Sure fair enough. It’s more nuanced than someone will be able to write in a succinct HN comment. Without debating the merits of carbon intensity, the ethanol mandate is far too small to make any appreciable impact on emissions. But it is large enough to have a very appreciable impact on food costs.
Spoiler: most agriculture goes to supporting industrial livestock farming.
It doesn’t change the economics. The ethanol mandate is horribly stupid.