Biogenic carbon
What is a biogenic carbon?
Biogenic carbon is the carbon that is stored in biological materials, such as plants or soil. Carbon accumulates in plants through the process of photosynthesis and therefore bio-based products can contribute to reduce the levels of carbon dioxide in the atmosphere and help mitigate the challenge of climate change. Biogenic carbon within a building product can therefore be considered as a "negative emission". This means that during the growth stage of bio-based materials carbon is stored into the material.
If the biomass is harvested and burned this carbon is released back to atmosphere. However, according to most LCA methodologies such as (CML, TRACI, EN 15978) carbon dioxide emissions from burning renewable materials are not included in GWP as the material is considered to grow back in few decades and tie back the carbon if the area of forest does not change.
When a bio-based material is used for a building product instead of burning the carbon will be stored as long as the material is used so until the end of life of the building. At the moment, the most likely end of life scenario for wood products waste handling at end-of-life is incineration in which case the stored carbon is released back to atmosphere. This means that carbon is stored for few decades but the total carbon balance over lifetime of building is zero.
One Click LCA uses two optional methods for taking this into account. In the generic method, the biogenic carbon storage is only shown as additional information. This means that either the negative emissions of storing the CO2 from atmosphere in A1 or the releasing it in C3 are not included in GWP results.
In DGNB and Energie Carbon tools the biogenic carbon storage over lifetime is reported as part of the GWP results. In this case the negative emissions from storing the carbon are shown as part of A1-A3 (storage is deducted from the GWP emissions in A1-A3) and in C3 where same amount of carbon is added as it is released back to atmosphere.
In both methods the total GWP result is the same.
Biogenic carbon counting in One Click LCA
Building materials
Biogenic carbon is included to the calculations in 2 ways
- The value is provided in the building material EPD
- The value is not declared and we provide a close estimation.
The calculation rule for the estimation is following the EN 16449:2014 Wood and wood-based products. Calculation of the biogenic carbon content of wood and conversion to carbon dioxide
When biogenic carbon is not declared in the EPD, then often some other variables needed for the calculations require assumptions:
- the carbon content (C) is assumed to be 50%
- the material is assumed to be fully dry, therefore
- the third member of the equation is reduced to [density(of dry)] x [volume]
- 44/12 is the ratio between the molecular mass of CO2 and C molecules
Energy resources
Our energy data is entirely based on the Ecoinvent database. Ecoinvent declares the biogenic carbon content and we can calculate the share of it in different fuel types and combinations of them. The biogenic carbon content in the Ecoinvent data is declared in the LCI of each resource as carbon dioxide in the air. [https://www.ecoinvent.org/files/dataqualityguideline_ecoinvent_3_20130506.pdf]
Biogenic carbon info of your material resource
Biogenic carbon info is visible for all applicable materials in the additional information info-bubble (green question mark next to the resource). You can recognize biogenic carbon from a tree icon.
One Click LCA does not deduct biogenic carbon from the A1-A3 impacts.
For certain calculation tools, such as DGNB and Energie Carbone, the data has mirror copies for these methodologies that require using data with biogenic data deducted from A1-A3 emissions (and re-releasing it in end of life stage). In such cases the ‘copy dataset’ will contain expression ‘biogenic CO2 not subtracted’ in the name and technical specification. You can always find this info in the additional information bubble. You can never choose both the copy and the unmodified dataset in the same tool, and you will only be able to access the data that complies with the methodology of your certification.
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