一些批评人士指出，玉米乙醇的生产所消耗的化石燃料能源比它最终生产的生物燃料能源还要多。

Some critics have suggested that the production of corn ethanol uses up more fossil fuel energy than the biofuel energy it eventually produces.

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And much easier to purify and know what you have at the end, than if you're trying to harvest it from a whole complex organism.

最终产品的纯化和鉴定也比,从复杂的生物体上提取和鉴定容易

耶鲁公开课 - 生物医学工程探索课程节选