There are so many other products that come out of corn being used for ethanol production, that ethanol is going to be made, mandate or not. If it doesn't sell here, it is going to ship outside the U.S. And it is the cheapest form of oxygenate that is available right now. At least that is environmentally approved. So it is not going away anytime soon. Clean air mandates, by default, will keep ethanol in the mix for some time.
Biodiesel, the same way. There is no mandate on biodiesel, except at some state levels, yet it is still made and a large portion of it goes outside the country, mostly to Europe. But while there is no mandate, there has been a trend to having biodiesel blends at the pumps across the country for some time. I go thru over 20,000 gallons of diesel a year in my business, trucking, and I haven't fuel with diesel without biodiesel blended in for over 7 years. Not that I chose biodiesel, it is blended into every gallon of diesel at every fuel stop location I frequent. And with the very substantial discounts I get fueling at those locations, I am not going to go running around the countryside looking for bio free diesel and pay thru the nose for it.
And one of the little known facts is, when corn is used for ethanol production, corn oil is removed, along with other stuff before the ethanol process begins. That corn oil is use for a variety of purposes. You see corn oil in the cooking section of the grocery store. But a major portion of corn oil goes to.... biodiesel plants! So corn is actually producing two different fuels from the same bushel of corn. One of those little snippets that the anti-ethanol crowd fails to consider in its argument that ethanol production is not energy efficient.