RFA Credit Calculator (Methane and CO₂)
The same equations, applied to a project of your own
RFA is fully computable from project basics. Set an abatement schedule and a policy horizon; the per-year multipliers and the gap against static crediting follow directly from the equations.
What would RFA mean for a project like yours?
Enter an abatement schedule and a policy horizon. Every figure recomputes from the paper's equations: the same physics, applied to your numbers. Avoided CO₂ counts one-to-one under every method (equation 7); the difference between methods is entirely about methane. (Input negative values to account for emission leakage.)
View as table
| Year | tCH₄ | CH₄ multiplier | RFA tCO₂e (incl. CO₂) | GWP SAR tCO₂e (incl. CO₂) |
|---|---|---|---|---|
| Yr 1 | 5,000 | 30.0 | 250,136 | 205,000 |
| Yr 2 | 5,000 | 29.8 | 248,865 | 205,000 |
| Yr 3 | 5,000 | 29.5 | 247,617 | 205,000 |
| Yr 4 | 5,000 | 29.3 | 246,393 | 205,000 |
| Yr 5 | 5,000 | 29.0 | 245,191 | 205,000 |
| Yr 6 | 5,000 | 28.8 | 244,012 | 205,000 |
| Yr 7 | 5,000 | 28.6 | 242,854 | 205,000 |
| Yr 8 | 5,000 | 28.3 | 241,717 | 205,000 |
| Yr 9 | 5,000 | 28.1 | 240,600 | 205,000 |
| Yr 10 | 5,000 | 27.9 | 239,503 | 205,000 |
Where the credit comes from, as the horizon grows
For the mix entered above, methane dominates the credit at short horizons and fades as the window lengthens, because its forcing is concentrated up front while CO₂ persists. This is the whole time-horizon debate in one picture.
View as table
| Horizon T | Share from CH₄ | Share from CO₂ |
|---|---|---|
| 1 yr | 85.4% | 14.6% |
| 5 yr | 84.8% | 15.2% |
| 10 yr | 83.6% | 16.4% |
| 20 yr | 80.4% | 19.6% |
| 50 yr | 70.3% | 29.7% |
| 100 yr | 58.2% | 41.8% |
Background
Where the frozen number came from
Four short notes for readers new to carbon markets. If you already know what GWP₁₀₀ is and why its horizon is contested, skip to the figures.
Carbon credits
Projects that prevent greenhouse-gas emissions earn credits, each standing for one tonne of CO₂ kept out of the atmosphere, and the credits are bought and sold on carbon markets. The system needs an exchange rate the moment the avoided gas is anything other than CO₂.
Short-lived gases (like methane) warm on different clocks in comparison to CO₂
For example, a tonne of methane heats the planet far more than a tonne of CO₂, but it fades from the atmosphere in about 12 years, while CO₂ lingers for centuries. Any exchange rate between the two therefore depends on how long a period you score them over.
Markets settled on one frozen number
The rate in use is GWP₁₀₀: a gas’ warming impact averaged over 100 years, expressed in tonnes of CO₂. Under this rate, a gas cut today and cut in a decade are rewarded identically; the timing of the benefit is invisible.
The paper lets the rate move
Radiative Forcing-based Accounting keeps the same IPCC physics but integrates it over the time remaining in the policy window, so a gas cut early or later in a project counts differently. By the final project year the rate settles exactly on the current official value: nothing is invented, and the two methods agree at the boundary.
The physics
Every static GWP is one point on a single curve
Methane traps heat intensely but decays within decades; CO₂ lingers for centuries. Integrating their radiative forcing over any horizon T gives the equivalence multiplier for that horizon. RFA assigns each project a multiplier appropriate to their lifetime.
The multiplier is a curve, not a constant.
Every static GWP is one point on this curve. RFA credits each project year at the point the policy horizon actually implies (T = H − L + t), so early years of a project earn more per tonne than late years.
With H = 100 and a 10-year project, year 1 is credited at 30.0 tCO₂/tCH₄ (T = 91) declining to 27.9 in year 10 (T = 100), converging to the fixed GWP value at the boundary, in alignment with the study.
View as table
| Project year | Effective horizon T | Multiplier (tCO₂/tCH₄ = tCO₂e) |
|---|---|---|
| 1 | 91 | 30.0 |
| 2 | 92 | 29.8 |
| 3 | 93 | 29.5 |
| 4 | 94 | 29.3 |
| 5 | 95 | 29.0 |
| 6 | 96 | 28.8 |
| 7 | 97 | 28.6 |
| 8 | 98 | 28.3 |
| 9 | 99 | 28.1 |
| 10 | 100 | 27.9 |
The evidence
Four CDM projects, re-credited
The paper applies RFA to four methane-abatement projects registered under the UNFCCC Clean Development Mechanism: landfill gas, municipal waste, livestock manure, and industrial wastewater. CDM rules credited all four at a flat GWP₁₀₀ of 21, a value fixed in 1995.
Annual CO₂e credits: Xingfeng Landfill, 2008–2014
Captured and destroyed landfill methane while generating electricity. The largest of the four projects by an order of magnitude.
Annual profiles are digitized from the paper's supplementary figures S1 to S4; totals are exact and cumulative credits match supplementary Table S1 to three significant figures. Per-year multipliers match Figure 2 of the paper.
View as table
| Year | tCH₄ avoided | RFA multiplier | RFA tCO₂e | GWP SAR tCO₂e | GWP AR6 tCO₂e |
|---|---|---|---|---|---|
| 2008 | 39,218 | 29.3 | 1,148,245 | 823,578 | 1,094,183 |
| 2009 | 44,209 | 29.0 | 1,283,762 | 928,397 | 1,233,442 |
| 2010 | 47,537 | 28.8 | 1,369,176 | 998,277 | 1,326,282 |
| 2011 | 47,537 | 28.6 | 1,358,167 | 998,277 | 1,326,282 |
| 2012 | 44,447 | 28.3 | 1,259,779 | 933,389 | 1,240,074 |
| 2013 | 41,595 | 28.1 | 1,169,648 | 873,492 | 1,160,497 |
| 2014 | 38,743 | 27.9 | 1,080,943 | 813,596 | 1,080,920 |
Multiplier by project year: every project, every year
The paper's Figure 2, recomputed live. Bold: RFA multiplier (tCO₂/tCH₄ = tCO₂e). Small: Δ vs the static SAR value (21) that CDM rules actually applied. Hatched cells fall outside the project's crediting period.
| Year 1 | Year 2 | Year 3 | Year 4 | Year 5 | Year 6 | Year 7 | Year 8 | Year 9 | Year 10 | Year 11 | |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Xingfeng Landfill | 29.3▲8.3 | 29.0▲8.0 | 28.8▲7.8 | 28.6▲7.6 | 28.3▲7.3 | 28.1▲7.1 | 27.9▲6.9 | ||||
| Chandigarh MSW | 30.0▲9.0 | 29.8▲8.8 | 29.5▲8.5 | 29.3▲8.3 | 29.0▲8.0 | 28.8▲7.8 | 28.6▲7.6 | 28.3▲7.3 | 28.1▲7.1 | 27.9▲6.9 | |
| Brazil Livestock | 30.0▲9.0 | 29.8▲8.8 | 29.5▲8.5 | 29.3▲8.3 | 29.0▲8.0 | 28.8▲7.8 | 28.6▲7.6 | 28.3▲7.3 | 28.1▲7.1 | 27.9▲6.9 | |
| Tamil Nadu Wastewater | 30.3▲9.3 | 30.0▲9.0 | 29.8▲8.8 | 29.5▲8.5 | 29.3▲8.3 | 29.0▲8.0 | 28.8▲7.8 | 28.6▲7.6 | 28.3▲7.3 | 28.1▲7.1 | 27.9▲6.9 |
Longer projects start with higher multipliers (a longer remaining window), and every row converges to the AR6 boundary value of 27.9 at T = 100 by its final year.
View as table
| Project | Y1 | Y2 | Y3 | Y4 | Y5 | Y6 | Y7 | Y8 | Y9 | Y10 | Y11 |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Xingfeng Landfill | 29.3 | 29.0 | 28.8 | 28.6 | 28.3 | 28.1 | 27.9 | — | — | — | — |
| Chandigarh MSW | 30.0 | 29.8 | 29.5 | 29.3 | 29.0 | 28.8 | 28.6 | 28.3 | 28.1 | 27.9 | — |
| Brazil Livestock | 30.0 | 29.8 | 29.5 | 29.3 | 29.0 | 28.8 | 28.6 | 28.3 | 28.1 | 27.9 | — |
| Tamil Nadu Wastewater | 30.3 | 30.0 | 29.8 | 29.5 | 29.3 | 29.0 | 28.8 | 28.6 | 28.3 | 28.1 | 27.9 |
The method
The four equations behind this page
RFA rests on the same physical science as GWP itself: IPCC AR6 radiative efficiencies and impulse-response functions. What changes is how time is aggregated. The policy horizon becomes an explicit, governable parameter rather than a constant hidden inside a table.
Atmospheric decay (impulse-response functions)
CO₂ persists across four sink timescales (Joos et al. 2013, IPCC AR6); CH₄ decays with a single 12.4-year lifetime.
Integrated forcing (AGWP)
Radiative efficiency × persistence, integrated over the evaluation horizon T. AR6 values: RE꜀ₒ₂ = 1.33×10⁻⁵, RE꜀ₕ₄ = 5.70×10⁻⁴ W m⁻² ppb⁻¹ (indirect-inclusive).
The dynamic multiplier
The AGWP ratio, converted to mass terms. A continuous function of T rather than a fixed constant.
- M(1) = 117.1 · M(20) ≈ 81–82 (GWP₂₀ AR6) · M(100) = 27.9 (GWP₁₀₀ AR6)
- Static GWPs are single points on this curve. RFA keeps the whole curve.
The dynamic horizon & crediting
Policymakers declare one policy horizon H, an explicit and governable choice. Each project year t of an L-year project is then integrated over the window that actually remains.
- No new MRV: registries swap a fixed constant for a computed multiplier; nothing else changes.
- Governance: H must be standardized, project length L capped, fungibility and banking rules defined.
Radiative forcing-based accounting (RFA): a dynamic framework to replace static GWPs in carbon markets. Environ. Res. Lett. 21 064024 · CC BY 4.0