Am I right that your comment is similar what you have replied already here on GDP? My impression is that like in the GDP discussion you are proposing a breakdown of each modelling step by creating an activity object for each model variable (e.g. along an impact chain). Since, however, there might be a databases/ file somewhere on the web where a list of characterisation factors (like there are GDP data per country online), this dataset on the web could be linked to our flows directly and used for e.g. for validation the results obtained from the query mentioned above, or even for calculations without using the model breakdown.
However, I don’t understand why in the first example you want to “follow the methane through some activities” and in the second one you want to use directly “weighting factors”. Seems inconsistent to me.
From: <email@example.com> on behalf of "Bo Weidema via Groups.Io" <bo.weidema@...>
Den 2019-03-13 kl. 16.28 skrev Massimo Pizzol:
What flows out of the steel production is carbon dioxide. 1 kg of carbon dioxide = 1 kg of carbon dioxide equivalents, so I assume what you are thinking of is rather if the output was of, say, methane, which can also be expressed in carbon dioxide equivalents under a specific macro-economic scenario, and depending on where in the impact pathway you define the equivalence. So the most consistent way of dealing with this is to follow the methane through the following ecosystem activities "atmospheric energy balance" and "temperature increase" as a result of the additional input of methane. These processes will have outputs expressed in radiative forcing and temperature change, which can of course be compared to the radiative forcing and temperature change from a kg of carbon dioxide, so that you obtain the impacts of methane in carbon dioxide equivalents at the point in the impact pathway that you are interested in.
The global warming potential (given a specified time horizon) is a weighting factor applied to each greenhouse gas. This is most easily included in a separate weighting step. This could be done by adding the weighting as an activity, but I would suggest to use the E matrix suggested in http://lca-net.com/p/2865 for this purpose.