How much methane does alternate wetting and drying cut in rice, and how do I show it to a buyer?

Under IPCC 2019 Refinement defaults, fields drained several times in a season emit 55% of the methane of continuously flooded fields, a 45% cut. A single drainage gives a 29% cut. Multiply your baseline methane per hectare by that cut and by verified AWD hectares, subtract any nitrous oxide increase, and back it with field water records.

The scaling factors

Table 5.12 of the IPCC 2019 Refinement, Volume 4, Chapter 5, scales the continuously flooded methane rate by 1.00 for continuous flooding, 0.71 for a single drainage period and 0.55 for multiple drainage periods. Alternate wetting and drying, done properly, is the multiple drainage case. A field that is drained once at mid-season is the single drainage case, not AWD.

The formula

1. Baseline methane per hectare = daily rate under continuous flooding x days of cultivation, using a regional IPCC default or measured data.
2. AWD methane = baseline x 0.55.
3. Reduction per hectare = baseline x 0.45, converted with a named GWP.
4. Subtract the extra nitrous oxide: drained soils emit more N2O, and the 2019 Refinement (Volume 4, Chapter 11) uses a direct N2O factor of 0.005 kg N2O-N per kg N for rice with single or multiple drainage against 0.003 for continuous flooding.
5. Multiply by hectares where AWD was actually practised, not hectares enrolled.

Evidence a buyer can rely on

• Field water tube readings with dates, showing water falling below the soil surface and re-flooding, for a sample of plots each season.
• Drainage and irrigation logs by plot, and photos with location and date.
• Farmer lists with plot areas and crop calendars.
• Who checked the records, and how many plots were visited.

How the buyer can use it

A buyer can count the lower methane in its Scope 3 Category 1 for the rice it bought from those fields, if the reduction is traced to its supply. If the same reduction is sold as a carbon credit to someone else, the buyer should not also claim it, so agree in writing who claims what.

Illustrative example: 500 hectares under AWD

• Baseline: 0.85 kg CH4 per ha per day (IPCC 2019 Refinement default for South Asia, continuously flooded, no organic amendments) x 120 days (assumed season) = 102 kg CH4 per ha
• AWD: 102 x 0.55 = 56.1 kg CH4 per ha; reduction 45.9 kg CH4 per ha
• In CO2e at AR5 GWP 28: 45.9 x 28 = 1,285.2 kg CO2e per ha
• Extra N2O: 120 kg N (assumed) x (0.005 minus 0.003) = 0.24 kg N2O-N x 44/28 = 0.377 kg N2O x 265 = 99.9 kg CO2e per ha
• Net: 1,285.2 minus 99.9 = 1,185.3 kg CO2e per ha; x 500 ha = 592,650 kg, about 593 t CO2e
• Per tonne of paddy at an assumed 4.0 t per ha: 1,185.3 / 4.0 = 296 kg CO2e less

Season length, nitrogen rate and yield are assumptions; measured baselines or organic amendments change the result. AR5 GWPs are used throughout.

What Senseible does here

Senseible reads the mill's own electricity bills and fuel invoices into a fingerprinted Scope 1 and 2 record, the processing part of the rice footprint. Field water records for AWD are kept by the farmer programme.

• Rice procurement Scope 3 emissions
• Sustainable Rice Platform GHG requirements
• Regenerative agriculture Scope 3 claims

Sources: 2019 Refinement to the 2006 IPCC Guidelines, Volume 4: Chapter 5, Tables 5.11 and 5.12 (rice methane); Chapter 11, Table 11.1 (direct N2O), GHG Protocol Corporate Value Chain (Scope 3) Standard

Last reviewed 2026-10-19. Buyer programmes may set their own evidence rules for AWD claims; check the buyer's current requirements.