and oxidation of MSW; and the gasification of RDF. However, in
this case the pyrolysis–gasification of MSW and the gasification
of scrap tyres contribute the least to photochemical ozone
formation.
4.2. Normalization and weighting results
Many methods allow the impact category indicator results to
be compared by a reference, typically the regional amount of
pollutants associated with a particular impact category. In the
normalization of results, the impacts are each divided by the
selected reference values. A commonly used normalization value
is the total yearly environmental load in a country or continent.
For example, the total acidic pollutant (measured as year
per capita) is used to determine the normalized value for
acidification.