What is 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 reducing 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 a "negative emission". This means that during the growth stage of bio-based materials carbon is stored in the material.

If the biomass is harvested and burned this carbon is released back into the atmosphere. However, according to most LCA methodologies such as (CML, TRACI, and EN 15978) carbon dioxide emissions from burning renewable materials are not included in GWP as the material is considered to grow back in a few decades and tie back the carbon if the area of the 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 into the atmosphere. This means that carbon is stored for a few decades but the total carbon balance over the lifetime of the building is zero.

How Do We Account For Biogenic Carbon?

One Click LCA uses several methods for taking this into account, we make a distinction between 'generic' methods which are used in most of the tools, and 'regulatory' methods which are according to specific regulatory requirements.

Generic Methods

1. Tools that use only CML (EN15804+A1) or only TRACI data

Biogenic carbon storage is only shown as additional information.

Negative emissions of storing CO2 from the atmosphere are not included in A1-A3
Emissions from releasing CO2 are not included in C3.

This means that neither the negative emissions of storing the CO2 from the atmosphere in A1 nor the release of it in C3 is included in GWP results.

2. Tools that use both CML (EN15804+A1) and EN15804+A2 (GWP-FOSSIL only)

Biogenic carbon storage is only shown as additional information

Negative emissions of storing CO2 from the atmosphere are not included in A1-A3
Emissions from releasing CO2 are not included in C3.

This means that neither the negative emissions of storing the CO2 from the atmosphere in A1 nor the release of it in C3 is included in GWP results. From EN15804+A2 EPDs in this method we only take GWP-FOSSIL.

3. Tools that use both CML (EN15804+A1) and EN15804+A2 (GWP FOSSIL, LULUC, and BIOGENIC)

Biogenic carbon storage is reported as part of the GWP results.

Currently, there is only 1 calculation tool that uses this method. This is the Level(s) Carbon tool which uses both CML (EN15804+A1) and EN15804+A2 data.

If the resource has only +A2 data or only +A1 data, the negative emissions of storing CO2 from the atmosphere are included in A1-A3 and the emissions from releasing CO2 are included in C3 (or C4 if the EOL is landfilling). Negative emissions are reported under GWP-Biogenic and GWP-Total, emissions from releasing CO2 are dependent on the chosen end-of-life method.
If the resource has +A1 and +A2 data, the emissions will be reported in the same way as described above.

4. Tools use only EN15804+A2 data

Biogenic carbon storage is reported as part of the GWP results, although the GWP results as per standard are covered by multiple GWP indicators.

Currently, there is only 1 calculation tool that uses this method. This is the Level(s) LCA tool which uses only EN15804+A2 data. Due to the differences between the Product Category Rules between EPD programs, there is variance in the way the biogenic impacts are accounted for.

Instead of balancing the biogenic impacts based on the biogenic carbon storage, this tool now uses GWP-biogenic impacts as reported in the EPDs. The GWP-biogenic value is always used from the EPD for A1-A3 and A5 LCA stages, C2-C4 and D. This applies, only if the LCA parameter for End of life calculation has been set to "Use EPD EOL scenario, user adjustable". Please see the help article on this here - Selecting Project Parameters

Negative emissions of storing CO2 from the atmosphere are reported under GWP-Biogenic only
Emissions from releasing CO2 are dependent on the chosen end-of-life method. E.g. Incineration would assign the emissions to C3 and Landfilling to C4.

Regulatory Methods

1. In DGNB and Energie Carbon/RE2020

Biogenic carbon storage is reported as part of the GWP results.

Negative emissions from storing CO2 from the atmosphere are included in A1-A3
Emissions from releasing CO2 are included in C3.

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 the same amount of carbon is added as it is released back to the atmosphere. In both methods, the total GWP result is the same.

2. In RICS v.1/GLA/Green Mark

Biogenic carbon storage is partially reported as part of the GWP results.

Negative emissions from storing CO2 from the atmosphere are not included in A1-A3
Emissions from releasing CO2 are included in C3.

In exception to these methods, for GLA calculations the biogenic carbon is not included in A1-A3 (it is reported separately) but the release of stored carbon is considered in the C3 stage. This is due to the format of the GLA submission template which has in-built queries for calculating total emissions.

Biogenic Carbon Counting in One Click LCA

In Building Materials

Biogenic carbon is included in 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 EN 16449:2014 Wood and wood-based products. Calculation of the biogenic carbon content of wood and conversion to carbon dioxide

Calculation rule for biogenic carbon

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

In Energy Resources

Our energy data is entirely based on the Ecoinvent database. Ecoinvent declares the biogenic carbon content and we can calculate its 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.

Biogenic Carbon Information of your material resource

Biogenic carbon info is visible for all application materials in the additional information info bubble (green question mark next to the resource). You can recognize biogenic carbon from a tree icon.

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 the end-of-life stage). In such cases, the ‘copy dataset’ will contain the 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.