Let's start with the most obvious point - lack of arable land to use for ethanol production. If we were to use EVERY acre of tillable land in America for growing ethanol sources, it still would not produce enough ethanol to keep our cars going. And even if it could, we would be able to drive to the supermarket, but the shelves would be empty because there is no land being farmed for FOOD. It is just plain stupid to burn your food supply. Because of ethanol production, the cost of food worldwide has risen sharply - and the poor, already hungry, are now starving.
But it gets even worse. For every gallon of ethanol produced, it takes 1.3 gallons of fossil fuels to produce it. So, it is not even green. It actually INCREASES the CO2 levels.
It takes fuel to till the soil. Fuel to fertilize. Fuel to irrigate. Fuel to harvest. Fuel to transport to the processing plant. Fuel to process into ethanol. Isn't it strange that somehow the "greenies" overlook such things. Instead, all they can see is the end product - "WOW! Fuel from weeds!"
And what about those "electric" cars? Again, it's "WOW! Run cars without burning fossil fuels!" The problem lies in the simple fact that it takes fuel to create the electricity! Simple physics teaches us that there is ALWAYS some loss when you change from one energy to another. So, it takes more fuel to create the electricity than it would have taken to simply fuel the car in the first place.
Sure, perhaps the electricity comes from nuclear, or water. But currently, most of our electricity comes from oil, gas and coal. And we already suffer "brownouts" - a lack of sufficient electricity. Imagine if all vehicles used electricity - we would be living in the dark.
The folks who want "green" solutions are correct in believing our future depends on green solutions. But they are absolutely looking in the wrong direction. They are not thinking things through. They are going forth while wearing blinders. And ignorance is even worse than burning oil.