A normalisation reference is the amount of an Impact category indicator for a specific Activity or group of activities that serves as a baseline for comparison in Life Cycle Assessment. This reference value is typically calculated as the aggregated per capita production or consumption for a defined geographical area over a specified time period, usually one year.
The purpose of a normalisation reference is to provide context and scale to Life cycle impact assessment result values. By comparing an LCIA result to a normalisation reference, practitioners can express environmental impacts in relative terms rather than absolute units, making it easier to understand the significance of results. For example, a carbon footprint might be expressed as "equivalent to 0.01% of the annual per capita greenhouse gas emissions in the European Union".
Normalisation references are constructed by aggregating impact category indicator amounts across all relevant activities within a geographical boundary, such as a country, region, or the entire world. The total impact is then divided by the population to obtain a per capita reference value. This approach allows for meaningful comparisons between product systems and provides insight into the relative contribution of a specific product or service to the total environmental burden of society.
Common geographical scopes for normalisation references include individual countries, regions such as Europe, or global averages. The choice of normalisation reference can significantly influence the interpretation of results, as different geographical areas may have varying levels of production, consumption patterns, and environmental pressures. Therefore, it is important to select a normalisation reference that is appropriate to the decision context and clearly communicate which reference has been used when presenting normalised results.
