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The debate over food crops grown for biofuels may not be quieting yet—not only is the practice said to feed fewer people than food crops grown for... food, but it also threatens wildlife habitats—but at least the variety of crops used is expanding beyond corn.

Sugarcane is seen as the most successful alternative fuel so far. It is the crop fueling Brazil's ethanol industry, which is the second largest in the world (at 24.5 billion liters last year) and considered to be the world's first sustainable biofuels economy. It is much more efficiently converted to fuel than corn, in part because a byproduct of sugarcane known as bagasse can be used to heat the distillation process.

Since ethanol fuel is not as efficient as biodiesel, efforts are underway to convert more of Brazil's sugarcane into diesel rather than ethanol. A smart move, since the biodiesel market is exploding: biodiesel production is now about 10.9 billion liters a year—ten times what it was eight years ago.

Critics of sugarcane for ethanol argue that it is causing deforestation, and the industry relies on poorly-treated workers—including child laborers and forms of slavery in the worst-case (but not infrequent) scenarios. Proponents, however, argue that labor laws exist and that the crop occupies only 2 percent of Brazil's arable land.