The Life Cycle Inventory (LCI) phase is a fundamental component of Life Cycle Assessment (LCA), focusing on collecting and quantifying data related to environmental inputs and outputs of a product. This phase sets the foundation for assessing the environmental impacts in the subsequent phases of LCA. This article covers the scope of the LCI phase, why it is important, how it fits into the broader context of LCA, and common challenges and best practices associated with it. This article covers the following questions:
What is the LCI phase?
What data is collected in the LCI phase?
How do inputs and outputs relate to modeling the product system?
What are the main challenges of the LCI phase?
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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
What is the LCI phase?
The Life Cycle Inventory (LCI) phase is the second phase of LCA (according to ISO 14040) and is often the most time-consuming phase. It involves creating a detailed inventory of all the necessary elements (i.e., inputs and outputs) for your product system, and thus, comes after the Goal & Scope phase because it is based on what it sets. Consider the inventory as a ‘shopping list’ of things you’ll need to accurately and holistically assess the environmental impact of your product system.
The LCI phase precurses the Life Cycle Impact Assessment (LCIA) phase, where the collected data is analyzed to determine the environmental impacts. A well-executed LCI ensures that the impact assessment is based on accurate and comprehensive data, leading to more reliable and meaningful results.
What data is collected in the LCI phase?
During the LCI phase, physical data is collected for all inputs and outputs related to your product’s life cycle. This includes but isn’t limited to, raw materials, energy, water, emissions to air, land, and water, and waste generation. Data can be sourced from documents such as electricity and water bills, supplier information, and environmental databases like ecoinvent.
Inputs and outputs
Inputs can include raw materials, different types of energy, water, or logistics
Outputs can include emissions to air, land, or water, and waste.
These inputs and outputs are part of the foreground system, which directly involves the processes and activities specific to your product. This data must be carefully collected and organized to ensure the LCA's accuracy.
Foreground and background data
Inputs and outputs in the LCI phase are categorized into foreground and background data.
Foreground data: Specific inputs and outputs directly related to the processes within the studied product's life cycle, such as raw materials and emissions specific to a particular production site. In Mobius, foreground data is considered Custom Impact data.
Background data: Generic data from environmental databases, such as ecoinvent, which provide impact information based on industry averages or scientific studies. Background data fills data gaps for processes not directly measured in the foreground system.
Together, foreground and background data provide a comprehensive picture of the product's environmental interactions.
Caution - Foreground vs background data: The difference between fore- and background data isn’t always as clear in practice. Foreground data doesn’t always measure environmental impact - it can measure mass, energy, or transport instead. In this case, the foreground data must be translated to environmental impact through background data. The following section expands on this.
How do inputs and outputs relate to modeling the product system?
Once the necessary input and output data is collected, the next step is to model the product system using an LCA software tool (e.g., Mobius or Helix). This involves creating a digital representation of your product's life cycle, incorporating all the processes and interactions identified in the initial part of the LCI phase.
Connecting and quantifying inputs and outputs
The inputs (e.g., raw materials, energy, water) and outputs (e.g., emissions, waste) are linked to environmental impact data in the LCA software tool. This process translates the foreground data into environmental impacts (Figure 1).
Figure 1: Translating physical data to environmental impact through primary data (Supplier LCAs) or secondary data (LCI Datasets).
This data can come from various sources:
Primary data: Specific information gathered from your suppliers or directly from your production processes.
Secondary data: Generalized information sourced from environmental databases, such as ecoinvent, which provide environmental impact based on industry averages or scientific data.
The model must be accurate and consistent - all of the units and methods in your data must match with those defined in the Goal & Scope phase of your LCA study. This might involve converting scientific notations to standard numbers, using particular units of measurement, or scaling data to fit your functional unit.
What are the main challenges of the LCI phase?
The following challenges should be carefully managed while conducting the LCI phase:
Iterative nature: The LCA process is iterative, meaning you may need to revisit and adjust your scope as new inputs and outputs are identified during data collection. For example, your data quality may be lower initially, but improve later as you’ve gained new insights. This also improves the accuracy of your LCA over time.
Data assumptions: Not all data may be readily available or perfectly accurate. Assumptions and approximations are often necessary. Documenting these assumptions is crucial for transparency and as a benchmark for potentially improving it at a later stage.
Pro tip - Assessing the quality of your model: At every stage of your LCA, it helps to consider the quality of the model using a traffic light system - green, amber, red. Mark anything you’re confident in with green. Give any items where you’re partially uncertain of an amber color. Code items you’re completely uncertain of red. This approach can also help when involving others (colleagues) in your LCA so it is clear where most work must be done. Such a transparent approach also streamlines the review or verification process.
Integration with background data: Linking your specific data to background data from environmental databases ensures a comprehensive assessment of environmental impacts.
Video tutorial
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Next steps
The Life Cycle Inventory (LCI) phase is a vital part of Life Cycle Assessment (LCA) that involves detailed data collection and quantification of all environmental inputs and outputs. This phase is foundational for assessing the environmental impacts in the next phase of LCA. For more detailed guidance on conducting LCAs, visit our additional resources and articles on our help center.