lca overview

7/17/2019 Lca Overview

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1

Life-Cycle Assessment

Lesson 1

Overview

This is the first lesson on life cycle assessment in this module. In this

lesson, the framework for conducting life-cycle assessments isdescribed and examples of the ways in which life-cycle assessmentshave been applied are provided. The second lesson provides a moredetailed overview of the inventory process in life-cycle assessment,and the third lesson discusses potential methods for assessing theimpacts of a product life-cycle.



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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

waste

• apply the most appropriate pollution

prevention and/or abatement techniques

To begin the lessons, we ask the question: "Why do life-cycle

assessment?"

A great deal of waste is generated through human activities --approximately 40 tons/year per person in the United States. Thisrepresents lost resources as well as results in environmentaldegradation.

The most important goal of LCA, according to a survey of organizationsactively involved in LCA, is to minimize the magnitude of pollution (S.Ryding, "International Experiences of Environmentally Sound ProductDevelopment Based on Life Cycle Assessment," Swedish WasteResearch Council, AFR Report 36, Stockholm, May 1994.) This chartlists some of the other goals: conserve non-renewable resources,including energy; ensure that every effort is being made to conserveecological systems, especially in areas subject to a critical balance ofsupplies; develop alternatives to maximize the recycling and reuse ofmaterials and waste; and apply the most appropriate pollution preventionand/or abatement techniques;



3

How is life-cycle

assessment used?

By manufacturers:

• 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 usesmanufacturers have for LCA. Product comparisons have received themost attention from the press but according to the Swedish survey themost important uses for manufacturers are 1) to identify processes,ingredients, and systems that are major contributors to environmentalimpacts, 2) to compare different options within a particular processwith the objective of minimizing environmental impacts, and 3) toprovide guidance in long-term strategic planning concerning trends inproduct design and materials.



4

How is life-cycle

assessment used?

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. Besidesenvironmental labeling programs, public sector uses of life-cyclemethodologies include use as a tool for making procurement decisionsand developing regulations. Policymakers report that the mostimportant uses of LCA are in 1) helping to develop long-term policyregarding overall material use, resource conservation and reduction ofenvironmental impacts and risks posed by materials and processesthroughout the product life-cycle, 2) evaluating resource effectsassociated with source reduction and alternative waste managementtechniques, and 3) providing information to the public about the resourcecharacteristics of products or materials.



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human

activities

What is life-cycle assessment?

energy

r a w

m a t e r i a l s

wastes and

emissions

p r o d u c t s

This is a simplified diagram of the inputs and outputs associated with

human activities. Opportunities for reducing waste outputs and energyand raw material requirements in this system can be analyzed fromseveral perspectives. For example, studies of wastes and emissions ata large scale can show the industries and regions where large volumesof waste or highly toxic wastes are generated. In the field of industrialecology, the fate of materials as they move through processes and intoproducts and wastes are studied. Life-cycle assessment looks at thissystem from the perspective of products.

In LCA, the processes required to make, use, and dispose of a productare analyzed to determine the raw materials, energy requirements,wastes, and emissions associated with the product's life cycle.



6

What is a “product life-cycle?”

disposal

use

product

manufacture

materialmanufacture

raw material

acquisition

p r o d u c t

r e u s e p

r o d u c t

r e m a n u f a c t u r e

m a t e r i a l s

r e c y c l e

energy

raw

materials

wastes

andemissions

t r a n s p o r t

This is a simplified diagram that shows the major stages of a productlife cycle. First, there is raw material acquisition. For the case ofpaper products, raw material acquisition would include timberharvesting. For plastic products, it would include crude oil extraction.

After raw material acquisition is the material manufacture stage. Thisis where raw materials are processed into basic materials of productmanufacture. Felled trees are processed into lumber and paper, forexample. Crude oil is processed into polymers that can be made intoplastics. These materials move to the product manufacture stagewhere 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 reusedinstead of being thrown away. It could be sent to productremanufacture, where the materials it contains are used to makeanother product. A paper cup, for example, might be shredded andused for animal bedding. Finally, it might be recycled to materialsmanufacture, where it is fed as a raw material for a process.

As shown in the diagram, all of these stages, along with the transportrequired to move products and materials, can require raw materialsand energy and all of them can produce wastes and emissions.

Life-cycle stages include raw-material acquisition, production, use, anddisposal. LCA is a new and evolving concept, and definitions andterminology as well as more fundamental practice aspects are stilldeveloping. Students of life-cycle assessment will find thatdifferences exist among practitioners as they learn more about LCA.



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3 Steps in LCA

1) life-cycle inventory

2) life-cycle impact

assessment

3) life-cycle improvement

analysis

There are three main steps in a life-cycle assessment:

1) Determine the emissions that occur and the rawmaterials 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 emissionsand raw material depletions are. This is called a life-cycle impactassessment.

3) Interpret the results of the impact assessmentin order to suggest improvements. When LCA is conducted tocompare products this step may consist of recommending the mostenvironmentally desirable product. This is called an improvementanalysis.



8

Planning an LCA Project

• determine objectivesWhy is LCA being conducted?

• define product under study and

its alternativesWhat is its function?

What is an appropriate functional unit?

• choose system boundariesWhat 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, thereasons for conducting the LCA are stated. Also, the product to bestudied and its alternatives are defined. The functions of the systemunder consideration must be defined and a functional unit chosen thatprovides a basis for calculating inputs and outputs. The choice offunction unit can be ambiguous and is discussed in more detail later inthis lesson. Also in the planning phase, a choice of system boundariesis made, defining the scope of the project. A strategy for datacollection is also determined and aggregation and evaluation methodsare chosen.



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The Functional Unit

especially critical in LCAs conductedto compare products

example:

Paper versus. plastic grocery sacks

function is to carry groceries so thefunctional 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 havea profound impact on the results of the study. For example, if paperand plastic grocery sacks are to be compared in an LCA, the functionalunit would be a given volume of groceries. Because fewer groceries,in general, are placed in plastic sacks than in paper sacks, the sackswould not be compared on a 1 to 1 basis. Instead, two plastic sacksmight be determined as having the equivalent function of one papersack.



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Functional Unit Ambiguity

number of functional units

Functional

Unit

12-oz.

aluminum

cans

16-oz. glass

bottles

2-liter

PET bottle

12-oz. of

soft drink

1 1.25 5.33

one

container

1 1 1

Soft Drink Delivery Systems

As shown here, the functional unit of soft drink delivery systems (12-

oz. aluminum cans, 16-oz. glass bottles, or 2-liter polyethyleneterephthalate bottles), could be either a serving of soft drink consistingof a given amount (e.g. 12 oz.) or a given container. These twochoices illustrate some of the difficulty in choosing a functional unit.Neither choice of functional unit is entirely satisfactory. Twelve ouncecans and 16-oz bottles are generally consumed as a single serving andcomparing them on the basis of container count makes sense. It isonly rarely, however, that a 2-liter bottle of soft drink would beconsumed 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 thelife-cycle inventory of 2-liter bottles will be over five times more perfunctional unit than values obtained if a 12-oz serving is chosen as thefunctional unit.

This example emphasizes that the results of LCA studies are heavilydependent on the decisions made during the planning phase.



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Uncertainty in Results of Life-

Cycle Inventories

• 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 themajor sources of uncertainties inherent in the results of life-cycleinventories. It is important to understand the factors that affect theaccuracy of the data so that the results are not over-interpreted and sothat time and resources are not wasted in "fine-tuning" elements of theinventory process when the overall results cannot be preciselyobtained.

The inherent uncertainties in life-cycle inventory include theassumptions and choices for system boundaries and data sources.For example, if a life-cycle stage is excluded from the analysisbecause it is incorrectly assumed to contribute insignificantly to theoverall impacts, the results of the inventory will be in error. Also, localconditions may not have been adequately addressed in a study thatused regional or global data. Most importantly, available data on theprocesses being inventoried may be of poor quality or not available.



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Product Comparisons

• generally sponsored by a

stakeholder (e.g. plastics manufacturers

sponsor a study comparing paper and

plastic products)

• uncertainties and assumptions

inherent in life-cycle inventories leaveroom 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 ofassessments That received a great deal of press attention are oneconducted to compare cloth and disposable diapering systems, onecomparing plastic and paper cups, and one comparing polystyreneclamshells and paper wrappings for sandwiches. Comparisonassessments are generally sponsored by an industry that has a vestedinterest in the results, and because of the open-ended nature of LCA,there is always room for criticism of the data. Because the results ofthese LCAs have generated a great deal of controversy and debate,these high-profile examples have created a great deal of skepticismabout the value of LCA and diverted attention away from some of theother less controversial applications, such as LCAs conducted in orderto improve products.



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LCA for Product Improvement

Fuel Type

Fuel

Production

and

Delivery

(MJ)

Delivered

Energy

(MJ)

Feedstock

Energy

(MJ)

Total

Energy

(MJ)

Electricity

Oil Fuels

Other

Totals

5.31

0.53

0.47

6.31

2.58

2.05

8.54

13.17

0.00

32.76

33.59

66.35

7.89

35.34

42.60

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,

May 1993.

Average Gross Energy Required toProduce 1 kg of Polyethylene

LCAs conducted for product improvement can reveal processes,

components, ingredients, and systems to target for environmentalimprovement. This was identified by product manufacturers as themost important application of LCA, according to a Swedish surveymentioned earlier.

The results of an example of an LCA effort conducted for the purposeof product improvement are shown in this table, which gives the resultsof an inventory of the energy required to produce 1 kg of polyethylene.The table shows that the majority of fuel required to make polyethyleneis in the organic matter that instead of being burned for energy isconverted to polyethylene. The values in the column titled "FeedstockEnergy" are about 3/4 of the total energy requirements. This inventoryshowed that the focus of efforts to reduce the life-cycle energyconsumption of polyethylene are best spent on reducing the mass ofpolyethylene in products -- to make them as light as possible.



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Polyester blouse life-cycle energy

requirements:Production: 18%

Use: 82%

Disposal: <1%

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 cycleof a polyester blouse showed that the majority of energy consumptionin the life-cycle (82%) occurred during the product use life-cycle stage,during washing and drying of the blouse. In this case, low-energy usemethods of washing and drying the blouse (cold water wash and linedry) have the greatest potential for lowering the energy requirementsof a blouse's life cycle.



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% of Life-Cycle Energy

Requirements for a Garment

Delivery Mode Transport Manufacture

Overnight Air

Truck

Truck + Rail

28%

5%

1%

72%

95%

99%

From Hopkins, Allen, and Brown, Pollution

Prevention Review, 4(4), 1994.

Transportation vs. ManufacturingEnergy Consumption for a Garment

The results of a life-cycle inventory of the energy required to

manufacture a garment and deliver it to the customer are shown in thistable. This study showed that in the case where next-day air shippingis used, the transportation and distribution life-cycle stages of aproduct can be significant contributors to its energy requirements.When customers were sent their orders by overnight air, transportationenergy requirements were 28% of total life-cycle energy requirements.This finding is contrary to common knowledge: transportation anddistribution of products generally contribute negligibly to the energyrequirements of a product. Prior to this study, the garmentmanufacturer was unaware that the delivery mode could contributesignificantly to the energy required over the life-cycle of their products.



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A final example of LCA used for product improvement is one where

the assessment was used to reveal which components are responsiblefor the majority of raw material usage, wastes, emissions, and energyconsumption in a product manufactured from multiple components. Ina life-cycle assessment of a computer workstation, life-cycle inventorydata were compiled for diverse components such as semiconductors,semiconductor packaging, printed wiring boards and computerassemblies, and display monitors. The findings of the study showedthat the majority of energy usage over a workstation life cycle occursfrom operation of the display during the use stage of the life-cycle.Therefore, to reduce the overall energy usage of a computerworkstation, efforts are best directed at the energy consumed by themonitor. Semiconductor manufacture was found to dominatehazardous waste generation and was also found to be a significantsource of raw material usage, even though, by weight, semiconductorsare a very small portion of a workstation.



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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,

and disposal.

• 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

especially influential.

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 threesteps: 1) a life-cycle inventory of the wastes and emissions, rawmaterials, and energy requirements of a product over its life cycle, 2) anassessment of the impacts caused the wastes and emissions, rawmaterials and energy requirements of the product over its life cycle, and3) an improvement analysis where recommendations for reducing theimpacts are formulated. At this point, you should understand whatfactors to consider in choosing a functional unit and also understand howcrucial the system boundaries of a life-cycle assessment are to theresults. You should also be aware of some of the ways in which thispowerful tool has been put into use by industry and by publicpolicymakers.

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