Suggestion on how to adjust ecoinvent EN15804 GWP-biogenic indicator

Question

Hi,

I am working with ecoinvent 3.11 EN15804 database and have a suggestion regarding GWP-biogenic indicator.

This indicator is characterized as shown in attached screenshot.

The corresponding flows are present in ecoinvent database (eg. forestry activity processes). When realizing an EPD (or more generally a LCA) of (for example) wood products, the amount of biogenic CO2 stored in the modelled material is likely to be different from the amount in ecoinvent database. This can happen for many reasons (uncorrect modelling in ecoinvent, use of proxy process, normative or program operator requirements, possibly others). Thus, the default characterization of this indicator by EN15804 methods will lead to uncorrect results.

Therefore, I would suggect to add a dedicated elementary flow (characterized +1) that allows to adjust the amount of CO2 stored and released depending on the material, and to set all existing CO2 characterization to zero (top 6 lines factors in attached screenshot). The methane characterization factors remain unchanged.

This would be similar to what is done for PENRM and PERM indicators in ecoinvent 3.11 EN15804 method.

I understand this adds a manual step and complexifies the EPD work. But the corresponding risk is to get uncorrect results for GWP-biogenic indicator (which I see a lot in EPDs).

Please let me know your view on this.

Best regards,

Jocelyn

Answer 1

Characterization factors below:

https://ask.openlca.org/?qa=blob&qa_blobid=7632949361764362812

Answer 2

Dear Jocelyn,

Thank you for your valuable input. If I understand correctly, you mean to have 6 additionally elementary flows for manual and customized calculations of input and output biogenic carbon, so that the users can add these flows manually and balance the biogenic carbon without taking any biogenic carbon results from the background data sets into account?

An idea could be to add these 6 new flows and calling them "Carbon dioxide, non-fossil (manual accounting)" or something similar and then adding a new method called "EN15804+A2 (EF 3.1) - manual accounting of biogenic CO2" as an example. The already existing method would stay as it is, so that users could decide to calculate it manually in the foreground, or automatically as it is defined in the background database. I agree that some biogenic carbon in ecoinvent might not be correct or too far away from the user model due to the generic or proxy or errorneous nature of the data set.

Do you know if other EPD tools using the ecoinvent database also do not take any of the background database results for biogenic carbon into account? It is a dilemma that modelers need to chose between life cycle indicators (taking the whole supply chain into account, which is a huge strength of LCA) but maybe prone to errors, or only assessing fixed values manually in the foreground and losing the perspective over the whole supply chain.

PS: Why are these flows called "biogenic" and not "non-fossil" in your screenshot, since we harmonized these namings with ecoinvent and in the EN15804 add-on they are called "non-fossil"? The choice of the naming is not important, I just ask out of interest. Maybe you added the method to a different/older database without overwriting the flow names during import?

Best wishes,

Conrad

Comments

Thanks Conrad,
I would actually only add one elementary flow, "carbon dioxide, biogenic | GWP-biogenic", characterized +1. This would be input with a positive value for carbon storing and output with a positive value for carbon releasing.
I am aware of some methods developped for EPDs that do not characterize biogenic CO2 background flows.
Regarding your last comment, I will check why I have this modification, thanks!

---

You are right. One additional elementary flow would be enough, since the openLCA impact direction feature will allow to calculate it with the right sign, depending if it is modeled on the input or on the output side. Also the compartments are not needed, since it doesn't matter for biogenic CO2. This flow can be added to the already existing default method (with accounting of the supply chain) and it can be added to the new method (where the background biogenic CO2 will be set to zero).