Sugar cane ethanol still has incredible energy losses. Processing it into ethanol is an energy loss. Transporting it is a huge energy loss. And burning it is the worst. ICE engines are at best 28% efficient. That's a 70% loss.
You're too focused on 'efficiency' here. The two processes are so wildly different that a 70% loss at certain stages isn't a big deal.
A solar panel loses more than 70% of the power that hits it. But that doesn't disqualify it at all.
And plants lose a ridiculous percent of energy right at the photosynthesis stage, but they'd still beat solar panels if solar panel prices went back a few decades.
> Photosynthesis is way, way less efficient than solar panels, even oned a few decades back.
It is. But solar panels used to be so expensive that photosynthesis was much cheaper, despite the differences.
> I'm focused on efficiency because that's one very important metric when we are talking about how to power the world.
But a factor of 3 is not very much when you look at the entire process. The costs can very so wildly, and the existing steps lose so much energy, that the particular number you're pointing to isn't a big deal.
> Ethanol is a scam.
Depends on how you make it, where you intend to use it, and how much you're willing to tax carbon emissions. If fossil fuels are $2 a liter, my best estimate is that cars will switch to batteries but airplanes will buy biofuel.
