Principles for Life Cycle Assessment
Life cycle assessment according to ISO 14040 is based on the following main principles:
Life cycle perspective
The assessment should encompass the full life cycle; from extraction of resources, through all manufacturing and processes steps, to use and end of life, including transportation and energy generation.
The assessment should include all relevant environmental impacts associated with the production of the product. Examples of relevant environmental impact to include are impacts on global warming and eco-systems, human health, depletion of non-renewable resources, etc. Note that different specific environmental impacts may be relevant for different products, depending on the nature of the processes needed to produce the product.
Relative approach and functional unit
The assessment should be related to the function delivered by the product system. The function is in LCA quantified by the functional unit, i.e. a numerical measure to which all inputs and outputs is related. For example, the function of paint is protection of a surface, and for this system the functional unit could be defined as “keeping 5 m2 of wall protected for 10 years”.
When performing the assessment, it may be necessary to go back and change expectations and prerequisites for the study, based on experiences and information that is collected underway. This is an important part of the work; to look back and check the purpose with the study and if the questions of the study has been answered. For example, aspects that were not known in the beginning might have come up during the study, or maybe certain data was simply not possible to obtain.
The choices made when performing the assessment should be documented and presented in sufficient detail, to facilitate the understanding of the results and limitations.
The assessment should include a sufficient part of the life cycle and environmental impacts. This is important to ensure that the result represents a meaningful picture of the total environmental impact throughout the product life cycle, and that no part that may be important in the study is left out.
Priority of scientific approach
When performing a life cycle assessment there are a number of decisions to be taken. For instance what to include in the assessment, how to collect data, and how to perform the environmental impact assessment. In this work one should always strive to, as far as possible, use a scientific approach to ensure that the work is reproducible and transparent. This in turn means that the work should be documented to allow for an independent review of the LCA.