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Rice cultivation is one of the world's largest sources of methane, a superpollutant gas with more than 25 times the warming power of CO2 over a 100-year horizon. As buyers look for credible ways to address methane emissions from agriculture, Alternate Wetting & Drying (AWD) projects have emerged as one of the fastest-growing project types in the voluntary carbon market.
But what exactly is AWD, and how can buyers know if a project's claimed reductions are real?
What is Alternate Wetting & Drying?
AWD is a water management practice for irrigated rice. Instead of keeping paddies continuously flooded throughout the growing season, farmers periodically drain and dry the fields before re-flooding them.
Continuous flooding creates anaerobic (oxygen-free) soil conditions in which bacteria break down organic matter and release methane. By introducing dry-down periods, AWD reintroduces oxygen into the soil, suppressing methane formation while maintaining rice yields. Carbon credits are generated from the difference between the methane emitted under a continuously flooded baseline and the methane emitted under the project's intermittently flooded regime.
It's a relatively low-cost, scalable intervention — but one that introduces its own accounting complexities, since drying the soil can increase other emissions, such as nitrous oxide (N2O), even as methane falls.
See our AWD explainer article here.
Read the Mitti Labs AWD case study here
Introducing Sylvera's AWD Ratings Framework
To help the market assess AWD project quality with confidence, Sylvera has developed a new AWD Ratings Framework. The framework evaluates projects across four pillars - Carbon Accounting, Additionality, Permanence, and Safeguarding & Co-Benefits - to determine how projects deliver genuine climate impact.
Carbon Accounting
Carbon Accounting assesses the over-crediting risk of a project - whether its methane reductions are accurately monitored in the field and conservatively quantified on paper. It combines two equally weighted components: Project Reporting and Carbon Modeling.
Project Reporting looks at how reliably a project measures what's actually happening in the paddies: the method and frequency used to monitor CH4 and N2O flux, how water levels are tracked (direct measurement methods like digital sensors and graduated tubes score higher than self-reported or unverified checks), and whether a documented management plan, farmer training programme, and compliance monitoring are in place to ensure the water regime is implemented as designed.
Carbon Modeling examines the accounting choices used to translate monitored activity into claimed tCO2e. This includes the credibility of the baseline flooding assumptions (with a hard eligibility check against forest clearance, recency of baseline practices, and consistent rice cultivars), whether accounting boundaries are comprehensive enough to capture material emission sources - notably N2O and soil organic carbon losses, which AWD can increase - and whether emission factors, global warming potential values, leakage, and uncertainty deductions are conservative.
Additionality
Additionality assesses whether a project's emission reductions would likely have happened anyway, absent carbon finance. It's scored across three tests - Common Practice, Financial Additionality, and Policy & Regulation - with the overall score set by the weakest of the three.
Common Practice checks whether continuous flooding is genuinely the credible baseline in the region, and whether AWD is already widespread - adoption rates at or above 20% signal that further uptake would likely be spontaneous rather than carbon-driven.
Financial Additionality looks at whether the project proponent depends on carbon revenue to cover material implementation costs not otherwise met by grants or secondary revenue, and whether farmers have a financial incentive - through water or electricity pricing - to adopt AWD on their own.
Policy & Regulation screens for laws or programmes that already mandate or incentivise AWD or water-saving irrigation, modified by how effectively that policy environment is actually enforced.
Permanence
Unlike sequestration-based project types, where stored carbon can later be released back into the atmosphere through fire, disease, or land-use change, AWD credits are generated through avoided emissions. Once methane is prevented from being released, there is no stock of carbon left that could later be reversed.
Because of this, every AWD project receives a fixed Permanence score reflecting very low reversal risk. Permanence simply isn't a differentiating risk factor for this project type - the meaningful quality questions sit in Carbon Accounting and Additionality instead.
Safeguarding & Co-Benefits
Safeguarding & Co-Benefits gives a blended view of a project's impact on communities and biodiversity beyond its carbon claims, combining a Community score and a Biodiversity score. Each of these, in turn, combines a safeguarding assessment with an assessment of positive contributions aligned to the UN Sustainable Development Goals.
On the Community side, Sylvera screens for eight safeguarding themes - including engagement and transparency, grievance redress, human rights and land tenure, benefit-sharing, labour conditions, and gender equality - several of which default to "very low risk" for AWD specifically, since the activity isn't land-based and doesn't displace existing livelihoods.
On the Biodiversity side, the focus is on the two most material risks for rice systems: water-management effects on paddy and wetland habitats, and pollution from agro-chemical inputs.
See the AWD Framework now
See the full Sylvera AWD Ratings Framework here.
AWD Ratings on to the Sylvera Platform
The first AWD project rating is now live in the Sylvera project catalog - available in our free access version, get started here.
