Advanced Weighting Flashcards
Definition of Weighting:
„Weighting is the process of converting indicator results of different impact categories by using numerical factors based on value-choices. It may include aggregation of the weighted indicator results. “ (EN ISO 14044:2006)
Midpoint approach and weighting
If subjective weighting approach is applied, the below will lead to uncertainty and unreliability.
- The degree of knowledge of respondents
- Lack of transparency
- weighting of impact category results
Endpoint approach and weighting
Aggregation of the weighting targets by applying scientific modeling
- Decreasing number of targets for comparison
- More transparent
Weighting approaches
- Distance to target
- Panel weighting
- Monetary weighting
- Binary weighting
Distance to target
Impacts are weighted according to their proximity to a target. (e.g. EcoScarcity, EDIP)
Panel weighting
Impacts are weighted based
on the opinions of a group of people, and their preferences are translated directly into numeric values or ranges. (e.g. EI99/ReCiPe)
Monetary weighting
Impacts are weighted according to their estimated economic value. (e.g. Contingent valuation method: EPS, Conjoint analysis: LIME)
Binary weighting
Impacts are assigned either no weight or equal importance, based on criteria decided by the practitioner.
Distance-to-Target (DtT) weighting method:
Based on the principle that environmental impacts are weighted according to their distance from the current environmental situation to a previously defined target.
•Ecological Scarcity Method (ESM) is one tool for a Distance-to-Target (DtT) weighting
Ecological Scarcity Method (ESM)
–> Tool for a distance-to-target weighting
- Goal: Weighting of each substance/ resource use by the proximity or rather distance of current flows to political targets (critical flows) via so called eco-factors
- Originally developed for Switzerland and its specific environmental situation and legislation (Müller-Wenk 1978)
- Last Update: Frischknecht & Büsser Knöpfel 2013: Swiss Eco-Factors 2013 according to the Ecological Scarcity Method
- Adaptation to Germany: Ahbe et al. 2014: Ecological Scarcity Method for Germany.
- Parallel development: Ahbe et al. 2018. The Ecological Scarcity Method for the European Union.
Eco-Factor
Eco-Factor=CharacterizationNormalizationweighting*constant
with weighting=F/Fk=current flow/critical flow
Overview about developed weighting sets (DtT)
I. Baseline set:
–Includes binding and non-binding targets
–Temporal variation of target years
II. EU 2020 set:
- includes only binding and non-binding targets for the year 2020
- Extrapolation of targets to the year 2020, if 2020 as target year was not available
III. EU binding targets set:
- includes only binding targets, non-binding targets are excluded
- temporal variation of target years
II. EU 2020 set:
–Includes only binding and non-binding targets for the year 2020
–Extrapolation of targets to the year 2020, if 2020 as target year was not available
III. EU binding targets set:
–Includes only binding targets, non-binding targets are excluded
–Temporal variation of target years
ESM EU (Current study):
11 environmental issues (123 Eco-factors)
Case study: Application of weighting sets to environmental situation of the EU - I. Baseline
- Highest amount of aggregated EU-EP due to strictest targets
- Focus on “climate change” and “important air pollutants” (58 %)
Case study: Application of weighting sets to environmental situation of the EU - II. EU 2020
- Decreased importance of “climate change” and “air pollutants“ (29 %)
- For other categories marginal differences, but increasing relative share of absolute EU-EP
Case study: Application of weighting sets to environmental situation of the EU - III. Baseline
- Significant changes in relative shares due to the lack of non-binding targets (e.g. Water resources)
- Increased importance of air pollutants (59 %), decreased importance of climate change (8 %)
Results and discussion of ESM EU
•Occurred problems:
–Lack of data
–Incomplete data bases
–Geographical discrepancies
–Inconsistent target years for critical flows
•Exemplary application showed the differences of each set according to the assumptions
•Currently weighting factors are substance-specific
•Midpoint weighting factors for each impact category would be desirable (wünschenswert) –> but an incomplete list of substances and resource uses (still) prevents the implementation
Conclusions ESM
- The ESM could be transferred to the EU as a relevant weighting method for LCA practitioners
- Baseline set: Development of 123 eco-factors for 11 categories
- Case study showed the applicability of ESM as DtT weigthing method for EU
- Restrictions: Missing quantitative policy or data on current emission levels
- Outlook: Application of ESM possible anywhere in the world (existence of environmental policy) –> Future methodological development could aim at other countries or the application on a more global scale
Panel method
- Social agreement only by experts
- Panel method, questionnaire survey by experts
Contingent Valuation Method:
A questionnaire of willingness to pay for avoiding some kinds of change in the environment.
-> often tax is considered as proxy
LIME
•LIME (lifecycle impact assessment method based on endpoint modeling) developed in Japan 2000, updated 2012 and with latest update in 2018
•Weighting value should be widely acceptable (can get a social consensus)
–Not only experts, politicians, but general public
•All components of the environment should be considered when decision making of weighting on AoPs is performed.
Conjoint analysis
- A statistical technique, with surveys
- Used in market research to determine how people value different attributes (feature, function, benefits) that make up an individual product or service
- The objective of conjoint analysis is to determine what combination of a limited number of attributes is most influential on respondent choice or decision making
- A controlled set of potential products or services is shown to respondents and by analyzing how they make preferences between these products, the implicit valuation of the individual elements making up the product or service can be determined
- These implicit valuations can be used to create market models that estimate market share, revenue and even profitability of new designs
Conjoint analysis
Decision making in general situation is performed by considering the balance of several aspects related to the choice.
Equal weighting:
A binary weighting method where the practitioner assumes all impact categories have equal weight (weight equals one), Method unpublished but applied in practice
Footprinting:
A binary weighting method where the practitioner selects one or several impact categories (weight equals one) and disregards the other categories (weight equals zero)
