Improved Rice Production

Project Drawdown defines improved rice production as: a set of practices to reduce methane emissions from paddy rice production using alternate wet and dry periods and other strategies. This solution replaces conventional paddy rice production in mechanized (non-smallholder) regions.

Paddy rice farming is a major source of greenhouse gas emissions largely in the form of methane, as flooded rice paddies provide a suitable anaerobic environment for methanogenesis. Yet, rice is a world staple crop of extreme importance, particularly in Asia. Thus, low-methane rice production techniques are sorely needed. Drawdown investigated two categories of low-methane rice production: improved rice production (profiled here), with techniques suitable to both small- and large-scale operations, and System of Rice Intensification, currently limited to the smallholder context.

Improved rice production practices include: changes to water management (alternate wetting and drying); fertility management; use of aerobic cultivars; no-tillage; and direct seeding. Data was collected only from studies that used two or more of these practices.

Methodology

Total Land Area[1]

Total available land is 111 million hectares, representing non-smallholder rice production.[2] Current adoption[3] of improved rice cultivation is estimated at 41 million hectares, by interpolating the global area under "Direct Seeded Rice" in the year 1997 and 2018..

Adoption Scenarios[4]

Five custom adoption scenarios were developed based on the estimation of low, medium, and high adoption rates based on the historical growth of direct seeded rice and water management available in the literature. Some of these scenarios include early peak adoption of the solution by 2030.

Impacts of increased adoption of improved rice production from 2020-2050 were generated based on two growth scenarios, which were assessed in comparison to a Reference Scenario where the solution’s market share was fixed at the current levels.

• Scenario 1: This scenario estimates the practice of improved rice cultivation on 94 million hectares by 2050.
• Scenario 2: Based on the most aggressive and early-peak-adoption custom scenarios, this scenario yields adoption of the solution on 111 million hectares.

Adoption of the solution not only mitigates greenhouse gas emissions, but also saves significant amounts of irrigation water used in rice cultivation. As a reflection of improved rice cultivation's many benefits, aggressive adoption of the solution is projected.

Emissions, Sequestration, and Yield Model

Methane emissions reduction from improved rice cultivation is set at 5.3 tons of carbon dioxide-equivalent per hectare per year, based on 106data points from 16 sources. Nitrous oxide emissions reduction is calculated at -1.4 tons of carbon dioxide-equivalent per hectare per year, based on 43 data points from 42 sources (some sources included meta-analysis of country of level data). Sequestration rates are set at 1.45 tons of carbon per hectare per year, based on 25 data points from 3 sources.

Yield gain compared to business-as-usual annual cropping were set at 4.5 percent, based on meta-analysis of 78 data points from 11 sources.

Financial Model

First costs of improved rice cultivation are US$0 per hectare, as the practices use existing equipment and infrastructure.2 For all agricultural solutions, it is assumed that there is no conventional first cost, as agriculture is already in place on the land. Net profit is calculated at US$640.07per hectare per year for the solution (based on meta-analysis of 16 data points from 6 sources), compared to US$449.16 per year for the conventional practice (based on 33 data points from 16 sources). While the operational cost is calculated at US$384.35 per hectare per year for the solution (based on 12 data points from 5 sources), compared to US$655.86 per year for the conventional practice (based on the 28 data points from 13 sources).

Integration[5]

Drawdown’s Agro-Ecological Zone model allocates current and projected adoption of solutions to the planet’s forest, grassland, rainfed cropland, and irrigated cropland areas. Adoption of improved rice cultivation was the second-highest priority for cropland, following System of Rice Intensification.

Results

Total adoption in the Scenario 1 is 94 million hectares in 2050, representing 84 percent of the total suitable land. Of this, 52.9 million hectares are adopted from 2020-2050. The emissions impact of this scenario is 9.44 gigatons of carbon dioxide-equivalent by 2050. Net cost is US$0. Lifetime savings in net profit is US$224.7billion and operational cost is US$462.8 billion. Yield gain results in an additional yield of 56 million metric tons between 2020 and 2050.

Total adoption in the Scenario 2 is 111 million hectares in 2050, representing 100 percent of the total suitable land. Of this, 70.3million hectares are adopted from 2020-2050. The impact of this scenario is 13.82 gigatons of carbon dioxide-equivalent by 2050. . Net cost is US$0. Lifetime saving in net profit is US$304.5 billion and operational cost is US$623.4. Yield gains result in an additional yield of 83 million metric tons of rice between 2020-2050.

Discussion

Benchmarks

The Intergovernmental Panel on Climate Change (Smith et al, 2007) estimates emissions reduction of 0.2 gigatons carbon dioxide-equivalent per year by 2030 for rice management. Griscom et al (2017)’s “Natural climate solutions” calculate 0.08-0.26 gigatons of carbon dioxide equivalent per year in 2030. Between the two Scenarios, Drawdown's two rice solutions combined provide 0.34-0.54 gigatons carbon dioxide-equivalent per year by 2030. Our results are likely higher due to the inclusion of carbon sequestration benefits. (Limitations

It would be useful to obtain more rice production financial data points for the conventional case. Additional data on current and projected adoption would be useful as well.

Conclusions

Rice is a staple crop of critical importance, particularly in Asia. Rice production is currently a major contributor of methane emissions. Fortunately, low-methane rice production systems are ready to be scaled up. Wide adoption of these practices can have a significant impact on climate change mitigation.