# School of Civil and Building Services Engineering

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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

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)

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)

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 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

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... 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

(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.

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

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

Process LCI and LCIA Results

Contribution Analysis

Contribution Analysis

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

Sensitivity Analysis

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

Thank You! Any Questions?