biogenic carbon content using IPCC 2021 (incl. biogenic carbon)

Question

Hi there,

I am using the ecoinvent 3.11 database and IPCC2021 (incl. biogenic co2) as impact assessment method. I have wood products that are part of my product system and I do not model EoL for those (they are assumed to be placed in a peatland and won't be removed). In the logic of biogenic carbon assessment, during the production of the wood products, an uptake (-1) of biogenic carbon will be modelled. Because I do not model EoL for those products, the consequential release of the biogenic carbon (+1) is not being modeled. Now I want to know how much biogenic carbon is stored in the wood products according to ecoinvent. I see two options: When looking at the contribution tree I can choose elementary flows. I used "carbon dioxide, in air (non-fossil)" and "carbon dioxide, resource correction" to calculate the amount of carbon stored for my specific process. The other option is to look at the total results for biogenic carbon and use the value shown for my process in question (which is smaller then the value from the elementary flows). What is the right way here?

And besides: almost never do processes have a total result for biogenic carbon of 0 t CO2-eq. (which they should in the logic of -1/+1 biogenic carbon accounting, don't they?).

Thanks for the help.

Answer 1

Hello,

The first option with the flows would be better, as it allows you to trace where the flows are contributing. In some cases, carbon dioxide in air may be part of a background process related to production not the wood product itself, and this distinction can be important.

Regarding the second option, the GWP biogenic impact category accounts for the overall uptake and emissions combined, so the total result may be lower than a single uptake towards your product depending on your product system.

I actually do not think there is a process that has total results for biogenic carbon equal to 0 kg CO₂ eq., as there is not always a perfectly equivalent end-of-life process for every process that produces a wood-based or other biogenic material. In practice, carbon accounting is often carried out manually.