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Changing rice farming methods could cut greenhouse emissions, report finds

As delegates to a climate conference in the Thai capital debate how to reduce greenhouse gases, one of the problems -- and a possible solution -- lies in the rice fields that cover much of Thailand, the rest of Asia and beyond.

The report from the Intergovernmental Panel on Climate Change (IPCC) meeting in Bangkok this week concludes that rice production was a main cause of rising methane emissions in the 20th century. It calls for better controls.

"There is no other crop that is emitting such a large amount of greenhouse gases," climate change specialist Reiner Wassmann of the International Rice Research Institute in the Philippines 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," he said.

The bacteria that thrive in flooded paddies produce methane by decomposing manure used as fertilizer and other organic matter in the oxygen-free environment.

A molecule of methane is 21 times more potent than a molecule of carbon dioxide as a heat-trapping gas. Although carbon dioxide is still the bigger problem, rising levels of methane now account for 23 percent, reports the US Environmental Protection Agency.

A 2005 study by US scientists focused on China, which produces a third of the world's rice and where rice fields have shrunk by 10 million hectares in the past decade as farmers shifted to other crops. The study also found that nitrogen-based fertilizer has replaced manure, and many Chinese farmers are using less water.

Wassmann said few countries have followed China's example, instead ignoring solutions such as draining fields or shifting to locations that need less water.

Also see story:
Progress slow at UN meeting on global warming

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