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Chalmers University of Technology Attributional and consequential LCI modelling Tomas Ekvall Department of Energy Technology Chalmers University of Technology Gothenburg, Sweden email [email protected] InLCA/LCM 2003, Seattle, September 22-25 2003 Chalmers University of Technology The type of LCA affects modelling • Early proponents: Heintz & Baisnée (1992) Weidema (1993) • Well established: SETAC-Europe WG on Inventory Enhancement InLCA/LCM 2003, Seattle, September 22-25 2003 Chalmers University of Technology Types of LCA in this presentation (Curran et al. 2001) • Attributional LCA, which aims at describing the environmental properties of a life cycle and its subsystems. • Consequential LCA, which aims at describing the effects of changes within the life cycle. InLCA/LCM 2003, Seattle, September 22-25 2003 Chalmers University of Technology LCI modelling – Guide in summary • Attributional LCA: Include full life cycle Use average data Allocate in proportion to, e.g., economic value • Consequential LCA: Include processes that are affected Use data that reflect expected effects of changes Avoid allocation through system expansion InLCA/LCM 2003, Seattle, September 22-25 2003 Chalmers University of Technology Data that reflect changes (Azapagic & Clift 1999) Environmental burdens (B) Marginal change Substantial change Complete change Point of operation Production volume (Q) InLCA/LCM 2003, Seattle, September 22-25 2003 Chalmers University of Technology Allocation problem at multifunctional processes (Ekvall & Weidema 2003) Raw material Multifunctional process Product A (used in the life cycle investigated) Product B (used in other life cycles) InLCA/LCM 2003, Seattle, September 22-25 2003 Chalmers University of Technology System expansion when B depends on A Raw material Multifunctional process Product A Prod. of product C Market for function provided by product B Use of product B/C Waste management InLCA/LCM 2003, Seattle, September 22-25 2003 Chalmers University of Technology System expansion when A depends on B Multifunctional process (excluded from analysis) Waste management Prod. of Product D Product B Product A Market for alternative function provided by product A Market for function provided by product A in the life cycle investigated InLCA/LCM 2003, Seattle, September 22-25 2003 Prod. of Product C Chalmers University of Technology Additional consequences (Ekvall 2003) Consequences on… Example: Electricity efficiency Modelling tool …demand by other consumers Increased through price reduction Partial equilibrium models …economic activity Increased through money savings General equilibrium models …knowledge and values Reduced through good Marketing models? example InLCA/LCM 2003, Seattle, September 22-25 2003 Chalmers University of Technology Including affected processes Cradle Chain of cause Change or foreground system and effect Large uncertainty Unmanageable uncertainty Grave InLCA/LCM 2003, Seattle, September 22-25 2003 Chalmers University of Technology Limitations • Attributional LCA: Describes systems only Systems are subjective (allocation, geographical boundaries etc.) • Consequential LCA: Describes consequences only Entails great uncertainty and instability InLCA/LCM 2003, Seattle, September 22-25 2003 Chalmers University of Technology Suggested criteria for assessing methodology • Generate relevant information • Allow efficient communication of this information • Contribute to inspire actions • No significant adverse effects InLCA/LCM 2003, Seattle, September 22-25 2003 Chalmers University of Technology Conclusions and discussion • Consequential modelling goes far beyond marginal data and avoiding allocation • Pure consequential LCAs are rare • Terminology is confused • Ranking methodology is not straightforward • Choice of methodology should be deliberate InLCA/LCM 2003, Seattle, September 22-25 2003 Chalmers University of Technology References Azapagic A, Clift R. 1999. Allocation of environmental burdens in multiplefunction systems. J Cleaner Prod, Vol. 7, No. 2, pp. 101-119. Curran MA, Mann M, Norris G. 2001. Report on the International Workshop on Electricity Data for Life Cycle Inventories. Cincinnati, Ohio 45268 USA, October 23 – 25, 2001. Ekvall T. 2003. Tools for consequential modelling. Poster presented at 13th SETAC-Europe Annual Meeting in Hamburg, April 2003. Ekvall T, Weidema BP. 2003. System Boundaries and Input Data in Consequential Life Cycle Inventory Analysis. Submitted to Int J LCA. Heintz B, Baisnée P-F. 1992. System boundaries. In: Life cycle assessment. Workshop report, Leiden, The Netherlands, 2-3 December 1991. SETAC, Brussels, Belgium, pp. 35-52. Weidema BP. 1993. Development of a method for product life cycle assessment with special references to food products (summary). PhD thesis. Technical University of Denmark, Lyngby, Denmark. InLCA/LCM 2003, Seattle, September 22-25 2003