August 31, 2011

Performing the interpretation in the LCA

By Ann-Christin Pålsson

Interpretation is an important activity in the LCA. The aim of the interpretation phase is to reach conclusions and recommendations in accordance with the defined goal and scope of the study. Results from the inventory (LCI) and environmental impact assessment (LCIA) are combined and reported to provide a complete and unbiased account of the study.

Note that the interpretation is made iteratively with the other phases, i.e. interpretation is an integral part of the work in the LCA where each intermediate result from the different phases of the study is interpreted.

The life cycle interpretation of an LCA comprises three main elements according to ISO 14040:

  • Identification of the significant issues based on the results of the LCI and LCIA phases of LCA.
  • Evaluation of results, including completeness, sensitivity and consistency checks. Also, results from uncertainty analysis and data quality analysis are considered
  • Conclusions, limitations and recommendations.

In practice, each result from the different parts of the study is interpreted separately:

  • Inventory
    • Data used for included unit processes
    • System boundaries; decisions regarding inclusions and exclusions of processes, consequences of cut-offs etc.
    • Inventory results; e.g. which parts of the product system have a large contribution to the overall result, and where can improvement potentials be identified.
  • Impact assessment
    • Classification and characterization; for example which flows and parts in the system have a large contribution to the impact assessment result for the selected impact categories
    • Weighting (when included); for example which impact categories has a large contribution to the weighting result, and which flows and processes contributes to these categories.

Thus, significant issues are identified for each intermediate result in the study. Evaluations are performed with regard to completeness, sensitivity and consistency for each result separately, and are then combined into an overall evaluation for the full study.