Comparative Analysis of Life Cycle Assessment Methodologies in the Built Environment

Life Cycle Assessment (LCA) is a technique that can be used to assess the potential environmental impacts of a product or system over its life cycle. It consists of four stages: Goal and Scope Definition, Life Cycle Inventory (LCI), Life Cycle Impact Assessment (LCIA) and Life Cycle Interpretation. LCA is an important tool in determining the overall environmental impact of a product/system, and can also be used to indicate which parts of the life cycle are contributing most.

LCI is a significant step in the LCA process, as it involves the collection of data, and how to combine the data from all parts of the Life Cycle into an overall emission, energy, or monetary value.  There are currently three main methodologies used to calculate the LCI, being Process, Input-Output and Hybrid techniques.  Process analysis involves the compilation of raw materials, energy and emissions data for each stage in the life cycle of the product/system.  Truncation error can lead to high uncertainty in the results of the LCA for this method.  In Input-Output analysis, the economy is broken down into N sectors, using national average data in these sectors to calculate the emissions and energy values for the Life Cycle being looked at.  Since Input-Output tables combine data from products/industries into sectors, using this method may also lead to high uncertainty in the LCA results.  Finally, the hybrid techniques include Process-based analysis, Input-Output-based analysis, Tiered analysis, and Integrated analysis.  These techniques aim to combine Process and Input-Output data in a way to reduce their limitations, and improve the overall uncertainty of the LCA results.

LCA of buildings and constructions is important as the built environment has a large environmental impact, contributing approximately 40-50% of GHG emissions and consuming 30-40% of the world’s primary energy supply.  It is thus necessary to examine the environmental impact over the entire life cycle of buildings and constructions in order to take measures to reduce this impact.  There have been many LCA studies done in the field, however due to the variation in use of the LCI methods across studies, it is difficult, if not impossible, to make comparisons between them.  This research thus intends to address the question of which methodology can be considered state-of-the-art in the built environment and be applied as a standard method for all LCAs conducted in the industry?

The main objectives of this research are thus:

• To assess existing LCI methodologies by identifying their strengths and weaknesses
• To carry out an LCA case-study in the built environment, using each LCI methodology for the same case-study.  The results of each LCA can then be compared by assessing the data quality and availability, uncertainty and sensitivity, compliance with the International Standard (ISO 14044), limitations, assumptions, system boundary completeness, and ease of application (in terms of cost and time) of each methodology for the same case-study.
• To determine a suitable LCI methodology that can be applied as a uniform method to the built environment

Personnel

DIT - School of Civil & Building Services Engineering

Deidre Wolff

Dr Aidan Duffy

Collaboration:

University of Bath - Prof Geoff Hammond