The following calculations demonstrate how characterization factors can be used to estimate the potential contribution toward an impact category. In this example, global warming potential (GWP) is presented in terms of equivalent emissions of carbon dioxide (CO2) using units of teragrams of carbon dioxide equivalents (Tg CO2 eq.):
Quantity of CO2 released = 90001 = 0.009 Tg (CO2 GWP factor value = 1)
Quantity of methane released = 50001 = 0.005 Tg (methane GWP factor value = 21)
GWP factor values are from the Intergovernmental Panel on Climate Change (IPCC) Model, 100 year time horizon, Third Assessment Report, 2001.
The key to impact characterization is using the appropriate characterization factor. For some impact categories, such as global warming and ozone depletion, there is a consensus on acceptable characterization factors. For other impact categories, such as resource depletion, consensus is still being developed.
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