New LCA-Based GHG Accounting Framework and Protocols
–Part of Draft National Standard being Developed under ANSI Process
A new life-cycle assessment-based framework for GHG accounting and assessment has been developed to facilitate the work of climate registries, policy makers, business managers, life cycle assessment (LCA) practitioners and other stakeholders interested in evaluating the emissions of key GHGs associated with organizations, operations, and projects.
Under the “LCSEA GHG Accounting Framework (Annex B of SCS-002 National Standard, Committee Draft),” specific greenhouse gases (GHGs) are quantitatively linked to current and projected climate anomalies and exceedances of recognized climate thresholds. It is specifically designed to allow for the integration of up-to-date research, data and knowledge pertaining to climate change and to bridge the disciplines of climate science and life cycle assessment. It builds upon earlier GHG accounting protocols developed by the Intergovernmental Panel on Climate Change (IPCC). Under the framework, distinct GHG accounting protocols have been developed to address global, Arctic and Antarctic climate concerns.
The Climate Component of Draft National Standard SCS-002
The framework is described in the proposed climate annex to SCS-002, a draft national standard being developed under the American National Standards Institute process to guide the use of life-cycle assessment in a variety of policy setting, procurement, planning and investment applications.
Key Elements
The key technical components of the framework and protocols are summarized below:
- For global calculations, GHGs are classified as “key GHGs” if they currently contribute (or are projected to contribute) to global and/or regional radiative forcing, either positively or negatively, by at least ± 0.1 W/m². For regional calculations, GHGs are classified as key GHGs if they meet the ± 0.1 W/m² current or projected radiative forcing threshold, and if their contribution to radiative forcing in turn will cause the GMT or RMT to change by at least ± 0.1°C over the relevant time horizon.
- Relevant time horizons are assigned to the global and regional GHG accounting protocols, based upon timeframes of the observed or projected exceedances of linked thermal and structural thresholds.
- GWP values are assigned, with two additional considerations beyond standard IPCC protocols: 1) the lower limit for GWP values must be consistent with the GHG’s atmospheric lifetime, including both pulse and continuous emission sources, and 2) the GWP time horizon must be consistent with the time horizon assigned to the global and regional GHG accounting protocols.
- GWPs, Regional Warming Potentials (RWPs), and supporting equations are established for the short-lived GHGs &38211; tropospheric ozone (TO) and black carbon (BC).
- Global Cooling Potentials (GCPs), Regional Cooling Potentials (RCP) and supporting equations are established for halocarbons (i.e., CFCs, HCFCs, and halons) and tropospheric sulfate aerosols (TSA).
- Characterization factors beyond the GWP Index are established to account for regional and global effects.
- “Pulse warming potentials” (PWPs) are established to account for large biogenic pulses that radically change the relative concentrations of key GHGs in the atmosphere over time.
- Equations and accumulated GWP (“GWP*”) values are established to account for accumulated GHG loadings from major continuous sources.
- Protocols are provided to establish baselines for use in making comparisons, such as comparing different energy source options before they are installed and operated. These protocols take into account the various investment periods that provide strategic and security level assessments for such new source options.
List of Key GHG Emissions
The following table, extracted from the framework document, highlights the key GHGs that meet the threshold requirements of the respective global, Arctic and Antarctic GHG accounting protocols. It should be noted that the long-lived GHGs (carbon dioxide, nitrous oxide, HFCs, and CFCs) have much lower net radiative forcing contributions at the poles than their global annual average values, while the short-lived GHGs (tropospheric ozone, black carbon, and sulfate aerosols) result in significantly higher radiative forcing at the poles than their annualized averaged global radiative forcing values reported by the IPCC. The radiative forcing of methane increases in the Arctic region due to localized early springtime concentrations and its longer atmospheric lifetime in the Arctic.
| Key GHG Emissions | Global Radiative Forcing W/m² | Regional Radiative Forcing and RMT Contribution | |
| Radiative Forcing | RMT | ||
| GHGs contributing to Increased Radiative Forcing | |||
| Carbon dioxide (CO2) | +1.66 W/m² | Arctic: +0.27 W/m² | < +0.1°C |
| Nitrous Oxide (N2O) | +0.16 W/m² | Arctic: +0.02 W/m² | < +0.1°C |
| Hydrofluorocarbons (HFCs) | +0.02 W/m² (current) +0.34 W/m² (2030 projection) |
Arctic: +0.05 W/m² | < +0.1°C |
| CFCs | +0.33 W/m² | Arctic: +0.05 W/m² | < +0.1°C |
| Methane (CH4) | +0.48 W/m² | Arctic: +0.57 W/m² | +0.3 to 0.4°C |
| Tropospheric Ozone (TO) | +0.37 W/m² | Arctic & Antarctica ≤ +4 W/m² | +0.5°C |
| Black Carbon (BC) | +0.9 W/m² | +1.0 to +1.5°C | |
| GHGs contributing to Negative Radiative Forcing | |||
| Tropospheric Sulfate Aerosols | -0.9 W/m² | Known Arctic Coolant: ≤ -3.0 W/m² | > -1°C (Arctic) |
| Halocarbons - CFCs - HCFCs - Halons - Methyl Bromide |
Negligible | Known Antarctic Coolants: -4.0 to -6.0 Wm² | > -1°C (Antarctica) |
| Sea Salt Aerosols and Mineral Dust (Direct) Increase in scattering and albedo | -0.5 W/m² | Potential Arctic Coolant: - 3.0 to -7.0 W/m² | To be determined |
| Sea Salt Aerosols and Mineral Dust (Indirect) Increase in cloud albedo | -0.7 W/m&3178; (IPCC) | Potential Indirect Cooling From Arctic Aerosols -14 W/m² | To be determined |
