LCA is a method for analyzing a product's impact on the environment during the product's complete life cycle from raw material procurement through manufacture, distribution and usage to final disposal. Environmental friendly products should be selected based on LCA to meet green purchasing or green procurement standards.
LCA is an effective tool for comparing the environmental performance of similar products or services or of old and new versions of a product over the complete product life cycle. This assessment is especially effective in a case that a product may emit minimal CO2 at the production stage but may discharge considerable levels of CO2 while in use or when being disposed of. In practice, LCA evaluates energy and resource consumption, pollutant emissions to air, water, and soil, and waste emissions at each stage of a product's life cycle from raw material procurement, manufacture and processing, sale and usage to final disposal.
The ISO 14040 series provides an implementation guideline for LCA procedures. An example is the LCA evaluation of the average annual CO2 emission of a building. This evaluation measures the amount of energy and raw materials consumed by a building at all phases, including during construction, when transporting materials over distances, and by air conditioners and other equipment while the building is in use. The collected data is used to estimate energy consumption, CO2 emission levels, and waste burden, which is then combined to produce an overall evaluation of the building's impact on the environment. During a building's life cycle, CO2 emissions are generally high during the construction stage because of the raw material processing required for the steel, cement and other materials used in construction. Data collected during the LCA is also used as a basis for registration of Type III Environmental Declarations.