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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