Sugarcane grown to power Brazil's cars and trucks has a beneficial side effect: it also cools the local air temperature, report scientists.
But researchers warn this does not mean replacing Amazon forest or other natural vegetation with sugarcane fields. The benefit comes when sugarcane is introduced into existing agriculture, replacing pasture land or crops like soybeans.
Sugarcane manages this win-win feat by its ability to reflect sunlight and to 'sweat' out cooling moisture into the air, says lead researcher Scott Loarie of the Carnegie Institution for Science.
Plants draw moisture from the soil and emit it into the air in the process of photosynthesis, says Loarie. Sugarcane is particularly efficient at making this transfer of cooling moisture.
"We showed that with sugarcane, it was these evaporative cooling effects that were much more significant than the albedo (reflectivity)," he says, speaking of research published online in Nature Climate Change.
Sugarcane is used in biofuel that powers about a quarter of the motor vehicles in Brazil, and in that way, it helps to keep some of the greenhouse gas carbon dioxide out of the atmosphere, which affects global climate.
Carbon payback
But, because of its efficiency at emitting cool moisture, it also can push down local temperatures by 0.93°C compared to other crops or pasture.
Planting sugarcane still does not cool down the air as much as other crops and pasture warm it when they replace natural vegetation. The researchers found this local warming effect was 1.55°C.
One advantage of sugarcane planting for biofuels in Brazil is that it shortens what is known as the carbon payback time.
This is a way of calculating how long it will take to get excess carbon dioxide out of the atmosphere after it is emitted, says Loarie.
"If we cut down a hectare of Amazon forest, how much carbon are we releasing into the atmosphere and how much time is it going to take before we take that carbon out of the atmosphere?" he says. "How long will it take us to make that back, to substitute fossil fuels with the renewable fuels we're going to grow?"
In places like the Amazon, he says, the carbon payback times can stretch to 60 years. But in much of Brazil, because sugarcane is such a productive form of energy, the carbon payback times are "only a couple of years," he says.
There are caveats to using sugarcane as fuel, even in Brazil. Growing sugarcane does not address questions of waning biodiversity or possible water scarcity, and would not necessarily be able to stretch across the country's central cerrado, or savanna, without irrigation.
The researchers stressed that sugarcane's benefits are contingent on planting it on land that is already being used for farming, not in places converted from natural vegetation
Nice to know, but I am not sure how much this would contribute in the greater scheme of things. It also runs into the problem of biofuels taking up space used for food. What we need is to genetically engineer sugar cane to grow in salty coastal areas FOR THE WIN.
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Water scarcity is a big issue in much of the world, for this. Sugar cultivation has always been quite limited in scope, and intensively farmed where it can be grown at all; this is a major reason for the massive slave plantations that grew sugar during the colonial era.
On the other hand, where there are adequate water resources, it's not an inherently bad crop (though how it is raised certainly can cause problems).
So... what they're saying is that growing sugarcane for fuel has more benefits than growing, say, corn (Z. mays) for fuel?
Wondering if cellulosic biofuel would be even better.
In a perfect world we'd have half the current world population (though I can't see a pleasant or acceptable way to achieve that), better fuel efficiency, and more equitable distribution. Also, less reliance on just one energy source (petroleum) with more diversity in energy resources. Just the latter would be an improvement.
As usual, though, no one listens to me, and no one will put me in charge....
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Simply because of the amount of sugar in sugarcane compared to maize, it's got to be better for producing ethanol. At the very least, it saves the need to break down starches metabolically. On the other hand, you can grow maize in a lot drier conditions than you can sugar cane.
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Commander of the MFS Darwinian Selection Method (sexual)