Asian Rice a Source of Greenhouse Gas


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Rice isn't just a staple food for much of the world or even our planet's most consumed cereal grain—it's also inexorably enmeshed in many a cultural identity. A report, however, from the Intergovernmental Panel on Climate Change (IPCC) meeting last week in Bangkok further concluded that rice was one of the main culprits behind rising methane emissions in the 20th century.

Flooded rice paddies emit methane, a greenhouse gas that contributes to global-warming damage on a scale that eclipses coal-fired power plants, vehicular exhaust, and other sources of carbon dioxide. (A molecule of methane has 21 times the heat-trapping potency of a molecule of carbon dioxide.) Although carbon dioxide remains the Big Bad of climate change, comprising 70 percent of warming potential in the atmosphere, rising levels of methane now make up 23 percent, according to the U.S. Environmental Protection Agency (EPA).

"There is no other crop that is emitting such a large amount of greenhouse gases," said Reiner Wassmann, a climate-change specialist at the International Rice Research Institute in the Philippines, quoted by CNN."Methane emissions are unique to rice," he said. "If Asian countries are exploring possibilities to reduce greenhouse gas, they have to look at rice production. I'm not saying it's the biggest source, but in Asia it's a source that cannot be neglected."

If my inconsolable rice-chomping self had to blame someone—or something—I'd point an accusatory finger at the anaerobic bacteria that camp out in the flooded paddies. Those ravenous microbes decompose the manure (and other organic matter) used as fertilizer in what's essentially an oxygen-free environment, resulting in methane piping through the plants or straight into the atmosphere.

On the other hand, levels of methane, which is also emitted au naturale from wetlands and from other man-made sources such as landfills and cattle farming, have leveled off in the past few years after decades of atmospheric buildup, possibly because of shifts in rice production. But here's the rub: The EPA projects that global methane emissions will climb again, as rice fields expand to meet the demands of growing populations.

A maneuver as simple as periodically draining the fields of water (or moving to locations that need less water) could help reduce methane emissions, according to scientists, but farmers often lack the funds and knowledge to break from time-honored techniques.

"In the developing world, you really have to think first and foremost about providing population with food," said Pete Smith of the University of Aberdeen in Scotland, lead author of the IPCC report's section on agriculture. "You can't start thinking about climate mitigation if you have to feed your family."

Meanwhile, earth-loving rice-eaters don't have to abandon all hope...or grain. (You might as well tell this writer to give up breathing.) Here are a couple of ways we can green up our rice bowls. :: CNN (See also :: Rice and Bamboo Power for Assam, India)

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