Are we "Back" to Ethanol?

[Crazy Dazz]

40 years ago (and previous) Ethanol was touted as the answer to the Oil Crisis. Infinitely renewable and cleaner than petrol.

This was even before everyone got their knickers in a twist about Carbon emissions.

For while, diesels, especially modern diesels, were all the rage. Much better fuel economy, and lower Carbon emissions. Combined with the promise of Bio-Diesel.

But it seems we have finally wised up, that CO2 is nowhere near as bad as NOx and the other crap spewed out by diesels.

The problem with diesels, as best as I can figure it, is that the combustion process is inherently poor, that the continuously variable ratio makes it both hard to run clean and combines poorly with Catalytic Convertors, and that the high initial compression lends itself to more NOx production.

We also figured out that there weren't enough fish & chips shops for an effective bio-diesel industry and that relying on palm-oil created its own set of problems.

Ethanol has significantly less calorific value than petrol, but this can be offset by higher compression and cleaner burning.
Of particular interest is Butanol which can be produced from biomass unsuited to fermentation, and has a much higher energy content.

Obviously any bio-fuel requires significant amounts of agricultural product, but my basic understanding is that (unlike palm-oil) it can be produced what what would otherwise be wasted byproducts.

As I understand it, cars designed to run on E85, have components more resistant to corrosion and solvent attack?

What I'm not clear on, is the need for the 15% PULP, as opposed to 100% Ethanol??