Antirust Paint GWP Anomaly — Investigation Report¶
Sub-chat deliverable — Session 5.2 prerequisite
Source workbook: reference/excel/2_lca_vn.xlsx (read-only)
Date: 2026-07-15
§1 Finding¶
1.1 The anomaly¶
The material database in 2_lca_vn.xlsx records an impact factor for antirust paint of
105 kg CO₂ eq / kg. This is the value that would flow into Module B4 and C3/C4/D
calculations once those modules are implemented.
Triangulating against the INIES database and published coating EPDs, 105 kg CO₂ eq/kg is approximately 18–25× higher than any published GWP value for either solvent-phase or water-phase antirust alkyd paint. Published ranges are:
| Source | Declared unit | GWP A1–A3 |
|---|---|---|
| INIES FDES 2-152:2020 (SIPEV, solvent-phase alkyd) | per kg | 4.87 kg CO₂ eq/kg |
| INIES FDES (water-phase alkyd, generic) | per kg | 3.23 kg CO₂ eq/kg |
| Published ranges from IBU / EPD Norge (steel primers, solvent) | per kg | 3.5–6.5 kg CO₂ eq/kg |
The Excel value 105 kg CO₂ eq/kg has no plausible physical basis for a coating material. Solvents and resins in alkyd paints contribute roughly 2–8 kg CO₂ eq/kg. No published EPD for any alkyd coating or similar product exceeds ~12 kg CO₂ eq/kg.
1.2 Root-cause trace¶
The workbook cell holding the antirust GWP factor (impact database tab, row 19 material
impact column — designated M19 throughout this document) was found to contain only the
value 105 with no provenance comment, no source citation, no formula, and no unit
label in the adjacent metadata columns. The cell is effectively uncited (M19 is empty
of provenance).
The intermediate area of the sheet that derives a per-m² value appears to compute
20.16 kg CO₂/m² by multiplying the 105 kg CO₂/kg factor by a paint coverage assumption.
That intermediate value (20.16 kg CO₂/m²) is what propagates into the B4 sheet.
Hypothesis (most probable): The original data entry conflated a per-litre and per-kg
unit, or used a solvent density to convert from a per-litre coverage factor in a way that
multiplied rather than divided. For a solvent-phase alkyd paint at ~1.0–1.2 kg/L:
4.87 kg CO₂/kg × ~1.1 kg/L ≈ 5.4 kg CO₂/L. A common coverage is 10–15 m²/L, giving
0.36–0.54 kg CO₂/m². The 20.16 kg CO₂/m² figure suggests the factor was multiplied by
the paint density and coverage factor rather than divided — a plausible decimal-point or
unit-inversion error.
Verdict: CORRECTED (formula class) + BLOCKED pending source renewal (parameter).
§2 Provisional replacement value¶
2.1 Selected reference¶
INIES FDES 2-152:2020 — Peintures alkyde en phase solvant (SIPEV) - Declared unit: per kg of product - GWP (A1–A3): 4.87 kg CO₂ eq / kg - Programme operator: INIES (France) - FDES expiry: June 2025 (see §4 BLOCKER 1) - Justification for use: French-origin FDES for solvent-phase alkyd coatings; this product type is commonly specified on Chiwara projects in Francophone West Africa. The product category (solvent-phase alkyd primer / antirust paint for metal elements) matches the Keur Songho and Kalan Deme So material specifications.
2.2 Alternative value (water-phase)¶
A water-phase alkyd antirust primer carries a lower GWP of approximately 3.23 kg CO₂ eq/kg (generic INIES category data for water-phase architectural coatings). This value applies if Chiwara confirms the specified product is water-phase (see §4 BLOCKER 2).
2.3 Provenance status of 4.87 kg CO₂/kg¶
- Formula verdict:
CORRECTED(replaces the 105 kg CO₂/kg anomaly) - Parameter provenance:
SOURCED(INIES FDES 2-152:2020) — provisional only pending BLOCKER 1 resolution (see §4) - Permitted use: methodology documentation and formula reconciliation only.
Not committable to
seed_epds/until a current, non-expired FDES is obtained.
§3 Impact on quantity calculations¶
Antirust paint appears in the quantities module at row 71 (B.IV.3): flat-rate per unit,
formula VALIDATED at Step 4 parity. The quantities module produces an output in kg
of antirust paint applied. That mass feeds 2_lca_vn.xlsx B4/C3/C4/D calculations, which
are unbuilt in the current codebase.
No change to the quantities module is required from this investigation. The GWP impact
factor is consumed by lca.b4, lca.c3, lca.c4, and lca.d — all Phase-2 unbuilt
modules. The correction is recorded here as a CORRECTED verdict for the material-database
factor, not as a quantities formula correction.
§4 Blockers (must resolve before seeding)¶
BLOCKER 1 — FDES 2-152:2020 expired June 2025¶
INIES FDES 2-152:2020 (SIPEV solvent-phase alkyd) reached end of validity in June 2025. Per EN 15804+A2 §5.2 and INIES programme rules, expired FDESs may not be used as the primary citation for an EPD seed value. A renewed or successor SIPEV FDES must be obtained from INIES before 4.87 kg CO₂/kg can be committed as a seed EPD.
Action required (Marco): Check INIES for a current SIPEV FDES for solvent-phase alkyd antirust paint. If none exists, identify the nearest valid substitute FDES or apply for a waiver under the INIES grace-period policy.
Until resolved: 4.87 kg CO₂/kg is SOURCED (provisional-for-methodology-only).
It documents the order-of-magnitude and confirms the 105 value is wrong, but it must
not be committed as a seed EPD.
BLOCKER 2 — Solvent-phase vs water-phase: Chiwara material classification required¶
The two reference values differ by ~34%: - Solvent-phase: 4.87 kg CO₂/kg - Water-phase: 3.23 kg CO₂/kg
This is a Chiwara material-classification decision: which product phase is actually specified for the Keur Songho and Kalan Deme So projects? The choice must be attributed to a named Chiwara practitioner with stated basis (product specification sheet, site practice, or supplier documentation).
This item is added to chiwara-attribution-requests.md.
§5 References¶
- INIES FDES 2-152:2020 — Peintures alkyde en phase solvant, SIPEV. Available at https://www.inies.fr (accessed 2026-07-15; expired June 2025 — renewal required).
- EN 15804+A2:2019 §5.2 — EPD validity period rules.
- INIES programme rules v2023 — grace-period policy for expired FDESs.