The “blend wall” issue is this: the EPA has mandated increasing percentages of cellulosic ethanol (as opposed to corn-derived) in gasoline. Congress (not the EPA) has specifically limited ethanol in gasoline to 10% unless the vehicle is designed for higher ethanol content fuel. There is already excess capacity in corn-based ethanol to provide ethanol at 10% for all the gasolin ein the US; therefore there is no incetive to start up celllulosic ethanol plants, therefore nobody is doing so and therefore the EPA blend deadlines will not be met.
And an interesting note from a Washingdon drone not working for EPA:
FWIW, I think that the EPA is insane. I have met many underlings in it and they are wild-eyed ideologues.