CIESIN Thematic Guides

Reducing Methane Emissions from Rice Cultivation

A major source of methane emissions is the decomposition of fertilizers and crop residues in flooded rice cultivation. The most effective option to reduce these emissions would be to prevent submergence of rice fields and to cultivate upland rice or other upland crops. Two major problems exist, however, with this alternative. First, wetland rice is normally grown under flooded conditions. Moreover, drainage of rice fields is often impossible during rainy seasons. Therefore, mitigation options need to result in reduced methane emissions and increased sustainable production of rice.

In Chapter 7 of Policy Options for Stabilizing Global Climate, the U.S. Environmental Protection Agency surveys a broad range of existing and emerging technologies to reduce methane emissions from rice production (Lashof and Tirpak 1990).

Neue (1993) explores mitigation strategies in "Methane Emission from Rice Fields: Wetland Rice Fields May Make a Major Contribution to Global Warming." The author discusses several options, including breeding rice varieties with low methane emission potential; increasing water percolation, which would add oxygen-rich water to the reduced soil layer and decrease anaerobic fermentation of soil organic matter; and diversifying crops in rice-based cropping systems.

Sass et al. (1992) report on an experiment to determine the effect of floodwater management on methane emissions in "Methane Emission from Rice Fields: The Effect of Floodwater Management." The authors found that multiple-aeration water treatment reduces methane to a significant extent when compared to the normal uninterrupted flood. Figure 6 compares rice plant height in four flood treatments.

According to Climate Change: The IPCC Response Strategies, a long-term research effort to improve irrigation techniques, increase efficiency of fertilizer use, and develop new high-yielding rice varieties may enable global methane emissions reductions on the order of 10 to 30 percent (Intergovernmental Panel on Climate Change 1991). Chapter 8 of the U.S. Office of Technology Assessment report Changing by Degrees examines two options for reduction of methane emissions, including nitrogen fertilizer use and land use changes. Parry and Swaminathan (1992) also discuss changes in land use as a method for reducing methane emissions in "Effects of Climate Change on Food Production."