Top Story: May 9, 2011

Sugarcane – Best of Biofuels?

Cut_sugarcane

Is sugarcane the best of the biofuels? Carnegie and Stanford scientists seem to think so. Last month they published a story in Nature Climate Change looking at biofuel crops in central Brazil.

Brazil leads the world in the use of biofuels instead of gasoline. About a quarter of their automobile fuel consumption comes from sugarcane, which significantly reduces carbon dioxide emissions that otherwise would be emitted.

Scientists wondered how the local climate has been affected as sugarcane has quickly displaced other agriculture in the region.

Using maps and data from hundreds of satellite images, the researchers calculated the temperature, the amount of water given off, and how much light was reflected versus absorbed for each of the different types of vegetation. They found that, compared to land cultivated with other annual crops, sugarcane reduced the local air temperature by an average of 0.93 degrees Celsius (1.67°F).

But compared to the natural vegetation of central Brazil—mainly grass and shrubs—the sugarcane fields warmed the ambient air by 1.55°C (2.79°F).

Co-author David Lobell of Stanford says the bulk of the temperature difference results from evapotranspiration—the moisture released to the air through the leaves of the plants and the soil.

The researchers emphasize that the beneficial effects only apply if sugarcane is grown on areas previously occupied by crops or pastureland, and not in areas converted from natural vegetation. It is also important that other crops and pastureland do not move to natural vegetation areas, which would contribute to deforestation.

So far, most of the conventional thinking about ecosystem effects on climate considers only impacts from greenhouse gas emissions. But according to co-author Greg Asner of Carnegie, “It's becoming increasingly clear that direct climate effects on local climate from land-use decisions constitute significant impacts that need to be considered core elements of human-caused climate change.”

Image by Rufino Uribe/Wikimedia

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