Methodology and calculation walkthrough
Version 0.2.0 · 7 September 2026 · illustrative software proof of concept.
The engine estimates a scenario and exports its assumptions. It does not measure emissions, determine eligibility, issue credits or generate a certified monitoring report.
Independent worked example
| Input | Default scenario |
|---|---|
| Country baseline factor | 1.13 kg CH4/ha/day |
| Baseline / project water scaling | 1.00 / 0.55 |
| Pre-season scaling | 1.00 |
| Organic amendment scaling | 2.88 |
| Residue assumption | 5 t/ha straw incorporated shortly before planting |
| Area | 50 ha |
| Season | 95 days |
| Baseline / project nitrogen | 100 / 100 kg N/ha |
| Other project emissions | 0 tCO2e (unverified assumption) |
| GWP scenario | CH4 28; N2O 265 |
| Uncertainty / SOC adjustment | 15% / 5% |
- Baseline daily factor = 1.13 × 1 × 2.88 = 3.2544 kg CH4/ha/day.
- Project daily factor = 3.2544 × 0.55 = 1.78992 kg CH4/ha/day.
- Gross methane reduction = (3.2544 − 1.78992) × 50 × 95 × 28 / 1,000 = 194.775840 tCO2e.
- N2O = 100 × 50 × 0.00314 × 265 / 1,000 = 4.160500 tCO2e.
- Balance = 194.775840 − 4.160500 = 190.615340 tCO2e.
- Uncertainty = 190.615340 × 15% = 28.592301 tCO2e.
- Pre-SOC estimate = 162.023039 tCO2e.
- SOC adjustment = 162.023039 × 5% = 8.101152 tCO2e.
- Final scenario = 153.921887 tCO2e, or 3.078438 tCO2e/ha/season.
- Two identical seasons = 307.843774 tCO2e for 50 ha. At an assumed USD 10/t, gross value is USD 3,078.44, before any costs, allocation or eligibility review.
For 300 ha over two identical seasons, the corresponding illustration is 1,847.06 tCO2e. Neither number is a measured outcome, saleable inventory or promised payment. No association with a TCAF purchase price is implied.
Implementation choices
The engine retains all estimated N2O. When project nitrogen exceeds baseline, the factor is 0.00786 applied to the full project N rate; otherwise it is 0.00314 under changed water management. It makes no automatic de-minimis claim. User-entered other emissions are also deducted in full. Negative balances remain negative and have zero gross value.
The default SOC adjustment represents unproven safeguards. A zero adjustment is a scenario assumption requiring appropriate evidence and external review. Selecting it does not make the project compliant. The 5% adjustment is applied after the uncertainty deduction in this demonstration; the final monitoring treatment must be agreed with the project reviewer.
Changing the organic amendment to “none” makes the estimate much smaller. The 2.88 factor must never be silently presented as a universal property of double-cropped rice. Baseline and project residues and pre-season conditions are held equal in this prototype; changed-residue pathways need a fuller model.
The default-factor approach cannot simply be scaled into an arbitrarily large certified project. The software warns when the annual scenario exceeds 60,000 tCO2e. It does not split projects to evade scale rules. At scale, the project structure and suitable measured/country-specific approach require professional review.
Evidence and limitations
The 12-week sample is entirely synthetic. Nine observations are aligned; week 6 is missing, week 7 conflicts, and week 10 is below the demonstration confidence threshold. Those records are held for human review. An aligned record is not certified evidence. No methane value is automatically assigned to a drainage-event count.
The current application has no real Sentinel-1 ingestion, classifier training, field sensor feed, Zalo integration, persistent farmer database or independent verifier approval. Report exports include the version, timestamp, inputs, intermediate values, source links and synthetic change history. Automated arithmetic tests validate implementation behavior, not field accuracy.
Primary references
- Gold Standard rice methodology, v1.0: equations 6–13, Tables 4–9 and simplified approach conditions. This is a bounded prototype inspired by those equations, not a full implementation of all certification requirements.
- SOC rule update, published 7 July 2025: relevant to monitoring periods beginning in 2026; practice/yield reporting and conditional 5% adjustment.
- Gold Standard Rice Sustainability Hub: complete requirements, templates, tools and assurance resources.
Additionality, baseline selection, project boundaries, monitoring completeness, GWP applicability, soil safeguards, data rights and programme-specific requirements remain separate checks. National MRV, TCAF and voluntary crediting must not be treated as interchangeable.