One Of The Worst Sources Of Methane Emissions May Shock You

Fossil fuels may release plenty of carbon dioxide, but they alone aren’t responsible for all of the greenhouse gases blamed for global climate change.

What causes bubbling brooks to bubble is actually methane, according to researchers at the University of Wisconsin, and the same is true for the belching of cattle. The U.S. Environmental Protection Agency says methane has a 20 percent larger impact on the environment than CO2 does.

But rice? This grain is so important to human nutrition that it is second only to corn in its volume of production. Yet it turns out to be one of the chief sources of methane emissions on the planet, according to a study published July 22 in the journal Nature.

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In fact, the study said, rice paddies are responsible for as much as 17 percent of the methane, or CH4, in the Earth’s atmosphere. And cultivation is growing to meet the increase in the world’s human population.

The methane is a natural byproduct of the decomposition of organic matter in the rice paddies. Because paddies are flooded, the report said, their “warm, waterlogged soil and exuded nutrients from rice roots provide ideal conditions for methanogenesis in paddies.” As a result, the world’s rice paddies emit between 25 million and 100 million metric tons of methane every year.

So far, there’s little that can be done to remedy the emissions of bubbling brooks and farting cows, but researchers at the Swedish University of Agriculture have, through genetic modification, developed a “high-starch low-methane-emission rice” whose roots, which decompose, are smaller and the grains are bigger, providing greater nutritional yield.

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In a commentary accompanying the article in Nature, Paul Bodelier, a microbial ecologist at the Netherlands Institute of Ecology, wrote that the genetically modified rice, or “GM rice,” provides “a tremendous opportunity for more-sustainable rice cultivation.” In other words, simultaneously more food and less pollution.

In a separate interview with MIT Technology Review, Bodelier noted that humans on average eat about 150 pounds of rice per person each year. As a result, as the world’s population grows, “[i]t is expected that rice cultivation will need to increase.” And to accomplish that without increasing methane pollution would be “quite important,” he said.

Modifying the genetic makeup of the rice was fairly simple. Chuanxin Sun of the Swedish university and senior author of the study added a single gene from barley to rice, then planted it in a field next to a conventional rice field in China. Then for three years his team measured the methane emissions and the nutritional yields from both conventional and GM plants.

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The results: Sun reported that the GM plants produced 43 percent more grain per plant, and also had smaller roots and thus fewer methane-emitting bacteria around them. The reduction in methane emissions was particularly effective during the summers, when they were down to 0.3 percent of total emissions from the plant’s decomposition, compared to 10 percent emissions in the conventional crop.

The reduction in methane emission was less striking in the autumn, Sun wrote, but still significant, at about half the plants total emissions.

But Sun cautioned that larger trials are needed before science can draw any concrete conclusions about the value of the genetically modified rice. In the meantime, if you’re worried about climate change, expand your focus beyond petroleum and coal to include your next dish of curried lamb on rice.

By Andy Tully of Oilprice.com

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