Why is CO2-non fossil not accounted for in the IPCC 2021 - Biogenic category

Question

I am wondering why does the "ecoInvent - IPCC 2021 climate change: biogenic - global warming potential" impact category does not account for CO2 - non fossil. 

Is there a way we can include CO2-non fossil in the "biogenic" results? 

Thank you very much.  

Answer 1

The "standard" and recommended approach from IPCC 2021 has net zero impacts of biogenic CO2 uptake and emission. It is a somewhat safe approach where one can assume that any biogenic carbon ends up in the atmosphere anyway at one point, so the net impact from uptake and emission is zero. This results in a characterisation factor of zero for "carbon dioxide, non-fossil" and for "carbon dioxide, in air", which is excluded from the characterisation factors and not shown in the impact category (we usually exclude characterisation factors that are zero). Maybe, at least for CO2, we could include the zero values into the characterisation factor tables to highlight there that these values are zero on purpose and not missing.

You are mentioning the ecoinvent implementation of IPCC 2021, which is only compatible with the ecoinvent database and where the biogenic carbon dioxide is set to zero correctly. You can even find the ecoinvent implementation (mapping) here:

https://github.com/ecoinvent/lcia/blob/master/3.10/methods_mapped/IPCC%202021_mapped_3.10.csv

You can include biogenic carbon by adding all elementary flows "Carbon dioxide, non-fossil" with +1, "Carbon dioxide, in air" with -1, "Carbon dioxide, non-fossil, resource correction" with -1 and changing all "Methane, non-fossil" from 27.0 to 29.8, which is similar to the EN15804 based on EF 3.1 and using IPCC 2021 for climate change categories.

But be aware that when the full life cycle is modelled and there is no significant carbon sink that lasts for several thousand years there should be (theoretically) no difference between tracking biogenic CO2 uptake/emissions (-1/+1) or putting it to net zero (0/0). But the risk is that explicitly tracking biogenic carbon uptake and emission can lead to unjustified claims of carbon credits or low carbon footprints due to the advantageous carbon uptakes in incomplete cradle-to-gate LCAs with no subsequent modelled release back into the atmosphere.

Comments

Ok, so the way I was modeling it is that I create a flow and add properties to it, e.g. "CO2_wt_incorporated".

Firstly, is this the right approach or should I add every component flowing into my unit as a seperate flow?

And secondly, are the CO2 emmissions accounted for if I do it like that?

If not, does it mean that I have to do all this:
"ou can include biogenic carbon by adding all elementary flows "Carbon dioxide, non-fossil" with +1, "Carbon dioxide, in air" with -1, "Carbon dioxide, non-fossil, resource correction" with -1 and changing all "Methane, non-fossil" from 27.0 to 29.8, which is similar to the EN15804 based on EF 3.1 and using IPCC 2021 for climate change categories."

..just to account the CO2 emmissions? In my opinion the IPCC approach is wrong, it is not necessarily true that any biogenic carbon will go into the atmosphere, why couldn't a plant just die down and become earth again? This is the default cycle if nothing and noone would interfere. Also a LCA is a snapshot, I can't account what will happen in the next 1000 years.