Hello Tarlon,
To answer the question, i will assume you are using ecoinvent.
It sounds like you are using the LCI database, which only gives you the processes in elementary flows.
If you access the UPR database, you will see the market process divided into several streams. If you calculate the UPR as a product system, you will be able to see the CO2 from each stream. It might be easier to export the results, and treat the data in excel.
OpenLCA was not set up for this type of calculation, and there are allocation choices made in each database that do not necessarily align with the GHG protocol or ISO 14064. Use with caution.
I hope this helps, good luck.