This is the first lesson on life cycle assessment in this module. In this
lesson, the framework for conducting life-cycle assessments is
described and examples of the ways in which life-cycle assessments
have been applied are provided. The second lesson provides a more
detailed overview of the inventory process in life-cycle assessment, and
the third lesson discusses potential methods for assessing the impacts
of a product life-cycle.
Why do life-cycle assessment?
• minimize the magnitude of pollution
• conserve non-renewable resources
• conserve ecological systems
• develop and utilize cleaner technologies
• maximize recycling of materials and
• apply the most appropriate pollution
prevention and/or abatement techniques
To begin the lessons, we ask the question: "Why do life-cycle
A great deal of waste is generated through human activities --
approximately 40 tons/year per person in the United States. This
represents lost resources as well as results in environmental
The most important goal of LCA, according to a survey of organizations
actively involved in LCA, is to minimize the magnitude of pollution (S.
Ryding, "International Experiences of Environmentally Sound Product
Development Based on Life Cycle Assessment," Swedish Waste
Research Council, AFR Report 36, Stockholm, May 1994.) This chart
lists some of the other goals: conserve non-renewable resources,
including energy; ensure that every effort is being made to conserve
ecological systems, especially in areas subject to a critical balance of
supplies; develop alternatives to maximize the recycling and reuse of
materials and waste; and apply the most appropriate pollution prevention
and/or abatement techniques;
How is life-cycle
• product development
• product improvement
• product comparison
Life cycle assessment has been applied in many ways in both the public
and private sectors. This is a list of some of the uses manufacturers
have for LCA. Product comparisons have received the most attention
from the press but according to the Swedish survey the most important
uses for manufacturers are 1) to identify processes, ingredients, and
systems that are major contributors to environmental impacts, 2) to
compare different options within a particular process with the objective
of minimizing environmental impacts, and 3) to provide guidance in
long-term strategic planning concerning trends in product design and
How is life-cycle
By public policymakers:
• environmental labeling
LCA is also used in the public sector. Some of the most visible of the
applications of life-cycle assessments are environmental or eco-labels.
Examples of ecolabels from around the world are shown here. Besides
environmental labeling programs, public sector uses of life-cycle
methodologies include use as a tool for making procurement decisions
and developing regulations. Policymakers report that the most important
uses of LCA are in 1) helping to develop long-term policy regarding
overall material use, resource conservation and reduction of
environmental impacts and risks posed by materials and processes
throughout the product life-cycle, 2) evaluating resource effects
associated with source reduction and alternative waste management
techniques, and 3) providing information to the public about the resource
characteristics of products or materials.
What is life-cycle assessment?
This is a simplified diagram of the inputs and outputs associated with
human activities. Opportunities for reducing waste outputs and energy
and raw material requirements in this system can be analyzed from
several perspectives. For example, studies of wastes and emissions at a
large scale can show the industries and regions where large volumes of
waste or highly toxic wastes are generated. In the field of industrial
ecology, the fate of materials as they move through processes and into
products and wastes are studied. Life-cycle assessment looks at this
system from the perspective of products.
In LCA, the processes required to make, use, and dispose of a product
are analyzed to determine the raw materials, energy requirements,
wastes, and emissions associated with the product's life cycle.
What is a “product life-cycle?”
This is a simplified diagram that shows the major stages of a product
life cycle. First, there is raw material acquisition. For the case of paper
products, raw material acquisition would include timber harvesting. For
plastic products, it would include crude oil extraction. After raw
material acquisition is the material manufacture stage. This is where
raw materials are processed into basic materials of product
manufacture. Felled trees are processed into lumber and paper, for
example. Crude oil is processed into polymers that can be made into
plastics. These materials move to the product manufacture stage
where they are made into products such as paper and plastic cups.
After this, they are used and disposed of or recycled.
Recycling can occur in several ways. A product might be reused,
which is what happens when a plastic cup is washed and reused
instead of being thrown away. It could be sent to product
remanufacture, where the materials it contains are used to make
another product. A paper cup, for example, might be shredded and
used for animal bedding. Finally, it might be recycled to materials
manufacture, where it is fed as a raw material for a process.
As shown in the diagram, all of these stages, along with the transport
required to move products and materials, can require raw materials
and energy and all of them can produce wastes and emissions.
Life-cycle stages include raw-material acquisition, production, use, and
disposal. LCA is a new and evolving concept, and definitions and
terminology as well as more fundamental practice aspects are still
developing. Students of life-cycle assessment will find that differences
exist among practitioners as they learn more about LCA.
3 Steps in LCA
1) life-cycle inventory
2) life-cycle impact
3) life-cycle improvement
There are three main steps in a life-cycle assessment:
1) Determine the emissions that occur and the raw
materials and energy that are used during the life-cycle of a product.
This is called a life-cycle inventory.
2) Assess what the impacts of these emissions
and raw material depletions are. This is called a life-cycle impact
3) Interpret the results of the impact assessment
in order to suggest improvements. When LCA is conducted to compare
products this step may consist of recommending the most
environmentally desirable product. This is called an improvement
Planning an LCA Project
• determine objectives
Why is LCA being conducted?
• define product under study and
What is its function?
What is an appropriate functional unit?
• choose system boundaries
What inputs and outputs will be studied?
How will data be collected?
Because of the open-ended nature of life-cycle assessments, the
planning phase of an LCA project is important. In the plan, the reasons
for conducting the LCA are stated. Also, the product to be studied and
its alternatives are defined. The functions of the system under
consideration must be defined and a functional unit chosen that
provides a basis for calculating inputs and outputs. The choice of
function unit can be ambiguous and is discussed in more detail later in
this lesson. Also in the planning phase, a choice of system boundaries
is made, defining the scope of the project. A strategy for data collection
is also determined and aggregation and evaluation methods are
The Functional Unit
especially critical in LCAs conducted
to compare products
Paper versus. plastic grocery sacks
function is to carry groceries so the
functional unit could be a defined
volume of groceries -- one plastic sack
does not hold the same volume of
groceries as a paper sack
The functional unit determines equivalence between systems.
Choosing a functional unit is not always straightforward and can have a
profound impact on the results of the study. For example, if paper and
plastic grocery sacks are to be compared in an LCA, the functional unit
would be a given volume of groceries. Because fewer groceries, in
general, are placed in plastic sacks than in paper sacks, the sacks
would not be compared on a 1 to 1 basis. Instead, two plastic sacks
might be determined as having the equivalent function of one paper
Functional Unit Ambiguity
Soft Drink Delivery Systems
number of functional units
Functional aluminum 16-oz. glass 2-liter
Unit cans bottles PET bottle
12-oz. of 1 1.25 5.33
one 1 1 1
As shown here, the functional unit of soft drink delivery systems (12-oz.
aluminum cans, 16-oz. glass bottles, or 2-liter polyethylene
terephthalate bottles), could be either a serving of soft drink consisting
of a given amount (e.g. 12 oz.) or a given container. These two choices
illustrate some of the difficulty in choosing a functional unit. Neither
choice of functional unit is entirely satisfactory. Twelve ounce cans and
16-oz bottles are generally consumed as a single serving and
comparing them on the basis of container count makes sense. It is only
rarely, however, that a 2-liter bottle of soft drink would be consumed as
a single serving.
Notice from this table how influential the choice of functional unit is. If
"one container" is chosen as the functional unit, values obtained for the
life-cycle inventory of 2-liter bottles will be over five times more per
functional unit than values obtained if a 12-oz serving is chosen as the
This example emphasizes that the results of LCA studies are heavily
dependent on the decisions made during the planning phase.
Uncertainty in Results of Life-
• assumptions made when choosing
system boundaries and data sources
• use of regional or global data
• poor quality data
• unavailable data
Ambiguity in the choice of functional unit is only one possible source of
error in conducting a life-cycle inventory. This is a list of some of the
major sources of uncertainties inherent in the results of life-cycle
inventories. It is important to understand the factors that affect the
accuracy of the data so that the results are not over-interpreted and so
that time and resources are not wasted in "fine-tuning" elements of the
inventory process when the overall results cannot be precisely obtained.
The inherent uncertainties in life-cycle inventory include the
assumptions and choices for system boundaries and data sources. For
example, if a life-cycle stage is excluded from the analysis because it is
incorrectly assumed to contribute insignificantly to the overall impacts,
the results of the inventory will be in error. Also, local conditions may
not have been adequately addressed in a study that used regional or
global data. Most importantly, available data on the processes being
inventoried may be of poor quality or not available.
• generally sponsored by a
stakeholder (e.g. plastics manufacturers
sponsor a study comparing paper and
• uncertainties and assumptions
inherent in life-cycle inventories leave
room for stakeholders in “losing”
product to criticize results
Perhaps the most widely publicized applications of LCA are those that
were completed for the purpose of comparing products. Examples of
assessments That received a great deal of press attention are one
conducted to compare cloth and disposable diapering systems, one
comparing plastic and paper cups, and one comparing polystyrene
clamshells and paper wrappings for sandwiches. Comparison
assessments are generally sponsored by an industry that has a vested
interest in the results, and because of the open-ended nature of LCA,
there is always room for criticism of the data. Because the results of
these LCAs have generated a great deal of controversy and debate,
these high-profile examples have created a great deal of skepticism
about the value of LCA and diverted attention away from some of the
other less controversial applications, such as LCAs conducted in order
to improve products.
LCA for Product Improvement
Average Gross Energy Required to
Produce 1 kg of Polyethylene
and Delivered Feedstock Total
Delivery Energy Energy Energy
Fuel Type (MJ) (MJ) (MJ) (MJ)
Electricity 5.31 2.58 0.00 7.89
Oil Fuels 0.53 2.05 32.76 35.34
Other 0.47 8.54 33.59 42.60
Totals 6.31 13.17 66.35 85.83
Feedstock energy is defined as the caloric value of materials that
are input into the processes required to produce polyethylene.
From “Ecoprofiles of the European Plastics Industry, Reports 1-4,”
PWMI, European Centre for Plastics in the Environment, Brussels,
LCAs conducted for product improvement can reveal processes,
components, ingredients, and systems to target for environmental
improvement. This was identified by product manufacturers as the
most important application of LCA, according to a Swedish survey
The results of an example of an LCA effort conducted for the purpose
of product improvement are shown in this table, which gives the results
of an inventory of the energy required to produce 1 kg of polyethylene.
The table shows that the majority of fuel required to make polyethylene
is in the organic matter that instead of being burned for energy is
converted to polyethylene. The values in the column titled "Feedstock
Energy" are about 3/4 of the total energy requirements. This inventory
showed that the focus of efforts to reduce the life-cycle energy
consumption of polyethylene are best spent on reducing the mass of
polyethylene in products -- to make them as light as possible.
LCA for Product Improvement
Polyester blouse life-cycle energy
Energy requirements of use stage could be
reduced by more than 90% by switching to
cold water wash and line dry instead of warm
water wash and drying in dryer.
(See Franklin Associates, Ltd., “Resource and
Environmental Profile Analysis of a
Manufactured Apparel Product,” Prairie
Village, KS, June 1993 for more details.)
The results of another example of an LCA conducted for product
improvement are shown here. This energy inventory of the life cycle of
a polyester blouse showed that the majority of energy consumption in
the life-cycle (82%) occurred during the product use life-cycle stage,
during washing and drying of the blouse. In this case, low-energy use
methods of washing and drying the blouse (cold water wash and line
dry) have the greatest potential for lowering the energy requirements of
a blouse's life cycle.
LCA for Product Improvement
Transportation vs. Manufacturing
Energy Consumption for a Garment
% of Life-Cycle Energy
Requirements for a Garment
Delivery Mode Transport Manufacture
Overnight Air 28% 72%
Truck 5% 95%
Truck + Rail 1% 99%
From Hopkins, Allen, and Brown, Pollution
Prevention Review, 4(4), 1994.
The results of a life-cycle inventory of the energy required to
manufacture a garment and deliver it to the customer are shown in this
table. This study showed that in the case where next-day air shipping is
used, the transportation and distribution life-cycle stages of a product
can be significant contributors to its energy requirements. When
customers were sent their orders by overnight air, transportation energy
requirements were 28% of total life-cycle energy requirements. This
finding is contrary to common knowledge: transportation and
distribution of products generally contribute negligibly to the energy
requirements of a product. Prior to this study, the garment
manufacturer was unaware that the delivery mode could contribute
significantly to the energy required over the life-cycle of their products.
LCA for Product Improvement
A final example of LCA used for product improvement is one where the
assessment was used to reveal which components are responsible for
the majority of raw material usage, wastes, emissions, and energy
consumption in a product manufactured from multiple components. In
a life-cycle assessment of a computer workstation, life-cycle inventory
data were compiled for diverse components such as semiconductors,
semiconductor packaging, printed wiring boards and computer
assemblies, and display monitors. The findings of the study showed
that the majority of energy usage over a workstation life cycle occurs
from operation of the display during the use stage of the life-cycle.
Therefore, to reduce the overall energy usage of a computer
workstation, efforts are best directed at the energy consumed by the
monitor. Semiconductor manufacture was found to dominate
hazardous waste generation and was also found to be a significant
source of raw material usage, even though, by weight, semiconductors
are a very small portion of a workstation.
Summary of Lesson 1
• LCAs are a tool for assessing and
minimizing the impact of human activities.
• Life-cycle stages of a product include raw
material acquisition, manufacturing, use,
• LCA techniques have been adopted in
industry and the public sector to serve a
variety of purposes.
• Choices made during the planning phase of
an LCA have a profound impact on the
results obtained. The choice of functional
unit, particularly when LCAs are
conducted to compare products, is
This concludes the first lesson on life-cycle assessment in this module.
You have been introduced to the concepts and goals of LCA. Remember
that a complete life-cycle assessment consists of three steps: 1) a life-
cycle inventory of the wastes and emissions, raw materials, and energy
requirements of a product over its life cycle, 2) an assessment of the
impacts caused the wastes and emissions, raw materials and energy
requirements of the product over its life cycle, and 3) an improvement
analysis where recommendations for reducing the impacts are
formulated. At this point, you should understand what factors to consider
in choosing a functional unit and also understand how crucial the system
boundaries of a life-cycle assessment are to the results. You should also
be aware of some of the ways in which this powerful tool has been put
into use by industry and by public policymakers.