@pastanaga - Actually they are currently trialing sorghum as a potential bio-fuel, particularly sweet sorghum.
Sweet sorghum is still used to make syrup in parts of the United States, since sorghum syrup is considered a traditional food, used in the same way that maple syrup is.
But, sorghum syrup is really labor intensive to make and when corn syrup is so much easier and cheaper to produce there's not much point in growing it.
But sweet sorghum is already being used in other places to make bio-fuel because it can be grown in climates where nothing else will grow well, and one of the major problems with bio-fuel is that growing it takes over areas already needed for food production.
So, growing sorghum for that purpose makes perfect sense.