Carbon modeling in the PEF initiative
The Product Environmental Footprint (PEF) approach aims to standardize and simplify LCA practice while maintaining its high quality. To enable all LCA practitioners to use the same approach, Product Environmental Footprint Category Rules (PEFCRs) are being developed. In this edition of the PEF series, we describe the state of the art of carbon modeling.
Three Sub-indicators For Climate Change
For the impact assessment of carbon flows there are two important guidance documents to consider: the PEF guide (2013), which provides rules on the modeling approach for biogenic carbon, and an additional guidance document from De Schryver and colleagues (2016), which will aid the development and implementation of the PEFCRs.
Carbon modeling with PEFCRs includes three different sub-indicators for climate change, as illustrated in the figure below:
- Climate change – fossil: greenhouse gas (GHG) emissions to any media originating from the oxidation and/or reduction of fossil fuels by means of their transformation or degradation (e.g. combustion, digestion, landfilling, etc.).
- Climate change – biogenic: carbon emissions to air (CO2, CO and CH4) originating from the oxidation and/or reduction of biomass by means of its transformation or degradation (e.g. combustion, digestion, composting, landfilling), and CO2 uptake from the atmosphere through photosynthesis during biomass growth.
- Climate change – land use and land transformation: carbon uptake and emissions (CO2, CO and CH4) originating from carbon stock changes caused by direct land-use change, soil carbon uptake (accumulation) and emissions through land management (land use).
Temporary Or Permanent Carbon Storage
The approach to carbon modeling outlined in the PEF guide excludes credits associated with temporary carbon storage or delayed emissions. They are not a default EF impact category but may be included as additional environmental information.
Carbon storage is considered permanent if the carbon is only expected to be emitted again more than three centuries after its uptake. In contrast, emissions expected to occur within three centuries (delayed emissions or temporary storage) are modeled as if emitted now.
Consistent With ILCD
All flows should be modeled consistently with the most recent ILCD list of elementary flows. For flows from sub-indicator 1, the names ending with ‘(fossil)’ (e.g., ‘carbon dioxide (fossil)” and ‘methane (fossil)’) should be used if available. For flows from sub-indicator 2, the names ending with ‘(biogenic)’ (e.g., ‘carbon dioxide (biogenic)” and ‘methane (biogenic)’) should be used if available. No specific flows were available for sub-indicator 3 when the guidance document was produced.
Modeling Flows Separately
Biogenic carbon uptakes and emissions have to be inventoried separately for each elementary flow. The allocation rules described in the PEFCR for all other elementary flows should also be applied to modeling the biogenic carbon flows. The guidance document provides two options for modeling biogenic uptake and emissions: (1) modeling all biogenic carbon flows, which allows carbon tracking, but may also require complex modeling or (2) leaving out the biogenic CO2 and modeling only the biogenic CH4 emissions, which influence the impact on climate change.
For the third sub-indicator describing land use and land transformation, all carbon flows have to be modeled separately. The uptake of carbon by soil via improved land management should be excluded from the footprint results but may be reported as additional information when sector legislations have different requirements. Furthermore, the PEF guides PAS 2050:2011 and PAS2050-1:2012 for horticultural products should be followed.
The guidelines provided by De Schryver and colleagues will be implemented in the final PEFCRS. For more details, I refer to the original guidance document from De Schryver and colleagues, and to the PEF guides PAS 2050:2011 and PAS2050-1:2012.
Learn more about PEF
If you want to learn more about our role in the PEF initiative, please contact us. See other episodes of this series:
- PEF: A game changer in LCA
- PEF: End-of-life modeling
- PEF: The role of the representative product
- PEF: Hotspot analysis
- PEF: Data requirements
- PEF: Governance structure
- PEF: Impact assessment
- PEF: Carbon modeling
- PEF: Environmental footprint of organizations
- PEF: Guidance for modeling the use stage
- PEF: Energy and transport data
- PEF: State of the debate and outlook
- PEF: The end of the pilor phase
- EF: Transition phase
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