Biogenic carbon is derived from biological sources such as plants and animals, influencing Life Cycle Assessments (LCAs). Calculating biogenic carbon and its associated emissions is essential for understanding the true environmental impact of a product. This article covers the following questions:
What is biogenic carbon?
How do different standards account for biogenic carbon?
How to perform biogenic carbon calculations?
Feel like you're missing information? This article builds upon the following articles. Check them out if you want to learn more:
On LCA standards: Explained: LCA standards
On LCIA methods/ standards: Explained: LCIA Methods
On impact categories: Explained: Environmental impact categories
What is biogenic carbon?
Biogenic carbon is carbon derived from biological sources, such as plants or animals, and excludes fossil carbon. To illustrate, carbon stored in trees or released during the decomposition of organic matter is biogenic.
Note - Peat: Peat, due to its slow regeneration rate, is treated as fossil carbon.
How do different standards account for biogenic carbon in LCA?
Not all LCA standards approach biogenic carbon calculations the same, reflecting the complexity of accounting for carbon cycles in environmental impact assessments. Below we outline some of the similarities and differences between standards.
What are common practices across standards?
General alignment: Most standards align with ISO 14040 and ISO 14044, except for the IPCC and GHG Protocol standards. These guidelines provide a framework for calculating and reporting biogenic carbon.
100-year assessment period: All standards recommend assessing global warming potential (GWP) over 100 years, consistent with IPCC guidelines. This timeframe helps capture the long-term effects of carbon emissions and storage.
Carbon flows: Carbon absorbed by biomass is treated as a negative flow, representing the removal of carbon from the atmosphere. Conversely, carbon released from biomass is treated as a positive flow, adding carbon to the atmosphere. This approach is often referred to as the -1/+1 method.
End-of-life considerations: In cradle-to-grave assessments, the end-of-life phase is crucial for accounting for biogenic carbon. All standards require that biogenic carbon be considered in this phase.
Separate reporting: Biogenic carbon must be reported separately from fossil carbon in all LCAs, ensuring clear differentiation between the two types of carbon.
What are differences across standards?
Definitions: While all standards agree on the basic definition of biogenic carbon, they differ in their specific inclusions and exclusions. This impacts how biogenic carbon is calculated and reported.
Implementation of -1/+1 approach: The -1/+1 approach is a common method, but each standard has its own rules for applying it, particularly regarding carbon stored within the 100-year assessment period.
Storage definitions: Different standards define carbon storage and its duration in various ways. Some include temporary storage within the 100-year period, while others do not.
Cradle-to-gate studies: There is no consensus on including biogenic carbon in cradle-to-gate studies. Some standards exclude it to maintain balance, as the carbon flux isn't balanced until the end of life.
Application across standards
Table 1: Comparative analysis of biogenic carbon considerations across standards
Standards | Clauses in definition | Approach | Storage | Region |
ISO 14067 | Does not include peat or geological carbon that was once biological. | -1/+1 | No - All emissions and removals are considered as released at the beginning of an assessment | Global |
GHG Protocols – Product Life Cycle Accounting | Includes “a variety of” soil and water-based sources. If the origin is ambiguous then count as non-biogenic. | -1/+1 | Yes - If not released to the atmosphere during waste treatment | Global |
ILCD Handbook | No explicit inclusions or exclusions were noted. | -1/+1 | Yes - Credits for storage* | Global |
PAS 2050 | Includes CO2 from air converted into non-biomass carbonates. Does not include soil carbon. | -1/+1 (-1/0**) | Yes - Considered for 100+ years only | UK with global adoption |
PEFCR Guidance | Does not include soil carbon. | -1/+1 (-1/0**) | Yes - Considered permanent after 100 years | Global |
EN 15804 | Includes carbon transfers to/from: non-native forests, other product systems, emissions to air from combustion or degradation | -1/+1 | No - neither temporary nor permanent storage is included | EU |
IPCC Guidelines for National GHG Inventories | Plant or animal biomass. Excludes peat due to long restoration period | -1/+1 | Yes – Not specific to biogenic carbon, any storage in a carbon pool is to be accounted for | Global |
*Credits awarded for storage equal to “no. years stored”/100 in the short-term perspective
**If carbon remains in the biomass for 100+ years
Note - Cut-off criteria: Use the criteria (aka rules or thresholds) per standard (Table 2) to decide which biogenic emissions to include in your LCA model.
Table 2: Cutoff criteria for biogenic carbon as per different standards
Standard | Biogenic C content | GWP Biogenic (incl. biogenic emissions and removals) | Biogenic C content (Cut-off) | Material/Energy (Cut-off) |
NMD | Yes, EN 15804/A2:2019 applies [1] Section 2.7.2.5 | Yes, [1][2] | EN 15804/A2:2019 applies | EN 15804/A2:2019 applies |
EN 15804/A2: 2019 | Yes, Biogenic carbon content in product and packaging, [3] Section 7.2.5 | Yes [3] | If the mass of biogenic carbon-containing materials in the product/packaging is less than 5% of the mass of the product/packaging, the declaration of biogenic carbon content may be omitted [3] Section 6.4.4 | <5% of the mass and energy usage per module (e.g. A1-A3, A4-A5, B1-B5, C3-C4 and D). [3] Section 6.3.6
If the individual material is less than 1% ignore the material [3] section 6.3.6
|
PCF (PACT ) | Yes, [5] Appendix B | Yes, from
2025 onwards. [5] Appendix B
| - | individual processes representing <1% of CtG PCF and in aggregate <5% [5][6] |
ISO 14067 | Yes | Yes |
|
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How to perform biogenic carbon calculations?
At Ecochain, we have developed a specific methodology to estimate biogenic carbon and its associated emissions. Follow these steps to perform the calculations:
Determine the need for biogenic carbon estimation: Check if biogenic carbon estimation is required based on the LCA scope and the standards applicable to your product.
Check cut-off criteria: Review the cut-off criteria specific to the standards you are following. This will help determine if certain biogenic carbon flows should be included or excluded.
Use the decision-making tree: Follow the decision-making tree (download below) to estimate the carbon content in the material. This process ensures that you consider all relevant factors in your estimation.
Estimate GWP biogenic
Downloads
What is still under research in biogenic carbon estimation?
There are ongoing research efforts to refine biogenic carbon estimation, particularly in the following areas:
Soil carbon inclusion: Different standards vary in their treatment of soil carbon. For example, GHG Protocols include some aspects, while PEFCR classifies all soil carbon as part of the land use change indicator.
CO₂ uptake and release: Standards agree on CO₂ uptake in biomass but differ on handling CO₂ release, especially for long-term storage scenarios like construction or landfill timber.
Temporary vs. permanent storage: Some standards, like the ILCD Handbook, credit temporary storage for not contributing to radiative forcing. Others, such as PAS 2050 and PEFCR, consider carbon permanently stored after 100 years but do not credit temporary storage.
Cradle-to-gate assessments: EN 15804 excludes biogenic carbon from cradle-to-gate assessments, while others include it with varying methodologies.
Next steps
Understanding biogenic carbon within the context of LCA helps accurately assess the environmental impact of products. Depending on how LCA standards and cut-off criteria are applied, biogenic carbon can either be included or excluded from an LCA. When included, it requires careful consideration of its temporary sequestration and eventual release, ensuring that the full environmental picture is captured. By setting appropriate cut-off criteria, practitioners can ensure that the most relevant aspects of biogenic carbon are taken into account, leading to a more comprehensive and accurate environmental impact assessment.
Understanding and applying these concepts effectively helps bridge the gap between raw environmental data and actionable insights, ultimately supporting more sustainable decision-making.
