88
5 Life Cycle Assessment of Chemical Products and Processes
Fig. 5.15 Illustration of the mechanism for tropospheric photochemical ozone (O 3 ) creation from
a reaction of hydroxyl radicals with volatile organic carbons (VOCs, shown as RCH 3 ) and nitrogen
oxides (NO x ). hν denotes the energy of a photon of light of the frequency ν. h is the Planck
quantum of action (in J s)
and processes (Derwent et al., 2007) were used to define midpoint and endpoint
characterization factors describing impacts on human health from generated ozone
(RIVM, 2017).
5.5.4 Step 4: Optional Normalization, Grouping, and Weighting
Important conclusions can often be drawn just by looking at the results from
the midpoint or endpoint indicators as they are. However, the optional impact
assessment steps of normalization, grouping, and weighting can help to further
refine the LCA results and make them more comprehensible or easier to compare.
5.5.4.1 Normalization
Through normalization, the results of an impact at the midpoint or the endpoint
are calculated to be relative to a selected reference. Doing this can help to show
the relative magnitude of an impact in comparison to a total impact for a region or
population, show different impacts on a common scale, and help to check that the
calculated impacts are reasonable (and not the result of an error in the calculations).
Normalization is often carried out, for example, with reference to:
• Total impacts
• The population, e.g., to calculate impacts per person
5 Life Cycle Assessment of Chemical Products and Processes
Fig. 5.15 Illustration of the mechanism for tropospheric photochemical ozone (O 3 ) creation from
a reaction of hydroxyl radicals with volatile organic carbons (VOCs, shown as RCH 3 ) and nitrogen
oxides (NO x ). hν denotes the energy of a photon of light of the frequency ν. h is the Planck
quantum of action (in J s)
and processes (Derwent et al., 2007) were used to define midpoint and endpoint
characterization factors describing impacts on human health from generated ozone
(RIVM, 2017).
5.5.4 Step 4: Optional Normalization, Grouping, and Weighting
Important conclusions can often be drawn just by looking at the results from
the midpoint or endpoint indicators as they are. However, the optional impact
assessment steps of normalization, grouping, and weighting can help to further
refine the LCA results and make them more comprehensible or easier to compare.
5.5.4.1 Normalization
Through normalization, the results of an impact at the midpoint or the endpoint
are calculated to be relative to a selected reference. Doing this can help to show
the relative magnitude of an impact in comparison to a total impact for a region or
population, show different impacts on a common scale, and help to check that the
calculated impacts are reasonable (and not the result of an error in the calculations).
Normalization is often carried out, for example, with reference to:
• Total impacts
• The population, e.g., to calculate impacts per person