I do not believe you will find a single real study that claims 60~65%.
Ethanol contains 23.6 megajoules per liter of ethanol. The highest values claimed (but disproved) were by Pimentel and Patzek of 29%.
Do you have a link that disproves Pimentel’s findings? The only ones that I am aware of were funded by the USDA and had a disturbing air of Lysenko about them.