SSS 2008-07-30（在线收听）

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This is Scientific American's 60-Second Science, I‘m Karen Hopkin. This will just take a minute.

Biofuels sound like such a good idea. A clean-burning fuel that reduces our need for foreign oil. What’s not to like? Well, for one thing, turning corn into biodiesel could be taking food off hungry people’s plates. “Okay,” biofuel advocates say, “suppose we just use the stems and leaves that are left over after crops are harvested? That should solve the problem.” Well, maybe not entirely. Because removing that so-called crop residue takes food away from soil microbes. They convert that material into the nutrients that crops need. So says USDA scientist Ann Kennedy of Washington State University. Microbes break down crop residue to form organic matter—the stuff that gives soil its rich, dark color. Organic matter, in turn, provides nutrients, helps the soil retain water, and prevents erosion. So, if you harvest the crop residue to produce biofuels, you remove the materials that are fodder for the bugs that make organic matter. Soil quality would drop, and farmers would have to find some other way to fertilize their fields. So biofuels are not a magic bullet. Maybe you should just eat the corn and ride your bike.

Thanks for the minute, for Scientific American s 60-Second Science, I m Karen Hopkin.