1. School of Civil and Building Services Engineering
Comparative Analysis of Life Cycle Inventory Techniques and Development of a Quantitative Uncertainty Analysis Procedure
Deidre Wolff
School of Civil and Building Services Engineering
Prof. Aidan Duffy
Prof. Geoff Hammond
Nov. 29, 2013

2. Life Cycle Assessment (LCA)
‘The compilation and evaluation of the inputs, outputs, and potential environmental impacts of a product system throughout its life cycle’ (ISO 14044, 2006)

3. Goal Definition and Scope
Life Cycle Assessment (LCA)
Four Stages:
Goal and Scope Definition
Life Cycle Inventory (LCI)
Life Cycle Impact Assessment (LCIA)
Interpretation
Goal Definition and Scope
Inventory Analysis
Interpretation
Impact Assessment
(ISO 14040)

4. Motivation
LCA is often used in decision-making processes and to inform policy
LCA involves using expert judgement, assumptions, data of poor quality, allocation and weighting
These all introduce uncertainty
Uncertainty is often ignored in LCA studies due to lack of knowledge and/or time and budget constraints

5. Objectives
Conduct Process, Input-Output, and Hybrid LCA of a simple system, quantifying overall uncertainty for each model
Compare the results obtained using different LCI methods
Develop a technique to make comparisons between studies that have applied different LCI methods
Apply methodology to a building, using a Bill of Quantities (BoQ) as a data source
Determine a suitable LCI and uncertainty analysis methodology to apply to all LCA studies in the built environment

6. What is uncertainty?
Errors originating from inaccurate measurements, lack of data, and model assumptions (Huijbregts, 1998) The problem of using information that is unavailable, wrong, unreliable, or that shows a certain degree of variability (Heijungs, 2004)

7. Uncertainty Classification in LCA
Parameter
data uncertainty
arises due to incomplete knowledge of true value of data, lack of data or measurement error
Model
unknown interactions between model formulations, due to simplification, derivation of characterization factors, aggregation of data into impact categories
Scenario
due to decisions made during the LCA, such as choice in system boundary, functional unit, allocation, weighting factors

8. LCA Overall Steps... Uncertainty Analysis Goal and Scope LCI LCIA
Interpretation
System Boundary
Data Collection
Identify Significant Issues
Choose Impact Categories
FU and
Reference Flow
Contribution/ Sensitivity Analysis
Scale Data to FU/ Ref Flow
Characterization Factors
Allocation Procedure
Weighting Methods
Uncertainty Analysis
LCI/LCIA Method
Assumptions

9. (Reap et al, 2008)

10. Case-study: Process LCA
Goal and Scope:
Determine the overall Global Warming Potential for the production of an electric kettle, using data from EcoInvent Database.
System boundary is cradle-to-gate, including raw material extraction and manufacturing of the materials used for the production of a kettle.
The system boundary is simplified, as the overall goal of the LCA is to quantify the uncertainty.

11. Case-study: Process LCA
Energy Input
Energy Input
Energy Input
Energy Input
Transport of Electric Kettle to Consumer
Raw Material Extraction
Transport to production facility
Assembly of Electric Kettle
Energy Input
Energy Input
Emissions to Air
Emissions to Air
Emissions to Air
Emissions to Air
Disposal/ Recycling
Use Phase
Emissions to Air
Emissions to Air

12. System Diagram Stainless Steel Silicone Kettle Copper Poly-propylene
The emissions associated with energy consumed during these steps has been ignored for simplification
Stainless Steel
437 g
Poly-propylene
245.5 g
Body of Kettle
682.9 g
Silicone
0.4 g
Assembly g
Kettle
Stainless Steel
15 g
Poly-propylene
310.2 g
355.6 g
Electrical Component
Copper
41.9 g
3.5 g
Polyamide

13. Process LCI and LCIA Results

14. Contribution Analysis

15. Contribution Analysis

16. Sensitive Parameters Sensitive Parameter
Contribution to Overall GWP (%)
Mean Value (kg CO2-eq per Kettle)
Raw EcoInvent Data
Emission
Kettle Part and Material
Mean (kg)
Minimum (kg)
Maximum (kg)
CO2 (Fossil)
Electrical, Polyprop.
15.9%
0.519
1.673
1.670
1.676
Body, Polyprop.
12.6%
0.410
Body, Stainless Steel
56.5%
1.842
4.212
3.673
4.865

17. Sensitivity Analysis

18. Next Steps… Quantify Uncertainty
Identify scenario and model uncertainty
Is it necessary to quantify scenario and model uncertainty in all cases?

19. Thank You! Any Questions?