United States
Environmental Protection
Agency
Risk Reduction
Engineering Laboratory
Cincinnati, OH 45268
Research and Development
EPA/600/SR-92/245 February 1993
EPA Project Summary
Life-Cycle Assessment:
Inventory Guidelines and
Principles
Battelle, and Franklin Associates, Ltd.
The U.S. Environmental Protection
Agency (EPA) is describing the pro-
cess, the underlying data, and the In-
herent assumptions Involved in con-
ducting the Inventory component of a
life-cycle assessment (LCA) In order to
facilitate understanding by potential
users. This Inventory consists of an
objective aggregation of the resource
usage and environmental releases as-
sociated with a product, production pro-
cess, package, or activity.
The report includes a brief discus-
sion of the history of LCAs, the basics
of the LCA methodology, the proce-
dural framework for conducting a life-
cycle Inventory, and descriptions of the
life-cycle stages.
This study was conducted in coop-
eration with the EPA Office of Air Qual-
ity Planning and Standards (OAQPS),
the Office of Solid Waste (OSW), and
the Office of Pollution Prevention and
Toxics (OPPT).
This project summary was developed
by EPA's Risk Reduction Engineering
Laboratory, Cincinnati, Ohio, to an-
nounce key findings of the research
project that Is fully documented In a
separate report of the same title (see
Project Report ordering Information at
back).
Introduction
As public concern has increased, both
government and industry have intensified
the development and application of meth-
ods to identify and reduce the adverse
environmental effects of the consumption
of manufactured products and marketed
services. These adverse effects occur at
all stages of the life cycle of a product.
LCA can be used as an objective tech-
nical tool to evaluate these environmental
consequences of a product, production
process, package or activity holistically,
across its entire life cycle.
A complete life-cycle assessment can
be viewed as consisting of three comple-
mentary components (1) the identification
and quantification of energy and resource
use and waste emissions (inventory analy-
sis); (2) the assessment of the conse-
quences those wastes have on the envi-
ronment (impact analysis); and (3) the
evaluation and implementation of oppor-
tunities to effect environmental improve-
ments (improvement analysis). The life-
cycle assessment procedure is not neces-
sarily a linear or stepwise process. Rather,
information from any of the three compo-
nents can complement information from
the other two. Environmental benefits can
be realized from each component of an
LCA independent of the completion of the
other components.
This report provides neutral, scientifi-
cally-oriented, consensus-based guidelines
on the conduct of the inventory compo-
nent of LCA.
Procedure
A properly conducted life-cycle inven-
tory analysis will provide a quantitative
catalog of energy and other resource re-
quirements, atmospheric emissions,
waterborne effluents, and solid wastes for
a specific product, process, or activity, as
well as identify and set boundaries among
the life-cycle stages (raw materials acqui-
Printed on Recycled Paper
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sition, manufacturing, use/reuse/mainte-
nance, and recycle/waste management).
To date, there has been no documenta-
tion which attempts to describe this proce-
dure in a manner that would facilitate un-
derstanding and use of the process and
lead to uniform application. The literature
contains little published information de-
scribing the technical basis for LCAs. In
an attempt to begin filling this information
gap, EPA contracted with Battelle and
Franklin Associates to document a proce-
dure for conducting a life-cycle inventory
analysis. This report of life-cycle inventory
guidelines and principles is the result of
that effort.
Results
Procedural Framework for Life-
Cycle Inventory
The inventory process begins with
clearly defining the purpose for conduct-
ing the inventory analysis and identifying
the boundaries which define the life-cycle
system. When the boundaries have been
determined, a system flow diagram can
be developed to pictorially describe the
system, as illustrated in Figure 1.
Once the purpose and boundaries have
been defined, a checklist (see Figure 2) is
a useful tool to cover most decision-mak-
ing areas in the performance of an inven-
tory. It includes geographic scope, types
of data used, how the data were gathered
and developed, how the data were mod-
eled, and how the results are presented.
A tool such as this one can help the
researcher clarify the issues, boundaries,
and conditions to be dealt with in a par-
ticular study. Worksheets can be used by
the analyst to collect and qualify data from
facilities. A checklist also can be used as
a communication tool.
A peer review, started early in the study,
should be conducted to address the valid-
ity of results, the methodology/scope, the
data/compilation, and the communication
of results. This review should include ex-
amination of how the boundaries were
defined and the quality level of the data
used before any statements regarding the
results of the analysis are published. Care-
ful interpretation is required in order to
avoid making unsupported statements.
Any limitations should also be communi-
cated to the public along with the results.
LCAs are data intensive and, therefore,
data quality can affect the outcome of an
analysis. Data collected for an inventory
should always be associated with a qual-
ity measure. Stand-alone data must be
developed for each subsystem to fit the
subsystems into a single system. Possible
sources of data are industrial data, gov-
ernment reports, papers and books in the
open literature, product specifications and
laboratory test data. The purpose, scope,
and boundary of the inventory help deter-
mine the level or type of information that
is required. Whenever possible, it is best
to get well-characterized industry data for
production processes. Manufacturing pro-
cesses often become more efficient or
change over time, so it is important to
seek current data. Inventory data can be
facility-specific or more general and still
remain current.
The next stage is the model construc-
tion, ft consists of incorporating the data
and material flows into a computational
framework typically using a computer
spreadsheet. The systems accounting data
that result from the computations of the
model give the total results for the energy
and resource use and environmental re-
leases from the overall system.
When writing the final report, it is impor-
tant to thoroughly describe the methodol-
ogy used in the analysis and explicitly
define the system analyzed and the bound-
aries that were set. All assumptions made
in performing the inventory should be
clearly explained. If the inventory was con-
ducted for purposes of product compari-
son, the basis for comparison among sys-
tems should be given, and any equivalent
usage ratios that were used should be
explained.
The results from the inventory can be
presented most comprehensively in tabu-
lar form. The choice of how the tables
should be created varies, based on the
purpose and scope of the study. Graphi-
cal presentation helps to augment tabular
data and can aid in interpretation.
How the results will be interpreted also
depends on the purpose for which the
analysis was performed. Careful interpre-
tation is required to avoid making unsup-
ported statements.
General Issues In Performing a
Life Cycle Inventory
There are several general issues which
are common to every stage of a life-cycle
inventory. These issues pertain to the type
of information these studies quantify and
the decisions or assumptions that must
be made in evaluating the information.
One major tool in life-cycle inventory analy-
sis is the template, which is a pictorial
Life-Cycle Stages
Inputs
Raw
Materials
Energy
^
^
Raw Materials Acquisition
\
t-
Manufacturing
1
r
Use/Reuse/Maintenance
\
Recycle/Waste Management
^;
^
^.
Outputs
Atmospheric
Emissions
Waterbome
Wastes
Solid
Wastes
Coproducts
Other
Releases
System Boundary
Figure 1. Defining system boundaries.
2
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Procedural Framework
LIFE-CYCLE INVENTORY CHECKLIST PART I—SCOPE AND PROCEDURES
INVENTORY OF:
Purpose of Inventory (check all that apply)
Private Sector Use
Internal Evaluation and Decision Making
l Comparison of Materials, Products, or Activities
l Resource Use and Release Comparison with Other
Manufacturer's Data
l Personnel Training for Product and Process Design
l Baseline Information for Full LCA
External Evaluation and Decision Making
l Provide Information on Resource Use and Releases
l Substantiate Statements of Reductions in Resource Use and
Releases
Public Sector Use
Evaluation and Policy-making
l Support Information for Policy and Regulatory Evaluation
l Information Gap Identification
l Help Evaluate Statements of Reductions in Resource Use and
Releases
Public Education
l Develop Support Materials for Public Education
l Assist in Curriculum Design
System* Analyzed
List the product/process systems analyzed in this inventory:
Key Assumptions (list and describe)
Define the Boundaries
For each system analyzed, define the boundaries by life-cycle stage, geographic scope, primary processes, and ancillary inputs included in
the system boundaries.
Postconsumer Solid Waste Management Options: Mark and describe the options analyzed for each system.
l Landfill l Open-loop Recycling
l Combustion l Closed-loop Recycling
l Composting l Other
Basis for Comparison
l This is not a comparative study. l This is a comparative study.
State basis for comparison between systems: (Example: 1000 units, 1,000 uses) _
If products or processes are not normally used on a one-to-one basis, state how equivalent function was established.
Computational Model Construction
l System calculations are made using computer spreadsheets that relate each system component to the total system.
l System calculations are made using another technique. Describe:
Describe how inputs to and outputs from postconsumer solid waste management are handled.
Quality Assurance (state specific activities and initials of reviewer)
Review performed on: l Data Gathering Techniques
l Coproduct Allocation
. l Input Data
l Model Calculations and Formulas
l Results and Reporting
Peer Review (state specific activities and initials of reviewer)
Review performed on: 1 Scope and Boundary
1 Data Gathering Techniques _
l Coproduct Allocation
l Input Data
l Model Calculations and Formulas
l Results and Reporting
Results Presentation
l Methodology is fully described.
l Individual pollutants are reported.
l Emissions are reported as aggregated totals only.
Explain why:
Report is sufficiently detailed for its defined purpose.
Report may need more detail for additional use beyond
defined purpose.
Sensitivity analyses are included in the report.
List:
Sensitivity analyses have been performed but are not included
in the report. List:
Figure 2. Sample life-cycle inventory checklist worksheet.
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Procedural Framework
LIFE-CYCLE INVENTORY CHECKLIST PART II-MODULE WORKSHEET
Inventory of: Preparer:
Life-Cycle Stage Description:
Date:
Quality Assurance AoDroval:
MODULE DESCRIPTION
Materials
Process
Other <•>
Energy
Process
Precombustion
Water Usage
Process
Fuel-related
Product
Coproducts <*>
Air Emissions
Process
Fuel-related
Water Effluents
Process
Fuel-related
Solid Waste
Process
Fuel-related
Capital Repl.
Transportation
Personnel
Data Value <*>
Type w
Data Age/Scope
Quality Measures (d)
MODULE INPUTS
MODULE OUTPUTS
(a) Include Units
(b) Indicate whether data are actual measurements, engineering estimates, or theoretical or published values and whether the numbers are from a specific manufacturer
or facility, or whether they represent industry-average values. List a specific source if pertinent, e.g.. 'obtained from Atlanta facility wastewater perrr* monitoring data-
(c) Indicate whether emissions are all available, regulated only, or selected. Designate data as to geographic specificity, e. g.. North America, and indicate the period.
(d) List measures of data quality available for the data Hem, e.g., accuracy, precision, representativeness, consistency-checked, other, or none.
(e) Include nontraditbnal inputs, e.g., land use. when appropriate and necessary.
(f) If coproduct allocation method was applied, indicate basis In quality measures column, e.g.. weight.
Figure 2. Continued
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guide that identifies the information that
must be obtained for every step involved
in an inventory analysis.
Major Concepts
Templates, or material and energy bal-
ance diagrams, are tools used to support
data gathering and development for life-
cycle inventory analyses.
Data for processes producing more than
one product are allocated based on the
relative weights of product output or an-
other justifiable method.
Data quality objectives are the required
performance specifications for information
in a life-cycle inventory. Establishment of
these specifications is determined by the
defined purpose of the life-cycle inven-
tory.
Data quality indicators are qualitative or
quantitative characteristics of data. These
include accuracy, bias, representativeness,
and other attributes that measure data
goodness and applicability.
Raw Materials and Energy
Acquisition
The life cycle of any product or material
begins with the acquisition of raw materi-
als and energy sources. For example,
crude oil and natural gas must be ex-
tracted from drilled wells, and coal and
uranium must be mined before these ma-
terials can be processed into usable fuels.
All of these activities fall into raw materi-
als acquisition.
Major Concepts
The resource requirements and envi-
ronmental emissions are calculated for all
of the processes involved in acquiring raw
materials and energy. This analysis in-
volves tracing the materials and energy
back to their sources.
Consequences of the raw materials ac-
quisition stage include non-traditional out-
puts, such as land use changes, and non-
chemical releases, such as odor or noise.
To the extent they are quantifiable, such
outputs may be incorporated.
When fuel sources become input mate-
rials for a manufacturing process, an en-
ergy factor accounts for the unused en-
ergy inherent in the fuel.
Materials Manufacture
Manufacturing is divided into three steps:
materials manufacture, product fabrication,
and filling/packaging/distribution. Materials
manufacture involves all manufacturing
processes required to process raw materi-
als into the intermediate materials from
which the finished product will be fabri-
cated. For example, this would include all
operations required to produce tallow and
sodium hydroxide from which bar soap is
made. Transportation between manufac-
turing steps and transportation to the point
of product fabrication is considered part of
material manufacture.
Major Concepts
Material manufacture converts raw ma-
terials into the intermediate products from
which the finished product will be fabri-
cated.
Material scrap from a subsystem can
be reused internally, sold as scrap, or
disposed of as solid waste. The inventory
account for each option is handled differ-
ently.
No credits or debits are applied to the
subsystem for internally recycled material
because no material crosses a subsystem
boundary.
Industrial scrap as a coproduct carries
with it the energy and wastes to produce
it. This ensures consistency with opera-
tions that use scrap inhouse.
Product Fabrication
This stage involves processing the
manufactured material to create a product
ready to be filled or packaged, for ex-
ample the production of fatty acids from
tallow, vacuum distillation, manufacture of
neat soap, and, finally, the cutting and
drying of the bar soap.
Major Concepts
Final product fabrication converts inter-
mediate materials into products ready for
their intended use by consumers.
Facilities for which data are reported on
a plant-wide basis will require allocation of
the inputs and outputs to the product of
interest.
Fllllng/Packaglng/Dlstrlbutlon
This stage includes all manufacturing
processes and transportation required be-
tween product fabrication and delivery of
the product to the customer. Thus, for bar
soap, this step includes all operations re-
quired to package the soap in wrappers,
place the packaged soap into corrugated
boxes, and transport the boxes to the
retailer and then to the consumer.
Major Concepts
Filling and packaging products ensures
that products remain intact until they are
ready for use, whereas distribution trans-
fers the products from the manufacturer to
the consumer.
In addition to primary packaging, some
products require secondary and tertiary
packaging, all of which should be ac-
counted for in a life-cycle inventory.
Any special circumstances in transpor-
tation, such as refrigeration used to keep
a product fresh, should be considered in
the inventory.
Use/Reuse/Maintenance
This stage is the one with which con-
sumers are most familiar; the actual use,
reuse and maintenance of the product.
This stage consists of a discrete set of
activities that begins after distribution of
finished products or materials to the con-
sumer and ends when these products or
materials are either recycled or discarded
into a waste management system.
Major Concepts
This stage includes all of the activities
undertaken by the user of the product or
service as well as any maintenance that
may be performed by the user or obtained
elsewhere.
Household operation, such as refrigera-
tion, are rarely associated with a single
product. Either the allocation of the capital
and operating energy and environmental
releases to a particular item are too small
to affect the results or they can be propor-
tionately included.
Recycle/Waste Management
Normally, after a product and its pack-
aging have been used by a consumer and
the product has fulfilled its intended pur-
pose, they are either recycled, composted,
or discarded as (post-consumer) waste.
Waste management includes incineration
and landfilling as well as wastewater treat-
ment.
Major Concepts
Recycle/waste management is the last
stage in a product's life-cycle.
In open-loop recycling, products are re-
cycled into new products that are eventu-
ally disposed.
In closed-loop recycling, products are
recycled again and again into the same
product.
Formulas are used to determine the
credits that should be assigned to recycled
products analyzed in a life-cycle inven-
tory.
This project summary was prepared by
the staff of Battelle, Columbus, Ohio
43201-2693.
The full report was submitted in fulfill-
ment of contract no. 68-CO-0003 by Bat-
telle under sponsorship of the U.S. Envi-
ronmental Protection Agency.
*U.S. Government Printing Office: 1993 — 750-071/60196
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Mary Ann Curran is the EPA Project Officer (see below).
The complete report, entitled "Life-Cycle Assessment: Inventory Guidelines and
Principles," (Order No. PB93-139681; Cost: $27.00, subject to change)
will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Risk Reduction Engineering Laboratory
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
United States
Environmental Protection Agency
Center for Environmental Research Information
Cincinnati, OH 45268
Official Business
Penalty for Private Use
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