3.7.3 Complementary material: The details of performing an LCA

Course subject(s) Module 3. Analysis

If you are curious about how to perform an LCA, you will find some valuable information in the following complementary text.

How to perform an LCA?

The ISO standard 14040:2006 describes the principles and framework for LCA. The standard includes the definition of the goal and scope of the LCA, the life cycle inventory analysis (LCI) phase, the life cycle impact assessment (LCIA) phase, and the life cycle interpretation phase, among other methodological aspects (see figure 1)

Figure 1: Life Cycle Assessment Framework. Source. ISO (2006)

Life cycle assessment framework: (1) Goal and scope definition, (2) Inventory analysis, (3) Impact assessment, (4) Interpretation

In the goal and scope phase, the aim of the study is defined, and the related questions are framed. Questions such as “What isthe intended application of the results?” are answered here. The function of the systems assessed is defined here.

LCA studies typically conduct comparisons based on functionality. For example, alternative cars are compared based on the delivery of 1 km of driving over a specific period of time. This unit of comparison is called a functional unit, and it is a quantitative description of the function fulfilled by the system under assessment.

The system boundaries are also set during this phase of the LCA study. Given the complexity of the input/output interactions that one can identify across the entirelife cycle of product systems, choices need to be made and some parts of the system will need to be cut-off from the analysis.

In the life cycle inventory phase, the product system is modeled as a collection of related activities and operations –defined as unit processes –that deliver the functional unit. Unit processes can be specific manufacturing steps or related activities like maintenance, cleaning, waste treatment or disposal.

All of above allows the system to perform its function, and all unit processes need to be scaled to the functional unit. Product systems can involve thousands of unit processes. Existing inventory databases are used for commonly used upstream processes (e.g. electricity generation, copper mining), while direct data collection is needed for other more relevant processes in the foreground.

Once the inventory system is populated with data, the magnitude and significance of the potential environmental impacts of the systems under assessment can be evaluated during the life cycle impact assessment phase. Impact scores are calculated using existing models that draw on the best available methods and scientific consensus to estimate transport, fate, effect, and potential damages of the inventory emissions. Standard LCA software will automatically connect the inventory data to the right factors for the characterization of emissions. Impact scores are then calculated across various impact categories, includingglobal warming, toxicity, and acidification, among many others.

Finally, the last phase corresponds to the interpretation of the results. LCA studies rely on extensive data to represent very complex economic systems. Data are not always accurate or available, and assumptions about average conditions across vastgeographical regions are required. Additional analyses are required to interpret the results, to assess the importance of assumptions, to study emissions across the life cycle, and assess the uncertainty of the data used. All of these very important aspects are part of the interpretation phase of LCA.

For detailed documents regarding the implementation of an LCA, please refer to:



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