Midpoint, endpoint and biogenic carbon in an insulation comparison
A construction client compares two insulation options for 1 m2 of facade at R = 4.0 m2K/W over a 50-year building life: 200 mm wood-fibre board (density 160 kg/m3) and 120 mm mineral wool (density 40 kg/m3). The practitioner runs ReCiPe 2016 v1.1 midpoint (H) and EF 3.1. Results per m2: wood fibre GWP100 = 12 kg CO2e including a -8 kg CO2e biogenic uptake; mineral wool = 14 kg CO2e. EF 3.1 gives wood fibre GWP-total = 4 kg CO2e (fossil 12, biogenic -8, luluc 0) and mineral wool 14 kg CO2e. At ReCiPe endpoint (H, E) the ranking reverses: wood fibre 2.1 x 10-6 DALY versus mineral wool 1.6 x 10-6 DALY, driven by land use and water use. The client wants to publish an EPD-based claim that wood fibre has 70% lower climate impact and use the result in a public procurement tender.
1. Which LCIA method should be used for the EPD and for the client's internal decision, and how should the biogenic carbon be handled?
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For the EPD, the method is not a free choice. EN 15804+A2 specifies the EF characterisation factors (version depends on the PCR) and requires separate disclosure of GWP-fossil, GWP-biogenic, GWP-luluc and GWP-total. ReCiPe cannot be substituted in the EPD declaration. For the internal decision, ReCiPe 2016 midpoint H is useful because it covers more impact categories, with endpoint only as a sensitivity.
The 70% claim is invalid because it compares GWP-total and treats the -8 kg biogenic uptake as a permanent removal. Whether that carbon returns depends on the end-of-life module: incineration releases it, landfill may store it. The like-for-like indicator is GWP-fossil: 12 versus 14 kg CO2e, about 14% lower, not 70%. Report GWP-biogenic and GWP-luluc separately, and include module D if the PCR requires it. Do not net biogenic uptake into a headline 'climate impact' figure unless the PCR and the declared end-of-life scenario explicitly allow it.
2. How should the client handle the midpoint/endpoint ranking reversal and the proposed public claim?
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The reversal means there is no method-independent winner. Wood fibre is better on fossil GWP, but worse on endpoint damage driven by land use and water use. For a public procurement tender, a comparative assertion requires the same PCR, the same functional unit and a critical review panel under ISO 14044. The client can publish EPD indicators with declared modules and state that wood fibre has lower GWP-fossil (if that survives the full module set), but cannot publish '70% lower climate impact'.
Recommended handling:
- Use GWP-fossil as the primary tender criterion, because it is robust and policy-relevant.
- Disclose the endpoint reversal and its drivers in the interpretation chapter.
- Run sensitivity on end-of-life (incineration versus landfill), electricity mix, and 100-year versus 500-year GWP.
- If a multi-criteria decision is wanted, agree weights in advance and document that weighting is value-laden.
State clearly that the climate ranking is robust for fossil GWP but not for endpoint damage, and that the public claim must be indicator-specific and reviewed.