1 systems analysis laboratory helsinki university of technology how to benefit from decision...

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Systems Analysis LaboratoryHelsinki University of Technology

How to Benefit from Decision Analysis in Environmental Life Cycle Assessment

Pauli Miettinen and Raimo P. Hämäläinen

Otakaari 1 M, FI-02150 Espoo

E-mail: [email protected]

http://www.hut.fi/Units/Systems.AnalysisEuropean Journal of Operational Research, Vol. 102, 1997, pp. 279-294.

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What is Environmental Product Life Cycle Assessment

• A tool to support environ-mental decision making

• Quantification of energy, material and waste flows over the product’s whole life cycle

• Evaluation of environmen-tal impacts of those flows

INVENTORYANALYSIS

IMPACT ASSESSMENT

IMPROVEMENT ASSESSMENT

GOAL DEFINITION

AND SCOPING

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LCA Organisations and Journals

• Organisations:– ISO - International Standardisation Organisation– SETAC - Society for Environmental Toxicology and

Chemistry

• Journals:– Chemosphere– Environmental Toxicology and Chemistry

International Journal of Life Cycle Assessment– Journal of Cleaner Production

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Goal Definition and Scoping

• Planning part of an LCA study– Purpose– Scope– Basis for comparison, i.e. the functional unit– Data collection and quality assurance plan

• Determines the following phases

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Inventory Analysis

• Quantification of inputs and outputs crossing the system boundary

• Problem areas:– Data amount and quality– Cut-off rules– Allocation

• Result is a long list of inputs and outputs of different nature– Difficult to interpret

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Product Life Cycle Assessment and System Boundaries

Energy productionand conversion

Raw-materialsacquisition

Manufacture Use

Recycling

Disposal

Incineration

Distribution

Re-use

Landfill

Ancillarymaterials

Natural environment

Product system

System boundary

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Impact Assessment

• Interpretation of the inventory results– Methods: Critical volumes, EPS, Eco-scarcity, Tellus,...– Environmental theme method: classification,

characterisation, (normalisation) and valuation

• How far to aggregate the inventory results?– One figure or contribution to a set of environmental

problems

• Objective and subjective information should be used separately

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Impact Categories

POTENTIAL ENVIRONMENTAL IMPACT

Ecological impactsAcidificationDepletion of stratospheric ozoneEcotoxicological impactsEutrophicationGlobal warmingHabitat alterations and impacts on biological diversityPhoto-oxidant formation

Human health impactsImpacts in work environmentToxicological impacts (excl. work environment)Non-toxicological impacts (excl. work environment)

Resource depletionEnergy and materialsLand (incl. wetlands)Water

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Improvement Assessment

• Systematic search for effective ways to reduce the total environmental load– Ensure that improvement in one part of the product’s life

cycle doesn’t lead to larger increase of impacts in the others

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Three Types of Data in LCA

• Process data for inventory analysis– Material and energy requirements as well as emissions

per unit output

• Impact data for transforming the inventory results to environmental impacts– Impacts of substances to different environmental

problems

• Preference data for planning the study and interpreting the results– Values and preferences of the actual decision makers– Overlooked in the current LCA practice

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Role of Decision Analysis in Life Cycle Assessment (LCA)

• Needed in the subjective steps:– Goal definition and scoping– Impact assessment (valuation)

• Helps planning the study to meet the needs of the decision makers

• Increases the transparency of public decision making

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Decision Analysis in Goal Definition and Scoping: Understanding the Process

• Who are the DMs?• What is the related decision or choice problem?• What are the alternatives?• What are the attributes, i.e. the impact

categories?• What data will be needed?

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LCA Study of Eight Finnish Beverage Packaging Systems (Virtanen et al. 1995)

• Objectives:– General: to produce environmental information for

political and economical decision making– Specific: To support in an environmental tax decision

concerning beverage in aluminium cans

• The study was unable to show the best alternative

• We analysed in retrospect:– How LCA information was used in decision making– What benefits might have come from the explicit use of

decision analysis

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Benefits from Value Tree Presentation and Explicit Prioritisation

• Seeing the decision problem in a general context– Include also other dimensions than environment

• Identification of the decision alternatives– Not the beverage packaging options but different tax

levels

• Identification of data collection needs– For example analysis of market shares resulting from

different tax levels should have been done

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Value Tree for Beverage Packaging

Packagingsystem

Economy

Consumer

Environment

Investments

Employment

Competition

Logistics

Price

Safety

Ease of use

Resource depletion

Ecological impacts

Human health impacts

Goal Main attributes Sub-attributes Alternatives

4 FIM / L

1 FIM / L

0 FIM / L

LCA

information

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Decision Analysis in Impact Assessment:Weighting the Impact Categories

• Impact weight should depend on:– General seriousness of the environmental impact– How alternatives differ in each impact category

• General weights suggested by the LCA community not acceptable– Address only part of the problem– Do not change if the decision problem, i.e. alternatives

change

• Weighting should be case specific• Behavioral problems exist in weighting

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A Compromise: Weights as a Function of the Impact Range

• Motivation: wi represents the importance of moving from the worst to the best outcome in the i th impact– Should never be interpreted without referring to some

specified change

• R and W are the reference range and weight– The reference weights elicited by considering the

reference ranges

• Weights explicitly as a function of the range, wi(ri)

– wi = Wi *ri /Ri, if the value function is linear

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Dynamic Weights in Case of Linear Value Function

1.0

0.0

v(Best)=1

v(Worst)=0

Value

Impac t

Actual range, r

Reference range, R

w = W*r / R

W corresponds to the range Rw corresponds to the range r

W

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Conclusions

• LCA a promising tool for environmental management, especially in public use

• Important application area for decision analysis• Goal definition and scoping: value tree

construction– Putting the decision problem into overall context– Understanding the components of the decision problem

• Impact assessment: weights must depend on the attribute ranges– Problem specific weighting– Explicit functional dependency

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