1. The Hierarchy of Emission Factor Specificity
Both the GHG Protocol Corporate Standard and IFRS S2 (§29(a)(iii)) require reporting entities to select emission factors that best reflect the physical fuel chemistry, grid topology, and operational technology of the reporting facility. When structuring an enterprise factor library, sustainability architects apply a strict specificity hierarchy:
- Facility-Specific / Continuous Emissions Monitoring (CEMS): Direct stack measurement or supplier-certified fuel chemical analysis.
- National & Sub-National Regulatory Schedules: Official government publications such as US EPA GHG Emission Factors Hub / eGRID for US operations, UK DESNZ Conversion Factors for UK operations, and DEWA / EWEC utility factors for UAE operations.
- Default International Baselines: IPCC Emission Factor Database (EFDB) Tier-1 default fuel factors when no national schedule exists for stationary or mobile combustion.
2. Technical Comparison: UK DESNZ vs. US EPA Hub vs. IPCC EFDB
Combining emission factors across datasets without checking calorific basis (Net/Lower Heating Value vs. Gross/Higher Heating Value) or Global Warming Potential (GWP) assessment report versions introduces systematic calculation errors of 5% to 11%.
| Technical Dimension | UK DESNZ Conversion Factors (2024 v1.1) | US EPA GHG Emission Factors Hub (2024) | IPCC EFDB (2006 / 2019 Refinement) |
|---|---|---|---|
| Primary Geographic Jurisdiction | United Kingdom (plus international flight distance factors) | United States (plus eGRID subregions for electricity) | Global Tier-1 defaults for all UN member countries |
| Calorific Basis (Natural Gas / Fuels) | Publishes both Gross CV (HHV) and Net CV (LHV) tables | Higher Heating Value (HHV / Gross Calorific Value) | Net Calorific Value (NCV / Lower Heating Value) |
| Gas Constituent Split | Disaggregates kg CO2e, kg CO2, kg CH4, and kg N2O | Publishes kg CO2, g CH4, and g N2O per unit | Publishes kg/TJ by gas with 95% confidence intervals |
| GWP-100 Horizon Basis | IPCC AR5 (CH4 = 28, N2O = 265) in 2024 schedule | IPCC AR5 / AR4 depending on EPA reporting rule citation | Native mass per gas (kg CH4, kg N2O); user applies AR5/AR6 |
| Redistribution & Commercial Licensing | Open Government Licence v3.0 (permissive with attribution) | US Federal Public Domain (unrestricted commercial & audit use) | Open public scientific reference; IEA country grid tables excluded |
3. Worked Heating Value & GWP Conversion Equation
When converting raw IPCC fuel factors expressed per Terajoule on a Net Calorific Value basis ($EF_{\text{NCV}}$) into total $\text{kg CO}_2\text{e}$ per physical liter or cubic meter, the deterministic calculation engine must apply consistent 100-year GWP multipliers ($\text{GWP}_{\text{CH}_4}, \text{GWP}_{\text{N}_2\text{O}}$):
Strict Non-Substitution Policy & Geographic Applicability (`GB` / `EU` / `US` / `AE`): In accordance with GetSustainable.ai's GHG Methodology v1.0.0 & v1.1.0, our Corporate GHG Screening Calculator never substitutes a UK DESNZ (GB) or US EPA (US) grid electricity factor for an unsupported country, and supports Emirate-specific UAE factors (AE-DUDEWA andAE-AZEWEC). When a localized electricity factor is unavailable in our open-licensed factor store, the engine returns a structuredMISSING_FACTOR_FOR_GEOGRAPHYerror rather than fabricating a proxy—a core requirement when evaluating platforms in our Carbon Accounting Software Directory.