The Life Cycle Impact Assessment (LCIA) phase is where the environmental footprint of products becomes more tangible. As the third phase in the Life Cycle Assessment (LCA) process, LCIA takes the raw data collected during the Life Cycle Inventory (LCI) phase and translates it into quantifiable environmental impact scores. This article covers the following questions:
What is the LCIA phase?
How does LCIA translate physical data into environmental data?
What is the role of LCIA methods?
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Feel like you're missing information? This article builds upon the following articles, check them out if you want to learn more:
On ISO 14040/44: Explained: LCA standards
On Goal & Scope phase: Explained: Goal & Scope phase
On Life Cycle Inventory phase: Explained: Life Cycle Inventory (LCI) phase
On impact categories: Explained: Environmental impact categories
What is the LCIA phase?
Life Cycle Impact Assessment (LCIA) is the third phase of LCA according to ISO 14040. It is where you begin to uncover the environmental impact of your product. After gathering data on the various inputs (like raw materials and energy) and outputs (such as emissions and waste) during the LCI phase, LCIA translates this raw, primary data into meaningful environmental impact scores. Put differently, the process of Life Cycle Impact Assessment converts a product’s interactions with the environment into quantifiable impacts, allowing you to understand the broader environmental consequences of a product’s life cycle.
How does LCIA translate physical data to environmental data?
In the previous section, we briefly described what happens in the LCIA phase - raw primary data is translated into environmental data and insights (Figure 1). But, what happens when primary data is converted to environmental data? For that, read about elementary flows, impact categories & characterization factors below.
Figure 1: Depiction of the LCIA phase which converts data input (left) into impact scores in environmental impact categories (right).
What is the connection between elementary flows and impact categories?
Understanding the connection between elementary flows and impact categories is crucial for translating raw data into meaningful environmental insights during the LCIA phase.
Elementary flows: These are the direct exchanges between your product system and the environment. These exchanges can go in both directions - such as the extraction of raw materials (like timber; from the environment to your product system) or the emission of pollutants (like CO₂, from the product system to the environment). Each elementary flow represents a specific environmental interaction, whether it's drawing resources from nature or releasing substances into it.
Note - Elementary flows: Luckily, most of the time you don’t model or work with elementary flows directly. LCI databases (e.g., ecoinvent) identify relevant elementary flows and bundle them together into ‘digestible’ datasets that include all relevant interactions between a specific system and the environment.
Impact categories: Once the product system is defined, the next step is to categorize the elementary flows into impact categories (*done via LCIA methods and our LCA software). Impact categories represent broader environmental concerns, such as climate change, water use, or ozone depletion. For instance, all emissions that contribute to global warming—such as CO₂, methane (CH₄), and nitrous oxide (N₂O)—are characterized, and then grouped under the "climate change" impact category. By aggregating these related flows, you can understand the overall contribution of your product to a specific environmental issue in a simplified, quantifiable way via impact scores.
What is characterization and how does it turn elementary flows into impact scores?
Characterization is the process in LCIA that transforms the effects of different elementary flows into a common unit within each impact category, making the environmental impacts easier to compare and understand.
Characterization factors: Each impact category uses characterization factors to standardize the effects of different substances. For example, within the "climate change" category, different greenhouse gases have varying levels of impact on global warming. Methane (CH₄), for instance, has a global warming potential (GWP) 34 times greater than carbon dioxide (CO₂). Therefore, 1 kg of methane emissions is equated to 34 kg of CO₂ equivalent (CO₂-eq) in this category. Similarly, many chemicals are toxic to human health - but not all chemicals are equally dangerous. Characterization factors ‘standardize’ these relative effects, to get to one total grouped impact.
Note - Differing characterization factors: Characterization factors can differ between LCIA methods (e.g. EN15804+A2 vs Environmental Footprint Method). They can differ in two ways:
Slightly different estimates of how specific molecules affect an environmental impact category (difference in actual characterization factors).
Different LCIA methods might use different units for the impact categories, which results in differing characterization factors. Read more about this here.
Impact scores: By applying characterization factors, LCIA converts raw LCI data into comparable impact scores, providing a clear picture of your product's environmental footprint across various categories.
This process, from identifying elementary flows, categorizing them into impact categories, and applying characterization factors, is how LCIA transforms complex environmental data into actionable insights.
What is the role of LCIA methods?
Before initiating the LCIA process and calculating the environmental impact of a product, an LCIA method must be selected. An LCIA method is a predefined set of impact categories and characterization models that determine how the environmental impacts are calculated. These methods differ based on the distinct impact categories they include, how they calculate these impacts, and how they classify (characterize) elementary flows. Choosing the right method often depends on the LCA standard applicable to your product or industry. Read the following article for more details on LCIA methods.
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Next steps
Life Cycle Impact Assessment (LCIA) is a critical phase in LCA that translates your product's environmental interactions into understandable impact scores. By categorizing and quantifying these impacts, LCIA provides the insights needed to assess and improve the environmental performance of your product. Understanding this phase is essential for anyone involved in LCA, as it helps bridge the gap between raw environmental data and actionable insights