Let’s suppose you want to know what is the best solution for the environment between two means of transports: a gasoline car and an electrical car …

• « environment » : it is about a comparison between two different transport means’ global environmental impacts (resources depletion, air emissions ,water emissions, waste generation)

• « best solution » : the objective is to take into account the whole impacts of two transport means: production, use and end of life

  
  

A fist consideration shows us that:

• air emissions of the gasoline car are mainly due to the gasoline combustion in the engine during its use stage

• air emissions of the electrical car are mainly due to the gasoline combustion fossils fuel used during the electricity production stage
  

• in order to define the best solution from an environmental point of view, it is notably necessary to compare the atmospheric emissions of the car use stage with the atmospheric emissions generated by the production of electricity necessary for the car to cover for instance 1 kilometre

This comparison is not obvious, and requires to make calculations, to use databases and to make assumptions

This work is standardised and has a name: this is the Life Cycle Assessment, according to the ISO 14040 series of standards. It is important to define the objectives and issues that lead to the need for the LCA method for each study we want to carry out.