Life-cycle analysis - Evaluation of impacts

Life Cycle Assessment (LCA) is a comparative tool for the environmental evaluation of any system. There are four stages in the LCA process:

• defining objectives ;

• incoming and outgoing inventory ;

• assessment of potential impacts ;

• interpretation.

The first two stages are described in the Life Cycle Assessment (LCA) articles [G 5 500] and Life Cycle Assessment. Carrying out the inventory [G 5 510] . The third step is the subject of this article. Readers are therefore advised to familiarize themselves with the first two stages and the associated articles before reading what follows.

The aim of this article is to present, on the basis of current scientific knowledge, methods for assessing environmental impacts in the context of LCAs. Methods for assessing potential impacts in LCAs are traditionally carried out in three phases:

• impact classification: this phase consists firstly in selecting a relevant list of impact categories to be taken into account. Then, for each category, all the flows in the inventory are identified qualitatively;

• impact characterization: this involves defining the impact indicator that will quantify the specific contribution of each flow belonging to the impact class under consideration, calculating the contribution of each flow for each class, and aggregating the contributions calculated for the various flows within each class;

• global impact assessment: the aim of LCA is to compare the potential impacts of different systems. This comparison concerns :

  • or on the life cycle of different systems providing the same service; the aim is then to identify which system(s) is (are) the most environmentally friendly for all the impact classes studied;

  • or on the various stages in the life cycle of a given system: the aim here is to identify the strengths and weaknesses of a system over its entire life cycle and with regard to the impact classes studied....