An impact category dataset is a structured collection of Characterisation factors and/or Weighting factors with their accompanying documentation, all referring to the same impact category.
Within Life Cycle Impact Assessment, impact category datasets serve as the essential building blocks that enable practitioners to translate Life Cycle Inventory results into meaningful environmental impact indicators. Each dataset is focused on a single impact category, such as climate change, acidification, eutrophication, human toxicity, or resource depletion, ensuring consistency and coherence in the assessment approach.
The characterisation factors contained within an impact category dataset provide the mathematical relationships needed to convert different elementary exchanges (such as emissions of various greenhouse gases) into a common unit for the impact category indicator. For instance, a climate change impact category dataset would include characterisation factors expressing different greenhouse gas emissions in terms of carbon dioxide equivalents (CO₂-eq), derived from a characterisation model that describes their relative global warming potentials.
Some impact category datasets may also include weighting factors, which are based on value choices and describe the relative importance or contribution of different impact category endpoints. These weighting factors enable aggregation across different types of environmental concerns, though their use introduces normative elements into the assessment.
The documentation accompanying each impact category dataset is crucial for transparency and reproducibility. It typically describes the underlying characterisation model, the scientific basis for the factors, the geographical and temporal validity of the data, any limitations or uncertainties, and the methodological choices made in developing the dataset. This documentation enables LCA practitioners to make informed decisions about which impact category datasets are appropriate for their specific assessment context and allows for critical evaluation of the results.
Impact category datasets are often compiled into larger impact assessment method datasets, which provide a consistent set of impact categories with a unified methodological framework and rationale.
