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The impact categories are ordered based on characterization factors. Characterization factors are numbers that indicate how much a specific substance (e.g. 1 kg of CO2) contributes to an environmental effect (e.g. climate change). Since more greenhouse gasses contribute to climate change, the mutual relationship between these substances can has to be determined on the basis of characterization factors. After characterization, an environmental analysis provides a score on various environmental themes such as climate change, acidification, eutrophication, etc. In order to reduce bring down the scores on these themes to one number one can use weightingweighing. Weighting Weighing reflects the relative importance of the environmental themes . The weighting process and is based on shadow price method. The shadow price is the highest cost level acceptable for governments (prevention costs) per unit of emission control.
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