Presentation on theme: "Comparative Analysis of Life Cycle Inventory Techniques and Development of a Quantitative Uncertainty Analysis Procedure Deidre Wolff School of Civil and."— Presentation transcript:
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
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)
7 Life Cycle Assessment (LCA) Four Stages: Goal and Scope Definition Life Cycle Inventory (LCI) Life Cycle Impact Assessment (LCIA) Interpretation (ISO 14040) Goal Definition and Scope Inventory Analysis Interpretation Impact Assessment
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
Objectives 1.Conduct Process, Input-Output, and Hybrid LCA of a simple system, quantifying overall uncertainty for each model 2.Compare the results obtained using different LCI methods 3.Develop a technique to make comparisons between studies that have applied different LCI methods 4.Apply methodology to a building, using a Bill of Quantities (BoQ) as a data source 5.Determine a suitable LCI and uncertainty analysis methodology to apply to all LCA studies in the built environment
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)
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
LCA Overall Steps... Goal and Scope LCILCIA Interpretation System Boundary Weighting Methods Characterization Factors Choose Impact Categories Uncertainty Analysis Contribution/ Sensitivity Analysis Identify Significant Issues FU and Reference Flow Allocation Procedure LCI/LCIA Method Assumptions Scale Data to FU/ Ref Flow Data Collection
(Reap et al, 2008)
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.
Raw Material Extraction Transport to production facility Assembly of Electric Kettle Energy Input Emissions to Air Transport of Electric Kettle to Consumer Energy Input Emissions to Air Energy Input Emissions to Air Disposal/ Recycling Use Phase Energy Input Emissions to Air Case-study: Process LCA
System Diagram Stainless Steel Poly- propylen e Silicone Poly- propylene Copper Polyamide Electrical Component Body of Kettle Stainless Steel Kettle Assembly 437 g 0.4 g g g g g 3.5 g 41.9 g g 15 g The emissions associated with energy consumed during these steps has been ignored for simplification
Process LCI and LCIA Results
Sensitive Parameters Sensitive Parameter Contribution to Overall GWP (%) Mean Value (kg CO 2 -eq per Kettle) Raw EcoInvent Data Emission Kettle Part and Material Mean (kg)Minimum (kg) Maximum (kg) CO 2 (Fossil) Electrical, Polyprop. 15.9% CO 2 (Fossil) Body, Polyprop. 12.6% CO 2 (Fossil) Body, Stainless Steel 56.5%
Next Steps… Quantify Uncertainty Identify scenario and model uncertainty Is it necessary to quantify scenario and model uncertainty in all cases?