California rice grower Tom Butler is on a fact-finding mission. For four years, he has been applying two new practices to his Sacramento Valley fields. He is dry seeding crops to reduce irrigation and draining the fields earlier when preparing for harvest. In doing so, Butler conserves water, but he may be helping the environment another way: by reducing greenhouse gas (GHG) emissions, such as methane and nitrous oxide.

Butler is participating in a pilot program funded by the Environmental Defense Fund. Though it’s too early to measure, he has seen promising signs from the project.

“We’ve had good results with yield and water conservation, which really was our goal,” says Butler. “We’re happy that greenhouse gases go down as a result of that, but they weren’t the initial reason why we do that.”

Greenhouse gases are only a minor concern because California rice production emits relatively little of the potentially harmful gases. According to a study by a group of researchers that includes Chris van Kessel from the University of California, Davis, increasing methane emissions by rice agriculture – a natural result of climate change – are a growing concern on the global scale. The study found that a rise in carbon dioxide (CO2) in the atmosphere has increased the intensity of GHG produced from rice cultivation by more than 31 percent. 

“Together, higher carbon dioxide concentrations and warmer temperatures predicted for 2100 will lead to a doubling of the amount of GHG emitted per kilo of rice produced,” says van Kessel. “However, it is also very likely that in 90 years from now, significant progress will have been made in reducing GHG from rice fields.”

Of the global GHG accumulation for all sectors, 0.001 percent comes from California rice fields, according to data compiled by Louis Espino, UC Cooperative Extension rice farm advisor for Colusa County. An inventory by the California Air Resources Board (ARB), meanwhile, puts agriculture at 7 percent of the total statewide GHG emissions. Of this amount from agriculture, rice cultivation accounts for just 1.8 percent. In other words, rice contributes about a tenth of 1 percent of the GHG emissions from California’s agriculture sector – nearly the same as the global contribution.

“It’s such a new issue I don’t think much has been done in that area,” says Espino. “Right now UC Davis is doing the research, doing the modeling, trying to understand what goes on in the soil.”

Espino points to high yields – with greater efficiency and higher production – per acre as the main reason why California rice GHG intensity is low. Little land is devoted to rice cultivation (540,000 acres) when compared to the large rice exporting countries across Asia. With less land in production, less opportunity is available for production of methane gas.