Primary data is data collected directly from specific activities, processes, or facilities that are actually part of the product system being studied. This data is obtained through direct measurement, calculation, or estimation from the actual sources within the system boundary, making it site-specific and representative of the particular conditions under investigation.
In the context of Life Cycle Assessment, ISO 14044 clause 4.3.3.2 distinguishes between data obtained directly from production sites or other activities in the supply chain (primary data) and data from other sources such as databases or literature (secondary data). Primary data represents the most accurate and specific information about the environmental performance of a particular activity, as it reflects actual operating conditions, technologies, and practices at the specific location and time period being assessed.
Primary data collection typically involves gathering information through site visits, surveys, questionnaires, interviews with operators, direct measurements of inputs and outputs, or extraction from facility records and monitoring systems. This may include data on raw material consumption, energy use, emissions to air and water, waste generation, and other relevant exchanges between the activity and its environment. The specificity and accuracy of primary data make it particularly valuable for identifying improvement opportunities and for supporting robust decision-making.
The quality and representativeness of an LCA study are significantly enhanced when primary data is used for activities that contribute substantially to the overall environmental impacts, particularly for foreground processes where the practitioner has direct access to information. Whilst collecting primary data can be resource-intensive, requiring time and effort to gather, validate, and document, it provides the foundation for credible and actionable LCA results that truly reflect the system being analysed.
In practice, most LCA studies combine primary data for key foreground processes with secondary data for background processes where primary data collection would be impractical or where generic data provides sufficient accuracy for the study's intended purposes.
