [BOD] and total suspended solids
[TSS])
radioactivity
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3.1 METHODOLOGY
• Potential Human Health and Ecotoxicity Impacts
chronic human health effects (occupational and public)
aesthetic impacts (odor)
aquatic ecotoxicity
terrestrial ecotoxicity
The second step of classification is assigning inventory inputs or outputs to applicable
impact categories. Classification depends on whether the inventory item is an input or output,
what the disposition of the output is, and in some cases the material properties for a particular
inventory item. Figure 3-1 shows a conceptual model of classification for the CDP. Table 3-1
presents the inventory types and material properties used to define which impact category will be
applicable to an inventory item. One inventory item may have multiple properties and therefore
would have multiple impacts. For example, methane is both a global warming gas and has the
potential to create photochemical oxidants (smog formation).
Output inventory items from a process may have varying dispositions, such as direct
release (to air, water or land), treatment, or recycle/reuse. Outputs with direct release
dispositions are classified into impact categories for which impacts will be calculated in the
characterization phase of the LCIA. Outputs sent to treatment are considered inputs to a
treatment process and impacts are not calculated until direct releases from that process occur.
Similarly, outputs to recycle/reuse are considered inputs to previous processes and impacts are
not directly calculated for outputs that go to recycle/reuse. Figure 3-1 graphically depicts the
relationships between inventory type, dispositions, and impact categories. Note that a product is
also an output of a process; however, product outputs are not used to calculate any impacts.
Once impact categories for each inventory item are classified, life-cycle impact category
indicators are quantitatively estimated through the characterization step.
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3.1 METHODOLOGY
Inventory
data type
Disposition
General
impact
categories
Chemical
properties
Specific
impact
categories'
Resource/
energy use
Certain chemibal properties
(e.g., greennouse
indicate Which
gases will have a
specific irjipact
global warming
categories
impact score)
will be calculated
(see Table 3-1).
* Equations for calculating impact scores for each impact category are provided in Sect. 3.1.2.
** Excluded from the scope of the CDP; however, included in the UT Life-Cycle Design Toolkit.
Note, radioactivity (not depicted in this figure) is classified for radioactive isotope outputs to air, water or landfill.
Figure 3-1. Impact classification conceptual model
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3.1 METHODOLOGY
Table 3-1. Inventory types and properties for classifying inventory items
into impact categories
Inventory Type
Input
Output
Chemical/Material Properties
Impact Category
Natural Resource Impacts
material, water
material, fuel
electricity, fuel
—
—
—
—
—
solid waste to
landfill
hazardous waste to
landfill
radioactive waste
to landfill
renewable
nonrenewable
energy
RCRA a - defined nonhazardous waste (or
other country -specific definitions)
RCRA a - defined hazardous waste
(or other country-specific definitions)
radioactive waste
renewable resource use
nonrenewable resource
use/depletion
energy use
solid waste landfill use
hazardous waste landfill use
radioactive waste landfill use
Abiotic Ecosystem Impacts
....
....
—
—
— -
—
— -
— -
—
air
air
air
air
air
water
water
water
radioactivity to air,
water, or land
global warming gases
ozone depleting substances
substances that can be photochemically
oxidized
substances that react to form hydrogen
ions (H+)
airparticulates (PM10, TSP) a
substances that contain available nitrogen
or phosphorus
BODa
TSSa
radioactive substance (isotope)
global warming
stratospheric ozone depletion
photochemical smog
acidification
air quality (air particulates)
water eutrophication (nutrient
enrichment)
water quality: BOD
water quality: TSS
radioactivity
Human Health and Ecotoxicity
material
—
— -
— -
—
air, water
air
water
air, water
toxic material
toxic material
odorous material
toxic material
toxic material
chronic human health effects -
occupational
chronic human health effects -
public
aesthetic impacts (odor)
aquatic ecotoxicity
terrestrial ecotoxicity
a Acronyms: Resource Conservation and Recovery Act (RCRA); paniculate matter with average aerodynamic
diameter less than 10 micrometers (PM10); total suspended particulates (TSP); biological oxygen demand (BOD); total
suspended solids (TSS).
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3.1 METHODOLOGY
3.1.2 Characterization
The characterization step of LCIA includes the conversion and aggregation of LCI results
to common units within an impact category. Different assessment tools are used to quantify the
magnitude of potential impacts, depending on the impact category. Three types of approaches
are used in the characterization method for the CDP:
• Loading - An impact score is based on the inventory amount.
• Equivalency - An impact score is based on the inventory amount weighed by a certain
effect, equivalent to a reference chemical.
Full equivalency - all substances are addressed in a unified, technical model.
Partial equivalency - a subset of substances can be converted into equivalency
factors.
• Scoring of inherent properties - An impact score is based on the inventory amount
weighed by a score representing a certain effect for a specific material (e.g., toxicity
impacts are weighed using a toxicity scoring method).
Table 3-2 lists the characterization approach used with each impact category. The
loading approach either uses the direct inventory amount to represent the impact or slightly
modifies the inventory amount to change the units into a meaningful loading estimate. Two
examples are nonrenewable resource depletion and landfill use. Use of nonrenewable resources
are directly estimated as the mass (loading) of that material consumed (input amount). Use of
landfill space applies the mass loading of an output of hazardous, nonhazardous, or radioactive
waste and converts that loading into a volume to estimate the amount of landfill space consumed.
The equivalency method uses equivalency factors that exist for certain impact categories.
Equivalency factors are values that provide a relative measure or weighting that relate an
inventory output amount to some impact category relative to a certain chemical. For example, to
relate an atmospheric release to the global warming impact category, chemical-specific global
warming potential (GWP) equivalency factors are used. GWPs are a measure of the possible
warming effect on the earth's surface arising from the emission of a gas relative to carbon
dioxide (CO2). They are based on atmospheric lifetimes and radiative forcing of different
greenhouse gases.
The scoring of inherent properties method is applied to impact categories that may have
different effects for the same amount of various chemicals, but for which equivalency factors do
not exist or are not widely accepted. The scores are meant to normalize the inventory data to
provide measures of potential impacts. Scoring methods are employed for the human and
ecological toxicity impact categories, based on the CHEMS-1 method described by Swanson et
al. (1997), and presented below. The scoring method provides a hazard value (HV) for each
potentially toxic material, which is then multiplied by the inventory amount to calculate the
toxicity impact score. The aesthetics category directly applies an inherent chemical property
(i.e., odor threshold concentration), but does not convert that value into a relative score, or HV.
Using the various approaches, the UT LCIA method calculates impact scores for each
inventory item for each applicable impact category. Impact scores are therefore based on either
a direct measure of the inventory amount or some modification (e.g., equivalency or scoring) of
3-6
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3.1 METHODOLOGY
that amount based on the potential effect the inventory item may have on a particular impact
category. Impact scores are then aggregated within each impact category to calculate the
various life-cycle impact category indicators.
Inventory amounts are identified on a functional unit basis and then used to calculate
impact scores. For each inventory item, an individual score is calculated for each applicable
impact category. The equations presented in the subsections that follow calculate impacts for
individual inventory items that could later be aggregated as defined by the user. Impact scores
represent relative and incremental changes rather than absolute effects or threshold levels.
Table 3-2. LCIA characterization approaches for the CDP
Impact Category
Characterization Approach
Natural Resource Impacts
Renewable resource use
Nonrenewable materials use/depletion
Energy use
Solid waste landfill use
Hazardous waste landfill use
Radioactive waste landfill use
loading
loading
loading
loading
loading
loading
Abiotic Ecosystem Impacts
Global warming
Stratospheric ozone depletion
Photochemical smog
Acidification
Air quality (paniculate matter)
Water eutrophication (nutrient enrichment)
Water quality (BOD, TSS)
Radioactivity
equivalency (full)
equivalency (full)
equivalency (partial)
equivalency (full)
loading
equivalency (partial)
loading
loading
Human Health and Ecotoxicity
Chronic human health effects - occupational
Chronic human health effects - public
Aesthetic impacts (odor)
Aquatic ecotoxicity
Terrestrial ecotoxicity
scoring of inherent properties
scoring of inherent properties
application of inherent properties
scoring of inherent properties
scoring of inherent properties
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3.1 METHODOLOGY
3.1.2.1 Renewable and nonrenewable resource use
Natural resources are materials that are found in nature in their basic form rather than
being manufactured (e.g., water, minerals, petroleum and wood). Renewable (or flow)
resources, which are those that can be regenerated, are typically biotic resources (e.g., forest
products, other plants or animals) and water. Nonrenewable (or stock) resources are abiotic,
such as mineral ore or fossil fuels. Both of these natural resource impacts are calculated using
the loading approach. Renewable and nonrenewable resource consumption impacts use direct
consumption values (i.e., material mass) from the inventory.
Renewable resource impact scores are based on the following process inputs in the LCI:
primary, ancillary, water, and fuel inputs of renewable materials. To calculate the loading-based
impact scores, the following equation is used:
(ISRR),=[AmtRRX(l-RC)],
where:
ISm equals the impact score for use of renewable resource /' (kg) per functional unit;
Amtm equals the inventory input amount of renewable resource /' (kg) per functional
unit; and
RC equals the fraction recycled content (post industrial and post consumer) of
resource /'.
In the CDP LCI, most manufacturers that provided primary data did not report recycled
content nor was the recycled content available for material inventories from secondary sources.
Therefore, to calculate the impact score for use of renewable resources the recycled content (RC)
was assumed to be zero.
Depletion of materials, which results from the extraction of renewable resources faster
than they are renewed, may occur but is not specifically modeled or identified in the renewable
resource impact score. For the nonrenewable materials use/depletion category, depletion of
materials results from the extraction of nonrenewable resources. Nonrenewable resource impact
scores are based on the amount of primary, ancillary, and fuel inputs of nonrenewable materials.
To calculate the loading-based impact scores the following equation is used:
where:
ISNRR equals the impact score for use of nonrenewable resource /' (NRR) (kg) per
functional unit;
AmtmR equals the inventory input amount of nonrenewable resource /' (kg) per functional unit;
and
RC equals the fraction recycled content (post industrial and post consumer) of
resource /'.
Due to the lack of data on the recycled content of nonrenewable resources, RC was assumed to
be zero.
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3.1.2.2 Energy use
General energy consumption is used as an indicator of potential environmental impacts
from the entire energy generation cycle. Energy use impact scores are based on fuel and
electricity inputs. The impact category indicator is the sum of electrical energy inputs and fuel
energy inputs. Fuel inputs are converted from mass to energy units using the fuel's heat value
(H) and the density (D), presented in Appendix K, Table K-l. The impact score is calculated by:
(ISjs), = AmtEl or [Amtpx (H / D)],
where:
ISE equals the impact score for energy use (MJ) per functional unit;
AmtE equals the inventory input amount of electrical energy used (MJ) per functional
unit;
Amtp equals the inventory input amount of fuel used (kg) per functional unit;
H equals the heat value of fuel /' (MJ/L); and
D equals the density of fuel/'(kg/L).
This category addresses energy use only. The emissions from energy production are outputs
from the energy production process and are classified to applicable impact categories, depending
on the disposition and chemical properties of the outputs (see Classification Section 3.1.1).
3.1.2.3 Landfill use
Landfill impacts are calculated using solid, hazardous, or radioactive waste outputs to
land as volume of landfill space consumed. Solid waste landfill use pertains to the use of
suitable and designated landfill space as a natural resource where municipal waste or
construction debris is accepted. A solid waste landfill impact score is calculated using solid
waste outputs disposed of in a solid waste (nonhazardous) landfill. Impact characterization is
based on the volume of solid waste, determined from the inventory mass amount of waste and
material density of each specific solid waste type:
(ISswi), = (Amtsw/D),
where:
ISSWL equals the impact score for solid waste landfill (SWL) use for waste /' (m3) per
functional unit;
Amtsw equals the inventory output amount of solid waste /' (kg) per functional unit; and
D equals density of waste /' (kg/m3).
Hazardous waste landfill use pertains to the use of suitable and designated landfill space
as a natural resource where hazardous waste, as designated and regulated under the Resource
Conservation and Recovery Act, is accepted. For non-US activities, equivalent hazardous or
special waste landfills are considered for this impact category. Impact scores are characterized
from hazardous waste outputs with a disposition of landfill. Impact characterization is based on
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the volume of hazardous waste, determined from the inventory mass amount of waste and
material density of each specific hazardous waste type:
(fSam}t = (AmtHW/D)1
where:
ISHWL equals the impact score for hazardous waste landfill (HWL) use for waste /' (m3)
per functional unit;
AmtHW equals the inventory output amount of hazardous waste /' (kg) per functional unit;
and
D equals density of waste /' (kg/m3).
Radioactive waste pertains to the suitable and designated landfill space as a natural
resource that accepts radioactive waste. Impacts are characterized from radioactive waste
outputs with a disposition of landfill. Impact characterization is based on the volume of
radioactive waste, determined from the inventory mass amount of waste and material density of
each specific waste.
(ISRwL>, = (AmtRW/D)l
where:
ISRWL equals the impact score for radioactive waste landfill (RWL) use for waste /' (m3)
per functional unit;
AmtRW equals the inventory output amount of radioactive waste /' (kg) per functional unit;
and
D equals density of waste /' (kg/m3).
3.1.2.4 Global warming impacts
The build up CO2 and other greenhouse gases in the atmosphere may generate a
"greenhouse effect" of rising temperature and climate change. Global warming potential (GWP)
refers to the warming (relative to CO2) that chemicals contribute to this effect by trapping the
earth's heat. The impact scores for global warming (global climate change) effects are
calculated using the mass of a global warming gas released to air modified by a GWP
equivalency factor. The GWP equivalency factor is an estimate of a chemical's atmospheric
lifetime and radiative forcing that may contribute to global climate change compared to the
reference chemical CO2. Therefore, GWPs are in units of CO2 equivalents. GWPs have been
published for known global warming chemicals within differing time horizons. The LCIA
methodology being presented in this memorandum uses GWPs having effects in the 100-year
time horizon. Although LCA does not necessarily have a temporal component of the inventory,
these impacts are expected to be far enough into the future that releases occurring throughout the
life cycle of a computer monitor would be within the 100-year time frame. Appendix K, Table
K-2 presents a current list of GWPs as identified by the Intergovernmental Panel on Climate
Change (IPCC) (Houghton et al., 1996). Global warming impact scores are calculated for any
chemicals in the LCI that are found in Appendix K, Table K-2. The equation to calculate the
impact score for an individual chemical is as follows:
(ISGW), = (EFGWP
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where:
ISGW equals the global warming impact score for greenhouse gas chemical / (kg CO2
equivalents) per functional unit;
EFGWP equals the GWP equivalency factor for greenhouse gas chemical /' (CO2
equivalents, 100 year time horizon) (Appendix K, Table K-2); and
Amt^Q equals the inventory output amount of greenhouse gas chemical /' released to air
(kg) per functional unit.
3.1.2.5 Stratospheric ozone depletion
The stratospheric ozone layer filters out harmful ultraviolet radiation from the sun.
Chemicals such as chlorofluorocarbons, if released to the atmosphere, may result in ozone-
destroying chemical reactions. Stratospheric ozone depletion refers to the release of chemicals
that may contribute to this effect. Impact scores are based on the identity and amount of ozone
depleting chemicals released to air. Currently identified ozone depleting chemicals are those
with ozone depletion potentials (ODPs), which measure the change in the ozone column in the
equilibrium state of a substance compared to the reference chemical chlorofluorocarbon (CFC)-
11 (Heijungs et al, 1992; CAAA, 1990). The list of ODPs that are used in this methodology are
provided in Appendix K, Table K-3. The individual chemical impact score for stratospheric
ozone depletion impacts is based on the ODP and inventory amount of the chemical:
(ISoo): = (EFODPxAmtODC>l
where:
ISOD equals the ozone depletion impact score for chemical / (kg CFC-11 equivalents)
per functional unit;
EFODP equals the ODP equivalency factor for chemical /' (CFC-11 equivalents)
(Appendix K, Table K-3); and
AmtODC equals the amount of ozone depleting chemical /' released to air (kg) per
functional unit.
3.1.2.6 Photochemical smog
Photochemical oxidants are produced in the atmosphere from sunlight reacting with
hydrocarbons and nitrogen oxides. At higher concentrations they may cause or aggravate health
problems, plant toxicity, and deterioration of certain materials. Photochemical oxidant creation
potential (POCP) refers to the release of chemicals that may contribute to this effect. The POCP
is based on simulated trajectories of tropospheric ozone production with and without volatile
organic carbons (VOCs) present. The POCP is a measure of a specific chemical compared to the
reference chemical ethene (Heijungs et a/., 1992). The list of chemicals with POCPs to be used
in this methodology are presented in Appendix K, Table K-4. As shown in Table 3-2,
photochemical smog impacts are based on partial equivalency because some chemicals cannot be
converted into POCP equivalency factors. For example, nitrogen oxides do not have a POCP.
However, VOCs are assumed to be the limiting factor and if VOCs are present, there is a
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potential impact. Impact scores are based on the identity and amount of chemicals with POCP
equivalency factors released to the air and the chemical-specific equivalency factor:
(ISPOCP), = (EFpocpxAmtpoc),
where:
ISPOCp equals the photochemical smog impact score for chemical /' (kg ethene
equivalents) per functional unit;
EFpocp equals the POCP equivalency factor for chemical / (ethene equivalents)
(Appendix K, Table K-4); and
Amtpoc equals the amount of smog-creating chemical / released to the air (kg) per
functional unit.
3.1.2.7 Acidification
This refers to the release of chemicals that may contribute to the formation of acid
precipitation. Impact characterization is based on the amount of a chemical released to air that
would cause acidification and the acidification potentials (AP) equivalency factor for that
chemical. The AP equivalency factor is the number of hydrogen ions that can theoretically be
formed per mass unit of the pollutant being released compared to sulfur dioxide (SO2) (Heijungs
et al, 1992; Hauschild and Wenzel, 1997). Appendix K, Table K-5 lists the AP values that will
be used as the basis of calculating acidification impacts. The impact score is calculated by:
(ISAP), = (EFApXAmtAC>1
where:
ISAP equals the impact score for acidification for chemical /' (kg SO2 equivalents) per
functional unit;
EFAP equals the AP equivalency factor for chemical / (SO2 equivalents) (Appendix K,
Table K-5); and
AmtAC equals the amount of acidification chemical /' released to the air (kg) per
functional unit.
3.1.2.8 Air particulates
This refers to the release and build up of particulate matter primarily from combustion
processes. Impact scores are based on particulate release amounts [particulate matter with
average aerodynamic diameter less than 10 micrometers (PM10)] to the air. This size of
particulate matter is most damaging to the respiratory system. Impact characterization is simply
based on the inventory amount of parti culates released to air. This loading impact score is
calculated by:
ISPM = AmtPM
where:
ISPM equals impact score for particulates (kg PM10) per functional unit, and
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AmtPM equals the inventory output amount of parti culate release (PM10) to the air (kg)
per functional unit.
In this equation, PM10 is used to estimate impacts. However, if only total suspended particulates
(TSP) data are available, these data may be used. Note that using TSP data is an overestimation
of PM10 which only refers to the fraction of particulates in the size range below 10 micrometers.
A common conversion factor (TSP to PM10) is not available because the fraction of PM10 varies
depending on the type of particulates.
3.1.2.9 Water eutrophication
Eutrophication (nutrient enrichment) impacts to water are based on the identity and
concentrations of eutrophication chemicals released to surface water after treatment.
Equivalency factors for eutrophication have been developed assuming nitrogen (N) and
phosphorus (P) are the two major limiting nutrients of importance to eutrophication. Therefore,
the partial equivalencies are based on the ratio of N to P in the average composition of algae
(C106H263O110N16P) compared to the reference compound phosphate (PO43") (Heijungs et a/.,
1992; Lindfors et a/., 1995). If the wastewater stream is first sent to a publicly owned treatment
works (POTW), treatment is considered as a separate process and the impact score would be
based on releases from the POTW to surface waters. Impact characterization is based on
eutrophication potentials (EP) (Appendix K, Table K-6) and the inventory amount:
(ISEUTR), = (EFEPxAmtEO>,
where:
ISEUTR equals the impact score for regional water quality impacts from chemical /' (kg
phosphate equivalents) per functional unit;
EFEP equals the EP equivalency factor for chemical /' (phosphate equivalents)
(Appendix K, Table K-6); and
AmtEC equals the inventory output mass (kg) of chemical /' per functional unit of
eutrophication chemical in a wastewater stream released to surface water after
any treatment, if applicable.
3. 1.2. 10 Water quality
Water quality impacts are characterized as surface water impacts due to releases of
wastes causing oxygen depletion and increased turbidity. Two water quality impact scores are
calculated based on the biological oxygen demand (BOD) and total suspended solids (TSS) in
the wastewater streams released to surface water. The impact scores are based on releases to
surface water following any treatment. Using a loading characterization approach, impact
characterization is based on the amount of BOD and TSS in a wastewater stream. The water
quality score equations for each are presented below:
(ISBOD), =
and
(ISTSS), = (AmtTSS),
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where:
ISBOD equals the impact score for BOD water quality impacts for waste stream / (kg) per
functional unit;
AmtBOD equals the inventory output amount of BOD in wastewater stream / released to
surface waters (kg) per functional unit;
ISTSS equals the impact score for TSS water quality impacts for waste stream /' (kg) per
functional unit; and
AmtTSS equals the inventory amount of TSS in wastewater stream /' released to surface
waters (kg) per functional unit.
3.1.2.11 Radioactivity
Radioactivity inventoried as the quantity of an isotope released to the environment is
considered in the radioactivity impact category. These outputs, such as those from the
generation of nuclear energy, can be air, water, or land releases. The radioactivity impact is a
direct loading score measured in Bequerels of radioactivity, and calculated as follows:
(ISrJt = (AmtrJ,
where:
ISrad equals the impact score for radioactivity of isotope /' (Bq) per functional unit; and
Amtrad equals the inventory amount of radioactivity of isotope /' (Bq) per functional unit.
While this impact category uses a loading approach, further refinement of this impact score
calculation in the future could use radioactivity dose conversion factors, which convert
radioactivity quantities (e.g., Bq) into human doses equivalents (e.g., sievert or rem).
3.1.2.12 Potential human health impacts
Human health impacts are defined in the context of life-cycle assessment as relative
measures of potential adverse health effects to humans. Human health impact categories
included in the scope of this LCA are chronic (repeated dose) effects, which include
noncarcinogenic and carcinogenic effects, and aesthetics (although not a health effect per se,
aesthetics pertains to human welfare). Chronic human health effects to both workers and the
public are considered. Quantitative measures of consumer impacts are not included in this LCIA
methodology because there are no direct outputs quantified in the LCI from the use stage of a
computer monitor. The CDP does, however, quantify indirect outputs from energy consumption
(i.e., pollutants released from energy production). In addition, Appendix L qualitatively
discusses direct consumer impacts, such as electromagnetic radiation or eye strain.
The chemical characteristic that classifies inventory items to the human health effects
(and ecotoxicity) categories is toxicity. Toxic chemicals were identified by searching lists of
toxic chemicals [e.g., Toxic Release Inventory (TRI)] and if needed, toxicity databases [e.g.,
Hazardous Substances Data Bank (HSDB)], and Registry of Toxic Effects of Chemical
Substances (RTECS), or other literature. Upon review by the EPA DfE Workgroup (see
Appendix C), several materials in the CDP inventory were excluded from the toxic list if they
are generally accepted as nontoxic. The EPA DfE Workgroup also reviewed the list of
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chemicals that were included in this project as potentially toxic. The list of potentially toxic
chemicals is provided in Appendix K, Table K-8, and chemicals that were excluded from the
toxic list that appear in the CDP inventory are presented in Appendix K, Table K-9.
Human (and ecological) toxicity impact scores are calculated based on a chemical
scoring method modified from CHEMS-1 found in Swanson et al. (1997). To calculate impact
scores, chemical-specific inventory data are required. Any chemical that is assumed to be
potentially toxic is given a toxicity impact score. If toxicity data are unavailable for a chemical,
a mean default toxicity score is given. This is described in further detail below. Ecological
toxicity is presented in Section 3.1.2.13.
Chronic human health effects are potential human health effects occurring from repeated
exposure to toxic agents over a relatively long period of time (i.e., years). These effects could
include carcinogenicity, reproductive toxicity, developmental effects, neurotoxicity,
immunotoxicity, behavioral effects, sensitization, radiation effects, chronic effects to other
specific organs or body systems (e.g., blood, cardiovascular, respiratory, kidney and liver
effects). Impact categories for chronic health effects are divided into worker and public impacts.
Occupational impact scores are based on inventory inputs and public impact scores are based on
inventory outputs.
Chronic occupational health effects
This refers to potential health effects to workers, including cancer, from long-term
repeated exposure to toxic or carcinogenic agents in an occupational setting. For possible
occupational impacts, the identity and amounts of materials/constituents as input to a process are
used. The inputs represent potential exposures and we could assume that a worker would
continue to work at a facility and incur exposures over time. However, the inventory is based on
manufacturing one monitor and does not truly represent chronic exposure. Therefore, the
chronic health effects impact score is more a ranking of the potential of a chemical to cause
chronic effects than a prediction of actual effects.
Chronic occupational health effects scores are based on the identity of toxic chemicals
(or chemical ingredients) found in primary and ancillary inputs from materials processing and
manufacturing life-cycle stages. The distinction between pure chemicals and mixtures is made
implicitly, if possible, by specifying component ingredients of mixtures in the inventory.
The chronic human health impact scores are calculated using hazard values (HVs) for
carcinogenic and for noncarcinogenic effects. The former HV uses cancer slope factors or
cancer weight of evidence (WOE) classifications assigned by EPA and/or the International
Agency for Research on Cancer (IARC) when no slope factor exists. If both an oral and
inhalation slope factor exist, the slope factor representing the larger hazard is chosen. Where no
slope factor is available for a chemical, but there is a WOE classification, the WOE is used to
designate default hazard values as follows: EPA WOE Groups D (not classifiable) and E
(noncarcinogen) and IARC Groups 3 (not classifiable) and 4 (probably not carcinogenic) are
given a hazard value of zero. All other WOE classifications (known, probable, and possible
human carcinogen) are given a default HV of 1 (representative of a mean slope factor) (Table 3-
3). Similarly, materials for which no cancer data exist, but are designated as potentially toxic,
are also given a default value of 1.
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Table 3-3. Hazard values for carcinogenicity weight-of-evidence
if no slope factor is available
EPA
Classification
Group A
Group Bl
Group B2
Group C
Group D
Group E
IARC
Classification
Group 1
Group 2A
N/A
Group 2B
Group 3
Group 4
Description
known human carcinogen
Probable human carcinogen (limited human data)
Probable human carcinogen (from animal data)
Possible human carcinogen
Not classifiable
Noncarcinogenic or probably not carcinogenic
Hazard
Value
1
1
1
1
0
0
N/A: not applicable.
The cancer hazard value for chronic occupational health effects is the greater of the
following:
oral: (HVCA\-
oral
oralSFt
ora/SF „
inhalation: (HV.
CA
inhalation
inhalation SF{
inhalation SF_,,
where:
oral SFt
oralSFmean
T-fV
•" ' CAinhalation
inhalation SFi
inhalation SF'
equals the cancer oral hazard value for chemical /' (unitless);
equals the cancer oral slope factor for chemical /' (mg/kg-day);
equals the geometric mean cancer slope factor of all available slope
factors (0.71 mg/kg-day);
equals the cancer inhalation hazard value for chemical / (unitless);
equals the cancer inhalation slope factor for chemical /' (mg/kg-day)"1; and
equals the geometric mean cancer inhalation slope factor of all available
inhalation slope factors (1.70 mg/kg-day)"1.
The oral and inhalation slope factor mean values are the geometric means of a set of chemical
data presented in Appendix K, Table K-10.
The noncarcinogen HV is based on either no-observed-adverse-effect levels (NOAELs)
or lowest-observed-adverse-effect levels (LOAELs). The noncarcinogen HV is the greater of the
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\l(oral NOAEL)
oral: (HV '
1 l/(oralNOAELmean)
inhalation and oral HV:
\l(inhal NOAEL)
inhalation: (HVNC ). =
\l(inhalNOAELJ
where:
HVNCoral equals the noncarcinogen oral hazard value for chemical /' (unitless);
oralNOAEL i equals the oral NOAEL for chemical /' (mg/kg-day);
oralNOAEL mean equals the geometric mean oral NOAEL of all available oral NOAELs
(11. 88 mg/kg-day);
HVNC inhaiation equals the noncarcinogen inhalation hazard value for chemical /' (unitless);
inhalNOAEL t equals the inhalation NOAEL for chemical /' (mg/m3); and
inhalNOAEL mean equals the geometric mean inhalation NOAEL of all available inhalation
NOAELs (68.67 mg/kg-day).
The oral and inhalation NOAEL mean values are the geometric means of a set of chemical data
presented in Appendix K, Table K-8. If LOAEL data are available instead of NOAEL data, the
LOAEL divided by 10 is used to substitute for the NOAEL. The most sensitive endpoint is used
if there are multiple data for one chemical.
The sum of the carcinogen and noncarcinogen HVs for a particular chemical is multiplied
by the applicable inventory input to calculate the impact score:
), = f(H
CA
where:
ISCHO equals the impact score for chronic occupational health effects for chemical /'
(tox-kg) per functional unit;
HVCA equals the hazard value for carcinogenicity for chemical /';
HVNC equals the hazard value for chronic noncancer effects for chemical /'; and
AmtTCinput equals the amount of toxic inventory input (kg) per functional unit for chemical /'.
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Chronic public health effects
For chronic public health effects, the impact score represents a surrogate for potential
health effects to residents living near a facility, including cancer, from long-term repeated
exposure to toxic or carcinogenic agents. Impact scores are based on the identity and amount of
toxic chemical outputs with dispositions to air and water.1 As stated above, inventory items do
not truly represent long-term exposure; instead, impacts are relative toxicity weightings of the
inventory.
The scores for impacts to the public differ from the occupational impacts in that
inventory outputs are used as opposed to inventory inputs. Note that this basic screening level
scoring does not incorporate the fate and transport of the chemicals. The chronic public health
effects impact score is calculated as follows:
where:
ISCHP equals the impact score for chronic human health effects to the public for
chemical /' (tox-kg) per functional unit; and
AmtTCoutput equals the amount of toxic inventory output of chemical /' to air and water (kg) per
functional unit.
Aesthetic impacts (odor)
This refers to impacts that detract from the quality of the local environment from a
human perspective. Characterization in this project is based on odor. Impact scores are based on
the identity and amount of odor-causing chemicals (Heijungs et a/., 1992; EPA 1992), released
to the air and their odor threshold value (OTV) (Heijungs et a/., 1992) (Appendix K, Table K-7).
This approach does not score chemicals as is done for toxic chemicals. The OTV is specific to a
chemical, but does not use an equivalency factor that is based on a reference chemical or a
hazard value based on a mean OTV. In this case, the OTV is a concentration which, when
divided into the mass output of a chemical, results in an impact score in units of volume of
malodorous air:
(ISAS), = (Amtoc/OTV),
where:
ISAS equals the aesthetics impact score for chemical /' (m3 malodorous air) per
functional unit;
Amtoc equals the amount of odor-causing output for chemical / released to air (mg) per
functional unit; and
OTV equals the odor threshold value for chemical /' (mg/m3) (Appendix K, Table K-
10).
1 Disposition could be to groundwater. For example, a landfill model could have releases that go to
groundwater.
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Note that this impact assessment methodology determines the volume of malodorous air created
if there is no dilution. In reality, many of the air releases reported in the LCI may occur at
concentrations below the chemical's odor threshold.
3.1.2.13 Ecotoxicity
Ecotoxicity refers to effects of chemical outputs on nonhuman living organisms. Impact
categories include ecotoxicity impacts to aquatic and terrestrial ecosystems.
Aquatic toxicity
Toxicity measures for fish are used to represent potential adverse effects to organisms
living in the aquatic environment from exposure to a toxic chemical. Impact scores are based on
the identity and amount of toxic chemicals as outputs to surface water. Impact characterization
is based on CHEMS-1 acute and chronic hazard values for fish (Swanson etal., 1997) combined
with the inventory amount. Both acute and chronic impacts are combined into the aquatic
toxicity term. The hazard values (HVs) for acute and chronic toxicity are based on LC50 and
NOAEL toxicity data, respectively, mostly from toxicity tests in fathead minnows (Pimephales
promelas) (Swanson et a/., 1997). The acute fish HV is calculated by:
\ =
'i
FA
where:
HVPA equals the hazard value for acute fish toxicity for chemical /' (unitless);
LC50i equals the lethal concentration to 50% of the exposed fish population for
chemical /'; and
LC50mean equals the geometric mean LC50 of available fish LC50 values in Appendix K,
TableK-8(23.45mg/L).
The chronic fish HV is calculated by:
l/NOAEL.
(HVFC\ =
WOAELmean
where:
HVPC equals the hazard value for chronic fish toxicity for chemical /';
NOAELt equals the no observed adverse affect level for fish for chemical /'; and
NOAELmean equals the geometric mean NOAEL of available fish NOAEL values in
Appendix K, Table K-7 (3.90 mg/L).
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The aquatic toxicity impact score is calculated as follows:
(ISAQ), = f(HVFA+HVpc)xAmtjCou,patiVateJi
where:
ISAQ equals the impact score for aquatic ecotoxicity for chemical /' (tox-kg) per
functional unit; and
AmtTCoutput^ater equals the toxic inventory output amount of chemical / to water (kg) per
functional unit.
Terrestrial toxicity
Toxicity measures for mammals (primarily rodents) are used to represent potential
adverse effects to organisms living in the terrestrial environment from exposure to a toxic
chemical. Impact scores are based on the identity and amount of toxic chemicals as outputs to
air and surface water. Impact characterization is based on chronic toxicity hazard values
combined with the inventory amount. The terrestrial toxicity impact score is based on the same
noncancer chronic data used for human health because underlying data are from the same
mammal studies (see Section 2. 1.2.12 for the HVNC term). The cancer hazard value was not
included in the terrestrial impact score as it is based on ranking for potential human
carcinogenicity. The terrestrial toxicity impact score is as follows:
(ISTER), = (HVNC xAmtTCoutpJ,
where:
ISTER equals the impact score for terrestrial toxicity for chemical /' (tox-kg) per
functional unit; and
AmtTCoutput equals the toxic inventory output amount of chemical / (kg) per functional unit.
3 . 1 .2. 14 Summary of impact score equations
Table 3-4 summarizes the impact categories, associated impact score equations, and the
input or output data required for calculating natural resource impacts. Each of these
characterization equations are loading estimates.
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Table 3-4. Summary of natural resources impact scoring
Impact Category
Use of renewable
resources
Use/depletion of
nonrenewable
materials
Energy use, general
energy consumption
Solid waste landfill
use
Hazardous waste
landfill use
Radioactive waste
landfill use
Impact Score Approach
18^= AmtRRxa-RC)
18^= AmtNERxCl-RC)
ISE = AmtE or (AmtF x H/D)
!SSwL =Amtsw/D
ISnwL =AmtHW/D
ISRWL = AmtRW / D
Data Required from Inventory
(per functional unit)
Inputs
Material mass (kg)
(e.g., water)
Material mass (kg)
Energy (MJ)
(electricity, fuel)
none
none
none
Outputs
none
none
none
solid waste mass (kg) and
density (i.e., volume, m3)
hazardous waste mass (kg)
and density (i.e., volume,
m3)
radioactive waste mass (kg)
and density (i.e., volume,
m3)
Abbreviations: RC = recycled content; H = heat value of fuel /'; D = density of fuel /'.
The term abiotic ecosystem refers to the nonliving environment that supports living
systems. Table 3-5 presents the impact categories, impact score equations, and inventory data
requirements for abiotic environmental impacts to atmospheric resources.
Table 3-5. Summary of atmospheric resource impact scoring
Impact Category
Global warming
Stratospheric ozone
depletion
Photochemical smog
Acidification
Air quality (particulate
matter)
Impact Score Approach
I^GW ~~ ErGWp x AmtGG
l^co ~~ -k-Tcop x AmtQDC
I^POCP "E-bpocp x Amtpoc
!SAP = EFAp x AmtAC
I^PM ~~ AmtPM
Data Required from Inventory
(per functional unit)
Inputs
none
none
none
none
none
Outputs
amount of each greenhouse gas
chemical released to air
amount of each ozone depleting
chemical released to air
amount of each smog -creating
chemical released to air
amount of each acidification
chemical released to air
amount of particulates: PM10or
TSP released to air a
a Assumes PM10 and TSP are equal; however, using TSP will overestimate PM10.
Table 3-6 presents the impact categories, impact score equations, and required inventory
data for abiotic environmental impacts to water resources.
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Table 3-6. Summary of water resource impact scoring
Impact Category
Water eutrophication
Water quality (BOD)
Water quality (TSS)
Impact Score Approach
l^EUTR ~~ ErEP X AmtEC
!SBOD ~~ AmtBOD
I^TSS ~~ AmtTSS
Data Required from Inventory
(per functional unit)
Inputs
none
none
none
Outputs
amount of each eutrophication chemical
released to water
amount of BOD in each wastewater
stream released to surface water
amount of suspended solids (TSS) in
each wastewater stream released to
surface water
Table 3-7 summarizes the human health and ecotoxicity impact scoring approaches. The
impact categories, impact score equations, the type of inventory data, and the chemical
properties required to calculate impact scores are presented. The human health effects and
ecotoxicity impact scores are based on the scoring of inherent properties approach to
characterization.
Table 3-7. Summary of human health and ecotoxicity impact scoring
Impact
Category
Chronic human
health effects -
occupational
Chronic human
health effects -
public
Aesthetic
impacts (odor)
Aquatic toxicity
Terrestrial
toxicity
Impact Score Equations
ISCHO = (HVCA + HVNC)x
AmtTCmput
ISCHP = (HVCA + HVNC)x
AmtTCoutput
ISAS = Amtoc/OTV
ISAQ =(HVFA + HVFC)x
AmtjQOUtpUt)Water
!STER ~~ "• *NC x AmtTCoutput
Data Required from Inventory
(per functional unit)
Inputs
mass of each
primary and
ancillary toxic
chemical
none
none
none
none
Outputs
none
mass of each toxic
chemical released to
air and surface water
mass of odorous
chemicals released to
air
mass of each toxic
chemical released to
surface water
mass of each toxic
chemical
released to air or
surface water
Chemical
Properties Data
Required
WOE or SF
and/or mammal
NOAEL or
LOAEL
WOE or SF
and/or mammal
NOAEL or
LOAEL
human odor
threshold values
fish LC50 and/or
fish NOAEL
mammal
NOAEL
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3.1 METHODOLOGY
3.1.2.15 Aggregation of impact scores
Individual impact scores are calculated for inventory items for a certain impact category
and can be aggregated by inventory item (e.g., a certain chemical), process, life-cycle stage, or
entire product profile. For example, global warming impacts can be calculated for one inventory
item (e.g., CO2 releases), for one process that could include contributions from several inventory
items (e.g., electricity generation), for a life-cycle stage that may consist of several process steps
(e.g., product manufacturing), or for an entire profile (e.g., a CRT desktop monitor over its life).
The following example illustrates how impacts are calculated. If two toxic chemicals
[e.g., toluene and benzo(a)pyrene] are included in a waterborne release to surface water from
Process A, impact scores would be calculated for the following impact categories (based on the
classification shown in Table 3-1):
• Chronic public health effects;
• Aquatic toxicity; and
• Terrestrial toxicity.
Despite the output types being waterborne releases, the water eutrophication and water
quality impact categories are not applicable here because the chemical properties criteria in
Table 3-1 are not met. That is, these chemicals do not contain N or P and are not themselves
wastewater streams.
Using chronic public health effects as an example, impact scores are then calculated for
each chemical as follows:
->CHP:toluene
CHP :benzo(a)pyrene
(HVCA:toluene + HVNC:toluene) x AmtTCoutput:toluene
ne + HVNC:benz0(a)pyrene) x AmtTCoutput:benz0(a)pyr,
Table 3-8 presents toxicity data for the example chemicals from Appendix K, Table K-
Using benzo(a)pyrene as an example, the hazard values are calculated as follows:
Table 3-8. Toxicity data used in example calculations
Chemical
Toluene
Benzo(a)pyrene
Cancer
Weight of
evidence
D,3
B2, 2A
Slope factor (SF)
(mg/kg-day)1
none
3.P
7.3C
Chronic noncancer effects
Oral
(mg/kg-day)
100b
no data
Inhalation
(mg/m3)
411. lb
no data
a inhalation SF
bNOAEL
c oral SF
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3.1 METHODOLOGY
Cancer effects:
oral: (HVC
C
oralSF.
HV,
CAoral:benzo(a)pyrene
7.3 (ing/kg-day)"1 - 0.71 (mg/kg-day)'1
10.3
inhalation: (HVCA ). = -
inhalation SF,
lnh inhalation
HV
n v CAinhalation:benzo(a)pyrene
= 3.1 (mg/kg-day)"1 -M.7 (mg/kg-day)"1
= 1.82
Thus, the cancer HV is 10.3, the greater of the two values.
Noncancer effects:
Since no data are available for noncancer effects, a default HV of one is assigned,
representative of mean toxicity.
Total HV:
Thus the total hazard value for benzo(a)pyrene is given by:
HV
^ benzo(a)pyreni
:o(a)pyrene
= HVCA + HVNC
= 10.3 + 1
= 11.3
Similarly, the HV for toluene is found to be 0.12. Given the following hypothetical output
amounts:
Ami
TC-O:TOLUENE
= 1.3 kg of toluene per functional unit
AmtTC.0.BENZO(A)pYRENE =0.1 kg of benzo(a)pyrene per functional unit
the resulting impact scores are as follows:
ISCHp-w:TOLUENE =0.12x1.3 =0.16 tox-kg of toluene per functional unit
ISCHp-w:BENzo(A)FYRENE = 11-3x0.1 = 1.13 tox-kg of benzo(a)pyrene per functional unit
3-24
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3.1 METHODOLOGY
If these were the only outputs from Process A relevant to chronic public health effects, the total
impact score for this impact category for Process A would be:
TS = TS + TS
10CHP:PROCESS_A 1OCHP-W:TOLUENE 1OCHP-W:BENZO(A)PYRENE
= 0.16+1.13
= 1.29 tox-kg per functional unit for Process A.
If the product system Y contained three processes altogether (Processes A, B, and C), and the
impact scores for Process B and C were 2.5 and 3.0, respectively, impact scores would be added
together to yield a total impact score for the product system relevant to chronic public health
effects:
TS = TS + TS + TS
10CHP:PROFILE_Y 1OCHP:PROCESS_A 1OCHP:PROCESS_B 1OCHP:PROCESS_C
= 1.29+ 2.5+"3.0
= 6.8 tox-kg per functional unit for Profile Y.
An environmental profile would then be the sum of all the processes within that profile for each
impact category.
3.1.3 Data Sources and Data Quality
Data that are used to calculate impacts are from: (1) equivalency factors or parameters
used to identify hazard values; and (2) LCI items. Equivalency factors and data used to develop
hazard values, which have been presented in this methodology, include GWP, ODP, POCP, AP,
EP, WOE, SF, mammalian LOAEL/NOAEL, OTV, fish LC50, and fish NOAEL. Published lists
of the chemical-specific parameter values exist for GWP, ODP, POCP, AP, EP and OTV (see
Appendix K). The other parameters may exist for a large number of chemicals and several data
sources must be searched to identify the appropriate parameter values. Priority is given to peer-
reviewed databases (e.g., HEAST, IRIS, HSDB), then other databases (e.g., RTECS), other
studies or literature, and finally estimation methods [e.g., structure-activity relationships (SARs)
or quantitative structure-activity relationships (QSARs)]. The specific toxicity data that are used
in the CDP are presented in Appendix K, Table K-8. The sources of each parameter presented in
this report, and the basis for their values, are presented in Table 3-9. Data quality is affected by
the type of data source (e.g., primary versus secondary data), the currency of the data, and the
accuracy and precision of the data, and will depend on the source. The sources and quality of the
LCI data used to calculate impact scores were discussed in Chapter 2. Data sources and data
quality for each impact category are discussed further in Section 3.3, Baseline LCIA Results.
3.1.4 Limitations and Uncertainties
This section summarizes some of the limitations and uncertainties in LCIA methodology,
in general. Specific limitations and uncertainties in each impact category are discussed in
Section 3.3 with the baseline LCIA results.
The purpose of an LCIA is to evaluate the relative potential impacts of a product system
for various impact categories. There is no intent to measure the actual impacts or provide spatial
or temporal relationships linking the inventory to specific impacts. The LCIA is intended to
3^25
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3.1 METHODOLOGY
provide a screening-level evaluation of impacts. More detailed characterization of exposure and
toxicity has been conducted on selected materials for the CDP in Chapter 4.
Table 3-9. Data sources for equivalency factors and hazard values
Parameter
Global warming potential (GWP)
Ozone depletion potential (ODP)
Photochemical oxidant creation
potential (POCP)
Acidification potential (AP)
Nutrient enrichment/eutrophication
potential (EP)
Weight-of-evidence (WOE)
Slope factor (SF)
Mammalian: Lowest observed
adverse effect level / No observed
adverse effect level
(LOAEL/NOAEL)
Fish lethal concentration to 50% of
the exposed population (LC50)
FishNOAEL
Odor threshold value (OTV)
Basis of Parameter Values
atmospheric lifetimes and radiative forcing
compared to CO2
the change in the ozone column in the
equilibrium state of a substance compared to
CFC-11
simulated trajectories of ozone production with
and without VOCs present compared to ethene
number of hydrogen ions that can theoretically
be formed per mass unit of the pollutant being
released compared to SO2
ratio of N to P in the average composition of
algae (C10(iH263O110N1(iP) compared to
phosphate (PO43")
classification of carcinogenicity by EPA or
IARC based on human and/or animal toxicity
data
measure of an individual's excess risk or
increased likelihood of developing cancer if
exposed to a chemical, based on dose-response
data
mammalian (primarily rodent) toxicity studies
fish (primarily fathead minnow) toxicity
studies
fish (primarily fathead minnow) toxicity
studies
measured odor thresholds in humans
Source
Houghtone/a/., 1996
Heijungse/a/., 1992;
CAAA, 1990
Heijungse/a/., 1992
Heijungsrfa/., 1992;
Hauschild and Wenzel,
1997
Heijungsrfa/., 1992;
Lindforse/a/., 1995
EPA, 1999; IARC, 1998
IRIS and HEAST as cited
in Risk Assessment
Information System
(RAIS) online database
IRIS, HEAST and various
literature sources provided
by EPA contractor
Various literature sources
and Ecotox database
Literature sources and
Ecotox database
EPA, 1992
In addition to lacking temporal or spatial relationships and providing only relative
impacts, LCA is also limited by the availability and quality of the inventory data. Data
collection can be very time consuming and expensive. Confidentiality issues may also inhibit
the availability of primary data.
Uncertainties are inherent in each parameter described in Table 3-9 and the reader is
referred to each source for more information on associated uncertainties. For example, toxicity
data require extrapolations from animals to humans and from high to low doses (for chronic
effects) and can have a high degree of uncertainty.
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3.1 METHODOLOGY
Uncertainties also are inherent in chemical ranking and scoring systems, such as the
scoring of inherent properties approach used for human health and ecotoxicity effects. In
particular, systems that do not consider the fate and transport of chemicals in the environment
can contribute to misclassifications of chemicals with respect to risk. Also, uncertainty is
introduced where it was assumed that all chronic endpoints are equivalent, which is likely not the
case. In addition, when LOAELs were not available but NOAELs were, a factor often was
applied to the NOAEL to estimate the LOAEL, introducing uncertainty. The human health and
ecotoxicity impact characterization methods presented here are screening tools that cannot
substitute for more detailed risk characterization methods. However, it should be noted that in
LCA, chemical toxicity is often not considered at all. This methodology is an attempt to
consider chemical toxicity where it is often ignored.
Uncertainty in the inventory data depends on the responses to the data collection
questionnaires and other limitations identified during inventory data collection. These
uncertainties are carried into impact assessment. In this LCA, there was uncertainty in the
inventory data, which included but was not limited to the following:
• missing individual inventory items,
• missing processes or sets of data,
• measurement uncertainty,
• estimation uncertainty,
• allocation uncertainty/working with aggregated data, and
• unspeciated chemical data.
The goal definition and scoping process helped reduce the uncertainty from missing data,
although it is certain that some (missing data) still exist. As far as possible, the remaining
uncertainties were reduced primarily through quality assurance/quality control measures (e.g.,
performing systematic double-checks of all calculations on manipulated data). The limitations
and uncertainties in the inventory data were discussed further in Chapter 2.
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3.2 DATA MANAGEMENT AND ANALYSIS SOFTWARE
3.2 DATA MANAGEMENT AND ANALYSIS SOFTWARE
The inventory and chemical characteristics data for the CDP are stored in a database
within a software package developed by UT, using the Microsoft Visual FoxPro application
programming language, under a cooperative agreement with the EPA Office of Research and
Development. The software package calculates impact scores based on the stored inventory and
chemical data and on the appropriate formulas for each impact category, as presented in
Section 3.1.
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3.3 BASELINE LCIA RESULTS
3.3 BASELINE LCIA RESULTS
This section presents the baseline LCIA results calculated using the impact assessment
methodology presented in Section 3.1. As noted in the section on baseline LCI results (Section
2.7.1), the baseline scenario meets the following conditions:
• uses the effective life use stage scenario (e.g., use stage calculations are based on the
actual amount of time a monitor is used by one or multiple users before it reaches its final
disposition);
• uses the average value of all the energy inputs from the primary data for glass
manufacturing;
• removes two outliers from the primary data for energy inputs during LCD panel/module
manufacturing and then uses the average of the remaining energy inputs;
• excludes transportation in the manufacturing stage, but includes any transportation
embedded in upstream data sets;
• includes the manufacturing processes of materials used as fuels (e.g., natural gas, fuel oil)
in the manufacturing stage instead of in the upstream, materials processing stage. In
cases where materials normally considered to be fuels are used as ancillary materials,
their manufacturing processes are included with other upstream processes; and
• assumes LCD glass manufacturing processes use the same amounts of energy as CRT
glass manufacturing per kilogram of glass produced.
Section 3.3.1 summarizes the baseline life cycle impact category indicators for both the
CRT and LCD. Sections 3.3.2 through 3.3.14 present a breakdown of the impact category
indicators by life-cycle stage, list the materials that contribute 99% of the total for both monitor
types, and discuss limitations and uncertainties in each impact category. Each of the tables in
this report shows the top contributors to the impacts because the complete tables, which are
provided in Appendix J, are often lengthy. Section 3.3.15 summarizes the top contributors to
each impact category, and Appendix M presents complete LCIA results.
3.3.1 Summary of Baseline LCIA Results
Table 3-10 presents the baseline CRT and LCD LCIA indicator results for each impact
category, calculated using the impact assessment methodology presented in Section 3.1. The
indicator results presented in the table are the result of the characterization step of LCIA
methodology where LCI results are converted to common units and aggregated within an impact
category. Note that the impact category indicator results are in a number of different units and
therefore can not be summed or compared across impact categories. Note also that the CDP
LCIA methodology does not perform the optional LCIA steps of normalization (calculating the
magnitude of category indicator results relative to a reference value), grouping (sorting and
possibly ranking of indicators), or weighting (converting and possibly aggregating indicator
results across impact categories). Ranking and weighting, in particular, are subjective steps that
depend on the values of the different individuals, organizations, or societies performing the
analysis. Since the CDP involves a variety of stakeholders from different geographic regions
and with different values, these more subjective steps were intentionally excluded from the CDP
LCIA methodology.
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3.3 BASELINE LCIA RESULTS
Table 3-10. Baseline life-cycle impact category indicators3
Impact category
Renewable resource use
Nonrenewable resource use
Energy use
Solid waste landfill use
Hazardous waste landfill use
Radioactive waste landfill use
Global warming
Ozone depletion
Photochemical smog
Acidification
Air particulates
Water eutrophication
Water quality, BOD
Water quality, TSS
Radioactivity
Chronic health effects, occupational
Chronic health effects, public
Aesthetics (odor)
Aquatic toxicity
Terrestrial toxicity
Units per monitor
kg
kg
MJ
m3
m3
m3
kg-CO2 equivalents
kg-CFC-11 equivalents
kg-ethene equivalents
kg-SO2 equivalents
kg
kg-phosphate equivalents
kg
kg
Bq
tox-kg
tox-kg
m3
tox-kg
tox-kg
CRT
1.31E+04
6.68E+02
2.08E+04
1.67E-01
1.68E-02
1.81E-04
6.95E+02
2.05E-05b>c
1.71E-01
5.25E+00
3.01E-01
4.82E-02
1.95E-01
8.74E-01
3.85E+07d
9.34E+02
1.98E+03
7.58E+06
2.25E-01
1.97E+03
LCD
2.80E+03
3.64E+02
2.84E+03
5.43E-02
3.61E-03
9.22E-05
5.93E+02
1.37E-05b
1.41E-01
2.96E+00
1.15E-01
4.96E-02
2.83E-02
6.15E-02
1.22E+07d
6.96E+02
9.02E+02
5.04E+06
5.19E-HM)
8.94E+02
a Bold indicates the larger value within an impact category when comparing the CRT and LCD.
b Several of the substances included in this category were phased out of production by January 1, 1996. Excluding
phased out substances decreases the CRT ozone depletion indicator to 1.09E-05 kg CFC-11 equivalents per monitor
and the LCD ozone depletion indicator to 1.18E-05 kg CFC-11 equivalents per monitor. These ozone depletion
indicators are probably more representative of the CDP temporal boundaries and current operating practices. See
Section 3.3.6 for details.
c Although the CRT indicator appears larger than the LCD indicator, uncertainties in the inventory make it difficult
to determine which monitor has the greater value. Therefore, this value is not shown in bold.
Radioactivity impacts are being driven by radioactive releases from nuclear fuel reprocessing in France, which are
included in the electricity data in some of the upstream, materials processing data sets. See Section 3.3.12 for details.
As shown in the table, under the baseline conditions the CRT indicators are greater than
the LCD indicators in the following categories: renewable resource use, nonrenewable resource
use, energy use, solid waste landfill use, hazardous waste landfill use, radioactive waste landfill
use, global warming, photochemical smog, acidification, air particulates, biological oxygen
demand (BOD), total suspended solids (TSS), radioactivity, chronic public health effects, chronic
occupational health effects, aesthetics, and terrestrial toxicity. The LCD indicators are greater
than the CRT indicators in the following categories: water eutrophication and aquatic toxicity. In
addition, as noted in Table 3-10, the CRT ozone depletion indicator is greater than that of the
LCD when phased out substances are left in the CRT and LCD inventories. However, if phased
3-30
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3.3 BASELINE LCIA RESULTS
out substances are removed from the CRT and LCD inventories, the LCD ozone depletion
indicator would exceed that of the CRT.
A number of the impact results for both monitor types, and for the CRT in particular, are
being driven by a few data points with relatively high uncertainty. Therefore, sensitivity
analyses of the baseline results are presented in Section 3.4.
3.3.2 Renewable and Nonrenewable Resource Use
3.3.2.1 Renewable resource use
Figure 3-2 presents the CRT and LCD impact category indicators for renewable resource
use by life-cycle stage, based on the impact assessment methodology presented in Section
3.1.2.1. Tables M-l and M-2 in Appendix M present complete renewable resource results for
the CRT and LCD, respectively. A renewable resource is one that is being replenished at a rate
greater than or equal to its rate of depletion. Note that several of the resources listed in the
Appendix and in the tables that follow are not renewable or can not be replenished, per se, but
are considered renewable since they can be restored or are present in nearly infinite, non-
depletable amounts. For example, water is typically considered a renewable resource since it can
be restored to potable quality and is therefore being "replenished" at a rate greater than or equal
to its rate of depletion. However, current trends toward shortages of potable water suggest that
water might be more appropriately classified as a nonrenewable resource.
^ 10,000 -
'E
3
c 6,000 -
o
o
c
;2 2,000 -
"3)
j*:
-2,000 -
Renewable resource use
n Upstream
• Mfg
~~
556
[ ~~|
111,500 nUse
DEOL
2,130
1,140 , ,
1 -17 264 426 -16
CRT Monitor type LCD
Figure 3-2. Renewable resource use impacts by life-cycle stage
3-31
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3.3 BASELINE LCIA RESULTS
As shown in Figure 3-2, the baseline life-cycle impact category indicator for renewable
resource use is 13,100 kg per monitor for the CRT and 2,800 kg per monitor for the LCD. Both
the CRT and LCD renewable resource use results are dominated by the manufacturing life-cycle
stage, with manufacturing accounting for 87% and 76% of the CRT and LCD totals,
respectively.
Table 3-11 presents the life-cycle inventory items that contribute to the top 99% of the
CRT renewable resource use total. It also lists the LCI data type (primary, secondary, or
model/secondary). As shown in Table 3-11, water used in the production of LPG clearly
dominates the CRT renewable resource use impact score. LPG is primarily used as an energy
source in CRT glass manufacturing, indicating that the glass/frit process group is ultimately the
greatest contributor to the CRT renewable resource use impact score. Other significant
contributors include water used to produce electricity in the United States during the use of the
monitor, water used in CRT tube manufacturing, and water used in the production of steel. The
LCI data for LPG production and steel manufacturing are from secondary sources, while the LCI
data for the U.S. electric grid are based on the model developed by the CDP for the amount of
electricity consumed by a CRT during use combined with data from secondary sources on the
inputs and outputs from U.S. power plants. CRT tube manufacturing LCI data are primary data
collected by the CDP.
Table 3-11. Top 99% of the CRT renewable resource use impact score
Life-cycle stage
Manufacturing
Use
Manufacturing
Materials processing
Manufacturing
Manufacturing
Process group
LPG production
U.S. electric grid
CRT tube manufacturing
Steel production, cold-rolled,
semi-finished
Japanese electric grid
PWB manufacturing
Material
Water
Water
Water
Water
Water
Water
LCI data
type
Secondary
Model/secondary
Primary
Secondary
Model/secondary
Primary
Contribution to
impact score*
79%
8.7%
6.2%
3.6%
0.34%
0.32%
* Column may not add to 99% due to rounding.
Table 3-12 presents the inventory items contributing to the top 99% of the LCD
renewable resource use total and the LCI data types (primary, secondary, or model/secondary).
As shown in the table, water used in LCD module/monitor manufacturing is the greatest
contributor to the LCD renewable resource use impact score. Other significant contributors
include water used in the production of LPG, water used by the U.S. electric grid during the use
life-cycle stage, and water used in steel production. It is LCD glass manufacturing that
consumes the LPG responsible for the high LCD renewable resource use score. The LCI data for
LCD module manufacturing are primary data collected by the CDP. LPG production and steel
manufacturing are from secondary sources, while the LCI data for the U.S electric grid are based
on the model developed by the CDP for the amount of electricity consumed by an LCD during
the use stage combined with data from secondary sources.
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3.3 BASELINE LCIA RESULTS
Table 3-12. Top 99% of the LCD renewable resource use impact score
Life-cycle stage
Manufacturing
Manufacturing
Use
Materials processing
Manufacturing
Manufacturing
Manufacturing
Manufacturing
Process group
LCD module/monitor mfg.
LPG production
U.S. electric grid
Steel production
(cold-rolled, semi-finished)
LCD panel components
Backlight
Japanese electric grid
PWB Manufacturing
Material
Water
Water
Water
Water
Water
Water
Water
Water
LCI data
type
Primary
Secondary
Model/secondary
Secondary
Primary
Primary
Model/secondary
Primary
Contribution to
impact score*
38%
18%
15%
8.2%
6.4%
6.8%
5.3%
0.66%
* Column may not add to 99% due to rounding.
3.3.2.2 Nonrenewable resource use
Figure 3-3 presents the CRT and LCD impact category indicators for nonrenewable
resource use by life-cycle stage, based on the impact assessment methodology presented in
Section 3.1.2.1. Tables M-3 and M-4 in Appendix M present complete nonrenewable resource
results for the CRT and LCD, respectively. The total nonrenewable resource use indicator was
668 kg per monitor for the CRT and 364 kg per monitor for the LCD. As shown in Figure 3-3,
the CRT nonrenewable resource use results are dominated by the manufacturing life-cycle stage,
which contributed 68% of the total. The LCD nonrenewable resource use score is dominated by
the upstream materials processing stages, which contributed 69% of the total.
Nonrenewable resource use
500 n
+. 400 -
'c
- 300 -
TO
O onn
4-*
o
§ 100 -
it
O)
•* 0 -
-100 -
_L
n Upstream
• Mfg
451 DUse
DEOL
250
74
43
-3.5 I I -2.3
CRT Monitor type LCD
Figure 3-3. Nonrenewable resource use impacts by life-cycle
stage
3-33
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3.3 BASELINE LCIA RESULTS
Table 3-13 presents the inventory items contributing to the top 99% of the CRT
nonrenewable resource use impact score. It also lists the LCI data type (primary, secondary, or
model/secondary). Similar to the renewable resource use LCIA results, the LPG production
process, which mainly supports the CRT glass manufacturing process, clearly dominates the
CRT nonrenewable resource use impact score. Petroleum used to make LPG is the non-
renewable resource being consumed by the LPG production process in the greatest amounts,
followed by natural gas, and coal. Note that the LPG actually consumed during CRT glass
manufacturing does not appear in the nonrenewable resource use results. This is because it was
accounted for in the nonrenewable resource use score for the LPG production process when it
was extracted from the ground.
Fuels (coal and natural gas) consumed by the U.S. electric grid during monitor use are
also among the greatest contributors to the CRT nonrenewable resource use impact scores. The
LCI data for LPG production are from secondary sources, while the LCI data for the U.S. electric
grid are based on the model developed by the CDP for the amount of electricity consumed by a
CRT during use combined with data from secondary sources on the inputs and outputs from U.S.
power plants.
Table 3-13. Top 99% of the CRT nonrenewable resource use impact score
Life-cycle stage
Manufacturing
Use
Manufacturing
Use
Manufacturing
Materials processing
Materials processing
Manufacturing
Use
Manufacturing
Manufacturing
Manufacturing
Materials processing
Manufacturing
Materials processing
Manufacturing
Process group
LPG production
U.S. electric grid
LPG production
U.S. electric grid
LPG production
Steel production, cold-
rolled, semi-finished
Steel production, cold-
rolled, semi-finished
Fuel oil #6 production
U.S. electric grid
Natural gas production
U.S. electric grid
Japanese electric grid
Aluminum production
Japanese electric grid
Polycarbonate
production
Japanese electric grid
Material*
Petroleum (in ground)
Coal, average (in ground)
Natural gas (in ground)
Natural gas
Coal, average (in ground)
Iron Ore
Coal, average (in ground)
Petroleum (in ground)
Petroleum (in ground)
Natural gas (in ground)
Coal, average (in ground)
Coal, average (in ground)
Bauxite
Petroleum (in ground)
Natural gas (in ground)
Natural gas
LCI data
type
Secondary
Model/secondary
Secondary
Model/secondary
Secondary
Secondary
Secondary
Secondary
Model/secondary
Secondary
Model/secondary
Model/secondary
Secondary
Model/secondary
Secondary
Model/secondary
Contribution
to impact
score*
56%
27%
6.7%
2.1%
2.0%
0.99%
0.60%
0.58%
0.57%
0.51%
0.43%
0.34%
0.20%
0.19%
0.19%
0.19%
* Column may not add to 99% due to rounding.
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3.3 BASELINE LCIA RESULTS
Table 3-14 presents the inventory items contributing to the top 99% of the LCD non-
renewable resource use impact score. In this case, the impact score is dominated by the natural
gas extracted to produce natural gas in the upstream, materials processing life-cycle stage.
Liquified natural gas (LNG) from this production process is used as an ancillary material in the
LCD module/monitor manufacturing process group, indicating LCD module/monitor
manufacturing is ultimately responsible for this non-renewable resource use. However, only one
of the seven companies that provided data for the LCD module/monitor manufacturing process
group reported this use of LNG. Note that the actual use of LNG in the LCD
module/manufacturing process group does not appear in the nonrenewable resource results.
Similar to the LPG results discussed above for the CRT, this is because it has been accounted for
in the natural gas production process results.
Other primary contributors to this impact score include coal used to produce electricity
for the U.S. electric grid, and petroleum used to produce LPG. The LCI data for all of the
primary contributors to the LCD non-renewable resource use score were either from secondary
sources or CDP models combined with secondary sources.
Table 3-14. Top 99% of the LCD nonrenewable resource use impact score
Life-cycle stage
Materials processing
Use
Manufacturing
Manufacturing
Manufacturing
Use
Manufacturing
Manufacturing
Materials processing
Manufacturing
Materials processing
Materials processing
Use
Process group
Natural gas production
U.S. electric grid
LPG production
Japanese electric grid
Natural gas production
U.S. electric grid
Japanese electric grid
Japanese electric grid
Steel production (cold-
rolled, semi-finished)
LPG production
Steel production (cold-
rolled, semi-finished)
Natural gas production
U.S. electric grid
Material
Natural gas (in ground)
Coal, average (in ground)
Petroleum (in ground)
Coal, average (in ground)
Natural gas (in ground)
Natural gas
Petroleum (in ground)
Natural gas
Iron ore
Natural gas (in ground)
Coal (in ground)
Coal (in ground)
Petroleum (in ground)
LCI data
type
Secondary
Model/secondary
Secondary
Model/secondary
Secondary
Model/secondary
Model/secondary
Model/secondary
Secondary
Secondary
Secondary
Secondary
Model/secondary
Contribution
to impact
score*
65%
18%
4.9%
2.1%
1.5%
1.4%
1.2%
1.2%
0.89%
0.59%
0.54%
0.45%
0.39%
*Column may not add to 99% due to rounding
3.3.2.3 Limitations and uncertainties
The renewable and nonrenewable resource use results presented here are based on the
mass of a material consumed. Depletion of renewable materials, which results from the
extraction of renewable resources faster than they are renewed, may occur but is not specifically
modeled or identified in the renewable resource impact scores. This may be particularly
important for water, which, while considered a renewable resource, is in shorter and shorter
supply as world population grows and more of the world's water resources become degraded.
For the nonrenewable materials use category, depletion of materials results from the extraction
3-35
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3.3 BASELINE LCIA RESULTS
of nonrenewable resources. However, the impact scores do not directly relate consumption rates
to the earth's ability to sustain that consumption.
The CRT and LCD impact scores for renewable resource use, and the CRT impact score
for nonrenewable resources use, are being driven by the fuels consumed during CRT or LCD
glass manufacturing. However, as discussed in Section 2.3.3.3, there is a high degree of
variability in the three sets of CRT glass manufacturing energy data received by the CDP.
Furthermore, as discussed in Section 2.3.3.1, LCD glass manufacturing data were developed
from the CRT data because no companies were willing to supply the LCD data. Therefore, glass
energy use inputs are uncertain for both the CRT and the LCD and were the subject of a
sensitivity analysis, discussed in Section 3.4.
The LCD impact score for nonrenewable resource use is being driven by LNG used as an
ancillary material during LCD module/monitor manufacturing. However, only one LCD
module/monitor manufacturer reported using LNG as an ancillary material, which was
confirmed by CDP researchers in follow-up communications. Given the fact that only one of
seven manufacturers reported the ancillary use of LNG, the LCD nonrenewable resource use
indicator may not be representative of the industry as a whole. If we remove this application of
LNG from the LCD inventory, the LCD nonrenewable resource result is reduced by 66%, from
364 kg per monitor to 125 kg per monitor.
Inventory data for most of the materials contributing 99% of the CRT and LCD impact
scores come from secondary sources, and were not developed specifically for the CDP. The
limitations and uncertainties associated with secondary data sources are summarized in Section
2.2.2. Table 3-15 looks more closely at the LPG and natural gas production geographic and
temporal boundaries. These are the production processes that are driving a large part of the CRT
and LCD resources use indicators. As shown in the table, most of the LPG and natural gas
production data are for the United States, although the LPG data set includes some data from
other countries. Both data sets rely on several different sources and have different temporal
boundaries. In particular, LPG production data are less recent, and may not accurately reflect
current production practices. All of these factors create some inconsistencies among the data
sets and reduce the data quality when used for the purposes of the CDP. However, this is a
common difficulty with LCA, which often uses data from secondary sources to avoid the
tremendous amount of time and resources required to collect all the needed data.
Table 3-15. LPG and natural gas production geographic and temporal boundaries
Production Process
LPG production
Natural gas production
Location
Mainly U.S., but includes some
other countries
U.S.
Source
Seven sources cited
Six sources cited
Year
1983 to 1993
1987 to 1998
3-36
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3.3 BASELINE LCIA RESULTS
3.3.3 Energy Use
Figure 3-4 presents the CRT and LCD impact results for energy use by life-cycle stage,
based on the impact assessment methodology presented in Section 3.1.2.2. Tables M-5 and M-6
in Appendix M list complete energy use results for the CRT and LCD, respectively. The total
indicator for this impact category was 20,800 MJ per monitor for the CRT, and 2,840 MJ per
monitor for the LCD.
CRTs generally are assumed to have greater life-cycle energy use impacts than the LCDs
due to the high energy requirements in the use stage. This is borne out by the results in
Figure 3-4, which show that CRT energy consumption during use is roughly 2.7 times that of the
LCD. However, contrary to expectations, CRT energy use impacts are driven by the
manufacturing life-cycle stage, which contributes about 88% of the total score. The use stage,
which was expected to be responsible for a large amount of energy consumption impacts, only
contributes about 11% of the total score. LCD energy consumption impacts are also largest in
the manufacturing life-cycle stage which accounts for almost 51% of the impacts in this
category. Both the use and upstream (materials processing) life-cycle stages are also significant
contributors to LCD life-cycle energy use, accounting for 30 and 22%, respectively. Note that
the sum of the upstream, manufacturing, and use life-cycle stages is greater than 100% due to an
energy credit for incineration with energy recovery at the end of a monitor's useful life.
20,000 n
*J
§ 15,000
c 10,000
o
o 5,000
*: n
==> °
-5,000
366
Fnp rnv
cneiyy
n Upstream
• Mfg
18,300 DUse
rjEOL
2'29° _128 633 L440 853 _84
CRT LCD
Monitor type
Figure 3-4. Energy impacts by life-cycle stage
3.3.3.1 Major contributors to the CRT energy use results
Table 3-16 presents the life-cycle inventory items contributing to the top 99% of the CRT
energy use results and the LCI data type (primary, secondary, or model/secondary). As shown in
the table, LPG used in the glass/frit process group, primarily from CRT glass manufacturing,
clearly dominates the CRT energy use result, followed by electricity consumed during use of a
CRT monitor, and natural gas, petroleum, and coal consumed during LPG production. Since
LPG is used primarily as an energy source during CRT glass manufacturing, most of the sum of
the glass/frit manufacturing and LPG production energy use impacts—roughly 87% of the CRT
life-cycle energy use impacts—can be attributed to the CRT glass manufacturing process.
3-37
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3.3 BASELINE LCIA RESULTS
Table 3-16. Top 99% of the CRT energy use impact score
Life-cycle stage
Manufacturing
Use
Manufacturing
Manufacturing
Manufacturing
Manufacturing
Manufacturing
Manufacturing
Manufacturing
Manufacturing
Materials processing
Manufacturing
Manufacturing
Manufacturing
Process group
Glass/frit manufacturing
CRT monitor use
LPG production
LPG production
LPG production
CRT tube manufacturing
Glass/frit manufacturing
Glass/frit manufacturing
Glass/frit manufacturing
CRT tube manufacturing
Polycarbonate production
LPG production
CRT tube manufacturing
Glass/frit manufacturing
Material
Liquified petroleum gas
Electricity
Natural gas (in ground)
Petroleum (in ground)
Coal, average (in ground)
Fuel oil #6
Natural gas
Fuel oil # 2
Electricity
Natural gas
Natural gas (in ground)
Uranium (U, ore)
Electricity
Electricity
LCI data
type
Primary
Model/secondary
Secondary
Secondary
Secondary
Primary
Primary
Primary
Primary
Primary
Secondary
Secondary
Primary
Primary
Contribution
to impact
score*
72%
11%
10%
2.0%
1.4%
0.72%
0.26%
0.24%
0.23%
0.18%
0.16%
0.16%
0.15%
0.13%
*Column may not add to 99% due to rounding.
3.3.3.2 Major contributors to the LCD energy use results
Table 3-17 lists the inventory items contributing to the top 99% of the LCD life-cycle
energy use results. Electricity consumed during use of the LCD monitor by the consumer is the
single largest contributor to LCD energy use impacts, closely followed by LPG utilized to
produce LCD glass. Other major contributors include natural gas consumed during natural gas
production, electricity and LNG used as a fuel during LCD monitor/module manufacturing, and
natural gas consumed during LPG production. Note that the LNG used as an ancillary material
in LCD module/monitor manufacturing is not included in the LCD energy use impact
calculations since it is not used as a source of energy. However, natural gas used as an energy
source to produce the LNG is included (the third item listed in the table).
3-38
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3.3 BASELINE LCIA RESULTS
Table 3-17. Top 99% of the LCD energy use impact score
Life-cycle stage
Use
Manufacturing
Materials processing
Manufacturing
Manufacturing
Manufacturing
Manufacturing
Manufacturing
Materials processing
Materials processing
Manufacturing
Manufacturing
Materials processing
Manufacturing
Manufacturing
Materials processing
Materials processing
Materials processing
Materials processing
Manufacturing
Materials processing
Materials processing
Manufacturing
Materials processing
Materials processing
Process group
LCD monitor use
LCD glass manufacturing
Natural gas production
LCD module/monitor mfg.
LCD module/monitor mfg.
LPG production
LCD panel components
LCD module/monitor mfg.
Natural gas production
Natural gas production
LCD module/monitor mfg.
LPG production
Polycarbonate production
LPG production
LCD module/monitor mfg.
PMMA sheet production
PMMA sheet production
Steel production
(cold-rolled, semi-finished)
Steel production
(cold-rolled, semi-finished)
Natural gas production
PMMA sheet production
Steel production
(cold-rolled, semi-finished)
LCD module/monitor mfg.
Styrene-butadiene copolymer
production
Aluminum production
Material
Electricity
Liquified petroleum gas
Natural gas (in ground)
Electricity
Liquified natural gas
Natural gas (in ground)
Electricity
Natural gas
Coal (in ground)
Petroleum (in ground)
Liquified petroleum gas
Petroleum (in ground)
Natural gas (in ground)
Coal (in ground)
Kerosene
Petroleum (in ground)
Natural gas (in ground)
Petroleum (in ground)
Natural gas (in ground)
Natural gas (in ground)
Electricity
Electricity
Fuel oil # 4
Natural gas (in ground)
Coal (in ground)
LCI data
type
Model/
secondary
Primary
Secondary
Primary
Primary
Secondary
Primary
Primary
Secondary
Secondary
Primary
Secondary
Secondary
Secondary
Primary
Secondary
Secondary
Secondary
Secondary
Secondary
Secondary
Secondary
Primary
Secondary
Secondary
Contribution
to impact
score*
30%
25%
14%
8.9%
5.8%
3.4%
1.4%
1.3%
1.3%
0.89%
0.88%
0.69%
0.67%
0.51%
0.46%
0.42%
0.41%
0.36%
0.35%
0.32%
0.32%
0.31%
0.31%
0.29%
0.29%
*Corumn may not add to 99% due to rounding.
3.3.3.3 Limitations and uncertainties
Some of the limitations and uncertainties in the energy use indicators are similar to those
in the renewable and nonrenewable resource use categories. First, as discussed in Section
3.3.1.1, the energy data for both CRT and LCD glass manufacturing are uncertain due to the
variability in the primary glass data received by the CDP from three glass manufacturers. Glass
manufacturing energy data are the subject of a sensitivity analysis in Section 3.4. Second, data
for LPG production and natural gas production, which are among the largest contributors to the
energy use indicators, are from secondary sources and are therefore subject to the limitations and
3-39
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3.3 BASELINE LCIA RESULTS
uncertainties associated with secondary data (see Section 2.2.2 and 3.3.1.1). Not counting the
use stage data, note that about 14% of the CRT energy use impacts shown in Table 3-16, above,
are from secondary sources, compared to about 24% of the LCD energy use impacts
(Table 3-17).
The amount of electricity consumed during use of a monitor was modeled by the CDP
from secondary sources on the amount of electricity consumed during different power modes and
the amount of time a monitor spends in each mode. Data quality for the effective life scenario
(the baseline scenario presented here) is considered to be excellent, based on the source and
quality information detailed in Appendix H and discussed in Sections 2.4.2 and 2.4.3.
3.3.4 Landfill Use
3.3.4.1 Solid waste landfill use
Figure 3-5 presents the CRT and LCD LCIA results for the solid waste landfill use
impact category, based on the impact assessment methodology presented in Section 3.1.2.3.
Tables
M-7 and M-8 in Appendix M present complete results for the CRT and LCD, respectively. Life-
cycle solid waste landfill use was 0.17m3 for the CRT and 0.054 m3 for the LCD. The solid
waste landfill indicators for both monitor types are dominated by waste disposal during the use
stage—which contributes 59% of the total for the CRT and 68% for the LCD—primarily from
wastes generated as a by-product of electricity production. Both monitor types have negative
solid waste impact scores during the end-of-life stage. This is due to an energy credit from
incineration processes, which offsets some of the solid waste impacts from electricity generation.
+J
'1 8.00E-02
"re
o
'"S 3.00E-02
c
s2
fO
-2.00E-02
5.64E
1.23E-02
-02
£
9.91E-02
Jolid waste • Upstream
• Mfg
QUse
DEOL
3.70E-02
1.07E-02
1.10E-02
CRT LCD
Monitor type
Figure 3-5. Solid waste impacts by life-cycle stage
Table 3-18 presents the materials that contribute to the top 99% of the CRT solid waste
landfill use impact score. Note that the material contributions actually add to greater than 100%
due to the energy credit from incineration processes, discussed above. Coal waste from U.S.
electricity production is the single largest contributor to CRT impacts in this impact category,
followed by slag and ash from LPG production, and dust/sludge and fly bottom ash from U.S.
3-40
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3.3 BASELINE LCIA RESULTS
electricity production. Electricity is used to power the monitor during the use stage, while LPG
is primarily used in the production of CRT glass during manufacturing. LPG production also
results in an unspecified solid waste that contributes 4.5% of the CRT solid waste impact score,
while the CRT glass/frit process group generates a wastewater treatment sludge that contributes
5% of the score. Thus, the CRT glass/frit process group contributes about 30% of the CRT solid
waste impact score, either directly (as a result of the glass manufacturing process itself) or
indirectly (from LPG production). Other processes that are significant contributors include steel
production and the landfilling of a CRT at the end of its effective life. The latter value is based
on the assumption that 25% of CRTs that have reached their end of life are disposed of in a solid
waste landfill (see Section 2.5 and Appendix I).
Table 3-18. Top 99% of the CRT solid waste landfill use impact score
Life-cycle stage
Use
Manufacturing
Use
Use
Materials processing
End-of-Life
Manufacturing
Manufacturing
Process group
U.S. electric grid
LPG production
U.S. electric grid
U.S. electric grid
Steel production, cold-
rolled, semi-finished
CRT landfilling
LPG production
CRT glass/frit mfg.
Material
Coal waste
Slag and ash
Dust/sludge
Fly bottom ash
Unspecified solid waste
EOL CRT monitor, landfilled
Unspecified waste
Waste water treatment sludge
LCI data
type
Model/secondary
Secondary
Model/secondary
Model/secondary
Secondary
Primary
Secondary
Primary
Contribution
to impact
score*
38%
21%
12%
10%
6.6%
5.0%
4.5%
4.4%
* Column adds to greater than 100% due to a credit from incineration with energy recovery during the EOL life-cycle
stage.
CRT glass manufacturing data were collected specifically for the CDP, while data for
other process groups were either modeled by the CDP from secondary sources (e.g., U.S. electric
grid data) or are entirely from secondary sources (e.g., LPG and steel production data). The
mass and volume of CRT materials that are landfilled were developed for the CDP based on the
mass reported in each inventory data set (collected as primary data) and the density of CRT
materials assumed to be disposed of in a solid waste landfill. Note that the upstream inventories,
which were derived from secondary sources (i.e., Ecobilan), include electricity generation within
the materials manufacturing processes. These inventories do not include coal waste as an output,
but list "slag and ash" as an output. The different inventories used in this project have varying
nomenclature and some of the solid waste materials listed in the table may indeed overlap.
Table 3-19 presents the materials that contribute to the top 99% of the LCD solid waste
landfill use results. Like the CRT solid waste results, the material contributions in the table are
actually greater than 100% due to some negative values at end-of-life from an incinerator energy
credit. Coal waste, dust/sludge, and fly/bottom ash from U.S. electricity during the use stage
dominate the LCD solid waste impacts, contributing 68% of the impact score. Other significant
contributors include the following: (1) an unspecified solid waste from producing steel used in
the manufacture of the monitor, (2) slag and ash generated during the production of natural gas
which is then used by one LCD module/monitor manufacturer as an ancillary material (LNG)
during LCD module/monitor manufacture, (3) a wastewater treatment sludge from LCD
3-41
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3.3 BASELINE LCIA RESULTS
module/monitor manufacturing, (4) coal waste from the generation of electricity in Japan during
manufacturing, and (5) landfilling of non-hazardous or non-recovered components of the LCD at
the end of its effective life. The latter value is based on the assumption that 50% of LCDs are
sent to a solid waste landfill at the end of their effective lives.
Table 3-19. Top 99% of the LCD solid waste landfill use impact score
Life-cycle stage
Use
Use
Use
Materials processing
Materials processing
Manufacturing
Manufacturing
End-of-Life
Process group
U.S. electric grid
U.S. electric grid
U.S. electric grid
Steel production, cold-
rolled, semi-finished
Natural gas production
LCD monitor/module
mfg.
Japanese electric grid
LCD landfilling
Material
Coal waste
Dust/sludge
Fly /bottom ash
Unspecified solid waste
Slag and ash
Waste water treatment
sludge
Coal waste
EOL LCD monitor,
landfilled
LCI data
type
Model/secondary
Model/secondary
Model/secondary
Secondary
Secondary
Primary
Model/secondary
Primary
Contribution
to impact
score*
44%
13%
11%
9.9%
7.7%
5.6%
5.0%
3.5%
*Column adds to greater than 100% due to a credit from incineration with energy recovery during the EOL life-cycle
stage.
LCI data for LCD monitor/module manufacturing were collected by the CDP, and LCD
solid waste disposal volumes were estimated by the CDP based on the amounts and density of
LCD materials assumed to be disposed of in a solid waste landfill. Like the CRT, data for other
process groups either were modeled by the CDP from secondary data sources or came from
secondary sources. As discussed above for the CRT, the materials processing inventories from
secondary sources (i.e., Ecobilan) include electricity generation within the materials
manufacturing processes. The different inventories used in this project have varying
nomenclature and some of the solid waste materials listed in the table may indeed overlap.
3.3.4.2 Hazardous waste landfill use
Figure 3-6 presents the CRT and LCD LCIA results for the hazardous waste landfill use
impact category, based on the impact assessment methodology presented in Section 3.1.2.3.
Tables M-9 and M-10 (see Appendix M) present complete hazardous waste landfill use results
for the CRT and LCD, respectively. Hazardous waste landfill use impacts are characterized
from hazardous waste outputs with a disposition of landfill, which includes about 83% of the
9.46 kg of hazardous waste/functional unit generated by the CRT life cycle and about 27% of the
6.3 kg/functional unit generated by the LCD life cycle. This consumes approximately 0.017 m3
of hazardous waste landfill space for the CRT and 0.036 m3 for the LCD, based on the mass and
densities of the various materials. The results for both monitor types are dominated by monitor
disposal at the end of its effective life. Approximately 46% of CRTs and 5% of LCDs are
assumed to be landfilled as hazardous waste (see Section 2.5 and Appendix I).
3-42
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3.3 BASELINE LCIA RESULTS
~ 1.80E-02n
3
|S 1.20E-02-
O
c 6.00E-03 -
O.OOE+00
Hazardous waste
1.53E-02
1.41E-03
1.09E-04 O.OOE-I-OO
3.49E-03
1.07E-04 „ ,
1.50E-05 OOOEfOO
CRT
LCD
Monitor type
Figure 3-6. Hazardous waste impacts by life-cycle stage
Table 3-20 presents the materials that contribute to the top 99% of the CRT hazardous
waste landfill use results. About 91% of the total hazardous waste landfill space consumed
throughout the life-cycle of the CRT is from the amount of the monitor that is assumed to be
disposed of as hazardous waste. The next largest contributor is an unspecified hazardous waste
from LPG production. Most of this LPG is used to manufacture CRT glass. CRT outputs to a
hazardous waste landfill at the end-of-life were estimated by the CDP. The LPG inventory is
from secondary sources.
Table 3-20. Top 99% of the CRT hazardous waste landfill use impact score
Life-cycle stage
End-of-Life
Manufacturing
Process group
CRT landfilling
LPG production
Material
EOL CRT monitor, landfilled
Hazardous waste
LCI data
type
Primary
Secondary
Contribution to
impact score
91%
8.1%
Table 3-21 lists the top contributors to the LCD hazardous waste landfill use results.
LCD results are also dominated by landfilling of the LCD monitor at the end of its effective life,
even though only 5% of LCDs are assumed to be landfilled. Other significant contributors
include an unspecified hazardous waste from LPG production, and acetic acid from LCD
monitor/module manufacturing. LPG is used in the manufacture of LCD glass. LCD outputs to
a hazardous waste landfill at the end-of-life were estimated by the CDP. The LPG inventory is
from secondary sources.
Table 3-21. Top 99% of the LCD hazardous waste landfill use im
jact score
Life-cycle
stage
End-of-Life
Manufacturing
Manufacturing
Process group
LCD landfilling
LPG production
LCD monitor/module mfg.
Material
EOL LCD monitor, landfilled
Hazardous waste
Acetic acid
LCI data
type
Primary
Secondary
Primary
Contribution to
impact score
97%
1.8%
0.88%
3-43
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3.3 BASELINE LCIA RESULTS
3.3.4.3 Radioactive waste landfill use
Figure 3-7 presents the CRT and LCD LCIA results for the radioactive waste landfill use
impact category, based on the impact assessment methodology presented in Section 3.1.2.3.
Tables M-l 1 and M-12 in Appendix M present complete results for the CRT and LCD,
respectively. Life-cycle radioactive waste landfill use indicators for the CRT are 1.81E-04 m3
per monitor for the CRT and 9.22E-05 m3 per monitor for the LCD. As shown in the figure,
CRT radioactive waste landfill impacts are dominated by radioactive waste disposal in the use
stage, which contributes about 79% of the total impacts. This result is to be expected, given the
relatively large amount of electricity consumed by a CRT during use and the associated
radioactive waste from nuclear power plants. The use stage also contributes the greatest amount
of LCD impacts (58%), but the manufacturing stage is also a significant contributor (33%) due to
electricity consumed during manufacturing. LCD manufacturing electricity is linked to the
Japanese electric grid, which derives 31% of its power from nuclear sources. By comparison,
about 20% of the U.S. electric grid is powered by nuclear sources.
•1 1.50E-04-,
3
g 1.00E-04
O
?
£ O.UUb-UO
3
^ O.OOE+00
2.7
Radioactive waste • Upstream
• Mfg
1.43E-04 DUse
4E-05 1 12E-05
I
I
DEOL
5.32E-05
.U4L-UJ
1.43E-08 8.55E-06 | | 101E-08
| | |
1 '
CRT LCD
Monitor type
Figure 3-7. Radioactive waste impacts by life-cycle stage
Table 3-22 lists the materials that contribute to the top 99% of the CRT radioactive waste
landfill use score and the LCI data type. Note that the LCI data for all of the materials in the
table are from secondary sources or models. Low-level radioactive waste and depleted uranium
from the U.S. electric grid are the radioactive materials being landfilled in the greatest quantities,
followed by low-level radioactive waste from the production of steel used in the monitor. The
latter radioactive waste is a byproduct of electricity production used in the manufacture of steel.
It should be noted that the electricity generation data utilized in the steel inventory are from
France (Glazebrook, 2001), where a large percentage of electricity is derived from nuclear
sources. Therefore, these emissions may not be representative of emissions from steel production
in some parts of Asia or in the United States. This issue is discussed further in the section on
limitations and uncertainties, below.
3-44
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3.3 BASELINE LCIA RESULTS
Table 3-22. Top 99% of the CRT radioactive waste landfill use impact score
Life-cycle stage
Use
Use
Materials processing
Manufacturing
Materials processing
Materials processing
Manufacturing
Manufacturing
Process group
U.S. electric grid
U.S. electric grid
Steel production, cold-
rolled, semi-finished
Japanese electric grid
Invar
Ferrite manufacturing
Japanese electric grid
U.S. electric grid
Material
Low-level radioactive waste
Uranium, depleted
Low-level radioactive waste
Low-level radioactive waste
Low-level radioactive waste
Low-level radioactive waste
Uranium, depleted
Low-level radioactive waste
LCI data
type
Model/secondary
Model/secondary
Secondary
Model/secondary
Secondary
Secondary
Model/secondary
Model/secondary
Contribution
to impact
score*
61%
18%
9.0%
3.8%
2.6%
2.5%
1.1%
0.97%
*Corumn may not add to 99% due to rounding.
Other significant contributors to the CRT radioactive waste score include low-level
radioactive waste from electricity used in Japan during manufacturing, and low-level radioactive
waste from invar and fertile manufacturing. Invar is an alloy of nickel and iron. Like the steel
data discussed above, the invar and fertile manufacturing data also include emissions from
electricity production. Finally, low-level radioactive waste from U.S. electricity consumed during
the manufacturing stage contributes slightly less than 1% of the CRT radioactive waste landfill
use impacts. The frit and PWB manufacturing processes consume this electricity. These are the
only CRT components linked to the U.S. grid.
Table 3-23 lists the materials that contribute to the top 99% of the LCD radioactive waste
landfill use results and the LCI data type. Note that LCI data for all of the primary contributors to
this impact category are from secondary sources or modeled from secondary sources. Together,
low-level radioactive waste and depleted uranium disposal from electricity consumed during use
of the monitor account for about 57% of the LCD radioactive waste landfill use indicator,
followed by low-level radioactive waste and depleted uranium disposal from electricity used
during manufacturing (roughly 32%). Waste disposal from steel production is also a significant
contributor at 8.7%. Like the CRT data discussed above, these emissions occur from electricity
production in France and may not be representative of U.S. or some Asian practices.
Table 3-23. Top 99% of the LCD radioactive waste disposal impact score
Life-cycle stage
Use
Manufacturing
Use
Materials processing
Manufacturing
Process group
U.S. electric grid
Japanese electric grid
U.S. electric grid
Steel production, cold-
rolled, semi-finished
Japanese electric grid
Material
Low-level radioactive waste
Low-level radioactive waste
Uranium, depleted
Low-level radioactive waste
Uranium, depleted
LCI data
type
Model/secondary
Model/secondary
Model/secondary
Secondary
Model/secondary
Contribution
to impact
score*
44%
25%
13%
8.7%
7.5%
*Column may not add to 99% due to rounding.
3-45
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3.3 BASELINE LCIA RESULTS
3.3.4.4 Limitations and uncertainties
Landfill use pertains to the use of suitable and designated landfill space as a natural
resource where the specified type of waste (solid, hazardous, or radioactive) is accepted.
Landfill use impacts are characterized from solid, hazardous, or radioactive waste outputs with a
disposition of landfill. Impact characterization is based on the volume of waste determined from
the inventory mass amount of waste and materials density of each specific waste. Note that
different countries may have different landfill designations for the final disposition of similar
waste streams (e.g., a waste considered hazardous in the U.S. may be accepted in a solid waste
landfill elsewhere). However, where possible, equivalent landfills (e.g., special waste landfills
and hazardous waste landfills) were considered for these impact categories.
CRT and LCD impact results for the solid and radioactive waste landfill use categories
were driven almost entirely by waste outputs reported in inventories from secondary sources.
These inventories were not developed specifically for the CDP and therefore are subject to the
limitations and uncertainties associated with secondary data (see Section 2.2.2 and 3.3.2). In
particular, radioactive waste disposal from some of the upstream materials processing data may
not be representative of conditions in the U.S. or parts of Asia. These data include emissions
from electricity production within the materials inventory, which are the primary source of
radioactive waste streams. For example, steel production data include the French electric grid,
where a large percentage of the power supply comes from nuclear power plants. In addition,
some of the upstream data may not be representative of current conditions, with steel production
data covering the period from 1975 to 1990 and invar production data being from 1991.
CRT and LCD impact results for the hazardous waste landfill use category were
dominated by monitor disposal at the end of their effective lives. Hazardous waste landfill
disposal volumes were estimated based on the percent of monitors with hazardous waste
landfilling as their final disposition, the monitor mass, and the material densities. However, data
on the percentage of CRTs that are landfilled are not separated into hazardous and non-
hazardous landfilling processes. Therefore, these percentages were estimated by the CDP, as
described in Appendix I. Even less is known about the final disposition of LCDs, particulary
since very few LCD desktop monitors have reached the end of their effective lives (and then,
only if they have been damaged in some way). Therefore, the effect of different LCD EOL
dispositions was evaluated in a sensitivity analysis (see Section 3.4.)
3.3.5 Global Warming
Figure 3-8 presents the CRT and LCD LCIA results for the global warming impact
category, based on the impact assessment methodology presented in Section 3.1. Tables M-13
and M-14 in Appendix M list complete global warming results for the CRT and LCD,
respectively. The life-cycle global warming indicators for the CRT and LCD were 695 and 593
kg of CO2 equivalents per monitor, respectively. The CRT global warming indicators are driven
by the use life-cycle stage, which contributes about 66% of the total. The manufacturing stage,
which contributed 88% of the CRT energy consumption impacts, only contributes about 29% of
the total global warming score. LCD global warming impacts, on the other hand, have the
greatest contribution from the manufacturing life-cycle stage, which accounts for about 40% of
the potential impacts in this category. Both the upstream (materials processing) and use
3-46
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3.3 BASELINE LCIA RESULTS
life-cycle stages are also significant contributors to the LCD global warming results, accounting
for 31% and 29% of the total, respectively.
500 -i
kg-CO2-equiv.
functional uni
-^ NJ GO -t*
0000
D 0 0 0 0
Global warming • Upstream
• Mfg
459 DUse
203
DEOL
240
18°
\tu 171
1.3 0.57
CRT LCD
Monitor type
Figure 3-8. Global warming impacts by life-cycle stage
One might expect the distribution of global warming impacts across life-cycle stages to
mirror those of energy consumption, as CO2 is generally a large emission from electricity
generation. However, as discussed in Section 3.3.3, CRT energy impacts are greatest in the
manufacturing stage due to the large amounts of energy used to manufacture glass. Since the
energy used in glass manufacturing is not only from electricity, but more so from other fuels
(LPG, natural gas, and fuel oil), there is not a direct correlation between CRT global warming
impacts and CRT energy impacts.
The distribution of LCD global warming impacts across life-cycle stages does mirror the
distribution of LCD energy use impacts discussed in Section 3.3.3. However, as discussed
below, the manufacturing stage global warming impacts for the LCD are being driven more by
the use of sulfur hexafluoride (SF6) in LCD monitor/module manufacturing than by the use of
electricity.
3.3.5.1 Major contributors to the CRT global warming results
Table 3-24 presents the life-cycle inventory items contributing to the top 99% of the CRT
global warming results and the LCI data type (primary, secondary, or model/secondary). As
shown in the table, CRT global warming impacts are dominated by CO2 emissions from
electricity generation during use of the monitor, followed by CO2 and methane emissions from
producing LPG used as fuel in the CRT glass/frit process group. Together these three emissions
contribute almost 89% of the CRT life-cycle global warming score. Carbon dioxide and
methane emissions from a number of other processes also add to the CRT global warming score,
as does nitrous oxide emissions from the LPG production process. It is likely that most of the
CO2 emissions from the materials processing life-cycle stage can be attributed to emissions from
electricity generation or fuel combustion. As discussed in Section 2.2.2.1, the upstream
materials processing inventories used in this study include data from electricity generation.
3-47
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3.3 BASELINE LCIA RESULTS
Note that almost all of the LCI data for global warming emissions are from secondary
sources. This is because the CRT global warming results are dominated by CO2 emissions from
electricity generation, and electric grid data were either developed by the CDP from secondary
sources or already included in the upstream, materials processing inventories from secondary
sources.
Table 3-24. Top 99% of the CRT global warming impact score
Life-cycle stage
Use
Manufacturing
Manufacturing
Manufacturing
Use
Materials processing
Manufacturing
Manufacturing
Materials processing
Materials processing
End-of-Life
Manufacturing
Materials processing
Materials processing
Process group
U.S. electric grid
LPG production
LPG production
Japanese electric grid
U.S. electric grid
Steel production, cold-rolled,
semi-finished
U.S. electric grid
LPG production
Polycarbonate production
Aluminum production
CRT incineration
CRT glass/frit mfg.
Invar
Styrene-butadiene copolymer
production
Material
Carbon dioxide
Carbon dioxide
Methane
Carbon dioxide
Methane
Carbon dioxide
Carbon dioxide
Nitrous oxide
Carbon dioxide
Carbon dioxide
Carbon dioxide
Carbon dioxide
Carbon dioxide
Carbon dioxide
LCI data
type
Model/secondary
Secondary
Secondary
Model/secondary
Model/secondary
Secondary
Model/secondary
Secondary
Secondary
Secondary
Secondary
Primary
Secondary
Secondary
Contribution
to impact
score*
64%
22%
2.5%
2.2%
1.9%
1.9%
1.0%
0.72%
0.66%
0.52%
0.51%
0.40%
0.33%
0.24%
*Column may not add to 99% due to rounding.
3.3.5.2 Major contributors to the LCD global warming results
Table 3-25 presents the life-cycle inventory items contributing to the top 99% of the LCD
global warming results and the LCI data type (primary, secondary, or model/secondary). Sulfur
hexafluoride used in LCD module manufacturing is the single largest contributor to LCD global
warming impacts, followed by CO2 emissions from electricity generation during the use stage,
CO2 and methane emissions from natural gas production, and CO2 emissions from the generation
of electricity used during manufacturing in Japan.
3-48
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3.3 BASELINE LCIA RESULTS
Table 3-25. Top 99% of the LCD global warming impact score
Life-cycle stage
Manufacturing
Use
Materials processing
Materials processing
Manufacturing
Manufacturing
Materials processing
Use
Materials processing
Materials processing
Manufacturing
End-of-Life
Process group
LCD monitor/module mfg.
U.S. electric grid
Natural gas production
Natural gas production
Japanese electric grid
LPG production
Steel production, cold-
rolled, semi-finished
U.S. electric grid
PMMA sheet production
Polycarbonate production
Natural gas production
LCD incineration
Material
Sulfur hexafluoride
Carbon dioxide
Carbon dioxide
Methane
Carbon dioxide
Carbon dioxide
Carbon dioxide
Methane
Carbon dioxide
Carbon dioxide
Carbon dioxide
Carbon dioxide
LCI data
type
Primary
Model/secondary
Secondary
Secondary
Model/secondary
Secondary
Secondary
Model/secondary
Secondary
Secondary
Secondary
Secondary
Contribution to
impact score*
29%
28%
16%
12%
8.7%
1.2%
1.1%
0.85%
0.45%
0.43%
0.35%
0.35%
*Corumn may not add to 99% due to rounding.
Sulfur hexafluoride is a potent global warming gas, with a global warming potential
(GWP) equivalancy factor of 23,900 CO2 equivalents (see Table K-2 in Appendix K). It is used
as an etchant in a dry-etching process of amorphus silicon and SiNx films. The CO2 and
methane emissions from natural gas production can be attributed to the use of LNG as an
ancillary material in LCD monitor/module manufacturing. However, as discussed in the section
on non-renewable resource use (Section 3.3.2), only one LCD module manufacturer reported this
use of LNG.
Carbon dioxide emissions (and, in one case, methane emissions) round out the remainder
of the primary contributors to the LCD global warming indicator. Most of the carbon dioxide
emissions occur from upstream processes and are due to electricity generation. With the
exception of the SF6 data, the LCI data for all of the top LCD global warming emissions are from
secondary sources. Sulfur hexaflouride emissions data were developed by the CDP based on an
emissions factor (0.45) applied to SF6 inputs reported by LCD monitor/module manufacturers.
The emissions factor is from the Intergovernmental Panel on Climate Change publication, Good
Practice Guidance and Uncertainty Management in National Greenhouse Gas Inventories
(Penman etal, 2000.)
3.3.5.3 Limitations and uncertainties
Global warming potential (GWP) refers to the warming that emissions of certain gases
may contribute by building up in the atmosphere and trapping the earth's heat. As discussed in
Section 3.1.2.4, the LCIA methodology for global warming impacts uses published GWP
equivalency factors having effects in the 100-year time horizon. These effects are expected to be
far enough into the future that releases occurring throughout the life cycle of a computer monitor
would be within the 100-year timeframe.
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3.3 BASELINE LCIA RESULTS
The effects of the buildup of global warming gases in the atmosphere is still the subject
of scientific debate, but in 1995 the Intergovernmental Panel on Climate Change (TPCC),
representing the consensus of most climate scientists worldwide, concluded that"... the balance
of evidence...suggests that there is a discernible human influence on global climate (IPCC,
1995)." Other than the limitations and uncertainties inherent in predicting future effects, most of
the limitations and uncertainties in the CRT and LCD global warming results have to do with the
LCI data on greenhouse gas emissions, which occur primarily from electricity generation
processes.
As noted above, the U.S. and Japan electric grid inventories used in the CDP were
developed by the CDP, and electric grids used with upstream processes are embedded in the
upstream inventories. U.S. electric grid emissions of CO2 are based on data in the EPA
publication, National Air Quality and Emissions Trends Report, 1997 (EPA, 1998), which were
the best data available when the electric grid inventory data was developed and are expected to
be reasonably accurate. However, the Japanese electric grid inventory was derived from the U.S.
inventory based on the mix of fuels used in Japan. Because Japanese power plants may employ
different pollution control devices, use fuels of different quality, or other factors, their
greenhouse gas emissions could actually be higher or lower than those reported in the inventory.
Similarly, the electric grid inventories embedded in upstream, materials processing
inventories may have differing geographic and temporal boundaries or may be representative of
older technologies. Therefore, actual emissions of greenhouse gases could be higher or lower
than reported. This is a common limitation of LCAs, which must often rely on secondary data
sources to avoid the considerable time and resources required to collect primary data for every
process.
3.3.6 Stratospheric Ozone Depletion
Figure 3-9 presents the CRT and LCD LCIA results for the stratospheric ozone depletion
impact category by life-cycle stage, based on the impact assessment methodology presented in
Section 3.1.2.5. Note that most of the CRT ozone depletion impacts occur from the use stage
(50%) and the upstream, materials processing stages (45%), while most of the LCD ozone
depletion impacts occur from the manufacturing stage (63%). As will be shown later, this is
important because upstream and use stage data are primarily from secondary data sources,
whereas manufacturing data were collected by the CDP. Tables M-15 and M-16 in
Appendix M list complete stratospheric ozone depletion results for the CRT and LCD,
respectively.
3-50
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3.3 BASELINE LCIA RESULTS
^ 3.00E-05 n
.> *-
=. '| 2.00E-05 -
0) _
' re
T- c 1 OOE-05 -
0 'J=
LL <->
9c n OOF+OO
O) «-
-1. OOE-05 -
uzone depletion B upstream
• Mfg
QUse
DEOL
9.30E-06 1.03E-05 8.63E-06
1 08b-06 3.83E-06
1 .oob-Uo
-1.69E-07 ' -1.11E-07
CRT LCD
Monitor type
Figure 3-9. Ozone depletion impacts by life-cycle stage
The ozone depletion impact category indicator was 2.05E-05 kg of CFC-11 equivalents
per monitor for the CRT and 1.37E-05 kg of CFC-11 equivalents per monitor for the LCD.
However, for both the CRT and the LCD, many of the materials contributing to this impact
category are listed as Class I ozone depleting substances in Title VI of the 1990 Clean Air Act
Amendments, and therefore were required to be phased out of U.S. production by January 1,
1996. Production of these substances was also phased out in other developed countries under the
Montreal Protocol and its Amendments and Adjustments, but continues today in some
developing countries. An exception is bromomethane, which is a Class I substance that will not
be completely phased out of production until 2005 (EPA, 200la).
For a few of the phased out substances, a significant amount of inventory remained after
production was phased out. However, most of these inventories are now exhausted, and Class I
ozone depleting substances are rarely used by manufacturers in developed countries. If we
delete the phased out substances from the CRT and LCD inventories, the CRT ozone depletion
indicator is reduced 47% from 2.05E-05 to 1.09E-05 kg of CFC-11 equivalents per monitor, and
the LCD result is reduced 14% from 1.37E-05 to 1.18E-05 kg of CFC-11 equivalents per
monitor. These latter values are probably more representative of the temporal boundaries for
primary data collected in the CDP LCA. Thus, when all data are included in the ozone depletion
calculations, the CRT has a greater ozone depletion impact score than the LCD, but the results
are switched (LCD greater than CRT) when phased out substances are removed from the
inventory.
3.3.6.1 Major contributors to the CRT ozone depletion results
Table 3-26 lists the materials that contribute to the top 99% of the CRT life-cycle ozone
depletion impact score and the LCI data type. Bromomethane emissions from electricity
generated in the use stage are the single largest contributor to the CRT ozone depletion indicator,
accounting for almost half of the total score. Most of the other materials in the table are emitted
from materials production processes in the upstream, materials processing life-cycle stage.
Exceptions are bromomethane emissions from the LPG production process (used to produce
3-51
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3.3 BASELINE LCIA RESULTS
LPG for the glass/frit process group), 1,1,1-trichloroethane emissions from electricity generation
in the use stage, and bromomethane emissions from electricity used in manufacturing.
Table 3-26. Top 99% of the CRT stratospheric ozone depletion impact score
Life-cycle stage
Use
Materials processing
Materials processing
Materials processing
Manufacturing
Materials processing
Materials processing
Use
Manufacturing
Process group
U.S. electric grid
ABS production
Aluminum production
Invar
LPG production
Lead
Steel production, cold-
rolled, semi-finished
U.S. electric grid
U.S. electric grid
Material
Bromomethaneb
HALON-1301b
HALON-1301b
HALON-1301b
Bromomethaneb
HALON-1301b
HALON-1301b
l,l,l-Trichloroethaneb
Bromomethaneb
LCI data
type
Model/secondary
Secondary
Secondary
Secondary
Secondary
Secondary
Secondary
Model/secondary
Model/secondary
Contribution to
impact score3
49%
20%
14%
5.9%
3.7%
2.6%
2.0%
1.1%
0.78%
a Column may not add to 99% due to rounding.
b Class I substance as listed in Title VI of the Clean Air Act Amendments.
Note that all of the materials listed in Table 3-26 are Class I ozone depleting substances.
As discussed above, all of these substances except bromomethane were phased out of production
by January 1, 1996. Note also that all of the LCI data for the materials in the table are from
secondary sources. For both of these reasons, the LCI data for the materials in the table are
highly uncertain. This is discussed further under limitations and uncertainties, below.
3.3.6.2 Major contributors to the LCD ozone depletion results
Table 3-27 lists the top contributors to the LCD life-cycle stratospheric ozone depletion
indicator and the LCI data type. Together HCFC-225cb and HCFC 225ca used in the LCD panel
components process group account for 59% of the LCD ozone depletion indicator. Note that
HCFC 225cb and HCFC 225ca are Class II ozone depleting substances that are not scheduled for
phaseout until 2015. [Under U.S. regulations and the Montreal Protocol and its Amendments and
Adjustments these substances can not be produced or imported after 2015, except for use as
refrigerants in equipment manufactured before January 1, 2020 (EPA, 200lb).] Also note that
the impact scores for these materials are based on primary LCI data collected from
manufacturers. Therefore, these data are considered to be more reliable than data for Phase I
substances from secondary sources.
3-52
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3.3 BASELINE LCIA RESULTS
Table 3-27. Top 99% of the LCD stratospheric ozone depletion use impact score
Life-cycle stage
Manufacturing
Use
Manufacturing
Materials processing
Manufacturing
Materials processing
Process group
LCD panel components
U.S. electric grid
LCD panel components
Aluminum production
(virgin)
Japanese electric grid
Steel production, cold-
rolled, semi-finished
Material
HCFC-225cbb
Bromomethane0
HCFC-225cab
HALON-1301C
Bromomethane0
HALON-1301C
LCI data
type
Primary
Model/secondary
Primary
Secondary
Model/secondary
Secondary
Contribution to
impact score3
34%
27%
25%
7.8%
3.1%
1.4%
a Column may not add to 99% due to rounding.
b Class II substance as listed in Title VI of the Clean Air Act Amendments.
0 Class I substance as listed in Title VI of the Clean Air Act Amendments.
Other significant contributors to the LCD ozone depletion score include bromomethane
emissions from electricity generation in the United States and Japan, and halon emissions from
upstream, materials processing stages. As noted above in the discussion of CRT ozone depletion
results, the halons were phased out of production in 1996, which suggests that these data are not
representative of current conditions. Bromomethane is still being produced, but bromomethane
emissions data are also uncertain as will be discussed in the section on limitations and
uncertainties, below.
3.3.6.3 Limitations and uncertainties
Both the CRT and LCD life-cycle stratospheric ozone depletion results are highly
uncertain due to the inclusion of a number of Class I ozone depleting substances in inventories
from secondary sources. As discussed above, except for bromomethane, developed countries
that are parties to the Montreal Protocol and its Amendments and Adjustments phased out the
production of Class I substances by 1996. To better assess the uncertainties in these results,
Table 3-28 lists the geographic and temporal boundaries for the life-cycle inventories of the
process groups listed in tables 3-26 and 3-27, above.
3-53
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3.3 BASELINE LCIA RESULTS
Table 3-28. Geographic and temporal boundaries of inventories contributing to the CRT
and/or LCD ozone depletion indicator results
Process group
ABS production
Aluminum production
Invar production
Japanese electric grid
LCD panel components
Lead production
LPG production
Steel production
U.S. electric srid
Geographic boundaries
Germany, Italy, Netherlands
Not provided
Multiple countries
U.S. and Japan8
Japan
Not provided
Mainly U.S.
Multiple countries
U.S.
Temporal boundaries
1997
Not provided
1991 (nickel), Not provided (lead)
1993b
1998
Not provided
1983-1993
1975-1990
1993b
a Based on the U.S. electric grid inventory modified to account for the fuel mix used in Japan.
b Date of stack tests from which bromomethane emission factor was developed (from EPA Web site: Emission
Factor Documentation for AP-42 Section 1.1: Bituminous and Subbituminous Coal Combustion.
http://www.epa.gov/ttn/chief/ap42/ch01/bgdocs/b01s01.pdf.)
The most recent data are for LCD panel components manufacturing, which are primary
data collected from manufacturers in Japan by the CDP and expected to be of better quality than
older data from secondary sources. Data for ABS production are also fairly recent, dating from
1997. However, the temporal boundaries for most of the data are either not listed in the
inventories, or pre-date the Class I substance production phase out. In addition, most of the data
are from Europe and/or the United States, where very few Class I ozone depleting substances are
currently used. Thus, we suspect that emissions of Class I substances reported in the inventories
no longer occur, indicating that the CRT and LCD life-cycle impact results should be reduced to
2.05E-05 kg of CFC-11 equivalents per monitor for the CRT, and 1.37E-05 kg of CFC-11
equivalents per monitor for the LCD.
Bromomethane is a Class I ozone depleting substance that has not yet been phased out of
production and is emitted during coal combustion to produce electricity. Bromoethane
emissions from electricity production are estimated from an emission factor reported in AP-42,
the EPA compilation of air pollutant emission factors (EPA, 1996). EPA (1996) provides an
emission factor rating that is, "an overall assessment of how good a factor is, based on both the
quality of the test(s) or information that is the source of the factor and on how well the factor
represents the emission source." The bromomethane emissions factor rating is "D," or below
average, indicating CDP data quality for bromomethane emissions from electricity generation is
also below average.
In conclusion, it appears that most of the Class I substance emissions data are highly
uncertain or of below average quality. Manufacturing data collected by the CDP, which includes
emissions of Class II substances, are of better quality and expected to be more representative of
current conditions. When all data are included in the ozone depletion calculations, the CRT has
a greater ozone depletion impact score than the LCD. However, if we remove phased out
substances from the inventory, the results are switched with the LCD having a greater score in
this category than the CRT.
3-54
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3.3 BASELINE LCIA RESULTS
3.3.7 Photochemical Smog
Figure 3-10 presents the CRT and LCD LCIA results for the photochemical smog impact
category by life-cycle stage. These results were calculated using the impact assessment
methodology presented in Section 3.1.2.6. Tables M-17 and M-18 in Appendix M list complete
results for the CRT and LCD, respectively. One 17" CRT monitor produces 0.171 kg of ethene
equivalents throughout its life cycle, while a functionally equivalent 15" LCD monitor produces
0.141 of ethene equivalents. The CRT photochemical smog impact score is dominated by
emissions during the manufacturing stage (71% of total); the LCD impact score is dominated by
emissions during the upstream, materials processing stages (91% of total). However, as
discussed below, it is fossil fuel production processes that emit the majority of smog forming
emissions during the life-cycle of either monitor type. Both the CRT and LCD receive a slight
credit on emissions of smog forming chemicals at the end of their effective lives due to energy
recovery from incineration processes.
0.200 n
.> ~ 0.150
o- =
a> « 0.100
(I) C
5 := 0 050 -
£ °
tt) 5 o 000
0) «-
^ -0.050
Smog formation n Upstream
• Mfg
DUse
0.121 0.129 DEOL
0.047
| 0.005 .0.002 U'UIZ_ o.002 -°-001
CRT LCD
Monitor type
Figure 3-10. Smog formation impacts by life-cycle stage
3.3.7.1 Major contributors to the CRT photochemical smog results
Table 3-29 lists the materials that contribute to the top 99% of the CRT photochemical
smog indicator result. The LPG production process alone, which emits various unspeciated
hydrocarbons, benzene, aldehydes, ethane, and formaldehyde, accounts for almost 67% of CRT
photochemical smog impacts. As noted earlier in the discussion of other impact category
indicators, most of this LPG is used as a fuel source in CRT glass manufacturing. However,
CRT glass energy data reported in the three data sets received by the CDP were highly variable
and therefore the subject of a sensitivity analysis (see Section 3.4).
Other materials responsible for more than 1% of the CRT photochemical smog score
include the following: (1) hydrocarbon (methane and nonmethane) emissions associated with
steel production, (2) methane emissions from electricity generation during the use stage,
(3) toluene emissions from CRT tube manufacturing, (4) nonmethane hydrocarbon emissions
associated with ABS production, and (5) nonmethane hydrocarbon emissions associated with
polycarbonate production. Note that the inventory for each upstream material (e.g., steel
3-55
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3.3 BASELINE LCIA RESULTS
production, ABS production, etc.) contains data from the raw materials extraction, materials
manufacture, and (usually) electricity generation processes. Therefore, hydrocarbon emissions
associated with steel production, for example, could be from one of many individual processes,
such as the steel production process itself, from fuels consumed during the mining of ore, or
from the combustion of fuels as an energy source during steel manufacturing.
Table 3-29. Top 99% of the CRT photochemical smog impact score
Life-cycle stage
Manufacturing
Manufacturing
Materials processing
Manufacturing
Use
Materials processing
Manufacturing
Manufacturing
Materials processing
Materials processing
Materials processing
Manufacturing
Materials processing
Manufacturing
Materials processing
Materials processing
Manufacturing
Manufacturing
Materials processing
Manufacturing
Manufacturing
Manufacturing
Manufacturing
Manufacturing
Process group
LPG production
LPG production
Steel production, cold-
rolled, semi-finished
LPG production
U.S. electric grid
Steel production, cold-
rolled, semi-finished
LPG production
CRT tube mfg.
ABS production
Polycarbonate
production
Aluminum production
Natural gas production
ABS production
LPG production
Stryene-butadiene
copolymer production
Invar
Fuel oil #6 production
LPG production
Lead
Fuel oil #6 production
Natural gas production
LPG production
CRT tube mfg.
LPG production
Material
Hydrocarbons, unspeciated
Nonmethane hydrocarbons,
unspeciated
Nonmethane hydrocarbons,
unspeciated
Methane
Methane
Hydrocarbons, unspeciated
Benzene
Toluene
Nonmethane hydrocarbons,
unspeciated
Nonmethane hydrocarbons,
unspeciated
Nonmethane hydrocarbons,
unspeciated
Nonmethane hydrocarbons,
unspeciated
Nonmethane hydrocarbons,
unspeciated
Aldehydes
Hydrocarbons, remaining
unspeciated
Nonmethane hydrocarbons,
unspeciated
Hydrocarbons, unspeciated
Formaldehyde
Nonmethane hydrocarbons,
unspeciated
Nonmethane hydrocarbons,
unspeciated
Methane
Ethane
Xylene (mixed isomers)
Pentane
LCI data
type
Secondary
Secondary
Secondary
Secondary
Model/secondary
Secondary
Secondary
Primary
Secondary
Secondary
Secondary
Secondary
Secondary
Secondary
Secondary
Secondary
Secondary
Secondary
Secondary
Secondary
Secondary
Secondary
Primary
Secondary
Contribution
to impact
score*
36%
25%
19%
3.4%
2.6%
2.0%
1.6%
1.3%
1.3%
1.1%
0.86%
0.53%
0.41%
0.39%
0.39%
0.32%
0.31%
0.29%
0.21%
0.21%
0.21%
0.18%
0.17%
0.16%
3-56
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3.3 BASELINE LCIA RESULTS
Table 3-29. Top 99% of the CRT photochemical smog impact score
Life-cycle stage
Manufacturing
Process group
Natural gas production
Material
Benzene
LCI data
type
Secondary
Contribution
to impact
score*
0.14%
*Corumn may not add to 99% due to rounding.
3.3.7.2 Major contributors to the LCD photochemical smog results
Table 3-30 lists the materials that contribute to the top 99% of the LCD life-cycle
photochemical smog results. LCD results are dominated by unspeciated hydrocarbon emissions,
methane emissions, and benzene emissions from natural gas production in the materials
processing life-cycle stage, which together account for about 75% of the total. This natural gas
is used as an ancillary material by one LCD monitor/module manufacturer. Other LCD
monitor/module manufacturers reported using LNG as a fuel, but not as an ancillary number. A
number of other materials and processes contribute more than 1% of the total LCD
photochemical smog score, most notably unspeciated, nonmethane hydrocarbon emissions
associated with steel production. As noted above under the CRT results, the latter hydrocarbon
emissions could occur from any one of various processes (e.g., ore mining, steel production,
electricity generation, etc.) wrapped into the steel production inventory.
Table 3-30. Top 99% of the LCD photochemical smog impact score
Life-cycle stage
Materials processing
Materials processing
Materials processing
Materials processing
Manufacturing
Manufacturing
Manufacturing
Materials processing
Materials processing
Use
Manufacturing
Materials processing
Materials processing
Manufacturing
Process group
Natural gas production
Natural gas production
Natural gas production
Steel production, cold-
rolled, semi-finished
LCD monitor/module
mfg.
LPG production
LPG production
Natural gas production
Steel production, cold-
rolled, semi-finished
U.S. electric grid
Natural gas production
PMMA sheet production
Polycarbonate production
Natural gas production
Material
Nonmethane
hydrocarbons, unspeciated
Methane
Benzene
Nonmethane
hydrocarbons, unspeciated
Isopropyl alcohol
Hydrocarbons, unspeciated
Nonmethane
hydrocarbons, unspeciated
Hydrocarbons, unspeciated
Hydrocarbons, unspeciated
Methane
Nonmethane
hydrocarbons, unspeciated
Nonmethane
hydrocarbons, unspeciated
Nonmethane
hydrocarbons, unspeciated
Methane
LCI data
type
Secondary
Secondary
Secondary
Secondary
Primary
Secondary
Secondary
Secondary
Secondary
Model/secondary
Secondary
Secondary
Secondary
Secondary
Contribution
to impact
score*
45%
17%
12%
11%
2.5%
2.1%
1.4%
1.2%
1.2%
1.2%
1.0%
0.87%
0.73%
0.39%
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3.3 BASELINE LCIA RESULTS
Table 3-30. Top 99% of the LCD photochemical smog impact score
Life-cycle stage
Materials processing
Materials processing
Process group
Aluminum production
PET resin production
Material
Nonmethane
hydrocarbons, unspeciated
Nonmethane
hydrocarbons, unspeciated
LCI data
type
Secondary
Secondary
Contribution
to impact
score*
0.39%
0.36%
*Corumn may not add to 99% due to rounding.
3.3.7.3 Limitations and uncertainties
Photochemical smog indicators are calculated using the mass of a chemical released to air
per functional unit and the chemical-specific partial equivalency factor. The equivalency factor
is a measure of the chemical's photochemical oxidant creation potential (POCP) compared to the
reference chemical ethylene. As noted in Section 3.1.2.6, photochemical smog impacts are
based on partial equivalency because some chemicals cannot be converted into POCP
equivalency factors (e.g., nitrogen oxide). The inability to develop equivalency factors for some
chemicals is a limitation of the photochemical smog impact assessment methodology.
The CRT impact score for photochemical smog formation is being driven by the process
for producing the large amount of LPG used in CRT glass manufacture. However, as discussed
in Section 2.3.3.3 and previous subsections of this Section 3.3, the three sets of glass
manufacturing energy data received by the CDP were highly variable, making the average glass
energy inputs used in the baseline analysis uncertain. Therefore, the emissions of smog forming
chemicals from LPG production, which are based on the glass LPG inputs, are also uncertain.
CRT glass energy inputs were subjected to a sensitivity analysis. Sensitivity results are
discussed in Section 3.4.
The LCD impact score for photochemical smog formation is being driven by the natural
gas production process to produce the large amount of LNG used as an ancillary material during
LCD monitor/module manufacturing. However, as discussed earlier, only one LCD
monitor/module manufacturer reported this use of LNG, which indicates the average LNG inputs
used in the LCD inventory may be unduly high. Therefore, the mass of smog forming chemical
emissions from the natural gas production process, which are based on the amount of ancillary
LNG inputs, may also by unduly high.
The majority of the CRT and LCD photochemical smog results are based on life-cycle
inventories from secondary sources and are therefore subject to the limitations and uncertainties
associated with secondary data, discussed previously. In particular, see Section 3.3.1.1 for a
detailed discussion of limitations and uncertainties in the LPG and natural gas production data.
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3.3 BASELINE LCIA RESULTS
3.3.8 Acidification
Figure 3.11 presents the CRT and LCD LCIA results for the acidification impact
category, based on the impact assessment methodology presented in Section 3.1.2.7. Tables M-
19 and M-20 in Appendix M list complete results for the CRT and LCD, respectively. The life-
cycle acidification impact indicator result is 5.25 kg of SO2 equivalents per monitor for the CRT
and 2.96 kg of SO2 equivalents per monitor for the LCD. As might be expected, acidification
impacts are greatest in the use stage for both monitor types, due to the emissions of SOX and NOX
from U.S. power plants. Use stage impacts are more dominant for the CRT (65% of life-cycle
acidification impacts) than the LCD (43%) due to the relatively large amount of power
consumed during use by the less energy-efficient CRT.
Arirlifiratirm
-: x 5.000 -
> c
'5 =
of
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3.3 BASELINE LCIA RESULTS
Table 3-31. Top 99% of the CRT acidification impact score
Life-cycle stage
Use
Use
Manufacturing
Manufacturing
Materials processing
Use
Manufacturing
Manufacturing
Materials processing
Manufacturing
Manufacturing
Use
Materials processing
Materials processing
Manufacturing
Materials processing
Manufacturing
Process group
U.S. electric grid
U.S. electric grid
LPG production
LPG production
Invar
U.S. electric grid
Japanese electric grid
U.S. electric grid
Steel production, cold-
rolled, semi-finished
CRT glass/frit
manufacturing
Japanese electric grid
U.S. electric grid
Aluminum production
Polycarbonate production
U.S. electric grid
Polycarbonate production
LPG production
Material
Sulfur dioxide
Nitrogen oxides
Sulfur oxides
Nitrogen oxides
Sulfur dioxide
Hydrochloric acid
Sulfur dioxide
Sulfur dioxide
Sulfur dioxide
Nitrogen oxides
Nitrogen oxides
Hydrofluoric acid
Sulfur dioxide
Nitrogen dioxide
Nitrogen oxides
Sulfur dioxide
Nitrous oxide
LCI data
type
Model/secondary
Model/secondary
Secondary
Secondary
Secondary
Model/secondary
Secondary
Model/secondary
Secondary
Primary
Model/secondary
Model/secondary
Secondary
Secondary
Model/secondary
Secondary
Secondary
Contribution
to impact
score*
47%
16%
15%
7.6%
4.8%
1.8%
1.6%
0.76%
0.73%
0.59%
0.54%
0.41%
0.40%
0.26%
0.25%
0.23%
0.22%
*Corumn may not add to 99% due to rounding.
3.3.8.2 Major contributors to the LCD acidification impact results
Table 3-32 lists the materials responsible for the top 99% of the LCD acidification impact
results and the LCI data type. Sulfur dioxide emissions from the U.S. electric grid during the use
stage are the greatest contributor at 31%, followed by NOX from natural gas production in the
materials processing stage. The latter process produces natural gas used by one LCD
monitor/module manufacturer as an ancillary material, indicating the LCD monitor/module
manufacturing process group is ultimately responsible for this contribution to the impact score.
However, as noted previously, only one LCD monitor/module manufacturer reported the
ancillary use of LNG. Other LCD monitor/module manufacturers reported using LNG as a fuel,
but not as an ancillary material. NOX, ammonia, hydrofluoric acid, and hydrochloric acid
emissions from LCD monitor/module manufacturing contribute another 22% of the LCD
acidification impact score. LCD monitor/module manufacturing data were collected directly by
the CDP from manufacturers in Asia.
NOX emissions from the U.S. electric grid during the use stage, and SOX and NOX
emissions from the Japanese electric grid during manufacturing are also among the top
contributors to the LCD acidification results. LCI data for these process groups were developed
by the CDP from secondary sources.
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3.3 BASELINE LCIA RESULTS
Table 3-32. Top 99% to the LCD acidification impact score
Life-cycle stage
Use
Materials processing
Manufacturing
Use
Manufacturing
Manufacturing
Manufacturing
Manufacturing
Manufacturing
Manufacturing
Use
Manufacturing
Materials processing
Materials processing
Manufacturing
Materials processing
Materials processing
Manufacturing
Use
Process group
U.S. electric grid
Natural gas prod.
LCD monitor/module mfg.
U.S. electric grid
Japanese electric grid
LCD monitor/module mfg.
Japanese electric grid
LCD monitor/module mfg.
LCD monitor/module mfg.
LPG production
U.S. electric grid
LCD backlight
Natural gas production
Natural gas production
LPG production
Steel production, cold-rolled,
semi-finished
PMMA sheet production
Natural gas production
U.S. electric gird
Material
Sulfur dioxide
Nitrogen oxides
Nitrogen oxides
Nitrogen oxides
Sulfur dioxide
Ammonia
Nitrogen oxides
Hydrofluoric acid
Hydrochloric acid
Sulfur oxides
Hydrochloric acid
Nitrogen oxides
Ammonia
Sulfur oxides
Nitrogen oxides
Sulfur oxides
Sulfur oxides
Nitrogen oxides
Hydrofluoric acid
LCI data
type
Model/secondary
Secondary
Primary
Model/secondary
Model/secondary
Primary
Model/secondary
Primary
Primary
Secondary
Model/secondary
Primary
Secondary
Secondary
Secondary
Secondary
Secondary
Secondary
Model/secondary
Contribution
to impact
score*
31%
15%
13%
10%
9.8%
4.0%
3.2%
2.8%
1.8%
1.3%
1.2%
0.70%
0.69%
0.65%
0.65%
0.64%
0.44%
0.35%
0.27%
*Corumn may not add to 99% due to rounding.
3.3.8.3 Limitations and uncertainties
Acidification impact characterization is a function of the mass of an acid-forming
chemical emitted to air and the acidification potential (AP) equivalency factor for that chemical.
The AP equivalency factor is the number of hydrogen ions that can theoretically be formed per
mass unit of the pollutant being released compared to SO2. This is a full equivalency approach
to impact characterization where all substances are addressed in a unified, technical model,
which lends more certainty to the characterization results than partial equivalency factors
discussed with regard to photochemical smog (Section 3.3.7).
For the CRT, and less so for the LCD, impact results are being driven primarily by SO2
and NOX emissions from U.S. power plants during use of the monitor by the consumer. As
discussed in Section 3.3.5 and noted above, the U.S. and Japanese electric grid inventories were
developed by the CDP from secondary sources. U.S. electric grid emissions of the criteria
pollutants, including SO2 and NOX, are based on data in the EPA publication, National Air
Quality and Emissions Trends Report, 1997 (EPA, 1998), which were the best data available
when the electric grid inventory data was developed and are expected to be reasonably accurate.
However, the Japanese electric grid inventory was derived from the U.S. inventory based on the
mix of fuels used in Japan. Because Japanese power plants may employ different pollution
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3.3 BASELINE LCIA RESULTS
control devices, use fuels of different quality, or other factors, their emissions could actually be
higher or lower than those reported in the inventory.
LCI data for many of the other primary contributors to the CRT acidification impact
category are from existing LCI databases. The limitations and uncertainties associated with
these data have been discussed extensively in other subsections of this chapter and pertain here.
On the other hand, LCI data for many of the other primary contributors to the LCD acidification
indicator results were collected directly by the CDP from manufacturers in Asia. These data are
considered to be of better quality since they were collected to meet the goals, objectives and
temporal and spatial boundaries of the CDP.
3.3.9 Air Particulates
Figure 3-12 presents the CRT and LCD LCIA results for the air particulates impact
category by life-cycle stage, based on the impact assessment methodology presented in Section
3.1.2.8. Tables M-21 and M-22 in Appendix M list complete air parti culates results for the CRT
and LCD, respectively.
0.160 n
.*;
§ 0.120-
c 0.080 -
o
o 0.040 -
c
it 0 000
Ul
-0.040 -
Particulates B Upstream
• Mfg
0.128 °'134 DUse
0.092 D EuL
0.058 I
0.014 °'022
| 1
I ' |
CRT -0019 LCD -°-012
Monitor type
Figure 3-12. Particulates impacts by life-cycle stage
The life-cycle air particulates indicator is 0.30 kg of air particulates per monitor for the
CRT and 0.115 kg of air particulates per monitor for the LCD. Recall from Section 3.1.2.8 that
air particulates impact results are ideally based on release amounts of particulate matter with
average aerodynamic diameter less than 10 micrometers (PM10) to the air. This is the size of
particulate matter that is most damaging to the respiratory system. However, as will be shown
later in this section, a significant portion of the particulate emissions data for both monitor types
do not specify a particulate size. This makes it more difficult to draw conclusions about the
relative life-cycle air particulate impacts of the CRT and LCD.
The manufacturing and upstream materials processing stages have almost equal
contribution to CRT air particulate impacts, at 45% of the total for the manufacturing stage and
43% of the total for the upstream stages. LCD impacts, on the other hand, are dominated by
particulate emissions during the upstream, materials processing stages, which contribute 80% of
the total score. Both technologies receive a substantial reduction in life-cycle air particulate
3-62
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3.3 BASELINE LCIA RESULTS
impacts at EOL due to an energy credit from incineration with energy recovery. The energy
credit, which is from incineration with energy recovery, is applied to electric power production
where it offsets some particulate emissions that would otherwise occur from electrical power
production.
3.3.9.1 Major contributors to the CRT air particulates impact results
Table 3-33 lists the materials that contribute to the top 99% of the CRT air particulates
impact score and their LCI data type. PM emissions from LPG production are the single largest
contributor to the overall score, at 43% of the total. This LPG is primarily an energy source in
CRT glass manufacturing, indicating the glass/frit process group is the ultimate source of these
air particulate emissions. As noted previously, CRT glass energy inputs are the subject of a
sensitivity analysis, discussed in Section 3.4.
Other major contributors to the CRT air particulates impact results are PM emissions
from the steel production process group, PM10 emissions from the U.S. electric grid during the
use stage, and PM emissions from aluminum production processes. Note that the inventories for
steel and aluminum production combine data from the raw materials extraction, materials
manufacture, and electricity generation processes. The PM emissions reported for the material
production process group could be from any one of these individual processes, but particulate
matter emissions are most often associated with combustion processes.
Table 3-33. Top 99% of the CRT air particulates impact score
Life-cycle stage
Manufacturing
Materials processing
Use
Materials processing
Process group
LPG production
Steel production, cold-rolled,
semi-finished
U.S. electric grid
Aluminum production
Material
PM
PM
PM-10
PM
LCI data
type
Secondary
Secondary
Model/secondary
Secondary
Contribution to
impact score*
43%
35%
19%
3.0%
*Column adds to greater than 99% due to an offset of emissions from incineration with energy recovery at EOL.
As shown in Table 3-33, the impact scores associated with the LPG, steel, and aluminum
production process groups—82% of CRT air particulates impacts—are based on emissions of
PM instead of emissions of PM10. This could be a matter of different terminology used in the
secondary data sets for these process groups (that is, PM is used to represent PM10), or it could
represent a broader class of particulate emissions, of which PM10 emissions would be a subset. If
the latter case is true, it is likely that CRT air particulate impacts are overstated.
3.3.9.2 Major contributors to the LCD air particulates impact results
Table 3-34 lists the materials that contribute to the top 99% of the LCD air particulates
impact score and their LCI data type. PM emissions from steel production are the largest
contributor to the overall score, followed by PM emissions from natural gas production. Natural
gas from this process supplies the LNG used as an ancillary material by one LCD
monitor/module manufacturer.
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3.3 BASELINE LCIA RESULTS
Other major contributors to the LCD air participates impact results are PM10 emissions
from the U.S. electric grid during the use stage and from the Japanese electric grid during
manufacturing, and PM emissions from LPG production. LPG from the latter process supplies
energy to the LCD glass manufacturing process.
Table 3-34. Top 99% of the LCD air particulates impact score
Life-cycle stage
Materials processing
Materials processing
Use
Manufacturing
Manufacturing
Process group
Steel production, cold-rolled,
semi-finished
Natural gas production
U.S. electric grid
Japanese electric grid
LPG production
Material
PM
PM
PM-10
PM-10
PM
LCI data
type
Secondary
Secondary
Model/secondary
Model/secondary
Secondary
Contribution to
impact score*
45%
25%
19%
5.9%
5.4%
*Column adds to greater than 99% due to an offset of emissions from incineration with energy recovery at EOL.
As shown in Table 3-34, the impact scores associated with the steel, natural gas, and LPG
production process groups—roughly 75% of LCD air particulates impacts—are based on
emissions of PM instead of emissions of PM10. As with the CRT, air particulate impacts should
be based on PM10 emissions, indicating LCD air paniculate impacts may be overstated.
3.3.9.3 Limitations and uncertainties
The CDP LCIA methodology for air particulates is based on emissions of PM10to air,
which is the size of parti culate matter that is most damaging to the respiratory system. However,
as noted in Tables 3-33 and 3-34, the majority of the CRT and LCD impacts were calculated
from emissions of "PM" rather than PM10. This could be a matter of different terminology used
in the secondary data sets for these process groups, or it could represent a broader class of
parti culate emissions, of which PM10 emissions would be a subset. If the latter case is true, it is
likely that both the CRT and LCD air particulate impacts are overstated.
The LCI data for all of the major contributors to both the CRT and LCD were either
developed by the CDP from secondary sources (e.g., the U.S. and Japanese electric grids) or are
from secondary LCI data sets (e.g., the fuel and upstream materials production processes). The
limitations and uncertainties associated with these data have been discussed in other subsections
of this chapter and pertain here. Note that U.S. electric grid emissions of the criteria pollutant
PM10 are based on data in the EPA publication, National Air Quality and Emissions Trends
Report, 1997 (EPA, December, 1998, EPA/454/R-98-016), and are expected to be reasonably
accurate.
Finally, the amount of LPG used to produce CRT glass, which is ultimately driving the
CRT air particulates results, is also uncertain due to the large variability in CRT glass energy
inputs received from glass manufacturers. See Section 3.4 for a sensitivity analysis of CRT glass
energy inputs.
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3.3 BASELINE LCIA RESULTS
3.3.10 Water Eutrophication
Figure 3-13 presents the CRT and LCD LCIA results for the water eutrophication impact
category by life-cycle stage, based on the impact assessment methodology presented in Section
3.1.2.9. Tables M-23 and M-24 in Appendix M are complete results for the CRT and LCD,
respectively.
-= 5.00E-02 n
>
'= s 4.00E-02
v c
% .f 3.00E-02
jS = 2.00E-02
Q.
w t3 1 .OOE-02
o c
•5 3 n nnp+nn
5* -1. OOE-02
7.22E-04
176E-02
1
Eutrophication
0 6.10E-04
4.90E-0;
Q Upstream
? BMfg
Q Use
DEOL
0
-1.10E-04 ' TK-iizrv;
CRT LCD -7.51 E-05
Monitor type
Figure 3-13. Eutrophication impacts by life-cycle stage
The life-cycle water eutrophi cation indicators are 0.048 kg of phosphate equivalents for
the CRT and 0.050 kg of phosphate equivalents for the LCD. Results for both the CRT and LCD
are completely dominated by emissions from the manufacturing stage, which accounts for 99%
of the indicator for both technologies. Both technologies have negative scores at the end-of-life
due to incineration with energy recovery. The energy recovery offsets some of the water
emissions from the electricity generation inventory included in the incineration data set.
3.3.10.1 Major contributors to the CRT water eutrophication impact results
Table 3-35 lists the materials that contribute to the top 99% of the CRT water
eutrophication results. Together, chemical oxygen demand (COD) and ammonia ions from the
LPG production process group account for about 91% of the total score. Most of the LPG from
this process is used as an energy source in CRT glass manufacturing (see Section 3.4 for the
sensitivity analysis of CRT glass energy inputs). Emissions of nitrogen, COD and phosphorus
from the CRT tube manufacturing process group contribute about seven percent of the CRT
water eutrophication impacts. COD and other nitrogen emissions from steel production are the
remaining top contributors to the CRT eutrophication score. LPG and steel production data are
from secondary sources, while the CRT tube manufacturing outputs are primary data collected
by the CDP.
3-65
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3.3 BASELINE LCIA RESULTS
Table 3-35. Top 99% of the CRT water eutrophication impact score
Life-cycle stage
Manufacturing
Manufacturing
Manufacturing
Materials processing
Materials processing
Manufacturing
Manufacturing
Process group
LPG production
LPG production
CRT tube manufacturing
Steel production, cold-rolled,
semi-finished
Steel production, cold-rolled,
semi-finished
CRT tube manufacturing
CRT tube manufacturing
Material
COD
Ammonia ions
Nitrogen
Other nitrogen
COD
COD
Phosphorus (yellow
or white)
LCI data
type
Secondary
Secondary
Primary
Secondary
Secondary
Primary
Primary
Contribution to
impact score*
72%
19%
6.3%
0.37%
0.33%
0.33%
0.32%
*Corumn may not add to 99% due to rounding.
3.3.10.2 Major contributors to the LCD water eutrophication impact results
Table 3-36 lists the materials that contribute to the top 99% of the LCD water
eutrophication results. Like the CRT, the LCD water eutrophication indicator is driven by
emissions from a single process group, in this case, LCD monitor/module manufacturing.
Together, emissions of nitrogen and phosphorus from that process account for 94% of the total
score. The LPG production process is the next largest contributor to the LCD water
eutrophication score, where water releases of COD and ammonia ions account for more than 4%
of the total.
Table 3-36. Top 99% to the LCD water eutrophication impact score
Life-cycle stage
Manufacturing
Manufacturing
Manufacturing
Manufacturing
Manufacturing
Materials processing
Process group
LCD monitor/module mfg.
LCD monitor/module mfg.
LPG production
LPG production
LCD panel components
PMMA sheet production
Material
Nitrogen
Phosphorus (yellow or white)
COD
Ammonia ions
Phosphorus (yellow or white)
Ammonia
LCI data
type
Primary
Primary
Secondary
Secondary
Primary
Secondary
Contribution
to impact
score*
67%
27%
3.4%
0.88%
0.48%
0.40%
*Column may not add to 99% due to rounding.
3.3.10.3 Limitations and uncertainties
Eutrophication (nutrient enrichment) impacts are calculated from the mass of a chemical
released directly to surface water and the chemical's eutrophication potential (EP). The EP is a
partial equivalency factor derived from the ratio of nitrogen and phosphorus in the average
composition of algae compared to the reference compound phosphate (see Section 3.1.2.9). As a
partial equivalency approach, only a subset of substances can be converted into equivalency
3-66
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3.3 BASELINE LCIA RESULTS
factors, which is a limitation of this LCIA methodology. However, the methodology does take
into account nitrogen and phosphorus, which are the two major limiting nutrients of importance
to eutrophication.
CRT water eutrophication results are dominated by LCI data from secondary sources, and
are therefore subject to the limitations and uncertainties associated with secondary data.
Furthermore, these results are ultimately due to the large amount of LPG reported to be used as a
fuel in LPG glass production. Because of the large degree of variability in glass energy data
received from three CRT glass manufacturers, CRT glass energy inputs are also uncertain and
the subject of a sensitivity analysis (see Section 3.4). LCD results, on the other hand, are driven
almost entirely by primary LCI data from the manufacturing life-cycle stage, which were
collected to meet the goals, objectives, and temporal and geographic boundaries of the CDP and
are therefore considered to be of better quality.
3.3.11 Water Quality
3.3.11.1 Biological oxygen demand (BOD)
Figure 3-14 presents the CRT and LCD LCIA results for the BOD water quality impacts
category by life-cycle stage, based on the impact assessment methodology presented in Section
3.1.2.10. Complete results are listed in Tables M-25 (CRT) and M-26 (LCD) in Appendix M.
2.00E-01 n
.*;
§ 1.50E-01 •]
c 1.OOE-01 -I
O
tj 5.00E-02 -
c
3
1.95E-01
,
O)
100E+00
-5.00E-02 J
3.93E-04
O.OOE+00 7.72E-04
-4.65E-04
CRT
2.79E-02
O.OOE+00
LCD
Monitor type
Figure 3-14. BOD impacts by life-cycle stage
-3.18E-04
During the life-cycle of a 17" CRT monitor, 0.195 kg of BOD are released to surface
water. The life-cycle of a functionally equivalent 15" LCD results in 0.0283 kg of BOD surface
water releases. As shown in Figure 3-14, BOD impacts for both monitor types are driven by
surface water releases in the manufacturing stage, which contribute 100% of CRT impacts and
99% of LCD impacts. Note that small BOD impacts also occur in the upstream, materials
processing life-cycle stage for both monitor types. These are almost entirely offset by negative
BOD values at end of life due to the offset of electric grid emissions when the monitors are
incinerated with energy recovery. Note also that there are no BOD emissions from the U.S.
electric grid during the use stage. The incineration inventory is a secondary data set that
3-67
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3.3 BASELINE LCIA RESULTS
contains a different electric grid inventory than the U.S. electric grid inventory developed by the
CDP.
Table 3-37 lists the materials responsible for the top 99% of the CRT BOD impacts.
CRT impacts in this category are driven by BOD releases from the LPG production process,
most of which is used to make LPG employed as fuel in CRT glass manufacturing. BOD
releases from CRT tube manufacturing also contribute a small percentage to the total score.
Table 3-37. Top 99% of the CRT BOD impact score
Life-cycle stage
Manufacturing
Manufacturing
Process group
LPG production
CRT tube manufacturing
Material
BOD
BOD
LCI data
type
Secondary
Primary
Contribution to
impact score
96%
3.3%
Table 3-38 lists the materials that contribute to the top 99% of the LCD BOD impacts. As
shown in the table, LCD impacts are slightly more distributed among processes than CRT
impacts, with BOD releases from four processes or process groups making up the list of top
contributors. Note that BOD releases from LPG production (most of which is used to make LPG
for LCD glass manufacturing) are much less for the LCD than the CRT, even though the LCD
glass manufacturing inventory was derived from the CRT glass manufacturing inventory. This is
because the CRT contains approximately ten times more glass than the LCD.
Table 3-38. Top 99% of the LCD BOD impact score
Life-cycle stage
Manufacturing
Manufacturing
Manufacturing
Materials processing
Process group
LCD monitor/module mfg.
LPG production
LCD panel components
Natural gas production
Material
BOD
BOD
BOD
BOD
LCI data
type
Primary
Secondary
Primary
Secondary
Contribution to
impact score
61%
32%
4.7%
0.99%
3.3.11.2 Total suspended solids (TSS^)
Figure 3-15 presents the CRT and LCD LCIA results for the TSS water quality impacts
category by life-cycle stage, based on the impact assessment methodology presented in Section
3.1.2.10. Tables M-27 and M-28 in Appendix M list complete results for the CRT and LCD,
respectively.
The life-cycle TSS impact indicator is 0.874 kg of TSS for the CRT and 0.0615 kg of
TSS for the LCD. TSS impacts for both monitor types are driven by the manufacturing stage,
where 99 and 94% of impacts occur for the CRT and LCD, respectively. TSS impacts also occur
in the upstream, materials processing life-cycle stage for both monitor types. Both technologies
receive a credit on TSS impacts at EOL due to an offset of electric grid emissions when the
monitors are incinerated with energy recovery.
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3.3 BASELINE LCIA RESULTS
*J 1 .OOE+00 n
3 8.00E-01 -
.2 4.00E-01 -
c 2.00E-01 -
5 n OOF+OO
•* -2.00E-01 -
TSS Q Upstream
• Mfg
8.69E-01 DUse
QEOL
5.80E-02
7.72E-03 1 o. OOE+00 4.98E-03 0. OOE+00
-2 11E-03 -1.44E-03
CRT LCD
Monitor type
Figure 3-15. TSS impacts by life-cycle stage
Table 3-39 presents the major contributors to the CRT TSS indicator and lists the LCI
data type. As with many other impact categories, the LPG production process is the single
largest contributor to the CRT TSS indicator, accounting for 97% of the total score. Most of the
LPG from this process is used as a fuel to produce CRT glass, but CRT energy inputs are
uncertain and evaluated in a sensitivity analysis in Section 3.4. TSS surface water releases from
the CRT glass/frit process group, CRT tube manufacturing, and fuel oil #6 production are also
top contributors to the CRT TSS score. However, the contribution of these processes or process
groups is small compared to that of the LPG production process.
Table 3-39. Top 99% of the CRT TSS impact score
Life-cycle stage
Manufacturing
Manufacturing
Manufacturing
Manufacturing
Process group
LPG production
CRT glass/frit mfg.
CRT tube manufacturing
Fuel oil # 6 production
Material
Suspended solids
Suspended solids
Suspended solids
Suspended solids
LCI data
type
Secondary
Primary
Primary
Secondary
Contribution to
impact score
97%
0.83%
0.53%
0.33%
Table 3-40 presents the top contributors to the LCD TSS impact score. Like the CRT
results discussed above, TSS surface water releases from the LPG production process are
responsible for the majority of LCD TSS impacts. LPG from this production process is used to
produce LCD glass. Note that the actual mass of TSS releases from the LCD-related process is
much smaller than those from the CRT-related process. This is because the LCD only uses about
10% as much glass as the CRT. TSS releases from the LCD monitor/module process group also
account for a sizeable percentage of LCD TSS impacts.
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3.3 BASELINE LCIA RESULTS
Table 3-40. Top 99% of the LCD TSS impact score
Life-cycle stage
Manufacturing
Manufacturing
Materials processing
Materials processing
Materials processing
Materials processing
Manufacturing
Process group
LPG production
LCD monitor/module mfg.
PMMA sheet production
Natural gas production
Steel production, cold-rolled,
semi-finished
Aluminum production
(all virgin)
LCD panel components
Material
Suspended solids
Suspended solids
Suspended solids
Suspended solids
Suspended solids
Suspended solids
Suspended solids
LCI data
type
Secondary
Primary
Secondary
Secondary
Secondary
Secondary
Primary
Contribution to
impact score*
66%
25%
2.2%
2.0%
1.6%
1.1%
1.0%
*Corumn may not add to 99% due to rounding.
Limitations and uncertainties
Both BOD and TSS indicators are calculated using a loading approach (i.e., the impact
score is based on the inventory amounts) and are therefore highly sensitive to inventory data
quality. CRT impact results are driven almost entirely by the LPG production inventory (a
secondary data set) and are therefore subject to the limitations and uncertainties associated with
secondary data. In particular, see Section 3.3.2.3 for a detailed discussion of LPG production
data quality. In addition, note that LPG production impacts are almost all due to the large
amount of LPG reported to be used as a fuel in CRT glass manufacturing. As note previously,
CRT glass energy inputs are uncertain and are evaluated in a sensitivity analysis (see
Section 3.4).
LCD impact results, on the other hand, are driven by LCI data from both primary and
secondary sources and are therefore considered to be of somewhat better quality than the CRT
results. However, a significant percentage of LCD water quality impacts also come from the
large amount of LPG used as a fuel input to LCD glass manufacturing. These energy inputs are
also uncertain and are evaluated in the sensitivity analysis in Section 3.4.
3.3.12 Radioactivity
Figure 3-16 presents the CRT and LCD LCIA results for the radioactivity impact
category by life-cycle stage, based on the impact assessment methodology presented in Section
3.1.2.11. Complete CRT and LCD results are presented in Tables M-29 and M-30 in Appendix
M, respectively.
The life-cycle radioactivity indicator is 38.5 million Bequerels (Bq) for the CRT and 12.2
million Bq for the LCD. Radioactivity impacts are driven by radioactive emissions from the
upstream, materials processing stage for both monitor types, which contributes 99% of CRT life-
cycle impacts and 98% of LCD life-cycle impacts. This result was unforeseen, since one might
expect the majority of radioactive emissions to occur from the use stage, due to electricity
generation at nuclear power plants. As it turns out, radioactivity impacts are being driven by data
for nuclear fuel reprocessing that are included in the electric grid inventories for the steel, invar
(an alloy of nickel and ferrite), and ferrite production process groups.
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3.3 BASELINE LCIA RESULTS
Radioactivity
:| 40,000,000 n
•5 30,000,000 -
c
.2 20,000,000 -
tj
§ 10,000,000-
38,000,000
12,000,000
35,000 436<00° 41
92.2 163'°°° 29
CRT
LCD
Monitor type
Figure 3-16. Radioactivity impacts by life-cycle stage
The LCIs for steel, invar, and ferrite were obtained from two databases developed by the
former Ecobilan Group, an LC A consulting firm that was previously headquartered in France
(see Section 2.2.1.1 for a discussion of how these databases were selected). Per Ecobilan, the
ferrite inventory contains older data that may include radioactive emissions from electricity use.
For the steel and nickel inventories, the source of both is site data in Europe, with the radioactive
emissions coming from electricity in Europe, where nuclear fuel is reprocessed. In fact, the
electricity data are from France for both materials, and France is one of the few countries
(including Japan and the United Kingdom) that reprocesses nuclear fuel (Glazebrook, 2001).
Therefore, the radioactivity impacts calculated from these inventories are more representative of
impacts from countries that reprocess nuclear fuel than impacts from countries that do not.
To further illustrate this point, Tables 3-41 and 3-42 lists the materials and process
groups that contribute to the top 99% of the CRT and LCD radioactivity indicator results,
respectively. As shown in the tables, radioactivity impacts for both monitor types are driven by
releases of plutonium-241 from steel (both monitor types), invar (CRT), and ferrite (CRT)
production. Plutonium-241 is a byproduct of fuel reprocessing. Xenon -133 releases from the
U.S. electric grid contribute slightly to the LCD radioactivity impacts and to a lesser degree to
the CRT total impacts. Note that the actual amount of radioactivity from Xenon-133 is greater
for the CRT than the LCD, but contributes a smaller percent of total impacts.
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3.3 BASELINE LCIA RESULTS
Table 3-41. Top 99% of the CRT radioactivity impact score
Life-cycle stage
Materials processing
Materials processing
Materials processing
Use
Materials processing
Materials processing
Process group
Steel production, cold-
rolled, semi-finished
Invar
Ferrite
U.S. electric grid
Steel production, cold-
rolled, semi-finished
Steel production, cold-
rolled, semi-finished
Material
Plutonium-241 (isotope)
Plutonium-241 (isotope)
Plutonium-241 (isotope)
Xenon-133 (isotope)
Plutonium-240 (isotope)
Cesium-135 (isotope)
LCI data
type
Secondary
Secondary
Secondary
Model/secondary
Secondary
Secondary
Contribution
to impact
score*
62%
18%
17%
0.81%
0.27%
0.24%
*Corumn may not add to 99% due to rounding.
Table 3-42. Top 99% of the LCD radioactivity impact score
Life-cycle stage
Materials processing
Use
Manufacturing
Materials processing
Materials processing
Process group
Steel production, cold-
rolled, semi-finished
U.S. electric grid
Japanese electric grid
Steel production, cold-
rolled, semi-finished
Steel production, cold-
rolled, semi-finished
Material
Plutonium-241 (isotope)
Xenon-133 (isotope)
Xenon-133M (isotope)
Plutonium-240 (isotope)
Cesium-135 (isotope)
LCI data
type
Secondary
Model/secondary
Secondary
Secondary
Secondary
Contribution
to impact
score*
96%
0.95%
0.54%
0.42%
0.38%
*Column may not add to 99% due to rounding.
Most of the radioactivity impacts are based on LCI data from secondary sources and are
therefore subject to the limitations and uncertainties in secondary data, discussed previously. In
addition, because radioactivity impacts are being driven by radioactive emissions from fuel
reprocessing in France, they may not be representative of radioactivity impacts elsewhere.
However, most of the CRT and LCD primary manufacturing data were collected from companies
in Japan, where fuel reprocessing also occurs. For example, if Japanese CRT and LCD monitor
and/or components manufacturers purchase steel from Japanese steel mills, the radioactivity
emissions from electricity used to manufacture the steel could be similar. Japan ranked second
in worldwide steel production in 2000 behind Mainland China, and third in 1999 behind
Mainland China and the United States (IISI, 2001).
Note that the Japanese electric grid, which is linked to CRT and LCD production
inventories, was developed from the U.S. electric grid inventory and therefore does not account
for radioactive emissions from fuel reprocessing. This means that radioactive impacts from
Japanese manufacturing processes that consume electricity are understated. For example,
electricity used in the CRT glass/frit process group was the ninth largest contributor to the CRT
energy use score, but the inventory for this process group does not account for fuel reprocessing
emissions.
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3.3 BASELINE LCIA RESULTS
3.3.13 Potential Human Health Impacts
As discussed in Section 3.1.2.12, human health impacts included in the scope of this
LCA are chronic (repeated dose) effects, including non-carcinogenic and carcinogenic effects to
both workers and the public, and aesthetics. (Although not a health effect per se, aesthetics
pertains to human welfare.)
Chronic health effect (cancer and noncancer) impacts are calculated using the scoring of
inherent properties approach where an impact score is based on the inventory amount weighed
by a hazard value (HV). The HV represents the chronic toxicity of a specific material (see Table
K-8 in Appendix K for a list of toxicity values used to calculate hazard values). In this manner
the inventory amount (the toxic chemical input amount for occupational health effects, and the
output amount for public health effects) is used as a surrogate for exposure, while the hazard
value represents the inherent toxicity of the chemical for chronic exposure.
The CDP human health effects LCIA methodology does not consider the fate and
transport of a toxic chemical in the environment, nor does it evaluate the potential for actual
exposures to occur. LCI data do not have the temporal and spatial specificity needed to estimate
potential dose rates, for example, nor do they contain information on engineering controls used
in an occupational setting to reduce exposure. [It should be noted that more sophisticated
models for evaluating human health effects in an LCA framework are being developed that use a
multimedia fate, multi-pathway human exposure, and toxicological potency approach (Bare,
1999). However, such models are less comprehensive in terms of the number of chemicals for
which there are data.] The limitations and uncertainties in the health effects scores are discussed
further below, following the presentation of results.
3.3.13.1 Chronic occupational health effects
Figure 3-17 presents the CRT and LCD LCIA results by life-cycle stage for the chronic
occupational health effects impact category, based on the impact assessment methodology
presented in Section 3.1.2.12. Complete CRT and LCD results are presented in Tables M-31 and
M-32 in Appendix M.
•1 9.00E+02 n
re 6.00E+02 -
o
'•5 3.00E+02 -
c
Chronic occupational
9.00E+02
n Upstream
• Mfg
O)
O.OOE+00
0 -3.00E+02 -
7.32E-01
6
3.56E+01
-2.83E+00 3.59E-01
.84E+02
DEOL
1.33E+01
-1.94E+00
CRT LCD
Monitor type
Figure 3-17. Chronic occupational impacts by life-cycle stage
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3.3 BASELINE LCIA RESULTS
The life-cycle chronic occupational health effects indicator is 934 tox-kg per functional
unit for the CRT, and 696 tox-kg per functional unit for the LCD. As shown in the figure, the
total score is dominated by toxic chemical inputs to the manufacturing stage, which account for
98% and 96% of CRT and LCD impacts in this category, respectively. This result was expected
since inputs to the other life-cycle stages tend to be raw materials (e.g., ores, coal, etc., for the
materials processing and use life-cycle stages) or finished products (e.g., the monitors
themselves for the EOL stage) that are not classified as toxic materials (see Table K-9 in
Appendix K for a 1
list of materials excluded from the toxic classification). Both the CRT and LCD receive negative
chronic occupational health effects scores at end of life due to the offset of electric grid
emissions when the monitors are incinerated with energy recovery.
Table 3-43 lists the materials responsible for the top 99% of the CRT chronic
occupational health effects score and the LCI data type. LCI data for most of the top
contributors are primary data collected from manufacturers by the CDP. In general, these data
are expected to be of better quality (for the purposes of the CDP) than data from secondary
sources, since they were collected to meet the goals and scope of the CDP.
Table 3-43. Top 99% of the CRT chronic occupational health effects score
Life-cycle stage
Manufacturing
Manufacturing
Manufacturing
Use
Manufacturing
Use
Manufacturing
Process group
CRT glass/frit mfg.
PWB manufacturing
CRT tube manufacturing
U.S. electric grid
CRT glass/frit mfg.
U.S. electric grid
CRT tube manufacturing
Material
Liquified petroleum gas
Sulfuric acid
Sulfuric acid
Natural gas
Barium carbonate
Petroleum (in ground)
Fuel oil # 6
LCI data
type
Primary
Primary
Primary
Model/secondary
Primary
Model/secondary
Primary
Contribution
to impact
score*
75%
13%
4.1%
3.0%
1.8%
0.81%
0.79%
*Column may not add to 99% due to rounding.
LPG inputs to the glass/frit process group, primarily from CRT glass manufacturing,
contribute 75% of the CRT impacts in this category. The high impact score for LPG is mainly
due to the large amount of LPG inputs to the glass/frit process group (351 kg/functional unit),
which results in a high score when multiplied by the HV. No toxicity data were available for
LPG. Therefore, it was assigned default HVs of one for both cancer and noncancer effects (total
HV=2), representative of mean cancer and noncancer toxicity values. As noted previously, glass
manufacturing energy data are uncertain and therefore evaluated in a sensitivity analysis (see
Section 3.4).
Sulfuric acid used in PWB manufacturing is the next greatest contributor to the CRT
chronic occupational health effects results (13%) followed by sulfuric acid used in CRT tube
manufacturing (4.1%). The sulfuric acid HV is based on an inhalation NOAEL of 0.1 mg/m3,
which is significantly lower (and therefore more toxic) than the geometric mean inhalation
NOAEL of 68.7 mg/m3. Consequently, sulfuric acid impacts are driven more by its inherent
toxicity for noncancer effects than the input amounts (0.18 kg per functional unit for PWB
manufacturing and 0.056 kg per functional unit for CRT tube manufacturing). Sulfuric acid has
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3.3 BASELINE LCIA RESULTS
no cancer slope factor and an IARC weight of evidence (WOE) classification of 3 (not
classifiable for carcinogenicity), and therefore received an HV of zero for cancer effects.
Natural gas and petroleum used as fuels in the U.S. electric grid, barium carbonate used
in the CRT glass/frit process group and fuel oil #6 used to manufacture the CRT tube round out
the top contributors to the CRT chronic occupational health effects score. Barium carbonate has
no cancer slope factor and an EPA cancer WOE of D (not classifiable), and therefore has an HV
of zero for cancer effects. However, its oral NOAEL is 0.21 mg/kg-day compared to the
geometric mean oral NOAEL of 11.9 mg/kg-day, which results in an HV of 57 for noncancer
effects. Therefore, like sulfuric acid, the barium carbonate impacts are driven more by its
inherent toxicity than the input amount (0.297 kg per functional unit). No specific toxicity data
were available for natural gas, petroleum, or fuel oil #6; consequently they were assigned a
default HV of one for both cancer and noncancer effects (total HV=2).
Table 3-44 lists the materials that contribute to the top 99% of the LCD chronic
occupational health effects score. Like the CRT, LCI data for most of the top contributors are
primary data collected from manufacturers by the CDP, and are therefore expected to be of
generally better quality (for the purposes of the CDP) than data from secondary sources.
Table 3-44. Top 99% of the LCD chronic occupational health effects score
Life-cycle stage
Manufacturing
Manufacturing
Manufacturing
Manufacturing
Manufacturing
Manufacturing
Use
Manufacturing
Manufacturing
Process group
LCD monitor/module mfg.
LCD monitor/module mfg.
PWB manufacturing
LCD glass manufacturing
LCD monitor/module mfg.
LCD panel components
U.S. electric grid
LCD monitor/module mfg.
LCD monitor/module mfg.
Material
Liquified natural gas
Sulfuric acid
Sulfuric acid
Liquified petroleum gas
Phosphine
Sulfuric acid
Natural gas
Dimethylsulfoxide
Ethanolamine
LCI data
type
Primary
Primary
Primary
Primary
Primary
Primary
Model/secondary
Primary
Primary
Contribution to
impact score*
57%
23%
8.0%
4.7%
1.8%
1.6%
1.5%
1.1%
0.62%
*Column may not add to 99% due to rounding.
As shown in the table, LCD impacts in this category are dominated by LNG used in LCD
monitor/module manufacturing. The high impact score for LNG is primarily due to the large
amount of ancillary LNG inputs (194 kg/functional unit) in the LCD monitor/module
manufacturing inventory, which results in a high score when multiplied by the HV. No toxicity
data were available for LNG. Therefore, it was assigned a default, mean HV of one for both
cancer and noncancer effects (total HV=2). As noted previously, only one of seven LCD
module/monitor manufacturers reported using LNG as an ancillary material. Therefore, the total
score for LCD chronic occupational health effects may not be representative of the industry as a
whole. If we remove this application of LNG from the LCD inventory, the LCD occupational
health effects result is reduced by 58 percent, from 683 tox-kg per monitor to 288 tox-kg per
monitor. Note, however that other LCD monitor/module manufacturers did report using LNG as
a fuel.
Sulfuric acid used in three process groups (LCD module/monitor manufacturing, PWB
manufacturing, and LCD panel components) accounts for another 33% of the LCD chronic
occupational health effects score. As discussed above for the CRT, sulfuric acid has a relatively
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3.3 BASELINE LCIA RESULTS
low toxicity value, and therefore a high HV, which results in a high impact score for a small
input amount. The LCD module/monitor manufacturing process group has the highest impact
score for sulfuric acid because it has the greatest input amount (0.229 kg per functional unit).
The remaining top contributors to the LCD chronic occupational health effects score are
LPG used in LCD glass manufacturing; and phosphine, dimethylsulfoxide, and ethanolamine
used in LCD monitor/module manufacturing; and natural gas used as a fuel by the U.S. electric
grid. As discussed earlier, LCD glass energy inputs are uncertain and evaluated in a sensitivity
analysis in Section 3.4. The LPG score is based on default HVs (representative of the geometric
mean toxicity values) for both cancer and noncancer effects, since no toxicity data were
available for LPG.
The phosphine score is driven by its low oral NOAEL value (0.026 mg/kg-day), which is
significantly lower than the geometric mean value of 68.7 mg-kg-day. Thus, due to its
inherently high toxicity, a relatively small input of phosphine (in this case, 0.027 kg per
functional unit) results in a relatively high chronic occupational health effects score. No slope
factors or cancer WOE classifications were found for phosphine, indicating a default HV of one
was used, which is far outweighed by the non-cancer hazard value.
Dimethylsulfoxide is less toxic than phosphine (oral LOAEL =1.0 mg/kg-day), but has a
greater input amount (0.066 kg per functional unit). However, phosphine's greater toxicity
outweighs the greater input amount for dimethylsulfoxide, resulting in a higher impact score for
phosphine.
No specific toxicity data were available for natural gas; consequently it was assigned a
default HV of one for both cancer and noncancer effects (total HV=2).
3.3.13.2 Chronic public health effects
Figure 3-18 presents the CRT and LCD LCIA scores by life-cycle stage for the chronic
public health effects category, based on the impact assessment methodology presented in Section
3.1.2.12. Complete results are presented in Tables M-33 and M-34 in Appendix M, respectively.
The life-cycle chronic public health effects score is 1,980 tox-kg per functional unit for
the CRT and 902 tox-kg per functional unit for the LCD. As shown in the figure, the CRT score
is dominated by toxic chemical outputs from electricity generation in the use stage, which
§ 1.80E+03
"re
O 1.20E+03
o
i 6.00E+02
)
O
100E+00
Chronic public health
1.65E+03
2.28E+02
9.77E+01
6.17E+02
1.74E-01
2.35E+02
5.01 E+01
CRT
-6.30E-02
LCD
Monitor type
Figure 3-18. Chronic public health impacts by life-cycle stage
3-76
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3.3 BASELINE LCIA RESULTS
account for almost 84% of CRT impacts in this category. To a lesser degree, LCD chronic
public health effect impacts are also driven by emissions from electricity generation in the use
stage, which account for more than 68% of the total. Note that the ratio of CRT to LCD use
stage public health impacts is the same as the ratio of CRT to LCD use stage electricity
consumption (634 kWh/life for the CRT to 237 kWh/life for the LCD).
The materials processing stage contributes almost 12% of CRT chronic public health
effect impacts and almost six percent of LCD impacts. The manufacturing life-cycle stage is
responsible for five and 26% of CRT and LCD impacts in this category, respectively. Both
monitors receive very small public chronic health effects scores at end of life. This is because
most public health effect impacts from CRT and LCD recycling and disposal processes are offset
by a credit on electric grid emissions when the monitors are incinerated with energy recovery.
Table 3-45 presents the materials that contribute to the top 99% of the CRT chronic
public health effects score. As shown in the table, SO2 emissions from a number of different
process groups almost completely dominate CRT impacts in this category, accounting for more
than 98% of the total. All of the SO2 LCI data shown in the table are either from secondary data
sets not developed specifically for the CDP, or from the electric grid inventories developed from
secondary sources for this project. Sulfur dioxide has a relatively high HV based on an
inhalation NOAEL of 0.104 mg/m3, compared to the geometric mean inhalation NOAEL of 68.7
mg/m3. In addition, from a mass loading perspective, SO2 emissions were the second largest
contributor to CRT life-cycle air pollutant emissions, exceeded only by emissions of carbon
dioxide (CO2). Carbon dioxide is not classified as toxic, and therefore does not contribute to the
human health effects scores.
Table 3-45. Top 99% of the CRT chronic public health effects score
Life-cycle stage
Use
Materials processing
Manufacturing
Manufacturing
Materials processing
Materials processing
Materials processing
Manufacturing
Materials processing
Process group
U.S. electric grid
Invar
Japanese electric grid
U.S. electric grid
Steel production, cold-
rolled, semi-finished
Aluminum production
Polycarbonate production
LPG production
Lead production
Material
Sulfur dioxide
Sulfur dioxide
Sulfur dioxide
Sulfur dioxide
Sulfur dioxide
Sulfur dioxide
Sulfur dioxide
Carbon monoxide
Sulfur dioxide
LCI data
type
Model/secondary
Secondary
Model/secondary
Model/secondary
Secondary
Secondary
Secondary
Secondary
Secondary
Contribution to
impact score*
83%
8.3%
2.9%
1.3%
1.3%
0.70%
0.40%
0.29%
0.23%
*Column may not add to 99% due to rounding.
Most of the sulfur dioxide emissions that contribute to the CRT chronic public health
effects score are from the combustion of fossil fuels used to generate electricity. For example,
the electricity required to power the monitor during the use stage accounts for the vast majority
of SO2 emissions and 83% of the CRT chronic public health effects score. Sulfur dioxide
emissions from electricity consumed in the United States and Japan during the manufacturing
life-cycle stage account for another 4.2% of the total score. Much of the SO2 emissions reported
3-77
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3.3 BASELINE LCIA RESULTS
in secondary data sets for the materials processing life-cycle stage may also be from electricity
generation since many of these data also contain an electric grid inventory.
Table 3-46 lists the materials that contribute to the top 99% of the LCD chronic public
health effects score and the LCI data type. LCD impacts in this category are also dominated by
SO2 emissions, which are responsible for roughly 93% of impacts. Like the CRT, most of these
emissions occur from electricity generation, either during the use stage (68%) or manufacturing
(21%). As noted previously, SO2 has a relatively high HV due to its low toxicity value
(inhalation NOAEL = 0.104 mg/m3). Similar to the CRT, from a mass loading perspective, SO2
emissions were the second largest contributor to LCD life-cycle air pollutant emissions,
exceeded only by emissions of CO2.
Table 3-46. Top 99% of the LCD chronic public health effects score
Life-cycle stage
Use
Manufacturing
Manufacturing
Materials processing
Materials processing
Materials processing
Materials processing
Materials processing
Materials processing
Materials processing
Manufacturing
Manufacturing
Process group
U.S. electric grid
Japanese electric grid
LCD monitor/module mfg.
Steel production, cold-
rolled, semi-finished
PMMA sheet production
Natural gas production
Natural gas production
Aluminum production
Natural gas production
Polycarbonate production
LCD monitor/module mfg.
U.S. electric grid
Material
Sulfur dioxide
Sulfur dioxide
Phosphine
Sulfur dioxide
Sulfur dioxide
Methane
Benzene
Sulfur dioxide
Carbon monoxide
Sulfur dioxide
Phosphorus
(yellow or white)
Sulfur dioxide
LCI data
type
Model/secondary
Model/secondary
Primary
Secondary
Secondary
Secondary
Secondary
Secondary
Secondary
Secondary
Primary
Model/secondary
Contribution to
impact score*
68%
21%
3.2%
1.4%
0.96%
0.78%
0.59%
0.57%
0.53%
0.49%
0.38%
0.35%
*Column may not add to 99% due to rounding.
Other top contributors to the LCD chronic public health effects score include phosphine
and phosphorus from LCD monitor/module manufacturing, and methane, benzene, and carbon
monoxide from natural gas production. As noted above in the section on chronic occupational
health effects, the phosphine score is driven by its low oral NOAEL value (0.026 mg/kg-day),
which is significantly lower than the geometric mean value of 68.7 mg-kg-day, resulting in a
high HV. Thus, a relatively small output of phosphine (in this case, air emissions of 0.063 kg
per functional unit) results in a relatively high chronic public health effects score.
The benzene and phosphorus chronic health effects scores are also driven more by their
toxicity than the output amounts. Benzene is a known human carcinogen (EPA WOE Class A)
that also causes noncancer health effects. The HV for benzene is based on its oral slope factor
[0.055 (mg/kg-day)"1] and its inhalation NOAEL for noncancer effects (1.15 mg/m3), which
together result in a high HV. (Benzene also has an inhalation slope factor and an oral NOAEL
value, but these yield lower hazard values when compared to the geometric mean values.)
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3.3 BASELINE LCIA RESULTS
Phosphorus has an EPA WOE classification of D (not classifiable as to human carcinogenicity),
but has a low oral NOAEL value (0.015 mg/kg-day), which also gives it a high HV.
No toxicity data were available for methane. Therefore, it received a default HV of one
for both cancer and noncancer effects (HV=2 total). The HV for carbon monoxide is based on
an inhalation LOAEL of 55 mg/m3.
3.3.13.3 Chronic public health effect scores modified to exclude sulfur dioxide
Because the chronic public health effects scores for both the CRT and the LCD are
dominated by SO2 emissions, a secondary analysis was run to identify the top contributors to
public health impacts when SO2 emissions are excluded from the inventories. Results of this
analysis may be more useful to manufacturers seeking to identify problematic toxic chemicals
within their own manufacturing processes.
Figure 3-19 presents the CRT and LCD chronic public health effects scores by life-cycle
stage when SO2 emissions are excluded from the inventories. Under this scenario, the CRT
score is reduced almost 99% from 1980 tox-kg to 26 tox-kg per functional unit, and the LCD
score is reduced about 93% from 902 tox-kg to 61 tox-kg per functional unit. Note that these
scores should not be used to evaluate which monitor type has higher overall impacts in this
category, but they are useful for identifying life-cycle improvement opportunities that were
previously obscured by SO2 impacts.
Chronic public health (without SO2)
*- 60 0 n
c
3
c
o
•5 20 0
|
"5> oo
X
0 -20.0 J
40
20
1 5
c r*
6. 1 Q oy
1 1
n Upstream
• Mfg
DUse
DEOL
9 -3
-096
CRT LCD
Monitor type
Figure 3-19. Chronic public health im pacts (without SO2)
by life-cycle stage
With SO2 emissions removed from the inventories, chronic public health effect impacts
are highest in the manufacturing life-cycle stage for both the CRT (56% of impacts) and the
LCD (65% of impacts). The use stage is the next largest contributor for the CRT (22%), and the
materials processing stage in the next largest contributor for the LCD (32%). As will be shown
below, use stage impacts are significant for the CRT, even when SO2 emissions are excluded,
because of the CRT's relatively high electricity consumption during use by the consumer and the
associated emissions of pollutants from U.S. power plants.
Table 3-47 presents the materials that contribute greater than one percent of CRT impacts
when SO2 emissions are excluded from the CRT inventory. Under this scenario, CRT chronic
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3.3 BASELINE LCIA RESULTS
public health impacts are still being driven by emissions of criteria air pollutants,2 including
carbon monoxide, nitrogen oxides, and sulfur oxides (assuming that SO2 emissions comprise a
large part of the sulfur oxide emissions shown in the table). As shown in the table, emissions of
these three pollutants or pollutant categories are responsible for some 48% of CRT chronic
public health impacts when pure SO2 emissions are excluded from the CRT inventory. Note that
the majority of these emissions occur from the LPG production process, and most of this LPG is
used as a fuel in CRT glass manufacturing. CRT glass manufacturing energy inputs are
uncertain and evaluated in a sensitivity analysis (See Section 3.4). Other significant contributors
include arsenic from lead production, methane from LPG production and the U.S. electric grid
inventory, vanadium and benzene from LPG production, and titanium tetrachloride from
aluminum production.
Table 3-47. Materials contributing greater than 1% of the CRT chronic
public health effects score (without SO2)
Life-cycle stage
Manufacturing
Use
Materials processing
Manufacturing
Manufacturing
Use
Manufacturing
Use
Manufacturing
Manufacturing
Materials processing
Manufacturing
Use
Use
Materials processing
Process group
LPG production
U.S. electric grid
Lead
LPG production
LPG production
U.S. electric grid
LPG production
U.S. electric grid
LPG production
LPG production
Aluminum production
(virgin)
CRT glass/frit mfg.
U.S. electric grid
U.S. electric grid
Steel Prod., cold-rolled,
semi-finished
Material
Carbon monoxide
Nitrogen oxides
Arsenic
Methane
Sulfur oxides
Methane
Nitrogen oxides
Carbon monoxide
Vanadium
Benzene
Titanium tetrachloride
Fluorides (F-)
Arsenic
Hydrochloric acid
Carbon monoxide
LCI data
type
Secondary
Modeled/secondary
Secondary
Secondary
Secondary
Modeled/secondary
Secondary
Modeled/secondary
Secondary
Secondary
Secondary
Primary
Modeled/secondary
Modeled/secondary
Secondary
Contribution
to impact
score
22.35%
9.12%
8.55%
6.50%
6.21%
4.99%
4.44%
4.23%
4.05%
3.32%
2.79%
2.27%
2.16%
1.91%
1.16%
Table 3-48 presents the materials that contribute greater than one percent of LCD impacts
when SO2 emissions are excluded from the LCD inventory. Under this scenario, phosphine
emissions from LCD monitor/module manufacturing are the dominant factor in the LCD chronic
public health effects score, contributing 47% of the total. Other significant contributors include
methane, benzene, carbon monoxide, and nitrogen oxides from natural gas production, and
phosphorus, fluorides, tetramethyl ammonium hydroxide, and nitrogen oxides from LCD
monitor/module manufacturing. Recall that the LCD monitor/module manufacturing process
The criteria air pollutants are those for which U.S. National Ambient Air Quality Standards have been
adopted. They are carbon monoxide, lead, nitrogen oxides, ozone, paniculate matter, and sulfur dioxide.
3-80
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3.3 BASELINE LCIA RESULTS
consumes the majority of the natural gas made in the natural gas production process, where LNG
is used as an ancillary material. However, only one of the seven LCD monitor/module
manufacturers that provided inventory data to the CDP reported the ancillary use of LNG. Other
LCD monitor/module manufactures did report the use of LNG as a fuel.
Table 3-48. Materials contributing greater than 1% of the LCD chronic
public health effects score (without SO2)
Life-cycle stage
Manufacturing
Materials processing
Materials processing
Materials processing
Manufacturing
Manufacturing
Materials processing
Manufacturing
Manufacturing
Use
Process group
LCD monitor/module mfg.
Natural gas production
Natural gas production
Natural gas production
LCD monitor/module mfg.
LCD monitor/module mfg.
Natural gas production
LCD monitor/module mfg.
LCD monitor/module mfg.
U.S. electric grid
Material
Phosphine
Methane
Benzene
Carbon monoxide
Phosphorus (yellow or
white)
Fluorides (F-)
Nitrogen oxides
Tetramethyl
ammonium hydroxide
Nitrogen oxides
Nitrogen oxides
LCI data
type
Primary
Secondary
Secondary
Secondary
Primary
Primary
Secondary
Primary
Primary
Modeled/secondary
Contribution
to impact
score
46.7%
11.4%
8.61%
7.81%
5.56%
4.15%
2.12%
2.09%
1.78%
1.43%
3.3.13.4 Limitations and uncertainties: chronic human health effects
Most of the limitations and uncertainties in the chronic human health effects results
presented here can be grouped into three categories:
1. Structural or modeling limitations and uncertainties associated with the accuracy of the
toxic chemical classification method and the chemical scoring approach used to
characterize human health effects.
2. Toxicity data limitations and uncertainties associated with the availability and accuracy
of toxicity data to represent potential human health effects.
3. LCI data limitations and uncertainties associated with the accuracy and
representativeness of the inventory data.
Each of these are discussed below.
Structural or modeling limitations and uncertainty. The chemical scoring method used
in the human health effects impact characterization is a screening tool to identify chemicals of
potential concern, not to predict actual effects or characterize risk. A major limitation in the
method is that it only measures relative toxicity, combined with inventory amount. It does not
take chemical fate, transformation, or degradation into account. In addition, it uses a simple
surrogate value (i.e., inventory amount) to evaluate the potential for exposure, when actual
exposure potential involves many more factors, some of which are chemical-specific. Other
sources of uncertainty include possible omissions by the CDP researchers in the impact
classification process (e.g., potentially toxic chemicals not classified as such) or
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3.3 BASELINE LCIA RESULTS
misrepresentation of chemicals in the impact characterization method itself (e.g.,
misrepresenting a chemical as a small contributor to total impacts, because of missing or
inaccurate toxicity data). Some of these limitations and uncertainties may also be considered
limits in the toxicity data which are discussed further below.
It should also be noted, however, that because LCA involves analyzing many processes
over the entire life cycle of a product, a comprehensive, quantitative risk assessment of each
chemical input or output can not be done. Rather, LCA develops relative impacts that often lack
temporal or spatial specificity, but can be used to identify materials for more detailed evaluation.
More detailed assessments of the toxicity and potential exposures to selected materials are
performed in Chapter 4.
Toxicity data limitations and uncertainties. Major uncertainties in the impact assessment
for potentially toxic chemicals result from missing toxicity data and from limitations of the
available toxicity data. Uncertainties in the human health hazard data (as typically encountered
in a hazard assessment) include the following:
• Using dose-response data from laboratory animals to represent potential effects in
humans.
• Using data from homogeneous populations of laboratory animals or healthy human
populations to represent the potential effects on the general human populations, with a
wide range of sensitivities.
• Using dose-response data from high dose toxicity studies to represent potential effects
that may occur at low levels.
• Using data from short-term studies to represent the potential effects of long-term
exposures.
• Assuming a linear dose-response relationship.
• Possibly increased or decreased toxicity resulting from chemical interactions.
Regarding uncertainties resulting from missing toxicity data, there is uncertainty
associated with using a default HV (i.e., assuming average toxicity for that measure when a
chemical could be either more or less toxic than average). However, the use of neutral default
values for missing data reduces the bias that typically favors chemicals with little available
information. Use of a data-neutral default value to fill data gaps is consistent with principles for
chemical ranking and scoring (Swanson and Socha, 1997). Of the 273 chemicals classified as
potentially toxic in the CDP LCA, 156 (57%) had no toxicity data for carcinogenic effects and
128 (47%) had no data for noncarcinogenic effects. Ninety-seven chemicals (36%) had no
human health toxicity data whatsoever.
LCI data limitations and uncertainty. Limitations and uncertainties in the LCI data have
been discussed previously and are generally related to: (1) uncertainties in data from secondary
sources that may not be representative of the geographic and temporal boundaries of this LCA,
and (2) uncertainties in a few of the primary data points collected specifically for this project.
With regard to the latter, glass manufacturing energy inputs are particularly uncertain despite
numerous attempts to resolve the uncertainty, but are responsible for a significant portion of
CRT human health impacts. Glass manufacturing energy inputs are evaluated in a sensitivity
analysis in Section 3.4. The amount of LNGused as an ancillary material in LCD
monitor/module manufacturing is also uncertain (also despite attempts to resolve questions
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3.3 BASELINE LCIA RESULTS
regarding the data), but this material contributes a significant portion of LCD occupational health
impacts. As noted previously, removing this application of LNG from the LCD monitor/module
manufacturing inventory would reduce the LCD chronic occupational health effects score by
68%.
3.3.13.5 Aesthetic impacts (odor)
Figure 3-20 presents the CRT and LCD LCIA results for the aesthetic impacts (odor)
category, based on the impact assessment methodology presented in Section 3.1.2.12. Complete
results for the CRT and LCD are presented in Tables M-35 and M-36 in Appendix M,
respectively. The life-cycle aesthetic (odor) impact result is 7.58 million m3 malodorous air per
functional unit for the CRT and 5.04 million m3 malodorous air per functional unit for the LCD.
As shown in the figure, this impact category indicator is dominated by air emissions in the
manufacturing stage for both the CRT (96% of total) and the LCD (98% of total). Both monitor
types receive relatively minor contributions in the use and materials processing life-cycle stages,
and negative values at end of life. Negative values are due to the offset of electric power plant
emissions from incineration with energy recovery.
'E 7,000,000
re 5,000,000
o
+= 3,000,000
c
s2 1,000,000
?5
£ -1,000,000 J
129,000
Odor n Upstream
• Mfg
7,280,000 rjUse
4,930,000 nEOL
I I
201 '°°° 74,900
| -34,100 61,600 | | ' -23,000
CRT LCD
Monitor type
Figure 3-20. Odor impacts by life-cycle stage
Major Contributors to the CRT Aesthetics (Odor) Result
Table 3-49 lists the materials that contribute to the top 99% of the CRT aesthetic impacts
result and the LCI data type. Air emissions of hydrogen sulfide from LPG production in the
manufacturing life-cycle stage dominate the CRT odor impacts, contributing 94% of the total
score. Hydrogen sulfide impacts are calculated based on an odor threshold value (OTV) of
0.00043 mg/m3. [See Table K-7 in Appendix K for a list of OTVs used to calculate aesthetic
(odor) impacts.] As noted previously, most of the LPG produced by this process is used as a fuel
in CRT glass manufacturing, but glass manufacturing energy inputs are uncertain. The next
largest contributor to the CRT is acetaldehyde emitted from the U.S. electric grid during the use
stage. Acetaldehyde has a lower OTV (0.00027 mg/m3) than LPG, and is also emitted in smaller
quantities. Emissions of hydrogen sulfide from fuel oil #6 production, steel production, and
ABS production are the remaining top contributors to the CRT aesthetic impacts score. LCI data
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3.3 BASELINE LCIA RESULTS
for all of the top contributors are either from secondary data sets or developed by CDP
researchers from secondary sources.
Table 3-49. Top 99% of the CRT aesthetic (
Life-cycle stage
Manufacturing
Use
Manufacturing
Materials processing
Materials processing
Process group
LPG production
U.S. electric grid
Fuel oil #6 production
Steel production, cold-
rolled, semi-finished
ABS production
Material
Hydrogen sulfide
Acetaldehyde
Hydrogen sulfide
Hydrogen sulfide
Hydrogen sulfide
LCI data
type
Secondary
Model/secondary
Secondary
Secondary
Secondary
Contribution to
impact score*
94%
2.5%
0.98%
0.42%
0.31%
odor) impacts score
*Column may not add to 99% due to rounding.
Major Contributors to the LCD Aesthetics (Odor) Result
Table 3-50 presents the materials that contribute to the top 99% of the LCD aesthetics
impact score and the LCI data type. LCD impacts are dominated by air emissions of phosphine
from LCD monitor/module manufacturing, which contribute 89% of the total score. OTVs
reported for phosphine range from 0.014 to 2.8 mg/m3. The lower, more sensitive value (0.014
mg/m3) was used to calculate impacts.
Table 3-50. Top 99% of the LCD aesthetic (odor) impacts score
Life-cycle stage
Manufacturing
Manufacturing
Use
Manufacturing
Manufacturing
Process group
LCD monitor/module mfg.
LPG production
U.S. electric grid
LCD monitor/module mfg.
LCD monitor/module mfg.
Material
Phosphine
Hydrogen sulfide
Acetaldehyde
Ammonia
Acetic acid
LCI data
type
Primary
Secondary
Model/secondary
Primary
Primary
Contribution to
impact score*
89%
6.8%
1.4%
1.2%
0.44%
*Column may not add to 99% due to rounding.
Other significant contributors include hydrogen sulfide from LPG production,
acetaldehyde from the U.S. electric grid, and ammonia and acetic acid from LCD
module/monitor manufacturing. Most of the LPG made in the LPG production process is used
as a fuel in LCD glass manufacturing, indicating this process is ultimately responsible for LPG
production impacts. However, LCD glass energy inputs are uncertain and evaluated in a
sensitivity analysis (Section 3.4). LCD monitor/module manufacturing data were collected
directly from manufacturers by the CDP, while the LPG production inventory was obtained from
Ecobilan. The U.S. electric grid inventory was developed by CDP researchers from secondary
sources.
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3.3 BASELINE LCIA RESULTS
Limitations and Uncertainties
Aesthetic (odor) impact scores are based on the identity and amount of odor-causing
chemicals (Heijungs etal., 1992; EPA, 1992), released to the air divided by their chemical-
specific OTVs. An OTV is the lowest concentration of a substance in air that can be smelled
based on a standardized test. Limitations and uncertainties in the aesthetics impact score stem
from structural or model uncertainty (whether or not odor thresholds will actually be exceeded),
OTV data uncertainty (how well published OTVs represent the odor threshold of different
populations), and LCI data uncertainty.
The aesthetics impact score calculates the mass of malodorous air that could result if a
chemical release occurs in a finite volume of air. It does not predict whether actual odor impacts
will occur. This is because LCI data do not describe the time rate of release or whether dilution
and mixing with ambient air will dilute the concentration of a pollutant to below its odor
threshold. In addition, odor thresholds are highly variable because of the differing ability of
individuals to detect odors. Therefore, the impact scores may not account for odors perceived by
the most sensitive populations or may overstate impacts perceived by less sensitive populations.
Finally, the aesthetic impact scores are subject to the limitations and uncertainties in the LCI
data, since they are calculated from air emissions data in the inventories. The limitations and
uncertainties in LCI data were discussed in Section 2.2.2.2, and have been discussed extensively
with LCIA results for other impact categories, above.
3.3.14 Ecotoxicity
Ecotoxicity refers to effects of chemical outputs on non-human living organisms. As
discussed in Section 3.1.2.13, ecotoxicity impact categories included in the scope of this LCA
include impacts to aquatic and terrestrial organisms.
Ecotoxicity impacts are calculated using the scoring of inherent properties approach
where an impact score is based on the inventory amount weighed by a hazard value (HV). The
HV represents the toxicity of a specific material to aquatic or terrestrial organisms (see
Table K-8 in Appendix K for a list of toxicity values used to calculate hazard values). Aquatic
HVs are based on acute and chronic toxicity values for fish, while terrestrial HVs are based on
chronic noncancer toxicity values for mammals, usually rodents. Similar to the chronic human
health impacts discussed in Section 3.3.13, the inventory amount (the toxic chemical outputs to
water for aquatic toxicity effects, and the outputs to air and water for terrestrial toxicity effects)
is used as a surrogate for exposure, while the hazard value represents the inherent toxicity of the
substance.
Also like the human health effects methodology, the CDP ecotoxicity LCIA methodology
does not consider the fate and transport of a toxic chemical in the environment, nor does it
evaluate the potential for actual exposures to occur. In addition, the methodology is limited in
that it does not consider toxicity data from all types of aquatic or terrestrial species, but rather
focuses on a few selected species for which more toxicity data are available. The limitations and
uncertainties in the ecotoxicity scores are discussed further below, following the presentation of
results.
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3.3 BASELINE LCIA RESULTS
3.3.14.1 Aquati c toxi city
Figure 3-21 presents the CRT and LCD LCIA results for the aquatic toxi city impact
category, based on the impact assessment methodology presented in Section 3.1.2.13. Complete
results for the CRT and LCD are presented in Tables M-37 and M-38 in Appendix M,
respectively.
Aquatic ecotoxicity
§ 6.00E+00 n
To
§ 4.00E+00
?
o
i 2.00E+00
I
O.OOE+00
5.12E+00
8.93E-02
1.36E-01 O.OOE+00
O.OOE+00
Monitor type
Figure 3-21. Aquatic ecotoxicity impacts by life-cycle stage
The life-cycle aquatic toxicity indicator is 0.22 tox-kg per functional unit for the CRT
and 5.19 tox-kg per functional unit for the LCD. As shown in the figure, the CRT aquatic
toxicity indicator is driven by water releases in the materials processing stage (64% of total),
while the LCD aquatic toxicity indicator is completely dominated by water releases in the
manufacturing stage (99% of total). Both monitor types receive zero scores in the use stage and
small, negative values at end of life. Negative values are due to the offset of electric power plant
emissions from incineration with energy recovery.
Table 3-51 lists the materials that contribute to the top 99% of the CRT aquatic toxicity
impact score and the LCI data type. As shown in the table, CRT aquatic toxicity impacts are
broadly distributed across a number of different process groups, with most of the top
contributors responsible for less than five percent of the impacts. Most of the LCI data from
which the scores were calculated are from secondary data sets, although a substantial fraction are
from primary data collected to meet the goals and scope of the CDP LCA. Water releases of
phosphorus from CRT tube manufacturing represents the single largest contributor to the CRT
aquatic toxicity score, accounting for 26% of the total. Aquatic toxicity impacts for phosphorus
are driven more by its inherent acute toxicity than the output amount. The phosphorus acute HV
is calculated from a fish LC50 of 0.020 mg/L, which is significantly more toxic than the
geometric mean value of 23.5 mg/L.
The only other specific outputs that contribute more than five percent of the CRT aquatic
toxicity score are water discharges of aluminum ions (valence = +3) and copper ions (valence =
+1 and +2) from aluminum production. The aluminum HV is calculated from an LC50 value of
36 mg/L and a NOAEL value of 3.6 mg/L, which are within an order of magnitude of the
geometric mean values of 23.5 mg/L and 3.9 mg/L. Copper, on the other hand, is much more
toxic to fish, with an LC50 value of 0.014mg/L and a NOAEL value of 0.004 mg/L. The
3-86
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3.3 BASELINE LCIA RESULTS
aluminum aquatic toxicity score exceeds that of copper because it is discharged in much greater
quantities.
Table 3-51. Top 99% of the CRT aquatic toxicity impact score
Life-cycle stage
Manufacturing
Materials processing
Materials processing
Materials processing
Materials processing
Materials processing
Materials processing
Manufacturing
Materials processing
Materials processing
Materials processing
Materials processing
Manufacturing
Manufacturing
Manufacturing
Materials processing
Manufacturing
Materials processing
Manufacturing
Materials processing
Materials processing
Materials processing
Materials processing
Materials processing
Materials processing
Materials processing
Materials processing
Materials processing
Materials processing
Materials processing
Materials processing
Materials processing
Process group
CRT tube manufacturing
Aluminum production
Aluminum production
Invar
Invar
Invar
Lead
CRT tube manufacturing
Ferrite manufacturing
Aluminum production
ABS production
Lead
CRT glass/frit mfg.
CRT tube manufacturing
CRT tube manufacturing
Steel production, cold-
rolled, semi-finished
LPG production
Steel production, cold-
rolled, semi-finished
LPG production
Lead
Polycarbonate production
Steel production, cold-
rolled, semi-finished
Ferrite manufacturing
Aluminum production
ABS production
Invar
Ferrite manufacturing
ABS production
Styrene-butadiene
copolymer production
Aluminum production
Polycarbonate production
Aluminum production
Material
Phosphorus (yellow or white)
Aluminum (+3)
Copper (+1 & +2)
Copper (+1 & +2)
Aluminum (+3)
Zinc (+2)
Aluminum (+3)
Fluoride
Zinc (+2)
Zinc (+2)
Ammonia
Copper (+1 & +2)
Fluorides (F-)
Zinc (elemental)
Copper
Phosphorus (yellow or white)
Phenol
Ammonia
Aluminum (+3)
Zinc (+2)
Copper (+1 & +2)
Copper (+1 & +2)
Aluminum (+3)
Barium sulfate
Aluminum (+3)
Ammonia
Copper (+1 & +2)
Copper (+1 & +2)
Copper (+1 & +2)
Titanium tetrachloride
Mercury compounds
Strontium (Sr II)
LCI data
type
Primary
Secondary
Secondary
Secondary
Secondary
Secondary
Secondary
Primary
Secondary
Secondary
Secondary
Secondary
Primary
Primary
Primary
Secondary
Secondary
Secondary
Secondary
Secondary
Secondary
Secondary
Secondary
Secondary
Secondary
Secondary
Secondary
Secondary
Secondary
Secondary
Secondary
Secondary
Contribution
to impact
score*
26%
12%
9.5%
5.0%
4.4%
4.0%
3.6%
3.1%
3.0%
2.9%
2.7%
2.7%
2.6%
2.3%
2.1%
2.0%
1.9%
1.2%
1.1%
0.82%
0.54%
0.45%
0.43%
0.40%
0.39%
0.36%
0.31%
0.25%
0.24%
0.20%
0.19%
0.14%
3-87
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3.3 BASELINE LCIA RESULTS
Table 3-51. Top 99% of the CRT aquatic toxicity impact score
Life-cycle stage
Materials processing
Materials processing
Materials processing
Materials processing
Materials processing
Materials processing
Materials processing
Materials processing
Materials processing
Materials processing
Materials processing
Process group
Steel production, cold-
rolled, semi-finished
Ferrite manufacturing
Lead
Steel production, cold-
rolled, semi-finished
ABS production
Steel production, cold-
rolled, semi-finished
Styrene-butadiene
copolymer production
Steel production, cold-
rolled, semi-finished
Aluminum production
Polycarbonate production
Invar
Material
Aluminum (+3)
Ammonia
Barium sulfate
Nitrogen dixode
Mercury compounds
Zinc (+2)
Mercury compounds
Fluorides (F-)
Lead compounds
Zinc (+2)
Strontium (Sr II)
LCI data
type
Secondary
Secondary
Secondary
Secondary
Secondary
Secondary
Secondary
Secondary
Secondary
Secondary
Secondary
Contribution
to impact
score*
0.12%
0.12%
0.10%
0.088%
0.088%
0.087%
0.086%
0.086%
0.076%
0.076%
0.074%
*Corumn may not add to 99% due to rounding.
Table 3-52 lists the materials that contribute to the top 99% of the LCD aquatic toxicity
impact score and the LCI data type. Unlike the CRT, LCD impacts in this category are not
distributed across a number of different process groups, but dominated by phosphorus emissions
from a single process group, LCD monitor/module manufacturing. Phosphorus releases from
LCD monitor/module manufacturing are several orders of magnitude higher than phosphorus
releases from CRT tube manufacturing (the greatest contributor to the CRT aquatic toxicity
impact score). However, the LCD aquatic toxicity score for phosphorus is still driven by the
inherent acute toxicity of phosphorus, rather than the release amount.
Other top contributors to LCD impacts in this category include ammonia releases from
PMMA sheet production, and phosphorus emissions from LCD panel components
manufacturing. No toxicity data were available for ammonia. Consequently, it was assigned a
default HV of two, representative of mean acute and chronic fish toxicity values.
Table 3-52. Top 99% of the LCD aquatic toxicity impact score
Life-cycle stage
Manufacturing
Materials processing
Manufacturing
Process group
LCD monitor/module mfg.
PMMA sheet production
LCD panel components
Material
Phosphorus (yellow or white)
Ammonia
Phosphorus (yellow or white)
LCI data
type
Primary
Secondary
Primary
Contribution
to impact
score
98%
0.63%
0.56%
3-88
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3.3 BASELINE LCIA RESULTS
3.3.14.2 Terrestrial ecotoxicity
Figure 3-22 presents the CRT and LCD LCIA results for the terrestrial toxicity impact
category, based on the impact assessment methodology presented in Section 3.1.2.13. Complete
results for the CRT and LCD are presented in Tables M-39 and M-40 in Appendix M,
respectively.
§ 1 .80E+03
To
§ 1 .20E+03
?
o
i 6.00E+02
x O.OOE+00
O
Terrestrial ecotoxicity
165E+03
2.28E+02
9.46E+01
6.16E+02
2.88E-01
2.33E+02
4.54E+01
1.46E-02
CRT
LCD
Monitor type
Figure 3-22. Terrestrial ecotoxicity impacts by life-cycle stage
The life-cycle terrestrial toxicity indicator is 1,970 tox-kg per functional unit for the CRT
and 894 tox-kg per functional unit for the LCD. As shown in the figure, the CRT result is
dominated by toxic chemical outputs from electricity generation in the use stage, which account
for almost 84% of CRT impacts in this category. To a lesser degree, LCD terrestrial toxicity
impacts are also driven by emissions from electricity generation in the use stage, which account
for more than 69% of the total.
The materials processing stage contributes about 12% of CRT terrestrial toxicity impacts
and about five percent of LCD impacts. The manufacturing life-cycle stage is responsible for
five and 26% of CRT and LCD impacts in this category, respectively. Both monitors receive
very small terrestrial toxicity scores at end of life. This is because most terrestrial toxicity
impacts from CRT and LCD recycling and disposal processes are offset by a credit on electric
grid emissions when the monitors are incinerated with energy recovery.
The terrestrial toxicity impact results are almost identical to the chronic public health
effects results presented previously (see Section 3.3.13). Recall that human health and terrestrial
toxicity impacts are calculated using the same noncancer toxicity values (and the same inventory
data), with the main difference being that toxicity data on carcinogenic effects are excluded from
the terrestrial toxicity impact calculations. However, human health and terrestrial toxicity
impacts are almost identical because: (1) impacts in both categories are dominated by emissions
of sulfur dioxide from electricity generation (see Tables 3-53 and 3-54 below for top contributors
to the CRT and LCD terrestrial toxicity impacts), and (2) sulfur dioxide has a high hazard value
for noncancer effects and a hazard value of zero for cancer effects.
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3.3 BASELINE LCIA RESULTS
Table 3-53 presents the materials that contribute to the top 99% of the CRT terrestrial
toxicity impact score. As already noted, SO2 emissions from a number of different process
groups almost completely dominate CRT impacts in this category, accounting for slightly less
than 99% of the total. Most of these emissions are from the combustion of fossil fuels to
generate electricity. All of the SO2 LCI data are either from secondary data sets not developed
specifically for the CDP or from the electric grid inventories developed from secondary sources
for this project. Sulfur dioxide has a relatively high HV, based on an inhalation NOAEL of
0.104 mg/m3 and the geometric mean inhalation NOAEL of 68.7 mg/m3. In addition, as noted in
the section on human health effects (3.3.13), from a mass loading perspective (i.e., based on the
inventory alone), SO2 emissions were the second largest contributor to CRT life-cycle air
pollutant emissions, exceeded only by emissions of carbon dioxide (CO2). Carbon dioxide is not
classified as toxic, and therefore did not contribute to the terrestrial toxicity impact category.
Table 3-53. Top 99% of the CRT terrestrial toxicity impact score
Life-cycle stage
Use
Materials processing
Manufacturing
Manufacturing
Materials processing
Materials processing
Materials processing
Manufacturing
Process group
U.S. electric grid
Invar
Japanese electric grid
U.S. electric grid
Steel production, cold-
rolled, semi-finished
Aluminum production
Polycarbonate production
LPG production
Material
Sulfur dioxide
Sulfur dioxide
Sulfur dioxide
Sulfur dioxide
Sulfur dioxide
Sulfur dioxide
Sulfur dioxide
Carbon monoxide
LCI data
type
Model/secondary
Secondary
Model/secondary
Model/secondary
Secondary
Secondary
Secondary
Secondary
Contribution to
impact score*
83%
8.4%
2.9%
1.3%
1.3%
0.70%
0.40%
0.27%
* Column may not add to 99% due to rounding.
Table 3-54 lists the materials that contribute to the top 99% of the LCD terrestrial
toxicity impact score and the LCI data type. LCD impacts in this category are also dominated by
SO2 emissions, which are responsible for roughly 92% of impacts. Like the CRT, most of these
emissions occur from electricity generation, either during the use stage (68%) or manufacturing
(21%). As noted previously, SO2 has a relatively high HV, due to its low toxicity value
(inhalation NOAEL = 0.104 mg/m3). Similar to the CRT, from a mass loading perspective (i.e.,
based on the inventory alone), SO2 emissions were the second largest contributor to LCD life-
cycle air pollutant emissions, exceeded only by emissions of CO2.
Other top contributors to the LCD terrestrial toxicity score include phosphine and
phosphorus from LCD monitor/module manufacturing, and carbon monoxide and methane from
natural gas production. As noted above in the section on chronic occupational health effects, the
phosphine, phosphorus, and benzene scores are driven more by their inherent toxicity than their
output amounts.
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3.3 BASELINE LCIA RESULTS
Table 3-54. Top 99% of the LCD terrestrial toxicity impact score
Life-cycle stage
Use
Manufacturing
Manufacturing
Materials processing
Materials processing
Materials processing
Materials processing
Materials processing
Materials processing
Materials processing
Manufacturing
Process group
U.S. electric grid
Japanese electric grid
LCD monitor/module mfg.
Steel production, cold-
rolled, semi-finished
PMMA sheet production
Natural gas production
Aluminum production
Natural gas production
Polycarbonate production
Natural gas production
LCD monitor/module mfg.
Material
Sulfur dioxide
Sulfur dioxide
Phosphine
Sulfur dioxide
Sulfur dioxide
Benzene
Sulfur dioxide
Carbon monoxide
Sulfur dioxide
Methane
Phosphorus
(yellow or white)
LCI data
type
Model/secondary
Model/secondary
Primary
Secondary
Secondary
Secondary
Secondary
Secondary
Secondary
Secondary
Primary
Contribution
to impact
score
68%
21%
3.2%
1.4%
0.96%
0.59%
0.57%
0.50%
0.50%
0.39%
0.38%
3.3.14.3 Terrestrial toxicity impact scores modified to exclude sulfur dioxide
Because the terrestrial toxicity impact scores for both the CRT and the LCD are
dominated by SO2 emissions, a secondary analysis was run to identify the top contributors to
these impacts when SO2 emissions are excluded from the inventories. Results of this analysis
may be more useful to manufacturers seeking to identify problematic toxic chemicals within
their own manufacturing processes.
Figure 3-23 presents the CRT and LCD terrestrial toxicity impact scores by life-cycle
stage when SO2 emissions are excluded from the inventories. Under this scenario, the CRT
score is reduced almost 99% from 1,970 tox-kg to 21 tox-kg per functional unit, and the LCD
score is reduced about 94%, from 894 tox-kg to 54 tox-kg per functional unit. Note that these
scores should not be used to evaluate which monitor type has higher overall impacts in this
category, but they are useful for identifying life-cycle improvement opportunities that were
previously obscured by SO2 impacts.
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Terrestrial ecotoxicity (without SO2)
60.0
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3.3 BASELINE LCIA RESULTS
Table 3-55. Materials contributing greater than 1% of the CRT
terrestrial toxicity impact score (without SO2)
Life-cycle stage
Manufacturing
Materials processing
Use
Manufacturing
Use
Manufacturing
Manufacturing
Manufacturing
Materials processing
Use
Manufacturing
Manufacturing
Use
Use
Materials processing
Materials processing
Manufacturing
Materials processing
Manufacturing
Process group
LPG production
Lead
U.S. electric grid
LPG production
U.S. electric grid
LPG Production
LPG production
LPG production
Aluminum production
(all virgin)
U.S. electric grid
CRT glass/frit mfg.
LPG production
U.S. electric grid
U.S. electric grid
Steel Prod., cold-rolled,
semi-finished
Invar
CRT tube manufacturing
Lead
LPG production
Material
Carbon monoxide
Arsenic
Nitrogen oxides
Vanadium
Carbon monoxide
Benzene
Methane
Sulfur oxides
Titanium tetrachloride
Methane
Fluorides (F-)
Nitrogen oxides
Arsenic
Hydrochloric acid
Carbon monoxide
Titanium tetrachloride
Carbon monoxide
Titanium tetrachloride
Arsenic
LCI data
type
Secondary
Secondary
Model/secondary
Secondary
Model/secondary
Secondary
Secondary
Secondary
Secondary
Model/secondary
Primary
Secondary
Model/secondary
Model/secondary
Secondary
Secondary
Primary
Secondary
Secondary
Contribution
to impact
score
26%
11%
5.7%
5.1%
4.9%
4.2%
4.1%
3.9%
3.5%
3.1%
2.8%
2.8%
2.7%
2.4%
1.4%
1.2%
1.0%
1.0%
1.0%
Table 3-56 presents the materials that contribute greater than one percent of LCD
terrestrial toxicity impacts when SO2 emissions are excluded from the LCD inventory. As with
the LCD modified chronic human health results discussed in Section 3.3.13, when SO2 emissions
are excluded, phosphine emissions from LCD monitor/module manufacturing are the dominant
factor in the LCD terrestrial toxicity score, contributing 53% of the total. Other significant
contributors include benzene, carbon monoxide, methane, and nitrogen oxides from natural gas
production, and phosphorus, fluorides, tetramethyl ammonium hydroxide, and nitrogen oxides
from LCD monitor/module manufacturing. Recall that the LCD monitor/module manufacturing
process consumes the majority of the natural gas made in the natural gas production process,
where LNG is used as an ancillary material. However, only one of the seven LCD
monitor/module manufacturers that provided inventory data to the CDP reported the ancillary
use of LNG. Other manufacturers reported using LNG as a fuel.
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Table 3-56. Materials contributing greater than 1% of the LCD
terrestrial toxicity impact score (without SO2)
Life-cycle stage
Manufacturing
Materials processing
Materials processing
Materials processing
Manufacturing
Manufacturing
Materials processing
Manufacturing
Manufacturing
Process group
LCD module/monitor mfg.
Natural gas production
Natural gas production
Natural gas production
LCD module/monitor mfg.
LCD module/monitor mfg.
Natural gas production
LCD module/monitor mfg.
LCD module/monitor mfg.
Material
Phosphine
Benzene
Carbon monoxide
Methane
Phosphorus (yellow or white)
Fluorides (F-)
Nitrogen oxides
Tetramethyl ammonium
hydroxide
Nitrogen oxides
LCI data
type
Primary
Secondary
Secondary
Secondary
Primary
Primary
Secondary
Primary
Primary
Contribution
to impact
score
53%
9.8%
8.2%
6.5%
6.3%
4.7%
1.2%
1.2%
1.0%
3.3.14.4 Limitations and uncertainties
Most of the limitations and uncertainties in the ecotoxicity results are similar to the
limitations and uncertainties in the human health effects scores. The reader is referred to Section
3.3.13 for a full discussion of these limitation and uncertainties. In summary, they can be
grouped into three categories:
1. Structural or modeling limitations and uncertainties associated with the accuracy of the
toxic chemical classification method and the chemical scoring approach used to
characterize human health effects.
2. Toxicity data limitations and uncertainties associated with the availability and accuracy
of toxicity data to represent ecotoxicity.
3. LCI data limitations and uncertainties associated with the accuracy and
representativeness of the inventory data.
With regard to toxicity data, other limitations and uncertainties in the ecotoxicity results
are related to the use of surrogates to assess toxicity to all species within an impact category.
For example, the aquatic toxicity category uses fish (usually the fathead minnow) as a surrogate
to assess toxicity to all aquatic organisms, but it has been well-established in the ecotoxicology
literature that fish are not the most sensitive test species to all or most industrial chemicals. In
fact, invertebrates (daphnids) or algae (Selenastrum) often are more sensitive to particular
chemicals than fish (Smrchek, 1999). Similarly, the terrestrial toxicity category uses mammals,
primarily rodents, as a surrogate to assess toxicity to all terrestrial organisms. Terrestrial plants
and soil organisms (insects, earthworms, etc.) are not considered, but both of these may be more
sensitive than mammals.
Because there are difficulties in comparing test endpoints for different types of
organisms, and because there is a very limited toxicity database for some of the other organisms,
the LCIA methodology employed in this study uses fish as a surrogate for aquatic toxicity and
mammals as a surrogate for terrestrial ecotoxicity. This helps to reduce data gaps and the
difficulties in comparing test endpoints for different types of organisms. Furthermore, we
believe this approach to be acceptable for a study, such as the CDP LCA, that gives relative
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3.3 BASELINE LCIA RESULTS
ranking of impacts from different chemicals or process groups instead of absolute values.
However, it should be noted that this approach can result in an underestimation of the absolute
ecotoxicity and hazards of chemicals.
With regard to LCI data limitations not discussed previously, it should be noted that the
CRT and LCD LCAs do not address spills or other accidental releases that could have significant
adverse effects on aquatic or terrestrial organisms. This is a common limitation of LCA, which
is often too labor-intensive to address different operational scenarios across the product life
cycle.
3.3.15 Summary of Top Contributors by Impact Category
Tables 3-57 and 3-58 summarize the top contributors to CRT and LCD life-cycle impacts
by impact category. As shown in Table 3-57, CRT impacts are largely driven by two factors: (1)
the large amount of LPG fuel used in CRT glass/frit manufacturing, and (2) the relatively large
amount of electricity consumed during the use stage. The LPG production process yields the
CRT's top contributor in eight of 20 impact categories. Most of this LPG is used as a fuel source
in CRT glass manufacturing in the glass/frit process group, which, in turn, produces the top
contributor to two of 20 impact categories. Thus, LPG used in the glass/frit process group
(primarily CRT glass manufacturing) is ultimately the key driver for CRT impacts in ten
categories. Similarly, outputs from electricity generation during the use stage result in the top
contributor to seven CRT impact categories. Note that in 14 of the 20 impact categories, the top
contributor to CRT impacts is responsible for more than 50% of impacts.
Both the glass manufacturing energy and the use stage lifespan (which determines the
amount of electricity generated during the use stage) are evaluated in a sensitivity analysis in
Section 3.4. In the modified glass energy sensitivity analysis, LPG inputs are greatly reduced
and impacts are therefore reduced, but in the modified lifespan (manufactured life) sensitivity
analysis, the number of hours a monitor is in use is increased. Thus, CRT impacts are increased.
LCD impacts are not as dominated by a few data points, but a few processes (LCD
monitor/module manufacturing and electricity generation in the use stage) are responsible for a
large percent of the impacts. As shown in Table 3-58, both of these processes result in the top
contributors to six LCD impact categories each. In addition, the process to produce LNG used as
an ancillary material in LCD monitor/module manufacturing is the top contributor to an
additional impact category (photochemical smog). Note that in 11 of the 20 impact categories,
the top contributor to LCD impacts is responsible for more than 50% of impacts.
Like the CRT, both the glass energy inputs and use stage lifespan of the LCD are
evaluated in a sensitivity analysis in Section 3.4. LCD monitor/module manufacturing energy
and LCD EOL dispositions are also evaluated. LCD monitor/module manufacturing energy was
selected for a sensitivity analysis because of the high degree of variability seen in data provided
by manufacturers. The impacts presented in the baseline scenario are calculated with energy
outliers removed from the average, but the outliers are included in the sensitivity analysis. This
results in higher electricity consumption but lower fuel consumption, which, in turn, causes
reduced impacts in some categories and increased impacts in others. Note that the LNG used as
an ancillary material in LCD monitor/module manufacturing is not affected by the sensitivity
analysis since it only focuses on materials used as an energy source.
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3.3 BASELINE LCIA RESULTS
Table 3-57. Summary of top contributors to CRT impacts by impact category
Impact category
Renewable resource
use
Nonrenewable
resource use
Energy use
Solid waste landfill
use
Hazardous waste
landfill use
Radioactive waste
landfill use
Global warming
Ozone depletion
Photochemical smog
Acidification
Air particulates
Water eutrophication
Water quality, BOD
Water quality, TSS
Radioactivity
Chronic health effects,
occupational
Chronic health effects,
public
Aesthetics (odor)
Aquatic toxicity
Terrestrial toxicitv
Top contributors
Life-cycle
stage
Manufacturing
Manufacturing
Manufacturing
Use
End-of-life
Use
Use
Use
Manufacturing
Use
Manufacturing
Manufacturing
Manufacturing
Manufacturing
Materials
Processing
Manufacturing
Use
Manufacturing
Manufacturing
Use
Process group
LPG production
LPG production
CRT glass/frit mfg.
U.S. electric grid
CRT landfilling
U.S. electric grid
U.S. electric grid
U.S. electric grid
LPG production
U.S. electric grid
LPG production
LPG production
LPG production
LPG production
Steel production, cold-
rolled, semi-finished
CRT glass/frit
manufacturing
U.S. electric grid
LPG production
CRT tube
manufacturing
U.S. electric grid
Material
water
Petroleum (in ground)
Liquefied petroleum
gas
Coal waste
EOL CRT monitor,
landfilled
Low-level radioactive
waste
Carbon dioxide
Bromomethane
Hydrocarbons,
unspeciated
Sulfur dioxide
PM
COD
BOD
Suspended solids
Plutonium-241
(isotope)
Liquefied petroleum
gas
Sulfur dioxide
Hydrogen sulfide
Phosphorus
(yellow or white)
Sulfur dioxide
Contribution
to impact
score
79%
56%
72%
38%
91%
61%
64%
49%
36%
47%
43%
72%
96%
97%
62%
78%
83%
94%
26%
83%
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3.3 BASELINE LCIA RESULTS
Table 3-58. Summary of top contributors to LCD impacts by impact category
Impact category
Renewable resource
use
Nonrenewable resource
use
Energy use
Solid waste landfill use
Hazardous waste
landfill use
Radioactive waste
landfill use
Global warming
Ozone depletion
Photochemical smog
Acidification
Air particulates
Water eutrophication
Water quality, BOD
Water quality, TSS
Radioactivity
Chronic health effects,
occupational
Chronic health effects,
public
Aesthetics (odor)
Aquatic toxicity
Terrestrial toxicitv
Top contributors
Life-cycle stage
Manufacturing
Materials
processing
Use
Use
End-of-life
Use
Manufacturing
Manufacturing
Materials
processing
Use
Materials
processing
Manufacturing
Manufacturing
Manufacturing
Materials
processing
Manufacturing
Use
Manufacturing
Manufacturing
Use
Process group
LCD monitor/module mfg.
Natural gas production
LCD monitor use
U.S. electric grid
LCD landfilling
U.S. electric grid
LCD monitor/module mfg.
LCD panel components
manufacturing
Natural gas production
U.S. electric grid
Steel production, cold-
rolled, semi-finished
LCD monitor/module mfg.
LCD monitor/module mfg.
LPG production
Steel production, cold-
rolled, semi-finished
LCD monitor/module mfg.
U.S. electric grid
LPG production
LCD monitor/module mfg.
U.S. electric srid
Material
Water
Natural gas
(in ground)
Electricity
Coal waste
EOL LCD
monitor,
landfilled
Low-level
radioactive waste
Sulfur
hexafluoride
HCFC-225cb
Nonmethane
hydrocarbons,
unspeciated
Sulfur dioxide
PM
Nitrogen
BOD
Suspended solids
Plutonium-241
(isotope)
Liquefied natural
gas
Sulfur dioxide
Hydrogen sulfide
Phosphorus
(yellow or white)
Sulfur dioxide
Contribution
to impact
score
38%
65%
30%
44%
97%
44%
29%
34%
45%
31%
45%
67%
61%
66%
96%
58%
68%
94%
98%
68%
3-97
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3.4 SENSITIVITY ANALYSES
3.4 SENSITIVITY ANALYSES
Due to assumptions and uncertainties in this LCA, as in any LCA, several sensitivity
analyses of the baseline results were conducted. Section 2.7.3 described how areas for
sensitivity analyses (scenarios) were selected, and the modifications made to the baseline
inventory. Sections 3.4.1 through 3.4.4 recap these modifications and present sensitivity
analysis results. Section 3.4.5 summarizes the effects of different scenarios on CRT and LCD
impacts.
3.4.1 Manufactured Life Scenario
Due to the uncertainty and assumptions associated with the baseline use stage lifespan
(effective life) scenario, a "manufactured life" scenario was also considered. Recall that the
manufactured life is defined as the length of time a monitor is designed to operate effectively,
while the effective life is defined as the actual amount of time a monitor is used, by one or
multiple users, before it reaches its final disposition. The manufactured life is the number of
hours a monitor would function as manufactured, and is independent of user choices or actions.
Section 2.4.1.3 presented a detailed discussion of how the manufactured life was determined, and
is summarized below.
The manufactured life of both monitor types was estimated using the
mean-time-before-failure (MTBF) specifications of the monitor and its components. From
review of MTBF information obtained on CRT-based monitors (see Appendix H, Attachment A,
Table A2), it appears that the CRT tube itself is the component that 99% of the time determines
whether the entire monitor has reached its end-of-life. Thus, an average of the two ranges
obtained on the estimated lifetime of CRT tubes (10,000 and 15,000 hours) was used as the CRT
manufactured lifetime (12,500 hours).
For active matrix LCDs, the components that have the greatest potential to fail first are
the display panel itself (including the liquid crystals and thin-film transistors), backlights, driver
integrated circuit (1C) tabs, and other smaller components. The backlights and driver 1C tabs can
be field-replaced, thus their failure does not necessarily represent the end of the monitor's life.
However, failure of the liquid crystals or transistors, which would require replacement of the
display panel itself, would most likely mean that the monitor cannot be cost-effectively repaired.
Thus, in this study, the amount of time an LCD monitor would operate during its manufactured
life is assumed to be the average of the non field-replaceable values, or 45,000 hours. In order
for a monitor to operate for 45,000 hours, any major field-replaceable parts that have MTBFs
less than 45,000 hours are accounted for in the inventory. For example, assuming the backlights
last on average 32,500 hours (the average of the values obtained for backlights), approximately
1.4 backlights on average would be needed for every panel during its 45,000 hour lifetime.
To calculate the manufactured life electricity consumption (kWh/life), the energy use rate
(kW) was multiplied by the lifespan (hours/life) for each monitor in each power mode (see Table
2-20 in Section 2.4.1.3). The LCD manufactured life (45,000 hours) is 3.6 times greater than the
CRT manufactured life (12,500 hours). In an LCA, comparisons are made based on functional
equivalency. Therefore, if one monitor will operate for a longer period of time than another,
impacts should be based on an equivalent use. Thus, based on equivalent use periods, 3.6 CRTs
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3.4 SENSITIVITY ANALYSES
would need to be manufactured for every LCD. This was incorporated into the profile analysis
for the manufactured life LCA. To apply the manufactured life scenario to the CRT and LCD
life-cycle profiles, the following modifications were made to the baseline (effective life)
scenario:
• change the CRT electricity input in the use stage from 635 kWh (2,286 MJ) to 788 kWh
(2,837 MJ);3
change the LCD electricity input in the use stage from 237 kWh (853 MJ) to 1,035 kWh
(3,726 MJ);
• increase the manufacturing of CRTs by a factor of 3.6 to account for the functional
equivalency of CRTs and LCDs. This was done by increasing the functional unit by a
factor of 3.6, which equates to manufacturing, using, and recycling or disposing of 3.6
times more CRTs than in the baseline case; and
• increase the manufacturing of the LCD backlight lamp by a factor of 1.4 to account for
the functional equivalency of LCDs and CRTs. This was done by increasing the
backlight lamp mass (0.0023 kg) by a factor of 1.4, which in turn results in an increase in
inputs and outputs associated with manufacturing the backlilght.
Table 3-59 presents the CRT and LCD life-cycle results by impact category for the
baseline and manufactured life scenarios. It also presents the percent change from the baseline
to the manufactured life scenario for both monitor types. Note that the manufactured life results
are most useful for evaluating the CRT and LCD together, not for comparing the CRT or LCD
baseline (effective life) results to its manufactured life results. This is because the CRT and
LCD manufactured life results are functionally equivalent, but the CRT to CRT and LCD to
LCD effective life and manufactured life scenarios are not. The baseline for both monitor types
represents impacts from manufacture and final disposition of one monitor. The CRT
manufactured life scenario represents impacts from 3.6 CRT monitors and the LCD
manufactured life scenario represents impacts from one LCD monitor and 1.4 backlights.
However, the percent change figures are presented to better understand how the manufactured
life scenario affects overall results.
3 This represents the electricity use for a 12,500 hour life span. This figure is then multiplied by a factor of
3.6 in the functional equivalency calculations (see third bullet, below).
3^99
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3.4 SENSITIVITY ANALYSES
Table 3-59. Baseline and sensitivity analysis results—manufactured life
Impact category
Renewable resource use
Nonrenewable resource use
Energy use
Solid waste landfill use
Hazardous waste landfill use
Radioactive waste landfill use
Global warming
Ozone depletion
Photochemical smog
Acidification
Air particulates
Water eutrophication
BOD
TSS
Radioactivity
Chronic health effects,
occupational
Chronic health effects, public
Aesthetics (odor)
Aquatic toxicity
Terrestrial toxicity
Units/ Monitor
kg
kg
MJ
m3
m3
m3
kg-CO2 eq.s
kg-CFC-11 eq.s
kg-ethene eq.s
kg-SO2 eq.s
kg
kg-phosphate
eq.s
kg
kg
Bq
tox-kg
tox-kg
m3
tox-kg
tox-kg
CRT
Baseline
1.31e+04
6.68e+02
2.08e+04
1.67e-01
1.68e-02
2.00e-04
6.95e+02
2.05e-05
1.71e-01
5.25e+00
3.01e-01
4.82e-02
1.95e-01
8.75e-01
3.85e+07
9.34e+02
1.98e+03
7.58e+06
2.25e-01
1.97e+03
Manu-
factured
4.83e+04
2.58e+03
7.70e+04
6.866-01
6.05e-02
8.00e-04
2.90e+03
8.27e-05
6.20e-01
2.19e+01
1.13e+00
1.74e-01a
7.02e-01
3.15e+00
1.14e+08
3.39e+03
8.56e+03
2.74e+07
S.lOe-Ol
8.54e+03
%
change
268%
286%
270%
312%
260%
328%
317%
304%
262%
317%
277%
260%
260%
260%
197%
263%
333%
262%
260%
333%
LCD
Baseline
2.80e+03
3.64e+02
2.84e+03
5.43e-02
3.60e-03
l.OOe-04
5.93e+02
1.37e-05
1.416-01
2.96e+00
1.156-01
4.96e-02
2.83e-02
6.15e-02
1.22e+07
6.96e+02
9.02e+02
5.04e+06
5.19e+00
8.94e+02
Manu-
factured
4.30e+03
6.12e+02
5.71e+03
1.79e-01
3.60e-03
3.00e-04
1.17e+03
2.66e-05
1.476-01
7.29e+00
1.876-01
4.96e-02
2.83e-02
6.15e-02
1.28e+07
7.41e+02
2.98e+03
5.30e+06
5.19e+00
2.97e+03
%
change
53.5%
68.0%
101%
230%
0.00%
194%
97.3%
94.1%
4.22%
146%
63.4%
0.02%
0.02%
0.02%
4.49%
6.47%
230%
5.00%
0.02%
232%
Bold indicates impact category
indicator is now greater than the
indicator that reversed direction from the baseline scenario such that the CRT
LCD.
As shown in Table 3-59, under the manufactured life scenario CRT impacts exceed those
of the LCD in every impact category except aquatic toxicity. CRT impacts were expected to be
greater than those of the LCD in most impact categories for the following reasons:
• Under the baseline scenario CRT impacts exceeded those of the LCD in every category
but water eutrophication and aquatic toxicity.
• The manufactured life scenario assumes more CRTs are manufactured than LCDs during
the manufactured life lifespan, which results in greater impacts.
• The manufactured life use stage is longer than the baseline, effective life use stage, and
the CRT consumes more electricity during use than the LCD.
By looking at the percent change in impact scores from the baseline to manufactured life
for a monitor type we can better understand which aspect of the life-cycle is driving impacts.
For example, CRT impacts increased by roughly 260% in several impact categories, which is the
increase from manufacturing or disposing of an additional 2.6 monitors. Energy impacts
increased by more than 260% due to the additional increase in electricity consumption during
use. The CRT chronic public human health effects category increased by some 330%. This is
explained by the increase in SO2 emissions in the use stage and the high HV for SO2, which has a
3-100
-------
3.4 SENSITIVITY ANALYSES
proportionately greater effect on overall impacts than increased outputs of other pollutants with
lower HVs in other life-cycle stages.
LCD impacts increased only slightly from the baseline to the manufactured life scenario
in some impact categories, but increased up to 230% in others. Most of the LCD impact
categories with less than one percent increase are for impacts related to water discharges (e.g.,
water eutrophication, aquatic toxicity, etc.). This is because the most significant change to the
LCD inventory from the baseline to the manufactured life scenario was in the use stage, and few
water discharges are reported in the U.S. electric grid inventory. On the other hand, the chronic
public health effects and terrestrial toxicity impact categories show the greatest increase. These
results are driven by air emissions of SO2 from U.S. power production, which increased
significantly with the longer lifespan.
To further illustrate how the longer lifespan (and additional manufacturing requirements,
mainly for the CRT) in the manufactured life scenario is affecting impacts, Figures 3-24 and 3-
25 compare the energy impacts and public chronic health effects, respectively, of both monitor
types under the baseline and manufactured life scenarios. As shown in Figure 3-24, CRT energy
impacts are still dominated by the manufacturing stage in the manufactured life scenario. This is
mainly due to the large amount of LPG used to manufacture 3.6 sets of CRT glass. On the other
hand, LCD energy impacts during the use stage exceeded those in manufacturing by a factor of
about 2.6 in the baseline scenario, but are ten times greater in the manufactured life scenario.
This is due to the longer lifespan for a single LCD in the manufactured life scenario.
3 Energy use impacts
w
7.00E+04 -,
^ 6.00E+04 -
'§ 5.00E+04 -
"s 4.00E+04 -
.2 3.00E+04 -
| 2.00E+04 -
£5 l.OOE+04 -
^ O.OOE+00 -
-l.OOE+04 -
>0
$1 1? ill?
in!i ^K?
Baseline Manu. Life
Scenario
CRT
fj Upstream
• Mfg.
DUse
rjEOL
8 m ^
Ml? ?« ^ I
1 3 «l ^5
2 °° S 2 °o
Baseline Manu. Life
LCD
Figure 3-24. Energy use: baseline and manufactured life sensitivity results
Figure 3-25 shows that CRT chronic public health impacts are similarly distributed in the
baseline and manufactured life scenarios. However, a greater percentage of LCD chronic health
impacts are in the use stage under the manufactured life scenario than the baseline due to the
longer use stage.
3-101
-------
3.4 SENSITIVITY ANALYSES
Chronic public health effects rj Upstream
8.00E+03 -,
3 6.00E+03 -
.0 4.00E+03 -
5
J 2.00E+03 -
"^ O.OOE+00 -
o
W o
00 +
-------
3.4 SENSITIVITY ANALYSES
the inputs and outputs from fuel production and electricity generation processes affect each of
the impact categories evaluated in this study.
Table 3-60 shows the baseline impact results and the revised impact results based on the
modified glass energy inputs. The overall life-cycle impact results are highly sensitive to the
energy consumption values from glass manufacturing. Under the modified glass energy
scenario, the nonrenewable resource use, global warming, photochemical smog, BOD, TSS,
chronic occupational health effects, and odor impact categories reversed direction such that the
LCD had greater impacts within each impact category than the CRT in the overall life cycle.
Note that the percent change in CRT results in most impact categories is much greater than that
of the corresponding LCD results. This is because the CRT uses approximately ten times more
glass than the LCD and therefore, the CRT results are much more sensitive to the glass
manufacturing data than are the LCD results.
Table 3-60. Baseline and sensitivity analysis results — modified glass energy
Impact category
Renewable resource use
Nonrenewable resource use
Energy use
Solid waste landfill use
Hazardous waste landfill use
Radioactive waste landfill use
Global warming
Ozone depletion15
Photochemical smog
Acidification
Air particulates
Water eutrophication
BOD
TSS
Radioactivity
Chronic health effects, public
Chronic health effects,
occupational
Aesthetics (odor)
Aquatic toxicity
Terrestrial toxicity
Units/Monitor
kg
kg
MJ
m3
m3
m3
kg-CO2 eq.s
kg-CFC-11 eq.s
kg-ethene eq.s
kg-SO2 eq.s
kg
kg-phosphate eq.s
kg
kg
Bq
tox-kg
tox-kg
m3
tox-kg
tox-kg
CRT
Baseline
1.31e+04
6.68e+02
2.08e+04
1.67e-01
1.68e-02
2.00e-04
6.95e+02
2.05e-05
1.71e-01
5.25e+00
S.Ole-Ol
4.82e-02
1.95e-01
8.75e-01
3.85e+07
1.98e+03
9.34e+02
7.58e+06
2.25e-01
1.97e+03
Glass
energy
2.67e+03
2.35e+02
3.02e+03
1.236-01
1.54e-02
2.00e-04
5.23e+02
1.97e-05
5.59e-02
4.02e+00
1.72e-01
4.10e-03
7.00e-03
2.06e-02
3.16e+07
1.97e+03
2.30e+02
1.09e+04
2.18e-01
1.97e+03
%
change
-79.6%
-64.8%
-85.5%
-26.0%
-8.13%
0.12%
-24.8%
-3.75%
-67.3%
-23.4%
-42.9%
-91.5%
-96.4%
-97.6%
-17.9%
-0.56%
-75.4%
-99.9%
-3.07%
-0.42%
LCD
Baseline
2.80e+03
3.64e+02
2.84e+03
5.43e-02
3.60e-03
l.OOe-04
5.93e+02
1.37e-05
1.41e-01
2.96e+00
1.15e-01
4.96e-02
2.83e-02
6.15e-02
1.22e+07
9.02e+02
6.96e+02
5.04e+06
5.19e+00
8.94e+02
Glass
energy3
2.43e+03
3.49e+02
2.04e+03
5.27e-02
3.60e-03
l.OOe-04
5.87e+02
1.37e-05
1.37e-01
2.92e+00
1.10e-01
4.80e-02
2.16e-02
3.09e-02
1.22e+07
9.01e+02
6.63e+02
4.79e+06
5.19e+00
8.94e+02
%
change
-13.4%
-4.14%
-28.0%
-2.82%
-1.35%
0.01%
-1.01%
-0.18%
-2.84%
-1.45%
-3.97%
-3.17%
-23.8%
-49.7%
0.00%
-0.02%
-4.74%
-4.99%
0.01%
-0.01%
a Bold indicates impact category indicator that reversed direction from the baseline scenario such that the LCD
indicator is now greater than the CRT.
b LCD impacts in this category are greater than CRT impacts when phased out substances are removed from the
inventories (see Section 3.3.6).
The energy impacts for the baseline and modified glass energy scenarios are presented in
Figure 3-26. In the baseline scenario, over 18,000 MJ of energy were consumed per CRT
monitor during manufacturing. Almost 83% of this was from the glass/frit process group,
mainly from glass manufacturing energy alone. When the glass energy inputs are reduced under
the modified scenario, total energy use in the CRT manufacturing stage decreases some 97% to
just under 500 MJ, and the use stage dominates the overall life-cycle energy impacts at
3-103
-------
3.4 SENSITIVITY ANALYSES
approximately 2,300 MJ per functional unit (i.e., per monitor). The 97% decrease in
manufacturing stage energy use is due to the reduced glass manufacturing fuel inputs and the
consequent reduction in energy inputs to the fuel production process.
^ Energy use impacts
w
2.00E+04 n S
| 1.50E+04 -
C l.OOE+04 -
1 5.00E+03 -
H? O.OOE+00 -
-5.00E+03 -
1 0 OONo^;^ cn^oooo ^ \6
m 1 1 1 rr^ 1 1 i ^n
n Up stream
• Mfg.
QUse
QEOL
] 8.53E+02
-8.44E+01
Baseline Mod.Gass Energy Baseline Mod. Glass Energy
CRT 0 . LCD
Scenario
Figure 3-26. Energy impacts: baseline and modified glass energy
sensitivity results
The modified glass energy scenario has a lesser, but still significant, effect on the
distribution of LCD energy impacts across life-cycle stages. Under the sensitivity scenario, the
LCD manufacturing stage energy consumption is reduced 55% from 1,440 MJ per monitor to
about 640 MJ per monitor, and the use stage becomes the biggest energy consumer at about 850
MJ per monitor.
Global warming is one of the impact categories in which the CRT has the greater impacts
than the LCD under the baseline scenario, but the LCD has the greater impacts under the
sensitivity analysis. Figure 3-27 shows the global warming impacts for both monitor types under
the baseline and modified glass energy scenarios. Under the latter scenario, CRT global
warming impacts in the manufacturing stage are reduced some 85%, but LCD impacts are only
reduced 2.5%. Again, this illustrates the greater sensitivity of CRT impact results to glass
energy inputs. Also, as discussed in Section 3.3.5, a large part of LCD global warming impacts
are driven by sulfur hexafluoride emissions from LCD monitor/module manufacturing, which are
unaffected by the revised glass energy scenario.
3-104
-------
3.4 SENSITIVITY ANALYSES
^ 5.00E+02 n
'3
13
.3 3.00E+02 -
"5
§ 2.00E+02 -
I
-« l.OOE+02 -
H
O
** 0 OOE+00
?
«
9
s _
+
w
"
m 1
,— J
1 1
g Global warming
r+T
-------
3.4 SENSITIVITY ANALYSES
occupational health effects) increase by more than 10%. As expected, life-cycle energy impacts
are the most affected by this sensitivity analysis, due to the increased fuel consumption during
manufacturing. However, under this scenario, none of the impact category results reversed
direction from the baseline such that the LCD now has greater impacts than the CRT or vice
versa, where the baseline LCD impacts were greater than the CRT.
Table 3-61. Baseline and sensitivity analysis results—LCD modified module energy
Impact category
Renewable resource use
Nonrenewable resource use
Energy use
Solid waste landfill use
Hazardous waste landfill use
Radioactive waste landfill use
Global warming
Ozone depletion"
Photochemical smog
Acidification
Air particulates
Water eutrophication
BOD
TSS
Radioactivity
Chronic health effects,
occupational
Chronic health effects, public
Aesthetics (odor)
Aquatic toxicity
Terrestrial toxicity
Units/Monitor
kg
kg
MJ
m3
m3
m3
kg-CO2 eq.s
kg-CFC-lleq.s
kg-ethene eq.s
kg-SO2 eq.s
kg
kg-phosphate eq.s
kg
kg
Bq
tox-kg
tox-kg
m3
tox-kg
tox-kg
CRT
Baseline
1.31e+04
6.68e+02
2.08e+04
1.67e-01
1.68e-02
2.00e-04
6.95e+02
2.05e-05
1.71e-01
5.25e+00
3.01e-01
4.82e-02
1.95e-01
8.75e-01
3.85e+07
9.34e+02
1.98e+03
7.58e+06
2.25e-01
1.97e+03
LCD
Baseline
2.80e+03
3.64e+02
2.84e+03
5.43e-02
3.60e-03
l.OOe-04
5.93e+02
1.37e-05
1.41e-01
2.96e+00
1.15e-01
4.96e-02
2.83e-02
6.15e-02
1.22e+07
6.96e+02
9.02e+02
5.04e+06
5.19e+00
8.94e+02
Mod. energy
2.78e+03
4.06e+02
4.68e+03
5.47e-02
3.60e-03
l.OOe-04
6.17e+02
1.37e-05
1.61e-01
3.00e+00
1.19e-01
4.96e-02
2.83e-02
6.13e-02
1.22e+07
7.66e+02
8.82e+02
5.04e+06
5.19e+00
8.74e+02
% change
-0.69%
11.4%
64.9%
0.74%
-0.01%
-3.88%
4.05%
-0.26%
13.7%
1.48%
3.85%
0.00%
-0.12%
-0.30%
-0.09%
10.1%
-2.14%
0.01%
0.02%
-2.25%
a LCD impacts in this category are greater than CRT impacts when phased out substances are removed from the
inventories (see Section 3.3.6).
Figure 3-28 presents the LCD baseline and sensitivity analysis results for the energy use
impact category, the category with the greatest percent change from the baseline to the modified
LCD module energy scenario. Under this scenario, LCD energy use impacts in the
manufacturing stage increased almost 230% from 1,440 MJ per functional unit to 3,280 MJ per
functional unit. However, total life-cycle energy use impacts increased only 65%. This
sensitivity analysis did not affect consumption rates outside of the manufacturing stage.
3-106
-------
3.4 SENSITIVITY ANALYSES
3.50E+03 n
^ 3.00E+03 -
§ 2.50E+03 -
1 2.00E+03 -
•-B 1.50E+03 -
u
§ l.OOE+03 -
^ 5.00E+02 -
0 OOE+00
-5.00E+02 -
LCD energy use impacts
1.44E+03 8.53E+02
6.33E+02 1 6.33E+02
| -8.44E+01
i.28E+02
Q Upstream
• Mfg.
QUse
QEOL
8.53E+02
-8.44E+01
Baseline Modified Module Energy
Figure 3-28. Energy use: LCD baseline and modified module energy sensitivity
results
Figure 3-29 shows the effects of the sensitivity analysis on LCD chronic occupational
health effects, another impact category with a relatively large percentage change. As shown in
the figure, the manufacturing stage impact score in this category increased about ten percent,
from 684 tox-kg per monitor to 755 tox-kg per monitor, due to the increase in fuel inputs. The
chronic occupational health effect impacts were less sensitive than energy impacts because
health effects results are calculated using a scoring approach that considers the inherent toxicity
of a chemical instead of a simple loading approach (as is used for energy impacts). No toxicity
data were available for LNG, the input with the greatest change in quantity. Therefore, the LNG
HV is representative of a mean toxicity value.
LCD chronic occupational effects
^ 8.00E+02 -,
'3
3 6.00E+02 -
et
.1 4.00E+02 -
-*^
u
a 2.00E+02 -
u
•* 0. OOE+00 -
H
O
"" -2.00E+02 J
3.59E-01
5.84E+02
Base
3.62E-03
3.59E-01
7.55E+02
fj Upstream
• Mfg.
QUse
DEOL
3.62E-03
-1.94E+00 ' -1.94E+00
line Modified Module energy
Figure 3-29. Chronic occupational effects: LCD baseline and modified module energy
sensitivity results
3-107
-------
3.4 SENSITIVITY ANALYSES
3.4.4 Modified LCD EOL Dispositions Scenario
Finally, because very few desktop LCDs have reached their end of life, and usually only
if they have been damaged in some way, very little is known about the EOL disposition of
LCDs. In the baseline scenario it was assumed that a certain percent of EOL LCDs are
incinerated, recycled, remanufactured, landfilled as solid waste, and landfilled as hazardous
waste. (See Section 2.7.3 and Appendix I for an explanation of how EOL disposition percentages
were determined.) To address uncertainties in the allocation of disposition percentages, this
sensitivity analysis qualitatively evaluates a different set of final disposition numbers, as follows:
• change percent recycled from 15% to 0%,
• change percent remanufactured from 15% to 40%,
• change percent landfilled (solid waste) from 50% to 40%.
• do not change fraction incinerated (15%) or fraction sent to a hazardous waste landfill
Thus, under the modified EOL disposition scenario, recycling and solid waste landfilling
impacts would decrease, remanufacturing impacts would increase, and incineration and
hazardous waste landfilling impacts would not change. However, in attempts made to obtain
remanufacturing data, it was found that remanufacturing processes spanned a wide range of
activities, from as little as replacing button tops to as extensive as testing and replacing PWBs or
transformers. Given the broad range of possibilities, and because few desktop LCDs have
reached their end of life, no single set of operations could be identified to adequately represent
remanufacturing activities that could be incorporated in our model. Remanufacturing data were,
therefore, excluded from the assessment.
As shown in the baseline LCIA results (Section 3.3), LCD EOL dispositions have little
effect on overall life-cycle impacts under the baseline scenario. In fact, the only impact
categories in which an EOL process was a top contributor to overall impacts were the hazardous
waste landfill use impact category, where the portion of a monitor landfilled contributed 97% of
impacts, and the solid waste landfill use category, where the portion of a monitor landfilled
contributed 3.5% of impacts. As noted above, hazardous waste landfill use impacts would not
change under the modified LCD EOL dispositions scenario, but solid waste landfill impacts
would be expected to decrease slightly. In a preliminary quantitative analysis of this scenario,
LCD life-cycle solid waste landfill impacts were found to decrease less than one percent, and
life-cycle impacts in other impact categories decreased less than 0.1%. Thus, the modified LCD
EOL dispositions scenario would have only a minor effect on LCD life-cycle impacts and would
not change comparative CRT and LCD results.
3.4.5 Summary of CRT and LCD Sensitivity Analysis Results
The results of the sensitivity analyses are useful to manufacturers who want to
understand how uncertainty in the inventory affects impacts. This information can be used to
identify areas for additional study or potential improvement opportunities. As discussed in
Sections 3.4.1 through 3.4.2, it appears that CRT life-cycle impacts are highly sensitive to the
glass energy data, and less sensitive to the lifespan assumptions (lifespan assumptions greatly
3-108
-------
3.4 SENSITIVITY ANALYSES
affect the magnitude of CRT life-cycle impacts, but they do not greatly affect the distribution of
impacts among life-cycle stage). LCD impacts are less sensitive to the glass energy data and in
fact are not greatly affected by any of the sensitivity analysis scenarios, except the longer
lifespan under the manufactured life scenario.
Sensitivity results are also useful to interested members of the public who may be
evaluating the relative impacts of different monitor types and are interested in whether the CRT
or LCD has greater life-cycle impacts in any given impact category. Table 3-62 presents the
monitor type with greatest impacts by impact category and by scenario. This information helps
us determine whether major assumptions (e.g., the monitor lifespan and LCD EOL distribution
assumptions) or uncertain data (e.g., glass energy data and LCD monitor manufacturing energy)
are driving results. As shown in the table, the modified glass energy scenario is the only
scenario that significantly changes the results from the baseline CRT and LCD comparative
results. Under this scenario, life-cycle impact results in seven categories reverse direction from
the baseline assessment, such that the LCD has greater impacts than the CRT. Therefore, under
this scenario, a total of nine out of 20 categories are greater for the LCD than the CRT, compared
to two out of 20 categories under the baseline scenario. The only other scenario that affects
these results is the manufactured life scenario, when impacts in the water eutrophication
category are greater for the CRT than the LCD.
Table 3-62. Summary of CRT and LCD LCIA results
Impact category
Renewable resource use
Nonrenewable resource use
Energy use
SW landfill use
HW landfill use
RW landfill use
Global warming
Ozone depletion b
Photochemical smog
Acidification
Air particulates
Water eutrophication
Water quality, BOD
Water quality, TSS
Radioactivity
Chronic health effects,
occupational
Chronic health effects, public
Aesthetics (odor)
Monitor type with greatest impacts by scenario
Baseline
CRT
CRT
CRT
CRT
CRT
CRT
CRT
CRT
CRT
CRT
LCD
CRT
CRT
CRT
CRT
CRT
CRT
Manu-
factured
life
CRT
CRT
CRT
CRT
CRT
CRT
CRT
b b
CRT
CRT
CRT
CRT
CRT
CRT
CRT
CRT
CRT
CRT
Modified
glass
energy
CRT
LCD
CRT
CRT
CRT
CRT
LCD
b b
LCD
CRT
CRT
LCD
LCD
LCD
CRT
LCD
CRT
LCD
Modified
LCD
module
energy
CRT
CRT
CRT
CRT
CRT
CRT
CRT
CRT
CRT
CRT
LCD
CRT
CRT
CRT
CRT
CRT
CRT
Modifed
LCD EOL
distribution"
CRT
CRT
CRT
CRT
CRT
CRT
CRT
CRT
CRT
CRT
LCD
CRT
CRT
CRT
CRT
CRT
CRT
3-109
-------
3.4 SENSITIVITY ANALYSES
Table 3-62. Summary of CRT and LCD LCIA results
Impact category
Aquatic toxicity
Terrestrial toxicity
Monitor type with greatest impacts by scenario
Baseline
LCD
CRT
Manu-
factured
life
LCD
CRT
Modified
glass
energy
LCD
CRT
Modified
LCD
module
energy
LCD
CRT
Modifed
LCD EOL
distribution3
LCD
CRT
a Based on a qualitative evaluation, not quantitative results.
b CRT impacts are greater than LCD impacts in this category when all data are included in the inventories, including
data for substances that have been phased out. However, LCD impacts are greater than CRT impacts when phased
out substances are removed from the inventories (see Section 3.3.6).
3-110
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Roenning, T. Ekvall. 1995. Nordic Guidelines on Life-Cycle Assessment. Copenhagen:
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4. QUALITATIVE RISK SCREENING OF SELECTED MATERIALS
Chapter 4
QUALITATIVE RISK SCREENING OF SELECTED MATERIALS
The scope of the DfE CDP, as presented in Chapter 1, was to first conduct an
environmental life-cycle assessment (LCA) to evaluate a generic 17" CRT and 15" LCD desktop
computer display, followed by a streamlined Cleaner Technologies Substitutes Assessment
(CTSA), which would target specific materials or processes that warrant further evaluation.
Traditionally, the DfE Program has conducted CTSAs that perform detailed risk
characterizations of alternative chemical processes. The streamlined CTSA for the CDP takes a
more detailed look than the LCA at the toxic effects of chemicals used in a process, without
conducting a complete risk characterization typical of past CTSAs.
In order to provide meaningful and timely results, the CDP Core group agreed to select a
few materials that are of interest to EPA and industry and conduct analyses concurrently with the
LCA, instead of conducting a CTSA on selected materials or processes after the LCA results
were presented. The LCA identifies material inputs and outputs and then characterizes them in a
life-cycle impact assessment (LCIA). In the human and environmental health effects impact
categories, these input and output amounts are used as surrogates for exposure. For the selected
materials, the additional CTSA-related analyses are intended to better understand the potential
exposures to selected materials, during any processes that use thee materials, in order to try to
better understand potential chemical risks.
The materials that were selected for further analysis were lead, mercury, and liquid
crystals. The justification for choosing these materials, and a brief description of the scope are
provided below:
• Lead: Lead is a top priority toxic material at the U.S. EPA. Lead is found in glass
components of CRTs, as well as in electronics components (printed wiring boards and
their components) of both CRTs and LCDs. The electronics industry is also concerned
with lead and continues to take steps to reduce the use of lead in electronics products.
Lead has been extensively studied for its toxic effects and has been addressed elsewhere
with regard to CRTs and electronics (ATSDR, 1999). Therefore, within the scope of the
CDP, lead is recognized as a material of concern, but extensive evaluation beyond the
LCA is not conducted. Some discussion of the potential for exposure is included in this
chapter, but it references existing studies for further information.
• Mercury: Another top priority toxic material at the U.S. EPA is mercury. The
fluorescent tubes that provide the source of light in the LCD contain mercury. Although
very small amounts of mercury are found in the LCD backlights, EPA's concern with
mercury and the potential for exposure during manufacturing and end-of-life processes
are reasons why a more detailed analysis of mercury is warranted in the CDP. In
addition, mercury is emitted from some fuel combustion processes, such as coal-fired
electricity generation processes, and there is interest in the relative magnitude of mercury
emissions from these sources as compared to the magnitude of mercury emissions from
its intentional use in LCD backlights. Another reason for including mercury is to begin to
do an improvement assessment, because there appear to be potential alternatives to
backlights with mercury.
4-1
-------
4. QUALITATIVE RISK SCREENING OF SELECTED MATERIALS
• Liquid crystals: The toxicity of the liquid crystals in LCDs has been alluded to in the
literature and there is a need to better understand the toxicity of these materials as well as
provide the appropriate context of potential exposure and any associated risk. For
example, during normal use of a display, no exposure would be expected. Liquid crystals
are generally organic materials in broad categories such as polycyclic aromatic
hydrocarbons (e.g., phenylcyclohexanes, biphenyls) (EIAJ, 1996). By including liquid
crystals in a more detailed analysis, this chapter attempts to better characterize any
potential hazard and/or potential exposure of liquid crystals from the manufacturing, use,
and disposal of LCD monitors.
Choosing these three materials as a priority does not presume that these are the only
materials of importance and worthy of additional analyses. The results of the LCI and LCIA in
Chapters 2 and 3 provide more information on where to focus additional analysis efforts or
improvements. Chapter 5 also identifies some potential improvement opportunities.
Sections 4.1 through 4.3 present the qualitative risk screening of lead, mercury, and liquid
crystals, respectively. Subsections in each section briefly describe the following:
• The use of the materials in computer displays: These subsections describe how the
materials are used in computer displays and give information on the mass used in
particular applications.
• Life-cycle inputs and outputs of the materials from computer displays: The life-cycle
assessment approach not only focuses on the material contained within the product, but
also emphasizes the environmental impacts of material inputs and outputs from every
life-cycle stage. These subsections summarize the life-cycle inputs and outputs of the
materials found in the CDP life-cycle inventories (LCIs).
• Life-cycle impacts associated with the material inputs and outputs: As discussed in
Chapter 3, life-cycle impact assessment (LCIA) is a screening-level evaluation of
potential impacts to any system (e.g., the environment) as a result of some action (e.g., a
chemical release). In the LCIA, life-cycle inventory data were classified into various
impact categories (e.g., greenhouse gases or ozone depletion) based on the characteristics
of the inventory item. Characterization methods were then used to quantify the
magnitude of the contribution the emission or consumption of the inventory item could
have in producing the associated impact. The result is expressed as an impact score
which has been calculated using specific impact assessment tools. These subsections
summarize the CDP LCIA results for lead, mercury, and liquid crystal inputs and outputs.
• Potential exposures to the material including occupational, public, and ecological
exposures: Toxic materials may pose a threat to human health anytime there is the
potential for human exposure throughout the life cycle of a computer display. Exposure
occurs anytime a chemical or physical agent comes into contact with an organism, be it
human or ecological. The magnitude of exposure depends on the concentration of the
chemical at the contact point, and the duration and frequency of the exposure. The
concentration of the chemical at the contact point is influenced by several factors,
including the type, quantity, and disposition (e.g., airborne, surface water) of the initial
release, and the subsequent environmental fate of the chemical (the ultimate disposition
of the chemical as it is transported through the environment). Note that exposure is often
defined in terms of exposure pathways. An exposure pathway describes the route a
4-2
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4. QUALITATIVE RISK SCREENING OF SELECTED MATERIALS
contaminant travels from its source to an individual. A complete exposure pathway
consists of the source and mechanism of release, transport medium, point of potential
human contact, and the exposure route (e.g., inhalation, ingestion, dermal contact). These
subsections focus on identifying potential exposures for three groups: workers in facilities
using the chemicals (occupational exposures), the general public, who may be exposed to
releases of the chemicals into the ambient environment, and ecological populations.
While a quantitative exposure assessment is beyond the scope of this study, a qualitative
discussion of potential pathways of exposure is presented for each of the groups listed
above.
Potential human health effects: Human health effects can include acute effects from
short-term exposure, as well as chronic effects from repeated, long-term exposure. To be
consistent with the scope of the LCIA, these subsections focus on chronic effects,
including noncancer and cancer effects, unless no chronic toxicity data are available.
U.S. environmental regulations for the material: These subsections briefly summarize
U.S. environmental regulations that may affect facilities that manufacture materials for
the computer display or are otherwise affected by the life cycle of computer displays (e.g.,
disposal facilities). They do not summarize environmental regulations from other
countries where displays or display components are manufactured, which may differ
significantly from U.S. regulations.
Alternatives to reduce the use of the material in computer displays: These subsections
identify alternatives that can substitute for a material, or, in some cases, source reduction
methods to reduce the use of a material. The discussion of alternatives presented here is
not a rigorous evaluation of their performance, cost, and environmental attributes, but
rather a summary of the current knowledge base that may be useful for manufacturers
seeking to identify improvement opportunities.
In Section 4.4, summary information and conclusions are presented.
4-3
-------
4.1 LEAD
4.1 LEAD
Lead and/or lead compounds are present in both CRTs and LCDs. Because lead and lead-
containing compounds have long been known to pose a threat to both human health and the
environment, this section presents a more detailed look at the use of lead in computer displays
and its effects on human health and the environment.
4.1.1 Lead in Computer Displays
Lead is a significant material in current CRTs, accounting for up to 8% of the overall
composition of the CRT by weight (Menad, 1999), with a 17" monitor containing as much as
1.12 kg of lead (Monchamp et. al., 2001). Lead is used in several parts of the CRT monitor,
including the funnel and neck glass, the sealing frit, as solder on printed wiring boards (PWBs)
within the monitor, and sometimes in the front panel glass of the CRT. Lead is not as prevalent
in LCDs, only being found on PWBs.
Lead, in the form of lead oxide, lines the inner surface of both the neck and funnel glass
of the CRT, or may in some cases be contained within the glass itself. The lead oxide layer acts
as a shield, protecting users from x-ray emissions given off by the electron gun. The lead oxide
layer can comprise as much as 28% by weight of the funnel (Lee et al, 2000) and 32% of the
neck (Menad, 1999).
The sealing frit, which is used to make a vacuum-tight connection between the funnel and
the front panel, is comprised of as much as 80% lead oxide (Busio and Steigelmann, 2000). The
lead oxide is mixed with boric oxide and zinc oxide, along with several other compounds, into a
paste. The glass frit paste is applied as a bead around the top of edge of the funnel and allowed
to dry. The front panel is then attached to the funnel and fired using a belt furnace for 30 to 60
minutes at typical temperatures of 450°C (Busio and Steigelmann, 2000). The lead, boric, and
zinc oxides devitrify to form large crystals which give strength to the frit seal (Techneglas, 2001).
Recent research has been directed at either reducing the lead content of the frit or reducing the
energy required to fuse the frit.
Printed wiring boards found in both LCDs and CRTs primarily use a lead-based solder as
a surface finish and to attach electrical components to the circuit board. Solder is typically
comprised of 37-40% lead. Depending on the type of component, parts can be applied using a
solder paste which is subsequently melted, or by passing the boards over a wave of molten
solder. Data collected for the life-cycle inventory indicates that a 17" monitor has approximately
51 grams of solder, or just under 19.8 grams of lead, while a 15" LCD panel contains nearly 22.4
grams of solder, or just about 8.5 grams of lead. Several lead-free solder alternatives are
currently being tested and are in limited use. Solder is the only significant source of lead in
LCDs.
The CRT panel glass itself may also contain a small percentage of lead oxide, typically
ranging up to 4% by weight (Lee et al., 2000). The lead acts as a stabilizer for the glass during
its formation, and also serves to keep the glass from browning. Lead-free CRT panel glasses are
currently being produced successfully.
A list of the lead-containing parts that make up a computer display, along with the
quantity of lead and percentage of lead in each part, is presented in Table 4-1.
4-4
-------
4.1 LEAD
Table 4-1. Computer display parts that contain lead
Part
Funnel
Front panel
Neck
Frit
PWBs (total)
PWBs (total)
Display type
CRT
CRT
CRT
CRT
CRT
LCD
Quantity
(Kgr
0.91
0.18
0.012
0.026
0.051
0.043
% Lead content of part
(by weight)
22-28% b'c
0-4 b'c
26-32 b'c
70-80 b'c'd
N/A
N/A
a Quantity of lead in a 17" monitor (Monchamp et. al., 2001).
b Menad, 1999.
cLeee?. al., 2000.
dBusio and Steigelmann, 2000.
N/A= Not applicable
4.1.2 Life-Cycle Inventory Inputs and Outputs of Lead for Computer Displays
Data on lead and lead-containing materials were collected and compiled as part of the
life-cycle inventory. Material inputs containing lead included primary materials (e.g., lead-based
solder) which end up as part of the product, as well as from ancillary materials (e.g., lead
consumed during the production of steel used to make CRT parts) which are consumed as part of
the manufacturing process or other supporting processes, such as energy production. The data
were aggregated by material from individual processes and are presented by life-cycle stage for
both CRTs and LCDs in Tables 4-2 and 4-3 below. More detailed material input data, which
include the processes for each input and the quantity of lead released, are included in
Appendix N.
Table 4-2. CRT lead-containing inputs by life-cycle stage
Life-cycle stage
Materials processing
Materials processing
Manufacturing
Manufacturing
Manufacturing
Manufacturing
Manufacturing
Input
Lead (Pb, ore)
Lead (Pb, ore)
Frit
Lead
Printed wiring board (PWB)
Solder (63% tin; 37% lead)
Solder, unspecified - (CRT Assembly)
Quantity
6.50E-05
4.96E-01
6.67E-02
4.94E-01
8.47E-01
5.08E-02
2.67E-02
Units
kg
kg
kg
kg
kg
kg
ks
Type
Ancillary material
Primary material
Primary material
Primary material
Primary material
Primary material
Primary material
4-5
-------
4.1 LEAD
Table 4-3. LCD lead-containing inputs by life-cycle stage
Life-cycle stage
Materials processing
Manufacturing
Manufacturing
Manufacturing
Manufacturing
Input
Lead (Pb, ore)
Printed wiring board (PWB)
Solder (60% tin, 40% lead)
Solder (63% tin; 37% lead)
Solder, unspecified
Quantity
2.47E-05
3.74E-01
3.81E-02
2.24E-02
7.35E-05
Units
kg
kg
kg
kg
ks
Type
Ancillary material
Primary material
Primary material
Primary material
Ancillary material
Material inputs can be raw materials such as lead ore, or output materials from a previous
process or life-cycle stage. For example, small quantities of lead extracted from lead ore are
sometimes used as additives in the production of several materials including ferrite, steel, and
invar. Once extracted, lead is an input material to the manufacturing processes of several CRT
components including CRT glass manufacturing and the manufacturing of the sealing frit paste,
which then is an input for the CRT tube manufacturing process. Similarly, lead is used to
produce solder which is then used to produce PWBs used in LCDs and CRTs.
Releases of lead and lead-based materials into the environment occur throughout the
entire life cycle of the computer display. Environmental releases include airborne, waterborne,
solid waste, and radioactive emissions of lead isotopes associated with nuclear fuel reprocessing.
Similar to the inputs, emissions data were aggregated by the material released from individual
processes and then reported by life-cycle stage. The lead or lead-based material released, the
quantity of the release, the type of release (e.g., waterborne), and the ultimate disposition of the
release all contribute to the environmental impacts.
The life-cycle outputs containing lead for both CRTs and LCDs are shown in Tables 4-4
and 4-5, respectively. More detailed data on lead and lead-based outputs for each process are
presented in Appendix N.
4-6
-------
4.1 LEAD
Table 4-4. Life-cycle lead outputs to the environment from CRTs
Life-cycle
stage
Materials
processing
Materials
processing
Materials
processing
Materials
processing
Manufacturing
Manufacturing
Manufacturing
Manufacturing
Manufacturing
Manufacturing
Manufacturing
Manufacturing
Manufacturing
Manufacturing
Manufacturing
Manufacturing
Manufacturing
Manufacturing
Manufacturing
Manufacturing
Manufacturing
Manufacturing
Manufacturing
Manufacturing
Manufacturing
Use
End-of-life
End-of-life
End-of-life
Output
Lead
Lead
Lead compounds
Lead-210 (isotope)
Broken CRT glass
Broken CRT glass
Cinders from CRT glass mfg (70% PbO)
CRT glass faceplate EP dust (Pb) (D008
waste)
CRT glass funnel EP dust (Pb) (D008
waste)
Frit
Hazardous sludge (Pb) (D008)
Lead
Lead
Lead
Lead (Pb, ore)
Lead compounds
Lead compounds
Lead contaminated grit (D008 waste)
Lead debris (D008 waste)
Lead sulfate cake
Printed wiring board (PWB)
PWB-Solder dross
Sludge from CRT glass mfg (1% PbO)
Waste batch (Ba, Pb) (D008 waste)
Waste finishing sludge (Pb) (D008 waste)
Lead
Lead
Lead compounds
Printed wiring board (PWB)
Quantity
1.66E-03
2.29E-08
1.59E-05
1.02E+00
1.88E-03
1.08E+00
8.26E-03
1.03E-03
5.01E-03
2.99E-03
1.52E-03
1.03E-06
1.30E-05
4.64E-05
4.41E-07
1.62E-05
1.17E-09
3.46E-05
2.14E-04
2.67E-05
3.70E-02
6.70E-02
8.77E-04
1.41E-03
2.56E-04
1.27E-05
1.42E-05
1.60E-09
1.46E-01
Units
kg
kg
kg
Bq
kg
kg
kg
kg
kg
kg
kg
kg
kg
kg
kg
kg
kg
kg
kg
kg
kg
kg
kg
kg
kg
kg
kg
kg
kg
Type
Airborne
Solid waste
Waterborne
Radioactivity
Hazardous waste
Solid waste
Hazardous waste
Hazardous waste
Hazardous waste
Hazardous waste
Hazardous waste
Waterborne
Airborne
Waterborne
Airborne
Waterborne
Waterborne
Hazardous waste
Hazardous waste
Hazardous waste
Solid waste
Hazardous waste
Hazardous waste
Hazardous waste
Hazardous waste
Airborne
Airborne
Waterborne
Hazardous waste
Disposition
Air
Landfill
Surface water
Air
Landfill
R/R
Landfill
Landfill
R/R
Landfill
Landfill
Treatment
Air
Surface water
Air
Treatment
Surface water
Landfill
Landfill
Landfill
R/R
R/R
Landfill
Landfill
Landfill
Air
Air
Surface water
R/R
R/R = recycling/reuse
4-7
-------
4.1 LEAD
Table 4-5. Life-cycle lead outputs to the environment from LCDs
Life-cycle stage
Materials processing
Materials processing
Materials processing
Materials processing
Manufacturing
Manufacturing
Manufacturing
Manufacturing
Manufacturing
Manufacturing
Manufacturing
Manufacturing
Manufacturing
Manufacturing
Use
End-of-life
End-of-life
Outputs
Lead
Lead
Lead compounds
Lead-210 (isotope)
Lead
Lead
Lead (Pb, ore)
Lead compounds
Lead compounds
Printed wiring board (PWB)
PWB-Lead contaminated waste oil
PWB-Solder dross
Waste batch (Ba, Pb) (D008 waste)
Waste CCFL, with lead
Lead
Lead
Lead compounds
Quantity
3.13E-06
5.42E-09
3.68E-06
3.21E-01
8.84E-06
8.33E-07
1.48E-06
5.67E-11
7.14E-06
7.50E-03
5.14E-03
2.96E-02
6.55E-05
8.17E-08
4.76E-06
4.76E-06
4.98E-10
Units
kg
kg
kg
Bq
kg
kg
kg
kg
kg
kg
kg
kg
kg
kg
kg
kg
ks
Type
Airborne
Solid waste
Waterborne
Radioactivity
Airborne
Waterborne
Airborne
Waterborne
Waterborne
Solid waste
Hazardous waste
Hazardous waste
Hazardous waste
Hazardous waste
Airborne
Airborne
Waterborne
Disposition
Air
Landfill
Surface water
Air
Air
Treatment
Air
Surface water
Treatment
Landfill
Treatment
Recycling/
reuse
Landfill
Treatment
Air
Air
Surface water
4.1.3 Computer Display Life-Cycle Impacts for Lead
The life-cycle impacts of lead, lead compounds, and materials containing lead (e.g., lead-
based solder on printed wiring boards) calculated for CRTs and LCDs during the LCIA are
summarized in Tables 4-6 and 4-7 respectively. Impact scores in the table are expressed in units
specific to each impact category (see Chapter 3.1 for a discussion of impact category units and
weighting). The total impact score for each category resulting from lead and lead-based
materials is presented at the bottom of each table.
4-8
-------
4.1 LEAD
Table 4-6. Summary of Lead Impact Scores for CRTs
Life-cycle
stage
Materials
processing
Manufacturing
Use
End-of-life
Material
Lead
Lead (Pb, ore)
Lead compounds
Lead-2 1 0 (isotope)
Broken CRT glass
Cinders from CRT glass mfg (70%
PbO)
CRT glass faceplate EP dust (Pb)
(D008 waste)
Frit
Hazardous sludge (Pb) (D008)
Lead
Lead compounds
Lead contaminated grit (D008
waste)
Lead debris (D008 waste)
Lead sulfate cake
Sludge from CRT glass mfg (1%
PbO)
Waste Batch (Ba, Pb) (D008 waste)
Waste finishing sludge (Pb) (D008
waste)
Lead
Lead
Lead compounds
Total Impact Scores By Category
Impact Scores by Category
Non-
renewable
resource
(kg)
0
4.96e-01
0
0
0
0
0
0
0
4.94e-01
0
0
0
0
0
0
0
0
0
0
9.89e-01
Hazardous
waste
landfill use
(m3)
0
0
0
0
6.22E-07
6.88E-06
2.15E-06
3.04E-06
1.38E-06
0
0
2.99E-09
1.85E-08
3.03E-08
6.45E-07
1.22E-07
2.32E-07
0
0
0
1.52E-05
Solid waste
landfill use
(m3)
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Radio-
activity
(Bq)
0
0
0
1.02E+00
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1.02E+00
Chronic
health
effects-
public
(tox-kg)
3.31e-03
0
3.17E-05
0
0
0
0
0
0
1.19e-04
2.35E-09
0
0
0
0
0
0
2.55E-05
2.85E-05
3.19E-09
3.52e-03
Chronic
health
effects-
occupational
(tox-kg)
0
0
0
0
0
0
0
0
0
9.88e-01
0
0
0
0
0
0
0
0
0
0
9.88e-01
Aquatic
toxicity
(tox-kg)
0
0
3.10e-04
0
0
0
0
0
0
9.3E-05
2.3E-08
0
0
0
0
0
0
0
0
3.1E-08
4.00e-04
Terrestrial
toxicity
(tox-kg)
1.66e-03
0
1.59E-05
0
0
0
0
0
0
5.94E-05
1.17E-09
0
0
0
0
0
0
1.27E-05
1.42E-05
1.6E-09
1.80e-03
4-9
-------
4.1 LEAD
Table 4-7. Summary of lead impact scores for LCDs
Life-cycle
stage
Materials
processing
Manufacturing
Use
End-of Life
Material
Lead
Lead (Pb, ore)
Lead compounds
Lead-210 (isotope)
Lead
Lead compounds
Printed wiring board (PWB)
Waste Batch (Ba, Pb) (D008
waste)
Lead
Lead
Lead compounds
Total Impact Scores By Category
Impact scores by category
Non-
renewable
resource
(kg)
0
2.47E-05
0
0
0
0
0
0
0
0
0
2.47E-05
Hazardous
waste
landfill use
(m3)
0
0
0
0
0
0
0
5.67E-09
0
0
0
5.67E-09
Solid waste
landfill use
(m3)
0
0
0
0
0
0
9.38E-06
0
0
0
0
9.38E-06
Radio-
activity
(Bq)
0
0
0
3.21E-01
0
0
0
0
0
0
0
3.21e-01
Chronic
health
effects-
public
(tox-kg)
6.26E-06
0
7.36E-06
0
1.77E-05
1.13E-10
0
0
9.52E-06
9.52E-06
9.95E-10
5.03E-05
Chronic
health
effects-
occupational
(tox-kg)
0
0
0
0
0
0
0
0
0
0
0
0
Aquatic
toxicity
(tox-kg)
0
0
7.25E-05
0
1.64E-05
1.12E-09
0
0
0
0
9.80E-09
8.9E-05
Terrestrial
toxicity
(tox-kg)
3.13E-06
0
3.68E-06
0
8.84E-06
5.67E-11
0
0
4.76E-06
4.76E-06
4.98E-10
2.52E-05
4-10
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4.1 LEAD
Impact scores for some lead-based inputs and outputs shown in Tables 4-2 though 4-5
were not calculated if the type and disposition of the input or release was not expected to
contribute to any of the impact categories. For example, a waterborne release of lead with a
disposition going to treatment assumed that lead was not yet released to the environment where
impacts could occur, and therefore no impacts were calculated. However, since inventory data
for subsequent disposal processes could not be obtained, it was assumed the lead (or other
inventory item) had been removed to a level such that the subsequent release of treated
wastewater would not contribute significantly to the impact. Similarly, impact scores were not
calculated for releases going to recycling/reuse or for product outputs.
Lead-based impacts from the CRT ranged from moderately to significantly greater
than those from the LCD in every category, with the exception of solid waste landfill use. The
most significant difference was in non-renewable resource consumption, where the CRT (989
grams) consumed over 40 thousand times the mass of non-renewable resources over the course
of its life cycle than those consumed by the LCD (0.025 grams). Hazardous waste landfill use is
another significant difference, with lead-based life-cycle outputs from CRTs using over 2,600
times the space of the lead-based outputs from LCDs. However, the absolute volume of waste
from the CRT is still a relatively small volume (1.50 cm3). Other categories where CRTs had
notably greater impacts as a result of lead include the chronic public health effects and terrestrial
toxicity impact categories.
Based on the CDP LCIA methodology, chronic occupational health effect impacts were
only calculated for lead inputs (excluding lead ore) to processes in the computer display life
cycle. Only the manufacturing life-cycle stage had lead inputs from which impacts were
calculated as shown in Table 4-6. The overall impact scores (0.988 tox-kg for CRT, none for
LCD) likely underestimate the chronic occupational impacts for lead because they do not
consider chronic occupational impacts from other processes such as the mining, smelting, and
refining of the lead, which are known to pose potential occupational exposures (see Section
4.1.4). For a more detailed discussion of how chronic occupational health effect impacts were
calculated, refer to Section 3.1.2.12.
The contribution of lead-based impacts for each computer display technology to the
overall impacts for each individual impact category is shown in Table 4-8. Values in the table
are expressed in the percent contribution the material made to the overall impact score for all
materials (e.g., mercury, fuel oil, glass) for each category. The percent contributions give an
indication of the importance of lead-based impacts relative to the life-cycle impacts from other
materials or outputs from the computer display.
4-11
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4.1 LEAD
Table 4-8. Summary of percent contributions from lead-based materials
to individual impact categories
Impact category
Non-renewable resource
Hazardous waste landfill use
Solid waste landfill use
Radioactivity
Chronic health effects- public
Chronic health effects- occupational
Aquatic toxicity
Terrestrial toxicity
CRT
1.48E-01 %
8.99E-02 %
NA
2.70E-08 %
1.80E-04 %
1.10E-01%
1.96E-01 %
8.90E-05 %
LCD
6.78E-06 %
1.57E-04%
1.73E-02%
2.63E-06 %
5.58E-06 %
N/A
1.71E-03 %
2.82E-06 %
N/A= Not applicable
It can be seen from Table 4-8 that the contributions of lead-based impacts are not
significant relative to the total impacts from other materials (e.g., glass, copper wire, electronic
components) in each category. Impacts from lead-based CRT outputs in the categories of
nonrenewable resources, aquatic toxicity, and chronic public health effects are all range from
0.1-0.2% of the overall impact scores in each category.
4.1.4 Exposure Summary
Lead may pose a threat to human health anytime there is the potential for human
exposure to the lead throughout the life cycle of a computer display. Exposure occurs anytime a
chemical or physical agent, in this case lead or lead compounds, comes into contact with an
organism, be it human or ecological. This section qualitatively identifies potential
exposures for three groups: occupational workers in facilities using lead (occupational
exposures), the general population living nearby these facilities which may be exposed to lead
releases into the ambient environment, and ecological populations in the area surrounding a
facility.
4.1.4.1 Occupational exposures
Workers are typically exposed to far greater concentrations of chemicals for longer
periods of time than other populations. Worker exposures to lead can be especially serious given
the overall toxicity of lead and lead compounds. As a result, both employers and government
agencies have adopted recommendations or requirements for employers who wish to limit
worker exposures.
Occupational exposures can occur anytime a worker comes into contact with lead,
whether it be through dermal (skin) contact with a part containing lead (e.g., lead oxide coating
on glass funnel), through the inhalation of lead particulates dispersed into the air, or through the
inadvertent ingestion of lead. Many of the primary and support processes required to
manufacture computer displays have lead in the workplace, and correspondingly, the potential
for worker exposure. The processes associated with lead inputs and outputs throughout the
computer displays' life cycles are presented in Tables N-l through N-4 in Appendix N. It is
important to note that while this list gives an indication of where likely lead exposures may
occur, it is not exhaustive. Many processes and subprocesses may be contained within a process
listed, each of which may pose its own potential for occupational lead exposures.
4-12
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4.1 LEAD
Exposures to lead are more likely to occur during the extraction, manufacturing, and
disposal life-cycle stages of a computer display. During the use of the computer display,
potential exposures to lead are unlikely as the components containing the lead are contained
within the outside shell of the computer display, limiting the opportunity for contact with
consumers. Table 4-9 presents some typical pathways leading to the occupational exposure of
workers to lead over the life cycle of a computer display.
Table 4-9. Potential occupational exposure pathways for lead over the
life cycle of a computer display
Exposure route
Inhalation
Dermal
Ingestion
Transport
media
Air
Air
Air
Direct contact
Direct contact
Air
Example mechanisms of exposure
Lead fumes resulting from the vaporization of lead during smelting
Lead oxide dust released to the air during lead frit manufacturing
Lead aerosols created during the aeration of tin/lead solder plating baths
during PWB production
Handling of leaded CRT glass funnels prior to assembly
Consumption of food eaten with lead-contaminated hands (or drinking,
smoking, etc)
Ingestion of lead contaminated soil particles which become airborne
during lead mining
Workers may be exposed to airborne lead concentrations through the release of lead dust,
fumes, or aerosols into the workplace. The lead is transported by the air, where it is inhaled into
the lungs and then absorbed into the bloodstream. The greatest potential for high-level
occupational exposure is during lead smelting and refining, where lead is vaporized during high
temperature heating resulting in the release of lead fumes and small respirable particles of lead
(EPA, 1986). Lead concentrations in air at three primary lead smelters were found to range from
80-2,900 |ig/m3, peaking at a level 58 times the OSHA recommended guidance level of 50 |ig/m3
(HSDB, 2001). Another study found that during the smelting and refining of lead, mean
concentrations of lead in air reached as high as 4,470 |ig/m3, nearly 90 times the OSHA guidance
level (Fu and Bofetta, 1995). Exposures to lead dust may also occur during lead mining, frit
manufacturing, CRT glass manufacturing, or processes in which metallic lead is heated in the
presence of air. Exposures to lead fumes are only possible during high temperature operations
(above 500°C), such as welding or spray coating of metals with molten lead (Sittig, 1985).
Dermal exposures can take place anytime lead or materials containing lead are physically
handled by workers. Opportunities for dermal exposures to lead are numerous in processes
throughout the computer display life-cycle, as many processes involve lead or parts containing
lead, especially in CRT manufacturing. Lead can be transferred to the skin of workers through
contact with lead-containing materials and parts. Dermal exposures may also occur during
cleaning and maintenance of equipment used to smelt, refine, or apply lead in a molten state
(e.g., solder wave machinery for PWBs) or in areas with large airborne lead concentrations that
may settle out onto work surfaces directly contacted by workers.
4-13
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4.1 LEAD
The contribution of dermal exposures to the overall lead body burden is uncertain. It is believed
that most forms of lead are unable to readily penetrate the skin, allowing only a small amount of
lead to enter the bloodstream. (ATSDR, 1999). Alkyl lead compounds, which are the known
exception, are primarily used as additives in gasoline and are not used directly in computer
display manufacturing (Bress and Bidanset, 1991; ATSDR, 1999). Therefore, dermal exposures
to inorganic lead compounds are not expected to be as significant as the inhalation or ingestion
routes of exposure (EPA, 1986).
Along with inhalation, ingestion of lead-bearing dust and fumes is a major route of
exposure in lead smelting and refining industries (EPA, 1986). Airborne dust particles of lead
can eventually settle onto skin, equipment, clothing, and work surfaces, where they may be
subsequently transferred to the mouth and become ingested. Airborne particles may also be
inhaled and swallowed, directly when greater than 5 micrometers in size (ATSDR, 1999). Once
ingested, the amount of lead that reaches the bloodstream through the stomach depends on a
number of factors, such as the age of the subject, length of time since last meal, and how well the
lead was able to dissolve in the stomach. Studies have found that roughly 6% of the lead
ingested will absorb into the blood stream of an adult who has recently eaten (within the last
day), while upwards of 60-80% was absorbed in adults who had not recently eaten (ATSDR,
1999).
Lead exposures of workers are frequently measured by biological testing (e.g., blood lead
levels, urinary lead levels) rather than monitoring the workplace for lead concentrations, making
occupational data on lead exposures often not readily available (EPA, 1986). For a discussion of
blood lead levels, corresponding effects, and recommended exposure guidelines, refer to Section
4.1.5 of this chapter.
Blood-lead levels have been reported in studies of workers for several industries relevant
to computer display manufacturing. For example, workers occupationally exposed to lead during
glass production were tested to determine their blood lead levels. Workers were divided into
groups based on work activities and blood samples were collected at the end of each shift.
Concentrations of lead in the blood ranged from 70 to 680 ug/1, with median values ranging from
170 to 340 ug/m3, depending on the worker group. Data on types and rates of exposure were not
identified (Ludersdorf et al, 1987). Another study found that workers producing ceramic coated
capacitors and resistors using leaded glass were exposed to occupational lead levels ranging from
61 to 1,700 ug/m3. Blood lead levels ranged from 16 to 135 ug/dL in these same workers,
greatly exceeding the OSHA recommended level of 50 ug/m3 (Kaye et al, 1987).
The presence of lead in the workplace does not mean that occupational exposures are
unavoidable. Worker exposures to lead can be reduced or even eliminated through the use of
personal protective equipment, sound operating practices, or through advanced machinery that
protects workers from exposure (e.g., an enclosed and vented wave solder machine). To
determine actual worker exposures to lead, a complete exposure assessment specific to each
manufacturing process would be required.
4.1.4.2 General population
The general population living nearby a manufacturing facility using lead may potentially
be exposed to lead emissions from the facility into the surrounding ambient environment. The
likelihood and quantity of the potential exposure is dependent on the type and quantity of release,
the receiving media, the local environmental conditions, and the fate and transport characteristics
4-14
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4.1 LEAD
of the release. General population exposure to lead is most likely to occur through ingestion of
lead contaminated food, water, and soil, as well as through inhalation of lead particulates in the
ambient air (EPA, 1986).
Lead released into the ambient air will typically be in the form of lead particulate matter,
which is eventually removed from ambient air through washout by precipitation (rain or snow) or
through gravitational settling. Estimates indicate that the majority of lead released into the
environment is dispersed into the atmosphere (EPA, 1980). With a relatively small mass mean
diameter of 0.55 um (HSDB, 2001), lead-containing particles can stay aloft for up to 64 hours
and travel 1600 km, though they are more likely to be deposited within 10 km of the emission
source (HSDB, 2001). General populations living near a source of lead emissions may encounter
the lead while it is still airborne, leading to potential inhalation exposure. The direct inhalation
of lead accounts for only a small part of the overall lead exposure to nearby populations,
although the reentrainment of lead-contaminated soil is a common route of exposure (ATSDR,
1999).
Ingestion of lead is the most significant route of exposure for general populations
(ATSDR, 1999). Particulates removed from the air are deposited into the soil, surface water, and
onto local vegetation, where they may be ingested by nearby residents. Grains, vegetables, and
fruits grown in close proximity to a source of lead emissions may contain lead which has been
absorbed from contaminated soil through the root system. Lead also has the ability to
bioaccumulate in the soft tissues of fish and wildlife, which are then consumed by sportsmen and
their families.
Incidental ingestion of soil, which may occur while eating or smoking with soil-coated
hands or when soil becomes reentrained and swallowed directly, often results in the largest lead
exposures to residents living near emission sources. Lead-contaminated soil can also enter the
home by being tracked into the house or carried home from the workplace on clothing, where it
can come into contact with eating surfaces or food and become ingested. A study measuring lead
in the home found mean lead levels as high as 22,191 ug/g in homes located within 1.6 km of a
lead smelting facility, and mean levels of 2,687 ug/g in homes of workers at the smelting facility,
irrespective of distance from the plant (ATSDR, 1999). One study found that once lead is
swallowed, up to 50% of the lead is released from the contaminated soil into the stomach after
only 10 minutes (HSDB, 2001).
Lead may also be released directly to surface water or indirectly to groundwater through
the leaching of lead from landfills. Life-cycle inventory releases to surface water include 464
grams of lead and 159 grams of lead compounds per CRT. Surface water may also become
contaminated through soil deposition or through surface water run-off from contaminated soil.
Groundwater lead contamination from the leaching of lead-contaminated debris from solid- or
hazardous waste disposal sites is unlikely to be significant due to the relative insolubility of lead
(HSDB, 2001). Lead released to both surface waters and groundwater will typically remain
insoluble, forming precipitates and settling into the sediment of the lake or stream. However,
very little lead is typically found in U.S. waters which are used to supply the public with drinking
water, due to strict governmental regulations (0.005 ppm lead) (ATSDR, 1999).
4-15
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4.1 LEAD
4.1.4.3 Ecological populations
Inorganic lead typically does not pose a significant health threat to fish and wildlife
populations, except at extremely high concentrations. Once introduced into surface waters, the
levels of soluble lead depend on the pH of the water and the dissolved salt content. At neutral
pH, inorganic lead typically does not remain soluble in water at high concentrations, forming a
precipitate that ultimately deposits in the sediment. However, as the alkalinity and pH decrease,
the relative soluble concentrations of lead may become higher.
Toxic substances such as lead are capable of concentrating in the tissues of fish and
wildlife. The bioconcentration of lead in fish is low-to-moderate in most species, with a
bioconcentration factor (BCF) of 42 an 45 being reported for two fresh water fish species1.
However, BCFs for certain other species, such as blue mussles (4,985), eastern oysters (1,000+)
and 4 types of fresh water invertebrate species (range of 499 to 1,700), were much higher (EPA,
1999).
4.1.5 Human Health Effects
Lead has been classified by EPA as a persistent biaccumulative toxic (PBT) chemical
(EPA, 200Ib). PBT pollutants are highly toxic, long-lasting substances that can build up in the
food chain to levels that are harmful to human and ecosystem health. Lead's ability to persist in
the environment without breaking down, along with its tendency to bioaccumulate, poses adverse
health effects to birds and mammals at the top of the food chain, along with anyone who
consumes them for food. Lead and lead-based compounds have been associated with a range of
adverse human health effects, including effects on the nervous system, reproductive and
developmental problems, and cancer.
4.1.5.1 Chronic effects (noncancer)
Lead is toxic to human health regardless of the form (Gosselin, 1984). It is one of the
most hazardous of the toxic compounds because the dose of lead is cumulative over a lifetime,
and the health effects are many and severe. Lead has been known to cause hematological,
gastrointestinal, and neurological dysfunction in adults and children. Chronic exposures have
also caused hypertension and reproductive impairment in both men and women, as well as
slowed development in children (Sittig, 1985).
Adverse effects, other than cancer or mutations, are generally assumed to have a dose or
exposure threshold. A reference dose (RfD) is an estimate of the daily exposure through
ingestion to the human population that is likely to be without an appreciable risk of noncancer
detrimental effects during a lifetime. Likewise, a reference concentration (RfC) represents an
estimate of the daily inhalation exposure to the human population that is likely to be without an
appreciable risk of noncancer detrimental effects during a lifetime.
Because of the relative toxicity of lead and the cumulative nature of lead doses, a safe
level of human exposure has yet to be identified by researchers, preventing EPA from
Bioconcentration is defined by EPA as the non-dietary accumulation of chemicals in aquatic organisms
(U.S. EPA, 1999).
4-16
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4.1 LEAD
establishing a RfD or RfC for inorganic lead (ATSDR, 1999). Instead, lead exposure is
determined by using exposure biokinetic models that relate exposure levels to an estimated blood
lead level, which is then compared to actual blood lead levels where adverse effects are known to
occur2. For example, increased blood pressure has been observed in adults with a blood-lead
level as low as 7 ug/dL (ACGIH, 1991). Lead concentrations in excess of 60 ug/lOOg blood
have been associated with neuropathy, gastrointestinal disturbances, and anemia, while workers
with blood-lead levels between 50-70 ug/100 g to have shown decreased neural response
(ACGIH, 1991).
As a guideline, a blood-lead level of concern for adult workers of 30 ug/dL has been
established by both the Occupational Safety and Health Administration (OSHA) and ACGIH. A
guideline of 10 ug/m3 (for a child) has been set by the Center for Disease Control (CDC) for
general population exposures to lead in the ambient environment. A summary of human health
effect guidelines for lead is presented in Table 4-10.
Table 4-10. Human health effect regulations and guidelines for lead
Type
Agency /Category
Regulatory level
Workplace exposures to lead
Worker blood-lead
target/action levels
Pregnant worker:
fetal blood-lead
target/action levels
Workplace air
exposure limit
OSHA, Adults who "wish to bear children"
OSHA, Blood-lead level of concern
OSHA, Medical removal
ACGIH, Biological Exposure Index (BEI) Blood-lead level of
concern (ACGIH, 1998)
NIOSH, level to be maintained through air concentrations
OSHA
CDC
OSHA Permissible exposure limit (PEL)
NIOSH Recommended exposure limit (REL) (NIOSH, 1997)
ACGIH TLV TWA (ACGIH, 1998)
30 ug/dL
40 ug/dL
50 ug/dL
30 ug/dL
60ng/100g
30ng/100g
10 ng/dLa
50 \ig/m3
100 \ig/m3
50 \ig/m3
Ambient environment exposures to lead
Blood-lead
target/action levels for
child
CDC
OSHA
World Health Organization blood-lead level of concern
10 ug/m3 a
30|ig/100g
20 ug/dL
a CDC considers children to have an elevated level of lead if the amount of lead in the blood is at least 10 |ig/dL.
Medical evaluation and environmental remediation should be done for all children with blood-lead levels greater
than 20 |ig/dL. Medical treatment may be necessary for children with a blood-lead concentration above 45 |ig/dL
(RTI, 1999).
Notes: ACGIH: American Conference of Governmental Industrial Hygienists; NIOSH: National Institute for
Occupational Safety and Health; TWA: Time weighted average; TLV: Threshold limit value
In order to estimate blood-lead levels, worker exposure levels based on releases reported in the inventory
would be required. However, without information pertaining to the exposure conditions (which is unavailable to this
study) and fate and transport of the releases, worker exposure cannot be calculated.
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4.1 LEAD
4.1.5.2 Carcinogenicity
The potential for a chemical to cause cancer is evaluated by weight-of-evidence
classifications, specific to the rating organization, which are typically determined by laboratory
or epidemiological studies. Lead and inorganic lead-based compounds have been classified by
the International Agency for Research on Cancer (IARC) as possible human carcinogens (Group
2B), based on sufficient evidence of carcinogenicity in animals (IARC, 1987). Lead has also
been classified as an A3 carcinogen (confirmed animal carcinogen with unknown relevance to
humans) by the American Conference of Governmental Industrial Hygienists (ACGIH, 1998).
The U.S. EPA has given lead a weight-of-evidence classification of B2, indicating lead is a
probable human carcinogen and a confirmed animal carcinogen (IRIS, 1999). There is currently
no established cancer slope factor for lead, which could be used to estimate cancer risk from an
exposure amount.
4.1.6 Environmental Regulations for Lead
Apart from the regulations and recommendations regarding worker safety presented in the
previous section, lead is regulated in a number of ways. This section presents a brief summary of
the U.S. regulations for lead and lead compounds expected to impact facilities that manufacture
materials for the computer display. It should be noted that many of the parts and materials which
go into the manufacture of computer displays are manufactured in countries outside the U.S.,
with their own lead regulations which may differ significantly from those discussed below.
Air emissions of lead are regulated under the Clean Air Act (CAA) of 1970 and the
amendments to the CAA of 1977 and 1990. Under the CAA, lead is regulated as a hazardous air
pollutant (HAP), which is by definition a chemical that is generally known or suspected to cause
serious health problems. Stationary source categories involved in the life cycle of a computer
display that must meet new source performance standards include primary and secondary lead
smelters, glass manufacturing plants, and metallic mineral processing plants (EPA, 1977; EPA,
1980a; ATSDR, 1999). A National Ambient Air Quality Standard (NAAQS) was also
established for lead, requiring that the concentration of lead in air that the public breathes be no
higher than 1.5 ug/m3 averaged over 3 months [40 CFR 50.12].
Lead releases to surface water are regulated under the Clean Water and Effluent
Guidelines and Standards promulgated under the Clean Water Act of 1977. Lead is identified as
a priority pollutant [40 CFR 401.15], requiring the limitation of lead concentrations in pollutant
discharges from point sources. The regulations also set standards of performance for new point
sources, as well as pretreatment standards for both new and established sources. Regulated point
source categories include lead smelters, steam electric power generation, glass manufacturers,
and aluminum production and others, all of which contribute to the life-cycle impacts of a
computer display. New point sources of lead contamination must also apply for National
Pollution Discharge Elimination System (NPDES) permits which will establish effluent limits for
sources of lead discharge.
To protect the population from a contaminated water supply, toxic substances in drinking
water are regulated under the Safe Drinking Water Act of 1986. A federal drinking water
standard of 15 ug/L has been established for lead.
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4.1 LEAD
EPA also regulates lead content in hazardous and solid wastes under the Resource Conservation
and Recovery Act (RCRA). A solid waste containing lead or lead compounds may be considered
a D008 characteristic hazardous waste if, when subjected to a Toxicity Characteristic Leachate
Procedure (TCLP) test, the extract exceeds 5.0 mg/L [40 CFR 261.24] for lead. Other lead-
contaminated wastes may be considered hazardous if specifically listed in 40 CFR 261.30-33,
unless specifically excluded. Listed wastes from specific sources which contribute to the
manufacture of computer displays include emission control dust from steel production and from
lead smelting (K061 and K069 respectively), waste leaching solution of control dust from
secondary lead smelting (K100), and spent baths and residues from electroplating operations
containing cyanide (F006), which are sometimes used in PWB manufacturing. Specific sources
of hazardous wastes, whether characteristic or listed wastes, are subject to handling, storage, and
disposal restrictions detailed in the code of federal regulations.
Manufacturers who emit lead are required to report the quantity of the emissions under
the Community Right-to-Know Act. EPA has recently reduced the reportable quantity threshold
for lead from 10,000 Ibs per year to 100 Ibs per year of lead.
4.1.7 Alternatives to Lead Use in Computer Displays
Because of increasing pressure through regulation and market forces, attempts to reduce
or eliminate lead in electronics have become popular. Several countries are considering or have
already passed restrictions on the use and disposal of lead, prompting many companies to
establish aggressive timelines for reducing or eliminating lead in their products. Several
opportunities to eliminate or reduce the amount of lead used in a computer display are being
aggressively researched. Two options being researched extensively are the development of a
reduced lead frit, and lead-free solders for PWB manufacturing and assembly.
Although not large in mass in a monitor, frit glass is 70 to 80% lead by weight. Lead is
one component of a mixture that crystalizes under intense heat, providing strength to the
vacuum-tight frit seal. An alternative lead-free frit glass has been developed that is based on tin
and zinc oxides, along with phosphate (Busio and Steigelmann, 2000). The lead-free glass is
inherently mechanically weak, requiring large amounts of ceramic fillers (A12O3) to be added to
improve the mechanical strength of the seal. It also requires the addition of vitreous silica
particles to match the thermal expansion requirements of the CRT glass. The resulting mixture
requires a firing cycle approaching 450°C, which is typical of frit glasses. A drawback is that the
frit glasses stay vitreous during the typical 30-60 minute furnace dwell time. However, initial
evidence suggests that the fired frit seal remains rigid during the pumping step, which occurs at
350°C. Although comprehensive test results are not yet available, the high-temperature stability
and rigidity of the lead-free frit glass is currently being tested under vacuum (Busio and
Steigelmann, 2000).
Lead-free solders have been the subject of industry research for some time. Driven by
renewed regulatory attention and by recent corporate commitments to reduce or eliminate lead
from their product lines, alternatives to lead-based solder are garnering increased attention.
Alternative lead-free solders include tin in combination with one or more of the following
metals: silver, copper, bismuth, germanium, and antimony. Several companies, including Sony,
Toshiba, Hitachi, and Ford Motor Company, have either already begun to implement electronics
production using a lead-free solder alternative, or have announced plans to do so. Though still a
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4.1 LEAD
relatively new and untested technology, initial testing has shown that alternatives are capable of
producing quality component connections, though they have a narrower operating window and
require higher temperatures to apply (Keenan and Kellett, 2001).
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4.2 MERCURY
4.2 MERCURY
Mercury is not only used in the manufacturing of LCDs, but also is emitted from a
number of processes over the life cycle of both LCDs and CRTs. Because of mercury's toxicity
to both humans and the environment, this section presents a more detailed look at the uses and
impacts of mercury, and its potential for causing harm as a result of the manufacture, use, and
disposal of computer displays.
4.2.1 Mercury in Computer Displays
Mercury is an important material in the construction of cold cathode fluorescent lamps
(CCFLs) that are used to backlight the LCD. A typical LCD utilizes a minimum of two CCFLs,
and can use as many as eight in larger displays. The CCFL consists of a glass tube filled with a
small amount of rare gas (typically argon) and a few drops of mercury. Metal electrodes built
into the ends of the tube conduct electric current to the inside gas, vaporizing a portion of the
mercury which then becomes excited, emitting light in the ultraviolet spectrum. Fluorescent
phosphors, which coat the inside of the glass tube, convert the ultraviolet emissions from the
mercury gas into visible white light. The phosphors are responsible for nearly all of the visible
light from the lamp, with the visible mercury spectrum contributing only a little to the lamps
output (Srivastava and Sommerer, 1998). No mercury is contained directly within the CRT.
Although a great deal of mercury is obtained by CCFLs, there also is a small source of
mercury generated by the infrequent breakage of mercury lamps in the photolithographic
exposure systems used to make both the CRT and LCD. Mercury filters are used in some water
cooled exposure table equipment to catch the mercury from lamp explosions or trap it in water
cooling baths. In air cooled lamp usage, the proximity of aluminum metal gives sites for
amalgam formation and a number of clean-up procedures are used. Unbroken lamps are returned
to the lamp manufacturer for recycling or disposal (Donofrio and Eckel, 1999).
Mercury may also be emitted from several processes required to manufacture, operate,
and dispose of both CRTs and LCDs. For example, electricity generated from the combustion of
coal results in the emission of mercury contained within the fuel. Other processes potentially
responsible for mercury emissions include mercury ore processing, non-ferrous metal production,
and the recycling of LCDs at the end of their useful life. The amount of mercury released
through these incidental mercury emissions is comparable to the amount of mercury used as a
direct material in the manufacture of LCD backlights.
4.2.2 Life-Cycle Inputs and Emissions of Mercury for Computer Displays
Data on mercury and mercury-containing materials were collected and compiled as part of
the life-cycle inventory. Material inputs containing mercury include primary materials (e.g.,
CCFLs) which end up as part of the product, as well as ancillary materials (e.g., fossil fuels
containing mercury) which are consumed as part of the manufacturing process or other
supporting processes (e.g., energy production). The data were aggregated by material from
individual processes and are presented by life-cycle stage for LCDs in Table 4-11. More detailed
material input data, which include the processes that use each input and the quantity of mercury
releases, are included in Appendix N.
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4.2 MERCURY
Table 4-11. Life-cycle stage mercury inputs for LCDs
Life-cycle stage
Manufacturing
Manufacturing
Inputs
Mercury
Backlight lamp (CCFL)
Quantity
3.99e-06
1.94E-03a
Units
kg
ks
Type
Primary material
Product
a Quantity of release shown represents entire mass of input material. Mercury may only comprise a fraction of the
total mass of material shown.
Mercury is not listed as an input in the life-cycle inventory for CRTs. However, mercury
is contained in raw material inputs (e.g., mercury contaminants in fossil fuels burned to produce
energy) into processes such as non-ferrous metal production and energy production for both
LCDs and CRTs. Though mercury inputs exist, they occur in upstream manufacturing processes
where input data did not contain detailed composition data for fuel inputs.
Releases of mercury and mercury-containing materials into the environment occur
throughout the entire life cycle of the computer display. Environmental releases include
airborne, waterborne, solid waste, and hazardous waste emissions. Similar to the inputs,
emissions data were aggregated by the material released from individual processes and then
reported by life-cycle stage. The mercury and mercury-containing material released, the quantity
of the release, the type of release (e.g., waterborne), and the ultimate disposition of the release all
affect the nature and type of environmental impacts.
The total life-cycle outputs/emissions containing mercury for both CRTs and LCDs are
organized by output type and shown in Tables 4-12 and 4-13, respectively. More detailed data
on mercury and mercury-containing outputs for each process are presented in Appendix N.
Table 4-12. Life-cycle stage mercury outputs from CRTs
Life-cycle stage
Materials processing
Materials processing
Materials processing
Manufacturing
Manufacturing
Use
End-of-life
End-of-life
Outputs
Mercury
Mercury
Mercury compounds
Mercury
Mercury compounds
Mercury
Mercury
Mercury compounds
Quantity
3.00E-06
1.42E-10a
9.68E-07
1.12E-06
1.35E-12
7.51E-06
-1.15E-07
4.33E-11
Units
kg
kg
kg
kg
kg
kg
kg
ks
Type
Airborne
Solid waste
Waterborne
Airborne
Waterborne
Airborne
Airborne
Waterborne
Disposition
Air
Landfill
Surface Water
Air
Surface Water
Air
Air
Surface Water
a Quantity of release shown represents entire mass of waste disposed. Mercury may only comprise a fraction of the
total mass of waste shown.
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4.2 MERCURY
Table 4-13. Life-cycle stage mercury outputs from LCDs
Life-cycle stage
Materials processing
Materials processing
Manufacturing
Manufacturing
Manufacturing
Manufacturing
Manufacturing
Manufacturing
Use
End-of-life
End-of-life
Outputs
Mercury
Mercury compounds
Broken CCFL
Mercury
Mercury compounds
Waste CCFL, with mercury
Waste glass, with mercury
Wastewater stream, from
CCFL mfg.
Mercury
Mercury
Mercury compounds
Quantity
9.44E-07
5.82E-07
2.69E-07a
2.64E-06
6.52E-14
8.17E-10a
1.05E-10a
167
2.80E-06
-8.64E-08
1.62E-11
Units
kg
kg
kg
kg
kg
kg
kg
kg
kg
kg
ks
Type
Airborne
Waterborne
Solid waste
Waterborne
Waterborne
Hazardous waste
Hazardous waste
Waterborne
Airborne
Airborne
Waterborne
Disposition
Air
Surface Water
Landfill
Treatment
Surface Water
Treatment
Landfill
Treatment
Air
Air
Surface Water
a Quantity of release shown for solid waste and hazardous waste represents entire mass of waste disposed. Mercury
may only comprise a fraction of the total mass of waste shown.
Mercury is released into the environment in many forms, but is most typically an airborne
release. The largest air emissions of mercury result from the generation of electricity from fossil
fuel burning. For LCDs, there is nearly the same amount of mercury emitted to the air from
energy production (3.22 mg) as the mass of mercury used in the fabrication of an LCD (3.99 mg).
In fact, the amount of mercury emitted to the air from electricity generation for CRTs (7.75 mg)
is greater than the entire amount of mercury from both the fabrication and energy production for
an LCD. Other airborne releases include the processing of ores such as lead, and the production
of several raw materials such as aluminum, polycarbonate, and steel.
4.2.3 Computer Display Life-Cycle Impacts for Mercury
The life-cycle impacts of mercury, mercury-based compounds, and materials containing
mercury (e.g., waste glass from broken CCFLs) calculated for CRTs and LCDs during the LCIA
are summarized in Tables 4-14 and 4-15, respectively. Impact scores in the table are expressed
in units specific to each impact category (see Chapter 3.1 for a discussion of impact category
units and weighting). The total impact score for each category resulting from mercury and
mercury-based materials is presented at the bottom of each table.
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4.2 MERCURY
Table 4-14. Summary of mercury-based impact scores by impact category for CRTs
Life-cycle
stage
Materials processing
Materials processing
Manufacturing
Manufacturing
Use
End-of-life
End-of-life
Material
Mercury
Mercury compounds
Mercury
Mercury compounds
Mercury
Mercury
Mercury compounds
Total Impact Scores by Category
Impact scores by category
Hazardous
waste landfill
use
(m3)
0
0
0
0
0
0
0
0
Solid waste
landfill use
(m3)
0
0
0
0
0
0
0
0
Chronic
health effects-
public
(tox-kg)
3.00E-06
5.11E-04
1.12E-06
7.13E-10
7.51E-06
-1.15E-07
2.29E-08
5.22E-04
Chronic health
effects-
occupational
(tox-kg)
0
0
0
0
0
0
0
0
Aquatic
toxicity
(tox-kg)
0
9.02E-04
0
1.26E-09
0
0
4.04E-08
9.02E-04
Terrestrial
toxicity
(tox-kg)
3.00E-06
5.10E-04
1.12E-06
7.11E-10
7.51E-06
-1.15E-07
2.28E-08
5.21E-04
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4.2 MERCURY
Table 4-15. Summary of mercury-based impact scores by impact category for LCDs
Life-cycle
stage
Materials
processing
Materials
processing
Manufacturing
Manufacturing
Manufacturing
Manufacturing
Use
End of Life
End of Life
Material
Mercury
Mercury compounds
Broken CCFL
Mercury
Mercury compounds
Waste glass, with
mercury
Mercury
Mercury
Mercury compounds
Total Impact Scores by Category
Impact scores by category
Hazardous
waste landfill
use"
(m3)
0
0
0
0
0
7.73E-15
0
0
0
7.73E-15
Solid waste
landfill use a
(m3)
0
0
1.98E-11
0
0
0
0
0
0
1.98E-11
Chronic health
effects-public
(tox-kg)
9.44E-07
3.07E-04
0
5.54E-07
3.44E-11
0
2.80E-06
-8.64E-08
8.53E-09
3.11E-04
Chronic health
effects-
occupational
(tox-kg)
0
0
0
3.99E-06
0
0
0
0
0
3.99E-06
Aquatic toxicity
(tox-kg)
1.82E-07
5.42E-04
0
1.9387E-07
6.08E-11
0
0
0
1.51E-08
5.43E-04
Terrestrial
toxicity
(tox-kg)
9.44E-07
3.07E-04
0
5.54E-07
3.44E-11
0
2.80E-06
-8.64E-08
8.52E-09
3.11E-04
1 Percentages of impacts shown for solid and hazardous wastes are based on the entire mass of material disposed, not necessarily on the amount of mercury. As
such, the percentage over-estimates the impact of mercury to either the solid or hazardous waste landfill use.
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4.2 MERCURY
Impact scores for some mercury-based inputs and outputs shown in Tables 4-11 through
4-13 were not calculated if the type and disposition of the input or release was not expected to
contribute to any of the impact categories. For example, a waterborne release of mercury with a
disposition going to treatment assumes that the mercury was treated prior to being released to the
environment. However, since inventory data for subsequent treatment/disposal processes could
not be obtained, it was assumed the mercury (or other inventory item) had been removed to a
level such that the subsequent release of treated wastewater would not contribute significantly to
aquatic toxicity impacts. Similarly, impact scores were not calculated for releases going to
recycling/reuse or for those designated as a product.
The life-cycle mercury-based outputs from LCDs had a broader affect on the environment
than those from CRTs, impacting a wider group of impact categories. Impacts to both solid and
hazardous waste landfill use, as well as to the chronic health effects of workers, all directly result
from the use of mercury in the LCD backlights. No mercury is required for the fabrication of a
CRT. Although the quantities are not large (see Tables 4-11 through 4-13), they cannot be
discounted, given the toxicity of mercury to both human health and the environment.
Chronic occupational toxicity impacts were only calculated for mercury inputs to
processes in the CDP. The overall impact scores (3.99E-06 tox-kg for LCD, none for CRT)
likely underestimate the chronic occupational impacts for mercury, because they are based on
inputs only and do not consider chronic occupational impacts from outputs in other processes
such as aluminum production or fluorescent lamp recycling, which may result in emissions of
mercury that originate within the workplace.
The contribution of mercury-based impacts for each computer display technology to the
overall impacts for each individual impact category is shown in Table 4-16. Values in the table
are expressed in the percent contribution the material made to the overall impact score for all
materials (e.g., liquid crystals, fuel oil, glass) for each category. The percent contributions give
an indication of the importance of mercury-based impacts relative to the life-cycle impacts from
other materials or outputs from the computer display.
Table 4-16. Summary of percent contributions from mercury-based materials to
individual impact categories
Impact category
Hazardous waste landfill use
Solid waste landfill use
Chronic health effects- public
Chronic health effects- occupational
Aquatic toxicity
Terrestrial toxicity
CRT
N/A
N/A
2.64E-05
N/A
4.01E-01
2.64E-05
LCD
NA
3.65E-08
3.45E-05
5.80E-07
1.05E-02
3.48E-05
N/A = Not applicable
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The results from Table 4-14 and 4-15 indicate that the mercury impacts from a CRT
exceed the impacts from an LCD in categories common to both technologies. This was not
expected, because mercury is used intentionally in an LCD, but not in a CRT. However, the
results are not surprising because mercury emissions from coal-fired power plants are known to
be one of the largest anthropogenic sources of mercury in the United States. Because the CRT
consumes significantly more electricity in the use stage than the LCD, its use stage emissions of
mercury are proportionately higher than those of the LCD. In fact, the mercury emitted from the
generation of power consumed by the CRT exceeds the entire amount of mercury emissions from
the LCD, including both the mercury used in LCD backlights and the mercury emissions from
electricity generation in the use stage that can be attributed to the LCD.
The impacts resulting from mercury and mercury-based materials do not appear to be
significant relative to the total impacts of all of the computer display materials (e.g., liquid
crystals, lead solder), as shown in Table 4-16. The largest contribution is 0.4% of the total
aquatic toxicity impacts for CRTs, and 0.01% of the total aquatic toxicity impacts for LCDs.
Impacts to other categories from both LCDs and CRTs were minimal.
4.2.4 Exposure Summary
Mercury may pose a threat to human health anytime there is the potential for human
exposure throughout the life cycle of a computer display. Exposure occurs anytime a chemical or
physical agent, in this case mercury or mercury compounds, come into contact with an organism,
be it human or ecological. This section qualitatively identifies potential exposures for workers in
facilities using mercury (occupational exposures), the general public, who may be exposed to
mercury releases into the ambient environment, and the ecological population.
4.2.4.1 Occupational exposures
About 4 mg of elemental mercury (combined total of all mercury contained within the
backlights) is used to manufacture the fluorescent backlight for the LCD backlight unit assembly.
Workers manufacturing the backlights may be exposed to the mercury used for these lights. This
study found no information on the specific manufacturing processes that are used to make CCFLs
or the specific worker exposures that could occur, but did find manufacturing information for
generic fluorescent lamps. We assume the processes are similar and have included a brief
discussion of the fluorescent lamp manufacturing process and potential sources of worker
exposure, below.
In fluorescent lamp manufacturing, pre-cut bulbs are washed, dried, and coated with a
liquid phosphor emulsion that deposits a film on the inside of the bulb. Mount assemblies are
then fused to each end of the bulb and the bulb is transferred to an exhaust machine. The bulb is
then exhausted and mercury is injected into the bulb. Some of the mercury combines with the
emulsion on the interior of the bulb where it remains over the life of the bulb. The glass bulb is
then filled with an inert gas and sealed (EPA, 1997).
During the lamp manufacturing process, emissions of mercury can occur from transfer
and parts repair during mercury handling, by the mercury injection operation, and from broken
lamps, spills, and waste materials. Workers can be exposed to mercury from any of these
sources, but mercury air levels can be reduced by process modifications, containment, ventilated
inclosures, local exhaust ventilation, and temperature control (EPA, 1997).
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4.2 MERCURY
There were no other inputs of mercury reported in the LCD life-cycle inventory, and none
were reported in the CRT life cycle. Workers may also be exposed to inorganic mercury in the
fluorescent backlights when processing LCDs at the end-of-life. Family members of workers
may be exposed as well, from a worker's clothing or shoes if they are contaminated with mercury
and brought home.
The processes associated with LCI mercury inputs and releases are presented in
supplemental tables in Appendix N. It is important to note that while this list gives an indication
of where likely mercury exposures may occur, it is not exhaustive. Many processes and
subprocesses may be contained within a process listed, each of which may pose its own potential
for occupational mercury exposures.
4.2.4.2 General population exposures
Mercury is a persistent biaccumulative toxic (PBT) chemical, as designated by EPA
(EPA, 200Ib). PBT pollutants are highly toxic, long-lasting substances that can build-up in the
food chain to levels that are harmful to human and ecosystem health. The general public may be
exposed to metallic mercury that is not safely contained (although it is unlikely that the backlight
would break to release mercury during normal LCD use) or to methylmercury-contaminated
foods. Mercury also can be passed from a pregnant woman to developing child through the
placenta, and from a mother to nursing infant through breast milk.
Most of the mercury released to the environment throughout the CRT and LCD life cycles
results from electricity generation required for use, manufacturing, and materials processing life-
cycle stages. A total of approximately 4 mg of mercury and mercury compounds are released to
air for an LCD, and approximately 12 mg are released to air for a CRT. Mercury is naturally
present in coal and becomes airborne when coal is burned to generate electricity. Airborne
mercury can stay in the atmosphere for up to a year, and can travel thousands of miles (EPA,
200 la). EPA modeling suggests that "a substantial fraction" of the mercury released to air by
utilities is dispersed "well beyond the local area" due to the fine particulate nature of the
emissions and tall stacks (EPA, 1998). Mercury in the atmosphere moves to land and water by
settling out with particles and being washed out by rain (dry and wet deposition). It may be
deposited directly to water or be carried by runoff to a lake, stream, or ocean. In the LCIs, in
addition to the air releases of mercury, 0.6 mg of mercury and mercury compounds are released
directly to surface water in the LCD life cycle, and 1 mg in the life cycle of the CRT. Ultimately,
at the end of life, the 4 mg of mercury in the LCD backlight will most likely be released to the
environment during LCD recycling or disposal processes.
Surface water is the environmental medium of most concern for mercury. In a surface
water environment, inorganic mercury can be transformed into methylmercury, a form which
readily bioaccumulates in fish (inorganic mercury does not tend to bioaccumulate). An EPA
study of mercury supports a "plausible link" between releases of mercury from industrial and
combustion sources and methylmercury found in fish3 (EPA, 200 Ic). Methylmercury
The mercury released to the environment from the CRT and LCD life cycles are only part of the overall
burden of mercury released to the environment from coal-fired power plants for all uses of electricity. The
proportion of mercury in fish that is due to coal-fired power generation is not known. In addition, there are other
natural and anthropogenic sources of mercury to the environment.
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4.2 MERCURY
concentrations at the top of the food chain (such as in predatory fish or fish-eating animals) can
be thousands or even millions of times greater than that in the surface water itself (EPA, 2000a).
The most important mercury exposures to the general public result from eating fish that
are contaminated with methylmercury. The populations of most concern are children and women
of child-bearing age (the developing fetus may be the most sensitive to the effects of
methylmercury). Also of concern are people whose diet largely depends on fish, such as with
some native cultures. The overall amount of exposure to mercury from eating fish depends on
both the concentration of mercury in the fish, and on the amount offish a person regularly eats.
Fish advisories due to methylmercury contamination have been issued by EPA4, 39 states, and
some tribes, providing consumption limits for certain species offish (EPA, 2000a, 200 Ic).
Freshwater fish are most affected, but some saltwater fish have also been found to be
contaminated with methylmercury. The Food and Drug Administration (FDA) has issued a fish
consumption advisory for pregnant women, nursing mothers, and small children to avoid eating
certain large saltwater fish (shark, swordfish, king mackerel, and tilefish), and to limit overall
weekly fish consumption, due to methylmercury contamination (FDA, 2001).
4.2.4.3 Exposure and effects to ecological populations
In addition to the fish themselves being contaminated, wildlife that eat fish also may be at
risk from exposure to methylmercury. Species of concern include loons, eagles, mink, otter,
wood stork, and the endangered Florida panther. Adverse effects of mercury to wildlife include
death, reproduced reproductive success, impaired growth and development, and behavioral
abnormalities. Levels have been measured in some individual wild animals that are comparable
to those levels seen to cause harmful effects in laboratory tests with the same species (EPA,
200Ic). Ambient water criteria have been developed by EPA under the CWA. Criteria for the
protection of aquatic life for mercury are presented in Table 4-17.
"EPA is issuing a national advisory concerning risks associated with mercury in freshwater fish caught by
friends and family. The groups most vulnerable to the effects of mercury pollution include: women who are pregnant
or may become pregnant, nursing mothers, and young children. To protect against the risks of mercury in fish caught
in fresh waters, EPA is recommending that these groups limit fish consumption to one meal per week for adults (6
ounces of cooked fish, 8 ounces of uncooked fish) and one meal per week for young children (2 ounces cooked fish
or 3 ounces of uncooked fish)." - EPA Office of Water, January 2001
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4.2 MERCURY
Table 4-17. EPA water quality criteria for mercury
Type of criteria
Criteria value (fig/L)
Notes
For protection of aquatic life
Freshwater Criteria Maximum Concentration
(CMC)
Freshwater Criterion Continuous
Concentration (CCC)
Saltwater Criteria Maximum Concentration
(CMC)
Saltwater Criterion Continuous Concentration
(CCC)
1.4a
0.77 a
1.8a
0.94 a
the acute limit for the priority
pollutant in freshwater
the chronic limit for the priority
pollutant in freshwater
the acute limit for the priority
pollutant in saltwater
the chronic limit for the priority
pollutant in saltwater
Source: Water Quality Criteria and Standards, EPA Office of Water. Revised: 06/21/2001
http://oaspub.epa.gov/wqsdatabase/epa.rep_parameter; report for mercury
a Criteria for metals are expressed in terms of the dissolved metal in the water column. This recommended water
quality criterion was derived from data for inorganic mercury (II), but is applied here to total mercury. If a
substantial portion of the mercury in the water column is methylmercury, this criterion will probably be under-
protective (EPA is updating the ambient water quality criteria on methylmercury.) In addition, even though
inorganic mercury is converted to methylmercury and methylmercury bioaccumulates to a great extent, this criterion
does not account for uptake via the food chain because sufficient data were not available when the criterion was
derived.
4.2.5 Human Health Effects
Mercury affects the nervous system, brain, and kidneys. Effects on the nervous system
vary depending on the form of mercury. Inorganic mercury salts, for instance, do not enter the
brain as readily as elemental mercury or methylmercury. Symptoms of mercury effecting the
brain and nervous system include personality changes, tremors, changes in vision such as
narrowing of the visual field, deafness, loss of muscle coordination, loss of sensation, and
problems with memory (ATSDR, 1999).
The fetus, infants, and young children are especially susceptible to the effects of mercury
on the nervous system. As mentioned above, mercury (especially methylmercury in food) can be
passed from a pregnant woman to the unborn developing child, and from a mother to a nursing
infant through breast milk. The developmental effects of mercury vary in severity depending on
the amount of exposure. Children exposed in this way may show small decreases in IQ or may
be slower to walk and talk. More severe effects might include brain damage with mental
retardation, blindness, muscle weakness or seizures, and inability to speak (ATSDR, 1999).
Mercury accumulates in the kidneys and all forms of mercury can cause kidney damage at
higher exposures (ATSDR, 1999). Short term exposure (hours) to high levels of mercury vapor,
as might occur through an accidental spill in the workplace, include damage to the lining of the
mouth, irritated lungs and airways, nausea, vomiting, diarrhea, increased blood pressure or heart
rate, skin rashes, and eye irritation. Skin contact may cause an allergic reaction (skin rashes) in
some people (ATSDR, 1999).
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4.2 MERCURY
4.2.5.1 Chronic effects (noncancer)
A reference dose (RfD) is an estimate (with uncertainty spanning perhaps an order of
magnitude) of the daily exposure through ingestion to the human population (including sensitive
subgroups) that is likely to be without an appreciable risk of deleterious noncancer effects during
a lifetime (in mg/kg-day). Similarly, a reference concentration (RfC) is an estimate (with
uncertainty spanning perhaps an order of magnitude) of the daily inhalation exposure to the
human population (including sensitive subgroups) that is likely to be without an appreciable risk
of deleterious noncancer effects during a lifetime (in mg/m3) (Barnes and Dourson, 1988). RfDs
and RfCs established by EPA for mercury and mercury compounds are presented in Table 4-18.
Table 4-18. Chronic toxicity reference values for mercury and mercury compounds
Form of mercury"
Elemental mercury
(Hg)
Methylmercury
(CH3Hg+)
Mercuric chloride
(HgCl)
Ingestion: reference
dose (RfD) (mg/kg-
day)b
not available
0.0001
0.0003
Inhalation: reference
concentration (RfC)
(mg/m3)'
0.0003
not available
not available
Notes, Source
Based on hand tremor, memory
disturbances, and other effects seen in
human occupational inhalation studies
(IRIS, 2001).
Based on developmental
neuropsychological impairment seen
in human epidemiological studies
(IRIS, 2001).
Based on autoimmune effects in rats
(IRIS, 2001).
a Forms of mercury for which EPA has established an RfD or RfC
b milligrams per kilogram of body weight per day for oral exposure (ingestion)
c milligrams per cubic meter of air, assuming continuous inhalation exposure for a 70-kg adult
4.2.5.2 Carcinogenicity
EPA has determined that mercury chloride and methylmercury are Possible Human
Carcinogens (cancer weight of evidence [WOE] classification C) based on limited evidence of
carcinogenicity in animals and inadequate or lack of human data. Elemental mercury is classified
by EPA as Not Classifiable as to Human Carcinogenicity (WOE class D) based on inadequate or
no evidence of carcinogenicity (IRIS, 2001).
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4.2.6 Environmental Regulations for Mercury
This section presents a brief summary of the U.S. regulations for mercury and mercury
compounds that may affect facilities that manufacture materials for the computer display or are
otherwise affected by the life cycle of computer displays. It should be noted that many of the
parts that go into the computer display are manufactured in other countries with their own
regulations which may differ significantly from those presented below.
Air emissions of mercury are regulated under the CAA of 1970 and the amendments of
1977 and 1990. Under the CAA, mercury is regulated as a hazardous air pollutant (HAP), which
is by definition a chemical that is either known or is suspected to cause serious health problems
for humans. EPA established National Emission Standards for HAPs (NESHAPs) for mercury
emissions based on risk under the pre-1990 version of the Clean Air Act. These NESHAPS [40
CFR 61 Subpart E] cover three source categories: ore processing facilities, mercury cell chlor-
alkali plants, and sewage sludge driers. Specific source requirements are specified for, among
other things, municipal waste combusters, hazardous waste combusters, and mercury ore
processing facilities. These source requirements could take the form of either a NESHAP or a
maximum achievable control technology (MACT) requirement.
OSHA has established standards for protecting worker health through the maintenance of
a safe working environment. The OSHA permissible exposure limit (PEL) for workplace
exposure to mercury is 0.1 mg/m3 (8-hour time weighted average). NIOSH has also established
recommended exposure limits (RELs) for several mercury compounds including a REL of 0.05
mg/m3 for mercury vapor.
Mercury emissions to surface water are regulated under the CWA, which lists mercury as
a priority pollutant [40CFR 401.15], requiring the limitation of mercury in point source
discharges. For mercury discharges, CWA regulations specify technology-based effluent limits
for classes and categories of industries (see 40 CFR 401, 403, Appendix B), and describe the
rights of states to establish effluent limits more stringent than technology-based standards.
Technology-based standards are listed for the following specific industries and point sources
involved in computer display manufacturing: nonferrous metals production, including primary
precious metals and mercury (40 CFR 250); secondary mercury (40 CFR 421.200); steam electric
power generation (40 CFR 423- Appendix A); and mercury ore mining (40 CFR 440.40). The
CWA also requires that new and existing points sources of mercury obtain a NPDES permit,
which will establish effluent limits for mercury discharges to surface waters.
To protect human health and preserve the nations drinking water supply, EPA has been
tasked by the SDWA to establish safe drinking water standards for toxic chemicals. In
accordance with the SDWA, EPA has established a safe drinking water standard for mercury of
2 ug/L.
The release or disposal of solid or hazardous waste containing mercury is regulated under
RCRA, which outlines specific classification and disposal requirements for products and wastes
that contain mercury. Mercury is both a characteristic and a listed waste under RCRA. A solid
waste containing mercury may be considered a D009 characteristic hazardous waste if, when
subjected to a TCLP test, the extract exceeds 0.2 mg/L [40 CFR 261.24] for mercury. Other
mercury-contaminated wastes may be considered hazardous if they are specifically listed in 40
CFR 261.30-33, unless they are specifically excluded. Listed wastes for mercury include
leachate resulting from the disposal of more than one restricted waste classified as hazardous
(F039), and wastewater treatment sludge and brine purification muds resulting from the mercury
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4.2 MERCURY
cell process in chlorine production (K106 and K071 respectively). Hazardous wastes are subject
to land disposal restrictions requiring that wastes be treated to below regulatory threshold levels
before they may be land-disposed.
In order to reduce the amount of hazardous waste in a landfill, EPA established the
Universal Waste Rule (UWR) in 1995. The rule was intended to encourage the recycling and
proper disposal of common hazardous waste components found in municipal waste streams, and
reduce the regulatory burden on businesses who produce these wastes. The rule allows for less
stringent standards for storing, transporting, and collecting wastes. However, the waste must
comply with full hazardous waste requirements for final recycling, treatment, or disposal.
Batteries and fluorescent lamps are included in the rule.
EPA also has regulated the air emissions of mercury from hazardous waste combustion
and from industrial boilers and furnaces under RCRA. EPA has issued new standards for
mercury emissions from these sources.
In December 2000, EPA announced plans to require coal-fired power plants to cut their
emissions of mercury. EPA plans to propose the regulations by 2003, with final rules in place by
2004 (EPA, 2000a). More recently, in April 2001 the Bush administration sought to dismiss an
electric industry lawsuit that would stop the EPA from regulating mercury and other toxic air
pollutants (Doggett, 2001).
Manufacturer's who emit mercury are required to report the quantity of the emissions
under the Emergency Planning and Community Right-to Know-Act (EPCRA). EPA has
established a reportable quantity threshold of 10 pounds for a facility that manufactures,
processes, or otherwise uses mercury. A similar threshold of 10 pounds exists for facilities that
manufacture, process, or otherwise use mercury compounds. Data that has been reported by
facilities for mercury is made available to the public through the publication of the Toxics
Release Inventory (TRI).
4.2.7 Alternatives to Mercury Use in LCDs
In an effort to minimize or even eliminate the quantity of mercury used during the
fabrication of LCDs, manufacturers have begun to develop mercury-free alternatives to mercury
vapor backlights. One such alternative is a flat lamp which is filled with inert gas xenon in place
of the typical mercury vapor lamps. The lamp has the appearance of a large white tile about one
centimeter in thickness. Its dimensions are the exact same as the screen itself, illuminating the
image evenly, hence eliminating the need for complex optical systems to distribute the light. The
new lamp is capable of emitting enough light to make the monitor twice as bright, making it
possible to use the screen during daylight, while also extending the viewing angle (OSRAM,
1998).
The new lamps generate light in a fashion similar to conventional backlight lamps. An
electrical current passed through a gas discharge produces ultra-violet light which is then
converted to visible light by phosphors. Unlike mercury gas which causes 'greying' in the
phosphors over time, the xenon gas does not affect the phosphors, extending the life of the lamp.
The lights have an average lifetime of up to 50,000 hours compared to only about 20,000 hours
for the conventional mercury backlights, extending the life of computer LCD displays before they
have to be replaced (OSRAM, 1998).
A drawback of the lamps, and the current subject of research is the reduced energy
efficiency of the new mercury-free lamps. The luminous efficiency of the new mercury-free
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4.2 MERCURY
lamp is only about half of the efficiency of a conventional backlight, due to less efficient
conversion of the UV light to visible light by the phosphors (OSRAM, 1998).
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4.3 LIQUID CRYSTALS
4.3 LIQUID CRYSTALS
One of the most significant differences between the two computer displays is the use of
liquid crystals in the LCD to generate an image. The toxicity of liquid crystals in LCDs has been
alluded to in literature indicating the potential for human health concerns. Because of relative
lack of information about these compounds, this section provides a more detailed look a liquid
crystals to better understand their potential impacts on human and ecological populations,
4.3.1 Liquid Crystals in Computer Displays
Liquid crystals (LCs) are organic compounds with the optical and structural properties of
crystals, but with the mechanical features of fluids. There are hundreds of LC compounds that
may be used in an LCD, each with different physical and optical characteristics. They are
typically classified by molecular weight, with low molecular weight LCs typically used for LCD
computer displays. LCs are not required for the fabrication of CRTs.
LCs are responsible for forming and transmitting the image produced by an LCD. The
LC portion of an LCD typically consists of as many as 20 different LC substances, mixed
together to form a white, opaque liquid that flows easily (Merck, 1999). The mixture consists of
elongated molecules that are held together at their ends by polar forces and aligned in the same
direction. The molecules move together in a series of flexible molecular chains, with each chain
influencing the alignment of other chains. By exposing the molecular chains to electric fields,
the alignment of the chains, and by extension their ability to transmit light, can be manipulated
(SEMI, 1995).
LCDs are fabricated using a complex multi-step process in a clean room (refer to Chapter
1 for a more detailed description of the fabrication process). Once the front and back layers have
been manufactured and assembled into a display cell, the LC is ready to be added. The
assembled display cells are placed into a vacuum chamber containing a reservoir of the LC
mixture, and the chamber is evacuated. A corner of the empty display cell is lowered into the LC
mixture using a remote control. Nitrogen gas is then introduced into the evacuated chamber to
bring the pressure up to approximately 1 atmosphere, exerting pressure on the surface of the LC
mixture, forcing it up into the display cell (SEMI, 1995). Approximately 0.6 mg of LC is
required for every square centimeter of panel surface (Merck, 1999). The display cell is sealed
once the LC fully penetrates the cell.
4.3.2 Life-Cycle Inputs and Outputs of Liquid Crystals for Computer Displays
Data on LC compounds were collected and compiled as part of the life-cycle inventory.
The data were aggregated by material from individual processes and presented by life-cycle stage
for LCDs in Table 4-19.
The individual LC compounds identified in Table 4-19 formed the ingredients of the
liquid crystal mixture used in the LCD. These compounds, used in varying quantities, are mixed
together in a liquid crystal manufacturing process to develop a mixture with the desired optical
characteristics for the LCD. While the above inputs illustrate the quantities of individual LC
compounds found in the LCD evaluated in this LCA, LC mixtures found in other LCDs could be
comprised of up to 20 or more liquid crystal compounds selected from the hundreds of
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4.3 LIQUID CRYSTALS
compounds currently available for use in LCDs. A small quantity of the liquid crystal mixture
(1.2 grams) is then used in the fabrication of the LCD.
Table 4-19. Life-cycle stage liquid crystal inputs
Life-cycle stage
Manufacturing
Manufacturing
Manufacturing
Manufacturing
Manufacturing
Manufacturing
Manufacturing
Manufacturing
Inputs a
Liquid crystal A
Liquid crystal B
Liquid crystal C
Liquid crystal D
Liquid crystal E
Liquid crystal F
Liquid crystal G
Liquid crystal mixture, for 15" LCD
Quantity
0.26
0.37
0.22
0.33
0.070
0.34
0.19
1.2
Units
g
g
g
g
g
g
g
g
Type
Primary material
Primary material
Primary material
Primary material
Primary material
Primary material
Primary material
Primary material
a Identities of liquid crystal compounds have been masked to protect the confidentiality of the compound names.
Life-cycle inventory data indicate that LCs are primarily released at the time of the
product's final disposition. Although other outputs of liquid crystals surely exist, they are likely
minimal and were not identified in the life-cycle inventory collected for LCDs. Evaporative LC
emissions during the manufacturing and mixture formulation processes are minimal due to the
typically low vapor pressures of LC compounds (Becker, 2001). Releases resulting from broken
or defective LCDs during manufacture are also likely to be small because of the strong adhesives
forces between LCs and the polymer film covering the outer layer of the displays (Becker, 2001).
However, small amounts of LC compounds were observed to present in the waste of one LCD
manufacturing facility during data collection (Overly, 2001). Because data were not provided
from manufacturers on manufacturing releases, and no data were available for releases at end-of-
life, it is difficult to definitively quantify the releases or their significance to the environment.
4.3.3 LCD Life-Cycle Impacts of Liquid Crystals
The life-cycle impacts of LC compounds calculated for LCDs during the LCIA are
summarized in Tables 4-20. Impact values in the table are expressed in units specific to each
impact category (see Chapter 3.1 for a discussion of impact category units and weighting). The
total impact score for each category from LCs is presented at the bottom of the table.
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4.3 LIQUID CRYSTALS
Table 4-20. Summary of LCD liquid crystal impacts
Life-cycle
stage
Manufacturing
Manufacturing
Manufacturing
Manufacturing
Manufacturing
Manufacturing
Manufacturing
Material
Liquid crystal A
Liquid crystal B
Liquid crystal C
Liquid crystal D
Liquid crystal E
Liquid crystal F
Liquid crystal G
Total category impact score
Chronic health effects- occupational
(tox-kg)
5.29E-04
4.35E-04
3.89E-04
1.40E-04
6.84E-04
6.53E-04
7.31E-04
3.56E-03
Impact scores have been calculated based on the inventory item, release type, and its
reported disposition. Occupational impacts to workers as a result of LC inputs are shown in the
Table 4-20. Impacts were not calculated for LCs which end up as part of the product because
users of the product are not expected to become exposed to the LC compounds during the typical
operation of the LCD. In addition, because releases of LCs to the environment were not provided
by the manufacturers in the LCI, potential impacts resulting from these releases were also not
assessed in this project. LCs are not used to fabricate CRTs and so have no environmental
impacts in the CRT life cycle.
LCs do not appear to contribute significantly to any of the impact categories defined for
this study. The total score for occupational impacts based on potential worker exposure to LCs
of 4.18 tox-grams represents less than 0.01% of the total overall chronic occupational health
effects impact score of 898 tox-kg for the functional unit of one LCD.
4.3.4 Exposure Summary
Like any materials classified as potentially toxic, LCs have the potential to pose a threat
to human health anytime there is the potential for human or ecological exposure throughout the
life cycle of a LCD. Exposure occurs anytime a chemical or physical agent, in this case LC
compounds, come into contact with an organism, be it human or ecological. This section
qualitatively identifies potential exposures for workers in facilities using LCs (occupational
exposures), the general public, who may be exposed to LC releases into the ambient
environment, and the ecological population.
4.3.4.1 Occupational exposures
Occupational exposures to LCs during the fabrication of the LCD panels are not expected
to be significant. LCD panels are fabricated in a clean room environment. The previously
assembled but empty display cells are placed into a vacuum chamber containing a reservoir of the
LC mixture, and lowered into the LC mixture using a remote control. Approximately 1.2 grams
of LC compounds are used to develop the LCD panel. The enclosed nature of the chamber
combined with the equipment (e.g., gloves, aprons) worn by workers in a clean room
environment may both act to minimize exposures.
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4.3 LIQUID CRYSTALS
However, the potential for other occupational exposures still exist. Workers could
become exposed to LCs during other manufacturing process steps, such as during the formulation
of the LC mixture (approximately 1.8 grams from Table 4-31), the handling and disposal of
broken or defective panels, or during the recycling or disposal of an LCD at the end of its useful
life. Because of the physical nature of the LCs (e.g., they are not volatile), typical worker
exposures are likely to be through dermal or ingestion (e.g., accidentally ingesting LC present on
a workers hands) routes. Worker exposure to LCs via dermal exposure is expected to be minimal
for workers who wear gloves while handling LCs.
4.3.4.2 General population
Because of the enclosed nature of the LCD panel, it is unlikely that consumers could
become exposed to LC compounds contained within the display through normal usage. LCs may
be released into the environment should the panel become fractured, either through accident or
through final disposal. No other releases of LC compounds into the environment were identified
by the LCI data collected for the LCD, making it difficult to assess any possible exposures to
nearby populations.
4.3.4.3 Ecological populations
Potential exposure to ecological populations could typically only occur through the
migration of LCs through the environment after being released during manufacturing or disposal
(either at LCD end-of-life, during disposal of broken or damaged panels during manufacturing, or
during disposal of containers or equipment contaminated with LCs). The potential for transport
of the LC through the environment is dependent on the identity of the chemical compound. The
number of choices of LC compounds along with the unavailability of data on disposal quantities
make it difficult to accurately assess the potential exposures which might result.
4.3.5 Human Health Effects
There are at least ten meaningful groups of liquid crystal compounds representing several
hundred LC substances. Each of these substances is chemically unique, each having the potential
to affect human health. Because of the number of LC compounds potentially present in the LCD,
it is not possible to provide a comprehensive review of the human health effects of the universe
of liquid crystal substances. However, a review of a small sample of LC compounds, those
which appeared in the project LCI collected for the LCD, was conducted by EPA and the results
presented below.
Toxicological testing of LC substances and mixtures was conducted by three
manufacturers responsible for roughly 90% of LC production. Testing of their chemical products
included testing for acute toxicity effects, and effects on skin and eyes. Results of the testing
indicated that of 588 LC substances tested, only twenty-five LC compounds had an LD505 less
LD50 represents the dose of chemical which is lethal to 50% of the test population. By comparison, the
LD50 for sodium chloride (table salt) is 3,000 mg/kg of body weight.
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4.3 LIQUID CRYSTALS
than 2,000 mg/kg of body weight (classified as exhibiting harmful effects to humans by the
European Union), and only one had a LD50 of less than 200 (classified as toxic by the European
Union). The remaining 562 LC substances did not have any acute toxic potential. Of the twenty-
five harmful LCs, only twenty-two substances are produced and all are present at less than 10%
concentration by weight, meaning that the resulting LC mixtures are not expected to exhibit
harmful properties to humans (Becker, 2000). The remaining three harmful chemicals along with
the lone toxic chemical were discontinued and excluded from further development. Several
compounds, but still a minority, were found to be skin or eye irritants (Merck, 1999).
4.3.5.1 Chronic effects (noncancer)
EPA conducted a review of existing toxicological data for the LC substances listed in
Table 4-31. The review failed to identify a RFD, RFC, NOAEL, or LOAEL for any of the LC
substances shown. This typically indicates that insufficient testing of these chemical compounds
has been performed to accurately determine their potential for chronic human effects.
4.3.5.2 Carcinogenicity and mutagenicity
An EPA review of toxicological studies for the liquid crystals identified in the life-cycle
inventory for LCDs failed to identify an existing slope factor for any of the LC compounds. A
lack of carcinogenicity data usually does not indicate that a compound is not carcinogenic, but
only that sufficient testing to ascertain carcinogenicity has yet to be performed.
Toxicological testing of LC substances for mutagenic effects was conducted by three
manufacturers responsible for roughly 90% of LC production. In a bacterial mutagenicity test of
615 LC substances, one LC compound showed mutagenic potential, with the remaining
compounds displaying no mutagenic effects. The lone chemical that failed the test was excluded
from further development and was never marketed (Becker, 2000). Additionally, 10 LC
compounds representing each of the significant groups of LCs, underwent mutagenicity testing
using mammalian cells. None of the tests indicated mutagenic activity. Based on both sets of
data, the manufacturer concluded that there does not appear to be a suspicion of mutagenic
potential in the liquid crystals it produces (Merck, 1999).
4.3.6 Environmental Regulations for Liquid Crystals
No regulations exist specifically for liquid crystals compounds. However, regulations
may exist for individual liquid crystal compounds. Because of the number of possible LC
compounds available for use in a LCD, a comprehensive review of U.S. regulations could not be
provided.
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4.4 CONCLUSIONS
4.4 CONCLUSIONS
The purpose of this chapter was to provide a more detailed analysis of a few select
materials of interest to EPA and industry that was intended to better understand the potential
exposures and chemical risks to both human and ecological populations. The materials selected
for further analysis included lead, mercury, and liquid crystals, each selected for its known or
suspected toxicity to humans and the environment, or because they are of particular interest to
indsutry or the U.S. EPA. The analysis of each material summarized or evaluated the following
key areas:
• Use of the materials in computer displays;
• Life-cycle inputs and outputs of the materials from computer displays;
• Life-cycle impacts associated with the material inputs and outputs;
• Potential exposures to the material including occupational, public, and ecological
exposures;
• Potential human health effects;
• U.S. environmental regulations for the material; and
• Alternatives to reduce the use of the material in computer displays.
The following are the conclusions drawn from the analyses of lead, mercury, and liquid crystal
use in the life cycle of both CRTs and LCDs.
4.4.1 Lead
Lead is found in glass components of CRTs, as well as in electronics components (printed
wiring boards and their components) of both CRTs and LCDs. It is also a top priority toxic
material at the U.S. EPA and the subject of electronics industry efforts to reduce or eliminate its
use. The following conclusions were drawn from a focused look at lead's role in the life cycle of
the computer display, and its effects on human health and the environment:
• Due to the much greater quantity of lead in the CRT than the LCD, lead-based life-cycle
impacts from the CRT ranged from moderately to significantly greater than those from
the LCD in every category, with the exception of solid waste landfill use. The most
significant difference was in non-renewable resource consumption, where the CRT
consumed over 40 thousand times the mass of non-renewable resources over the course of
its life cycle than those consumed by the LCD. Other categories where CRTs had notably
greater differences in impacts occurred in hazardous waste landfill use, chronic public
health effects, and terrestrial toxicity.
• Contributions of lead-based impacts are small relative to the total life-cycle impacts from
other materials in the CRT (e.g., glass, copper wire), with the greatest impacts from lead-
based CRT outputs occurring in the categories of non-renewable resources, aquatic
toxicity, and chronic public health effects (ranging from 0.1 to 0.2% of the overall impact
scores in each category).
• For workers, inhalation is the most likely route of exposure to lead which may result in
health concerns. General population exposure to lead is most likely to come from
incidental ingestion of lead in the soil, or ingestion of lead brought into the household on
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4.4 CONCLUSIONS
workers clothing or on shoes. Studies have discovered potentially high concentrations of
lead in households within close proximity to certain facilities that use lead.
• Significant worker exposures to lead have been documented by existing studies of several
processes which contribute to the life-cycle of the computer displays (e.g., lead smelting).
These exposures have been as high as 90 times the OSHA recommended safety levels for
exposure to workers at lead smelters. The resulting occupational chronic health effects to
workers from lead exposure likely have been underestimated by the CDP LCIA
methodology, which uses material inputs, and not outputs, as surrogates for exposure.
• Lead and lead compounds pose serious chronic health hazards to humans who may
become over-exposed either in the workplace, or through the ambient environment. Lead
exposure is associated with a range of adverse human health effects, including effects on
the nervous system, reproductive and developmental problems, and cancer. Lead persists
in the environment, but is relatively immobile in water under most surface and
groundwater conditions.
• Alternatives are being developed, such as lead-free solders and glass components, that
will potentially minimize the future lead content in both CRTs and LCDs.
4.4.2 Mercury
Mercury is contained within the fluorescent tubes that provide the source of light in the
LCD. Mercury is also emitted from some fuel combustion processes, such as coal-fired
electricity generation processes, which contribute to the life-cycle impacts of both CRTs and
LCDs. EPA's concern with mercury and the potential for exposure during manufacturing and
end-of-life processes warranted a more detailed analysis of mercury in the CDP. The following
conclusions were drawn from a focused look at mercury's role in the life cycle of the computer
display, and its effects on human health and the environment:
• The mercury emitted from the generation of power consumed by the CRT (7.75 mg)
exceeds the entire amount of mercury emissions from the LCD, including both the
mercury used in LCD backlights (3.99 mg) and the mercury emissions from electricity
generation (3.22 mg). Although this was not expected because mercury is used
intentionally in an LCD, but not in a CRT, the results are not surprising since mercury
emissions from coal-fired power plants are known to be one of the largest anthropogenic
sources of mercury in the United States. Because the CRT consumes significantly more
electricity in the use stage than the LCD, its use stage emissions of mercury are
proportionately higher than those of the LCD.
• Contributions from mercury-based impacts are not significant relative to the total life-
cycle impacts from other materials (e.g., glass, copper wire) in the CRT or LCD, with the
greatest impacts from mercury-based outputs occurring in the aquatic toxicity category
(0.4% for CRTs, 0.01% for LCDs)
• Possible pathways of worker exposure during backlight fabrication include inhalation of
mercury vapors, and dermal exposure or ingestion of mercury on skin. The most likely
pathway for general population exposure is inhalation of mercury released into the air.
• Exposure data relevant to the manufacturing of mercury backlights were not available,
therefore specific conclusions about the potential magnitude of worker exposures could
not be made. Occupational chronic health effects to workers from mercury exposures
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4.4 CONCLUSIONS
calculated during the impact assessment (3.99e-06 tox-kg for LCD, none for CRT) likely
have been underestimated by the CDP LCIA methodology, which uses material inputs as
surrogates for exposure.
Mercury and mercury compounds pose serious chronic health hazards to humans who are
exposed. EPA has determined that mercury chloride and methylmercury are possible
human carcinogens. Mercury poses serious chronic health hazards to humans, affecting
the nervous system, brain, and kidneys.
Alternative backlights have been developed that not only eliminate mercury from the
light, but also improve on many of the optical characteristics of the displays. Current
development is focused on improving the energy efficiency of the alternative lights.
4.4.3 Liquid Crystals
Liquid crystals are organic compounds responsible for generating the image in an LCD.
LCs are not present in CRTs. The toxicity of the LCs in LCDs has been alluded to in the
literature, yet there is very little known about the toxicity of these materials. By including LCs in
a more detailed analysis, this section attempted to better characterize any potential hazard and/or
potential exposure of LCs from the manufacturing, use, and disposal of LCD monitors. The
following conclusions were drawn from a focused look at LCs role in the life cycle of the
computer display, and its effects on human health and the environment.
• LCs are combined into mixtures of as many as 20 or more compounds selected from
hundreds of potential liquid crystal compounds. Because of the possible variations in
mixtures and the sheer number of compounds available, a select number of liquid crystals
were used to assess potential human health hazards.
• LCs do not appear to contribute significantly to any of the impact categories defined for
this study. The total score for LCD occupational impacts based on potential worker
exposure to LCs of 4.18 tox-grams, calculated using default toxicity values, represents
less than 0.01% of the total overall chronic occupational health effects impact score of
898 tox-kg for the functional unit of one LCD.
• Impacts were not calculated for LC releases in the CDP LCIA because data regarding LC
outputs were not available to the project. LCs are not used to fabricate CRTs and so
have no environmental impacts in the CRT life cycle.
• Occupational exposures to LCs during the fabrication of the LCD panels are not expected
to be significant. The enclosed nature of the chamber in which the LCDs are assembled,
combined with the equipment (e.g., gloves, aprons) worn by workers in a clean room
environment, are both expected to act to minimize exposures. Other occupational
exposures may exist that have not been identified.
• Toxicological testing by a manufacturer of LC substances and mixtures showed that
95.6% (562 of 588) of the liquid crystals tested displayed no acute toxic potential to
humans. Twenty-five of the remaining twenty-six chemicals had the potential to exhibit
harmful effects to humans, while the remaining crystal was classified as toxic (EU
classification) and thus was discontinued. An EPA review of toxicity data for the
confidential LC compounds was unable to identify any relevant toxicity information.
Insufficient toxicity data exist to assess the toxicity of specific LC compounds.
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4.4 CONCLUSIONS
Testing for mutagenic and carcinogenic effects by the supplier showed that 99.9% (614
out of 615) of the liquid crystal compounds tested displayed no mutagenic effects. The
remaining chemical that showed mutagenic potential was excluded from further
development. Additionally, mutagenicity testing often LC substances using mammalian
cells showed no suspicion of mutagenic potential.
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Lee, C., Chang, S., Wang, K., and Wen, L. 2000. "Management of Scrap Computer Recycling in
Taiwan." Journal of Hazardous Materials. A73: 209-220.
Menad, N. 1999. "Cathode Ray Tube Recycling." Resources, Conservation, and Recycling.
26: 143-154.
MERCK. 1999. "Toxicological Investigations of Liquid Crystals." Presented at 28th Freiburger
Arbeitstagung. March 24-26.
Monchamp, A., Evans, H., Nardone, J., Wood, S., Proch, E., Wagner, T. 2001. "Cathode Ray
Tube Manufacturing and Recycling: Analysis of Industry Survey." Electronic Industries
Alliance. Spring.
Musson, S., Jang, Y., Townsend, T., and Chung, I.. 2000. "Characterization of Lead Leachability
from Cathode Ray Tubes Using the Toxicity Characteristic Leachate Procedure."
Environmental Science and Technology. 34: 4376-4381.
NIOSH (National Institute for Occupational Safety and Health). 1997. NIOSH Pocket Guide to
Chemical Hazards. Publication No. 97-140. U.S. Government Printing Office.
Washington D.C.
OSRAM. 1998. "The World's First Mercury-Free Flat Lamp." Web site available at:
http://www.osram.com/txt/aktuell/planone.htm. July 13.
Sittig, M. 1985. Handbook of Toxic and Hazardous Chemicals and Carcinogens. 2nd ed.
Noyes Data Corporation, Park Ridge, NJ.
Srivastava, A.M. and Sommerer, T.J. 1998. "Fluorescent Lamp Phosphers." Electrochemical
Society Interface. Summer.
Techneglas, Incorporated. "Frit Facts: A Brief Technological Summary of Televison Solder
Glass for CRT Technicians, Engineers, and Managers", downloadable fact sheet.
http://www.techneglas.com.
4-46
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5.1 LCI vs. LCIA
Chapter 5
SUMMARY AND CONCLUSIONS
The purpose of the CDP, as stated in Chapter 1, is to provide a scientific baseline of life-
cycle environmental impacts of CRTs and LCDs, help manufacturers identify areas to focus
improvement assessment activities, and to develop a life-cycle model for future analyses. The
primary targeted audience is the electronics industry, for whom results may provide insight into
improvement opportunities in the life cycle of CRTs and/or LCDs. In addition, the general
public may also find results useful when considering environmental impacts of each display type.
This chapter briefly summarizes the results and draws conclusions based on those results. This
report, however, does not include direct comparative assertions or improvement assessments
based on the results. Alternatively, results and conclusions are described in terms of the overall
LCI versus the LCIA, and details of the impact assessment, including the additional assessments
of lead, mercury and liquid crystals, and the sensitivity analyses. Major uncertainties, cost and
performance considerations, suggestions for improvement opportunities, and suggestions for
further research are also provided.
5.1 LCI vs. LCIA
In this LCA, a life-cycle inventory (LCI) was compiled from many data sources,
including both primary and secondary data sources. The primary data were obtained from
component and monitor manufacturers of CRTs and LCDs. In an LCA, inventory data provide
information on how much material is being consumed in the life cycle (i.e., inputs) and how
much material is generated/released (i.e., outputs). The LCI results of this report are detailed in
Chapter 2. The LCI provides inventory data grouped by inventory type (e.g., primary material,
energy, air emission, solid waste).
The LCI alone, however, does not always translate directly into impact categories that
may be of interest. That is, a given amount of one material may have different impacts (for a
certain impact category) than the same amount of another material. Furthermore, some materials
may affect more than one impact category. For example, an air emission could affect air
acidification as well as being toxic to humans breathing it. Therefore, a life-cycle impact
assessment (LCIA) is conducted to reveal potential impacts in several impact categories. In this
CDP LCIA, described in detail in Chapter 3, impacts are sometimes driven by materials other
than the top inventory contributors. For example, the top air emission for LCDs is carbon
dioxide (Table 2-49), however the greatest global warming impact score is from SF6 in the LCD
monitor/module manufacturing process (Table 3-25).
To illustrate that the inventory results may not directly translate into impact results, the
first two columns in Table 5-1 show which monitor has greater inventory amounts for each
inventory type in the LCI, and the last two columns show which monitor has greater impact
scores for each impact category in the LCIA. The impact categories that are affected by each
inventory type are in the same rows as the associated inventory type. As seen in Table 5-1, some
impact categories associated with ancillary material and water pollutant inventory types had
opposing outcomes in the LCI versus the LCIA. For example, the three impact categories
affected by the ancillary material inventory had greater impacts for the CRT, although the
5-1
-------
5.1 LCI vs. LCIA
ancillary material inventory had greater amounts of inputs for the LCD. In this case, both
primary and ancillary materials contribute to the impact categories, causing differing results.
Considering the wastewater outputs, which are greater for the LCD than the CRT, the
impacts related to water releases are in some cases greater for the CRT than the LCD. Note that
although the wastewater volume is greater for the LCD, the total mass of water pollutants in the
LCI is greater for the CRT (see Table 2-24). In the LCIA, the LCD has greater impacts for water
eutrophication and aquatic toxicity, but not for the two water quality categories (BOD and TSS),
chronic health effects to the public, nor terrestrial toxicity, all of which include water emissions
in calculating the impact score.
Table 5-1. Baseline LCI vs. LCIA: monitor with greater inventory amount and impact
Baseline life-cycle inventory (LCI)
Inventory type
Primary materials
Ancillary materials
Water inputs
Fuel inputs
Electricity inputs
Total energy inputs
Air pollutant outputs
Monitor with
greater
inventory
results
CRT
LCD
CRT
CRT
CRT
CRT
CRT
Baseline life-cycle impact assessment (LCIA)
Potential impact category(ies)
associated with inventory type
Renewable resource use
Nonrenewable resource use
Chronic health effects, occupational
Renewable resource use
Nonrenewable resource use
Chronic health effects, occupational
Renewable resource use
Energy use
Chronic health effects, occupational
Energy use
Energy use
Global warming
Ozone depletion
Photochemical smog
Acidification
Air particulates
Chronic health effects, public
Aesthetics (odor)
Terrestrial toxicity
Monitor with
greater
impact results
CRT
CRT
CRT
CRT
CRT
CRT
CRT
CRT
CRT
CRT
CRT
CRT
a
CRT
CRT
CRT
CRT
CRT
CRT
5-2
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5.1 LCI vs. LCIA
Table 5-1. Baseline LCI vs. LCIA: monitor with greater inventory amount and impact
Baseline life-cycle inventory (LCI)
Inventory type
Wastewater outputs
Water pollutant outputs
Hazardous waste outputs
Solid waste outputs
Radioactive waste outputs
Radioactivity outputs
Monitor with
greater
inventory
results
LCD
CRT
CRT
CRT
CRT
CRT
Baseline life-cycle impact assessment (LCIA)
Potential impact category(ies)
associated with inventory type
none
Water eutrophication
Water quality, BOD
Water quality, TSS
Chronic health effects, public
Aquatic toxicity
Terrestrial toxicity
Hazardous waste landfill use
Solid waste landfill use
Radioactive waste landfill use
Radioactivity
Monitor with
greater
impact results
NA
LCD
CRT
CRT
CRT
LCD
CRT
CRT
CRT
CRT
CRT
a The LCIs for both the CRT and LCD contain data for substances that were phased out of production by 1996 due
to their ozone depletion potential. Whether these emissions still occur in countries that were signatories to the
Montreal Protocol and its Amendments and Adjustments (such as the United States and Japan) is not known, but
considered to be unlikely. When phased-out substances are included in the inventory, the CRT has greater ozone
depletion impacts than the LCD. However, if phased-out substances are removed from the inventories, the results
are switched, with the LCD having greater impacts.
5-3
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5.2 LCIA RESULTS
5.2 LCIA RESULTS
5.2.1 CRT and LCD Baseline Results
The LCIA results, presented in detail in Chapter 3, showed that the CRT has greater total
life-cycle impact indicators in most of the impact categories (see Table 3-10). In the baseline
scenario, the CRT has greater impacts than the LCD in all but two impact categories
(eutrophication and aquatic toxicity). However, note that for the ozone depletion category, the
LCIs for both the CRT and LCD contain data for substances that were phased out of production
by 1996 due to their ozone depletion potential. Whether these emissions still occur in countries
that were signatories to the Montreal Protocol and its Amendments and Adjustments (such as the
United States and Japan) is not known, but considered to be unlikely. When phased-out
substances are included in the inventory, the CRT has greater ozone depletion impacts than the
LCD. However, if phased-out substances are removed from the inventories, the results are
switched, with the LCD having greater impacts.
When considering which life-cycle stage has greater impacts, the LCIA results showed
that the manufacturing life-cycle stage dominates impacts for most impact categories for both the
CRT and LCD (refer to Section 3.3). Table 5-2 summarizes which life-cycle stages have the
greatest impacts for each impact category for the CRT and LCD. As shown in Table 5-2, the
CRT has nine and the LCD has 11 impact categories with greatest impacts from the
manufacturing life-cycle stage. Only six categories (solid waste landfill use, global warming,
ozone depletion, acidification, air particulates, and chronic public health) have greatest impacts
from the CRT use stage, and four categories (solid waste landfill use, acidification, air
particulates, and chronic public health) have greatest impacts from the LCD use stage. The CRT
has three categories with greatest impacts from the upstream life-cycle stage and the LCD has
three. The end-of-life (EOL) life-cycle stage is greatest for the same two impact categories for
both the CRT and LCD (hazardous waste landfill use and radioactive waste landfill use). Note
that the EOL stage impacts are generally very small contributors to the overall impacts. This is
likely because of the small inventories associated with the EOL processes, but also may be a
function of the incomplete and/or secondary data for the EOL (i.e., no remanufacturing data, and
secondary data not completely specific to the monitors evaluated in this study).
A more detailed evaluation of lead, mercury, and liquid crystals was completed in
Chapter 4. As expected, the CRT, which has lead in the glass, frit, and printed wiring boards
(PWBs), has greater impacts from lead than did the LCD, which only has lead in the PWBs.
Regarding mercury, there were greater inventories of mercury in the CRT life cycle than in the
LCD life cycle, despite the fact that only the LCD has mercury directly in the product. The
greater amount of mercury is from the release of mercury and mercury compounds from the
generation of electricity. And as the CRT life cycle uses more electricity than the LCD, there
was a greater quantity of mercury releases reported for the CRT than the LCD. Liquid crystals
are only found in LCDs, and therefore, there are no associated impacts for the CRT. Little
conclusive information was available on the liquid crystal materials. A detailed literature search
was conducted, however very little data were available on the toxicity of these materials. Based
on the limited toxicity data obtained, liquid crystals currently do not appear to be a significant
human health or environmental hazard in the LCD life cycle. However, there were insufficient
toxicity data available to make a definitive conclusion about liquid crystal toxicity.
5-4
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5.2 LCIA RESULTS
Table 5-2. Monitor
and
type with greatest impacts for each life-cycle stage
impact category (baseline scenario)
Impact category
Renewable resource use
Nonrenewable resource use
Energy use
Solid waste landfill use
Hazardous waste landfill use
Radioactive waste landfill use
Global warming
Ozone depletion
Photochemical smog
Acidification
Air particulates
Water eutrophication
Water quality, BOD
Water quality, TSS
Radioactivity
Chronic health effects, occupational
Chronic health effects, public
Aesthetics (odor)
Aquatic toxicity
Terrestrial toxicity
TOTALS
Monitor type with greatest impacts
Upstream
LCD
LCD
CRT
CRT, LCD
CRT
CRT=3
LCD=3
Manufacturing
CRT
CRT, LCD
CRT, LCD
LCD
LCD
CRT
LCD
CRT, LCD
CRT, LCD
CRT, LCD
CRT, LCD
LCD
CRT, LCD
CRT=9
LCD=11
Use
CRT, LCD
CRT
CRT
CRT, LCD
CRT, LCD
CRT, LCD
CRT=6
LCD=4
EOL
CRT, LCD
CRT, LCD
CRT=2
LCD=2
5.2.2 CRT Results
For the CRT, many of the impacts were driven by a single material in the inventory. As
stated in Section 3.3.15 and shown in Table 3-57, in 14 of the 20 impact categories, the top
individual contributor to the impacts was responsible for greater than 50% of the impacts. This
shows that the CRT data are highly sensitive to a few data points. Major conclusions from the
CRT LCIA are as follows:
• Energy used in glass manufacturing and associated production of LPG are driving the
baseline CRT results (they dominate ten impact categories, including overall life-cycle
energy use).
5-5
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5.2 LCIA RESULTS
• The large amounts of fuel used as energy sources are driving occupational health effects.
Occupational impacts are calculated from inventory input amounts, and therefore there
may or may not actually be exposure to these fuels (e.g., they may be contained);
however, the results illustrate the potential for health effects, especially under spill or
upset conditions.
• The generation of electricity for the use stage dominates seven impact categories.
• Air emissions of sulfur dioxide from electricity generation (for the use life-cycle stage)
drive chronic public health effects, acidification, and terrestrial toxicity impacts. This
may be a concern, for example, in areas in nonattainment of regulated levels of sulfur
dioxide in the United States.
The use of LPG fuel in glass manufacturing dominated ten impact categories: two
directly from the LPG used in glass/frit manufacturing (energy use impacts and chronic
occupational health effects) and eight from LPG production (renewable resource use,
nonrenewable resource use, photochemical smog, air particulates, water eutrophication, BOD
water quality, TSS water quality, and aesthetics). In addition, impacts from the generation of
electricity during the use stage dominated seven impact categories: solid waste landfill use,
radioactive waste landfill use, global warming, ozone depletion, acidification, chronic public
health, and terrestrial toxicity. The CRT tube manufacturing process, which represents the most
functionally and physically (by mass) significant component of the CRT monitor, only dominated
one impact category (aquatic toxicity). Twenty-six percent of the aquatic toxicity score was from
phosphorus outputs from tube manufacturing, while most of the rest were from the materials
processing life-cycle stage. The remaining two impact categories (hazardous waste landfill use
and radioactivity) had greatest impacts from the landfilling of the assumed hazardous proportion
of CRT monitors, and the release of Plutonium-241 in steel production, respectively
(Table 3-57). The radioactivity impacts are driven by the radionuclide Pu-241, due to the electric
grid inventory included in the steel production secondary data set, which includes nuclear fuel
reprocessing.
The large amount of LPG reported for glass manufacturing was originally questioned
during the data collection and verification stage of this project. While no compelling reason
could justify removing the LPG data in the baseline case, a sensitivity analysis was conducted in
which the glass energy data were modified. Other sensitivity analyses were also conducted (i.e.,
manufactured life, modified LCD monitor manufacturing energy, and modified LCD EOL
distributions). However, the only scenario that substantially altered the comparative results was
the modified glass energy scenario (see Table 3-62 and Section 3.4.5).
The overall energy in the baseline scenario was nearly seven times greater than that in the
modified scenario (from 20,800 MJ to 3,020 MJ), and the amount of LPG dropped to zero, while
other energy sources increased. The basis for the modified data was removing the energy inputs
from one suspect data set. As a result, the CRT modified glass energy scenario had greater
energy use impacts in the use stage than in the manufacturing stage for the CRT. The amount of
LPG used in glass manufacturing in the baseline scenario is 351 kg/monitor of LPG, which alone
5-6
-------
5.2 LCIA RESULTS
costs about $71.1 This is a significant amount of the cost of a complete CRT monitor (the range
of a few currently selling 17" CRTs is $158-316, and the average cost from primary data
collected in the CDP was $541, which are presented in Section 5.4). Therefore, it is likely that
the actual energy inputs to the glass manufacturing process is somewhere between the baseline
and modified glass scenarios. In conclusion, more information is needed on energy used in glass
manufacturing, which is driving CRT baseline results.
The additional analyses for the CRT of lead and mercury also revealed that the use of lead
could present health risks, but the method of using only inputs to evaluate occupational impacts
(see Section 3.1.2.13) may not adequately represent occupational exposures and risks. Further
refinement of the occupational impact analysis may be warranted.
Although there is no mercury in the CRT monitor, mercury emissions from electricity
generation in the CRT life cycle were greater (in mass) than the mercury used in the LCD.
Therefore, to reduce mercury emissions from the CRT life cycle, efforts to reduce electricity
consumption could be taken. Additionally, changes to the electric grid could also reduce
mercury emissions from the CRT life-cycle.
5.2.3 LCD Results
The LCD impact results were less sensitive to an individual input or output than the CRT
results, although in 11 of the 20 impact categories an individual input was still responsible for
greater than 50% of the total impacts (Table 3-58). In general, the LCD results are less uncertain
than the CRT results. This is because most of the CRT results are being driven by either glass
input data or data from secondary sources, while LCD impacts are being driven more by data
from primary sources. Some results to note are as follows:
• The LCD monitor/module manufacturing process group had greatest impacts in six
impact categories (Table 3-58).
• Although the top contributor to the energy impact category was electricity consumed in
the use stage (30%), the overall energy impacts were greater from the manufacturing
stage than the use stage.
• In the glass energy sensitivity scenario, the use stage had greatest energy impacts,
although only by a small margin over the manufacturing stage (see Figure 3-26).
• Sulfur dioxide [emitted from electricity generation for the use stage, and constituting only
0.37% of the air emission inventory (see Table 2-49)] dominates the acidification, chronic
public health, and terrestrial toxicity impact categories (Table 3-58). The high public
health and terrestrial toxicity scores are due to its low non-cancer toxicity value and
resulting high hazard value (HV).
• Sulfur hexafluoride (SF6) from LCD monitor/module manufacturing was the single
greatest contributor to the global warming impact score; however, carbon dioxide from
the use stage and the materials processing stage also contributed significantly to the
global warming impacts (Table 3-25).
1 Based on a "daily market price" on August 29, 2001, of $0.4160/gallon of LPG
(http://www.americanpowernet.com/pub_energy/futures.html). For 351 kg/functional unit in the CRT manufacturing
life-cycle stage, the cost is about $71 per functional unit (i.e., one monitor), assuming a density of LPG of 2.053
kg/gallon. For the LCD, the 16.8 kg/functional unit of LPG would cost about $3.40 per monitor.
-------
5.2 LCIA RESULTS
• The glass energy inputs did not directly dominate any impact categories, as they did for
the CRT (due to the smaller mass of glass in the LCD); however, LPG production
(required for the glass energy fuel) dominated two categories: TSS water quality and
aesthetics (Table 3-58).
• LNG as an ancillary inventory material was questionably very large and had greatest
impacts in two categories: nonrenewable resource use and photochemical smog
(Table 3-58; shown there as "Natural Gas Production" due to that process being used as a
surrogate for LNG production).
The additional analyses of lead, mercury, and liquid crystals showed that the LCIA alone
is not adequate enough to determine all the potential impacts within the life-cycle of the LCD
monitors. Similar to the conclusion for the CRT, lead-based occupational impacts would require
further refinement of the LCIA methodology. The LCIA method in this LCA used inputs as
surrogates for occupational exposure. There are outputs, within the occupational setting, that
should also be considered.
For mercury, which is found in the backlights of the LCD monitors, there is nearly the
same amount of mercury by mass emitted to the air during electricity generation as there is
mercury used to make the backlight unit. The mass of mercury input for backlights is only about
20% greater than the mercury air emissions from electricity generation (across all life-cycle
stages).
Liquid crystals were also identified by the CDP Core Group as a material for which
additional information would be reviewed. The LCIA did not find the liquid crystals to be
significant contributors to any impact categories; however, this could partially be due to the lack
of information on them. The additional analysis also revealed limited information, but
qualitatively, did not show significant potential risk.
5.2.4 CRT vs. LCD Sensitivity Analysis Results
The only sensitivity analysis to show significant difference in the results was the modified
glass energy scenario. In comparing the CRT and LCD, the CRT baseline scenario had greater
impacts than the LCD in all but two impact categories (eutrophication and aquatic toxicity) and
possibly three (ozone depletion). In the modified glass energy scenario, nine of the 20 categories
had greater impacts from the LCD life-cycle than the CRT. Energy use remained greater for the
CRT; however, nonrenewable resource use, global warming, photochemical smog,
eutrophication, BOD and TSS water quality, chronic occupational health effects, and aesthetics
all reversed such that the LCD had greater impacts than the CRT (Table 3-62). As stated above,
it is believed that a more true representation of the monitor life cycles lies somewhere between
the baseline and modified glass energy scenario. Further work is recommended in clarifying and
refining glass energy input information.
5-8
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5.3 UNCERTAINTIES
5.3 UNCERTAINTIES
As with any LCA, it is not uncommon for there to be uncertainty associated with such a
large data collection effort. Two of the largest sources of uncertainty in this LCA that have a
significant effect on the results are as follows:
• CRT and LCD glass manufacturing energy inputs (from primary data): The larger
amount of glass used in CRTs than LCDs results in the CRT having greater associated
uncertainty than the LCD results.
• Secondary data for upstream and fuel production processes: When any one material is
used in the life-cycle of either monitor in large quantities, the impacts associated with the
inputs and outputs from the production of that material may become significant. For
example, LPG and LNG production were both used in significant enough amounts to
influence some impact categories. Therefore, the uncertainty in the secondary data
becomes important. This highlights the need for a consistent, national (or international)
LCI database that is updated regularly.
Other uncertainties associated with individual data points collected from primary data
sources may be found in the data for this analysis. However, they had less effect on the overall
results than the uncertainties mentioned above. For manufacturers interested in conducting
improvement assessments, closer review of such uncertainties may be warranted.
Other uncertainties in the LCA pertain to uncertainties inherent in LCIA methodology.
The purpose of an LCIA is to evaluate the relative potential impacts of a product system for
various impact categories. There is no intent to measure the actual impacts or provide spatial or
temporal relationships linking the inventory to specific impacts. Uncertainties are inherent in
each impact category, and the reader is referred to the baseline LCIA results in Section 3.3 for a
detailed discussion of uncertainties by impact category.
Another point that should be recognized in the overall comparison of CRTs and LCDs is
that CRTs are a more mature technology than LCDs. Changes in LCD manufacturing processes
have likely occurred during the development and publication of this report. Therefore,
comparisons must be carefully drawn when evaluating the mature CRT to the newer LCD
technology.
5-9
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5.4 COST AND PERFORMANCE CONSIDERATIONS
5.4 COST AND PERFORMANCE CONSIDERATIONS
The focus of this study has been on the environmental effects associated with CRTs and
LCDs. The environmental attributes or burdens of a product are not expected to be considered
alone when evaluating the marketability and commercial success of a product. The cost and
performance of each monitor type are obviously critical components to a company's or
consumer's decisions of whether to produce or purchase a product. This section briefly
addresses a few direct costs associated with the monitors. A complete cost analysis, including all
direct costs (e.g., material costs) and indirect costs (e.g., environmental costs to society) are
beyond the scope of this report. Direct retail costs of the monitors and electricity costs are
presented herein.
The average retail price of 1997-2000 model year monitors, collected from the
manufacturers who supplied data for this project, as well as the performance information, are
presented in Table 5-3. Costs collected from current monitors on the market are presented in
Table 5-4. From Table 5-3, which represents primary data collected on the actual monitors
included in this study, the LCD is approximately 2.7 times more costly. More recent data show
that prices have come down, and the difference in prices between the CRT and LCD has also
been reduced.
Table 5-3. Primary cost and performance data collected from manufacturers for the CDP
Monitor
CRT monitor
(functional unit
aggregate)
LCD monitor
(functional unit
aggregate)
Display
Size
(inches)
17
15
Resolution
(pixels)
1024x768
1024x768
Brightness
range
(cd/m2)
86-154
200-300
Contrast ratio
range
200:1-300:1
Number of
Colors
"Full color"
"Full color"
Average cost
from primary
data
(US$)
$541
$1,450
— Not reported or not applicable.
A complete cost analysis would require assessing the costs from each life-cycle stage.
The costs presented above are retail costs that presumably represent the manufacturing costs, but
probably not external environmental costs, for example. The costs from the use stage can be
represented by the electricity costs during the use stage. The average cost of residential and
commercial electricity in the United States is approximately $0.021/MJ,2 and the CRT and LCD
monitors use about 2,290 and 853 MJ/functional unit, respectively, in the use stage baseline
scenario, which assumes a total of 13,547 hours per life over a period of 6.5 years (see Section
2.4.1.2). Therefore, the electricity costs to consumers during the use stages are $48 for the CRT
and $18 for the LCD. The amount of electricity consumed and the associated cost of that
electricity for each life-cycle stage in the baseline scenario are presented in Table 5-5.
This number was calculated from a value found at the following Web address:
www.eia.doe.gov/cneaf/electricity/ esr/tl 1 .txt.
5-10
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5.4 COST AND PERFORMANCE CONSIDERATIONS
Table 5-4. Cost and performance data for some currently selling CRTs and LCDs"
Monitor
Display
Size
(inches)
Resolution
(pixels)
Brightness
(cd/m2)
Contrast ratio
Number of
Colors
2001 Cost
($US)
CRTs
Monitor 1
Monitor 2
Monitor 3
17/16
17/16.1
17/16
1280x1040
1280x1040
1600x1200
—
— -
—
—
"High contrast, anti-static,
anti-glare coating."
—
—
— -
—
$158
$171
$316
LCDs
Monitor 1
Monitor 2 *
Monitor 3
Monitor 4 *
Monitor 5
15.1
15.1
15.1
15.1
15
1024x768
1024x768
1024x768
1024x768
1024x768
—
200
200 c
200
210C
200:1
250:1
200:1 c
250:1
350:1
16.7 million
16.7 million
1 6+ million
16.7 million
—
$349
$400
$439
$499
$554
" All information from Vol. EC23 of the eCOST.com catalog, except where noted otherwise.
* Data from the manufacturer's Web site except for prices, which where obtained from http://www.cdw.com on
8/29/01.
c Data are from the manufacturer's Web site.
— Not reported or not applicable.
Table 5-5. Life-cycle electricity costs (baseline scenario)
Life-cycle stage
Upstream
Manufacturing
Use
EOL
Total
CRT
Electricity use
(MJ/functional
unit)
(see Table J-3)
73.2
129
2,290
0.229
2,492
unit cost
($/MJ)
0.012"
0.012"
0.021 *
0.012"
—
Cost
($US)
$1.3
$1.5
$48
$0.003
$51
LCD
Electricity use
(MJ/functional
unit)
(see Table J-12)
8.55
278
853
0
1,140
unit cost
($/MJ)
0.012"
0.012"
0.021 *
0.012"
Cost
(SUS)
$0.10
$3.4
$18
0
$22
" 1999 U.S. average cost of electricity for the industrial sector is $0.0443/kWh. Assuming 3.6 MJ/kWh,
($0.0443/kWh)/(3.6 MJ/kWh) = $0.012/MJ. Source: www.eia.doe.gov/cneaf/electricity/esr/tll.txt. Note that the
use of the U.S. average cost is simply to compare costs among life-cycle stages, although the actual costs would be
mostly from Asia.
b 1999 U.S. average cost of electricity for the residential and commercial sectors is $0.0771/kWh. Assuming 3.6
MJ/kWh, ($0.0771/kWh)/(3.6 MJ/kWh) = $0.021/MJ. Source: www.eia.doe.gov/cneaf/electricity/esr/tll.txt.
5-11
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5.4 COST AND PERFORMANCE CONSIDERATIONS
The LCA is defined such that the monitor assessments are performed on a functionally
equivalent basis. To the extent possible, data were collected on functionally equivalent monitors.
The data presented in Table 5-3 are the range of specifications provided by the monitor
assemblers, but not necessarily from the manufacturers of all of the component parts. Therefore,
we are unsure if the specifications provided by the monitor assemblers also represent those of the
component parts, since the component parts manufacturers did not consistently supply
performance data as requested in the data collection questionnaire used in this study. However,
when companies were approached to participate in the study, they were informed of the
performance specification parameters within which the study boundaries were defined.
Therefore, it is assumed that they meet the specifications as presented in Chapter 1 (Table 1-2)
and in Table 5-3 and they perform relatively equivalently. In the primary data, the reported
brightness of the CRT was less than the LCD, otherwise, they are functionally similar.
5-12
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5.5 IMPROVEMENT ASSESSMENT OPPORTUNITIES & TARGETED AUDIENCE USES OF REPORT
5.5 IMPROVEMENT ASSESSMENT OPPORTUNITIES AND TARGETED
AUDIENCE USES OF REPORT
To meet the primary objective of providing the display industry with data to perform
improvement assessments, the industry should look at the manufacturing life-cycle stage, while
recognizing the influences of the other stages. CRT improvement opportunities could include
improved energy efficiency during glass manufacturing and display use, as well as reductions in
lead content. LCD improvement opportunities could also include improved energy efficiency,
especially during manufacturing. Certain materials, such as SF6 and its contribution to global
warming, may also be of concern and an area to focus on in future improvement assessments.
In addition, any improvement assessment should consider how changes in one life-cycle
stage will affect impacts in other stages. For example, in Chapter 4 we saw that the mercury
inputs and outputs from the intentional use of mercury in an LCD backlight are less than (by
mass) the mercury emissions from the CRT use stage, due to the relatively high energy usage by
the CRT and the emissions of mercury from electricity generation. In this example, we can see
that on a pure mass basis, a product's energy efficiency is a key consideration and any changes in
manufacturing should consider if it will affect changes in use. However, this project did not
conduct a quantitative risk assessment to determine where the greatest potential for mercury
exposure (and therefore risk) might occur. Consequently, we cannot definitively say whether it is
better to have a potentially less energy-efficient backlight that does not contain mercury or a
more energy-efficient backlight that does. Nonetheless, this analysis highlights the life-cycle
trade-offs that must be considered in an improvement assessment.
Another objective of this study was to provide an LCA model for future analyses.
Companies or individuals who have more current data for the CRT or LCD can apply them to the
model presented here. For example, changes in an individual process can be identified and
incorporated into the model. The other processes that are not expected to change significantly
can be left unchanged, and only limited data would need to be altered. This would reduce the
time and resources that would normally be required for a complete analysis.
Finally, those interested in comparing the results of the two monitors can apply their own
set of importance weights to each impact category to determine their individual decision. For
example, if energy impacts are much more important than aesthetics to a particular person, they
can weigh energy more heavily in concluding which monitor may have fewer environmental
impacts, while keeping in mind the data limitations and uncertainties, as well as cost and
performance considerations.
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5.6 SUGGESTIONS FOR FUTURE RESEARCH
5.6 SUGGESTIONS FOR FUTURE RESEARCH
Areas where future research could be conducted to refine and/or continue the use of the
results in this study are as follows:
• gather more information on energy use in glass manufacturing;
• develop consistent materials and fuel processing data in a national (or international) LCI
database that is updated regularly;
• refine and/or update some of the LCD manufacturing data (e.g., LNG data);
• collect more complete EOL data (e.g., remanufacturing data, and primary data for
incineration and landfilling) to determine better representation of the EOL impacts;
• conduct more research on EOL options for LCDs;
• collect more detailed data on landfilling and other treatment processes, such as water
treatment where no impacts were calculated;
• update manufacturing data to meet more recent monitor model years;
• conduct a more focused analysis on selected areas for detailed improvement assessments;
and
• evaluate process changes or other alternatives against an "average 1997-2000 model year"
to evaluate impacts of changes or improvements over time.
5-14
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APPENDIX A
APPENDIX A
FLAT PANEL DISPLAY TECHNOLOGIES
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APPENDIX A
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APPENDIX A
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APPENDIX A
FLAT PANEL DISPLAY TECHNOLOGIES
1. Background
Flat panel displays (FPDs) are increasingly gaining a presence in the computer display
market. They provide, for example, a more compact display as used in laptop computers and are
viable substitutes for cathode ray tube (CRT) displays. Other advantages over the CRT are
higher contrast, sunlight readable, more reliable, and more durable (i.e., require much less
maintenance) Koch and Keoleian, 1995). In general, the major disadvantages have been that the
resolution and quality of the image did not match that of CRTs. Several different types of FPD
technologies have been demonstrated and are in use to varying degrees. The major categories are
liquid crystal displays (LCD), plasma display panels (PDP), electroluminescent (EL), field
emission displays (FED), vacuum fluorescent displays (VFD), digital micromirror devices
(DMD), and light emitting diodes (LED). Table A-l briefly describes each FPD technology.
Although each technology has its own performance characteristics and is manufactured using
different materials and processes, most are generally comprised of two glass plates surrounding a
material that filters external light or emits its own light. These technologies use manufacturing
techniques more similar to the production of semiconductor chips than televisions. Most FPDs
control the color and brightness of each pixel (picture element) individually, rather than from one
source, such as the electron gun in the CRT. The different types of electronic information
display devices and how they are categorized are depicted in Fig. A-l.
1.1 Elimination of FPD Technologies from this Study
While there are several types of FPDs, two LCD technologies will be included in this
LCA, based on their applicability to be used as substitutes in the computer display market. LCDs
comprise approximately 87% of the FPD market (OTA, 1995). Currently, the largest market for
FPDs is in notebook computers and CRTs monopolize the desktop computer market. However,
FPDs are already moving into the desktop computer market. The LCD technology that best
meets the purpose and needs of this study is the amorphous-silicon thin film-transitor (a: Si TFT)
active matrix LCD (AMLCD). There are two variations of the a: Si TFT AMLCD that are
expected to dominate the desktop monitor market for LCDs: the traditional twisted nematic (TN)
mode and the in-plane switching (IPS) mode. Table A-l describes these technologies. Various
subtechnologies of LCDs are presented in Fig. A-2. The IPS mode is a non-nematic amorphous
silicon AMLCD. Note that all the subtechnologies listed in Fig A-2 are not described here; the
purpose is simply to show the complexity of different types of LCDs.
The PDP technology could be incorporated into the desktop computer market, especially
if computers and televisions begin to merge. However, plasma technology is generally designed
for large screens, and does not meet the specifications (e.g., diagonal size) of the functional unit
defined for this project. Therefore, PDP technology will not be included in the scope of this
project. FED and EL technologies are targeted toward military, medical, and high-end
commercial products because they possess particular characteristics (such as size, durability, and
high image quality) for those niche markets. Because these other FPD technologies are a small
fraction of the market, not targeted toward the desktop computer market, and/or do not meet the
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APPENDIX A
specifications of our functional unit, they are not included within the scope of this project. Table
A-l presents brief descriptions of various FPD technologies and whether or not they are included
in this LCA.
Table A-l. Flat panel display technologies
Technology
Description
Applicability to Project
Liquid Crystal
Displays (LCD)
A liquid crystal material, acting like a shutter,
blocks, dims, or passes light unobstructed,
depending on the magnitude of the electric
field across the material (OTA, 1995). A
backlight provides the light source.
Included in this study. Descriptions of the
subtechnologies and whether or not they
are included in the study are presented
below.
(1) Passive matrix
(PMLCD)
Liquid crystal (LC) material is sandwiched
between two glass plates, which contain
parallel sets of transparent electrical lines
(electrodes) in a row and column configuration
to form a matrix. Every intersection forms a
pixel, and the voltage across the pixel causes
the LC molecules to align and determines the
shade of that pixel (OTA, 1995).
Traditionally for low-end applications
(e.g., calculators, wrist watches). Higher
end applications use a super-twisted
nematic (STN)1 construction. The liquid
crystal material is twisted between 180 and
270 degrees which improves the contrast
between the "on" and "off states, resulting
in a clearer display than with the twisted
nematic (twisted only 90 degrees) (OTA,
1995; MCC, 1997). However, cost and
performance issues limit this technology
from wide application in the desktop
market and therefore, it will not be
evaluated in this study.
(2) Active matrix
(AMLCD)
Similar to the PMLCD except an electronic
switch at every pixel provides faster switching
and more shades. The addressing mechanism
eliminates the viewing angle and brightness
problems suffered by PMLCD. Requires more
backlight than PMLCD due to the additional
switching devices on the glass (at each pixel).
Various switching types are listed below:
Provides vivid color graphics in portable
computer and television screens (OTA,
1995). This technology meets the
functional unit specifications in this study.
Specific subcategories are described
below.
modulating methods for LCD technologies include twisted nematic (TN), super-twisted
, and film-compensated STN (OTA, 1995), The STN is the current
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APPENDIX A
Table A-l. Flat panel display technologies
Technology
Description
Applicability to Project
AMLCD Switch Types:
(2a) Thin-film transistor (TFT):
The transistor acts as a valve allowing current
to flow to the pixel when a signal is applied.
The transistors are made of various materials
including: amorphous silicon (a:Si),
polycrystalline silicon (p:Si), non-Si[CdSe]
(Castellano, 1992). Two different TFT light
modulating modes are twisted nematic (TN)
and in-plane switching (IPS) (DisplaySearch
1998). In comparison to the TN mode, the
IPS mode requires more backlight but fewer
manufacturing steps.
The current standard AMLCD switching
mechanism for computer displays is a:Si
TFT. Polycrystalline Si is not suitable for
larger than about 5" displays. Both the TN
and IPS a:Si TFT AMLCD technologies
are analyzed in this project.
(2b) Diode matrix:
The diode acts as a check valve. When
closed, it allows current to flow to the pixel
charging it. When opened, the pixel is
disconnected and the charge is maintained
until the next frame (Castellano, 1992).
The diodes are found to short easily and
must be connected in series to achieve long
life usability. The diode displays are also
limited in size smaller than that of the
functional unit.
(2c) Metal-insulator metal (MIM):
The MIM is a diode type switch using metal-
insulated-metal fabrication techniques (OTA,
1995).
Temperature sensitive, which creates gray
scale nonuniformities. They are also size
limited like other diode type displays and
therefore not included in this study.
(3) Active addressed
LCD
Hybrid of passive and active matrix. The
pixels are addressed using signals sent to the
column and row as determined using an
algorithm encoded into an integrated circuit
(1C). The 1C drives each row of pixels more
or less continuously and drives multiple rows
at one time (OTA, 1995)
Employed in notebook and desktop
monitors > 12.1". However, they need
special drivers (OTA, 1995), have slow
response times, and their contrast worsens
as panel size increases (Young, 1998).
Therefore, this technology does not meet
the specifications of the functional unit and
is excluded from evaluation in this study.
(4) Plasma-addressed
liquid crystal (PALC)
The pixel is addressed using row electrodes,
which send the signal, and column gas
channels, which conduct a current when
ionized (OTA, 1995).
PALC displays are in development to be
used as large low cost displays. Production
of the displays have not yet occurred and
they are not included in this study.
(5) Ferroelectric
LCDs (FLCD or
FELCD)
The pixel is addressed using positive or
negatives pulses to orient the crystals. The
positive pulse allows light to pass (light state)
and the negative pulse causes the blockage of
light (dark state) (Castellano, 1992). A
ferroelectric liquid crystal is bistable and holds
it polarization when an electric field is applied
and removed (Peddie, 1994). They are also
called surface stabilized ferroelectric (SSF)
LCD.
Has high resolution with very good
brightness, but limited color palette
(Peddie, 1994). Limited color palette does
not meet color specification of functional
unit.
A-3
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APPENDIX A
Table A-l. Flat panel display technologies
Technology
Description
Applicability to Project
Plasma Display
Panels (POP)
An inert gas (e.g., He, Ne, Ar) trapped
between the glass plates emits light when an
electric current is passed through the matrix of
lines on the glass. Glow discharge occurs
when ionized gas undergoes recombination.
lonization of atoms occurs (electrons are
removed), then electrons are recombined to
release energy in the form of light. Full color
plasma displays use phosphors that glow when
illuminated by the gas (OTA, 1995).
Established technology. Good for large
screens (e.g., wall-mounted televisions),
but are heavier and require more power
than LCDs (OTA, 1995). Designed for
large screens and are larger displays than
specified for desktop applications.
Therefore, not included in this study.
Electroluminescent
Displays (EL)
A phosphor film between glass plates emits
light when an electric field is created across
the film (OTA, 1995). EL uses a
polycrystalline phosphor (similar to LED
technology which is also an electroluminescent
emitter, but uses a single crystal semi-
conductor). ELs are doped (as a
semiconductor) with specific impurities to
provide energy states that lie slightly below
those of mobile electrons and slightly above
those of electrons bound to atoms. Impurity
states are used to provide initial and final
states in emitting transitions (Peddie, 1994).
Also referred to as thin-film EL (TFEL).
Variations: AC thin-film EL (AC-TFEL),
active matrix EL (AMEL), DC EL, organic
EL.
Lightweight and durable. Used in
emergency rooms, on factory floors, and in
commercial transportation vehicles (OTA,
1995). Problems found in the power
consumption and controlling of gray levels.
Targeted toward military, medical, and
high-end commercial products, therefore
not included in the scope of this project.
Field Emission
Displays (FED)
Flat CRT with hundreds of cathodes (emitters)
per pixel (form of cathodeluminescent
display); eliminates single scanning electron
beam of the CRT. Uses a flat cold (i.e., room
temperature) cathode to emit electrons.
Electrons are emitted from one side of the
display and energize colored phosphors on the
other side (OTA, 1995; Peddie, 1994).
Not commercially available, but
anticipated to fill many display needs
(OTA, 1995). Could potentially apply in
all LCD and CRT applications. High
image quality as with CRT, but less bulky
and less power use than with CRT. A
number of roadblocks to this technology
taking over the AMLCD market include
proven manufacturing processes (problems
found in the reliability and reproducibility
of the devices), efficient low-voltage
phosphors, and high voltage drivers. The
technology is targeted toward military,
medical and high-end commercial products
and not included in current study.
Vacuum Fluorescent
Displays (VFD)
Form of cathodeluminescent display that
employs a flat vacuum tube, a filament wire, a
control grid structure, and a phosphor-coated
anode. Can operate at low voltages since very
thin layers of highly efficient phosphors are
coated directly onto each transparent anode
(Peddie, 1994).
VFDs offer high brightness, wide viewing
angle, multi-color capability and
mechanical reliability. Used in low
information content applications (e.g.,
VCRs, microwaves, audio equipment,
automobile instrument panels, etc.). No
significant uses seen for computer displays
(Peddie, 1994).
A-4
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APPENDIX A
Table A-l. Flat panel display technologies
Technology
Description
Applicability to Project
Digital Micromirror
Devices (DMD)
Miniature array of tiny mirrors built on a
semiconductor chip. The DMD is used in a
projector that shines light on the mirror array.
Depending on the position of a given mirror,
that pixel in the display reflects light either
onto a lens that projects it onto a screen
(resulting in a light pixel) or away from the
lens (resulting in a dark pixel) (OTA, 1995).
Just beginning to be used mainly as
projection devices and has not been
developed for use that would match the
functional unit (OTA, 1995).
Light Emitting
Diodes (LED)
The LED device is essentially a semiconductor
diode, emitting light when a forward bias
voltage is applied to a p-n
junction. The light intensity is proportional to
the bias current and the color dependent on the
material used. The p-n junction is formed in a
III-V group material, such as aluminum,
gallium, indium, phosphorous,
antimony, or arsenic.
For low information display applications,
which makes it not capable of meeting the
requirements of the functional unit. Color,
power, and cost limitations prevent the
emergence into the high information
display market (Castellano, 1992).
Electrochromic
display
Open-circuit memory using liquid electrolytes
(Peddie, 1994, p. 214). Non-emitter (as
LCDs), as opposed to emitters (e.g., EL, FED,
POP).
Outstanding contrast and normal and wide
viewing angles; open-circuit memory.
Complex and costly involving liquid
electrolytes, poor resolution, poor cycle
life, lack of multicolor capability, etc. Not
suitable for computer displays in past;
however, new technology may be
promising (Peddie, 1994).
Light Emitting
Polymers
Developing technology (Holton, 1997).
Developing technology.
A-5
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APPENDIX A
Electronic Information Displays
Projection
Direct-view
Off-screen
Cathode-
ray tube
Light Cathode-ray Flat-panel Coherent Non-coherent
valve tube (CRT)
Emitter
Non-emitter
Luminescence
Incandescence
Electroluminescence
Cathodoluminescence
(CL)
Polycrystalline Single
phosphor crystal
semiconductor
Electroluminescence Light-
(EL) emitting
diode (LED)
Direct-
view
discharge fllament
(GD)
Indirect-
view
filament
quid
allinity
.C)
Col
oidal
suspension
(CS)
Electr
mec
(
(EM)
Vacuum
fluorescence
(VFD)
Flat CRT/
field emission
display
(FED)
Electrochromism Electroactive
(EC) solid
(ES)
Plasma display
panel (POP)
Figure A-l. Classification of Electronic Information Displays. Source: Adapted from Tannas 1985.
A-6
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APPENDIX A
Liquid Crystal Displays!
Hematic
Direct
Bi-stabt«
Multiplexed
Twisted-Hematic FE
Guest Host
Dynamic Sacttering
Nodulated TN
Polymer Dispersed
Active Matrix
Standard TNFE
ECS
OKI
Silicon
Amorphous Si
poly Si
Deposited
Recrystallized
Bulk (MOS)
Smectlc A
ThermaUeUetrlc
Electro-conic
Smectlc C
Ferroelectric SSftc
Guest Host
Plasm Addressed
Figure A-2. LCD subtechnologies. Source: Catellano 1992.
A-7
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APPENDIX B
APPENDIX B
DESCRIPTIONS OF LIQUID CRYSTAL DISPLAY (LCD) TECHNOLOGY AND
AMORPHOUS SILICON THIN-FILM TRANSISTOR (a:Si TFT) TECHNOLOGY
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APPENDIX B
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APPENDIX B
PRINCIPLES Of LCD TBCHMOLOOT
WHATIS
AllQUID
PRINCIPLES
OF LCD
LCD
PRODUCTION
AMOHPHCRUS
•StTFT
DIRECT VUTW
MONITORS
In this section, we will explain everything ranging from the properties oi'liquid crystal molecules to the basic principle of
display technology by using TN type liquid crystals as an example.
TJie parallel arrangement of liquid crystal molecules along grooves
When coming into contact with grooved surface in a fixed direction, liquid crystal molecules line up parallel along the
grooves.
I®
Natural Mate
Molecules are arranged in a
loosely ordered fashion with their
long axes parallel.
When coming into contact with
a finely grooved surface
(alignment layer).
Molecules line up
parallel along
grooves.
When liquid crystals are sandwiched between upper and lower plates, they line-up with grooves pointing in
directions 'a' and 'b,' respectively
The molecules along the upper plate point in direction 'a1 and
those along the lower plate in direction T>,' thus forcing the
liquid crystals into a twisted structural arrangement.
(figure shows a 90-degree twist)
(TN type liquid crystal)
Light travels through the spacing of the molecular arrangement
The light also "twists" as it passes through the twisted liquid crystals
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APPENDIX B
Light passes through liquid crystals, following the direction in which
(he molecules are arranged. When the molecule arrangement is twisted
90 degrees as shown in the figure, the light also twists 90 degrees as it
passes through the liquid crystals.
Liaht bends 90 degrees as it follows the twist of the molecules
Molecules rearrange themselves when voltage is applied
When voltage is applied to the liquid crystal structure, the twisted light passes straight through.
Voliafl e
"
The molecules in liquid crystals are easily rearranged by
applying voltage or another external force. When voltage is
applied, molecules rearrange themselves vertically (along
with the electric field) andlight passes straight through
along the arrangement of molecules.
Blocking light with two polarizing filters
When voltage is applied to a combination of two polarizing filters and twisted liquid crystal, it becomes a LCD display.
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APPENDIX B
Light passes when two polarizing filters are arranged wiih polarizing axes as shown above, left.
Light is blocked when two polarizing filters are arranged with polarizing axes as shown above, right.
TN type LCDs
A combination of polarizing filters and twisted liquid crystal creates a liquid crystal display.
Light
Voltage
When two polarizing niters are arranged
along perpendicular polarizing xxes, light
entering from above is re-directed 90
degrees along the helix arrangement of the
liquid crystal molecules so that it passes
through the lower filter.
When voltage is applied, the liquid crystal
molecules straighten out of their helix
pattern and stop redirecting the angle of the
light, thereby preventing light from passing
through the lower filter.
This Sgure depicts die principle behind typical twisted nematic (TN) liquid crystal displays. In a TN type LCD, liquid
crystals in which the molecules form a 90-degree twisted helix, are sandwiched between two polarizing filters. When no
voltage is applied, light passes; when voltage is applied, light is blocked and the screen appears black. In other words, the
voltage acts as a trigger causing the liquid crystals to function like the shutter of a camera.
LCD
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APPENDIX B
TKT TECHMOLOOY
WHAT ES
AUOUID
-py
PRINCIPLES
OF LCD
At.VSHfHCS.US
•SSTFT
PROJECTORS
PANELS AND
BIRECTVtEW
MQNirans
Active matrix LCDs, which are typically used in products such as LCD projectors, are controlled by a s\vitchin° element
known as a thin-film transistor or thin-tilm diode placed at each pixel.
The fundamental concept was revealed in 1961 by RCA of America, a U.S. company, but basic research only be»an in
the 1970's.Amorphous Si TFT LCDs introduced in 1979 and 1980 have become the mainstream for today's active matrix
displays. These units place an active element at each pixel, and taking advantage of the non-linearity of the active
element, are able to apply sufficient drive-voltage margin to the liquid crystal itself, even with the increase in the number
of scan lines.
As shown in Figure 1, TFT LCDs that use amorphous Si thin-film transistors (TFTs) as the active elements are becoming
the mainstream today, and lull-color displays achieving contrast ratios of 100:1 and which compare favorablv to CRTs
are being developed.
Color fitter
Polarizer
The driver electronics tor TFT LCDs consist of
data-line drive circuitry that applies display signals
Molecules J° the data lines (source drivers) and scanning line
Source <^r've circi'try that applies scanning signals to the
, Busline gate lines (gate drivers). A signal control circuit to
control these operations and a power supply circuit
complete the system.
Liquid crystal materials used in TFT LCDs are TN
'O/iantalion (twisted neraatic) liquid crystals, but despite the
gin, fact that pixel counts have increased and a drive
element is placed at each pixel, we have still been
able to rapidly increase the contrast, viewing angle,
and image quality of these displays.
busline
Backlighting
Figure 1 Construction of TFT LCD
However, manufacturing technologies to fabricate several hundred thousand such elements onto the surface of a large
screen are extremely problematic, and the fundamental approach developed in 1987 is still being used today.
In 1988, Sharp developed a 14-inch TFT color TV, and with this development of a futuristic wall-mount TV, TFT LCDs
created the foundation tor manufacture and introduction of large-screen color displays.
Remitter discovered liquid crystals almost 100 years ago, and today, bolstered by customer needs and the new and
special technologies and materials that a manufacturer can offer to meet those needs, liquid crystals have made huge
strides.
At this opportunity, we would, to make the whole world aware of the potential of LCDs, and as new manufacturers enter
the market, become the trigger that raises this awareness to new levels.
In the evolution of LCD display manufacturing, the burden of undertaking aggressive development of application
products has been considerable. In addition to notebook and sub-notebook PCs that have been the mainstream
applications for LCDs in the past, there has been significant growth in areas which take advantage of the unique
characteristics of LCD displays, such as compact size, thin profile, and low power consumption to create products which
could not be produced using CRTs, such as LCD TVs, ViewCams, new portable information tools, etc. In addition, for
large projection TVs, it has now become possible to develop products that are more compact and lighter in weight than
conventional CRT-based models, and LCDs are rapidly becoming the mainstream display device in this field.
In this way, LCD displays have expanded into application areas mat were once niches belonging solely to CRTs, and me
development of numerous key technologies that have the potential to further expand their application product areas
continues.
Thanks to the development ot'TFT LCD displays and the synergistic evolution (spiral evolution) with LCD application
devices and equipment, such as PC notebooks and computer monitors, A/V equipment, car navigation systems, game
devices, etc., we can anticipate the growth of new demand-generating products. LCDs have emerged as the likely winner
among flat-panel displays for the new information-oriented society. As we approach the dawn of the multimedia era
which will see the convergence of video, computers, and communications, a critical need is emerging for innovations in
displays that link man and machine through our sense of sight.
The driving force behind LCD manufacturing are recently developed amorphous-Si TFT LCD technologies which
represent breakthroughs in the areas of 1) higher aperture ratios, 2) wider viewing angles, and 3) EMI (electromagnetic
interference) reduction, as well as low-temperature polycrystalline Si TFT LCD display technologies. Thanks to these
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APPENDIX B
breakthroughs, a new direction has emerged in 1996 which will make the best use of these key technologies in LCD
applications. For example, higher aperture ratio technologies are being used in LCD displays intended for PC notebooks.
wider viewing angle and lower EMI technologies are being used in LCDs destined for LCD monitors, and
low-temperature poiycrystalline Si TFT LCD technologies are being used as super-fine dot-pitch light valves for
high-definition projection TV systems.
In the future, promising new technologies can be expected to spawn the next generation of new LCD application
products based on high-performance LCD display systems ("systems-on-panel") that takes null advantage of integrated
drive and control circuitry.
tco
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APPENDIX B
References
Sharp. 1998. Information found on a Web page from Sharp USA. Web site available at:
.
B-6
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APPENDIX C
APPENDIX C
CRITICAL REVIEW
-------
APPENDIX C
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APPENDIX C
APPENDIX C
CRITICAL REVIEW
Table C-l. Computer Display Project Core Group* and Technical Work Group Members
Contact
Salla Ahonen
Heather Bowman
Reggie Caudill
Bob Donofrio
Holly Evans
Co-Chair, Core Group
Bruce Gnade
Tony Hainault
Kathy Hart*
Co-Chair, Core Group
Edwin Henderson*
David Isaacs*
former Co-Chair, Core Group
Mikko Jalas
Tim Jarvis
Greg Keoleian
Lori Kincaid*
J. Ray Kirby
Jonathan Koch
David Lear
Clare Lindsay
John Lott
Jeff Lowry
Carole McCarthy
Timothy Mann
Organization
Environmental Issues, Nokia Research Center,
Nokia
Electronics Industry Alliance
New Jersey Inst. of Tech. Research Center
Display Device Consultants
Electronics Industry Alliance
DARPA
Minnesota Office of Environmental Assistance
US EPA, Office of Prevention Pesticides and
Toxic Substances
US EPA, Office of Prevention Pesticides and
Toxic Substances a
Electronics Industry Alliance a
Environmental Issues, Nokia Research Center,
Nokia
The SemiCycle Foundation
U. of Michigan, School of Natural Resources and
the Env.
Univ. of TN
Center for Clean Products and Clean
Technologies
IBM
GE Power Systems
Compaq Computer Corp.
U.S. EPA, Office of Solid Waste
DuPont Electronic Materials
Techneglas
McCarthy Environmental Consulting
IBM
Location
Helsinki, Finland
Arlington, VA
Newark, NJ
Ann Arbor, MI
Arlington, VA
Arlington, VA
St. Paul, MN
Washington, DC
Washington, DC
Arlington, VA
Helsinki, Finland
Austin, TX
Ann Arbor, MI
Knoxville, TN
Research Triangle
Park, NC
Schenectady, NY
Houston, TX
Arlington, VA
Research Triangle
Park, NC
Columbus, OH
Duxbury, MA
Loganville, GA
C-l
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APPENDIX C
Table C-l. Computer Display Project Core Group* and Technical Work Group Members
Contact
Frank Marella
Co-Chair, Technical Work
Group
John Mathews
Jay Mathewson
Colleen Mizuki*
Amanda Monchamp
Rick Nolan
Bob Pinnel*
Greg Pitts*
Gene Proch
Gloria Schuldt
Eileen Sheehan
Dipti Singh*
Co-chair, Technical Work
Group
Doug Smith
Ted Smith*
David Spengler*
Maria Socolof*
Dan Steele
Larry Stone
Butch Teglas (Delmer F.)
Valerie Thomas
David Thompson
Donna Timmons
Dani Tsuda*
Lucian Turk
Laura Turbini
Victoria Wheeler
Organization
Sharp Electronics Corporation
Envirocycle
Eastman Kodak Co.
Microelectronic & Computer Technology
Corporation a
Electronics Industry Alliance a
Motorola
U.S. Display Consortium
Microelectronic & Computer Technology
Corporation a
Corning Asahi
Microelectronic & Computer Technology
Corporation a
U.S. EPA, P2 Team, Region 9
US EPA, Office of Prevention Pesticides and
Toxic Substances
Sony Electronics Inc.
Silicon Valley Toxics Coalition
Digital Equipment Corporation
Univ. of Tennessee
Center for Clean Products & Clean Technologies
Motorola MD FPD 10
ESIH and Chemical Operations Flat Panel
Display Division
Compaq Computer Corp.
Philips Consumer Electronics
Princeton Univ. Ctr. For Energy & Env. Studies
Matsushita Electronic Corporation of America
Eastman Kodak Co.
Apple Computer Inc.
Dell Computer
Georgia Institute of Technology
Eastman Kodak Co.
Location
Mahwah, NJ
Hallstead, PA
Rochester, NY
Austin, TX
Arlington, VA
Austin, TX
San Jose, CA
Austin, TX
Austin, TX
San Francisco, CA
Washington, DC
San Diego, CA
San Jose, CA
Maynard, MA
Knoxville, TN
Tempe, AZ
Houston, TX
Knoxville, TN
Princeton, NJ
Secaucus, NJ
Rochester, NY
Cupertino, CA
Austin, TX
Atlanta, GA
Rochester, NY
C-2
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APPENDIX C
Table C-l. Computer Display Project Core Group* and Technical Work Group Members
Contact
Ross Young
former Co-Chair,
Technical Work Group
Organization
Display Search
Location
Austin, TX
* Core Group members (subset of Technical Work Group)
a Affiliation at time of involvement in project.
Table C-2. U.S. EPA Design for the Environment Workgroup Members for the
Computer Display Project
Name
Andrea Blaschka
Susan Dillman
Franklyn Hall
Kathy Hart
Karen Hogan
Susan Krueger
Fred Metz
Dipti Singh
Jerry Smrchek
Division/Branch
Risk Assessment Division/Existing Chemicals Assessment Branch
National Program Chemicals Division/Technical Branch
Economic, Exposure, and Technology Division/Chemical Engineering Branch
Economics, Exposure, and Technology Division/Design for the Environment
Risk Assessment Division/Science Support Branch
Economics, Exposure, and Technology Division/Economic and Policy Analysis
Branch
Economics, Exposure, and Technology Division/Industrial Chemistry Branch
Economics, Exposure, and Technology Division/Design for the Environment
Risk Assessment Division/Existing Chemicals Assessment Branch
C-3
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APPENDIX D
APPENDIX D
TECHNICAL MEMORANDUM:
Life-Cycle Inventory Approach for Materials Extraction and
Materials Processing Life-Cycle Stages
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APPENDIX D
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APPENDIX D
APPENDIX D
TECHNICAL MEMORANDUM:
Life-Cycle Inventory Approach for Materials Extraction and
Materials Processing Life-Cycle Stages
1. INTRODUCTION
1.1 Background
The U.S. Environmental Protection Agency's Design for the Environment Program
Computer Display Project (CDP) is conducting an environmental life-cycle assessment (LCA)
that will evaluate the relative environmental impacts of cathode ray tubes (CRT) and liquid
crystal display (LCD) computer monitors. The major life-cycle stages of a product system
include materials extraction, materials processing, product manufacturing, product use, and final
product disposition (end-of-life). An LCA evaluates the relative environmental impacts of a
product system and is defined in greater detail in Chapter 1 of the main report. An LCA
generally consists of four phases: goal definition and scoping, life-cycle inventory (LCI), life-
cycle impact assessment (LCIA), and life-cycle improvement assessment.
The activity of quantifying the inputs (e.g., materials, utilities) and outputs (e.g.,
emissions, wastes) of a product system is the LCI phase of an LCA. A product system is made
up of the multiple processes that help produce, use, or dispose of the product. Each process
typically has an inventory that consists of inputs and outputs for each process. Therefore, an LCI
of a product system consists of several inventories for processes throughout the life-cycle of the
product. This technical memorandum (TM) addresses the LCIs related to two major life-cycle
stages: materials extraction and materials processing, which together will be referred to as the
life-cycle stages that are "upstream" of the product manufacturing stage. Ideally, transportation
associated with those stages is also included. This TM will describe the approach to choosing
the upstream data from secondary sources that will be included in the CDP analysis.
1.2 Purpose and Scope of this Technical Memorandum
The purpose of this TM is to present the approach for obtaining process-specific
inventory data related to extraction and processing of the materials needed to produce a CRT and
LCD computer monitor. Collecting these upstream inventory data can involve dozens of
upstream processes because there are dozens of materials used to produce CRTs and LCDs.
Therefore, decision rules are typically used to limit which materials to include in the scope of the
LCA, and existing data from secondary sources are generally relied upon. For inventories related
to materials extraction and materials processing, various databases with input and output LCI
data exist for materials commonly used in industry. The existence of these inventories, and the
limited resources available for collecting primary inventory data for the entire life cycle, result in
the use of secondary data for upstream processes. In the CDP, more emphasis will be given to
collecting primary data for product manufacturing and end-of-life processes. This TM identifies
initial materials considered for inclusion in the upstream life-cycle stages. Actual material lists
from the inventories collected from the primary data collection efforts were not available until
D-l
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APPENDIX D
after data collection had to begin for the upstream processes. Therefore, initial materials were
identified to help determine which secondary data to obtain. Once actual materials from the
manufacturing stage inventory were identified, the selected secondary data source was checked
for the appropriate data sets to be included in the study. This TM addresses the initial steps for
choosing which upstream data source to use, by identifying and prioritizing several data sources.
The remainder of this TM will present a brief summary of results, the methodology for selecting
secondary upstream data for the CDP, detailed results in terms of preferred data sources, and the
limitations to using the upstream data for the CDP.
2. RESULTS SUMMARY
Based on initial material lists and project decision rules, approximately 40 materials
(including some material groups) were initially identified as materials for which upstream data
inventories should be included in the CDP LCA. Nine data sources (i.e., studies and/or
databases) were evaluated to determine which upstream data would be used for these and other
materials that might be identified in the CDP. Two databases were disregarded because the data
are not or will not be available to the public. The remaining seven were reviewed for their
applicability to the CDP. Complete inventory data for all currently identified CDP materials
were not available from any one of the databases/studies alone. Therefore, a hierarchy of
preferred data has been chosen for upstream data from secondary sources. The most preferred
data is that from the Environmental Information and Management Explorer (EIME) database
developed by Ecobilan (Ecobalance), a company based in France.
EIME is an LCA software package that specializes in electronics and the electronics
industry and currently includes 18, with forthcoming updates expected to bring it to 21 materials
specific to the CDP. The database is immediately available, and although it is relatively
expensive, it may be attainable at a negotiated price (Glazebrook 1999). The EIME data do not
fulfill all the CDP's upstream data requirements and therefore, other databases will be needed.
Twelve materials were not found in any of the databases and may require additional research
from secondary or primary sources to complete the CDP product system inventories. It appears,
however, that EIME, supplemented with Ecobalance's Database for Environmental Analysis and
Management (DEAM) will cover most materials needed in the CDP.
3. METHODOLOGY
The method for determining the upstream data that will be used for the CDP depends on
which materials need to be included in the upstream evaluation and what existing databases are
currently available for those materials. This section consists of three subsections that present the
following: (1) how the preliminary list of materials were identified; (2) which data sources were
considered for use as CDP upstream inventory data; and (3) the selection criteria for choosing
which upstream data to include in the CDP.
3.1 Materials Selection
The first step to selecting upstream data sources is to identify what materials are of
interest to the project. Primary data collected from manufacturing facilities will provide a list of
upstream materials to consider in the upstream stages. However, the materials inventory from
D-2
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APPENDIX D
the CDP product manufacturing stage was not yet complete when upstream data collection
needed to begin to meet project time and budget constraints. Therefore, a preliminary list of
materials used to manufacture the monitors was identified by disassembling a CRT and LCD and
by reviewing the literature on manufacturing processes. The list was then slightly reduced based
on decision rules to limit the scope of the project. This preliminary list is then used to help
choose preferred sources of upstream data for materials of interest in the CDP. The following
subsections describe the bills of materials of the LCD and CRT, the decision rules applied to the
bills of materials, and the list of selected materials for upstream data collection.
3.1.1 Bills of Materials
A 15" CRT and a 15" LCD desktop monitor were disassembled, to the extent they could
be manually separated, into their component parts/materials and each of these parts was weighed
using Mettler analytical balances. A 17" CRT (the CDP functional unit) was not available for
disassembly and therefore it is assumed that the percent contribution of materials in the 15" CRT
and the 17" CRT are equivalent, which is an adequate assumption for the purposes of identifying
major product materials.
Primary (also referred to as "product") materials are defined as those that become part of
the final assembled monitor. Bills of materials of the CRT and LCD monitors were compiled to
quantify the mass contribution of each primary material and component in each monitor. Where
individual materials could not be discerned, component parts consisting of multiple materials
were identified and weighed. These bills of materials are presented in the CDP's Industry and
Technology Profile Document (MCC 1998). The material makeup of some component parts
[e.g., thin-film transistors (TFTs) on LCD glass substrate or phosphors on CRT glass substrate]
were identified from published literature (i.e., secondary sources) (O'Mara 1993, DisplaySearch
1998, FCR 1996, MCC 1993, ECT 1980). Simultaneous and subsequent work on the CDP
involved obtaining more details on the makeup of certain component parts from manufacturers
(i.e., primary sources) through data collection questionnaires.
The next step was to identify common ancillary (also referred to as "process") materials
used in product manufacturing, which were found from secondary sources (O'Mara 1993,
DisplaySearch 1998, FCR 1996, MCC 1993, ECT 1980) and reviewed by industry experts.
These ancillary materials were added to the primary bills of materials for consideration in the
LCA (MCC 1998). Additional ancillary materials were identified from primary sources during
concurrent manufacturing data collection activities.
3.1.2 Decision Rules
Due to the complexity of the CRT and LCD monitors, and for any LCA, the boundaries
of the analysis must be clearly defined. Thus, the following decision rules for choosing the
materials to be evaluated were developed and applied to the primary and ancillary bills of
materials. Three major categories of decision criteria were used to select materials for detailed
analysis in the LCA: (1) mass contribution; (2) potential environmental and/or energy
significance; and (3) technological importance. A priority hierarchy was developed (Figure 1)
using a combination of these criteria.
D-3
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APPENDIX D
MATERIAL/COMPONENT INPUTS:
- >5% of total mass
environmental concern
- energy concern
functionally significant
- physically unique
-1-5% of total mass
i- <1% of total mass^
L- not otherwise
significant /Excluded from
.or unique.
analysis
Figure 1. Decision rule hierarchy
The first criterion is applied by including materials that constitute greater than or equal to
1% of the monitor by mass. Materials constituting more than 5% will be given greater emphasis
in the LCA. Mass is a simple measure by which to select important materials for consideration
in the LCA because in many cases, the larger the material, the greater the impact. This is true for
resource consumption impacts which are equivalent to the amount of material used. However,
other impact categories may not be equivalent to the amount of material consumed, and simply
eliminating materials based on mass alone may exclude important impacts from an
environmental life-cycle perspective. Therefore, under the second criterion, materials were also
included if they have a potential environmental/health impact (e.g., they may be toxic) or use
large amounts of energy to produce. The environmental criterion decision rule refers to materials
that may pose risks to the public, occupational workers, or the ecosystem from manufacturing,
use, or disposal of the material. The primary and ancillary materials were reviewed by a team of
experts at the University of Tennessee and were compared to regulatory lists and other sources
(Klaassen et al. 1986, EPA 1998, ChemFinder 1998, SRC 1998) to identify materials with known
or potential environmental concerns. When impacts are calculated in the LCIA, a more rigorous
review of toxicity data and environmental parameters will be conducted to provide quantitative
impact measures.
The third decision rule criterion applies to materials that are critical to the technology
(e.g., LCD TFT materials or the CRT phosphors). This is intended to ensure that other materials
of potential importance are not overlooked in the LCA. Furthermore, because the LCA will be
comparative in nature, greater emphasis will be placed on materials that are physically unique to
a display technology.
For the materials meeting the top tier of the decision rule hierarchy (Figure 1) in the CDP,
attempts are made to obtain secondary data for those upstream material processes. Materials in
the middle segment of the triangular hierarchy scheme are given lower priority, but included, if
D-4
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APPENDIX D
available. Finally, the last segment of the triangle would contain materials excluded from the
analysis.
3.1.3 Material Selection Results
The materials identified here are for selecting which materials require the collection of
input and output inventory data from materials extraction, materials processing, and associated
transportation, collectively referred to as the "upstream" life-cycle stages. The inventories from
each of these life-cycle stages are then used to calculate impacts of the various impact categories
considered in the analysis.
The total masses of the CRT and LCD that were disassembled were approximately 12.8
kg and 5.15 kg, respectively. The printed wiring boards (PWBs) and their components were
excluded from these weights and from the following materials analysis because they are treated
as complex display components not broken down by individual materials. The CRT consists of
approximately 17 primary materials and the LCD is comprised of about 23 primary materials
(MCC 1998). The major primary materials by weight (>1%) in the CRT and LCD are listed in
Table 1 with their corresponding components. Figures 2 and 3 depict the percent contribution of
each of those materials to the overall monitor. For the CRT, eight materials were greater than or
equal to 1% and only three [glass, steel, and high impact polystyrene (HIPS)] were greater than
5% of the weight of the monitor. The LCD had seven materials greater than or equal to 1%, five
of which were greater than 5% [steel, polycarbonate, acrylonitrile butadiene styrene (ABS),
polyester, and glass]. The items in bold in Table 1 represent the materials that are >5% for both
the CRT and LCD. Other primary materials to be included in the LCA, based on the
environment and technology decision rules, are presented in Table 2. The primary materials that
were excluded due to mass are presented in Table 3.
Ancillary materials, such as those required for photolithography, are used in greater
quantities for LCDs than CRTs. Preliminary literature searches (O'Mara 1993, DisplaySearch
1998, FCR 1996, MCC 1993, ECT 1980) found four ancillary materials for CRTs and 12 for
LCDs (MCC 1998). The latter portion of Table 2 presents the ancillary materials that are
included for either technological or environmental importance. The mass criterion for ancillary
materials will be identified through responses to data collection questionnaires distributed to
manufacturers participating in the project. Table 3 shows the ancillary materials that were
preliminarily excluded based on environmental and technical criteria because mass data for
ancillary materials are not yet available.
Table 1. Primary materials comprising >1% by mass of a CRT or LCD monitor and
associated componentsa
Material
ABS
Aluminum (Al)
Copper (Cu)
P'f^rritf^-mQ crnf^t
Associated component(s)
CRT
Aluminum shielding, power
board heat sink, connectors
Deflection yoke
T^f^flf^ntinn \/nVf^
LCD
Base/stand
Power supply heat sink, TFT
metal
D-5
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APPENDIX D
Table 1. Primary materials comprising >1% by mass of a CRT or LCD monitor and
associated componentsa
Material
Glass (e.g., borosilicate) b
Glass (lead oxide)
Lead (Pb) c
Plexiglas
Polycarbonate
Polyester
Polystyrene, high-impact
(HIPS)
Silicone
Steel
Associated component(s)
CRT
Panel, funnel, neck, frit
Funnel & neck glass, frit
Casing
Potting material in flyback
transformer
Base, right, left & back shields;
shadow mask
LCD
LCP panel
Backlight clear protector
Backlight light pipe
Power supply & rear cover
insulators
Base/stand weight & brackets,
backlight plates, rear cover metal
plate, power supply housing
a See Figures 2 and 3 for material percent contributions to total mass of monitor, excluding PWBs.
b Includes materials that could not be easily separated from the glass (e.g., frit, phosphors, transistors) and subtracts the
estimated lead content of the glass for the CRT.
c The mass of lead was estimated from the total mass of the different glass components and approximate lead levels in the CRT
glass components (MCC 1994). On average, approximately 10% of the total mass of CRT glass was assumed to be lead.
NOTE: Materials in bold are >5% of the monitor by weight.
total mass = 5. 15 kg
»^
Fig.
39%
V^
\ \
\
17%
5%
—2%
3%
4%
2. CRT product materials
decision rule
n
u
n
n
n
n
n
n
Glass (39%)
Steel (27%)
HIPS (17%)
Pb (4%)
Ferrite-magnet (3%)
Cu (2%)
Al (2%)
Silicone (1%)
Other (excluded)
meeting mass
47%
14%
14%
total mass = 12.8 kg
3%
Steel (47%)
PC (14%)
ABS(11%)
Polyester (9%)
Glass (1%)
Plexiglas (1%)
Al(1%)
Other (excluded)
Fig. 3. LCD product materials meeting mass
decision rule
D-6
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APPENDIX D
Table 2. Primary and ancillary materials or components meeting technology (T),
environment (Env), or energy (E) criteria
Materials
Associated components or process
CRT
LCD
Decision
criteria
CRT
LCD
Primary materials
Aluminum oxide (A12O3)
Aquadag
Beryllium (Be)
Bismuth oxide
Color filters (acryl epoxy resins)
Divinylbenzene resin
Frit (lead solder glass)
Indium-tin oxide (ITO)
Liquid crystals (e.g., polycyclic
aromatic halogenated
hydrocarbons, cyanobiphenyl,
phenylcyclohexane compounds)
Mercury
Nickel
Phosphors (e.g., ZnS, Y2O2)
Polyimide
TFT metals (e.g., Al, Cr, Mo, W)
TFT silicon materials (e.g., SiO2,
SiNx, doped Si)
Tungsten (W)
Electron gun wire heater
Faceplate black matrix
coating
Shadow mask back
coating
Glass solder joints
Electron gun cathodes
Illuminating material
Electron gun wire heater
Be-Cu metal clips
Front panel glass color
filters
Spacers in AMLCD cell
Electrode
Light-modulating material
Cold cathode fluorescent
tube in backlight
AMLCD cell alignment
layer
Transistor
Transistor
Transistor
Env
T
Env
Env, E
T, Env
T, Env
T, Env
Env
T
Env
T
T, Env
Env
T
T, Env
T
T, Env
Ancillary materials
Boron trichloride (BC13)
Carbon tetrafluoride (CF4)
Carbon trifluoride (CHF3)
Chloride (C12)
Ferric chloride (FeCl3)
Hydrochloric acid (HC1)
Isopropyl alcohol (IP A)
N-methyl pyrrolidone (NMP)
Polyvinyl alcohol
Qnlfiir li^YQflimriHf1 f^sp1 ^
Photolithographic etchant
(shadow mask)
Photolithographic
application of phosphors
Photolithographic etchant
Photolithographic etchant
Photolithographic etchant
Photolithographic etchant
Photolithographic etchant
Glass cleaner
Photolithographic
developer
PI-intnlitlinfrrQr^l-Mr* f^tnliQnt
Env
Env
Env
Env
Env
Env
Env
Env
Env
T^m/
D-7
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APPENDIX D
Table 2. Primary and ancillary materials or components meeting technology (T),
environment (Env), or energy (E) criteria
Materials
Tetramethyl ammonium
hydroxide (TMAH)
Associated components or process
CRT
LCD
Photolithographic
developer
Decision
criteria
CRT
LCD
Env
The materials identified for inclusion in the CDP (Tables 1 and 2) are then prioritized
based on the decision rule hierarchy triangle. Those materials that are either: (1) >5% by mass;
or (2) of environmental/energy concern, fit into the top priority of the upstream data collection
effort. Those materials that are either: (1) between 1-5% by mass; or (2) functionally important
and/or physically unique, fit into a lower priority of upstream data collection, but are still
included in the project. Those materials that are less than 1% by mass and do not meet the other
criteria listed above are excluded from the analysis. Currently, the materials falling into each
segment of the decision rule hierarchy are listed in Table 4.
Table 3. Materials excluded from analysis
Material
Associated component/application
CRT
LCD
Primary materials
Aluminized mylar
Brass
Foam rubber
Nylon
Paper
Polysulphone
Silicone rubber
Brass ring on neck assembly
Insulating rings on neck
assembly
Corner tape on backlight assembly
Brass threaded standoff in backlight assembly
Foam gasket in backlight assembly
Cable clamp, strain relief in backlight
assembly, clamp in backlight, bushing in
base/stand assembly
Caution label on rear plate assembly
Gaskets in LCD panel assembly, shock
cushion in light assembly, rubber feet in
base/stand assembly
Ancillary materials
Nitrocellulose
binder
Amyl acetate
O2
N2
Iodine
For frit application
For frit application
Metal etchant
Metal etchant
Polarizer coating
D-8
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APPENDIX D
For the top priority materials, we obtained upstream inventory data from secondary
sources where available. If no secondary sources were available, we attempted to collect primary
data or conduct further research from the literature. For materials in the middle tier, we
attempted to collect secondary data but gave less emphasis on including them if too many
resources were required. The top tier consists of materials greater than 5% by mass and all the
materials in Table 2. Each material in Table 2 was added to the list of materials for either
environmental or technological reasons and all except tungsten (W) were unique to a technology.
However, tungsten is also included in the top tier for potential environmental concern. As a
result, all the materials in Table 2 are of potential environmental concern and/or are both
functionally important and physically unique (see Figure 1).
Table 4. Summary table of preliminary CDP materials in priority hierarchy
Top tier
Middle tier
Lowest tier (excluded)
Steel, CRT glass, HIPS,
Polycarbonate, ABS, Polyester,
LCD glass, lead, A12O3,
Aquadag, Be, Bismuth oxide,
Acryl epoxy resins (color filters),
Divinylbenzene resin, Frit, ITO,
Liquid crystals, Hg, Ni,
Phosphors, Polyimide, TFT
metals, TFT silicon materials,
W, BC13, CF4, CHF3, C12, FeCl3,
HCI, IP A, NMP, Polyvinyl
alcohol, SF6, TMAH
Ferrite-magnet, Silicone,
Plexiglas, Al, Cu
Aluminized mylar, Brass, Foam
rubber, Nylon, Paper,
Polysulphone, Silicone rubber,
Nitrocellulose binder, Amyl
acetate, N2, O2, Iodine
3.2 Data Sources Evaluated
In order to identify upstream inventory data to be used for the CDP, nine different data
sources (databases or studies) were evaluated. The following nine were chosen based on UT's
experience in LCA, which included a comprehensive review of LCA databases (Menke et al.
1996), and from the scoping process for this project:
• American Plastics Council (APC)
The APC is a major trade association for the U.S. plastics industry. APC is comprised of
24 of the leading plastics manufacturers in the United States with many members having
a strong global market presence. APC's membership represents 80% of the U.S. resin
production capacity (APC 1999). APC has collected LCI data that are expected to be
released in 1999 for polyethylene (PE), polypropylene (PP), high impact polystyrene
(HIPS), polyethylene terephthalate (PET), and polyvinyl chloride (PVC) resins and
polyurethane precursors (Hentges 1999). Data are mostly vintage 1991 or 1993 and cover
production in North America (Hentges 1999). Additional inventories from APC have not
yet been identified, although they are presumed to exist.
D-9
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APPENDIX D
Association of Plastics Manufacturers in Europe (APME)
APME is an industry body that has published inventory data on olefins, polystyrene (PS),
PE, PP, PVC, PET and polymethanes (APME 1999), as well as ABS, Plexiglas,
polycarbonate, polyester, and polyimide (Karlsson 1999).
Bou |