Perhaps the worst economic drawback of biofuels is that, according to some researchers, producing biofuel burns through too many resources to make it feasible.
In a 2005 study, researchers measured the total resource input that went into producing biodiesel from a number of popular crops. They measured the gas burned by tractors plowing the fields, the energy it took to produce and spread fertilizer, the water for irrigation and the energy it took to move it to the fields, and a seemingly endless list of other expenses -- both financial and in terms of greenhouse gas emissions -- that went into producing biofuel. At best, some biofuels studied required 27 percent more energy to produce than they contained. In the worst case, sunflower oil-based biofuel took more than 100 percent more energy to produce than it contained [source: Pimentel].
In the face of these costs, some biofuel advocates argue that new and future technologies, along with economies of scale, will reduce these ratios. Until then, however, it appears that biofuels still have significant economic drawbacks to overcome on their way to replacing petroleum-based fuels.
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