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Motorists may be able to run their cars on kumara fuel once United States scientists give the tubers a tune-up.
Sweet potatoes, as Americans call kumara, are being re-engineered at North Carolina State University as a source of ethanol to help the US reduce its dependence on imported oil and ease the biofuel industry's troublesome reliance on corn.
While the American table sweet potato is orange inside and becomes sweet during baking as enzymes break down starch into sugar, the industrial sweet potato on which the scientists are working typically has a purple or white skin and is white inside, with a high starch content that limits its sweet taste.
It doesn't taste much like the classic kumara, but can produce twice the starch content of corn, the leading source of ethanol. More starch means more sugars that can be fermented into biofuel.
The university's Dr Craig Yencho said the big challenge was lowering production costs. "If we could plant them the same way you plant an Irish potato, by planting cut seed pieces and mechanically planting them into the ground, we could cut planting costs in half."
The ethanol production from sweet potatoes would then become more cost effective and feasible.
"Not only would these sweet potatoes be a much more viable ethanol source than corn, but because they are industrial sweet potatoes, we wouldn't be taking away from a food source," said Dr Yencho, who is now in China helping the world's number one producer of sweet potatoes tap the crop's biofuel potential.
Dr Yencho is also working on an unconventional approach to further boost sugar and thus ethanol yield. By using bacteria from deep-sea thermal vents, he is creating an industrial sweet potato that practically processes itself into ethanol.
Dr Yencho said special genes could reduce the cost of enzymes that are used by biofuel processors to break down the starch in corn to sugars which are then converted into alcohol by fermentation.
While corn is cheaper to produce than the industrial sweet potato, some groups argue that diversion of corn crops for corn-based biofuel aggravates world hunger problems.
- Northern Advocate
