I seem to recall Al Gore saying ethanol was something he regretted promoting.
That is a good example of taking more diesel energy to grow the corn with farm equipment than the gas that you would save by burning ethanol in your car. Besides Al Gore, there are many others that thought corn ethanol was the fuel of the future (especially farmers in Iowa).
Another fuel that has a higher carbon footprint is the sticky Alberta tar sands or oil sands (in Alberta they don't like you using the term tar). It takes a lot of fuel to make a lot of fuel from sticky stuff.
PV is much more efficient than photosynthesis, just like silicon computing is much faster than carbon based brain cells. We can make much better use of a field by installing a PV system and charging our Tesla Roadsters than growing bioengineered super corn with farm equipment and making moonshine for our cars.
I live in California and fly a small airplane. I could put car gas in the plane if it did not have ethanol in it in California. Ethanol is tough on aviation engines. Hopefully I will be able to fly with electricity or biodiesel someday.
10 years ago, I suggested to my dad that he use biodiesel for his Dodge Cummings pickup truck. He proceeded to buy a workhorse (like a clydesdale) to grow rapeseed oil to make biodiesel with. Very good intentions and I imagine he would have to work the fields for a year to drive to the Bay Area.